Quizlet - Viruses Flashcards
Naked Icosahedral virus
Enveloped Icosahedral virus
Enveloped helical virus
Recombination
Exchange of genese btw 2 Chromosomes by crossing over w/in regions of significant base sequence homolgy.
Reassortment
When viruses w/ segmented genomes (e.g., influenza virus) exchange segments. High-frequency recombination. Cause of worldwide influenza pandemics.
Complementation
When 1 of 2 viruses that infect the cell has a mutation that results in a nonfunctional protein. The nonmutated virus complements the mutated one by making functional protein that serves both viruses.
Phenotypic mixing
Occurs w/ simultaneous infxn of a cell w/ 2 viruses. Genome of virus A can be partially or completely coated (forming pseudovirion) w/ surface protein of virus B. Type B protein coat determines the infectivity of the phenotypically mixed virus. However, the progeny from this infxn have a type A coat that is encoded by its type A genetic material.
Viral vaccines
Live attenuated vaccines induce humoral and cell-mediated immunity, but have reverted to virulence on rare occasions. Killed vaccines induce only humoral immunity, but are stable. No boosters are needed for live-attenuated vaccines. It’s dangerous to give live vaccines to immunocompromised pts or their close contacts.
Important live attenuated vaccines
Measles, mumps, rubella, Sabin polio, VZV, yellow fever, smallpox MMR = Measles, mumps, rubella
Important killed vaccines
R abies, I nfluenza, Salk P olio, and HA V vaccines killed = RIP A lways
Important recombinant viral vaccines
HBV (Ag = recombinant HBsAg) HPV (types 6, 11, 16, and 18)
DNA viral genomes
All DNA viruses except the parvoviridae are dsDNA. All are linear except papilloma, polyoma, and hepadnaviruses (circular). All are dsDNA (like our cells), except part-of-a-virus (parvovirus)
RNA viral genomes
All RNA viruses except Reoviridae are ssRNA All are ssRNA (like our mRNA) except re peato virus (reo virus) is dsRNA
Naked viral genome infectivity
Purified nucleic acids of most sdDNA (except poxviruses and HBV) and (+)strand RNA (~mRNA) viruses are infectious. Naked nucleic acids of (-)strand ssRNA and dsRNA viruses are not infectious. They require enzymes contained in the complete viriion.
Virus ploidy
All viruses are haploid (w/ 1 copy of DNA or RNA) except retroviruses, which have 2 identical ssRNA molecules (~diploid)
Viral replication
DNA viruses all replicate in the nucleus (except poxvirus) All RNA viruses replicate in the cytoplasm (except influenza virus and retroviruses)
Non-enveloped viruses (list)
Naked (nonenveloped) viruses include: Calcivirus Picornavirus Reovirus Parvovirus Adenovirus Papilloma Polyoma Naked CPR and PAPP smear
Enveloped viruses
Generally, enveloped viruses acquire their envelopes from plasma membrane when they exit from the cell. Exceptions are herpesviruses, which acquire envelopes from the nuclear membrane.
DNA enveloped viruses (list)
Herpesviruses (HSV types 1 and 2, VZV, CMV, EBV), HBV, smallpox virus
DNA nucleocapsid viruses (list)
Adenovirus, papillomaviruses, parvovirus
RNA enveloped viruses (list)
Influenza virus, parainfluenza virus, RSV, measles virus, mumps virus, rubella virus, rabies virus, HTLV, HIV
RNA nucleocapsid viruses (list)
Enteroviruses (poliovirus, coxsackievirus, echovirus, HAV), rhinovirus, reovirus (rotavirus)
DNA viruses (list)
HHAPPPPy viruses! Hepadna Herpes Adeno Pox Parvo Papilloma Polyoma
All DNA viruses:
1.) Are double stranded (EXCEPT parvo: ssDNA) 2.) All are linear (EXCEPT papilloma and polyoma - circular, supercoiled and hepadna - circular, incomplete) 3.) Are icosahedral (EXCEPT pox: complex) 4.) Replicate in the nucleus (EXCEPT pox - carries own DNA-dep RNA pol)
Viral families: Herpesvirus Envelope? DNA strxr? Medical importance?
