VIROLOGY-Intro to HHV 8 PDF

VIROLOGY-Intro to HHV 8 Introduction VIROLOGY- is the scientific study of viruses, submicroscopic infectious agents that replicate only inside the living cells of other organisms. Unlike cellular organisms, viruses lack the ability to independently reprod...

VIROLOGY-Intro to HHV 8 Introduction VIROLOGY- is the scientific study of viruses, submicroscopic infectious agents that replicate only inside the living cells of other organisms. Unlike cellular organisms, viruses lack the ability to independently reproduce, metabolize, or respond to stimuli. DISCOVERY In 1892, Dmitri Ivanovsky used one of these filters to show that sap from a diseased tobacco plant remained infectious to healthy tobacco plants despite having been filtered. Martinus Beijerinck called the filtered, infectious substance a "virus" and this discovery is considered to be the beginning of virology. VIRUSES Simple, acellular cytoplasmic membrane Distinct pattern of cytosol multiplication functional organelles Cell line or tissue Culture; not sensitive to antibiotic BACTERIOPHAGES - metabolic activity VIRAL STRUCTURE VIROLOGY-Intro to HHV 8 1  What are viruses? Not living organisms They are obligate intracellular “parasites” Lack cellular structures Transmit via vectors Replicate very quickly #Go_Viral they contain either DNA or RNA, but not both* they are incapable of replication unless occupying an appropriate living host cell they are incapable of metabolism The classification of viruses is based on: nucleic acid type size and shape of virion, and presence or absence of an envelope. VIROLOGY-Intro to HHV 8 2  CELLS: VIRUSES: can replicate INDEPENDENTLY CANNOT replicate INDEPENDENTLY can make their own proteins CANNOT make their own proteins can produce energy CANNOT produce energy can be seen by Light Microscopy CANNOT be seen by Light Replicates by mitosis or binary Microscopy fission neither have a nucleus or a Cell membrane is found in every cytoplasm. cell. n/a Nuclear material is dna & rna. An envelope is found in some Proteins are abundant. viruses. Ribosomes are present. Either dna or rna (never Mitochondria: (Prokaryotes: both).Proteins are few. absent) (eukaryotes: present) Ribosomes are absent (EXCEPT Enzymes are many. ARENAVIRUS). MITOCHONDRIA ARE ABSENT. ENZYMES ARE FEW OR NON- EXISTENT. VIRUSES DNA (7) RNA (15) Pox -Toga, Flavi, Retro, Corona, Delta, Arena, Bunya, Filo, Rabdo, Orthomyxo, Herpes Paramyxo, Picorna, Calici, Hepe, Reo Hepadna (no envelope) Parv Pap VIROLOGY-Intro to HHV 8 3  Poly Adena (no envelope) REPLICATION 1. Adsorption- First to recognize and bind to a suitable host referred to as attachment. 2. Penetration is entry of the virus into the host cell. 3. Uncoating occurs when there is either the separation of the capsid from the genome or rearrangement of the capsid proteins exposing the genome for transcription and replication. 4. The eclipse period is the stage when the genetic material is replicated but intact virions are not yet detectable. a. Viral DNA or RNA serves as the template for mRNA production. b. mRNA codes for viral protein and enzymes necessary for nucleic acid synthesis. 5. Assembly (maturation): Genetic material is assembled into a protein coat. 6. Viruses are then released from the host cell. a. Cell lysis: Naked viruses lyse host cell and leave through a hole in the plasma membrane. b. Budding: Intact virion pushes outward from a host's membrane. The membrane wraps around the virion; the membrane is cleaved and then resealed around the virion, thus becoming the viral envelope. Specimen Collection Site for Diagnosing Viral Diseases 1. Viruses are in highest concentrations during the first several days following onset of symptoms. VIROLOGY-Intro to HHV 8 4  2. Samples should generally come from the infected site. a. Skin infections: Rash site and, depending on the virus, serum and urine b. Respiratory infections: Sputum or throat swabs c. Central nervous system (e.g., meningitis and encephalitis)- -**(CSF) is the most important specimen -**In cases of encephalitis, brain biopsy material and sometimes serum are used. d. Urogenital infections: Needle aspirates and endocervical and urethral swabs e. Gastrointestinal tract: Stool samples and rectal swabs f. Eye infections: Eye swabs and corneal scrapings Sample Transport 1. Samples for viral culture must be placed into a viral transport medium (VTM). 2. VTM contains: a. Buffered saline- to maintain pH. b. Protein stabilizers- to protect the virus from degradation. c. Antimicrobials that inhibit bacterial and fungal growth, which could interfere with virus isolation. 