Viruses: Types, Replication, and Diseases PDF

Filterable virus Chamberland- 1800s- took tobacco leaf infected with tobacco mosaic virus- made a paste out of it- filtered it with small enough pores to filter out bacteria- rubbed filtered paste onto uninfected leaf-caused disease on that leaf too PROVED THAT VIRUSES EXIST-agent smaller than bact...

Filterable virus Chamberland- 1800s- took tobacco leaf infected with tobacco mosaic virus- made a paste out of it- filtered it with small enough pores to filter out bacteria- rubbed filtered paste onto uninfected leaf-caused disease on that leaf too PROVED THAT VIRUSES EXIST-agent smaller than bacteria Infectious fluids were passed through filters designed to trap bacteria The cell-free filtered fluid remained infectious This proved that an agent smaller than bacteria was the cause of the disease Causes common cold-rhinovirus emerging viruses A virus that has appeared suddenly or has recently come to the attention of medical scientists. Covid, avian influenza, H5N1 Virus A bag of DNA or RNA(nucleic acid-either RNA or DNA, surrounded by a protein capsid) Nonliving infectious agent Obligate parasite that needs a host(host-specific!) Generally too small to filter out Obligate parasite unable to grow outside of a living host Antibiotics do not kill _____. Viruses Sometimes, antibiotics are given for viral infections to prevent ____________. Secondary bacterial infection Ex. Antibiotics to prevent bacterial pneumonia in a person with whooping couch(which is a virus) Viruses- Random facts to know Measles- rash, respiratory infection Mumps- lymph nodes, can cause sterility in MALES Polio- spreads via fecal contamination- water- March of Dimes women raised money for polio research in the 1930s/40s/50s Rabies-has vaccine for dogs Shingles- a herpes virus, chickenpox Wart- burn or freeze to trigger immune system to attack, liquid nitrogen, HPV=wart, can turn on cancers, especially cervical and penile Colorful tulips- A virus that humans infect tulips with Smallpox- Eliminates worldwide in the 1970s via vaccine Smallpox vaccine causes the development of a pustule full of live virus, which can be contagious when it ruptures Canker sores/cold sores- herpes 1 virus Influenza- dangerous since it causes secondary infections, mutates very fast Ex. H5N1- bird to dairy cow to human Mass termination of birds for avian influenza Ex. canine influenza- show dogs are often vaccinated Envelope virus Virus with a phospholipid envelope Ex. Flu Non-envelope (naked) virus No extra layer Ex.Herpes electron microscope 1945 Need it to see viruses First human viral disease diagnosis from an animal Sir Walter Reed-1901- Transmission of yellow fever from mosquitos to humans in South America Humans cut down trees, the monkeys that mosquitos fed on left, mosquitos fed on humans instead, infected them with yellow fever Controls for viruses Vaccination Chemical control Ex- Polio has a vaccine We add chlorine to pool water to prevent it Agent that kills viruses virucide Bacteriophage A virus that infects bacteria, complex virus Types of nucleic acids in viruses ssRNA(mRNA) ssDNA dsDNA dsRNA Example of a ssDNA virus Parvovirus Puppies-fecal material Example of a ssRNA virus influenza a ssRNA virus with two ssRNA strands HIV (unusual!)-attacks T Helper cell-no immune system now! Enveloped virus Reverse transcriptase- retrovirus Transcribes RNA to DNA HIV enters cell, capsid proteins removed in the cytoplasm, RNA released, reverse transcriptase to DNA, DNA to nucleus, transcribes to mRNA for genome and released back to cytoplasm, capsid assembled around genomes, new HIVs bud from host cell! Glycoprotein spikes On the capsid or the envolope Used by mumps virus or HIV to attach to host receptors protein encoded by NA, integrated into the viral envelope Ex. hemagglutinin neuraminidase- attach to lungs Common in making flu cavvine capsomer A subunit of the virus capsid shaped as a triangle or disc. Bacteriophage anatomy Phage head Tail Tail fibers(used to attatch/inject) lytic cycle cycle of viral infection; results in replication of virus and cell destruction LYSES CELL lysogenic cycle a viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA Viral Replication 1. ADSORPTION(attatchment of virus to host cell-glycoprotien spikes of virus bind to the receptors of the host cell) 2. PENETRATION(host cell can bring it in by vacuole/vesicle or virus can enter by itself) and UNCOATING(envolope/capsid is dissolved and the nucleic acid of the virus is released into cell cytoplasm) 3. SYNTHESIS/REPLICATION(nucleic acids translated into building blocks for new viruses, host cell machinery used) 4. MATURATION/ASSEMBLY (mature virus particles assembled from parts) 5. RELEASE (nonenveloped/complex viruses released when cell lyses, enveloped viruses released by budding through a membrane-ex. ER/cytoplasmic/etc- thus gaining their envelope) Retrovirus