HIV Flashcards
What is HIV
RNA retrovirus of the lentivirus genus
Causes acquired immunodeficiency syndrome (AIDS)
2 types of HIV
HIV-1: Type M and Type O
HIV-2
Epidemiology of HIV-2
predominantly confined to West Africa
Epidemiology of HIV-1 (type M and O)
Type M: prevalent in Europe, America, Australia and sub-Saharan Africa
Type O: mainly in Cameroon
Tramission
Unprotected sexual intercourse
Shared contaminated needles
Contaminated blood transfusions
Vertical transmission from mother to child. The virus crosses the placenta and is transmitted through breast milk
What is meant by vertical transmission in humans
From mother to child
Investigations
Bloods Virology screen Other infection e.g. TB if indicated HIV specific tests: -Enzyme-linked immunosorbent assay (ELISA) -Western blot test -Immunofluoresence assay (IFA) -Nucleic acid testing
Blood investigations
FBC U and Es LFTs Lipids Glucose HLA-B (5701 status) Lymphocyte subsets
What is assessed on Virology screen for HIV
HIV antibody HIV viral load HIV genotype Hepatitis serology Cytomegalovirus antibody Syphilis screen
Complications of HIV
Increased risk of opportunistic infections
Increased risk of malignancies
Examples of opportunistic infections that can result from HIV
Toxoplasma gondii CMV e.g. retinitis Pneumocystis jiroveci pneumonia Cryptococcal meningitis Mycobacterium avium complex Candidiasis Aspergillosis
Examples of malignancies that can result from HIV
Kaposi’s sarcoma
Non-Hodgkin’s lymphoma
Cervical cancer
Anal cancer
**HIV infection process
gp120 antigen on HIV binds to CD4+ receptors on the T cell
This process produces a conformational change and the need to bind to a co-receptor: CCR5 or CXCR4
gp41 binds to the co-receptor
This binding causes ‘six-helix bundle formation’ and fusion of the viral and host membranes
Disintegration of the viral capsid occurs causing viral RNA to be released into the human cell
Double-stranded RNA is produced and this process is catalysed by viral reverse transcriptase
Double-stranded RNA is integrated into host DNA using integrase enzyme
Host cell now manufactures new virions by long terminal repeat sequences and genes ‘tat’ and ‘rev’
What antigen on HIV binds to CD4+ receptors on T-cell
gp120
What antigen binds to CCR5 or CXCR4 coreceptor
gp41
What enzyme catalyses the production of double-stranded HIV RNA
viral Reverse Transcriptase
What genes in infected host cell manufactures new virions
Long terminal repeat sequences
‘tat’ and ‘rev’ genes
What enzyme integrates double-stranded RNA of HIV into the host DNA
Integrase
What genes are required for viral replication
PEG:
pol - encodes reverse transcriptase and integrase
env - encodes envelope proteins e.g. gp120
gag - encodes biral structural proteins
‘pol’ gene function
encodes reverse transcriptase and integrase
‘env’ gene function
encodes envelope proteins e.g. gp120
‘gag’ gene function
encodes viral structural proteins
Conservative treatment
Patient education including transmission reduction advice
Contact tracing
Psychological support
**Medical treatment
Highly active antiretroviral therapy (HAART):
2 x NRTIs combined with 1 x NNRTI
OR
2 x NRTIs combined with 1 x PI or 1 x II
NRTI = Nucleoside reverse transcriptase inhibitor NNRTI = Non-nucleoside reverse transcriptase inhibitor PI = Protease inhibitor II = Integrase inhibitor
