Flashcards in IAH Deck (207):
What is the plaque forming assay?
tissue culture assay for quantifying infectious virus
What is a focus assay?
Counting the areas where cells overgrow
What are the components of virion particle?
genome, enzmes, auxialry protein, structural proteins, attachment proteins, fusion proteins, membrane
What is the physiology of picornavirus?
icosahedral, ssRNA+, no lipid envelope, no tegmentum, pH stability: enterovirus ph3-9
rhino virus only ph6+
Polio infection vs. disease?
most were innapparent (asymptomatic)
mild illness-minor febrile illness
only 0.1-2% resulted in paralytic poliomyeltitis:
How was picornavirus diagnosed?
serologic, PCR, virus isolation from CSF, stool specimens and throat washing
Polio had three major epidemiological phases?
virus encountered at early age, high rate of sublinical infections, encounter at maternal antibodies
late 1800s, encounter virus at later age, bc of hygeine, increased paralytic incidence
few cases, all cases related to virus
Piolovirus produces how many proteins?
one protein, causes self limited proteases
How does poliovirus inject its +RNA genome into it?
injected after endocytosis, by utilizing hte capsid as an injection system
What is the physiology of adenovirus?
latent virus in adenoides and tonsils, 51 serotypes, causes gastrointestinal or respiratory disease,
What is adenovirus more dangerous in?
children and immunocompromised
How does adenovirus attach and entry?
viral surfing by attaching to myosin, enters through clathrin mediated endocytosis, viral fusion pore control
How is adenovirus shed from epithelial cells?
Enters throug apical end, shed on the basal side, and hte virus penton spike fiber disrupts adhesion gap junction to allow it back into the lumen
How do you quantify infectious virus?
focus forming assay
single-step growth curve
What are the basic steps in a viral life cycle?
attachment, penetration, uncoating, synthesis of components (synthesis of mRNA, translation of viral proteins, genomre replication),
assembly of viral components
What is virion attachment?
for both naked and envelopoed virus, a viral surface protein recognizes a receptor on the target cell
What is the receptor fro HIV?
Human CD4 on t cells
What is the receptor on cell for EBV?
Human complement receptor CD21
What is the receptor on cell for Rhinovirus?
What is the receptor on the cell for Influenza virus?
How do viruses cause disease?
Virus destruction of infected cells
viral modification of infected cell function
immune and inflammatory responses to virus infection
-immune-mediated damage or destruction
combination of several factors
What innate response from host defense is responsible for viral combat?
soluble mediators (IFNs, cyokines, chemokines; antiviral response within infected cell; make surrounding cells resistant to infection, recruit effector cells)
What is the humoral adaptive response is sued to combat viral infection?
neutralizing antibody: block attachment or entry
complement fixing antibody: lyse virions or infected cells
What is the cell-mediated adaptive response to combat viral infection?
MHC presentation of viral peptides killing of virus-infected cells by cytotoxic T cells
What are the characteristics of chronic virus infection?
Initial steps of infection similar to accute; however virus is not cleared. Initial robust immune response is subdued to prevent immunopathology; immune response of host set to a higher activation state overall
What is hte definition of a latent virus infection?
a viral cycle chaaracterized by minimal if any expression of a subset of viral genes and absence of lytic replication and infectious virion production
What is the prototype of latent virus infection?
What are the innate immunity to viral infection?
Patterns by PRRs
Type 1 IFN secretion
cytokines -- IL1, TNFalpha
NK cells- direct killing of virus-infected cells by NK cells and NK cell are a huge source of IFNgamma
What are the order of immune responses for innate reaction to innate immune response?
Production of IFNalpha, IFNbeta, TNFalpha, IL12 early 2 day peak
NK cell mediated killing 3 day peak
T cell medaited peak 6 to 10 days
What is exogenous IFNalpha used to treat?
chronic Hep C
tx melanoma, hairy cell leukemia, chronic myelogenous leukemia, Kaposi's sarcoma
What is exogenous IFN Beta used to treat?
used in treaatment of MS
Why is exogenous IFNgamma not used to treat disease?
limited clinical usefulness but side effects limit it's ability
What is PKR?
induced by IFN, protein kinase R
binds to ds RNA and becomes autophosphorylates; phosphorylates eIF-2alpha
What is OAS?
