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What are the 3 causes for secondary immunodeficiency?
Iatronic - which is brought on by medical tx.
Disorders like malnutrition, genetic defect,etc.
Primary infections like HIV/AIDS
What leads to genomic diversity with HIV what does it do?
Reverse transcriptase "retrovirus"
It converts RNA into viral DNA
Now the viral DNA can insert itself into host cell DNA
What is provirus
Integrated viral DNA
What encourages new virus production
Rev stimulates translation of gag and env
These proteins release viral RNA
What is the virology of the HIV
It is a lentivirus & is sRNA genome
In the cell mediated response, what does the cytotoxic T cells do?
They kill virus infected cell through interaction with MHC class I
*Nef gene (from HIV) inhibits expression of MHC clas I
Can the initial immune response to HIV reduce viral replication?
But does not eliminate
When are CD4 cells low?
When the viral load is at its highest
What depletes the CD4 cells?
Cytotoxic T cells
What cells are affected by HIV
Helper T Cells mostly affected by reducing CD4+ cells
*Lack of T cell help for cell mediated immunity & Signals to B cells are affected
What is the eclipse phase?
7-10 days post exposure
What type of cells are included in the CD4+ cells?
T-cells, mono's, macrophages, dendritic, microglial brain cells.
What is the CDC requirement for positive identification of HIV
- CD4 counts
- Certain bacterial infections
- Certain clinical conditions
- Which is then divided into Nine groups:
- A,B,&C each with three subgroups.
What is the WHO requiremtn for positive identification of HIV
4 levels of clinical staging:
Based on clinical appearance of the patient (when lab tests are unavailable)
3 aspects for lab ident in lab
Host Ab levels
Host CD4 and T cell coutns
What is the window period of false negatives for antibodies and antigens
Ab - 30 days
Ag - 15 days
Ag by nucleic acid testing is 12 days
CDC ident with CD4+ / T cells counts is?
CD4+ T cells <200uL
(normal range is 500-1500)
What HIV screenig tests are used
*CDC: a positive ELISA must be confirmed by a second and 3rd ELISA. If positive then a Western Blot is confirmatory***
- ELISA - sensitive & specific
- *Detects Ab's against viral lysates
What is the principle of the Western blot
Viral particls are separated then trenasferred onto a nicrocellulose paper then incubated with pt serum.
Can be visualized by EIA or biotin avidin
CDC interpretation: bands at 2 of the following 3 locations ⇨ p24, gp41, gp120/160
What test is used to detect the virus itself
*p24 increased at 7-20 days post inf.
Other tests used
- HIV genotyping
- RT-PCR (reverse transcriptase and real time)