Australian researchers are hoping to test an experimental DNA fowlpox virus in human studies in the near future following promising results in mice and monkeys.
Study of the vaccine in over 100 monkeys showed that the vaccine stimulated strong T-cell responses and prevented HIV infection, Dr Stephen Kent of the Macfarlane Burnett Centre told the Annual Conference of the Australasian Society for HIV Medicine in Perth on December 10.
When the monkeys were challenged with HIV following vaccination, none became infected. Dr Kent said that the vaccine stimulated increased levels of cytotoxic and CD4 responses to both env and gag proteins, similar to levels seen in HIV-infected people. Levels of the cytokine RANTES was also stimulated following vaccination.
Separately, the DNA and fowlpoxvirus HIV vaccines are ineffective against HIV. When used together in a prime-and-boost regimen, a strong T-cell response is produced.
While the HIV protein nef was not included in the vaccine, nef-specific responses were detected in monkeys following exposure to HIV. This indicates that very low levels of virus were replicating in the body, Dr Kent said. He concluded that the DNA/fowlpox vaccine seems to work by boosting immunity and facilitating the monkeys to fight off HIV infection.
The vaccine was developed by researchers at the Australian National University and the CSIRO. Several other groups are studying the combination DNA/fowlpox strategy worldwide.
Australian researchers estimate that the testing process will cost $A20 million over five years. Trials are expected to commence within the next two years.
Dr Kent said that many questions remain unanswered and that it is unknown whether the vaccine will safely prevent infection in humans.