2'-5' Oligoadenylate synthetase it is also induced by IFN
catalyzes synthesis of oligo adenlyate and activates RNAse L- endoribonuclease
IFNalpha and IFNbeta induce the anti-viral state which leads to waht?
increase surface class 1MHC
increased NK cells
decrease viral protein synthesis
What is the role of TNF?
tumor necrosis factor; a pyrogen which can induce fever
produced by activated macrophages, cD4 T cells and NK cells
induces death signaling
What is the role of IL1beta?
a pyrogen-can induce fever
major pro inflammatory; produced and secreted by activated macrophages
What is IL6?
major pro-inflammatory cytokine
What is the role of NK cells?
kill targets after assessing the balance between inhibitory signals from class I molecules
activating signals from NK activating ligands
How are infected cells induced to undergo apoptosis?
from within; by internal factors and frm outside by Fas or TNFalpha, NK cells
What is the role of viral IFN-GammaR or viral IFNalpha/betaR?
blocks binding of IFN's and is encoded by poxviruses
How does Adenovirus inhibit PKR?
encodes its own structured RNA and inhbitis activation by dsRNA
How does poxvirus counter PKR activation?
encodes dsRNA binding proteins that sequester the dsRNA and prevent PKR activation
What cancer does hepatitis B and Hepatitis C cause?
What cancers do EBV cause?
lymphoma and nasopharyngeal carcinoma
What cancer does HHV8 cause?
kaposi's sarcoma KSHV
What cancer does HTLV1 cause?
adult T cell leukemia
What cancer does HPV cause?
cervical cancer; head and neck cancer
What patient population are virally caused cancers occurng
What does merkel cell polyoma virus cause?
merkel cell carcinoma a aggressive skin cancer in elder and immunosuppressed patients
What is the structure of papillomavirus?
member of paovavirus
infect cutaneous and mucosal epithelia
small circular double-stranded DNA genome
What proteins does the HPV genome encode?
virus encodes early and late genes?
E1 adn E2 mediate the replication and transcription of viral DNA
E4 disrupts cytokeratins to facilitate virus egress
L1 and L2 compose the capside
What are E5, 6, and 7 doing that is associated with onocogenesis?
E5-stim constitutive growth factor receptor signaling
E6 and E7 neutralizes the major brakes that regulate the cell cycle p53 and Rb
What HPV protein neutralizes p53 and Rb to uncouple cell division?
E6 and E7
What HPV proteins stimulate growth factor receptor signaling?
How does replication of HPV work?
early gene expression in basal layers
late gene expression in spinous and graunlar layer
virion assembled and released in cornified layer
Where is HPV virion assembled and released?
the cornified and granular layer
Where is late gene expression and viral genome amplifaction occuring in HPV?
granular and spinosis layer
Where is the early gene expression E1, E2, E6 and E7 occuring?
basal and spinous level of HPV
At what level does HPV initially infect,
How does HPV E7 regulate Rb?
binds Rb and targets it for degradation so prevents it blocking the progression to S phase
What inappropiate entry into the cell cycle can activate p53 protein?
Induces production of Cdk/cyclin inhibitors and stops the cell cycle
What is the role of E6 protein of papillomavirus?
recruits a ubiquitin ligase that targets p53 for degradation and prevents it from blocking progression to S phase or inducing apoptosis
also induces the expression of telomerase
What is the role of a pap smear?
cytological evidence of diplasia or neoplasia; detection of koliocytotic cells which are rounded and appear in clumps
What is the role of hybrid capture assay?
used for detection, strain analysis, and quantification of HPV DNA
What is the virion structure and composition of retroviruses?
env protein is hte envelope
group specific antigens (gag)
Capid core is made of Matrix, Capsid, Nucleocapsid, protease
What are the 3 groups of proteins in a retroviral genomic RNA?
gag, pol and env
What does R stand for in retrovirus?
repeat on both ends of genome
What is the gag gene?
encodes the Matrix, capsid, nucleocapsid, and protease
What is the polymerase gene (pol)?
encodes reverse transcriptaseand integrase which are made as an extended polyprotein
What is the envelope gene?
encodes the env protein, which is made as a precursor and gets cleaved into different domains
Complex retrovirus HIV organized how?
similar to simple retrovirus except numerous adtional genes
How are the accessory proteins mRNA's generated in complex retrovirus?
complex alternative splicing
consists of a number steps seperated into two phases by the integration step
How does adsorption of HIV work?
