microbio virology Flashcards
Recombination
exchange of genes between 2 chromosomes by crossing over
Reassortment
when viruses with segmented genomes exchange genetic material; can happen with genes from different kind of virus (human, swine, and avian viruses)
complementation
when 1 of 2 viruses that infects a cell has a non-functioning protein but the other virus provides it. for example, Hep D requires the presence of replicatinghep B virus to supply HBsAg, the envelope protein for HDV
phenotypic mixing
simultaneous infection of a cell with two viruses; genome of virus A can be coated with the surface proteins of virus B; the type B virus coat determines the tropism of the hybrid virus, but the progeny from the infecton ave a type A coat that is encoded by type A genetic material
live attenuated vaccines
induce humoral and cell-mediated immunity; examples are small pox, yellow fever, rotavirus, chickenpox (VZV), Sabin polio virus, MMR, influenza (intranasal); dangerous for immunocompromised people; no booster needed for live atenuated vaccines
killed/inactivated vaccine
induce only humoral immunity; rabies, influenza (injected), Salk polio, and hep A vaccines
Subunit vaccines
Hep B virus; HPV (types 16, 18, 6, and 11)
Naked viral genome infectivity
purified nucleic acids of most dsDNA and the POS strand of ssRNA (=mRNA) viruses are infectious; Naked nucleic acids of the NEG strand ssRNA and dsRNA viruses are not infectious. They require polymerases contained in the complete virion
where do DNA viruses replicate?
the nucleus (except poxvirus_
where do RNA viruses replicate?
cytoplasm (except influenza and retroviruses)
Naked (nonenveloped viruses)
pappilomavirus, adenoviru, parvovirus, polyomavirus, calicivirus, picornavirus, reovirus, and hepevirus
Generally (though there are exceptions), DNA viruese
are ds, linear, icosohedral, and replicate in the nucleus
Herpes viruses
ds, linear, enveloped; include HSV-1, HSV-2, VZV, EBV, CMV, HHV-6/HHV-7, HHV-8
HSV-1
oral (and sometimes genital) lesions; spontaneous temporal lobe encephalitis; keratoconjunctivitis
HSV-2
genital (and some oral) lesions
VZV (aka HHV-3)
chickenpox, zoster (shingles)
EBV (aka HHV-4)
mono, Burkitt-Lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma
CMV (aka HHV-5)
AIDS retinitis; also consider in transplant recipients; congenital defects
HHV-6
roseola (exanthum subitum)
HHV-7
less common cause of roseola
HHV-8
Kaposi sarcoma
Hepadenavirus
enveloped, partially DS, and circular; example is Hep B virus
Adenovirus
not enveloped, DS, linear; febrile pharyngitis, acute hemorrhagic cystitis, pneumonia, conjunctivitis (“pink eye”)
parvovirus
non-enveloped, SS, linear (smallest DNA virus); B19 causes aplastic crisis in sickle cell disease, “slapped cheeks” rash in ids (erythema infectiosum or fifth disease); RBC destruction in fetus leads to hydrops fetalis and death, in adults leads to pure RBC aplasia adn rheumatoid arthriits-like sx
papillomavirus
non-enveloped, DS, circular, causes warts (serotypes 1,2,6,11), CIN and cervical cancer (types 16, 18)
polyomavirus
not enveloped, DS and circular; JC virus cases PML in HIV patients; BK virus can be seen in transplant patients and commonly targets the kidney
poxvirus
enveloped, DS and linear (largest DNA virus); smallpox eradicated by use of live attenuated vaccine; cowpox causes “milkmaid blisters”; molluscum contagiosum causes flesh-colored papulewith central umbilication
HSV-1
gingivostomatitis, keratoconjunctivits, herpes labialis, temporal lobe encephalitis; transmitted by respiratory secretions
HSV-2
herpes genitalis, neonatal herpes; Latent in sacral ganglia; transmitted by sex contact, perinatally
VZV
chickenpox, shingles, encephalitis, pneumonia; latent in dorsal root or trigeminal ganglia; most common complication of shingles is post-herpetic neuralgia; transmitted by resp secretion
EBV
mono (fever, hepatosplenomegaly, pharyngitis, and lymphadenopathy, esp posterior cervical lymphadenopathy); transmitted by resp secretions and saliva; infects B cells through CD21; atypical lymphocytes seen on peripheral blood smear are not infected B cells but rather reactive T cells; detect by monospot test (heterophile antiboides); assoc with lymphomas and nasopharyngeal carcinoma
CMV
congenital infection, mono (but negative monospot test), pneumonia, retinitis; infected cells have characteristic “owl eye” inclusions; latent in mononuclear cells; transmitted congenitally and by transfusion, sex contact, saliva, urine, transplant
