[NAIROBI] Strategies for developing new HIV vaccines and for stalling the development of HIV/AIDS drug resistance may be hampered by high secondary infection rates, when an individual is re-infected with a second strain of HIV, according to researchers.
The rate of HIV/AIDS secondary infection among people living with the disease in Uganda could be as high as primary HIV infection rates among the general population, a study published in the Journal of Infectious Diseases last month (5 June), has found.
The finding that secondary infection — also referred to as 'superinfection' — is common "suggests that the immune response elicited by primary infection confers [only] limited protection and raises concerns that vaccine strategies designed to replicate the natural anti-HIV immune response may have limited effectiveness," the study says.
Vaccines aimed at blocking new HIV infections, therefore, need to create an immune system response that is stronger or different to the natural immune response, according to Andrew Redd, lead researcher at the US National Institutes of Health.
The study was a collaboration between researchers in Uganda and the United States. The team initially tested 149 HIV-positive heterosexual individuals for secondary infection, at the time of their HIV diagnosis, and again a year later, shortly before they were to begin antiretroviral therapy. Seven individuals were found to be re-infected with a second strain of HIV.
Redd said that providing counselling to newly diagnosed HIV-positive individuals reduced their proclivity to high risk behaviour, but that they still showed higher risk behaviour than the HIV-negative population.
Future research might also explore why some individuals who are at high risk of secondary HIV infection do not become superinfected, said Redd.
"It might be possible to find a protective natural immune response to HIV that could then be recreated in uninfected individuals through a vaccine strategy," he added.
Peter Cherutich, head of HIV prevention at Kenya's National Aids and STI [sexually transmitted infections] Control Programme, said that high rates of secondary infections may be because of inconsistent condom use, low treatment coverage and low rates of HIV status knowledge, compounded by HIV complacency and multiple concurrent sexual partnerships. "HIV/AIDS is now considered a chronic disease just like many others," he said.
Francis Nyamiobo, a research physician at the Kenya Aids Control Project at the University of Nairobi, Kenya, said: "Multiple infections will most likely complicate the search for an HIV vaccine; this is because a vaccine targets a specific strain, and when a patient is infected with more than one strain, then the vaccine would not be effective".
Journal of Infectious Diseases doi: 10.1093/infdis/jis325 (2012)