HIV receptor is CD4/CCR5;
How does HIV penetrate and uncoat in human cells?
viral envelope fuses with cell membrane either at the cell surface or in endosomes after endocytosis
How does HIV uncoat in human cells?
genomic RNA is only partially uncoated, remains in a protein 'particle' particle in the cytoplasm
some of the gag proteins remian associated with incoming genomic RNA
How does reverse transcription work with HIV?
process of converting ssRNA to dsDNA; integrated DNA called provirus
How does integration work with HIV?
carried out by the integrase protein which enters cell with the virus and remains associated with the dsDNA
How does proviral transcription work in HIV?
major role of the LTR is to direct synthesis of viral RNA
organization of the LTR- U3 contains binding sites for cellular transcription factors acquired for high level RNA synthesis
How does RNA processing work in HIV?
as pol II transcripts all viral RNAs are polyadenylated, some must be spliced to generate teh env mRNA but a large portion must remain full length
How does translation occur in HIV?
most abundant protein is gag and gag-pol, made as a polyproteins from full length mRNA
What is the most abundant protein in HIV?
gag and gag-pol; initiates at an AUG start codon and ends at a stop codon
What does env protein is made from what?
spiced mRNA on ER-bound robosomes, moves through ER-golgi is inserted into plasma membrane
How does virion assembly and budding wokr in HIV?
how is the viral unspliced RNA selected for packaging instead of env spliced RNA or any other RNA
packaging: requires a psi signal; spicing removes psi signal
budding: viral gag and gag-pol polyproteins recruit RNA
maturation: as mentioned above proteolysis of gag and gag-pol by PR occurs after budding
How does retroviral mediated oncogenesis?
non-transforming retrovirus- non-acute or slow tumor viruses; tumors are caused by activation of inactivation of host genes
How does transforming retroviruses "acute" occur?
infections cause tumors within week; viruses harbor a mutated copy of a cellular gene involved in growth control
What six accessory proteins of HIV are required for replication?
Vif, Vpr, Vpu, Nef, Tat, Rev
What are the two regulatory HIV protein?
Tat and Rev
What is the HIV protein absolutely required for transcription?
Tat- transactivator of transcription
What does Rev do?
regulator of virion expression allows structural gene expression by promoting transport of unspliced RNA from nucleus to cytoplasm
What are restriction factors fo HIV?
viral proteins that overcome cellular defenses
What are teh two restriction factors of HIV?
Vif and Vpu
What does Vif of HIV do?
virion infectivity factor- causes a cellular antiviral protein to be degraded: otherwise is incorporated into new virion where block RT in the next cell by inducing massive viral dsDNA
What does vpu do in HIV?
promotes virion release from cell by inhibitin a host protien tetherin
What are the two co-receptors, which HIV bind one or the other of?
CCR5 and CXCR4
What are the presentl available drugs for HIV?
What is HAART?
highly active anti-retroviral therapy
considerablesuccess of cocktails triple terapies
long-term pts experience toxicity
Can dendritic cells become infected?
no can bind HIV but not productively infected; can assist in dissemination
What are the HIV tropisms?
M and T tropic
M infect macrophages in lab
T infect T lines in lab
What is the basis for starin tropisms?
env sequence of different HIV types
Which strain of HIV is most concerning?
M tropic bc source of person to person transmission
What is the mutation that protects against HIV infection?
32 bp deletion in CCR5; double mutation leads to no HIV binding
Co-receptor engagements triggers what?
a snapback of N and C terminal helices regions of gp41 which brings membranes together and fuses them
What are the indirect effects of HIV?
immune resposne kills infected cells, soluble gp 120 may bind uninfected cells and now susceptble to ADCC
What are the ways to diagnose HIV?
Real time RT-PCR
What is the half life of infected memtory T cells?
greater than 5 years meaning you would require over 75 years to clear this department
what are some complications of influenza virus infection?
primary viral pneumonia
secondary bacterial pneuomnia
myositis and cardiac involvement
How is influenza diagnosed?
rapid antigen capture, detects nucleoprotein
Adenoviruses cause what type of disease?