An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses. DNA virus DNA is replicated and form new viral DNA => transcribed to produce viral proteins (DNA + viral proteins assemble to form new viruses). The protein coat disintegrates in the cytoplasm, DNA enters nucleus where replication and transcription occurs, mRNA goes to cytoplasm for translation of capsid proteins, return to nucleus for virion assembly RNA Virus A virus in which the genetic information is stored in the form of RNA (as opposed to DNA). Reproduction occurs in the cytoplasm Ex. Picornavirus Complex virus A virus with a complicated structure, such as a bacteriophage. virion complete virus particle Antiviral drugs: Inhibition of virus entry- EXAMPLES Amantidine: Blocks HIV by preventing it from binding to cell receptors Tamiflu: Blocks INFLUENZA by interfering with virus's fusion to cell membrane, stops neuraminidase. Take within 24 hours! Antiviral drugs: Inhibition of nucleic acid synthesis- EXAMPLES Acyclovir: inactivates DNA polymerase, stopping DNA replication in HERPES VIRUSES AZT/Zidovudine: Stops reverse transcriptase in HIV, blocking DNA production Nevirapine: Attaches/blocks HIV rt binding site Antiviral drugs: Inhibition of Viral Assembly/Release- EXAMPLE Saquinavir: Inserts into HIV protease, resulting in inactive viruses protease enzyme that breaks down proteins Vaccination sheets Tells you what you need to know, signed by parents/guardians if minor, nurses have vaccination sheets for many vaccines(Antibodies!) Hep, tetanus, diptheria, etc 6 Requirements for Effective Vaccines 1. Low level adverse side effects, no serious harm/toxicity 2. Protect against exposure to wild, natural, and artificial forms of pathogen 3. Stimulates antibody(B-cell) and cytotoxic(T-cell) response 4. Long term, lasting effect(memory!) 5. Not too many boosters or doses 6. Inexpensive, easy to administer, long shelf life Tdap vaccine/DTP vaccine tetanus, pertussis, and diptheria A toxoid vaccine Why vaccinate? To protect individuals To establish herd immunity - Protection of the whole population Prevention of epidemics - Protection of non-immunized individual How do vaccines work? - pathogen stimulaties wbc into making antigens - dead or inactive pathogen enter body via injection - antibodies stick to antigens and clump them together - memory cells = immunity Stimulate immunity with exposure to the pathogen Innate immunity first line of defense (chemical/physical/cellular barriers) Adaptive immunity the ability to recognize and remember specific antigens and mount an attack on them second line of defense aka acquired immunity Humoral immunity B cells produce antibodies after exposure to specific antigens; type of adaptive immunity cell-mediated immunity type of immunity produced by T cells that attack infected or abnormal body cells; type of adaptive immunity T cytotoxic cell the only T Cells that can DIRECTLY attack and kill diseased cells- including cancer cells T-Helper cell contacts the displayed antigen fragment and releases cytokines that activate B cells T-Suppressor cell Suppresses or stops the reaction of T & B cells or immune reaction Natural Killer Cell A type of white blood cell that can kill tumor cells and virus-infected cells as part of innate immunity, WITHOUT the stimulation of antigens Natural immunity acquired as part of normal life experiences artificial immunity protection from infection obtained through medical procedures Active natural immunity antibodies developed in response to an infection/being sick Active artificial immunity vaccination. Deliberate exposure to an antigen (vaccine) Passive natural immunity IgG transferred from mother to fetus: Across placenta Through breast milk Protection of infant for the first few months of life or until weaned Passive artificial immunity injection of antibodies (immune globulin) short term protection Vaccines with dead/inactive material are made by... Killing the cell/inactivating the virus bye heat or chemicals to denature the proteins and stop attachment but keep cell recognition Pathogens CANNOT multiply Attenuated vaccines are made with... Weakened living pathogens(with reduced virulence) Pathogens can multiply but NOT enough to sicken The only attenuated vaccine issue Polio and babies Cutter vaccine 1955 The influenza vaccine is made of________. glycoprotein spikes from multiple strains of flu viruses (microbe parts vaccine) Acellular vaccine A vaccine preparation that contains parts of BACTERIA to elicit immune response as opposed to the whole cell Type of microbe parts vaccine Examples of Acellular vaccines Tetanus- uses toxin Whooping cough Campylobacter/salmonella- Flagella vaccine Subunit vaccine Vaccine containing only specific antigenic proteins of the infectious VIRUS Microbe parts vaccine Parts of the microbe(antigens, virus or bacteria) are used to stimulate immunity but NO pathogens are present