Chapter 38 - HIV

Question 1

describe retroviruses

Answer 1

• positive strand RNA viruses
• enveloped
• contain reverse transcriptase enzyme
• cause chronic disease long after infection

Question 2

HIV is a _____ that causes _____

Answer 2

retrovirus; AIDS

Question 3

how do retroviruses cause chronic disease long after infection

Answer 3

integration of viral DNA into host chromosome

Question 4

describe HIV adsorption and penetration during initial infection and later during infection

Answer 4

• initial: M tropic: cells of macrophage lineage. receptor/coreceptor: CD4 and CCR5
• later: T tropic: T cells, receptor/coreceptor: CD4 and CXCR4

Question 5

describe target cell binding of HIV

Answer 5

• viral ENV protein gp120 binds to cellular receptor CD4 and to coreceptor CXCR4 or CCR5
• coreceptor interaction essential for gp41 contact and viral fusion with host cell

Question 6

how can people be resistant to HIV

Answer 6

they lack the receptors necessary for fusion

Question 7

what is HIV penetration due to

Answer 7

membrane fusion promoted by gp41

Question 8

describe HIV genome replication

Answer 8

• reverse transcriptase synthesizes one strand of DNA using viral RNA as the template
• reverse transcriptase synthesizes the other strand of DNA using the newly created viral single DNA strand
• cellular tRNA used as a primer by reverse transcriptase

Question 9

what is the major target for anti HIV drugs

Answer 9

RT enzyme

Question 10

RT enzyme is _____

Answer 10

error prone

Question 11

what is the integration of viral DNA copy into host cell genome promoted by

Answer 11

viral integrase enzyme

Question 12

Viral DNA is transcribed into RNA by ______

Answer 12

host cell RNA polymerase II

Question 13

what are the steps in HIV genome replication

Answer 13

• synthesis of viral DNA copy
• integration of viral DNA copy into host cell genome
• transcription of integrated viral DNA copy to create more viral RNA
• HIV protein expression and viral assembly

Question 14

describe HIV protein expression and viral assembly

Answer 14

• viral RNA serves as mRNA for translation
• viral RNA serves as the viral genome that is packaged into virions
• viral assembly occurs at the plasma membrane
• virions acquire their membrane by budding of nucleocapsids from the plasma membrane
• translation creates vrial polyproteins
• viral polyproteins get cleaved to final mature sizes by viral protease

Question 15

what are the HIV accessory factors and what do they do

Answer 15

• nef: decreases expression of MHC class I molecules on the surface of an infected cell, preventing killing by cytotoxic T cells
• vpu: reduces cell surface CD4 expression and enhances viral release

Question 16

what are long terminal repeats

Answer 16

• transcriptional promotor (upstream LTR) and terminator (downstream LTR)
• promotor responds to host cell signals and can also be relatively dormant, creating the latent state which is an inmportatn characterisitic of HIV

Question 17

what is AIDS caused by

Answer 17

• HIV -1 (mainly): from Chimpanzee
• HIV2: from sooty mangabey virus

Question 18

how can HIV enter body

Answer 18

-microabrasions on mucosal surfaces
- needle punctures
-intact mucosal surfaces

Question 19

HIV virus may enter as:

Answer 19

part of an infected cell- macrophage, lymphocyte, spermatozoa
- free virus

Question 20

what type of virus is AIDS

Answer 20

retrovirus

Question 21

what is initial contact of HIV mediated by

Answer 21

macrophage lineage cells
- infect/stick to dendritic cells
- transport to lymph node and contact CD4 T cells

Question 22

what is DTH reactions important for and what is it mediated by

Answer 22

important for controlling fungal and intracellular pathogens
- DTH is medaited by CD4T cells

Question 23

what are the neurological symptoms fo HIV caused by

Answer 23

• not well understood
• possibly viral infection of neurons
• possibly release of substances by other cells that promote inflammation in the brain

Question 24

what is the relationship between CD4T cells and amount of virus in the blood

Answer 24

direct

Question 25

what are AIDS indicator conditions

Answer 25

- candidiasis of the bronchi, trachea or lungs - candidiasis, esophageal - kaopsi sarcoma - mycobacterum avium complex (MAC) or mycobacterium kasasii, disseminated or extrapulmonary - mycobacterium tuberculosis - mycobacterium - pneumocystitis jiroveci pneumonia

Question 26

what is the transmission of HIV

Answer 26

by direct exposure of the persons bloodstream to body fluid containing virus

Question 27

where is HIV found in someone who is infected with the virus

Answer 27

- blood -semen - vaginal fluid

Question 28

HIV is not transmitted by ______

Answer 28

casual contact like sneezing, kissing, bug bites

Question 29

transmission of HIV even through needlestick is ______. less than _____ of exposures show seroconversion

Answer 29

poor; 1%

Question 30

what is AIDS

Answer 30

progressive destruction of CD4+ cells elads to collapse of immune system

Question 31

what is an AIDS patient suscpetible to

Answer 31

opportunistic pathogens

Question 32

what central nervous system disease is also associated with AIDS

Answer 32

dementia

Question 33

what are AIDS related cancers

Answer 33

Kaposis sarcoma caused by human herpes virus 8

Question 34

what are the treatments for AIDS

Answer 34

-nucleoside analogue reverse transcriptase inhibitors - nonnucleoside RT inhibitors - protease inhibitors - fusion penetration inhibitors

Question 35

is there a vaccine for AIDS

Answer 35

no

Question 36

what are other human retroviruses

Answer 36

- Human T cell lymphotrophic viruses I, II, III, and IV

Question 37

what does HTLV I cause

Answer 37

adult T cell leukemia and lymphoma

Question 38

what does HTLV II, III and IV cause

Answer 38

no known diseases associated with these viruses