Immunodeficiency Flashcards
what are immunodeficiency disorders?
abnormality(es) of the immune system that predisposes to diseases normally eradicated by a functional system
examples of types of disease that immunodeficient patients are at higher risk for
infections
neoplasms
three causes of immunodeficiency disorders
hereditary
infectious
iatrogenic
systemic diseases that can also produce immunodeficiency
alcoholism/malnutrition diabetes renal failure cushing's syndrome cancer
iatrogenic causes of immunodeficiency disorders
steroid therapy
cancer therapy
immunosuppressive drugs for transplant
surgical or functional splenectomy
how many primary immunodeficiency disorders known?
over 100
common types of inheritance of primary immunodeficiency disorders
autosomal recessive inheritance
what other types of disorders have increased risk for autoimmune disease?
disorders that affect T cells
loss of tolerance
cell-mediated defects appear
soon after birth
examples of cell-mediated defects
T cell (intracellular pathogens)
oral candida
other fungal infections
intracellular parasites
examples of intracellular parasites
cytomegalovirus
herpesvirus
pneumocystis
mycobacteria
humoral defects appear
several months after birth, fetus is protected by maternal antibodies
examples of humoral defects
B cell (extracellular pathogens) bacterial infections-staph, strep, hemophilus, giardia lamblia
asplenic defects
encapsulated bacterial infections-pneumonia, meningitis, flu, salmonella
AIDS
full manifestation of infection by human immunodeficiency virus-1 (HIV)
what does AIDS infect?
Th cells and dendritic cells (APCs)
what does AIDS produce defect in?
cell-mediated immunity
defects in cell-mediated immunity lead to predisposition to
opportunistic infections-pathogen doesn’t normally cause a problem in people with competent immune system
cancers (normally lymphomas)
nervous system damage
what represents the final stage of HIV infection?
AIDS
how is AIDS transmitted?
sexual contact
bloodborne
perinatal
classic risk factors for HIV: 4 H’s
homosexual men
Haitians
heroin users
hemophiliacs
what poses the greatest risk for HIV?
receptive anal sex
does HIV cross placenta?
yes, is present in breast milk
how is HIV not spread?
casual contact
bites
mosquitoes
toilets
rare examples of HIV transmission
needlesticks
blood transfusions
transmission percentages of HIV
46%: homosexual contact
15%: IV drug abuse
4%: homosexual contact and IV drug abuse (both present)
33%: heterosexual contacts of the above
seven things that have been proven to reduce transmission of HIV
- HIV testing of blood products/coagulation factors
- anti-retroviral prophylaxis before and during childbirth by HIV-positive mothers
- condom distribution and use
- needle exchange programs
- male circumcision
- formula feeding instead of breast feeding by HIV positive mothers
- early anti-retroviral treatment for an HIV-positive member of a serodiscordant couple
HIV structure
encapsulated retrovirus
what does HIV core contain?
SS RNA (two copies) protease integrase reverse transcriptase p24 protein
what is p24 in humans?
antigenic, evokes immune response
what does HIV envelope contain?
gp120 and gp41 proteins
what is the basis for antibody detection of HIV?
p24
what does reverse transcriptase do?
converts RNA to DNA upon infection
what does HIV infection require?
binding of virus to CD4 receptor
gp120 co-binds another receptor
what is gp120 necessary for?
virus to bind to T helper cells
what happens once the HIV virus is internalized?
RNA is converted into DNA by reverse transcriptase
what is the problem with reverse transcriptase?
not accurate, inconsistent DNA production across viruses
results in genomic changes
what happens once DNA is produced by reverse transcriptase?
DNA is inserted into T cell genome using integrase enzyme
what happens after viral DNA is transcribed/translated?
new viral parts are made
new viral RNA can be re-incorporated to make new viruses
what does protease do?
cleaves immature protein into mature protein, makes functional parts
what happens with new virus particles?
they bud from infected T cell
how can T cells pass virus?
from one cell to another
why is direct cell-cell transfer bad?
it escapes immune attack
cannot be recognized and attacked by antibodies
what happens to free gp120 from lysed Th cells?
they bind and block CD4 receptors of other Th cells
what does binding of gp120 to CD4 receptors produce?
weak cell-mediated and humoral response, ineffective
how do antiviral drugs work?
they act on different steps of infection
-can attack adhesion, reverse transcription, integration
multiple steps are affected by different drugs
HIV primary infection timeline
weeks to months
what does primary HIV infection resemble?
infectious mononucleosis
sx primary HIV infection
fever, fatigue, myalgias, lymphadenopathy, etc.
what is primary HIV infection characterized by?
high viral load
HIV latency phase timeline
years to decades
what is HIV latency phase characterized by?
gradual decrease in Th (CD4) counts
controlled viral load
persistent generalized lymphadenopathy
what are the criteria for AIDS?