A very wide variety, GI, UTI, conjunctivitis, respiratory, lymphoid infection
What usually kills people when infected by measels?
What does mumps infect?
pancreas, parotid gland, ovaries, testes other glands can cause neurological issues
What is the host for mumps?
Rubella virus is what type of virus?
What is the major concern from Rubella?
neonates younger than 20 weeks who are inected can result in congenital defects
What are the prominent clinical finding in congenital Rubella syndrome?
cataracts and other ocular defects, heart defects, death in first year
What is parvovirus B19?
single stranded DNA virus, icosahedral non-enveloped virus; dependent on host DNA replication functions
What is bocavirus?
newly discovered parvovirus responsible for GI and respiratory infections
Parvovirus infects what?
infects actively replicating red blood cell progenitors in bone marrow (viremia)
What are the clinical features of Parvovirus B19?
erytha infectiosum, bright red cheeks, maculopapular rash, circulating immune complexes
What are complications of B19 infection?
in chronic hemolytic anemia pts virus can cause aplastic crisus
when transmitted to fetus can cause still births and generalized edema
What viruses are transmitted by fecal/oral transmission in childhood?
rotavirus and norovirus
Rotavirus is what structure?
11 double stranded RNA segments with no envelope but a 3 layer capsid
group A most common cause of human disease
can have reassortment
What is the most imoprtant non-structural protein of hte rotavirus?
NSP4, an extotoxin that increases intracellular calcium leading to diarrhea due to disruption of tight junctions
What virus causes the largest number of sever diarrhea in children?/hospitalizations
What is teh concern with rotavirus vaccines?
intussusception of intestines
What is norovirus causing?
major cause of acute gastroenteritis in school-aged children and adults
What is the most common cause of foodeborne gastroentertiis in teh untied states?
What are the symptoms of hand and foot disease?
mild fever, sore throat, fatigue, vesicular lesions on hand feet and inside mouth
What is the host of the hantavirus?
What is the disease associated with hantavirus?
hantavirus-induced pulmonary syndrome
What are two arthopod-borne viruses that are emerging?
West Nile and Dengue
three general type of disease fever
What is Dengue spread by?
mosquito, climate expaneded host range of vector
What allowed west nile to spread?
introduction of infected vector to new range
When was the first case of West Nile in the United states discovered?
What is the natural resevoir of West Nile virus?
birds; only crows and Jays are affected negatively
Horse or humans are what for west nile virus?
usually dead end host, viremia is hard for it to achieve
What are the clinical features of west nile fever?
fever, fatigue, swollen lymph glands, headache, skin rash, eye pain
Severe disease in immunocompromised:
fever, ataxia, myelitis, GI sympoms, seizures, AMS
How is WNV diagnosed?
relies on hihg index of clinical suspicion; usually fall greatest number of human cases`
What is the first infection of dengeu fever described as?
breakbone fever, fever, muslce bone pain, joint pain
not fatal have protection against reinfection with same serotype
What is the problem with getting a second infection of Dengue fever with different serotype?
antibodies that don't properly neutralize increase infections of Monocytes and macrophages, release inflammatory and can cause hemorrhagic fever
What is the diagnosis of Dengue done?
ELISA to detect antibodies
using touriquette will result in broken vessels
What is the role of monkeypox?
relatively rare disease occuing mostly in Africa; virus a member of Poxvirus
first human case identified in 1970 not generally fatal
What are the symptoms of monkeypox?
incubation of 12 days
fever, headache, muscle aches, and backache
emergence is due to change in behavior and movemnt of virus
What are the symptoms of hantavirus?
fever, hemorrhage, 5-10%, headache, acute renal failure
When did hantavirus become aproblem?
during the korean war
Dengue virus is what type of virus?
What are causes of Dengue shock syndrome?
occurs when individual with antibodies agianst one serotype is infected with another serotype
How is Dengue hemorrhagic fever diagnosed?
ELISA to detect antibodies to determine antibodies along witha positive tourniquet test
What is the cause of monkeypox?
relatively rare disease occuring in africa; small pox simlar but milder than smallpox
Monkeypox has what symptoms?
fever, headache, muscle ache, lymph nodes swollen, scab
what leads to developing and emergind diseases?
