Lecture 4 part 2 -- herpes, etc Flashcards
explain the envelope, capsid, and genome of herpesviruses
envelope – has an envelope. RICH in glycoproteins
capsid – icosaDELTAhedral
genome – dsDNA virus with a linear genome
what are the 3 subfamilies of the herpesviruses
-alpha
-beta
-gamma
the 3 subfamilies of herpesviruses was determined based on….
their gene structure and site of latent infection
where are herpesviruses replicated and assembled?
in the nucleus
explain the symptoms usually exhibited in herpesviruses (be general)
herpes is a common infection.
usually, benign and asymptomatic but can be serious especially in immunocompromised ppl
where in the body is there significant morbidity if herpesviruses get their
eye, brain, and disseminated infections (spread)
true or false
some herpesviruses have highly specific tissue tropism
true
how are herpes viruses released from the cell?
through lysis, exocytosis, or cell-cell bridges
name the 3 viruses under alpha herpesvirus
HSV-1 (herpes simplex)
HSV-2
Varicella-Zoster virus (VZV) – HHV-3 (chicken pox)
name the viruses under beta herpesvirus
CMV (cytomegalovirus) – HHV-5
Human Herpes virus 6 and 7
name the viruses under gamma herpesvirus
EBV – epstein-barr virus – HHV-5
Kapsi’s Sarcoma-related virus (HHV-8)
HHV3
varicella-zoster virus (chicken pox) (VZV)
ALPHA
HHV 6 and 7
human herpes virus 6 and 7 (BETA)
HHV-4
Epstein-barr virus (EBV)
GAMMA
HHV-5
CMV (cytomegalovirus)
BETA
HHV-8
kapsoi’s sarcoma related virus (gamma)
explain the replication scheme for herpesviruses (how they make protein and more genome)
herpes genome: dsDNA
to make protein:
SAME WAY AS HOST – USES DNA DEPENDENT RNA POLYMERASE THAT IS MADE BY THE HOST to make (+)mRNA. this is then translated to protein on a host ribosome
to make genome: uses VIRAL DNA dependant DNA polymerase to replicate into more dsDNA
which herpesvirus(es) cause mononucleosis
Epstein-barr virus (gamma) - HHV-5
cytomegalovirus (beta) - HHV-4
which virus has a TEGUMENT and what is it
herpesviruses
cluster of proteins that surrounds the nucleocapsid
what is one of the only viruses to use the rolling circle method of replication?
herpesviruses
explain how herpesviruses replicate
their genome (dsDNA) circularizes in the nucleus. the transcription of immediate early genes begins.
alpha proteins are the products of immediate early genes. they stimulate the transcription of early genes.
beta proteins are the products of early genes. they function in DNA replication, yielding CONCATEMERIC DNA which is very long, linear, and multiple genomes.
late genes are transcribes
the product of late genes = gamma genes. they participate in virion assembly
to actually replicate, they use the ROLLING CIRCLE METHOD OF REPLICAITON
Name the primary infection sites for HHV1-4
HHV-1: mucoepithelial cells
HHV-2: mucoepithelial cells
HHV-3: mucoepithelial cells
HHV-4: B cell, oral epithelium
name the latent infection sites for HHV1-4
HHV-1: nerve ganglia
HHV-2: nerve ganglia
HHV-3: nerve ganglia
HHV-4: B lymphocytes
HHV-4- —- HHV-8 are all latent in…..
IMMUNE CELLS
which herpes virus has symptoms like genital and anal lesions, severe neonatal infections, and meningitis?
HHV-2
which herpes virus has symptoms like oral and ocular legions and encephalitis? (inflammation of brain)
HHV-1
Which herpes virus gives the chicken pox with primary infection and shingles virus with reactivation?
HHV-3 (varicella-zoster virus)
which herpes virus gives tumors and some B cell lymphoma?
HHV-8 (kaposi sarcoma)
which herpes virus gives roseola in infants and infections in allograft recipients ?
