Immunology Flashcards
HIV 2
Specific to Portuguese and West Africans
Less progressive, less immunocompromised with less opportunistic infections
Less responsive to treatment
HIV testing
Before 12 weeks
- p24 Antigen < 10 days (rules in but not out)
- HIV RNA or pro-viral DNA
After 12 weeks
- HIV serology
- HIV PCR
Hypersensitivity Reactions
Type 1 - IgE mediated
Type 2 - IgG mediated cytotoxicity
Type 3 - Immune Complex Ab-Ag mediated cytotoxicity
Type 4 - T cell mediated excitotoxicity
CCR5 heterozygous individuals
CCR5 is a co-receptor for HIV binding (in early infection). A lack of co-receptor CCR5 causes a slower progression or relative protection against HIV infection
HLA B5701 in HIV
MHC molecule on CD4 which has higher affinity for CD8 killer cells & are more likely to be able to control there viral load/slower progression of disease. These patients cannot be treated with Abacavir (risk hypersensitivity)
HIV medications with highest risk metabolic syndrome
Protease inhibitors “NAVIR”
along with high bilirubin, renal stones and lipodystrophy
Abacavir
NRTI
Hypersensitivity reaction in patients with HLA B5701 & risk of cardiovascular events
HIV drugs causing Lipodystrophy
Protease inhibitors
Zidovudine (NRTI)
Hepatitis B serology
Hepatitis B treatment contraindicated in cirrhosis
Peg IFN - should only be used in mild - mod disease (not cirrhosis!)
Can cause psychiatric disturbances and transient cytopenia
Active against Hep D coinfection
contraindicated in pregnancy
Intracranial lesions in HIV
- Toxoplasmosis
- Progressive multifocal leukoencephalopathy (PML), JC virus
- Primary Lymphoma
- Tb
- Abscess
- Kaposis (HHV8)
Toxoplasmosis lifecycle and treatment
Cat as host for parasite -> cat faces containing Ova ingested by animals -> Undercooked animal meat ingested by Humans -> pass onto fetus
Rx with Pyrimithamine-Sulphadiazine, with folic acid-> inhibits dihydrofolate reductase of plasmodia and thereby blocks the biosynthesis of purines and pyrimidines
CD4+ levels and Infections
< 200 PJP
< 100 Toxoplasmosis
< 50 Mycobacterim, CMV
IgM half life
7 days
T helper cells
Th1 - secretes IFN-gamma to activate macrophages, and induces B cells to produce opsonising IgG Ab’s which promote phagocytosis.
Th2 - secretes IL4, 5, 13 to up regulate IgE class-switching and activation of eosinophils (via IL5). Involved in Allergy and Parasite infections.
Th17 - secretes IL17 and IL22 to up regulate neutrophils and monocytes to target intracellular organisms, bacteria and fungi
TReg - Secretes IL10 and CTLA via FOXp3 transcription factor to suppresses IL2. Has an immunosuppressant role.
Hep B Immune phases
Immune Tolerance - HBeAg+, DNA ++, ALT normal
Immune Clearance - HBeAg+, DNA +, ALT high (treat)
Immune Control - HBeAg-, Anti-HBeAb +, DNA low, ALT normal
Immune Escape - HBeAg-, Anti-HBeAb +, DNA high, ALT high (treat)
Contrindication to PEG IFN in Hep B
- Cirrhosis or advanced Hep B (only used or mild-mod hep B)
- Pregnancy or lactation
- Neuropsychiatric disorders
Cryptococcus
CD4 count < 150
Yeast from bird dropping causing meningitis in HIV and immunocompromised patients
+ Cryptococcal Ag in serum and CSF
Treat with Amphotericin + Flucytosine for 2 weeks, then Fluconazole for 8 weeks
Toxoplasmosis
CD4 count < 50
Parasitic infection from Cats
Causes intracranial lesions with toxoplasmosis encephalitis
Toxoplasmosis Serology +
Rx with pyrimethamine-sulphadiazine (anti-parasitic)
Bactrim as prophylaxis CD4 < 100