CD4 count less than 200 and/or AIDS defining illness
what is AIDS characterized by?
increased viral load
what is HIV infection CDC classification based on?
CD4 counts (1-3) clinical sx (A-C)
what CDC categories have AIDS?
all category 3 and C
is CDC classification used clinically?
no
categorized for epidemologic purposes
what do many AIDS defining illnesses have in common?
many opportunistic infections
opportunistic infections-pneumocystic carinii (jirovecii)
serious pneumonias
prophylaxis-Bactrim
opportunistic infections-candida
affects mucosal surfaces
can cause more severe infections
opportunistic infections-HSV
extensive full-thickness burns of the epidermis or necrotizing encephalitis
opportunistic infections-cytomegalovirus (CMV)
intractable colon problems (diarrhea), lung/brain infections
opportunistic infections-toxoplasmosis (protozoan)
severe encephalitis
opportunistic infections-tuberculosis
major health risk that HIV-infected people pose to healthy people
opportunistic infections-atypical mycobacterial infections (M. avium, M. intracellulare, M. kansaii)
untreatable
opportunistic infections-histoplasmosis (fungus)
disseminated infection
common, everyone exposed
examples of opportunistic infections group 1
pneumocystis carinii (jairovecci) candida HSV CMV toxoplasmosis TB atypical mycobacterial infections histoplasmosis
opportunistic infections-cryptococcus (fungus from pigeon droppings)
pneumonia
encephalitis
opportunistic infections-aspergillosis (fungus from HS bio)
pneumonia
opportunistic infections-cryptosporidiosis (protozoan)
intractable diarrhea
JC papovavirus
progressive multifocal leukoencephalopathy
epstein barr virus or herpesvirus 8
tumors or pseudotumors
- lymphomas
- kaposi sarcoma (infectious disease)
examples of opportunistic infections group 2
cryptococcus aspergillosis cryptosporidiosis JC papovavirus epstein barr or herpesvirus 8-lymphomas, kaposi sarcoma
what are opportunistic infections?
mostly intracellular parasites that escape humoral and innate immune defenses
diagnosis HIV-what test is used for screening?
ELISA-enzyme-linked immunosorbent assay
what does ELISA test for?
antibodies to p24 and other antigens
how long does it take for an ELISA test to be positive after exposure?
6-8 weeks after exposure, may take 6 months
ELISA pro
cheaper
ELISA con
false positives and negatives
what is always used to confirm a positive ELISA test?
western blot
what does a western blot do?
tests for antibodies, higher specificity
what is used to follow patients with HIV?
PCR
what does PCR do?
polymerase chain reaction
detects and quantifies viral DNA
“viral load”
how long does it take for a PCR to be positive following HIV exposure?
7 days
how do antiretroviral drugs treat HIV?
block viral replication at different points
what type of antiretroviral drugs are there?
reverse transcriptase inhibitors
protease inhibitors
integrase inhibitors
entry inhibitors
reverse transcriptase inhibitors (nucleoside and non-nucleoside varieties)
prevent viral DNA formation
protease inhibitors
prevent formation of viral proteins
integrase inhibitors
prevent integration of viral DNA into host
entry inhibitors
prevent viral attachment and/or entry into T cell
what is HIV combination therapy called?
HAART
what has HAART accomplished?
significantly improved lifespan and quality
is HIV curable
no, only treatment not curative
remains uncurable
reasons we do not have a HIV vaccine
humans develop no effective natural immunity
virus changes rapidly-even with the same host
antibodies don’t protect well
populations who need it most cannot afford it
all previous attempts have been failures
what populations would be most benefitted from a HIV vaccination?
IV drug abusers
third world countries