+ RNA Virus Flashcards
What is the genome structure of Togaviruses?
Single-stranded, positive-sense RNA; enveloped.
How does the Togavirus enter a host cell?
Receptor-mediated endocytosis.
What unique replication step do Togaviruses employ?
Synthesis of a subgenomic mRNA for structural proteins.
What diseases are associated with Togaviruses?
Rubella and various encephalitides.
Through which vector are Togaviruses often transmitted?
Mosquitoes.
How does Togavirus evade host immunity?
Modulates interferon response through viral proteins.
What is the structure of Flavivirus?
Enveloped, positive-sense single-stranded RNA virus.
Describe the replication process of Flavivirus.
Endocytosis entry, cytoplasmic replication, single polyprotein production.
What diseases are caused by Flaviviruses?
Dengue, Zika, West Nile fever, Yellow fever, Hep C
What is the primary transmission mode for Flaviviruses?
Vector-borne, mainly via mosquitoes.
How does Flavivirus interact with the immune system?
Inhibits interferon response to prevent immune detection.
What are the structural features of Picornaviruses?
Naked, icosahedral capsid.
Describe the genome type of Picornaviruses.
Positive-sense single-stranded RNA.
How do Picornaviruses replicate?
RNA genome acts as mRNA; translated into a polyprotein.
Name common diseases caused by Picornaviruses.
Polio, Hepatitis A, common cold.
What is the primary route of Picornavirus transmission?
Fecal-oral route, especially for Enteroviruses.
How do Picornaviruses avoid the immune system?
They inhibit host cell mRNA translation selectively.
Describe the genome and structure of Coronaviruses.
Enveloped, positive-sense single-stranded RNA.
How do Coronaviruses enter host cells?
Spike protein binding and membrane fusion.
What is a unique feature of Coronavirus replication?
Replication complex formation on double-membrane vesicles.
What diseases are associated with Coronaviruses?
SARS, MERS, COVID-19.
How are Coronaviruses primarily transmitted?
Respiratory droplets.
How do Coronaviruses evade immune responses?
By delaying interferon responses and suppressing immune signaling.
What is distinctive about the Retrovirus genome?
Two copies of single-stranded positive RNA, reverse transcribed into DNA.
How do Retroviruses replicate?
Integrate DNA copy of RNA into host genome.
What major diseases are caused by Retroviruses?
HIV/AIDS, HTLV (cancers).
What is the primary transmission route for Retroviruses?
Blood, sexual contact, perinatal transmission.
Describe a major immune evasion tactic of HIV.
Frequent mutations in envelope proteins to escape antibodies.
What type of genome does the Norwalk virus have?
Non-enveloped, positive-sense RNA.
Describe the pathogenesis of Norwalk virus.
Infects intestinal cells, causing gastroenteritis.
How is Norwalk virus primarily spread?
Fecal-oral route, through contaminated food or water.
What immune response helps control Norwalk virus infection?
Mucosal immunity, particularly IgA.
What is unique about the Hepatitis A virus (HAV)?
Non-enveloped, positive-sense RNA virus.
How does HAV replicate?
Translated directly from RNA genome as mRNA.
What disease does HAV cause?
Acute hepatitis.
Describe the transmission method of HAV.
Fecal-oral, often through contaminated food or water.
What immune response is effective against HAV?
Antibody-mediated neutralization after infection or vaccination.
What is a common diagnostic method for these RNA viruses?
PCR, ELISA for antibodies or viral proteins.
What prevention methods are effective for these viruses?
Vaccines and vector control for mosquito-borne viruses.
How do antiviral drugs target RNA virus replication?
Inhibit enzymes like RNA polymerase or viral proteases.
What surface protein is critical for Togavirus entry into cells?
E glycoprotein.
What characteristic symptom does Rubella, a Togavirus infection, cause?
A red rash, often called ‘German measles’.
What enzyme is essential for Flavivirus replication?
RNA-dependent RNA polymerase.
How do Flaviviruses modify the host cell during infection?
Reorganize cellular membranes to form replication complexes.
What is a key immune evasion strategy used by Dengue virus?
Antibody-dependent enhancement.
What structural feature allows Picornaviruses to be stable?
Non-enveloped, highly stable icosahedral capsid.
What unique feature does Poliovirus have in its genome structure?
Internal ribosome entry site (IRES) for translation.
How is immunity developed against Poliovirus?
Through oral or inactivated polio vaccines.
What are common symptoms of Hepatitis A infection?
Jaundice, fever, and abdominal pain.
How does Hepatitis A virus survive in the digestive tract?
Resistant capsid to acidic conditions and detergents.
How does the Coronavirus spike protein contribute to infectivity?
Binds to ACE2 receptors to initiate entry.
What is the role of the RNA-dependent RNA polymerase in Coronavirus?
Synthesizes viral RNA in the cytoplasm.
What are the main symptoms of COVID-19?
Fever, cough, difficulty breathing; severe cases can lead to pneumonia.
How do current COVID-19 vaccines work?
Induce immunity to the spike protein of the virus.
What is the hallmark feature of Retroviruses in their life cycle?
Reverse transcription of RNA into DNA.
What cellular receptors are targeted by HIV for entry?
CD4 and co-receptors like CCR5 or CXCR4.
How does HIV lead to immune suppression?
Targets and destroys CD4+ T cells.
What is the main mode of transmission for Norwalk virus?
Direct person-to-person or contaminated food and water.
What are the main symptoms of a Norwalk virus infection?
Nausea, vomiting, diarrhea.
How does Norwalk virus evade the immune system?
Rapid mutation and infection of gut cells.
What immune response helps control Hepatitis A infections?
IgM and IgG antibodies against the virus.
How long does immunity from the Hepatitis A vaccine last?
Typically lifelong after two doses.
What replication feature is unique to Retroviruses like HIV?
Integration of viral DNA into host genome.
How is the Flavivirus envelope structured to evade immunity?
Uses glycosylated proteins that inhibit antibody binding.
How is Hepatitis A diagnosed?
Detection of IgM antibodies via ELISA or serology.
Which enzyme in Retroviruses is targeted by drugs like AZT?
Reverse transcriptase.
What are the typical high-risk groups for Norwalk virus?
Elderly and immunocompromised individuals.
How is immunity to Dengue virus complicated?
Antibody enhancement of disease severity with different serotypes.
What type of vaccine is used for Rubella virus?
Live attenuated, part of MMR vaccine.
What diagnostic method is commonly used for COVID-19?
RT-PCR for viral RNA detection in respiratory samples.
How is the Flavivirus polyprotein processed?
By host and viral proteases into functional proteins.
What is the significance of the “latent” stage in Retrovirus infection?
Virus integrates into host DNA, remains dormant until reactivated.
What is one reason for the success of the Hepatitis A vaccine?
Only one serotype, making the vaccine highly effective.
How does Togavirus mRNA translation occur in the host cell?
Viral RNA serves directly as mRNA for protein synthesis.
What viral protein allows Coronaviruses to escape endosomes?
Spike (S) protein facilitates membrane fusion.