Change in demographics increased urban centers often with poor sanitation
increasd interntaional trade
increased international travel
Change in behaveior
-antibiotic, IV drug use, Promiscuous sex
Changes in environmen
change in tech
change in virust
What are the two emergin arborviruses?
west nile and dengue virus
When was west nile released into north america?
What ar ethe features of severe west nile virus?
menigitis, encephalitis fever atazia myelitis GI symptoms seizures change in mental status
How is WNV diagnosed?
relies on high index of clinical suspicion
consider WNV in adults greater than 50 years of age or older
local WNV activity
vaccine availbe for horses
What are the gamma herpes viruses?
What are the Beta herpes viruses?
What are the alpha herpes viruses?
varicella zoster virus
Herpes simplex virus
What occurs during the latent infection of the herpes virus?
Same strain of herpesvirus persists within the same host; Maintains itself as an episome
HSV-1 and 2 are latent at what points?
HSV-1 -- trigeminal ganglia
HSV-2 -- sacral ganglia
Latency associated transcripts do what?
these are NEVER translated into protein and function to repress HSV gene expression by an unknown mechanism
Unknown stimuli trigger viral reactivation ccurs how?
few viral capsids are subjected to anterograde transport with mature virions produced around the site of innoculation-- reinfection of epithelial cells--lesion--spread: reccurent infection
Reinfection of a seropositive individual with a different strain of HSV is possible but uncommon, this is what?
an exogenous reinfection
What is the mechanism of action of acyclovir?
a suicide inhibitor: competes with dGTP for viral DNA polymerase
What is neonatal herpes?
inoculation during birth
inoculation during pregnancy results in multiple birth defects
CNS is commonly affected
Disease usually manifests within days of life
mortality is high
survivors experience a very high rate of neurological abnormalities
What CMV in healthy adults presented?
mild mononucleosis or cold-like symptoms
Asymptomatic in healthy adults
What are the leading causes of congenital birth defects?
TOxoplasmosis, Rubella, Cytomegalovirus, Herpes simplex
mild to severe mental retardation, deafness, death
What becomes symptomatic upon immunosuppression?
chemotherapy, organ transplant, and HIV
What long term persisten infection is associated with CMV?
What are basic characteristics of CMV?
230 kbp double stranded DNA genome
-stages of gene expression; immediate early, early and late
expresses 750different proteins
enocdes its own DNA replication machinery
Cytomegalovirus transmission occurs how?
Direct contact with virus-containing secretions
inoculation onto a mucosal site
shedding with or without symptoms
What is the immune response to CMV?
Macrophage, interferon and NK cells control but insufficient to control
humoral doesn't play a role in clearance but limit reinfection or reactivation
cell mediated immune response is important up to 10%
What are the symptoms of CMV in healthy adults and children?
mild disease, often unapparent
fever, fatigue, sore throat headache
liver function abnormalities
How is CMV diagnosed?
IgM or IgG although can be difficult to tell
owl's eye cells in urine or other tissues
culture virus from clinical material
How is CMV treated?
gangiclovir or valganciclovir
activated with phosphorylation by viral kinase inhibits viral DNA pol
acyclovir is NOT effective
congenital CMV does what?
cause birth defects
first semester trimester infections have worse outcomes
poor outcomes if symptoms at birth
-small size at birth
hearing and vision loss
Who is CMV infection a problem in?
pts undergoing chemo
What is the rate of seropositivity of EBV?
95% or greater by early 20s world wide
a lot of asymptomatic infections
What are cahracteristics of EBV?
immediate early, early and late gene expression
replication in B cells or epithelial cells
latent infection in memory B cells
stimulate and immortalize B cells
What are the stages of EBV disseminationa nd latency?
transmission by blood and saliva
latency 3 occurs in proliferating B cells results in mononucleosis, post transplant lymphoproliferative disorder
latency type 1/2-viral antigens; can lead to Burkitt's, Hodgkin lymphomas, nasopharyngeal carcinoma
What are the EBV associated lymphomas?
Burkitt's lymphoma- b cell lymphoma of jaw and face
Nasopharyngeal epithalial carcinoma-EBV DNA in epithelial tumor cells
B cell lymphomas-Hodgkin and non-hodgkin
Immunosuppressed pts and transplant pts
What are the symptoms of EBV-mediated infectious mononucleosis?
