How a cat virus could lead to an HIV vaccine

Researchers believe the feline AIDS virus can be used to identify regions of the human AIDS virus that might be more effectively used to develop an HIV vaccine. (Credit: Misty/Flickr)

Blood from people infected with HIV shows an immune response against a cat AIDS virus protein, a finding that may help scientists find a way to develop a human HIV vaccine.

“One major reason why there has been no successful HIV vaccine to date is that we do not know which parts of HIV to combine to produce the most effective vaccine,” says Janet Yamamoto, a professor of retroviral immunology at the University of Florida College of Veterinary Medicine and the study’s corresponding author.

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She says the discovery supports further exploration of a human AIDS vaccine derived from regions of the feline AIDS virus.

Yamamoto and colleagues are working on a T-cell-based HIV vaccine that activates an immune response in T cells from HIV-positive individuals against the feline AIDS virus.

T-cell peptides are small pieces of protein that can prompt the body’s T cells to recognize viral peptides on infected cells and attack them. However, not all HIV peptides can work as vaccine components.

“In humans, some peptides stimulate immune responses, which either enhance HIV infection or have no effect at all, while others may have anti-HIV activities that are lost when the virus changes or mutates to avoid such immunity,” she says.

“So, we are looking for those viral peptides in the cat AIDS virus that can induce anti-HIV T-cell activities and do not mutate.”

In previous studies, scientists have combined various whole HIV proteins as vaccine components, but none have worked well enough to be used as a commercial vaccine, Yamamoto says.

“Surprisingly, we have found that certain peptides of the feline AIDS virus can work exceptionally well at producing human T cells that fight against HIV.”

For the study, reported in the Journal of Virology, researchers isolated T cells from HIV-positive individuals and incubated these cells with different peptides that are crucial for survival of both human and feline AIDS viruses. They then compared the reactions they got with feline immunodeficiency virus (FIV) peptides to what they found using HIV-1 peptides.

“We found that one particular peptide region on FIV activated the patients’ T cells to kill the HIV,” Yamamoto says.

This feline viral region identified by human cells appears to be evolutionarily conserved—it is present in multiple AIDS-like viruses across animal species.

“That means it must be a region so essential that it cannot mutate for the survival of the virus,” she says.

The researchers believe the feline AIDS virus can be used to identify regions of the human AIDS virus that might be more effectively used in a vaccine-development strategy for HIV.

“We want to stress that our findings do not mean that the feline AIDS virus infects humans, but rather that the cat virus resembles the human virus sufficiently so that this cross-reaction can be observed,” says study collaborator Jay A. Levy, professor of medicine at the University of California, San Francisco.

To date, a T-cell-based vaccine has not been used to prevent any viral diseases, Yamamoto says. “So we are now employing an immune system approach that has not been typically utilized to make a vaccine. The possible use of the cat virus for this vaccine is unique.”

The National Institutes of Health supported the research.

Source: University of Florida