HIV 1- pathophysiology and presentation Flashcards
What is HIV
Human Immunodeficiency Virus
a retrovirus which can cause Acquired Immunodeficiency Syndrome (AIDS)
how is AIDS prevented in HIV positive people
early diagnosis and treatment
those with treated HIV have a ‘near normal’ life expectancy
what does AIDS cause
opportunistic infections
AIDS related cancers
what is the target site for HIV
CD4+ receptors
what is CD4
a glycoprotein sound on the surface of a range of immune cells:
- T helper lymphocytes (CD4+ cells)
- Dendritic cells
- Macrophages
- Microglial cells
what to T helper cells (CD4+ Th cells) do
essential for induction of the adaptive immune response
Recognise MHC2 antigen presenting cells
Activate B-cells
Activate cytotoxic T cells (CD8+)
Cytokine release
what does HIV do to the immune response
Reduces circulating CD4+ cells
Reduced proliferation of CD4 cells
Reduction in CD8+ T cell activation
Reduction in antibody class switching
Chronic immune activation
what is a normal CD4+ sound
500-1600 cells/mm3
risk of opportunistic infection if <200 cells/mm3
how does the HIV virus replicate
rapid replication in very early and very late stage
new generation every 6-12 hours
how does the HIV infection spread around the body
Infection of mucosal CD4 cell
transport to regional lymph node
Infection established within 3 days of entry
Dissemination of virus
how does a primary HIV infection present
80% present with symptoms
onset is 2-4 weeks after infection
fever rash myalgia pharyngitis headache/aseptic meningitis
v high risk of transmission
what happens to the virus during asymptomatic infection
ongoing viral replication
ongoing CD4 count depletion
ongoing immune activation
still risk of transmutation
just no symptoms
what are opportunistic infections
infection caused by a pathogen that does not normally produce disease in a healthy individual
uses the ‘opportunity’ given by a weakened immune system
what organism often causes an opportunistic pneumonia in those with HIV
Pneumocystitis Jiroveci
in people who’s CD4 count is <200
how do you treat pneumoncystitis Jiroveci pneumonia
High dose co-trimoxazole (+/- steroid)
what bacterial infection is much more common in HIV+ve individuals than HIV-ve
TB
Symptomatic primary infection Reactivation of latent TB Lymphadenopathies Miliary TB Extrapulmonary TB Multi-drug resistant TB Immune reconstitution syndrome
what are the characteristics of cerebral toxoplasmosis in those with HIV
Toxoplasma gondii infection
CD4 <150
headache fever focal neurology seizures reduced consciousness raised intracranial pressure
what are the characteristics of cytomegalovirus in HIV
CMV
CD4 threshold <50
causes retinitis, colitis, oesophagi’s
presentation:
- reduced visual acuity
- floaters
- abdo pain, diarrhoea, PR bleeding
ophthalmic screening given for all those CD4 <50
what skin infections are more common in HIV
Herpes Zoster Herpes Simplex Human Papilloma Virus Weird/wonderful -penicilliosis -histoplasmosis
what are some important HIV associated neurological problems
HIV associated Neurocognitive impairment (HIV-1)
-reduced short term memory +/- motor dysfunction
Progressive multifocal leukoencephalopathy (JC virus)
- rapidly progressing
- focal neurology
- confusion
- personality change
what is ‘slim’s disease’
HIV-associated muscle wasting
caused by:
- metabolic (chronic immune activation)
- Anorecia
- Malabsorpiton/diarrhoea
- hypogonadism
what are some AIDS related cancers
Kaposi’s sarcoma
Non-hodgkins lymphoma
Cervical cancer
what is Kaposi’s sarcoma
Sarcoma caused by the Human Herpes Virus 8 (HHV8)
vascular tumour
cutaneous
mucosal
visceral (pulmonary, GI)
treat with HAART( highly active antiretroviral therapy) local therapy or systemic chemo
what is non-hodgkin’s lymphoma
caused by EBV
cancer of B cells
presents with: B symptoms Bone marrow involvement Extranodal disease Increase CNS involvement
Tx- HAART
what is cervical cancer
cancer of the cervix caused by HPV
rapid progression to severe dyplasias and invasive disease
HIV testing should be offered for all complicated HPV presentations
What non-opportunistic infections are also symptomatic of HIV
Mucosal Candidiasis Seborrhoeic Dermatitis Diarrhoea Fatigue Worsening psoriasis Lymphadenopathy Parotitis Epidemioloigcally linked conditions eg. STIs, Hep B, Hep C
what haematological conditions are caused by HIV
Anaemia (effects up to 90%)
Thrombocytopenia (CD4 300-600)
how is HIV transmitted
Sexual transmission
Parenteral transmission
Mother to child
what factors increase HIV sexual transmission risk
Anoreceptive sex
Trauma
Genital ulceration
Concurrent STI
what is parenteral transmission
transmission from injection drug use
infected blood products
iatrogenic
how can HIV be passed from mother to child
In utero/trans-placental
During delivery
Breast feeding
what group of people are at the highest risk of HIV in the uk
Men who have sex with men (MSM)
effects 1:17
1:7 in London
who should be tested for HIV
Everyone in high prevalence areas
Opt-pout testing in certain clinical settings
Screening of high risk groups
Testing in the presence of clinical indicators
when is there opt-out HIV testing offered
Termination of Pregnancy Genitourinary Clinics Drug Dependency Services Antenatal services Assisted conception services
when should you test on clinical groups
if HIV is in the differentials - any chance there is HIV
how do you take an HIV test
Document consent
Obtain venous sample for serology
Request via ICE
Ensure pathway is in place for retrieving and communicating result
what markers are used by labs to detect HIV infection
Viral RNA
Antigen
Antibody
what do 3rd generation HIV antibody tests identify
if HIV-1 or HIV2
IgM and IgG
v sensitive/specific in established infection
Average 20-25 days window periods
what can 4th generation HIV antibody tests do
Identify combined antibody and antigen
shortens window period
window 14-28 days
negative 4th generation test at 4 weeks = v likely to exclude HIV infection
what is a rapid HIV test (POCT)
Fingerprick blood specimen or saliva
Results within 20-30 mins
3rd generation (Ab only)
4th generation (Ab/Ag)
advantages of POCT
simple to use no lab needed no venopuncture needed no anxious wait reduced follow up good sensitivity
disadvantages of POCT
expensive £10 quality control poor positive predictive value in low prevalence settings not suitable for high volume cant be relied on in early infection
