Antiretroviral drug regimens that are of benefit in treating HIV type 1 infection are less efficacious against HIV-2, according to a case series published in the June 15th edition of Clinical Infectious Diseases. This leads the study’s authors to call for more clinical trials of HAART for the treatment of HIV-2 infection.
HIV type 2 was identified in Senegal in 1985, and was the second human retrovirus discovered that causes AIDS. HIV-2 is transmitted at a lower rate than HIV-1, and has a slower disease course, with 85% of infected people remaining free of symptoms for over eight years.
Although it has largely remained confined to West Africa, HIV-2 infection has recently been found in India, Europe and the United States, albeit with low prevalence. “The lack of studies undertaken to reveal associations between clinical and virologic parameters and disease or therapeutic efficacy has resulted in uncertainty in the treatment and management of HIV-2-infected patients,” state the study’s authors.
The investigators present the case histories of ten HIV-2-infected patients living in the United States, covering CD4 cell counts, HIV-2 viral loads, and details of clinical illnesses and treatments. All of the patients originated from West Africa, and seven were male.
Three patients were classified as ‘asymptomatic’ (CDC class A1 or A2), with the remaining seven being ‘symptomatic’. At baseline, the asymptomatic patients had higher CD4 cell counts (median 639 vs. 175 cells/mm3; p
Two of the asymptomatic patients and all of the symptomatic patients were provided with antiretroviral therapy. Physicians prescribed drug combinations that were similar to HIV-1 HAART regimens, but modified on the basis of findings from in vitro studies. Most of the drug combinations included more than one protease inhibitor, but the use of NNRTIs was avoided.
Five of the patients changed drug combination at least once over the course of follow-up (median 35 months). The various HAART regimens failed to suppress viral loads to below the limit of detection (100 copies/ml) in any of the eight patients with detectable viral load at baseline, despite five of these reporting no problems with drug adherence.
In addition, antiretroviral therapy did not cause a reduction in viral load greater than 2 log10 copies/ml in any of the symptomatic patients, despite improvements in CD4 cell counts in three patients and modest improvements in clinical symptoms.
“Our preliminary observations suggest that drug regimens with documented efficacy in treating HIV-1 infection may not demonstrate similar efficacy for treatment of HIV-2 infection,” conclude the authors. “Controlled clinical trials of HIV-2-infected patients who are receiving various HAART regimens are clearly needed to provide therapeutic guidance to the medical community.”
Importantly, the case series demonstrated a clear link between low viral loads, high CD4 cell counts and clinical outcome, “providing evidence that HIV-2 virus load is useful in managing treatment of patients with HIV-2 who are receiving therapy.”
Further information on this website
HIV-2 globally - overview of HIV-2
French HIV-2 cohort study: treat only when plasma viral load can be measured - news story
Viral diversity in Africa - news story
Reference
Mullins C et al. Highly active antiretroviral therapy and viral response in HIV type 2 infection. Clin Infect Dis 38: 1771-1779, 2004.