HIV I Flashcards
What is HIV?
Retrovirus that causes AIDS = leads to opportunistic infections and AIDS related cancers
What is the single highest predictor of mortality in HIV?
AIDS related complications
What is the life expectancy of people with treated HIV?
Near normal life expectancy
What are the types of HIV?
HIV-1 = group M responsible for global pandemic HIV-2 = less virulent
What are the targets of HIV?
CD4+ receptors
What is CD4?
Glycoprotein found on surface of T helper cells, dendritic cells, macrophages and microglial cells
What are CD4+ T helper cells essential for?
Induction of adaptive immune response = recognition of MHC II, activation of B cells and CD8+ T cells, cytokine release
What are the normal CD4+ levels?
500-1600 cells/cubic mm = opportunistic infection risk if <200 cells/cubic mm
How does HIV affect the immune response?
Sequesters cells in lymphoid tissues Reduces proliferation of CD4+ cells Reduces CD8+ T cell activation Reduction in antibody class switching Chronic immune activation
What does the sequestering of cells in lymphoid tissues have?
Reduces circulating CD4+ cells
What effect does reduced CD8+ T cell activation have?
Dysregulated cytokine expression
Increased susceptibility to viral infections
How does HIV replicate?
Rapid replication in very early and very late infection = new generation every 6-12 hours
What is the average time till death in untreated HIV?
9-11 years
How does HIV infection become established?
Infection of mucosal CD4 cell = Langerhans and dendritic cells
Transport to regional lymph nodes
Infection established within 3 days of entry
How long does it take primary HIV infection to present?
Onset 2-4 weeks after infection= up to 80% present with symptoms, very high risk of transmission
What are the symptoms of primary HIV infection?
Fever, maculopapular rash more marked on trunk, myalgia, pharyngitis, headache/aseptic meningitis
What are some features of asymptomatic HIV infection?
Ongoing viral replication, CD4 count depletion and immune activation
Risk of onward transmission if remains untreated
What are opportunistic infections?
Infection caused by a pathogen that doesn’t normally produce a disease in a healthy individual
What is pneumocystis pneumonia?
Pneumocystis jiroveci infection = occurs if CD4 <200
What are the symptoms of pneumocystis pneumonia?
Insidious onset SOB, dry cough and exercise desaturation
What does a CXR of pneumocystis pneumonia show?
May be normal
Can show interstitial infiltrates and reticulonodular markings
How is pneumocystis pneumonia diagnosed?
BAL and immunofluorescence +/- PCR
What is the treatment for pneumocystis pneumonia?
High dose co-trimoxazole (+/- steroids)
Prophylaxis with low dose co-trimoxazole
What is an example of an opportunistic infection that shows epidemiological synergy with HIV?
Tuberculosis
What causes cerebral toxoplasmosis?
Toxoplasma gondii infection = occurs when CD4 threshold <150
What does a reactivation of cerebral toxoplasmosis cause?
Multiple cerebral abscesses
What are the symptoms of cerebral toxoplasmosis?
Headache, fever, focal neurology, seizures, reduced consciousness, raised ICP
What causes cytomegalovirus?
Reactivation of latent CMV infection = due to retinitis, colitis or oesophagitis
Occurs when CD4 threshold <50
What are the symptoms of cytomegalovirus?
Reduced visual acuity, floaters, abdominal pain, PR bleeding, diarrhoea
What should all patients with a CD4 threshold <50 receive?
Ophthalmic screening
What are some skin infections that can occur in HIV?
Herpes zoster = multidermatomal, recurrent
Herpes simplex = hypertrophic, aciclovir resistant
HPV = extensive, recalatriant, dysplastic
Penicillinosis and histoplasmosis
What is HIV associated neurocognitive impairment?
HIV-1 infection = reduced short term memory +/- motor dysfunction
What causes progressive multifocal leukoencephalopathy?
Reactivation of latent John Cunningham Virus = occurs when CD4 threshold <100
What are the symptoms of progressive multifocal leukoencephalopathy?
Rapidly progresses = focal neurology, confusion, personality change
What are some neurological presentations of HIV?
Distal sensory polyneuropathy, mononeuritis multiplex, vacuolar myelopathy, aseptic meningitis, GB syndrome, viral meningitis, cryptococcal meningitis, neurosyphilis
What are some aetiologies of HIV associated wasting?