Enveloped. dsDNA, linear. HSV-1: oral (and some genital) lesions, keratoconjunctivitis HSV-2: genital (and some oral) lesions VZV: chickenpox, zoster, shingles EBV: mononucleosis, Burkitt’s lymphoma CMV: infxn in immunosuppressed pts, especially transplant recipients; congenital defects HHV-6: roseola (exanthem subitum) HHV-8: Kaposi’s sarcoma-associated virus (KSHV)
Viral families: Hepadnavirus Envelope? DNA strxr? Medical importance?
Enveloped. Partial circular dsDNA. HBV: Acute or chronic hepatitis. Vaccine available: use has increased tremendously. Not a retrovirus, but has reverse transcriptase.
Viral families: Adenovirus Envelope? DNA strxr? Medical importance?
Nonenveloped. Linear dsDNA Febrile pharyngitis - sore throat Pneumonia Conjunctivitis (pink eye)
Viral families: Parvovirus Envelope? DNA strxr? Medical importance?
Nonenveloped. Linear (-)ssDNA (smallest DNA virus). B19 virus: aplastic crises in sickle cell dz, slapped cheeks rash - erythema infectiosum (fifth dz), hydrops fetalis.
Viral families: Papillomavirus Envelope? DNA strxr? Medical importance?
Nonenveloped. Circular dsDNA HPV: warts, CIN, cervical cancer.
Viral families: Polyomavirus Envelope? DNA strxr? Medical importance?
Nonenveloped. Circular, dsDNA. JC: progressive multifocal leukoencephalopathy (PML) in HIV
Viral families: Poxvirus Envelope? DNA strxr? Medical importance?
Enveloped. Linear dsDNA (largest DNA virus). Smallpox, although eradicated, could be used in germ warfare. Vaccinia: cowpox (milkmaid’s blisters) Molluscum contagiosum.
Herpesviruses: HSV-1 Dz? Route of Transmission?
Dz: Gingivostomatitis keratoconjunctivitis temporal lobe encephalitis (most common cause of sporadic encephalitis in the USA) Herpes labialis Transmission: Respiratory secretions Saliva
Dz: Gingivostomatitis keratoconjunctivitis temporal lobe encephalitis (most common cause of sporadic encephalitis in the USA) Herpes labialis Transmission: Respiratory secretions Saliva
HSV-1
Herpesviruses: HSV-2 Dz? Route of Transmission?
Dz: Herpes genitalis [below] Neonatal herpes Transmission: Sexual contact Perinatal
Dz: Herpes genitalis [below] Neonatal herpes Transmission: Sexual contact Perinatal
HSV-2
Herpesviruses: VZV (Varicella-Zoster Virus) Dz? Route of Transmission?
Dz: Shingles (below) Encephalitis Pneumonia Transmission: Respiratory secretions *VZV remains dormant in the trigeminal and dorsal root ganglia.
Dz: Shingles (below) Encephalitis Pneumonia Transmission: Respiratory secretions *VZV remains dormant in the trigeminal and dorsal root ganglia.
VZV (Varicella-Zoster Virus)
Herpesviruses: EBV Dz? Route of Transmission?
Dz: Infectious mononucleosis Burkitt’s lymphoma Nasopharyngeal carcinoma Transmission: Respiratory secretions, saliva
Dz: Infectious mononucleosis Burkitt’s lymphoma Nasopharyngeal carcinoma Transmission: Respiratory secretions, saliva
EBV
Herpesviruses: CMV Dz? Route of Transmission?