5-20% of B cells infected
fever, malaise, lymphadenopathy, exudative pharyngitis, splenomegaly
symptoms due to T cell response
asymptomatic in young chilren
What is the disease post-transplant lymphoproliferative disorder?
EBV-mediate B cell proliferative disease
-immunosuppressive tx activates infection
-incidence 1-33% transplants depending on organ
within first year after transplant
donor B cells or reactivation in recipient
low risk if graft contains donor t cells
POOR PROGNOSIS 40-70% mortality
anti-CD20 antibodies eliminate B cells
How is EBV diagnsed?
-test for heterophile antibodies by agglutination of animal red blood cells
PTLD-fluorescent in situ hybridization to EBER RNA in neoplastic cells
What is the is HHV-8?
Kaposis sarcoma herpes virus; causes Kaposi sarcoma, primary effusion lymphoma and multicentric Castlleman disease
replication occurs in CD19 peripheral B cells
What is the hepatitis A virus?
single serotype worldwide
fecal oral transmission
acute disease and asymptomatic infection
no chronic infecction
How often is jaundice causeed by Hepatitis A?
under 6 less than 10 percent
over 14 yrs 70-80%
What are the complications associatedd with Hepatitis A?
Who is the hepatitis A vaccine recommended for?
those traveling to areas with high incidence
ppl with chronic liver disease
ppl working with HAV
Where are the hepatitis E outbreaks occuring?
US cases have travelt o HEV endemic areas and most outbreaks are associated with fecally contaminated drinking water
How does the outcome of hepatitis B infection change by age at infection?
chronic infections are the greatest in those infected at birth
symptomatic fnfections occur more regulary after about 4 years of age
What is the mechanism of hepadnavirus?
enveloped virus is bidning to sodium/bile acid contransporter
circular DNA genome partially double-sranded genome with DNA syntehsis occuring to form fully ds DNA and that goes to nucleus
mRNA "reverse-transcribedd" to ssDNA, DNA made partially ds
DNA can integrate into chromosome and remain in cell
HBV infected cell produce what two things?
infectious virus as well as non infectious HbsAg particles; antigen without DNA
What are the normal causes for initial infection by HBV?
so IDU, sex, neonatal, breast feeding
What are the symptoms of hepB?
What are the normal clinical outcomes for HBV infection of adults?
90% have full resolution
9% have HbsAg+ for greater than 6 motnhs ; 50% of those resolve the rest have some osrt of chronic state which can result in carcinoma or cirrhosis
1% fulminant hepatitis
What is hepatitis delta?
viroid that can only grow in hepatits B infected cells
small RNA copied by host RNA pol II, catalytically active ribozyme that processes itself
encodes 1 antigen becomes packaged in Hep B sAg
What are the clinical features of Hepatitis D?
coinfection; sever acute disease and low risk of chronic infection
superinfections(subsequent to HBV) usualy develop chronic HDV and high risk of sever chronic liver disease
What is the treatment of HBV?
vaccination is key to prevent infection of high-risk individuals and infants
polymerase inhibitors, nucleoside analogs, IFN-alpha; aka antivirals
new approaches silence HBV expression during chronic infection
Hepatitis C is what structure?
flavivirus; pos strand, RNA virus. Enveloped virions
9 kB genome; 10 proteins, involves proteolytic processing
encodes multiple immunomodulators
liver damage primarily due to immunopathology
hihg incidence of chronic and asymptomatic infections
assoicated with hepatic carcinoma
What is the viral life cycle of hepatitis C?
hepatocyte specific- basis for developing therapies
intimate relationship with intracellular lipids and membranes
RNA replication; IRES-mediated translation
membrane associated RNA replication
maturation and release
What are the most common sources of Hep C infection?
What are teh clinical outcomes of HCV infection of Adults?
85% persistent infection
--6% liver failure
--4% hepatocellualr carcinoma
Why does HCV lead to a high incidence of carcinoma?
HCV core proteins interact and regulate many tumor suppressors; induce steatosiss
envelope protein E2 inhbiits NK cells
non-structural proein NS3 can enhance cell growth
NS5A enhances cell growth and prevents apoptosis
How does the IL28B gene playa keyaoutcome in HCV infectin?
it encodes IFN-gamma and a polymorphism has a strong impact on teh response to IFN therapy as well as natural clearance; the primary genotye in the US has more trouble clearing