Virus Lectures Flashcards
Childhood viral infections
measles, respiratory syncytial virus, varicella zoster, poliovirus, rotavirus
(-)ssRNA viruses
measles, RSV, hep delta, rabies, influenza
dsRNA viruses
rotavirus
dsDNA viruses
chicken pox, hep B, adenovirus, HSV1 and 2, cytomegalovirus, EBV, HPV
non-enveloped viruses
poliovirus, rotavirus, hep A, E, adenovirus, rhinovirus, HPV
Measles and RSV replication
buds from cell surface, cytoplasm replication, fusion creates syncytia
- RSV infects ciliated cells on respiratory tract; replication limited to respiratory tract
Measles complications
- immune suppression because interference with CD46 and signaling lymphocyte activation molecules (CD46)
- opportunistic infections arise
- blindness in vit A deficient children
- acute disseminated encephalomyelitis (demyelinating disease)
- subacute sclerosing panencephalitis
Measles vaccination/treatment
vaccine = live attenuate; life long immunity
- vit A reduce severity
- NO antivirals
RSV prevention
ribavirin and passive immunoprophylaxis (palivizumab -> targets F protein)
Varicella zoster replication
replicates in nucleus of active cell; resides in resting cell (ex: neuron) as latent infection (circular genome); infects neighboring cells first
Chicken pox vaccination/antivirals
life-long immunity; line attenuated vaccine
antivirals = acyclovir; interferes with genome replication but cannot eliminate latent virus and does not prevent infection of cells
Poliovirus replication
creates pore in cell membrane, genome serves as mRNA and replicates in cell cytoplasm
- primary replication in peyer’s patches of small intestine (minor viremia), secondary replication (major viremia)
CNS damage with poliovirus
due to viral replication in gray matter of brain and spinal cord
- limb paralysis from ant horn cell damage
- respiratory paralysis from damage to medulla oblongata
poliovirus prevention
vaccination
- Salk = killed
- sabin = live attenuated
Rotavirus replication
disrupt membrane (genome never exposed), dump nucleocapsid into cytoplasm and replicate in cell
how is rotavirus diagnosed?
antigens in stool
Rotavirus prevention
vaccines- rotateq (2,4,6 mo) and rotarix (2, 4 mo)
- No antivirals
- proper hygiene
- treat by oral rehydration
Hepatitis viruses transmission
fecal - oral = HAV, HEV
sexual = HAV, HBV, HCV, HDV, HEV
vertical (mother to child) = HBV, HCV, HDV
parental (sharing needles) =HAV, HBV, HCV, HDV, HEV
Which virus has the smallest genome of human viruses?
HBV
HBV biology
not grown in culture, genome has RNA intermediate, cccDNA is used as template for transcription, requires liver specific transcription factors, produce empty particles present in infected people
HBV prevention
vaccine = multiple inoculations, not effective against chronic infection
treatment for chronic = interferon alpha therapy and nucleoside analogs (adefovir, lamivudine, tenogovir)
Which virus requires an active HBV infection?
HDV
HCV biology
- genome passed into cytoplasm
- genome template for translation (missing cap, ribosomes recognize internal ribosome entry sites (IRES)
HCV treatment
ZEPATIER -> on market to treat some genotypes
- no vaccine
Hepatitis infections general symptoms
malaise, anorexia, vomiting, jaundice
HAV prevention
vaccination - HAVrix, VAqta killed/inactivated vaccine
Which hepatitis infection is life threatening for pregnant women?
HEV
Which hepatitis infections can become chronic?
HBV, HCV, HDV
Hepatitis incubation periods shortest to longest
HAV, HEV, HCV, HBV and HDV
Which hepatitis infections can be asymptomatic?
all (HDV is possible)
Which hepatitis infections have long term sequelae?
HBV, HCV, HDV
What is arthropod transmission?
virus transmitted through vectors
- mosquitoes, ticks
reservoirs - birds and small mammals
transmission requires replication in vector
EEE and VEE replication
introduced through bite of infected arthropod, infect cells locally or carried by langerhans cells to LN, replication and release into blood stream, can infect other organs (CNS)
EEE and VEE prevention
vaccine (live = TC-83, inactivated = C-84)
- only provided to at risk military and researchers
- no treatment
- mosquito repellent to prevent
West nile virus prevention
no vaccine or treatment
- mosquito repellent to prevent
Why is the range for EEE and WNV so different?
species associated with diseases habitat ranges are in these areas
Rabies virus biology
- only replicate in cytoplasm
- genome order dictates abundance of transcripts and proteins
- binding of N to RNA triggers genome replication
- frequently produces defective interfering particles
Spread of rabies
replicates locally until finds neurons -> moves passively in axoplasm of peripheral nn to spinal ganglia, spinal cord and brain -> spreads back to periphery highly innervates salivary glands and replicates
Rabies prevention
- vaccine
- post exposure prophylaxis administered immediately for bites that break skin (4 doses), also receive immunoglobulin (RIG)
- vaccination of dogs and animals essential
Which retrovirus does not cause human disease?
spumavirus
What do simple retroviruses encode?
Gag, Pro, Pol, Env genes
Retrovirus replication
attachment -> entry -> reverse transcription (ssRNA genome to dsDNA) -> integration (virus dsDNA into host making provirus) -> transcription from provirus -> translation -> assembly -> release -> maturation (protease activity)
Why is reverse transcription important in retrovirus?
defining feature
- initiates once nucleocapsid is in cytoplasm (need higher levels NTPs present)
- occurs in large complex similar to nucleocapsid
- infection cannot progress without
How is reverse transcription promiscuous between genome copies?
- “silent” when copies are identical
- many recombinations when different genomes in virion
Retrovirus integration
must access nucleus
- during mitosis - requires dividing cells
- importation- can infect non-dividing cells
3’ end processing of dsDNA
attack target DNA, nick created
host repair
What are integration identified oncogenes?
transcription factors, secreted growth factors, growth factor receptors, cell signal transduction pathways
Slow retrovirus disease
effect is like high-level mutagenesis
eventually results in tumorigenesis
cytopathic retrovirus
minority of retroviruses carry cytopathic genes, cause tissue damage directly
acute transforming viruses
induce rapid tumor formation, carry host genes (mitogenic or antiapoptotic), often replication defective because host gene replaces an essential gene
Which HTLV is most often associated with humans?
HLTV-1
HLTV transmission
person to person - mother to child via breastfeeding (endemic areas) - sharing needles - blood transfusions - sexual transmission within host - highly cell associated - primary mode for spread is contact between infected and naive cells
HTLV-1 prevention and treatment
prevention
- no breastfeeding for HTLV-1 pos mothers
- increase screening for blood products
Treatment
- ATLL = lymphoma/leukemia chemotherapy
- HAM/TSP = corticosteroid, interferon yield temporary relief of symptoms
What a worldwide pandemic with significant impact?
HIV; highest in sub-saharan Africa
HIV transmission
sexual, paternal (mainly transfusions), mother to infant
HIV infection
begins virus containing blood of body fluid to a mucosal surface or blood, targets memory T cells (CD4+)
HIV prevention and treatment
prevention - protection during sex - blood screening treatment - antivirals; NRTIs (nucleoside reverse transcriptase inhibitors), protease inhibitors, NNRTI (non NRTI), HAART (highly active antiretroviral therapy -combines 3 of treatment options)
