HIV Flashcards
What type of virus is HIV? What does that mean?
RNA retrovirus
means it uses reverse transcriptase
Describe the two types of HIV?
HIV-1 and HIV-2
HIV-1 is the most frequently occurring strain globally. HIV-2 is almost entirely confined to West Africa.
When is there rapid replication of HIV?
in very early and very late infection
Describe how infection occurs after initial contact?
There is infection of mucosal CD4 cells
occurs and these transport the virus to the regional lymph nodes
once transported to regional lymph nodes permanent infection occurs and there is dissemination as virus infected CD4 cells enter the blood strean
What type of cells does HIV infect?
CD4+ cells
How does HIV affect the immune response?
Reduced circulating CD4+ cells
Reduced proliferation of CD4+ cells
Reduction CD8+ (cytotoxic) T cell activation
Dysregulated expression of cytokines
Reduction in antibody class switching ( refers to a B cell choosing to switch from producing IgE to IgM etc) Reduced affinity of antibodies produced
Chronic Immune Activation (microbial translocation)
How long does it take from HIV exposure to get established HIV infection?
72 hours
What are the stages of HIV? What is CD4 count and HIV RNA copies levels at each stage?
Primary infection: significant fall in CD4 and increase in HIV
Asymptomatic Infection: fall in HIV RNA copies before steady rise, slight rise in CD4 before steady fall
AIDs: increasing HIV RNA copies and CD4 decreasing to very low levels
What are normal CD4 parameters and when is there highest risk of opportunistic infections?
Normal parameters= 500-1600 cells/mm3
Highest risk of opportunistic infections: < 200 cells/ mm3
Describe when primary infection HIV symptoms occur and what symptoms are?
Up to 80% of people have symptoms 2-4 weeks after infection
unfortunately diagnosis may be missed as symptoms are non-specific and get better
combination of: fever, maculopapular rash, myalgia, pharyngitis, headache/ aseptic meningitis
Is there a high risk of transmission at the primary infection stage?
very high risk of transmission
Describe when asymptomatic infection occurs and what is happening?
rate of clinical progression is variable, majority of people are asymptomatic for a substantial but variable length of time
may have HIV indicators but not AIDs defining conditions
there is ongoing viral replication, CD4 count depletion, immune activation and risk of onwards transmission if remains undiagnosed
Define opportunistic infection?
an infection caused by a pathogen that does not normally produce disease in a healthy individual
it uses the opportunity afforded by a weakened immune system to cause disease
List some examples of opportunistic infection in HIV?
pneumocystis pneumonia tuberculosis cerebral toxoplasma cytomegalovirus jc virus
PCP is caused by ______
fungus - pneumocystis jiroveci
CD4 threshold for PCP is?
< 200
Symptoms of PCP?
Insidious onset of SOB and dry cough exercise desaturation (O2 sats fall rapidly when exercising)
CXR of PCP?
may be normal or show diffuse interstitial infiltrates and reticulonodular markings
How is PCP diagnosed?
with BAL and IF
Treatment of PCP?
high dose co-trimoxazole +/- steroid
Describe prophylaxis of PCP in those with HIV?
prophylactic dose of co-trimoxazole can be given in those with CD4 < 200 to prevent PCP occurring
Describe tuberculosis in HIV?
in those with HIV there is more likely to be symptomatic primary infection, reactivation of latent TB, lymphadenopathies, miliary TB, immune reconsitution syndrome (immune system recovers slightly but then has massive inflammatory response to opportunistic infection)
CD4 threshold for cerebral toxoplasmosis is?
CD4 < 150
Describe what happens with cerebral toxoplasmosis and the symptoms?
there is reactivation of latent infection which causes multiple cerebral abscesses and sometimes chorioretinitis, fever, headache, raised ICP, seizures, focal signs, decreased consciousness
