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May 5, 2008
Stimulated Cells Control SIV, and Hopefully HIV
A method for enhancing immune responses to simian immunodeficiency virus (SIV), the monkey version of HIV, was able to significantly control viral reproduction in infected macaques, say the authors of a study published in the online journal PLoS Pathogens. The authors say these study results, which were also reported at a vaccine and immunotherapy conference last month in Australia, pave the way for future studies exploring the same technique in people with HIV.
Efforts to stimulate immune responses to HIV in people living with the virus have had little success thus far, regardless of the methods used. Though researchers have been able to achieve measurable increases in certain types of immune cells, this has not translated into control of HIV levels in blood in the absence of antiretroviral (ARV) therapy. The same has been largely true with SIV in various species of macaque monkeys who become ill from the virus.
Robert De Rose, of the Department of Microbiology and Immunology at the University of Melbourne, in Australia, and his colleagues hypothesized that exposing an SIV-infected macaque’s immune cells to a variety of overlapping SIV proteins and then reinfusing those cells might help the macaques’ immune systems control the virus. De Rose’s team compared this method, called overlapping peptide-pulsed autologous cells (OPAL), with ARV treatment in 36 pigtail macaques.
All of the macaques began receiving the ARV drugs Viread (tenofovir) and Emtriva (emtricitabine) by subcutaneous injection once a day, three weeks after becoming infected with SIV. All remained on ARV treatment for at least seven weeks. Twenty-four of the macaques also received a series of four OPAL treatments: 12 had their immune cells stimulated by SIV peptides from the Gag protein of the virus, and 12 had immune cells stimulated by peptides from several SIV proteins. At the end of the seven weeks, the macaques that had received the OPAL treatments stopped receiving ARV treatment, while those that didn’t receive the OPAL treatments continued to receive ARV treatment.
De Rose’s team found that the macaques that received the OPAL treatments maintained very good control of SIV levels in blood for a year following the treatments and, in fact, had lower levels of SIV than the macaques that stayed on ARV treatment. What’s more, whereas nearly half of the macaques on continuous ARV treatment died during that year, 90 percent or more of the macaques that received either type of OPAL treatment survived.
While it is far too soon to tell whether the OPAL technique will work in people living with HIV, De Rose says that the positive results of this study offer sufficient promise to begin studying OPAL in humans. De Rose also points out that if the technique is successful in people with HIV, it should cost much less over time than current treatments.
