HIV and T-cells

Chelsea Harmon

Catherine Hanson

Abby Llaneza

Jen Williams

Introduction CD4 is a protein located on the

surface of the Helper T cell CD 4 helper cells are located on

Helper T cells which attract the virus to the cell.

CD 4 normally functions as an agent to help bind MHC Class II to the Macrophage

Time Course of HIV and AIDS Acute Phase

– Sharp rise of virus in the blood– Consequent drop in CD4 T cells– Immune system most damaged by HIV

Chronic Phase– Immune system recovers somewhat– HIV fairly steady for several years

AIDS Phase– CD4 Level drops below 200 cells per cubic mm

of blood– Opportunistic infections arise

Time Course Diagram

HIV Life Cycle Begins with Virus binds to the helper T-cell

surface and it fuses with the cell membrane It empties its contents into the cell and the HIV

enzyme reverse transcriptase copies the viral genetic material from RNA into double-stranded DNA and another HIV enzyme, integrase splices into the cellular DNA.

Provirus, the integrated DNA is used as a blueprint that makes the cell produce viral proteins and RNA.

Another enzyme, the HIV protease cleaves the new proteins allowing them to join the RNO in new viral particles that eventually bud from the cells and infect other helper T-cells.

HAART Highly Active Antiretroviral Therapy This therapy is used to achieve

maximum viral suppression Includes 2 nucleoside analogues and 1

protease inhibitor Costs $10,000 to $12,000 a year Drawbacks: Many pills to keep track

of, high resistance rates, pill failures

Measuring Viral Load

HIV replicates prolifically from the start of infection

HIV levels remain fairly stable for several years because the body responds for a time by manufacturing huge amounts of CD4 T-cells.

Measuring Viral Load (cont.)

Findings:– Investigators found that in untreated patients the

strength of the initial immune response exerts a decisive influence on the rate of progression to AIDS

– Strong immunological activity in the acute phase of infection helps to preserve the body’s later ability to manufacture the subset of CD4 T cells that specifically react to HIV.

– At any stage viral levels correlate with prognosis. Many studies suggest that patients whose viral concentrations fall into the undetectable realm and stay there are most likely to avoid progression to AIDS.