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Flashcards in Intro to Virology Deck (32):

What are the general features of viruses?

obligate parasite, smaller in size than bacteria and cells, RNA or DNA genomes, packaged in protein and sometimes in lipid envelope as well


Why are viruses obligate parasites?

lack ribosomes and must use the hosts to produce proteins


What are the symptoms often seen with viral disease?

rash, fever, conjunctivitis, pharyngitis, gastroenteritis, hepatitis, pneumonia, bronchiolitis, adneopathy, parotitis, meningoencephalitis, arthritis, congenital or perinatal disorders


What is the difference between (+) or (-) RNA?

(+) -> encodes the proteins, readable by our ribosomes; (-) -> have to carry replication enzymes, to make a single copy = mRNA


How are viruses classified? Why do we care?

disease produced, physical characteristics (structures and envelopes), Genome sequence used primarily (PCR amplification to ID and quantify); diagnosis, determine treatment or outcome, best method of disinfection or prevention


What are the different kinds of viral genomes?

RNA or DNA, segmented or monopartite, packaged often as a nucleoprotein.


what are viral envelopes made of?

viral transmembrane proteins (often glycoproteins), some interact with receptors, often have matrix and tegument proteins that interact with envelope and core proteins


What is the process of budding?

when a virus pushes through a membrane structure of the cell allowing acquisition of an envelope


What are the general features of viruses with RNA genomes?

evolve rapidly because of high error rate of RNA-dependent RNA polymerase


What are the general features of viruses with DNA genomes?

use host enzymes to replicate and transcribe mRNA, low error rate, allows for larger genomes, more coding capacity


What is the function of nucleoprotein?

protein for packaging and replication, allows for coiling the complex of genome and protein,


What is the core or capsid of a virus?

protein structure encasing the nucleoprotein, some virion are just capsid and genome (can increase stability of the virion)


What are some characteristic shapes of viruses?

helical, icosahedral, or complex (many different forms)


How do viruses infect?

fomites (susceptible to drying out with envelope, longer if just capsid), droplets (cough or sneeze on to fomites or inhaled), body fluids (blood, semen, urine, slaiva, breast milk), vectors (mosquitos or ticks, virus replicates to increase concentration in saliva)


What are the various modes of Transmission of viruses?

respiratory, fecal-oral, sexual transmission, direct contact, urine-associated transmission, parenteral transmission, vertical (mom to child), arthropod-borne transmission (ticks, mosquitos, sandflies), zoonotic infections (from animals, rodents, even breathing in their urine)


How do viruses get into cells?

receptors= host encoded proteins on cell surface, often between cells and only available during mitosis, bind envelope glycoproteins cause fusion of viral envelope with cell membranes; non-enveloped via endosomes


How is the distribution of effects of a virus determined?

based on the distribution of receptor variants that the virus can bind with= tropisms


What are some antiviral targets?

polymerases- reverse transcriptase or RNA dependent RNA polymerase; viral proteases- cleave viral proproteins to generate infectious virus; components of viral capsid involved in receptor binding; immune activators- interferon B, trx with IgG


How do positive RNA viruses replicate?

bind receptor, conformational change to release RNA, translate to produce viral proteins processed by viral proteases, virion RNA copied by viral RNA-dependent RNA polymerase (cytoplasm), lysis to release virus


How do DNA viruses replicate?

attachment of virus to receptors, entry and fusion with cell membrane, DNA release from core released into nucleus, transcription of viral RNA-> expression of viral proteins including DNA replication proteins and capsid. replicated DNA assembled in cores in nucleus and bud through nuclear membrane


How do retroviruses replicate?

attach virus to CD4 allows entry and fusion with plasma membrane, viral RNA is copied as DNA by reverse transcriptase in nucleocapsid, transport to nucleus, viral cDNA integrated into host genome, viral RNA exported from nucleus, translated, and packaged, viral particles assembled and matured by viral protease


What is the pathway and replication pattern from ingestion of virus to secondary infection?

virus ingested, primary site of infection GI (first replication), primary viremia (circulates through blood stream), replication in second sites (spleen, lymph nodes, meninges, etc), pathogenic virus replication in secondary organs (necrosis, inflammation, etc), virus excreted from primary site and secondary sites (fecal), virus cleared from system by adaptive immune response or becomes persistent


When in the phase of disease is the virus excreted?

prior to symptomatic disease


What can be detected during acute phase of viral infection?

virus cant be detected, but antiviral IgG lasts for years.


What is a persistent infection?

a virus not cleared after acute period, leading to chronic infection (ex: Hep C, herpes simplex, etc), some virus infections can be cleared if a sufficient immune response is generated and/or antiviral therapy is effective


What is a latent virus reactivation?

regulated to prevent virus replication except during short periods of virus activation (herpes, cytomegalovirus, Epstein-Barr), not same as clinical latency (no symptoms of disease)


What is perinatal disease?

infection before birth from mother at birth or via breast milk after birth; HIV, Parvovirus (miscarriage, hydrops fetalis), Rubella (congenital infection, hearing loss, miscarriage, teratogenic), CMV infection (fetal infection, hearing loss, neurologic comp.), Herpes, HBV, Hepatitis E (moratlity of pregnant women), enterovirus (systemic multi-organ disease of neonates) and influenza


What viruses are known to cause cancer?

HBV and HCV- persistent infections-> HCC, HPV: strains associated with cervical cancer and oropharyngeal cancer, Epstein-Barr virus (lymphoma, gastric carcinoma, nasopharyngeal carcinoma), HHV8 (Karposi's sarcoma, lymphoma), HTLV1 (T-cell lymphoma)


What are the various vaccine-preventable viral diseases?

Hep B and A, influenza, measles, mumps, polio, rubella, rotavirus, HPV, shingles and chickenpox, rabies, yellow fever, Japanese encephalitis, small pox, adenovirus


What are some remerging viral disease?

influenza, sin-nombre hanta virus, SARS, Ebolavirus


what viruses are new to humans?

new influenza serogroups, SIV-like primate virus became HIV 1 and 2, Ebola


How are new medical, cultural, agricultural practice results in new transmissions of virus?

west nile virus via birds to New York, global warning increased mosquito populations in temperate region of globe-> inc. dengue and chikungunya infections, and human transport via airplanes