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68 Cards in this Set
- Front
- Back
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how are rhinoviruses most reliably isolated? Why are they not enteric pathogens?
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using trachea organ culture; bc they are labile at pH of stomach and grow poorly at core body temp
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other than rhinoviruses, what are 5 other causes of the common cold?
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coronaviruses, respiratory syncitial virus, and parainfluenzavirus, coxsackie and ECHO
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what is the first step in viral replication for reoviruses? What is packaged into the virion to aid in transcription?
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mRNA synthesis from genome; Rna pol
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why is the RNA from reoviris not infectious?
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bc it requires RNA pol to continue
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does the reovirus virion have a gene for the RNA pol or carry the enzyme itself?
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both
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rotaviruses are a subclass of which virus class? What disease do they cause?
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reovirus; diarrhea in infants.
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what is the path of transmission of rotaviruses? What is the treatment for this virus?
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fecal oral; rehydration
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where are adenoviruses assembled? Is viral mRNA and protein synthesis regulated?
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nucleus; yes
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which proteins are made early in an adenovirus infection? Late in the infection?
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proteins needed early in infectionl mRNA for virion (structural) proteins
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how many types of adenovirus exist?
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30
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how are adenoviruses spread?
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airborne
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are all adenoviruses airborne? What is the exception? What symptoms do these cause?
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no; some enteric adenoviruses; gastroenteritis and diarrhea
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what symptoms characterize gastroenteritis?
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vomiting and diarrhea
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how is viral gastroenteritis transmitted normally?
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fecal oral route
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what are the 3 primary viral causes of gastroenteritis?
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rotaviruses, enteric adenoviruses, norwalk virus
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which chemical destroys the infectivity of enveloped viruses?
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ether
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are enveloped viruses stable?
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no
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do enveloped viruses just adopt the PM of the infected cell?
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no, they add glycoproteins
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how many segments of ssRNA are present in an orthomyxovirus? How are the different segments housed?
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8; in individual helical nucleocapsids
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does the orthomyxovirus virion contain the enzyme for RNA pol or does it contain the gene in the genome?
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the enzyme is kept in the virion
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what effect do Ab against nucleocapsids have on enveloped viruses?
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none
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what are the names of the 2 envelope membrane antigens on orthomyxovirus?
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hemagglutinin and neuraminidase
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Ab against which glycoprotein of orthomyxoviruses are more effective?
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hemagglutinin
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which glycoprotein of orthomyxovirus is required for adsorption of virions to cells?
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hemagglutinin
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what is the function of the neuraminidase glycoprotein on orthomyxoviruses? Which bonds does it cut?
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enzyme to release newly formed viruses from their final point of attachment in host cell; sialic acid
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what is the effect of an Anti-neuraminidase on orthomyxoviruses?
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slow release of newly formed virions and consequently slow down the infection in the infected individual and reduce severity of disease
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which process can be used to measure the relative concentration of orthomyxovirus in a clinical sample?
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hemagglutination
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what are the 3 types of human influenza virus?
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A, B, C
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how often do inluenza B epidemics occur?
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every 3-6 years
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how many of each type of influenza virus are contained in the annual killed virus vaccine?
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2 A and 1 B
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how often do minor epidemics of influenza A occur? Major epidemics?
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every 2-3 years; every 10-30 years
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what yields a minor epidemic? What occurs at H antigen?
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minor variation by mutation within existing RNA segments; existing Ab in human population from previous epidemics confers partial immunity; antigenic drift
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what yields a major pandemic? What occurs at H antigen?
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Ab from past epidemics fails to confer any immunity; antigenic shift
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is a pandemic more or less intense if both N and H antigens shift? Why?
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worse; because the patients do not have Ab for either antigen
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what are the mechanisms behind antigenic shift?
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recombination between human and animal influenza A strains or direct transmission of swine or avian influenza into human population
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what must occur to permit genetic recombination between two closely related viruses?
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they must infect cell at more or less the same time
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is genetic recombination more possible in viruses with continous or chopped genomes?
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chopped
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what is the difference between reassortment and genetic recombination?
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they are the same
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what is phenotypic mixing?
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when two viruses simultaneously infect a cell and capsid proteins are mixed when viruses replicate.
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how is diagnosis done for influenza?
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virus isolation in culture or by comparison of acute and convalescent sera or fluorescent Ab on throat swab
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how is the influenza virus transmitted?
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by coughs and sneezes
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what characterizes influenza? What is the pathogenesis? Is viremia common?
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fever, chills, aches; destruction of ciliated respiratory epithelium; no
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what is the most common complication of influenza? Which is the most common secondary bacterial infection with influenza? The most fatal?
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pneumonia; pneumococcus; staphylococcus
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with what are influenza caused deaths usually associated?
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underlying respiratory insufficiency
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how long is the incubation period for influenza? Why?
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short because there is no obligatory viremia
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what is the most important factor in immunity to influenza and in recovery from acute infection?
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IgA in mucosal surfaces
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why is the killed vaccine not optimal for influenza even though it is the predominant type used?
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bc it does not elicit IgA production
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how is the live-attenuated polyvalent influenza vaccine administered?
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intranasally
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influenza A infections can be prevented or treated with which 2 drugs?
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amantadine and rimantadine
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is amantadine more effective if given before or after influenza infection?
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before
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what do Tamiflu and zanamivir inhibit? Are they reactive against influenza A or B? by how many days do they reduce the symptomatic period of the virus?
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neuraminidase; both; one or two
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what is the characteristic of the paramyxovirus mumps and measles infection?
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systemic infections with viremia
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other than measles and mumps, what are two forms of paramyxovirus that do not cause system infections?
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4 types of parainfluenza virus and respiratory syncitial virus;
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What characteristics do parainfluenza viruses and respiratory syncitial viruses share?
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no major shifts in antigenicity; many subclinical infections; severe LRIs on initial infection; agglutination of RBCs
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which virus of the paramyxovirus family causes CROUP?
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parainfluenza
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what characterizes CROUP? When is the peak incidence of CROUP?
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dyspnea and stridor; age 2
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what is the most common cause of severe LRI's in infants and is now recognized as a significant infection of the elderly population? Are vaccines available? Why are adult infections common?
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respiratory syncitial virus; no; bc IgA does not offer long term immunity
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what is effective for preventing severe respiratory syncitial virus pneumonia in high risk infants?
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passive immunity with high doses of mAb against RSV
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how is the SARS-associated coronavirus similar to viruses that cause colds?
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it is genetically and antigenitcally distinct
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what are the principle lower respiratory symptoms of SARS? What is the incubation period of the disease? What is the case fatality rate?
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dry cough and dyspnea; 2-10 days; 9%
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what is the function of the interferon system? What are the 2 classes of proteins in the system? When are these synthesized?
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to suppress viral growth; interferons and virus inhibitory proteins; after a viral infection
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when are virus inhibitory proteins synthesized?
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when plasma membranes of uninfected cells bind interferon molecules
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how do virus inhibitory proteins act?
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Block protein synthesis
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what are the names of the two virus inhibitory proteins?
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2-5-A synthase and a specific protein kinase
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how does 2-5-A- synthase work? A specific protein kinase?
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by activating a ribonuclease which degrades mRNA; by phosphorylating eIF2
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what activates virus inhibitory proteins?
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infection of interferon-treated cells
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what kind of specificity does interferon confer?
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species
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is interferon produced transiently or long-term, compared with antibody?
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transiently
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