Biology Module 7 Infectious Disease PDF

Module 7 - Infectious Disease 7.1 Causes of Infectious Disease Inquiry question- How are diseases transmitted? Students: describe a variety of infectious diseases caused by pathogens, including microorganisms, macroorganisms and non-cellular pathogens, and collect primary and seco...

Module 7 - Infectious Disease 7.1 Causes of Infectious Disease Inquiry question- How are diseases transmitted? Students: describe a variety of infectious diseases caused by pathogens, including microorganisms, macroorganisms and non-cellular pathogens, and collect primary and secondary-sourced data and information relating to disease transmission, including: (ACSBL097, ACSBL098, ACSBL116, ACSBL117) - classifying different pathogens that cause disease in plants and animals (ACSBL117) - investigating the transmission of a disease during an epidemic - design and conduct a practical investigation relating to the microbial testing of water or food samples - investigate modes of transmission of infectious diseases, including direct contact, indirect contact and vector transmission investigate the work of Robert Koch and Louis Pasteur, to explain the causes and transmission of infectious diseases, including: - Koch’s postulates - Pasteur’s experiments on microbial contamination assess the causes and effects of diseases on agricultural production, including but not limited to: - plant diseases - animal diseases compare the adaptations of different pathogens that facilitate their entry into and transmission between hosts (ACSBL118) 7.1.1 Infection An infection is the presence of disease-causing organisms in the body of a host. - Pathogen: (An umbrella term) an infectious microorganism that causes disease. (e.g. single celled microbes, multicellular parasites, non-cellular agents) - Infectious disease: caused by the transfer of a pathogen between hosts. All infectious diseases are communicable - Non-infectious disease: do not involve the transfer of a pathogen between hosts, usually hereditary - Communicable: disease are contagious or transmissible through contact with an infected person  - Non-communicable: diseases are not contagious or transmissible through contact with other people - Contagious: how easily the disease can be transmitted (e.g. highly contagious) Pathogens Bacteria Description Single celled, prokaryotic organisms. - Have cell wall with but no cell membrane-bound organelles - Reproduce by binary fission Transmission - Direct and indirect contact - Air borne - Vector borne - Contaminated food and water Examples Lyme disease. It is transmitted through bites from ticks. Viruses (non-cellular) Description Contain nucleic acid, either DNA or RNA (but not both), and a protein coat, which encases the nucleic acid. Key: RNA polymerase is exclusively found in viruses  Transmission - Direct contact - Indirect contact - Airborne transmission - Vector borne Examples Coronavirus Fungi Description Eukaryotic organisms that can be both unicellular and multicellular. They are both microscopic and macroscopic and reproduce both sexually and asexually.  Transmission - Direct contact - Indirect contact - Airborne transmission - Foodborne transmission Examples Athlete's foot, ringworm, yeast infection Protozoa Description Single-celled eukaryotic microorganisms that reproduce asexually by binary fission and contain a nucleus. Transmission - Vector borne - Faecal-oral transmission - Environmental transmission (e.g.swimming in infected pools) - Direct contact 250 × 250 Examples Malaria caused by plasmodium protozoa Prions Description An abnormal protein that is capable of causing degenerative diseases of the nervous system. Pathogenic prions cause disease by inducing abnormal folding patterns in the normal proteins that they come in contact with - do not contain any genetic material - Prions are the smallest of all pathogens  Transmission - Inherited in pregnancy / breastfeeding - Ingested with contaminated material Examples Ingested with Macroparasites Description Endoparasites (live in the host's body). - E.g. tapeworms Ectoparasites (live outside host’s body) - E.g. mosquito, fleas, ticks Transmission - Direct contact - Indigestion - Vector borne - Environmental exposure Examples Heartworms Transmission Modes of Transmission - Reservoir: e.g. soil, water - Carriers: e.g. humans, mosquito - Active carrier: infected individual experiencing symptoms - Passive carrier: infected individual without experiencing symptoms Types of Transmission Vertical The transmission of an infectious agent from a parent to their offspring through transmission the placenta, breast milk, or genital tract during delivery. 3 main types: Transplacental Vaginal birth Breastfeeding Horizontal transmission of organisms between biotic and/or abiotic members of an transmission ecosystem that are not in a parent-progeny relationship Direct Contact Direct transmission involves physical contact between an infected organism and a susceptible organism. Therefore, disease spreads slower due to the need for close contact. Indirect Contact Indirect transmission spreads pathogens through no direct physical contact. This causes high rates of infection as no physical contact between organisms is required. - Air borne Vector - (vector needs host to survive e.g. mosquitos, fleas) transmission Chain of Infection Process for disease to spread between organisms - Infectious agent: pathogen capable of infection and causing disease - Reservoir: place where pathogen lives and reproduces - Portal of Exit: pathway for pathogen to exit reservoir and be transmitted - Portal of entry: pathway for pathogens to enter and infect a new host - Susceptible host: depends on genetics, immunity and overall health Infection 1. Portal of Entry for Invasion (pathway for pathogens to enter and infect new host) Invade either through skin, lungs, gastrointestinal system, genitourinary tract Pathogens either infiltrate cells or travel through the blood and tissue fluids Pathogens are aided by invasins ○ Spreading factors: enzymes that impact the structure of tissue matrices and the spaces between cells ○ Clotting factors: enzymes induce clotting. This disguises the pathogen and protect it from being engulfed by the host’s immune system ○ Disrupting cell membranes: Active entry: the pathogen interferes with the host cell (e.g. disrupting the membrane) Passive entry: enters naturally into the host’s cells 2. Establishment (pathogens must establish themselves in the host’s body by adhering to a surface) Pathogens stick to cell surface using adherence factors  ○ Pili and fimbriae:help the pathogen stick by attaching to glycolipids on the surface of the host cells ○ Capsule: helps pathogen stick through hydrophobic or hydrophilic interactions with the surface of the host cells ○ Cell surface adhesion molecules: have structures that bind specifically to proteins found on host tissue 3. Evasion (hiding