Lecture 17: Poxvirus, Picornavirus, Coronavirus - Chap 44, 46, 47 Flashcards
What type of genome do Poxviruses possess?
Linear double-stranded DNA
Describe the structure of Poxviruses.
Large, oval/brick-shaped with complex structure, containing core membrane, lateral bodies, surface tubules
Where does Poxvirus replication occur, and why is this unique?
In the cytoplasm, unique for a DNA virus because it must encode its own replication enzymes
What immune evasion strategies do Poxviruses use?
Virokines, viromimicry, virotransduction, and virostealth to evade immune responses
What diseases are caused by Poxviruses?
Smallpox, Molluscum contagiosum, Orf, and Monkeypox
How is Smallpox transmitted, and what are key symptoms?
Respiratory droplets; symptoms include fever, rash with pustules, malaise
Describe the lifecycle stages of Poxvirus replication.
Early gene transcription, DNA replication in inclusion bodies, late gene expression for structural proteins
Why was Smallpox eradication possible?
Human-only host, single serotype, consistent symptoms, effective vaccine
What is Molluscum contagiosum, and how is it transmitted?
A Poxvirus infection causing non-lytic papules; transmitted by contact
What type of genome do Picornaviruses have?
Single-stranded positive-sense RNA
Describe the Picornavirus structure.
Non-enveloped, icosahedral capsid; very small (~25-30 nm)
What is unique about Picornavirus replication?
RNA serves as mRNA, directly translated into a polyprotein, which is cleaved into functional proteins
What diseases are associated with Enteroviruses (a Picornavirus group)?
Poliomyelitis, hand-foot-and-mouth disease, viral meningitis
How does Poliovirus cause disease in the body?
Infects lymphoid tissue, spreads via viremia, and may affect the nervous system causing paralysis
Describe the immune response to Enteroviruses.
IgA provides mucosal protection; IgG prevents viremia, helping to control disease spread
How is Poliovirus controlled?
Through vaccination (IPV - inactivated, OPV - live oral vaccine)
What are the main transmission routes for Enteroviruses?
Fecal-oral, respiratory aerosols, and fomites
How is Enterovirus infection diagnosed?
PCR for viral RNA; culture from throat swabs or fecal samples
What structure gives Coronaviruses their name?
The crown-like spike (S) proteins on the viral envelope
Describe the genome type of Coronaviruses.
Single-stranded positive-sense RNA
Explain the two-phase replication process of Coronaviruses.
Early phase produces RNA polymerase; late phase generates structural proteins from a negative-sense RNA template
What role do spike proteins play in Coronavirus infections?
Allow binding to host receptors (e.g., ACE2 for SARS-CoV-2), facilitating entry into cells
What diseases are caused by Coronaviruses?
Common cold, SARS, MERS, and COVID-19
How does COVID-19 affect the body?
Causes respiratory issues, systemic inflammation, and may lead to severe complications like ARDS
What immune evasion mechanisms are used by Coronaviruses?
Several non-structural proteins (e.g., PLPro, NendoU) suppress immune signaling
How is COVID-19 primarily transmitted?
Respiratory droplets, airborne particles, and contact with contaminated surfaces
What are common symptoms of COVID-19?
Fever, cough, fatigue, loss of taste/smell, shortness of breath
What high-risk groups are most affected by COVID-19?
Older adults and people with chronic conditions like heart disease, diabetes, and obesity
How is COVID-19 diagnosed?
RT-PCR for viral RNA from nasal or throat swabs
What treatments are available for COVID-19?
Antivirals (e.g., remdesivir), supportive care, and vaccination
Describe control measures for COVID-19.
Vaccination, quarantine, mask-wearing, social distancing
How did SARS and MERS outbreaks inform COVID-19 response?
Highlighted zoonotic transmission, need for quarantine, and rapid vaccine development
What vaccination types are available for COVID-19?
mRNA vaccines (Pfizer, Moderna), viral vector vaccines (J&J)
Explain the significance of the Coronavirus envelope.
Protects RNA genome and enhances survival in the respiratory and GI tracts
What diagnostic tools are used for Poxvirus infections?
Serology, electron microscopy, PCR for viral DNA
What treatments are used for severe Poxvirus infections?
Vaccinia immune globulin, cidofovir for vaccinia complications
Question
Answer
Which virus is associated with warts and cervical cancer?
HPV (Human Papillomavirus)
What do HPV types 16 and 18 increase the risk of?
Cervical, anal, penile, and oropharyngeal cancers
How does HPV evade immune detection?
Hides from immune responses, allowing persistent infection
What cells does HPV primarily infect?
Epithelial cells of skin or mucous membranes
What are the key oncogenes in HPV that promote cell growth?
E6 and E7 proteins
How does HPV affect p53 and RB proteins?
Inactivates them to promote uncontrolled cell growth
What is the common symptom of HPV infection on the skin?
Benign warts
How is HPV commonly transmitted?
By direct or sexual contact, and fomites
Which method is used for HPV detection in clinical settings?
PCR genome analysis of cervical swabs
Which HPV types are targeted by available vaccines?
