HIV Vaccine takes big step

A phase 2b clinical trial of a novel preventive HIV vaccine regimen developed by Harvard Medical School researchers based at the Ragon Institute of Massachusetts General Hospital, MIT and Harvard, Beth Israel Deaconess Medical Center and partners has begun in southern Africa.

The investigational regimen is designed to induce responses to different strains of the virus found in many regions of the world. The new study is the first to test whether the vaccine is able to reduce the incidence of HIV infection.

Scanning electron micrograph of HIV particles infecting a human T cell. Image: National Institute of Allergy and Infectious Diseases

Scanning electron micrograph of HIV particles infecting a human T cell. Image: National Institute of Allergy and Infectious Diseases.

“One of the major challenges for HIV vaccine development is the tremendous genetic diversity of the virus,” explained Bruce Walker, the HMS Phillip T. and Susan M. Ragon Professor of Medicine at Mass General and director of the Ragon Institute.

“Viruses from patients in Boston may be 40 percent different from viruses found in Africa, so developing a vaccine that can protect against these diverse strains is an enormous, unprecedented challenge,” Walker said.

Called the Imbokodo trial from the Zulu word for rock—echoing a South African proverb that refers to the strength of women and their importance in the community—the new study has begun enrolling young women in South Africa, the country with the greatest prevalence of HIV infection worldwide.

Regulatory approval is being sought in Malawi, Mozambique, Zambia and Zimbabwe. The trial is being conducted at clinical sites coordinated by the HIV Vaccine Trials Network in collaboration with scientists in southern Africa.

Imbokodo has a goal of enrolling 2,600 uninfected, sexually active women, ages 18-35, who will receive vaccinations at four timepoints over one year—either the experimental, mosaic-based vaccine regimen or a placebo—to determine whether the vaccine regimen can reduce the incidence of HIV infection.

The vaccine regimen being tested, originally developed in the laboratory of Ragon Institute founding member Dan Barouch, HMS professor of medicine at Beth Israel Deaconess, includes a mosaic vaccine—so called because it contains genetic sequences from different HIV strains prevalent in many parts of the world.

“A safe and effective global HIV vaccine will almost certainly be needed to end the HIV epidemic,” said Barouch, who is also director of the Center for Virology and Vaccine Research at Beth Israel Deaconess.

“This clinical trial will determine whether this vaccine candidate will prevent HIV infection in young women in sub-Saharan Africa,” he added.

Barouch began pursuing the mosaic vaccine strategy in 2007, and early versions of mosaic vaccines tested in several animal models showed very promising results prior to initial human testing.

Earlier this year, Barouch and partners reported preliminary results of the phase 1/2a APPROACH study at the 9th International AIDS Society Conference on HIV Science, indicating that the experimental vaccine appeared to be well tolerated and that the most promising regimens triggered the desired antibody responses in all of the healthy volunteers who received them.

Source: HMS

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