(HealthDay News) – HIV-1 disease progression seems to be inhibited by co-infection with HIV-2, with the slower rate of progression enhanced in those whose HIV-2 infection preceded HIV-1 infection.

Joakim Esbjörnsson, PhD, from Lund University in Sweden, and colleagues examined the natural history of disease progression in individuals infected with HIV-1 and HIV-2. A total of 223 participants who were infected with HIV-1 alone, or co-infected with HIV-2, were followed up for approximately 20 years.

The researchers found that the median time to development of AIDS was 104 months for participants with dual HIV-1 and HIV-2 infection and 68 months for those infected with only HIV-1 (P=0.003). Among participants with dual infection the levels of CD4+ T cells were higher, and levels of CD8+ T cells increased at a lower rate, indicative of slower disease progression. The longest time to AIDS and highest levels of CD4+ T-cell counts were seen for dually infected participants for whom HIV-2 infection preceded HIV-1 infection. The genetic diversity of HIV-1 was significantly lower in participants with dual infection versus those with HIV-1 infection alone.

“In the present study, we found that HIV-2 has an inhibitory effect on the rate of HIV-1 disease progression in vivo,” the authors write. “This inhibition was evident in the time to AIDS, at the cellular level of the immune system, and at the molecular level of HIV-1 evolution.”

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