3. Samples for viral cultures can be refrigerated in VTM for about 48 hours, but they should never be frozen at -20°C. Storage at -70°C: While storage at -70°C can reduce infectivity for some viruses, it is a viable option for many viruses and is often used for long-term storage in research and clinical settings. SAMPLE SITES AND ASSOCIATED VIRAL AGENTS Respiratory System VIROLOGY-Intro to HHV 8 5  1. Upper respiratory tract infections: rhinovirus, influenza virus, parainfluenza virus, adenovirus respiratory syncytial virus (RSV), Epstein- Barr virus (EBV), and coronavirus. Rhinovirus: A major cause of the common cold. Influenza virus: Causes seasonal flu. Parainfluenza virus: Can cause croup in children. Respiratory syncytial virus (RSV): A common cause of respiratory infections, especially in infants and young children. Epstein-Barr virus (EBV): While primarily associated with infectious mononucleosis, EBV can sometimes cause upper respiratory symptoms. Coronavirus: Includes SARS-CoV-2 (the virus that causes COVID-19) and other coronaviruses that can cause milder respiratory illnesses. 2. Croup and bronchitis: RIPA influenza virus parainfluenza virus RSV adenovirus 3. Pneumonia in children: PARV RSV (common cause of pneumonia, especially in infants and young children.) parainfluenza virus- (cause croup but can also lead to pneumonia in children) adenovirus varicella-zoster virus (VZV)- rare but possible complication of chickenpox (especially in immunocompromised individuals). 4. Pneumonia in adults: CRIV influenza virus VZV cytomegalovirus (CMV)- in immunocompromised individuals. VIROLOGY-Intro to HHV 8 6  RSV (can also cause pneumonia in adults, especially older adults and those with underlying health conditions.) Viral Meningitis Caused by: HHEEMV Enterovirus- common cause of viral meningitis, especially in children Echovirus Herpes simplex virus type 1 (HSV-1)- can cause meningitis, although it's less common than HSV-2 HSV-2 VZV Mumps virus Encephalitis Infections are caused by: HAV HSV- both HSV-1 and HSV-2 can cause encephalitis. VZV- in people with weakened immune systems Arboviruses- (West Nile virus, Japanese encephalitis virus, and Eastern Equine Encephalitis virus) ** A number of animals, including birds and horses, serve as reservoirs for these viruses. Rabies virus is also an uncommon cause of encephalitis. Cutaneous Infections Caused by: RHHEEMV HSV-1 (cold sores) HSV-2 (genital herpes) VIROLOGY-Intro to HHV 8 7  VZV (chickenpox and shingles) Echovirus (can cause skin rashes, especially in children) Measles virus (widespread, blotchy rash) Rubella virus (also known as German measles, causes a rash) Enterovirus (While some enteroviruses can cause skin rashes, it's not a universal characteristic of all enteroviruses.) Continuation of cutaneous infections Molluscum Contagiosum Virus (MCV) - This poxvirus causes small, pearly- white bumps on the skin. parvovirus B-19 - can cause a distinctive slapped-cheek rash in children Genital Infections (Urethritis, Cervicitis, etc.) 1. Frequently caused by HSV-2 (genital herpes) and human papillomavirus (genital warts). 2. Genital tract infections are typically sexually transmitted. ** Urethritis and Cervicitis: While HSV-2 and HPV can contribute to urethritis (inflammation of the urethra) and cervicitis (inflammation of the cervix), other pathogens, such as Chlamydia trachomatis and Neisseria gonorrhoeae, are also major causes of these infections. Gastroenteritis: RANC Rotaviruses (major cause of severe diarrhea, especially in young children.) Norwalk viruses (also known as “noroviruses”, are a common cause of acute gastroenteritis, often referred to as "stomach flu." They can cause vomiting, diarrhea, and abdominal cramps.) Adenoviruses (some can cause diarrhea, particularly in young children) VIROLOGY-Intro to HHV 8 8  Caliciviruses The symptoms can range from mild self-limiting diarrhea to severe diarrhea with dehydration, particularly with rotavirus infections in young children. Eye Infections 1. Caused by (HAV) HSV (Both HSV-1 and HSV-2 can cause eye infections, including herpes simplex keratitis) Adenovirus (common cause of conjunctivitis ) VZV 2. Viruses can cause conjunctivitis and severe cases of keratitis, resulting in blindness. Neonatal Infections 1. Neonatal infections are acquired in utero, during childbirth, or soon after childbirth. 2. The infections can be caused by HSV, CMV, and rubella virus. VIRAL IDENTIFICATION Histology and Cytology 1. Cellular inclusions are diagnostic for many viruses. 