MicrobiologyBytes

HIV-2 is retrovirus a closely related to HIV-1, but seems to cause AIDS in only a minority of infected individuals (HIV-2: the forgotten AIDS virus. Trends in Microbiology 2008 Oct 27). Determining exactly why HIV-2 causes asymptomatic infection in most people could further our understanding of HIV immunopathogenesis. Studies to date have suggested that both enhanced immune responses and lower virus replication could play a role. Investigating immune responses in HIV-1-infected long-term nonprogressors (LTNPs) is one of the main approaches used to identify aspects of protective immunity to HIV, but the study of LTNPs is restricted by the small proportion of HIV-1-infected individuals who display slow or no progression to AIDS. In contrast, valuable insights might be gained into HIV immunopathogenesis from studies of HIV-2 cohorts with their high proportion of LTNPs.

HIV-2 is estimated to have entered the human population in 1940 (±16 years), approximately a decade after the introduction of HIV-1 into humans. The prevalence of this virus is highest in West Africa. Although the clinical features of HIV-2 AIDS mirror those of HIV-1, the AIDS-free survival rate at 5 years is significantly greater and the rate of CD4+ T cell decline was much slower than with HIV-1.

Subscribe to podcasts (free):
[iTunes] Enhanced podcasts & videos
[RSS] mp3 podcasts (audio only)
Play this episode: Enhanced version
Audio only

HIV-2 does not appear to be an attenuated virus since it is able to replicate equally as well as HIV-1, however, virus load and plasma RNA levels during the asymptomatic stages of HIV-2 infection are approximately 30-fold lower than with HIV-1. The reason for this seems to be better host immune control of HIV-2 infection. There is evidence that innate, cellular and humoral immune responses might all be more effective at controlling HIV-2 infection than HIV-1. Immune activation is also lower in HIV-2 patients than HIV-1 patients, resulting in a lower rate of CD4+ T cell decline. Unfortunately, HIV-2 infection offers no protection against HIV-1.

HIV-2 offers tantalizing glimpses into how HIV-1-induced AIDS might be approached, although as yet this has not had any tangible practical benefits.

Related:

• What have the Romans ever done for us?
• Parasitic worm may increase susceptibility to AIDS virus
• HIV mutation and the immune response
• How does HIV cause AIDS?
• Immune exhaustion in HIV infection
• HIV “can never be cured”

Tags: Biology, Health, HIV/AIDS, Medicine, Microbiology, Podcast, Science, Virology

This entry was posted on Monday, November 24th, 2008 at 9:00 am and is filed under Biology, HIV/AIDS, Health, Medicine, Microbiology, Podcast, Science, Virology. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.