Types 6, 11, 16, 18, 31, 33, 45, 52, and 58
What virus is linked to Merkel cell carcinoma?
MCPyV (Merkel Cell Polyomavirus)
What disease does JCV cause in immunocompromised individuals?
Progressive multifocal leukoencephalopathy (PML)
How is JCV transmitted?
Inhalation or contact with contaminated water or saliva
What type of cells are affected in JCV-associated PML?
Astrocytes and oligodendrocytes
What is a distinguishing characteristic of PML lesions?
Demyelination with large abnormal astrocytes and oligodendrocytes
How is PML diagnosed in patients suspected of JCV infection?
PCR detection of viral DNA in cerebrospinal fluid and MRI/CT scans
What organ is primarily affected by BK virus in immunocompromised individuals?
Kidneys
How do polyomaviruses, such as BK virus, maintain persistent infection?
Establish latent infection in organs like kidneys and lungs
Which proteins do both HPV and polyomaviruses use to disrupt cell cycle regulation?
T antigen (in polyomaviruses) and E6/E7 proteins (in HPV)
What method is ineffective for polyomavirus control and treatment?
No effective mode of control is currently available
How does HPV tissue tropism vary by type?
Specific HPV types infect different tissues and determine disease manifestation
Which polyomavirus is commonly associated with kidney disease?
BK virus
What triggers reactivation of JCV and BK virus?
Immunocompromised state
Why are JCV infections usually asymptomatic in early life?
The virus remains latent and does not cause symptoms in healthy individuals
In which population are both HPV and polyomaviruses a significant health concern?
Immunocompromised individuals
What does CIN stand for in relation to HPV infection?
Cervical Intraepithelial Neoplasia
How do HPV infections typically resolve?
Slowly and often spontaneously due to immune response
What is the main transmission method for HPV laryngeal papillomas?
Passage through an infected birth canal (Types 6 and 11)
How is HPV distributed worldwide?
Ubiquitously, with no seasonal incidence
Why does JCV infection lead to progressive neurological symptoms?
Due to demyelination and damage to brain cells
Which two types of polyomaviruses are specifically noted for opportunistic disease?
JCV and BK virus
Why are warts common with HPV infection?
Caused by benign outgrowth of infected epithelial cells
What demographic factor increases the risk of BK virus-related kidney disease?
Immunosuppression (e.g., transplant patients)
What type of genome do papillomaviruses and polyomaviruses have?
DNA genome
How would you describe the capsid structure of papillomaviruses?
Small, naked capsid
What is the significance of a ‘naked capsid’ in virus structure?
Resistant to environmental stress, aids in transmission
Which proteins are key for HPV’s ability to manipulate the host cell cycle?
E6 and E7 proteins
What role does the T antigen play in polyomaviruses?
Inactivates p53 and RB to promote cell growth
How does the HPV genome influence its tissue tropism?
Specific HPV types target different epithelial tissues
Where does HPV persist in the body during infection?
Basal layer of skin or mucous membranes
What is the genome type of polyomaviruses like JCV and BK?
DNA genome
What is a key feature of the HPV genome in terms of immune evasion?
Remains hidden from immune system
How does JCV affect the brain in immunocompromised patients?
Causes demyelination by damaging brain cells
What is the structure of HPV genome?
Double-stranded circular DNA genome
What HPV protein binds origin and helps increase transcription?
E1 protein
Which HPV protein helps with the release of virions?
E4 protein
Which protein is responsible for EGFR activation in HPV?
E5 protein
What are the structural capsid proteins in HPV?
L1 and L2
Describe the genome structure of adenovirus.
Linear double-stranded DNA
What unique feature does adenovirus capsid have?
Icosahedral capsid with fibers at vertices
What genome structure does parvovirus have?
Single-stranded linear DNA
What key function does HPV’s E6 protein serve in oncogenesis?
Binds p53, activates telomerase, suppresses apoptosis
How does E7 protein promote cancer in HPV?
Binds to p105RB, promoting cell cycle progression
What proteins in polyomavirus help regulate early and late gene transcription?
Large T antigen
Which polyomavirus protein is a major capsid and attachment protein?
VP1
What is the main disease mechanism in parvovirus B19 infection?
Infects erythroid precursor cells, causing lytic infection
What does CIN1 represent in HPV infection?
Mild changes affecting 1/3 of cervical layer
Describe CIN2 in HPV infection.
Moderate changes affecting 2/3 of cervical layer
What is CIN3 in HPV pathology?
Severe changes affecting full cervical layer, not yet cancer
What is progressive multifocal leukoencephalopathy (PML)?
A JCV-caused demyelinating disease in immunocompromised individuals
What condition can adenovirus cause in crowded environments like camps?
Pharyngoconjunctival fever
How is HPV typically transmitted?
Direct and sexual contact, birth canal for types 6 and 11
How is adenovirus transmitted?
Respiratory droplets, fecal-oral route, contaminated surfaces
What age group is most at risk for parvovirus B19?
Children in elementary school
Which demographic is at risk for severe B19 complications?
Non-immune pregnant women and those with chronic anemia
Who is at risk for PML with JCV reactivation?
Immunocompromised patients
What age group is often affected by adenovirus in crowded settings?
