microbiology

Question 1

what is the mutation that causes Kaposi’s sarcoma?

Answer 1

RB and P53 tumor suppressor genes

Question 2

what is the cause of outbreaks of diarrhea caused by cryptosporidium parvum?

Answer 2

1- inadequate purification of drinking water
2- swimming in fecally contaminated pool and lakes
3- resistance of cysts to chlorination but it can be killed by pasteurization and removed by filtration

Question 3

why skin test in fungal infetion can only be used for epidimiologic studies not diagnostic ?

Answer 3

because it can give false negative in 2 reasons
1- false -ve in due to cross reactivity
2- false -ve in dissaminated disease
3- cen stmulate AB response and conduse serologic test

Question 4

what is the role of cellular proteins in HIV replication?

Answer 4

1- chemokines CXCR4and CCR5 for entrance
2- actin and tubulin for movement of viral DNA into the nucleus
3- cyclinT1 with other viral proteins for Transcription
4- other proteins for budding

Question 5

what are the different types of patients infected by HIV

Answer 5

1- Classical type: detected HIV with decrease number of CD4+ using an anti-viral drug
2- Elite controllers: no HIV detected with normal CD4+number (maybe due to certain HLA and P21)
3- mutated nef gene individuals: long term infection without OI and normal CD4+ count
4- non-progressors individuals: having large amount of alpha-defensins interfere with binding to CXCR4 receptor

Question 6

when will the clinical picture of AIDs appear?

Answer 6

1- ultimate failure of CD8+ to control the infection due to nef proteins and a large number of CD4+ have died so there is no response to IL-2
2- some of the patients have rapid progression of AIDs due to mutation in gene encoding MHCI

Question 7

what are the main 3 mechanisms in which HIV invades the immune system?

Answer 7

1- integration of viral DNA into host DNA
2- high rate mutated env gene
3- production of tat and nef gene required for MHC downregulation

Question 8

what are the mechanisims that HBV cause HCC?

Answer 8

1- HBx gene => oncogen
2- persistant regeneration
3- insertional mutagens

Question 9

which of the following HB markers present in a chronic carrier state but result in negative laboratory results?

Answer 9

HBsAb because it is bind to a high number of HBsAg