Schein - DNA Viruses Flashcards
Parvoviruses
Smallest pathogenic viruses
- ssDNA
- only pathogen is Parvovirus B-19
- replicates only in dividing cells
- causes fever and rash
- called “fifth disease”
- rash is called erythema infectiosum - it starts by the cheeks and works it’s way down to the trunk and arms.
- can cause spontaneous abortion in pregnant woman and birth defects.
- can cause transient aplastic anemia.
Papovavirus
Named after papilloma, polyoma, simian vacuolating
- replicates in the nucleus because it needs host cell replication machinery
HPV
Replicates in epithelial cells
- viral proteins keep infected cells in the division cycle.
- causes proliferative warts that can lead to cervical cancer.
How does HPV disrupt the cell cycle and cause the. Cell to keep multiplying?
It integrates its DNA into the host DNA and uses the host machinery to make early proteins called E6 and E7.
- E6 will bind to p53 and not allow it to apoptose cells
- E7 will bind to retinoblastoma protein (Rb) and thus Rb will not inhibit E2F (elongation factor) and thus DNA will won’t induce to replicate.
Adenovirus
Also drive infected cells into cell division
- leading cause of tonsillitis, usually in children
- can cause conjunctivitis
Pox virus
Largest DNA virus
- replicates in the cytoplasm because it is larger and has everything it needs.
- brick shaped
- causes smallpox
Smallpox
- transmitted by respiratory secretions
- causes viremia which infects macrophages, which spread it throughout the body.
- causes rash that starts by the face and mouth and then moves to the trunk and body
- all of the pustules will be the same age.
Which virus is brick shaped?
Pox virus / smallpox
What is the morphology of the herpesviruses???
Fried egg appearance
Protein synthesis cascade for herpesviruses
1) virus fuses with host cell membrane
2) virus uncoats
3) virus enters nucleus
4) alpha mRNA is made and shipped out of the nucleus into the cytoplasm
5) alpha proteins are made and brought back into the cell
6) beta mRNA is made and sent outside of the ulcers into the cytoplasm
7) beta proteins are made and brought back inside of cell
8) gamma mRNA is made and sent outside of the nucleus into the cytoplasm.
9) virus can then be packaged and leave the nucleus and then leave the cell.
Which viruses are alpha herpes viruses? Beta? Gamma?
Alpha - HSV1, HSV2, VZV
Beta - CMV, HH6, HH7
Gamma - EBV, HHV8
ALpha herpes
HSV1, HSV2, VZV
- latent in sensory ganglia
- causes cold sores, genital warts, pustules
- rapid spread, short reproductive cycle
Beta Herpes
CMV, HHV6, HHV7
- latent in monocytes
- slow reproductive cycle
Gamma herpes
EBV, HHV8
- latent in lymph tissue
- infection specific to T or B lymphocytes
How do herpes viruses evade the immune system?
- they inhibit production and activity of cytokines by using cytokines homologs to bind receptors
- Decrease MHC Class I activity
- inhibit interferon activity
- block apoptosis
- hinder macrophage activation.
HSV
1 - causes cold sores, inflammatiokkn of the conjunctiva of the eye, and encephalitis in newborns
2 - genial herpes and neonatal herpes
- virus spreads along neurons and lays latent in sensory nerve ganglion
- creates multinuclear giant cells and intra-nuclear inclusion bodies.
- uses LATs to remain latent
Latency-Associated Transcripts (LATs)
Found in latently infected sensor neurons. It is a viral mRNA transcript that is anti-sense to a gene called ICPO. As long as this LAT transcript is on the ICPO, it remains latent.
Varicella-Zoster
Systemic disease that causes a rash that itches.
- lays latent in multiple sensory ganglia.
- rash starts on the trunk and goes to extremities, which is the opposite of smallpox.
- all pustules will not be the same age.
Cytomegalovirus
Betaherpesvirus
Children - asymptomatic
Newborns - salivary gland disease
Adults - mononucleosis-like disease
Has owl-like appearance.
Which virus has an owl-like appearance?
CMV
How is CMV spread?
Contact with infected body fluids
- sexual intercourse
- blood transfusions
- latent in monocytes (and neutrophils)
Epstein-Barr Virus
Gamma Herpes virus
- causes infectious mononucleosis
- associated with burkitt’s lymphoma and nasopharyngeal carcinoma
- spread through saliva through repeated exposure.
- it infects and multiplies in B lymphocytes
Immune response to Epstein Barr virus
- Stimulated B cells will produce “heterophile antibodies” which are indicative of this disease
- increase in activated T cells
Diagnosis of Epstein Barr virus
Downy cells - atypical T cells
Heterophile antibodies
Paul-Bunnell Test (mono spot) - that looks for agglutinate do RBCs
Serology - anti-capsid will be early on and anti-EBV nuclear antigen won’t be for 3-6 weeks post-infection.
Which one of these is single stranded DNA?
Parvovirus
Where does pox virus replicate?
Cytoplasm
- even though ut is a DNA virus, it has everything it needs and can replicate in the cytoplasm.
What is unique about the VZ virus??
All of the pustules will not be the same age
They will start on the trunk and then make their way to the extremities.
Heterophile antibodies
Polyclonal immunoglobulins that are nonspecific but are diagnostic of Epstein Barr
Downy Cells
Activated T cells that are atypical.
Diagnostic of Epstein Barr
In Epstein Barr, which antigens will. Be high. Early and which late?
Early - anti-viral capsid antigen
Late (3-6 weeks after) - anti-EBV viral antigen
What is the link between EBV, Malaria, and Burkitt’s ymphoma
Let’s say that you have EBV already and now you contact malaria. This will cause a decrease in T cells but also will cause an increase in B cells to fight off the infection. As the B cells continue to multiply, it makes it more likely to transmit EBV to more B cells. Then what happens with burkitt’s lymphoma is that there is a transposition of a c-myc gene to B cells, which is more common the more times you divide. It basically causes continuous B cell replication.