from the immune system) Forming biofilms: clumps of cells that produce a protective extracellular matrix to shelter themselves from the immune system Changing surface antigens: cover themselves in antigens identical to the host to make immune system believe that pathogen is not foreign Attack immune cells: destroying antibodies Hide: travelling to parts of the body that the immune system cannot reach (e.g. intestines) 4.Reproduction (Once safely established, pathogen survive and reproduce) Reproduction causes worsening of symptoms on host 5. Exit  No unique pathogen escape mechanism, it's just random. (e,g, through faeces) 6. Transmission (once out of the host, pathogen spreads to other hosts) Epidemic VS Pandemic VS Endemic - Endemic: is not serious enough to be a global concern, like flu and fever Epidemic An epidemic is an increase in the number of people affected by a disease in a certain geographical area which spans over several communities. If this area is small, it causes an outbreak If it's large enough to cover a continent, it's a pandemic Epidemic are the result of change in these factors: Human Level Pathogen Level - Migration: movement of infections - Virulence of pathogen: mutations of the individuals introduced disease to new pathogen increase its virulence, as it populations allows pathogens to evade against hosts - Poor infrastructure: populations are - Antibiotic resistance:as they become densely packed together and unhygienic antibiotic resistant, some infections practices which promote disease cannot be treated survival - Herd immunity: in populations where a - Healthcare: not accessible by the public significant number of individuals are or high cost of medication immune, the group becomes immune and reduces the chances of epidemics Controlling an Epidemic  Identifying the Pathogen Through clinical observation, laboratory confirmation Environmental The process of changing the environment to reduce contact with the Management pathogen. E.g : - Cleansing water supplies - Removing sanitary waste from public areas like sewage systems Quarantine A period of restricted movement and separation of people, animals and materials that can promote spread of infectious disease. - Example Infectious Disease Malaria Pathogen: plasmodium protozoa Transmission: Transmitted indirectly through vector borne transmission , where female mosquitoes carry the protozoan parasite, and as it bites the host it injects the pathogen into the host's bloodstream. T Infection: travel to liver, where they infect liver cells and reproduce in the liver through binary fission. Then they travel through the bloodstream. This causes antibodies to be produced by the adaptive immune system to limit the spread of pathogens in the liver and red blood cells. t Symptoms: fever, chills, headache, nausea , muscle pain 7.1.2 Robert Koch and Louis Pasteur Historical Understanding of Disease Cause of disease and organism decay was explained by the theory of spontaneous generation. Robert Koch developed the agar plate technique for growing microorganisms, and used it to culture the isolated anthrax bacillus Koch determined that each disease is caused by a specific microorganism The principles he used to identify the specific microorganism that was responsible for a disease came to be known as Koch’s postulates Koch’s Postulates 1. The same microorganism must be present in every diseased host. 2. The micro-organism must be isolated and cultured in the laboratory and accurately described and recorded. 3. When a sample of the pure culture is inoculated into a healthy host, this host must develop the same symptoms as the original host. 4. The microorganism must be able to be isolated from the second host and cultured and identified as the same as the original species. If it is identical, the disease causing pathogen has been identified A possible limitation: A number of microorganisms are found in the diseased host that could cause the specific disease. The scientist must identify the specific microorganisms through multiple cycles of the experiment. Louis Pasteur Pasteur studied the fermentation of beet juice and found that the process was due to the presence of living organisms microbes called yeasts. This led to microbial fermentation theory He discovered pasteurisation (heat these solutions long enough to kill the contaminating bacteria that were present after fermentation) He discovered that rotting of food was due to the activity of living organisms and conducted the swan-neck flask experiment ○ Experiments consisted of swan neck flask that was not sealed ○ This way he developed germ theory of disease and disproved spontaneous generation ○ The independent variable: type of flask used ○ The dependent variable: amount of contamination that can be measured Discovered how to make vaccines by administering weakened versions of the pathogen to susceptible individuals. This allows the body to build resistance Pasteur’s Experiment Concluded that: microorganisms do not spontaneously generate but originate from pre-existing microorganisms in the environment. This is because there was no growth of microbes in the sterile swan neck flasks. Microorganisms are airborne - microorganisms present in the air are responsible for the contamination of nutrients in broth. 1. Meat broth was boiled in the swan neck flasks that were not sealed and, as they cooled, the air was drawn in from outside. Any microorganisms present in the air did not reach the broth, as they were trapped in the narrow neck and the curve of the glass. 2. Over time, there was no bacterial or fungal growth was observed in these flasks. Bacterial growth occurred if the curve of the flask was broken off and the contents of the flask exposed to the air. Furthermore, tipping a flask to allow the solution in it to reach the curve where the micro-organisms were trapped resulted in bacterial growth occurring. This added further evidence to discredit the theory of spontaneous generation. Key: 1. Initial sterilisation: Pasteur first boiled the broth inside the swan-neck flask to sterilise it, killing any pre-existing microorganisms. 2. Exposure to Air: while preventing airborne microorganisms 3. Observation: as the flask remained upright, there was no microbial growth. However when the flask was tilted, it allowed the broth to contact the trapped particles in the neck, and microorganisms started to grow.  