HHV-6/HHV-7
roseola; high fevers for several days that can cause seizures, followed by a diffuse macular rash; transmitted by saliva
HHV-8
Kaposi sarcoma (neoplasm of endothelial cells); seen in HIV/AIDS and transplant pts; dark/violaceous plaques or nodules representing vascular proliferations; cal also affect GI tract and lungs; transmitted by sexual contact
HSV indentification
Viral cx for skin/genitalia; CSF PCR for herpes encephalitis; Tzanck test (smear of opened kin vesicle to detect multinuc giant cells commonly seen in HSV-1, HSV-2 and VZV infection); intranuclear inclusions also seen with HSV-1, HSV-2, VZV
rotavirus
RNA virus; numbe r1 cause of fatal diarrhea in kids
coltivirus
RNA; colorado tick fever
PicoRNAviruses
poliovirus, echovirus, rhinovirus, coxsackievirus, HAV
echovirus
aseptic meningitis
rhinovirus
common cold
coxsackievirus
aseptic meningitis, herpangina (mouth blisters, fever); hand, foot and mouth disease; myocarditis and pericarditis
norovirus
viral gastroenteritis
what are the flaviviruses
hep C virus, yellow fever, dengue, st. louis encephalitis, west nile virus
coronavirus
common cold and SARS
orthomyxovirus
influenza virus
paramyxoviruses
paraflu (croup), RSV (bronchiolitis in babies, treat with ribavirin); measles; mumps
rhinovirus
a picoRNAvirus; nonenveloped RNA virus; cause of common cold; over 100 seologic types; acid labile (destroyed by stomach acid, therefore does not infect the GI tract, unlike other picornavirses)
yellow fever virus
a flavivirus (also an arbovirus) transmitted by Aedes mosquitoes; sx are igh fever, block omitus, and jaundice. May see Councilman bodies (eosinophilic apoptotic globules) on liver bx
rotavirus
infantile gastroenteritis; segmented dsRNA virus; acute diarrhea in the winter (esp day care center); villous destruction with atrophy leads to decreased absorption of sodium and loss of potassium; CDC recommends routine vaccination of all infants
influenza viruses
orthomyxoviruses; enveloped, neg ssRNA viruese with 8-segment genome; contains hemagluttin to promote viral entry and neuraminidase to promote progeny virion release
genetic shift/antigenic shift
causes pandemics; reassortment of viral genome segments, such as when segments of human flu A virus reassort with swine flu A virus
genetic drift/antigenic drift
causes epidemics; mino (antigenic dift) changes based on random mutation in hemagluttinin or neuraminase genes
rubella virus
a togavirus; causes rubella (aka german measles); fever, post-auricular and other lymphadenopathy, arthralgias, and fine rash; causes mild disease in children but serious congenital disease (TORCH infxn)
congenital rubella findings
blueberry muffin baby, indicative of extramedullary hematopoesis
rubella rash in a kid
fine, confluent macules that start on the face and spread centrifugally to involve the trunk and extremities
paramyxoviruses
usually affects kids; paraflu (croup), mumps, measles, RSV (bronchioltis, pneumonia); all contain surface F (fusion) protein, which causes resp epithelial cells to fuse and form multinuc giant cells; Palivizumab (monoclonal antibody against F protein) prevents PNA caused by RSV in premature infants
Croup
aka acute laryngotracheobronchitis; caused by paraflu; barking cough, inspiratory stridor; narrowing of upper trachea and subglottis leads to steeple sign on Xray; severe croup can result in pulsus paradoxus 2/2 upper airway obstruction
measles
rubeola virus; fever, cough, coryza, and conjunctivitis then eventually Koplik spots, followed by a maculopap rash that starts at the head/neck and spreads down; Lymphadenitis with Warthin-Finkeldey giant cellsin a background of paracortical hyperplasia; subacute sclerosing panencephalitis, occuring years later; encephalitis; giant cell pneumonia are possible sequelae
koplik spots
bright red sports with blue/white center on buccal mucosa that precedes the measles rash by 1-2 days
Vit A supplementation in measles
can reduce mortality in infants with malnutrition in kids who get measles
mump’s virus
uncommon, due to MMR vaccine; symptoms are parotitis, orchitis, and aseptic meningitis; can cause sterility (esp after puberty)
rabies virus
