Chapter 38 - HIV Flashcards
describe retroviruses
- positive strand RNA viruses
- enveloped
- contain reverse transcriptase enzyme
- cause chronic disease long after infection
HIV is a _____ that causes _____
retrovirus; AIDS
how do retroviruses cause chronic disease long after infection
integration of viral DNA into host chromosome
describe HIV adsorption and penetration during initial infection and later during infection
- initial: M tropic: cells of macrophage lineage. receptor/coreceptor: CD4 and CCR5
- later: T tropic: T cells, receptor/coreceptor: CD4 and CXCR4
describe target cell binding of HIV
- 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
how can people be resistant to HIV
they lack the receptors necessary for fusion
what is HIV penetration due to
membrane fusion promoted by gp41
describe HIV genome replication
- 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
what is the major target for anti HIV drugs
RT enzyme
RT enzyme is _____
error prone
what is the integration of viral DNA copy into host cell genome promoted by
viral integrase enzyme
Viral DNA is transcribed into RNA by ______
host cell RNA polymerase II
what are the steps in HIV genome replication
- 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
describe HIV protein expression and viral assembly
- 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
what are the HIV accessory factors and what do they do
- 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
what are long terminal repeats
- 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
what is AIDS caused by
- HIV -1 (mainly): from Chimpanzee
- HIV2: from sooty mangabey virus
how can HIV enter body
-microabrasions on mucosal surfaces
- needle punctures
-intact mucosal surfaces
HIV virus may enter as:
part of an infected cell- macrophage, lymphocyte, spermatozoa
- free virus
what type of virus is AIDS
retrovirus
what is initial contact of HIV mediated by
macrophage lineage cells
- infect/stick to dendritic cells
- transport to lymph node and contact CD4 T cells
what is DTH reactions important for and what is it mediated by
important for controlling fungal and intracellular pathogens
- DTH is medaited by CD4T cells
what are the neurological symptoms fo HIV caused by
- not well understood
- possibly viral infection of neurons
- possibly release of substances by other cells that promote inflammation in the brain
what is the relationship between CD4T cells and amount of virus in the blood
direct