Independent Shape of the flash's neck. Variable Dependent Variable Microbial growth Controlled Variables Nutrient broth composition Flask material 7.1.3 Disease in Agriculture Plant and Animal Disease Introduction 2 Types of Diseases Endemic diseases: diseases constantly present within a country or region Exotic diseases: introduced Factors Affecting Development of Infectious Disease Host factors: the pathogen’s availability, its ability to transfer between hosts Environmental factors: overcrowding and lack of hygiene leading to a build-up of wastes, which provide a suitable environment for pathogen reservoirs; Pathogen factors: susceptibility to disease, access to pathogen Factors Contributing to the Risk of Infectious Disease Increase mobility of human populations: travellers, imported livestock and plants carry diseases  Changing patterns of land use: deforestation which causes insects and animals to migrate to other areas. If they migrate near agriculture it can cause a disease. Climate change: distribution and abundance of insect vectors Antimicrobial resistance: overuse of antibiotics on farms develops antimicrobial resistance due to rapid natural selection of resistant bacteria. If this happens, common bacterial infections may no longer be able to be treated with antibiotics. Cause of Agricultural Disease Artificial Selection Although artificial selection increases economically beneficial traits in crops, it lowers the genetic variation of a population, making the population more vulnerable to a disease The Irish Potato Famine In the 1800’s the country suffered a major famine when their main food crop was destroyed by fungal pathogens. Since potatoes were their main food source, this had an effect of starvation. The potatoes were grown asexually through vegetative propagation (taking cuttings), hence all potatoes were identical to one another, hence every potto was susceptible to a disease As a consequence, farmers today carefully control genetic diversity within crops and use breeding practices that promote biodiversity Intensification Intensive farming is a result of growing populations, involving housing crops at higher densities, increasing direct contact of individuals and hence increasing the risk of infectious disease transmission To prevent this farmers use antibiotics and vaccines, but in the long term this creates more of a risk as the overuse of medicine can great antibiotic resistance to pathogens To prevent this, farmers must have sufficient space for animals to inhabit, smaller amounts of pesticides and medicine Movement of Agricultural goods can carry diseases, if they are transported then they People and Goods can introduce the disease to new areas People can also carry a disease, and migration of people also introfduce disease to new countries To prevent this, restrictions apply to states and territories for movement of goods. Screening of luggages take place at airports, and pets are required to quarantine Plant Disease If soil pH, water availability and nutrient balance are not balanced, this increases plants' natural ability to inhibit pathogen invasion and growth. Plants have adapted to survive disease by dropping infected fruits or leaves. Pathogens invade the plant through openings in the plant (insect bites, natural openings). Cause Fungi: most common. Fungi enter plants through their stomata or any other opening caused by damage to the plant, such as pruning and insect bites. They damage the plant by destroying conducting tissues and absorbing nutrients from the plants. ○ Named example: chestnut blight Insects and mites: cause damage and act as vectors Bacteria Nematodes Viruses Symptoms Death Abnormal growth Destruction of tissues Discolouration Social and Economic Effects Reduced yields Loss of trading opportunities Economic loss for farmers Financial hardship for community/consumers Animal Disease Epizootic: the animal equivalent of a human epidemic Zoonosis: an infectious disease that has jumped from a non-human animal to humans. Effect of Animal Diseases Death of affected animals  Economic loss for farmer Loss of trading opportunities Human illness and disease 7.1.4 Adaptation of Pathogens Criteria to cause disease 1. Adhere to the host cells and enter the host 2. Colonise and multiply in host tissues 3. Resist or not stimulate host defence mechanisms 4. Damage the host Adaptations Adhesion and Invasion Viruses General Info After attaching, they must enter the host cell to facilitate replication Adhesion Surface proteins adhere to receptors in host cell surface Invasion Enter through endocytosis Non-enveloped viruses enter through forming a pore in the host cell membrane Bacteria General Info Bacteria are larger, so they cannot enter like viruses Adhesion Pili and fimbriae  Invasion Chemical strategies that destroy host immune defences Toxins are secreted to damage host cells Fungi Adhesion Assisted by cell wall that permit adhesion to host cells Invasion Cell wall and capsule protects fungi from host attacks Secretion of enzymes that damage host cells Macroparasites Adhesion (ticks) Mouthparts are able to be inserted into host skin to attach Invasion Secrete biological molecules that prevent blood clotting or initiating inflammatory response Transmission Airborne Able to be suspended in the air for long periods Pathogen causes sneezing and coughing, which causes ejection and transmission to new host Waterborne Able to colonise and proliferate in water Modified our surface structures for motility (e,g, flagella) Vector-borne Synchorine life cycle to host Vector is not affected by pathogen Production of surface proteins that allow attachment to vector Vertical Capable to uterine invasion (mother to Capable to transmission across the placenta child) Sexual is also the same as vertical 7.2 Responses to Pathogens Inquiry question- How does a plant or animal respond to infection? Students: investigate the response of a named Australian plant to a named pathogen through practical and/or secondary-sourced investigation, for example: - fungal pathogens - viral pathogens analyse responses to the presence of pathogens by assessing the physical and chemical changes that occur in the host animals cells and tissues (ACSBL119, ACSBL120, ACSBL121, ACSBL122) 7.2.1 Plant Response Passive Defence (First defence system) Physical barriers Thick and waxy cuticle, cell walls and stomata to inhibit pathogen entry ○ As pathogen secretes enzymes, these qualities resist damage Bark provides protection against pathogens Leaf structure, as they have thorns and hairs to repel insects Vertical hanging leaves: which do not accumulate a water, reducing the likelihood of pathogen reservoirs building up on the outside of leaves Chemical Barriers Production of enzymes: they break down pathogen derived toxins Antimicrobial defence: a chemical that kills microbes (e.g. antibiotics) Active Defence / The Immune Response (the next line of defence after passive defence) Physical Response Control of the surface of the plant by becoming impenetrable. (e.g. closing the stomata after sensing a pathogen ○ Rapid, takes minutes to hours Gum section to repair wounds in the bark ○ Delayed, takes days Chemical Response Enzymes that destroy the pathogen 7.2.2 Animal Responses to Pathogen Lines of defence Innate immunity: present at birth and is genetically determined. It stops the pathogen from spreading and establishing itself in the host. Non-specific. ○ First line: physical and chemical barriers formed by tissues ○ Second line: inflammation which is a cellular attack on the pathogen Adaptive immunity: third line of defence. Targets specific pathogens to kill them and produces memory cells. Specific. ○ Inflammation ○ Phagocytosis ○ Fever ○ Cell death to seal off the pathogens Introduction of the Immune System Antigen is the molecule that the body recognises as foreign and that triggers the immune response  ○ Host cells tissues have antigens, but they are self antigens and hence recognised as belonging to the host and hence does not trigger the immune response Therefore antigens that are foreign or non-self trigger the immune response There are ‘marker molecules’ on the surface of the body that identify the cell as belonging to the body (self) Pathogens entering the body have a variety of chemical markers (antigens) on their surface. The immune system recognises these markers as non-self Components of the Immune System Lymphatic System A part of the immune system and circulatory system. Lymphatic system transports immune cells throughout the body and is where antigen recognition by lymphocytes occurs. Its role is to provide space for lymphocyte maturity and to transport lymphocytes and antigen presenting cells to the lymph node to stimulate the adaptive immune response. It plays an integral role by transporting bacteria and viruses to the lymph nodes where they are trapped and destroyed by phagocytes and lymphocytes. Primary lymphoid tissue is where the B and T cells are produced and mature. Thus referring to bone marrow and the thymus. Secondary lymphoid tissue is where the adaptive immune system begins. This entails the spleen, tonsils and lymph nodes. Function: ○ Immune response: detects and responds to foreign invaders Composed of: ○ Lymph: A clear fluid that circulates through the lymphatic system. It contains white blood cells, especially lymphocytes, which are essential for immune responses. ○ Lymphatic vessels: Network of capillaries and larger vessels that transport lymph throughout the body. These vessels run parallel to veins and arteries and have valves to prevent backflow ○ Lymph nodes: Small, bean-shaped structures located along the lymphatic vessels. They act as filters, trapping bacteria, viruses, and other foreign substances, which are then destroyed by lymphocytes. Pathogens and their products enter the lymph fluid. As fluid transports through lymphatic nodes, if there is a pathogen the node undergoes enlargement. Changes in size, shape or texture of lymph nodes may help to pinpoint the site of an infection. (this is an response to infection) White Blood Cells Protects the body against infections and is involved in both innate and adaptive immune response.  When do they come in Microbiome The collective term for microbes that live on skin, intestines and mouth. The presence of the microbiome inhibits the growth and multiplication of many pathogens that encounter the body, because the natural microbes out-compete the pathogenic ones. However if the balance is changed, growth and multiplication of harmful pathogens cannot be controlled. Physical Barriers Physical barriers are structures that the body uses to restrict entry to pathogens, by making it difficult for the pathogen to adhere to cells or to penetrate tissues.  Skin: structure that covers the entire body and is made of tightly packed skin cells that strengthen skin against breakage and infection. Mucus membranes: they line the openings of a body that is not covered by skin (e.g.reproductive tract) and secretes mucus which traps unwanted pathogens until they are removed by cilia. The mucus also contains enzymes which break down microbes. Cilia: small hair-like structures tin the respiratory tract that sweep the mucus along the tract so that they can be coughed out Physical Response to Infection Vomiting: the body’s way of expelling harmful substances Increase urination: if there are pathogens in bladder, and in response they flush it out through urination Wound healing: reseals the damaged physical barriers against infection by pathogens. Chemical Response to Infection Urine: antimicrobial substances in urine, as well as its pH, help create conditions that are unfavourable for the growth of pathogens. ○ Sebum, sweat, saliva and tears all contain antimicrobial substances Inflammation: the accumulation of fluid, plasma proteins and white blood cells that occur when tissue is damaged or infected. It helps wounds repair and leads to pathogen destruction. It is a defence mechanism and occurs at the sight of infection. ○ When cells are challenged with pathogen, they release chemicals that alarm the body ○ These chemicals cause the capillaries to dilate, increasing the blood flow to the site of infection, causing the area to become red, hot and swollen, painful and sometimes less mobile ○ This also increase the permeability of the blood vessels, which allows certain white blood cells to move from the blood into the tissues to attack the invading pathogens Phagocytes are a type of white blood cell attracted to the sight of inflammation. Phagocytes include macrophage, neutrophils and dendritic cells ○ Chemicals that increase body’s temperature are also released, inhibiting growth and reproduction of pathogen and inactivates harmful toxins from the pathogen (denatures pathogen’s enzymes) ○ Inflammation is characterised by redness, heat, swelling, pain, loss of function Not bruising Phagocytosis Phagocytosis is the process by which phagocytes change their shape so they can surround a foreign particle and completely enclose it. Once the foreign particle is inside the cell,lysosomes containing digestive enzymes duse with the phagosome to form a phagolysosome. The enzymes released within the phagolysosome break down the pathogen inside the cells. These fragments are eventually released by the phagocytes by exocytosis after the pathogen has been destroyed. Phagocytes are specialised white blood cells, and they include: ○ Neutrophils ○ Macrophage ○ Dendritic cells Neutrophils Neutrophils are the first to move to the site of the infection to inactivate pathogens Neutrophils are short acting and then self-destruct after a few days They are used by the body to fight acute infections. ○ Therefore, an increase in circulating neutrophils in the blood indicates inflammation Formed in the bone marrow Macrophage Live longer than other phagocytes, so that help fight chronic infections Present some antigenic fragments on their surface, it then meets up with T lymphocytes and activates them Release cytokines, which attract other immune cells and promote inflammation Monocytes They circulate blood normally until attracted to inflamed tissue, and they undergo transformation into macrophages and dendritic cells Fights chronic infections  When damage occurs to tissues, monocytes are recruited to the tissue from the blood. On the surface of