A new preventative HIV vaccine trial has kicked off in Australia under the direction of an Australian/Thai consortium.
The vaccine is one of about twenty preventative vaccines which are currently in human studies around the world.
The vaccine has two components – a DNA vaccine designed to trigger the production of immune cells which target HIV-infected cells, and a modified fowl pox vaccine designed to boost the number these HIV-specific cells. This strategy is known as ‘prime and boost’. Animals studies involving similar ‘prime and boost’ vaccines have been conducted by Australian researchers. These have provided encouraging evidence of protection against HIV infection.
The researchers are currently enrolling people deemed to be at low risk of HIV infection in a phase I safety study. Those at high risk of HIV (including sexual partners of HIV-positive people; individuals who have unprotected sex with a partner of unknown HIV status; individuals who report a sexually transmissible infection or injecting drugs in the last 12 months; and gay men who report an unprotected anal sex with partners of unknown HIV status in the previous 12 months) are not eligible to enter the safety study. The rationale is that high risk people who receive an experimental vaccine may put themselves at greater risk of HIV infection.
Twenty-four participants will receive three vaccinations over eight weeks. Half will be randomised to the experimental vaccine and half will receive placebo. Follow-up blood tests will be conducted over one year.
Although the study is designed to assess the safety of the vaccine in humans, researchers are planning to collect immunological data which may provide some indication of efficacy. Principal Investigator of the clinical trial Dr Tony Kelleher said, “We will also be able to undertake a range of sophisticated laboratory tests to determine if the vaccines stimulate the human immune system to produce anti-HIV responses. These responses will help us in further development of the vaccines.”
The decision to proceed to further safety and efficacy research will occur following interim analysis of the phase I data. If the safety of the vaccine is confirmed, subsequent testing will be occur in Thailand and Australia.
The vaccines are being supplied by Virax Holdings Ltd, a public company which is conducting ongoing research into the therapeutic application of the fowl pox technology. Virax has already conducted a safety study of its therapeutic vaccine in HIV-infected people. The possible clinical effectiveness of the fowl pox vaccine in boosting HIV-specific immune responses of people with HIV is being assessed in an extension trial scheduled for completion later this year.
The Australian/Thai Consortium which is coordinating the preventative vaccine study includes leading HIV researchers and scientists from several Australian universities and the Commonwealth Scientific and Industrial Research Organisation, as well as community groups and the Thai Red Cross. The study will be conducted at St Vincent’s Hospital, Sydney. The research is funded by the United State’s National Institutes of Health and supported by the Australian Federal Government.