HIV Flashcards
What viral group does HIV belong to?
Lentivirus group of the retrovirus family
Retroviruses are characterised by the possession of the enzyme reverse transcriptase, which allows viral RNA to be transcribed into DNA and thus incorporated into the host genome
What are transmission modes for HIV?
- Sexual intercourse
- Mother to child
- Contaminated blood, blood products and organ donations
- Contaminated needles
What is the pathogenesis of HIV?
At the time of initial exposure virus is transported by dendritic cells from mucosal surfaces to regional lymph nodes where permanent infection is established
The host cellular receptor that is recognised by HIV surface glycoprotein gp120 is the CD4 molecule, which defines the cell populations that are susceptible to infection
After the virus enters the body there is a period of rapid viral replication, leading to an abundance of virus in the peripheral blood. During primary infection, the level of HIV may reach several million
What immune cells are activated in the acute viraemia stage of HIV?
CD8+ T cells
The CD8+ T cell response is thought to be important in controlling virus levels, which peak and then decline, as the CD4+ T cell counts recover.
What immunological changes are seen in progressive HIV?
Reduction in CD4 count Increase in B2 microglobulin Decreased IL-2 production Polyclonal B-cell activation Decrease in NK cell function
How does HIV infection cause AIDS?
Ultimately, HIV causes AIDS by depleting CD4+ T cells. This weakens the immune system and allows opportunistic infections:
- During the acute phase, HIV-induced cell lysis and killing of infected cells by CD8+ T cells accounts for CD4+ T cell depletion, although apoptosis may also be a factor
- During the chronic phase, the consequences of generalized immune activation coupled with the gradual loss of the ability of the immune system to generate new T cells appear to account for the slow decline in CD4+ T cell numbers
After HIV infection, when does a person lose most of its CD4 cells?
First weeks of infection
The reason for the preferential loss of mucosal CD4+ T cells is that the majority of mucosal CD4+ T cells express the CCR5 protein which HIV uses as a co-receptor to gain access to the cells, whereas only a small fraction of CD4+ T cells in the bloodstream do so
HIV seeks out and destroys CCR5 expressing CD4+ T cells during acute infection
What are the three clinical staged of HIV?
- Acute infection
- Clinical latency
- AIDS
How do people in the acute HIV infection stage present?
Symptoms occur in 40–90% of cases and most commonly include fever, large tender lymph nodes, throat inflammation, a rash, headache, tiredness, and/or sores of the mouth and genitals.
The rash, which occurs in 20–50% of cases, presents itself on the trunk and is maculopapular, classically
What are the symptoms of the clinical latency stage of HIV?
While typically there are few or no symptoms at first, near the end of this stage many people experience fever, weight loss, gastrointestinal problems and muscle pains
Between 50% and 70% of people also develop persistent generalized lymphadenopathy
How is AIDS defined?
An HIV infection with either a CD4+ T cell count below 200 cells per µL or the occurrence of specific diseases associated with HIV infection.
How does AIDS present?
The most common initial conditions that alert to the presence of AIDS are pneumocystis pneumonia (40%), cachexia in the form of HIV wasting syndrome (20%), and esophageal candidiasis.
What oncological risk does AIDS carry?
Kaposi’s sarcoma, Burkitt’s lymphoma, primary central nervous system lymphoma, and cervical cancer
How is HIV/AIDS diagnosed?
Diagnosis of primary HIV before seroconversion is done by measuring HIV-RNA or p24 antigen
How would you manage a HIV positive patient?
dolutegravir/lamivudine/tenofovir FIRST LINE treatment
Highly active antiretroviral therapy
Initially, treatment is typically a non-nucleoside reverse transcriptase inhibitor (NNRTI) plus two nucleoside analog reverse transcriptase inhibitors (NRTIs)