monocytes are toll-like receptors (TLRs), which recognise specific pathogen-associated molecular patterns (PAMPs) released from bacterial cells. Monocytes quickly differentiate into macrophages and dendritic cells. They remove microbes, lipids and dying cells through the process of phagocytosis. Natural Killer Cells Lymphocytes that constantly patrol the body, and are important in defence against virus-infected and cancerous cells. They release cytotoxic chemicals that kill cells directly, they are only released in close proximity to the target cell Not phagocytes Complement System The complement system is a group of around twenty soluble proteins that assist other defence mechanisms destroying extracellular pathogens. It is non-cellular, meaning that it does not require any cells unlike every other system. These complement proteins can stimulate phagocytes to become more active, attract phagocytes to the site of the infection or destroy the membranes of the invading pathogen. Usually inactive, but become active when pathogen is in detected in the body Complement proteins Complement proteins are attracted to pathogen-antibody complexes and bind to them as well. This acts as a signal for phagocytes and other lymphocytes called B cells (third line of defence) to destroy the pathogen. These proteins circulate the blood and is a part of the initial response to pathogen opsonization, where the proteins flag the antigen for removal Cytokines Cytokines are chemical messengers that are produced during an infection and they promote the development and differentiation of T and B lymphocytes for the third line of defence. Fever (pyrexia) Elevation in body's temperature to kill or limit the growth of pathogens. High temperature of the body also enhance the activity of white blood cells and thereby strengthen the response to the presence of the pathogen Advantage Disadvantage Increased immune activity: Higher body Discomfort and pain: Fever often comes temperatures can enhance the efficiency with symptoms such as sweating, chills, of immune cells, such as white blood headache, muscle aches, and cells, which helps in fighting off infections dehydration, which can be very more effectively. uncomfortable. Inhibit pathogen growth: high Severe Fever Risks: Very high fevers can temperature slows pathogen growth and be dangerous and lead to complications replication such as febrile seizures and it can Sense of awareness: Awareness of illness denature healthy enzymes due to signs and symptoms experienced, allowing person to seek treatment as soon as possible to minimise effects on person 7.3 Immunity Inquiry question- How does the human immune system respond to exposure to a pathogen? Students: investigate and model the innate and adaptive immune systems in the human body (ACSBL119) explain how the immune system responds after primary exposure to a pathogen, including innate and acquired immunity 7.3.1 Immune system Recognise patterns and alert other cells and tissues if these patterns are non-self Adaptive Immune Response Innate Immune System Mostly explained in the previous part. Main responses of the innate immune system; Phagocytosis Natural killer cells Inflammation Complement system Adaptive Immune System B and T Lymphocytes are mainly responsible for generating adaptive immune systems. They target different types of antigens. Antigen molecule have regions called epitopes that can bez in the immune system, and this is how they determine if they are self are non self Humoral Response Cell-mediated Response Most effect against Pathogens in body fluids Intracellular pathogens Cells involved B lymphocytes T lymphocytes Antivirals Inhibits the development of viruses inside infected cells (does not kill) Before virus replicates is the best time antivirals should be taken Limitations ○ Developing a class of drugs that stops viral replication without killing the host cells is challenging ○ Accessing medication and complying with dosing regimens may be difficult in developing countries Antibiotic Controls bacterial infection by either killing or inhibiting the growth of bacteria ○ Bacteriostatic ○ Bactericidal Most effective when it ○ Used for bacterial and not viral infections ○ Kills rather than inhibit the growth of bacteria  ○ Targets a specific pathogen ○ Taken for the whole course Antibody (immunoglobulins) Definition A blood protein produced in response to and counteracting a specific antigen. Antibodies combine chemically with substances which the body recognizes as non-self. The antibody molecule has two binding sites, where each binding site is specific for a particular antigen. This is an antigen-antibody complex. Antigens interfere with the functioning of the pathogen. Function To identify and neutralise foreign substances and a response to antigens. They bind to epitopes of pathogens in their natural form. (other cells like T cells recognise fragments of antigens only) Structure Y-shaped. Their structure allows them to specifically bind to antigens, and their diverse functions enhance the body's ability to fight infections and eliminate pathogens. Antibody Neutralisation Deactivating a pathogen or toxin by blocking its active site. i.e. by Strategies blocking the part of the antigen which is the key to its ability to (antibodies cause damage. Hence the antibody can prevent binding between recognise a toxin or pathogen and its target such that its unable to cause damage and has no effect on the body. Agglutination Antibodies bind to antigens on the surface of cells to form clumps of cells. This enhances phagocytosis as the clumps can be easily removed by phagocytes. Complement Antibodies activate complement proteins to facilitate the Activation immune response. Enhances phagocytosis, inflammation and contributes to pathogen removal.  Precipitation Antibodies bind to soluble antigens causing them to form insoluble clumps. This enhances phagocytosis as the clumps can be easily removed by phagocytes. Lymphocytes Each B and T cells are different. Since each T and B cells have specific receptors specific to an antigen, the diversity of receptors on each cell allows millions of combinations of receptor types available to the human immune system. These combinations are determined by person’s genes and programmed from birth When an antigen is present in the body, the B cell that is specific for that antigen is activated, and then cloned. Once the antigen is destroyed, these cloned B cells remain, ready for the next time this specific antigen presents itself to the body – they become memory cells and adapted, and hence the adaptive immune response is specific B Cells (B Lymphocytes) T Cells (T Lymphocytes) Types and Plasma cells Cytotoxic or Killer T Cells Function Produce antibodies against the Kill foreign, infected and abnormal cells. pathogen. This is also known as the Theory also kill the body's own cells if they humoral response. become dangerous