Dz: Congenital infxn Mononucleosis (negative Monospot) Pneumonia. Infected cells have characteristic owl’s eye appearance (below) Transmission: Congenital Transfusion Sexual contact Saliva Urine Transplant
Dz: Congenital infxn Mononucleosis (negative Monospot) Pneumonia. Infected cells have characteristic owl’s eye appearance (below) Transmission: Congenital Transfusion Sexual contact Saliva Urine Transplant
CMV
Herpesviruses: HHV-8 Dz? Route of Transmission?
Dz: Kaposi’s sarcoma (in HIV pts) Transmission: Sexual contact
Dz: Kaposi’s sarcoma (in HIV pts) Transmission: Sexual contact
HHV-8
EBV
A herpesvirus. Can cause mononucleosis. Infects B cells. Also associated w/ development of Hodgkin’s and endemic Burkitt’s lymphomas, as well as nasopharyngeal carcinoma.
Mononucleosis due to EBV Sx/findings?
Fever, hepatosplenomegaly, pharyngitis, and lymphadenopathy (especially posterior cervical LNs). Abnormal circulating cytotoxic T-cells (atypical lymphocytes). Positive Monospot test.
When does EBV peak?
Peak incidence 15-20 yrs. Most common during peak kissing years (kissing dz)
Positive Monospot test
Heterophil Abs detected by agglutination of sheep RBCs (positive in EBV infxn)
Herpesviruses (list)
Get herpes in a CHEV rolet C MV H SV E BV V ZV
Tzanck test
A smear of an opened skin vesicle to detect multinucleated giant cells. Used to assay for HSV-1, HSV-2, and VZV. Tzanck heavens I don’t have herpes!
Cowdry A inclusions
Intranuclear inclusions shown in cells infected w/ HSV (would show up on Tzanck smear)
Viral family: Reoviruses Envelope? RNA structure? Capsid symmetry? Medical importance?
No Envelope. dsRNA , linear, 10-12 segments Icosahedral (double) capsid Reovirus: Colorado tick fever Rotavirus: #1 cause of fatal diarrhea in children
No Envelope. dsRNA , linear, 10-12 segments Icosahedral (double) capsid Reovirus: Colorado tick fever Rotavirus: #1 cause of fatal diarrhea in children
Reoviruses
Viral family: Picornaviruses Envelope? RNA structure? Capsid symmetry? Medical importance?
No envelope ss(+)RNA, linear Icosahedral capsid. Poliovirus: polio-Salk/Sabin vaccines – IPV/OPV Echovirus: aseptic meningitis Rhinovirus: common cold Coxsackievirus: aseptic meningitis, herpangina –febrile pharyngitis, hand, foot, and mouth dz, myocarditis HAV: acute viral hepatitis
No envelope ss(+)RNA, linear Icosahedral capsid. Poliovirus: polio-Salk/Sabin vaccines – IPV/OPV Echovirus: aseptic meningitis Rhinovirus: common cold Coxsackievirus: aseptic meningitis, herpangina –febrile pharyngitis, hand, foot, and mouth dz, myocarditis HAV: acute viral hepatitis
Picornaviruses
Viral family: Hepevirus Envelope? RNA structure? Capsid symmetry? Medical importance?
No envelope. ss(+)RNA, linear Icosahedral capsid. HEV
No envelope. ss(+)RNA, linear Icosahedral capsid. HEV
Hepevirus
Viral family: Calciviruses Envelope? RNA structure? Capsid symmetry? Medical importance?
No envelope. ss(+)RNA, linear. Icosahedral capsid. Norwalk virus – viral gastroenteritis.
No envelope. ss(+)RNA, linear. Icosahedral capsid. Norwalk virus – viral gastroenteritis.
Calciviruses
Viral family: Flaviviruses Envelope? RNA structure? Capsid symmetry? Medical importance?
Enveloped. ss(+)RNA, linear. Icosahedral capsid. HCV Yellow fever* Dengue* St. Louis encephalitis* West Nile Virus* (*=arbovirus)
Enveloped. ss(+)RNA, linear. Icosahedral capsid. HCV Yellow fever* Dengue* St. Louis encephalitis* West Nile Virus* (*=arbovirus)
Flaviviruses