bullet-shaped virus; Negri bodies commonly found in purkinje cells of cerebellum na din hippocampal neurons; rabies has long incubation period (weeks to months) before sx onset; travels to the CNS by migrating in a retrograde fashion up nerve axons after binding to ACh receptors; disease progresses from fever to agitation, photophobia, hydrophobia, hypersalivation to paralysis and coma to death; post exposure prophylaxis is wound-cleaning plus immuniz with killed vaccine and rabies immunoglobulin; most commonly from bat, racoon, and skunk bites
ebola virus
filovirus that targets endothelial cells, phagocytes, hepatocytes; abrupt onset of flu-like sx, d/v, fever, myalgias; con progress to DIC, diffuse hemorrhage, shock; high mortality rate, no definitive treatment; supportive care
Hep A virus
RNA picoRNAvirus; fecal-oral; no HCC risk; usually asymptomatic
Hep B virus
DNA hepadnavirus; parenteral, sexual, perinatal transmission; yes HCC risk
Hep C virus
RNA flavivirus; primarily blood transmission (IVDU), HCC risk
Hep D virus
RNA delta virus; parenteral, sexual, perinatal transmission (just like Hep B); dependent on Hep B
Hep E virus
RNA hepevirus; fecal-oral transmission, esp waterborne; high mortality in pregnant women
Signs and sx of all hepatitis viruses
fever, jaundice, increased AST and ALT; may see Councilman bodies (eosinophilic apoptotic globules) on liver bx
HBeAg
A second, different antigenic determinant in the HBV core (aside form HBcAg) that indicates active viral replication and therefore high transmissibility
Anti-Hbe
antibdy to HBeAg; indicates low transmissibility
ALT and AST in viral versus alcoholic hepatitis
in viral, ALT>AST; in alcoholic, AST>ALT
important diagnostic test in the incubation period
HBsAg
important test in the prodrome or acute disease
HBsAg and anti-HBc
diagnostic test in early convalescence
anti-HBc
diagnostic test in late convalescence
Anti-HBs and anti-HBc
What can you detect in the acute hep B infection?
HBsAg and HBeAg and IgM of anti-HBc
what can you detect in the “window” period?
HBeAg and anti-HBc IgM
what can you detect in the chronic HBV with high infectivity?
HBeAg, HBsAg, ant-HBc IgGi
what can you detect in chronic HBV with low infectivity?
HBsAg, anti-Hbe, and anti-HBc IgG
what can you detect in recovery period
anti-HBs, anti-Hbe, anti-HBc IgG
what can you detect in the immunized patient?
anti-HBs
structure of HIV
diploid genome (2 molecules of RNA); structural genes are gp120 (attachment to host CD4 T cells) and gp41 (fusion and entry) and p24 (capsid protein) and pol (reverse transcriptase, aspartate protase, integrase); virus binds CD4 as well as coreceptor, either CCR5 on macrophages (early infxn) or CXCR4 on T cells (late infection)
if a patient has a homozygous versus heterozygous CCR5 mutation
homozyg gives you immunity; heterozyg gives you slower course of disease
HIV dx
first do ELISA; if pos, confirm by Western blot; both of these tests look for antibodies to viral proteins, so are often falsely neg in the first 1-2 mos of infxn and falsely pos initially in babies born to infected mothers (anti-gp120 crosses placenta)
AIDS diagnosis alternative
CD4 percentage less than 14%
Opportunistic infections in patients with CD4 count less than 500
candida (oral thrush), EBV (oral hairy leukoplakia), bartonella henselae (bacillary angiomatosis), HHV-8 (Kaposi sarcoma), Cryptosporidium (chronic, watery diarrhea), HPV (squamous cell carcinoma, commonly of anus or cervix
Opportunistic infections in patients with CD4 count less than 200
toxoplasma (brain abscess), HIV dementia, JC virus reactivation (PML), PCP pneumonia
Opportunistic infections in patients with CD4 count less than 100
aspergillus (hemoptysis, pleuritic pain), crytpococcus neoformans (meningitis), cadida albicans (esophagitis), CMV (retinits, esophagitis, colitis, pneumonitis, encephalitis), EBV (B cell lymphoma), histoplasma (fever, weight loss, cough, vomitting, diarrhea), MAC (nonspec systemic sx or focal lymphadenitis
Prions
conversion of normal protein to a beta pleated form, which is transmissible via CNS-related tissue (iatrogenic CJD) or food contaminated by BSE-infected animal products; resistant to standard sterilizing procedures, including autoclaving; leads to spongiform encephalopathy and dementia, ataxia, and death
Creutzfeldt-Jakob disease
rapidly progressive dementia, typically sporadic (some familial forms)
Bovine spongiform encephalopathy (BSE)
also known as mad cow disease
Kuru
acquired prion disease noted in tribal populations practicing human cannibalism