or infected (like cancer They bind to specific antigens cells) Don't directly destroy They secrete toxic chemical into the pathogens, instead they target cell, these prevent interfere with the functions of reproduction and kill it the pathogen so that ○ Pathogen is unable to cause damage ○ It is easier for other  components of the Helper immune system to Help promote the activities of other destroy it immune responses by secreting cytokines which: Increase the activity of phagocytes Help promote inflammation Stimulate the production of cytotoxic T lymphocytes and memory B lymphocytes Basically increase everything Memory B Lymphocytes Suppressor Provides long term defence against Turn off the immune response after the antigens. Memory cells recognise an antigen has been successfully destroyed or antigen if they have been exposed to removed. it before. Faster Memory T Lymphocytes Stronger Provide the body with long term defence Longer lasting against antigens. They enable a faster and larger response to the same antigens. In secondary exposure, memory T cells activate B cells which differentiation into antibody-producing plasma cells to produce large amounts of antibodies Location Blood and tissue fluids of the body Sight of infection Target Attacks invaders outside cells Attacks invaders inside cells. They are in direct contact with the cell. Cycle 1. They are produced and 1. Produced in the bone marrow mature in the bone marrow 2. They are released into the blood 2. Once matured they are and mature in thymus gland released into the blood 3. Once they mature, they are 3. They accumulate on the released into the blood again where lymphoid tissues (this is they circulate in an inactive state where they stay until there is 4. If a T lymphocyte comes into a pathogen) contact with its specific antigen, the 4. When B cells come in contact receptors on its surface allows it to with specific antigen, it bind it and the cells become becomes activated activated 5. Once triggered, it begins to 5. Once binded, it proliferates and proliferate to form millions of differentiates into one of the 4  clones types 6. These daughter cells differentiate to become either plasma cells or memory B Cells The Link between humoral and cell mediated response Antibodies (function of the humoral response) have no direct access to pathogens, T lymphocytes (cell mediated response) target and destroy the entire infected host cell as well as pathogens inside them. MHC Molecules (major histocompatibility complex molecules) Protein molecules that carry the partly digested antigens to the cell surface, where these are recognized by T cells. It allows the T cell to recognise if a cell is self or non self. There are 2 types: MHCI - in every cell that has a nucleus in vertebrates MHC II - in antigen-presenting cells such as macrophages, dendritic cells and activated B cells Summary of Adaptive Immune Response 1. Foreign material is engulfed by macrophages, which then display the antigen attached to their MHC II molecules 2. The antigen-presenting macrophages move to lymph nodes, where they are inspected by helper T cells that have the T cell receptor that corresponds to the antigen being presented. ‘  The helped T cells can also be activated by B cells. When a b cell encounters the antigen-antibody complex, and processes the antigen, attaches it to its surface molecules and presents hos to the helper T cells that have the matching t cell receptors 3. These helper T cells then activate the cloning of millions of cytotoxic T cells and memory T cells that are specific for this antigen 4. The cytotoxic t cells leave the lymph nodes and migrate to the site of the infection, where their antigen receptors bind with the antigen displayed on the infected cell. 5. These T cells then release chemicals that destroy the cell and any pathogens within it. 6. These chemicals also increase the inflammation and attract more macrophages, which carry out phagocytosis to help destroy the pathogens and clear up debris. 7. Some of the cytotoxic t cells produce a chemical which protects the healthy cells around an infected cell from viral invasion. 8. Once the infection has been defeated, the suppressor T cells release other chemicals to stop the production and action of the cytotoxic T cells. 9. The memory T cells that are produced at the time and are specific to that particular antigen remain in the body, in the lymph nodes. On re-exposure to the same antigen containing pathogen, they cause the rapid production of more of the same cytotoxic t cells, This prevents the body from developing the symptoms of the disease again. 7.3.2 Primary and Secondary Immune Response Primary Immune Response Secondary Immune Response Effectiveness Fast but short lived. Response is by B More rapid response and higher production and T lymphocytes. of antibodies. This is because of the Since its the body’s first memory T and B cells exposure to certain antigens, Why booster vaccines are it can take a while for recommended matching T lymphocyte to found and activated How much of A higher antibody concentration remains as antibodies more memory B and T cells are formed. remain after antigens die Symptoms Usually symptoms are produced Usually no symptoms Infectious disease example - Cholera Bacteria Vibrio Cholera  Symptoms Severe dehydration and diarrhoea, and if not treated death Transmission People ingest water or food contaminated which cholera bacteria, where faces of diseased persons are a source of contamination. Innate response Production of cytokines Migration of neutrophils They kill or inactivate the bacteria Adaptive B lymphocytes specific to cholera antigens response Antibody production which peak at 1-3 weeks after initial infection B memory cells form How it affects 1. Bacteria multiply rapidly the body 2. Toxin from bacteria penetrates cells of intestinal wall 3. Toxin precents ontesitne from absorbing water from digested foo d Types of Immunity Active immunity Occurs when the immune system is stimulated by an antigen to make its own T, B cells and antibodies. Key: the body makes its own T, B cells and antibodies and active immunity is permanent as memory cells are produced 2 types: ○ Natural active immunity: you become immune after catching a disease. The pathogen introduces the antigen to your immune system ○ Artificial active immunity: produced by a vaccine Involves a controlled dose of antigenic material into the body Passive immunity When antibodies are transferred to an unimmunised person, providing them with temporary protection against a microbial agent or toxin. Key: the body becomes immune after being GIVEN antibodies and passive immunity is temporary since there are no memory cells produced 2 types: ○ Natural passive immunity: a baby come immune due to the antibodies received from their mother (e.g. through the placenta and breastfeeding) ○ Artificial passive immunity: the body becomes immune