The trial, called ‘STEP’, was halted in September 2007 because preliminary results suggested that people who had been given the vaccine were more likely to be infected with HIV than people who had been given a placebo.

The researchers behind the study, from Imperial College London, King’s College London and Royal Holloway, University of London, say their findings mean scientists may have to rethink other vaccines they are developing for diseases like HIV, tuberculosis and malaria, which are delivered in the same way, using the same virus ’shell’.

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The International Maternal Pediatric Adolescent AIDS Clinical Trials Group is conducting the studies, which are sponsored and funded by the National Institute of Allergy and Infectious Diseases (NIAID) and the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), both part of the National Institutes of Health.

“These studies are important because HIV infection and pregnancy both increase the risk for a poor immune response to the normal 15-microgram dose of seasonal influenza vaccine given to the general population,” says NIAID Director Anthony S. Fauci, M.D. “Moreover, children, young people and pregnant women are at higher risk for more severe illness from the 2009 H1N1 influenza virus than other groups, and HIV-infected individuals in these populations may be particularly vulnerable.”

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The researchers from Harvard Medical School, Boston, Massachussetts; Los Alamos National Laboratory, Los Alamos, New Mexico; and the National Institute of Allergy and Infectious Diseases, Bethesda, Maryland detail their findings in the October 2009 issue of the Journal of Virology.

HIV-1 replication peaks during the period of primary infection, therefore it is estimated that 50% of sexually contracted HIV-1 cases occur when the individual transmitting the virus is newly infected. No vaccines capable of inducing antibodies that completely neutralize a variety of HIV-1 isolates are currently available, however prior studies show that vaccine-elicited, virus-specific T-lymphocyte populations can limit viral replication during primary infection in nonhuman primates.

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“Developing an effective AIDS vaccine has eluded scientists because the virus is tricky,” says Guido Silvestri, MD, a Yerkes affiliate scientist and director of clinical virology at the University of Pennsylvania School of Medicine and lead author of the commentary. Silvestri, along with co-author James Else, DVM, associate director for veterinary resources at Yerkes, writes, “Over 25 years after the discovery of HIV as the etiological agent of AIDS, no effective vaccine for the disease is available.”

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Now, a study by Dan Barouch, MD, PhD, and a scientific team at Beth Israel Deaconess Medical Center (BIDMC), reported in the July 20 Advance Online issue of Nature Medicine, shows this was likely not the case.

“Our findings demonstrate that there is no correlation between Ad5 neutralizing antibodies and T-cell immune responses,” explains Barouch, who is Chief of the Division of Vaccine Research at BIDMC and Associate Professor of Medicine at Harvard Medical School. “Moreover, subjects with baseline Ad5-specific neutralizing antibodies did not develop higher levels of Ad5-specific T-cell responses as compared with subjects without baseline Ad5-specific neutralizing antibodies.”

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“These new findings represent an important step forward in HIV vaccine research,” says Anthony S. Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases (NIAID), part of the NIH, which provided major funding and other support for the study. “For the first time, an investigational HIV vaccine has demonstrated some ability to prevent HIV infection among vaccinated individuals. Additional research is needed to better understand how this vaccine regimen reduced the risk of HIV infection, but certainly this is an encouraging advance for the HIV vaccine field.

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