2. Because most DNA viruses replicate in the nucleus, they often produce nuclear inclusions. However, some DNA viruses are assembled elsewhere in the cell. 3. RNA viruses produce cytoplasmic inclusions (assembled in the cytoplasm). VIROLOGY-Intro to HHV 8 9  Inclusion Bodies 1. Guarniere- Eosinophilic Cyctoplasmic Inclusion 2. Councilman Inclusion- Yellow fever virus, Acute viral hepatitis 3. Cowdry inclusion- HSV (A), VZV (A), and CMV (B) 4. Owl Eye- CMV 5. Negri-body- Rabies virus Viral Isolation A. Cell culture Cell cultures require nutritionally rich complex media. The media often contain fecal calf serum as a nutrient. Viruses have an affinity for specific cell types (e.g, respiratory epithelium, neurons, etc.). 1. Primary cell cultures derived directly from tissue. These cells have a normal number of chromosomes (diploid) and are permissive for a number of viruses, but they can only be maintained for a short time in the laboratory. They are used to grow influenza virus, parainfluenza virus, enteroviruses, and adenoviruses. 2. Established cell lines or “low passage” or “finite cell lines,” are also diploid can be maintained longer than primary cell lines but they are not as permissive. VIROLOGY-Intro to HHV 8 10  Examples of established cell lines include WI-38, MRC-5, and IMR-90. 3. Continuous cell lines are altered cells that can be maintained indefinitely. heteroploid, HeLa, HEp-2, A549, and Vero cells are examples They can be used to grow HSV, VZV, CMV, adenovirus, and rhinoviruses. B. Embryonated eggs are sometimes used for growth of viruses. to cultivate viruses for research studies and vaccine preparation (ex: influenza virus). C. Animal models are sometimes used in research studies. Electron Microscopy Due to size, most individual virions can only be seen by electron microscopy. Disadvantages: expensive requires expertise usually not very sensitive ** electron microscopy is not commonly used. Other Methods for Identification 1. Detection of host antibodies directed against specific viruses. 2. Viral gene probes and nucleic acid amplification (e.g., polymerase chain reaction [PCR]) VIROLOGY-Intro to HHV 8 11  MEDICALLY IMPORTANT DNA VIRUSES Remember!!! Always be: H epadnaviridae H erpesviridae A denoviridae P apillomaviridae P olyomaviridae P arvoviridae P oxviridae y Rules: DNA Viruses 1. All are D-S DNA EXCEPT Parvovirus 2. All are icosahedral EXCEPT POXVIRUS 3. All are enveloped EXCEPT “P-A-P” (Pap, Adeno, Parvo) 4. All multiply in nucleus EXCEPT Poxvirus Herpesviridae Characteristics: Double stranded DNA Family name: Herpesviridae Icosahedral capsid with envelope At least 8 human herpes viruses known: HSV-1,HSV-2,VZV, EBV, CMV, HH6,HH7, and HH8 VIROLOGY-Intro to HHV 8 12  Herpes Simplex Virus type 1 and type 2 HSV-1- is transmitted by oral to oral contact to cause oral herpes (which can include symptoms known as “cold sores”), but can also cause genital herpes. HSV-2 – sexually transmitted infection that causes genital herpes. Both HSV-1 and HSV-2 infections are life-long. HSV-1 Highly Contagious infection,which is common and endemic throughout the world Vast majority of infection are oral herpes Cold sores Cold Sore Signs and symptoms Mostly asymptomatic, and majority of the people are unaware they are infected. Painful blisters or open sores called ulcers in or around the mouth Transmission (HSV - 1) Mainly transmitted by oral to oral contact to cause oral herpes infection, via sores, saliva, and surfaces around the mouth. It can be transmitted from oral or skin surfaces that appear normal and when there are no symptoms. How HSV-1 spreads Kissing: HSV-1 can spread through kissing Oral sex: HSV-1 can spread through oral-genital contact Sharing objects: HSV-1 can spread through sharing objects like lip balm, silverware, or razors VIROLOGY-Intro to HHV 8 13  Skin-to-skin contact: HSV-1 can spread through skin-to-skin contact with an infected person When HSV-1 is most contagious HSV-1 is most contagious when there are active sores However, a person with HSV-1 can spread the virus even if they don't have symptoms ** How to protect yourself Avoid kissing and oral sex while you have symptoms Use a barrier like a dental dam or condom during oral sex HSV-2 It causes genital herpes Infection with this virus is lifelong and incurable The most common cause of genital herpes. Signs and symptoms (HSV - 2) Often have no symptoms or mild symptoms that go unrecognized. When symptoms occur characterized by painful blisters or open sores on the genitals, anus, or surrounding areas. In addition to genital ulcers, symptoms of new genital herpes infection often include fever, body aches, and swollen lymph nodes Transmission (HSV - 2) HSV-2 is mainly transmitted during sex In rare circumstances, HSV-2 infection can be transmitted from a mother to her infant during delivery. VIROLOGY-Intro to HHV 8 14  Disease HSV-1 HSV-2 Gingivostomatitis Genital infection Pharyngitis Herpetic whitlow Herpes labialis Disseminated disease Conjuctivitis