ICL 1.15: AIDS Flashcards
which family of viruses is lentivirus in?
retrovirus
which cells does HIV infect?
infects T-cells and macrophages primarily
what receptors does HIV have to bind to to succesfully enter a cell?
must bind to CD4 receptor
AND
B-chemokine co-receptor is needed for viral entry
CCR5 or CXCR4 are major co-receptors
so you need both CD4 and either CCR5 or CSCR4 for HIV to bind to host cell
what is the root cause of clinical manifestations of HIV?
loss of the T-cell arm of the immune system results in the clinical manifestations of HIV
occurs through the decline of CD4 cells
but the mechanism of decline is only partly understood
how many types of HIV are there?
HIV comes in 2 types: HIV1 and HIV2
HIV2 isn’t common in the US
HIV1 comes in different groups: M,N,O,P
then in HIV1M there are different subtypes/clades: A-K
what is the prevalence of HIV in the US?
HIV prevalence is increasing due to derease in death rate
HIV incidence is decreasing due to anti-viral therapy
transmission of a virus depends on which 3 major factors?
- inoculum dose
- exposure time
- host susceptibility
you need all 3 things to get an active infection
which body fluids are not HIV infectious?
non-bloody fluids such as saliva, tears, sweat, feces are non-infectious
saliva has antibody, not virus
which body fluids are HIV infectious?
- blood
- genital fluids
- cerebrospinal fluid
- breast milk
what is the inoculum dose?
the amount of virus required to set up an active infection
some viruses have very low inoculation doses which is scary because it means it doesn’t take alot of the virus to infect someone
what is the viral load?
the amount of virus
how does HIV host-susceptibility work?
host susceptibility requires TWO receptors to get into the cell
if you lack one of the receptors like CD4 or one of the coreceptors (CCR5 or CSCR4) it decreases your susceptibility to HIV
what is the most common exposure route of HIV?
blood transfusion
how are we trying to eliminate HIV?
by decreasing the viral load in a person to the point that it’s almost zero
if the viral load is undetectable then you can’t transmit it to another person during sexual contact!
what are the characteristics of an acute HIV infection?
it’s usually self-limiting!
onset of illness is about 2 weeks after infection
and you start making antibodies a couple weeks in
most patients don’t present for medical care during acute HIV infection
what are some of the symptoms of HIV?
- fever
- fatigue
- myalagia
- skin rash
- headache
- pharyngitis
these are all pretty vague so most people don’t go to the doctor in the early stages of HIV
it also often gets mistaken as mononucleiosis
what are the differences between HIV and EBV?
HIV
- acute onset
- minor tonsil tissue hypertrophy and exudate is rare
- mucocutaneous ulcers common (35-50%)
= rash common (<50%)
EBV
- subacute onset
- significant tonsil tissue hypertrophy and exudate is common
- mucocutaneous ulcers are rare
rash is rare without penicillin/amoxicillin use
what does an HIV rash look like?
literally nothing
it’s so faint and doesn’t last long either
how does your CD4 count change throuhghout an HIV infection?
when you get infected with HIV there’s disregulation and deterioration of T cell arm of the immune system
usually a healthy person has 1000 cells/cc CD4 cells
with infection your CD4 cell count takes a sharp drop then recovers quickly then declines over the years
but you don’t get sick till your CD4 count is less than 200 and you’ll be super sick when it’s under 50
the problem is that when someone comes into your office with vague symptoms and their CD4 count is still pretty normal, it’s hard to figure out what’s wrong
what’s the range of CD4 cells throughout an HIV infection?
CD4 Count > 500 (28%) often asymptomatic
CD4 Count 200 - 500 increasing incidence of thrush, shingles, pneumococcal pneumonia, etc.
CD4 Count <200 (14%) at risk for opportunistic infections. Begin PCP prophylaxis. AIDS by CDC definition
CD4 Count <50 at risk for Mycobacterium avium infection, cytomegalovirus
when will HIV patients present to the clinic?
- Patients are more likely to present with protean clinical complaints that point to a damaged immune
system= CD4 < 200 - Or self-refer for testing because they perceive themselves to be at risk
- Or present with an AIDS –defining illness
what are the clinical findings that suggest HIV?
- persistent generalized lymphadenopathy
- unexplained cytopenia (RBC, WBC, PLT)
- recurrent pneumonia
- Kaposi’s sarcoma
- trush (oral candidiasis)
- wasting syndrome
- TB
- pregnancy (all pregnant women need HIV test during each pregnancy)
- STD/STI
- CNS involvement like depression, memory loss, neuropathy
- fever of unknown origin
- unexplained constitutional complaints
what diagnotic tests can you run at the different stages of HIV?
post infection:
1 week: viral RNA
2 weeks: p24ag
5 weeks: western blot
how do you diagnose HIV?
HIV is diagnosed by detection of viral RNA, p24antigen, or antibody
what is a 3rd generation HIV test?
3rd generation HIV tests detect IgG/IgM AB to HIV 1 and HIV 2
but this must be confirmed with a western blot
what is a 4th generation HIV test?
4th generation HIV testsdetect IgG/IgM AB to HIV 1and HIV 2 and p24 Ag
but this must be confirmed witha differentiation assay
what is the eclipse period?
the eclipse period is the initial interval after HIV infection when no existing diagnostic test is capable of detecting
would you rather have a low or high viral load with a low or high CD4 count?
you’d rather have a low CD4 count with a low viral load because the infection will more slower
what is the goal of antiretrovirals?
to obtain an undetectable viral load
they can restore NORMAL life expectancy and decrease morbidity and viral transmission