HHV-6
Which herpes virus gives some cases of roseola?
HHV-7
The genomes of HSV-1 and HSV-2 encode around how many proteins? explain
~80 proteins divided in 2 groups:
-viral replication
–viral DNA polymerase
–scavenging enzymes that create deoxyribonucleotides used for synthesis of new viruses
-other proteins
–attachment glycoproteins
–immune escape proteins
are HSV infections lytic or not lytic?
lytic
HSV infections lyse what 2 types of cells?
epithelial cells and fibroblasts
where are HSV infections latent?
in non-dividing cells. ie: neurons
in latent HSV infections, are early and late genes being expressed?
no— being suppressed by:
-LATs (latency-associated transcripts)
-micro RNAs inhibit gene expression
HSV viruses persist in _____ neurons
explain what is happening
sensory neurons ie: trigeminal nerve
these viruses avoid the host immune response and the person is asymptomatic. TAP is blocked, and they express Fc and complement receptors
reactivation of the herpes virus can occur with systematic infection, fever, stress, or sun exposure
which HHV can affect neonates and is often fatal
HSV-2
cell mediated immunity of the neonates is not fully developed
what are the symptoms of HSV-1
mucocutaneous lesions — cold sores
pharyngitis
eczema
encephalitis
what are the symptoms of HSV-2
genital herpes – affects sacral ganglion
neonatal HSV
chickenpox affects what 3 cells?
epithelial cells, fibroblasts, and T cells
where does HHV-3 (VZV) go latent?
in neurons – dorsal root or cranial root ganglia
what is the primary route of transmission for VSV
inhalation
where does VZV replicate
in mucosal epithelium. cell-cell spread (synctium)
how is HHV-3 spread
by viremia to skin producing regions
what are 3 potential outcomes of HHV-4
epsteinn barr virus
- primary infection – productive and lytic
- latent infection in memory B cells – recurrence when the B cell is activated
- immortalization of B cells–lymphomas
3 fates of the epsteinn-barr virus are: primary infection, latent infection in memory B cells, and immortalization of B cells
explain how each is accomplished
primary infection – lytic and productive. virus binds CR2 receptor on selected epithelial cells and B cells. early and late genes are transcribed and translated
latent infection in memory B cells — recurrence can occur once the B cell is activated. NO EARLY OR LATE GENE EXPRESSION
immortalization of B cells — B cell lymphomas and nasopharyngeal carcinomas
how is HHV-4 transmitted
through shedding virus (saliva)
what component of our immune system is critical for controlling HHV-4
T CELLS
the massive activation of T cells by the proliferation of B cells contributes to symptoms of mono (infectious mononucleosis)
name 3 symptoms of epsteinn barr virus that occur as a result of T cell mediated immunity to control the infection
lymphocytosis – increase in cells with 1 nucleus
swelling of lymph tissue
malaise – general discomfort
what does EBV produce that inhibits the TH1 immune response?
an analog to IL-10 cytokine (a virokine)
which HHV is a dsDNA virus but harbors mRNA transcripts in its capsid?
HHV-5 (cytomegalovirus)
what are the permissive and non permissive cells for HHV 5
permissive – fibroblasts, epithelial cells, granulocytes, macrophages
nonpermissive – lymphocytes, stromal cells, monocytes
HHV-5 favors ___ infections. why?
latent because there is slow replication
–reactivated in immunocompromised individuals
which virus has asymptomatic shedding of the virus in bodily fluids?
HHV-5
cytomegalovirus
for which herpes virus is nearly everyone seropositive in adulthood?
name other characteristics of this virus
HHV-6 – Roseola
replicates in SALIVARY GLANDS
high fever followed by neck and trunk rash
where does HHV-6 go latent?
in CD4 cells and monocytes
–productive infection when T cells are activated
which herpes virus is opportunistic in AIDS patients
HHV-8 Kaposi sarcoma
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