Pussy Cats may be key to HIV Vaccine

There have been numerous studies showing how dogs can benefit human health, by sniffing out cancer, for example. Now it is time for cats to shine, as researchers say they may hold the key to a human immunodeficiency virus (HIV) vaccine.

 
Researchers from the University of Florida and the University of California, San Francisco, have discovered that blood from patients infected with HIV shows an immune response against a feline AIDS virus protein.

Janet Yamamoto, professor of retroviral immunology at the College of Veterinary Medicine at the University of Florida and corresponding study author, told Medical News Today:
 
"Since FIV (feline immunodeficiency virus) and HIV-1 are distant cousins and their sequences are similar, we used the T cells from HIV positive human subjects to see if they can react and induce anti-HIV activity to small regions of FIV protein, which lead to the current story."

The team's findings are published in the Journal of Virology.

New vaccine-development strategy for HIV

The researchers say they are working on a T cell-based HIV vaccine that is able to activate an immune response in T cells from individuals against the feline acquired immunodeficiency syndrome (AIDS) virus.

T peptides are small pieces of protein that are crucial in this process, as they trigger the body's T cells to distinguish viral peptides on infected cells and attack them.

However, Prof. Yamamoto says that not all HIV peptides are able to work as vaccine components. Some enhance HIV infection or have no effect, while others have anti-HIV activities that become lost if the virus changes or mutates to avoid immunity.
Previous studies have shown that when combining various whole HIV proteins to create vaccine components, the results have not been strong enough to create a commercial vaccine.

But the researchers believe that the feline AIDS virus could be used to discover areas of the human AIDS virus, and this could lead to a new vaccine-development strategy for HIV.

"We had difficulty in identifying ways to select regions on HIV-1 for HIV-1 vaccine. Our work shows how to select the viral regions for HIV-1 vaccine. The regions on FIV or their counterpart on HIV-1 that have anti-HIV T cell activities can be used as a component for human HIV-1 vaccine," says Prof. Yamamoto.

FIV triggers T cells to kill HIV

To reach their findings, they acquired the T cells of patients who were infected with HIV. The T cells were isolated and incubated with different peptides that the researchers say are crucial for survival of both the human and feline AIDS viruses.

On comparing the reactions of the feline immunodeficiency virus (FIV) peptides with the reactions of the HIV peptides, the researchers discovered one particular peptide region on FIV that triggered patients' T cells to kill HIV.
 
They found that the feline viral region by human cells seems to be "evolutionarily conserved." This means it is present in many viruses similar to AIDS across animal species.

This feline viral region must be crucial, the researchers note, as it is unable to mutate in order for the virus to survive.

Prof. Yamamoto notes that so far, there have been no T cell-based vaccines used to prevent any viral diseases:

"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."

Dr. Jay A. Levy, professor of medicine at the University of California, San Francisco, and study author, stresses that their findings do not mean that the feline AIDS virus infects humans.
"Rather," he adds, "the cat virus resembles the human virus sufficiently so that this cross-reaction can be observed."

Prof. Yamamoto told Medical News Today that more of these cross-reactive regions on FIV need to be observed, as well as regions on the monkey AIDS virus (simian immunodeficiency virus):