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
What is cerebral toxoplasmosis treated with?
pyrimethamine
What is the CD4 threshold level of CMV?
occurs at CD4 <50
What does CMV cause?
either causes retinitis (reduced visual acuity and floaters) or colitis or oesophagitis (GI symptoms)
What screening can be done for CMV in those with CD4 < 50?
ophthalmic screening to check for chorioretinitis
Describe HIV associated neurocognitive impairment?
HIV 1 itself is neurotoxic, effects can happen at any CD4 but tends to be worse at lower counts, can cause reduced short term memory and motor dysfunction
Describe multifocal leukoencephalopathy?
cause by opportunistic infection of JC virus, causes rapidly progressing focal neurology, confusion and personality changes
What CD4 count does multifocal leukoencephalopathy occur at?
CD4 < 100
What skin infections are present in normal individuals but may be worse in HIV?
herpes zoster, herpes simplex, HPV
How may herpes zoster in HIV present?
multidermatomal and recurrent
How does herpes simplex in HIV present?
extensive, hypertrophic, aciclovir resistant
How does HPV in HIV present?
extensive, treatment resistant and dysplastic
What is HIV associated wasting?
severe weight loss in HIV which has multiple aetiologies, e.g. metabolic from immune activation, anorexia, malabsorption, hypogonadism
AIDS increases risk of many cancers but name the 3 AIDs defining cancers?
kaposis sarcoma
non hodgkins lymphoma
cervical carcinoma
Describe kaposis sarcoma?
vascular tumour from the herpes virus
causes purple lesions/ plaques, can appear on the skin, GI tract or respiratory tract
Describe non hodgkins lymphoma in HIV?
frequently extranodal, often involves the brain
Describe cervical carcinoma in HIV?
there is increased risk of cervical carcinoma caused by oncogenic HPV, annual cervical screening is needed
List some non-AIDS symptoms that may occur in the latent/ asymptomatic stage?
mucosal candidiasis seborrhoeic dermatitis worsening psoriasis diarrhoea fatigue lymphadenopathy parotitis neuro issues leuko or lymphopenia
Anyone with unexplained leuko or lymphopenia should _____
be offered HIV test
What accounts for most HIV transmission? Name the other modes of transmission?
sexual (79%)
other - drug injection, infected blood transfusions, mother to child, breast feeding
What increases risk of sexual transmission of HIV?
anoreceptive sex (as more lymphoid tissue in the rectum and anal sex is more likely to cause microabrasions), trauma, genital ulceration, concurrent STI (as may have more CD4 receptors present)
High risks groups for HIV that should be offered tests?
MSM females partners of MSM adults from endemic areas and children PWID partners of people with HIV
Describe the HIV tests and when they are positive?
the test for p24 antigen will be positive after 6 weeks of infection
the test for antibody is not positive until 3 months after infection
Describe treatment of HIV?
everyone starts treatment regardless of CD4 count on highly active antiretroviral therapy
this is a combination of 3 drugs from at least 2 drug classes to which the virus is susceptible to
adherence is really important to stop development of resistance
checking for drug interactions is also important
Ways to prevent HIV?
achieving undetectable viral load (as then it cant be transmitted from the infected person) PrEP PEP condoms encouraging disclosure
Describe PrEP?
for those at high risk can be given daily or on demand and usually tenofovir or emtricitabine
Describe PEP?
start within 72 hours of high risk exposure ART taken for 4 weeks, tenofovir/ emtricitabine and raltegravir
Effectiveness of PrEP and PEP?
PrEP - 86% effective
PEP- about 80% effective (but obviously difficult to get data on)
