The quest to develop a vaccine against HIV, the virus that causes AIDS, might receive help from the common house cat.
A vaccine that prevents the cat version of HIV/AIDS was developed recently and could provide insights into developing a human HIV vaccine, the feline vaccine creator Janet Yamamoto, of the University of Florida at Gainesville, told United Press International.
HIV/AIDS is a global epidemic and many experts think a vaccine that prevents infection is the only way to curtail the rising number of cases of the disease that destroys the immune system and is expected to claim tens of millions of lives in coming years.
Feline Immunologic Virus or FIV, which is similar to HIV, causes a condition similar to AIDS in cats. In August, Fort Dodge Animal Health of Overland Park, Kan., launched its FIV vaccine called Fel-o-vax, which is based on technology developed by Yamamoto.
"The FIV vaccine clearly gives hope that an HIV vaccine could work," said Yamamoto, who now is focused on developing an HIV vaccine.
Jorge Flores, chief of the vaccine clinical research branch in the division of AIDS at the National Institute of Allergy and Infectious Diseases in Bethesda, Md., agreed the cat vaccine may have lessons for HIV researchers.
"The field of HIV vaccine technology has been following very closely the developments of the FIV vaccine," he told UPI.
Some HIV researchers, however, have ignored lessons to be gleaned from the cat vaccine, Yamamoto said. She said she has been "trying to get the science community to accept" these lessons and apply them to HIV vaccine development.
Her efforts to spread the word among scientists include giving a lecture at the National Institutes of Health in Bethesda this week and writing a review of insights gained from the FIV vaccine that soon will appear in a reputable AIDS journal.
One of the main lessons, she said, is vaccines should contain the entire virus. Most HIV vaccines currently under development use only certain components of the virus, not the whole virus. That is a mistake, Yamamoto said, because the whole virus elicits a better immune response so the body is better able to prevent HIV infection.
The whole-virus approach, however, raises safety concerns. The virus would be inactivated to make it incapable of causing disease but there are concerns that if some of the virus escapes the inactivation procedure then it still could infect people. That is not a risk scientists are willing to take in light of the fact HIV infection ultimately is a death sentence.
"The ideal thing would be an (inactivated whole-virus vaccine) but we cannot take a chance here," Flores said. "Ethically the world has come to the conclusion that would be unacceptable" even in countries where the virus is endemic because it would be putting people's lives at risk, he said.
However, scientists at SAIC, a Frederick, Md., firm that conducts research for the National Institutes of Health on a contractual basis, are developing a whole-virus approach. The scientists have developed one method of inactivating the virus and are trying to develop other methods, Flores said. As a safety measure, the Food and Drug Administration requires at least two inactivation methods to ensure the virus is rendered harmless. Inactivation methods are difficult to develop because they must de-activate the virus while leaving its structure intact so it still induces an immune response from the body, Flores said.
The SAIC researchers are continuing their research, however, because they "do not yet have a vaccine" and ultimately might discover how to make their approach safe, Flores said.
Another lesson offered by the cat vaccine is selection of the viral strain is critical to the effectiveness of the vaccine, Yamamoto said. Strains of virus from people who are infected but resist developing AIDS for several years, if ever, appear to induce a much better immune response, she said.
Scientists developing HIV vaccines have not paid attention to that and that could explain why some vaccines have not worked well, she said.
Flores said there has been heated debate among AIDS researchers about which strains would be the best to use in a vaccine. Most vaccines use strains of virus that cause AIDS early on, he said. One reason is HIV-infected people who do not develop AIDS for years harbor many different strains of the virus in their body and it is difficult to know which one to choose for a vaccine, he said.
Scientists also should consider using multiple strains of the virus in a single vaccine, Yamamoto said. There are several different strains of the virus and a vaccine based on one strain may not prevent infection from another strain, she said.
Flores acknowledged most HIV vaccines only have contained a single strain, but he noted a vaccine that contains three strains is slated to begin tests in humans "very soon."