Keratitis Herpetic whitlow Encephalitis Disseminated disease (neonates) Detection (HSV) Cell culture EIA- detect the presence of antibodies against HSV. FA stain- (Fluorescent Antibody Staining) PCR- detect the genetic material (DNA) Varicella Zoster Virus Herpesvirus belonging to the subfamily of Alphaherpesvirirdae Acute, highly contagious disease VZV is responsible for causing two distinct illnesses: Chickenpox: A highly contagious childhood disease characterized by a widespread rash of itchy blisters. Shingles: A reactivation of the latent VZV infection, typically later in life, causing a painful, blistering rash along a specific nerve distribution. VIROLOGY-Intro to HHV 8 15  Transmission (VZV) Close person-to-person contact via respiratory droplets Direct Contact: Contact with the fluid from chickenpox blisters can also spread the virus Less common: touching freshly soiled contaminated items Signs and symptoms (VZV) Characterized by an itchy, vesicular rash usually starting on the scalp and face, initially accompanied by fever and malaise. The rash spreads to the trunk and extremities. It normally takes about 7-10 days for all the crust to disappear. Disease Chicken pox (varicella) The hallmark of chickenpox is an itchy rash that starts as small, red bumps. These bumps quickly develop into fluid-filled blisters (vesicles). Shingles (Zoster) Mechanism: After you have chickenpox, the virus remains dormant in your nerve cells. Years later, the virus may reactivate and travel along nerve pathways to your skin, causing shingles. Symptoms (Shingles): Pain: Often the first symptom, can be burning, shooting, or tingling. Rash: A painful, red rash that typically appears as a single stripe of blisters on one side of the body or face. Detection FA stain- (Fluorescent Antibody Staining): This technique uses fluorescently labeled antibodies to detect viral antigens Cell culture- to see if the virus grows and replicates. VIROLOGY-Intro to HHV 8 16  Shell vial culture- a rapid cell culture method PCR- detect the genetic material (DNA) Epstein barr Virus Also known as human herpesvirus 4 A gamma herpes virus that occurs only in humans Transmission Close contact with infected saliva Saliva as a Vehicle: EBV is commonly referred to as the "kissing disease" because it's often transmitted through saliva exchange during kissing. Other Saliva-Involving Activities: Sharing drinks, food, or utensils with an infected person can also expose you to EBV. Site of latency B-lymphocytes: EBV establishes latency (a dormant state) within B-lymphocytes ** This latent infection can reactivate Disease (EBV) Infectious mononucleosis "glandular fever" or the "kissing disease,"- most common disease caused by EBV. ATYPICAL LYMPHOCYTES Downey cells Oral hairy leukoplakia in HIV patients Detection (EBV) VIROLOGY-Intro to HHV 8 17  1. Viral capsid Ag (VCA) Anti-VCA IgM, appears early in EBV infection and disappears within 4-6 weeks Anti-VCA IgG, appears in the acute phase of EBV, peaks at 2-4 weeks 2. Monospot test (Screening test) Not recommended for general use Ab detected by monospot can be cause by other than infectious mononucleosis 3. Hematology – Downey cells EBV and Cancer: Burkitt lymphoma: cancer that affects B-lymphocytes Nasopharyngeal carcinoma: A cancer that develops in the nasopharynx (the upper part of the throat behind the nose). Hodgkin lymphoma: A type of cancer that affects the lymphatic system. Cytomegalovirus MOT: Transplacental, oral, sexual, and by blood and tissue transplant #1 congenital infection; mononucleosis-like but heterophile Ab (-) “Owl eye” Inclusion CMV spreads through contact with bodily Common Routes of fluids, such as: Transmission (CMV) Saliva Sexual contact Blood Blood transfusions Urine Organ transplantation VIROLOGY-Intro to HHV 8 18  Semen Pregnancy (mother to fetus) Breast milk Breastfeeding Organs Test/Specimen (CMV) PAP/ Giemsa stain- Urine/ tissue Blood- to identify active CMV infection Other body fluids (CMV): ** Depending on the clinical situation, other specimens may be tested, such as: Saliva Cerebrospinal fluid (CSF) Amniotic fluid Tissue samples (biopsy) Culture (CMV) - HDF (Human diploid fibroblast cell) Human Herpes virus 6 (HHV6) Disease: Roseola Infantum (SIXTH DISEASE) 9-to 12 month old infant who acutely develops high fever followed by a rash (ROSEY). MOT: Most likely close contact via respiratory route. Site of latency: T lymphocycte (CD cells) Detection: PBS specimen by PCR Human Herpes Virus 8 VIROLOGY-Intro to HHV 8 19  Kaposi Sarcoma- a cancer that causes lesions to grow in the skin, mucous membranes lining the mouth, nose and throat. Lesions are usually purple and are made of cancer cells. VIROLOGY-Intro to HHV 8 20