Children under 14
What diagnostic test is commonly used for HPV?
PCR genome analysis
How is PML diagnosed in suspected JCV infection?
PCR on cerebrospinal fluid, MRI or CT for lesions
What diagnostic method is used for adenovirus typing?
PCR of respiratory or fecal samples
How is parvovirus B19 infection confirmed?
PCR or IgM antibody test
What vaccine protects against multiple HPV types?
Gardasil 9
What HPV types are included in Gardasil 9?
Types 6, 11, 16, 18, 31, 33, 45, 52, 58
Is there a vaccine for adenovirus?
Yes, for military use covering types 4 and 7
How is parvovirus B19 infection typically controlled?
No specific treatment; managed with supportive care
What type of immune response is crucial for clearing parvovirus B19?
Antibody response
What is a control method for adenovirus in shared environments?
Good hygiene and disinfection of contaminated surfaces
What are key poxvirus immune evasion proteins?
Virokines, Virostealth, and Virotransduction proteins
What is the primary clinical difference between variola major and minor?
Variola major has >30% mortality, minor <5% mortality
What was the key factor for smallpox eradication success?
Exclusive human host range, single serotype, effective vaccine
What are risks associated with the smallpox vaccine?
Encephalitis, vaccinia necrosum, spread to contacts
What is vaccinia immune globulin used for?
Treatment of severe vaccine complications like vaccinia necrosum
What are the four stages of poliovirus infection outcomes?
Asymptomatic, abortive, non-paralytic, paralytic polio
Which picornavirus receptor is known as the poliovirus receptor?
CD155
What does CD155 receptor facilitate in poliovirus infection?
Adhesion and cell entry for viral replication
How does ICAM-1 function in rhinovirus infection?
Acts as the primary receptor for rhinovirus attachment
What is a major difference between live (OPV) and inactivated (IPV) polio vaccines?
OPV induces mucosal immunity; IPV induces systemic immunity
What are the main structural proteins in coronaviruses?
Spike (S), Membrane (M), Envelope (E), Nucleocapsid (N)
What are the two phases of coronavirus replication?
Early phase for RNA polymerase, late phase for structural proteins
What symptom uniquely distinguishes COVID-19 from other coronaviruses?
Loss of taste and smell
What proteins help coronaviruses evade immune response?
Non-structural proteins like PLPro and Mpro
How does SARS-CoV differ from common coronaviruses?
Can replicate in lower respiratory tract causing severe infection
What is the infectious dose of norovirus?
10-100 virions
What environmental factors can norovirus resist?
Acid, detergents, drying
What is the primary symptom of norovirus infection?
Gastroenteritis with vomiting and diarrhea
What is a key treatment method for norovirus dehydration?
Oral rehydration or IV fluids
What kind of rashes can be caused by viral infections for diagnosis?
Maculopapular, petechiae, vesicular rashes
How is norovirus typically diagnosed?
RT-PCR of stool samples
What is unique about the poxvirus replication process?
Replicates in cytoplasm and requires virus-encoded RNA polymerase
Why is cell-mediated immunity critical in resolving smallpox infection?
Necessary to eliminate infected cells and control systemic spread
What enzyme assists in poxvirus uncoating?
Uncoatase
Where does poxvirus assembly occur?
Guarnieri bodies (inclusion bodies) in the cytoplasm
What is the function of the E1 matrix protein in coronavirus?
Helps in membrane assembly
Describe the replication process of coronavirus in terms of genome translation phases.
Two phases: early (produces RNA polymerase L) and late (yields structural proteins)
What immune evasion strategy involves mimicking host proteins in poxviruses?
Viromimicry
Which coronavirus protein assists in evading host immune responses?
PLPro (papain-like protease)
How does molluscum contagiosum evade the immune system?
Uses about 30% of its genome for immune evasion mechanisms
What structural protein in poxvirus contributes to its dumbbell shape?
Lateral Bodies
What are the primary structural proteins in picornavirus capsids?
VP1, VP2, VP3, and VP4
What is the role of the spike (S) protein in coronaviruses?
Attachment to host cell receptors and entry
What is a unique feature of smallpox rash compared to chickenpox?
Smallpox rash erupts all at once
What is a hallmark symptom of poliovirus-related paralytic polio?
Asymmetric flaccid paralysis without sensory loss
Which coronavirus symptom is notably common in COVID-19 but rare in other coronaviruses?
Loss of taste and smell
What are the main differences between OPV and IPV polio vaccines?
OPV is live oral; IPV is inactivated injected vaccine
What antiviral is used in severe poxvirus complications like vaccinia necrosum?
Cidofovir
What is the preferred vaccine for smallpox, and why?
Cowpox-derived vaccine (vaccinia) due to cross-protection and safety
What diagnostic test is commonly used to confirm norovirus?
RT-PCR of stool samples
What seasonality is associated with rhinovirus infections?
Common in early autumn and late spring
How does poliovirus evade the acidic conditions of the digestive system?
Encased in a resistant icosahedral capsid
What structural feature allows norovirus to persist in the environment?
Highly stable naked capsid resistant to detergents and drying