Metabolic = chronic immune activation
Anorexia, malabsorption, hypogonadism
What are some examples of AIDS related cancers?
Kaposi’s sarcoma, non-Hodgkin’s lymphoma, cervical cancers
What causes Kaposi’s sarcoma?
Human Herpes virus (HHV) 8 = causes vascular tumour May be cutaneous, mucosal or visceral (pulmonary, GI)
What is the treatment of Kaposi’s sarcoma?
HAART, local therapies, systemic chemotherapy
What are some examples of non-Hodgkin’s lymphomas?
Burkitt’s lymphoma, primary CNS lymphoma
What causes non-Hodgkin’s lymphomas?
Epstein Barr virus = same diagnosis and treatment as for HIV negative patients (add HAART)
What are the symptoms of non-Hodgkin’s lymphomas?
More advanced B symptoms, bone marrow involvement, extranodal disease, CNS involvement
What causes cervical cancers?
Persistent HPV infection = test for HIV in all complicated HPV cases
Rapid progression to severe dysplasia and invasive disease
What are some non-opportunistic infections and other conditions that can occur in HIV?
Mucosal candidiasis, seborrhoeic dermatitis, diarrhoea, fatigue, worsening psoriasis, lymphadenopathy, parotitis, STIs, hepatitis B or C
What are some haematological conditions that can occur in HIV?
Anaemia affects up to 90%
Thrombocytopenia occurs when CD4 is 300-600
How common is sexual transmission of HIV?
Accounts for 95% of new infections in the UK
What are some factors that increase risk of sexual transmission of HIV?
Anoreceptive sex, trauma, genital ulceration, concurrent STI
What causes parenteral transmission?
Injection drug use = accounts for 2% of new diagnoses in the UK (quite uncommon)
Infected blood products or iatrogenic
When can mother to child transmission occur?
In utero, during delivery or via breast feeding
What is the risk of mother to child transmission occurring?
1 in 4 at-risk babies will become infected
Risk <0.1% when viral load undetected at delivery
What is the prognosis of “congenital” HIV?
1 in 3 HIV positive babies will die before their first birthday if untreated
What is the prevalence of HIV in the UK?
1.6/1000 in people >= age 15
What is the prevalence of HIV in different risk groups?
Male/male sex = 1:17
Heterosexuals age 15-44 = 1:1000
IV drug users aged 15-44 = 1:263
How common is undiagnosed HIV?
7% of people living with HIV in UK are undiagnosed
Heterosexual men are most likely to be undiagnosed
Where is universal HIV testing done?
In high prevalence areas (>0.2%) = recommended to all general medical admissions and all new patients registering at GP
Where are some places that opt out HIV testing is done?
Abortion services, GUM clinics, drug dependency services, antenatal services, assisted conception services
What are some high risk groups that should be offered HIV testing?
Gay men and female partners of bisexual men
People who inject drugs
Partners of people living with HIV
Adults and children from endemic areas
Sexual partners from endemic areas
History of iatrogenic exposure in endemic area
What are some areas of high prevalence?
Sub-Saharan Africa, Caribbean, Thailand
When is it acceptable to test for HIV on clinical grounds?
When HIV falls within the differential diagnoses
What are some features of taking an HIV test?
Document consent or refusal = request via ICE
Obtain venous sampling for serology
How should testing for HIV be done in a patient who is incapacitated?
Only test if in patient’s best interests
Consent from relative not needed
Wait until patient regains capacity of safe to do so
What are some features of third generation HIV antibody tests?
HIV-1 and HIV-2 antibody = detect IgG and IgM
Very sensitive in established infection
Window period of 20-25 days
What are some features of fourth generation HIV antibody tests?
Combined antigen and antibody (p24)
Shortens window period to 14-28 days
What are some features of a rapid HIV test (POCT)?
Fingerprick blood sample or saliva
Results within 20-30 mins
Third or fourth generation
What are the advantages of a rapid HIV test (POCT)?
Simple to use and no lab required
No venepuncture needed
Reduce follow up and good sensitivity
What are the disadvantages of a rapid HIV test (POCT)?
Expensive (£10) and difficult to quality control
Poor predictive value in low prevalence settings
Not suitable for high volume
Unreliable in early infection
