HIV and CD4 Cell life

Infection with HIV reaches a stabilized viral load at six months after infection and usually remains at this level or it will increase for a few years in the absence of antiretroviral therapy. Prior to infection, population based studies done on MSM have shown CD4 counts to be about 1000/ mm3. At six months this level decreases to a mean value of 780/mm3 and then down to 670/mm3 at the one year mark; however, some patients don’t do as well and have significantly lower CD4 levels at one year. For example, out of 40 newly acquired HIV infected individuals, eleven of them had CD4 counts below 350/mm3 by week 36 (month 9) and 20 or 50 percent of the patients had reached this CD4 threshold at 72 weeks (after 18 months). That means a lot of individuality is causing some people’s immune system to be more susceptible to HIV infection, most likely their individual genetics. In addition, if a higher total viral load is transmitted into the infected individual during initial contact, more HIV viruses may be present from the start of infection.

In the early stages of infection a rapid decline in CD4 cells may be the sign of destruction of CD4 cells or a shift of CD4 cells from the peripheral blood to lymphatic tissue. Subsequent years of infection have shown to cause a decrease in CD4 count of about 50/mm3 per year. This means the most amount of CD4 cells are lost during the initial year of infection. The rate of decline per year is correlated with total viral burden. There is an average decrease of 4 percent per log10 copies/ml per year in one study. Sometimes an individual sustains their high levels of CD4 cell counts and are known as “chronic nonprogressors.”

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References:

John G. Bartlett. The stages and natural history of HIV infection. Wloters Kluver. UpToDate. <http://www.uptodate.com.ezproxy1.library.arizona.edu/contents/the-stages-and-natural-history-of-hiv-infection?source=search_result&search=HIV&selectedTitle=1~150> Accessed: 7/8/2012.