after being injected with antibodies from someone else (e.g. through purified blood products of animals an immune people) Comparison Active immunity is slower than passive immunity They both involve antibodies being produced or introduced either naturally or artificially 7.4 Prevention, Treatment and Control Inquiry question- How can the spread of infectious diseases be controlled? Students: investigate and analyse the wide range of interrelated factors involved in limiting local, regional and global spread of a named infectious disease investigate procedures that can be employed to prevent the spread of disease, including but not limited to: (ACSBL124) - hygiene practices - Quarantine - vaccination, including passive and active immunity (ACSBL100, ACSBL123) - public health campaigns - use of pesticides - genetic engineering investigate and assess the effectiveness of pharmaceuticals as treatment strategies for the control of infectious disease, for example: - antivirals - antibiotics investigate and evaluate environmental management and quarantine methods used to control an epidemic or pandemic interpret data relating to the incidence and prevalence of infectious disease in populations, for example: - mobility of individuals and the portion that are immune or immunised (ACSBL124, ACSBL125) - Malaria or Dengue Fever in South East Asia evaluate historical, culturally diverse and current strategies to predict and control the spread of disease (ACSBL125) investigate the contemporary application of Aboriginal protocols in the development of particular medicines and biological materials in Australia and how recognition and protection of Indigenous cultural and intellectual property is important, for example:  - bush medicine - smoke bush in Western Australia 7.4.1. Limiting Spread The three levels of disease monitoring Local Related to activities in neighbourhood, village, city. Sanitation, jow waste and sewage are disposed of Overcording, increase chance of host to host transmission Animal husbandry Regional Trades of goods across a country Global Human migration across the globe Spread of Named Infectious Disease Coronavirus initially started in Wuhan of China, which affected people at a local level. It spread regionally across the country due to human migration and trades of goods. As china manufacturers many goods, the transportations of these goods globally contributed to the spread of the disease globally, becoming a pandemic. Factors involved in disease transmission Not a single cause, the causes are multifactorial involving loca, regional and global factors. Pathogen factors Host factors Environmental and geographic factors (climate, humidity and temperature) 7.4.2 Disease Prevention Prevention Control - when prevention is failed Both Hygiene Any activity that reduces the availability for pathogens to survive and proliferate. Basic personal hygiene practices: cleaning yourself and your environment, washing hands before eating  Government level: cleansing water ways and correct disposal of waste Although it is useful and simple, it has a general effect rather than targeting a specific disease Vaccination Vaccines are substances that contain the antigens of specific diseases, and can be used to provide immunity against them. The vaccines mimic the disease, allowing the body to develop immunity by producing memory cells. Pathogens are inactivated or even killed before it enter the body Specific to a specific disease Purpose of vaccination is for herd immunity and makes our immune response stronger, vaster and longer lasting. vaccination programs are able to eradicate diseases (e.g. smallpox) For a vaccine to be successful, a series of vaccinations should be given over a number of years, as over a series of vaccinations, the lymphocytes will more rapidly recognize the antigen and the numbers of memory cells prodyced will be enough Exam language: vaccination is the introduction of a vaccine into the body with the intention of providing immunity to a specific disease Pesticides Pesticide is a substance that controls pests by killing pathogen responsible for a disease. Key: protects people against vector-borne diseases and crops and livestock Example: DDT was a pesticide that was used to kill mosquitoes in the past Dangers ○ Biomagnification: pesticides accumulates in the body tissues of organisms in the food chain in increasing amounts at higher trophic levels ○ Pests develop resistance Genetic Engineering Used to modify the genetic structure of an organisms using biotechnology, where this is used to produce plants and animals that are resistant to pests and diseases. Quarantine A period of isolation used to control the spread of infectious disease that physically controls a disease by limiting its opportunity for transmission. Small scale: confining patient to homes or hospitals Large scale: confining whole communities and banning or limiting transport of food supplies Animal quarantine: to ensure that they are disease free befor they are released Plant quarantine: examines all parts of the plants for pests and diseases Medication Antivirals: target virus Antibiotics: target bacteria Public Health Campaign Used to prevent and control disease 7.4.3 Antivirals and Antibiotics Antivirals They do not kill viruses, but inhibit their development inside infected cells. They do not cure the disease, they slow the the progress of damage from viruses, so the body's natural defence can take over Each antiviral is specific to a virus Best taken before the virus replicates inside a cell The antivirals must stop viral replication without killing the host cell Since virus are intracellular, it is difficult to develop drugs that target intracellular pathogens ○ This is because the antiviral is required to penetrate the cell membranes without damaging the host cell. This has an affect of disrupting the correct functioning of cells and cellular processes such as protein synthesis and cell replication They are only used for serious illnesses and not against common viruses since the immune system is usually able to defend body and to also lower the chances of developing a resistant strain of bacteria Antibiotics Specific to a specific bacteria They are often produced from chemicals that are naturally produced by organisms ○ E.g. penicillins are naturally by fungi penicillium ○ This is bc natural treatment is a biodiverse source that are rich in microorganisms that produce wide variety of antibiotics and have unique structures and modes of synthesis that may not be replicated through artificial methods Have selective toxicity, as they harm bacterial cells but not host cells Disadvantage of overuse: antibiotics induce selective pressure that causes the bacteria most suitable to survive and reproduce its characteristics, building resistance. This is a negative since scientists may never find an antibiotic suitable for the bacteria every again Comparison