RNA viruses

Question 1

Non-enveloped, SS+ non-segmented, icosahedral nucleocapsid RNA viruses

Answer 1

Picornaviridae - RNA is translated into 1 large polypeptide that is cleaved by proteases into functional viral proteins

• Enterovirus
  
  • Poliovirus - paralysis, aseptic meningitis
  • Coxsackievirus - aseptic meningitis, URI
    
    • Type A - herpangina, hand-foot-mouth disaese
    • Type B - myocarditis
  • Echovirus - similar to Coxsackievirus
  • Hepatitis A virus
• Rhinovirus - common cold

Calciviridae

• Calcivirus
  
  • Norwalk virus - institutional gastroenteritis
  • Hepatitis E virus - high mortality in pregnant women

Question 2

Non-enveloped, DS segmented, icosahedral nucleocapsid RNA viruses

Answer 2

**Reoviridae **- only RNA viruses that are DS

• Rotavirus - most common cause of infectious diarrhea in small children (non-bloody); causes villous destruction with atrophy
• Coltivirus - transmitted to humans from rodents via ticks in Rocky Mtns; fever, myalgias, ocular pain, headache

Question 3

Enveloped, SS+ non-segmented, icosahedral nucleocapsid RNA viruses

Answer 3

Togaviridae

• Alphavirus - encephalitis; transmitted to humans from birds or horses via monsquitos; high mortality rate (EEE > WEE > VEE)
• Rubivirus - rubella (fever followed by descending rash, and polyarthritis), congenital rubella (PDA, deafness, PA stenosis, cataracts, blueberry-muffin rash)

Flavaviridae

• Flavivirus - West Nile fever/encephalitis (Langerhans cells, neurons), Yellow fever (hepatocytes), Dengue fever (macrophages), St. Louis encaphalitis (neurons), Japanese encphalitis (neurons)
• Hepatitis C virus - tx with alpha-IFN, ribavirin

Question 4

Enveloped, SS+ diploid, icosahedral nucleocapsid RNA viruses

Answer 4

Retroviridae

• Lentivirus__ (HIV) - gp120 (env) binds CD₄, CXCR4, and CCR5 on T cells and macropahges; gp41 (env) mediates viral-cell fusion and syncytia formation
• HTLV-1/2 - T-cell leukemia/lymphoma; differentiated from HIV by lack of integrase and different surface proteins (gp46, gp21)

Question 5

Enveloped, SS- circular, icosahedral nucleocapsis RNA viruses

Answer 5

Deltavirus

• Hepatitis D - requires hepatitis B surface antigen to form infectious particles; superinfection with HDV increases risk of fulminant hepatitis; HDV genome is unique in that it is a ribozyme (able to cleave and ligate itself)

Question 6

Enveloped, SS+ non-segmented, helical nucleocapsid RNA viruses

Answer 6

Coronaviridae

• Coronavirus - common cold (2nd only to Rhinovirus) “club-shaped” projections on envelope; SARS

Question 7

Enveloped, SS- segmented, helical nucleocapsid RNA viruses

Answer 7

Bunyaviridae

• Bunyavirus (arbovirus) - California Encephalitis (transferred from forest rodents via mosquitos), Rift Valley Fever (sub-Saharan africa), Sandfly Fever (Asia, SA)
• Hantavirus (robovirus) - interstitial pulmonary edema, respiratory failure; airborne transmission from feces/urine of rodents

Arenaviridae

• Arenavirus - Lassa virus (hemorrhagic fever; “sand-like” ribosomal particles in virion; rodent resevoir), Lymphocytic Chroiomeningitis Virus

Orthomyxoviridae

• Influenza virus - hemagglutinin envelope protein binds sialic acid on cells to permit endocytosis, neuroaminidase envelope protein cleaves HA-sialic acid interaction to permit viral spread; M protein involved in assembly

Question 8

Enveloped, SS- non-segmented, helical nucleocapsid RNA viruses

Answer 8

Paramyxoviridae - viral fusion surface protein (F protein) cause infected cells to form multinucleate giant cells; F protein targeted by palivizumab

• Paramyxovirus - Parainfluenza virus (croup); HA/NA binds sialic acid/cleaves sialic acid interaction
• Pneumoviru__s - RSV (bronchiolitis); G protein attaches virus to cells
• Rubulaviru__s - *Mumps virus *(parotitis, orchitis, pancreatitis, aseptic meningitis); HA/NA binds sialic acid/cleaves sialic acid interaction; M protein involved in assembly
• Morbillivirus - Measles virus (Rubeola) - Warthin-Finkelday (multinucleated giant) cells in respiratory secretions; MMR is only live viral vaccines given to HIV+ patients

Rhabdoviridae

• Lyssavirus - Rabies virus; Gp spikes bind to ACh receptors to permit viral entry into peripheral nerves; Negri bodies

Filoviridae

• Filovirus - Ebola virus, Marburg virus; highly glycosylated Gp inhibits strong Ab response