Antivirals do not cure a disease as it does not kill the virus, rather it suppresses and slows the process of the virus harming the body. Antibiotics cure a disease as it can kill the bacteria Antibiotics are overused and misused therefore they have resistive issues Bacteria is usually extracellular hence easier to target, virus is intracellular which means they are harder to target as they must penetrate through the cell membrane of the host’s cell without damaging it Overall, They are specific because they are designed to targets the pathogen’s unique features of their lifecycle, specific proteins, enzymes, toxins and replication processes 7.4.4 Environmental Management and Quarantine Methods Environmental Management Quarantine Methods 7.4.5 Data Data that must be collected: Incidence The incidence of an infectious disease is the number of new cases occurring during a specified time. i.e the infection rate probability of contracting the disease. Noted as a percentage Used by health management authorities: Indicates if there is a disease outbreak and its rate of spread Prevalence The prevalence of a disease is the proportion of the population that have the disease at a particular point in time. Incidence refers to new cases, prevalence refers to all cases It is used by health management authorities: Determines if long term healthcare resources are necessary Allows monitoring effectiveness of healthcare resources and campaigns, and management over time Mobility Mobility of a population assesses the potential disease outbreaks. This is because humans carry pathogens and spread diseases to new locations. Dengue Fever Vector-borne disease via aedes aegypti mosquito. It is caused by a virus called flavrius Prevalent in SouthEast Asia due to the subtropical environment which is ideal for the mosquitoes. Symptoms includes high fever headaches, muscle pains, vomiting Malaria 7.4.6. Predicting and Controlling the Spread of a Disease ​Epidemiology: the study of the incidence and distribution patterns of disease that lead to its cause, management and control. Quarantine is a historical method to prevent and manage spread of disease 7.4.7. Aboriginal protocols in the Development of Medicine Bush medicine: refers to the use of herbs and other plants to treat illnesses There is a variety of medicine, since remedies from plants vary from region to region Traditional remedies would not stayed static over time between trading groups would have passed information, seeds and knowledge from group to group The medicine is taken by being chewed or made into concentrated tree Changes in bush medicine: ○ Introduction of billycan changed the traditional aboriginal, as they started boiling as it destroy harmful pathogens, but it also destroys some of the active ingredients that are essential component of the remedy Contemporary application:  ○ Many scientists are interested in traditional healing due to the increase of infection and need for sources to create medicine. Bush medicine has antimicrobial substances. However it is important that Aboriginal protocols are acknowledge, respected and applied Key concern of Aboriginal people: ○ That they have not received any acknowledgement, financial credit for their property. ○ Damage to their native plants Intellectual property: the property of the mind or privately owned knowledge Different species: ○ Tree smoke bush: a tall and open shrub that will grow to 3 to 4 that grows on sand plains ○ Common smoke bush: multi-stemmed shrub with a lignotuber. It has slender need-like leaves and loose branching clusters of white or grey flowers. It helps with thephysical and mental clearing of the mind providing greater concentration ability especially after stress and trauma ○ Slender smoke bush ○ Plume smoke bush Cycles are important, to observe how the mosquitoes fully develop into adulthood,d and therefore how they move diseases/ therefore we learn that we can kill the larvas when they are immature to prevent spread of diseases SUMMARY Innate Immune Response Adaptive Immune Response Characteristics Non-specific: does not target Specific: Targets specific pathogens specific pathogens. It based on antigen recognition responds in the same way to Delayed: Takes days to weeks to all infections become fully activated upon first Immediate: the first line of exposure to a pathogen defence, acts within minutes Memory: Remembers previous to hours of encountering a encounters with pathogens, leading pathogen to a faster and more robust No memory: does not response upon subsequent remember previous exposures encounters with pathogens Components Physical and chemical Lymphocytes: B cells and T cells barriers Antibodies: Produced by B cells and Cellular defences: phagocytic target specific antigens cells, natural killer and dendritic cells proteins: complement  system, cytokines Inflammation Functions Barrier protection Antigen recognition: B and T cells Pathogen recognition: Uses recognize specific antigens through pattern recognition receptors their unique receptors (B cell (PRRs) to identify receptors (BCRs) and T cell pathogen-associated receptors (TCRs)). molecular patterns (PAMPs). Clonal expansion: Upon recognizing Inflammation an antigen, specific B and T cells Phagocytosis proliferate and differentiate into Activation of adaptive effector cells. immunity Memory formation: Some B and T cells become memory cells, providing long-lasting immunity. Humoral immunity: B cells produce antibodies that neutralise pathogens and facilitate their destruction. Cell-mediated immunity: T cells, including helper T cells (Th cells) and cytotoxic T cells (Tc cells), coordinate the immune response and directly kill infected cells. How innate and adaptive immune response interact The innate and adaptive immune responses are highly interconnected and interdependent. The innate immune system provides an immediate response to pathogens and acts as a bridge to activate the adaptive immune system. Through processes like antigen presentation, cytokine signaling, and cell activation, the innate immune cells help initiate and shape the adaptive immune response. Conversely, the adaptive immune system enhances the effectiveness of the innate response through mechanisms such as antibody production and the formation of memory cells, ensuring a more efficient response upon re-exposure to pathogens. Infectious Disease Non-infectious Disease contagious, meaning that they can be not contagious and are caused by genetic, transmitted from one organism to nutritional and environmental factors, not another, and are caused by pathogens. pathogens. Plants Animals Chemical Release of enzymes Immune cells and molecules responses Complement system Cytokines White blood cells: phagocytes and lymphocytes Production of antibodies Physical Bark Skin Response Thick cuticles Mucous membranes Stomatal closure Cilia Cell wall reinforcement Inflammation Vertical leaf orientation