VIR201 is an experimental therapeutic vaccine currently in phase I / II studies. The aim of therapeutic vaccines is to augment the body's immune response to HIV and to delay or prevent progression to AIDS.

VIR201 is being developed by Virax Holdings Limited and early testing of VIR201 in people with HIV is underway in Australia.

The same vaccine technology, originally developed by scientists at the Australian National University and the Commonwealth Scientific and Industrial Research Organisation, is being tested as a preventative vaccine by an Australian / Thai consortium.

VIR201 uses DNA vaccine technology called Co-X-Gene in which HIV and human genetic material have been grafted on to a harmless fowlpox virus. This fowlpox vector carries genetic material for HIV proteins gag and pol. The aim of this component of the vaccine is to stimulate HIV-specific immune responses in people who have very low levels of HIV in their blood due to antiretroviral therapy. The vaccine also carries genetic material to stimulate the cytokine or immune system messenger called interferon gamma which is associated with delayed disease progression. The aim of this second component of the vaccine is to boost levels of interferon gamma and improve immune functioning.

Current research

A phase I / IIa study of VIR201 was conducted in 34 HIV-infected people in Australia. All had commenced combination antiretroviral therapy within six months of contracting HIV and were randomised to receive three injections of VIR201or placebo over 12 weeks. This study found VIR201 was safe but had no detectable effect on the immune system.

Despite the disappointing finding, an extension study is ongoing to assess the ability of VIR201 to control viral load in people who have ceased antiretrovirals.

Animal studies indicate this vaccine is safe and can stimulate strong HIV-specific immune responses (Kent 1998; Dale 2000).

References

Dale CJ et al. Induction of HIV-1-specific T-helper responses and type 1 cytokine secretion following therapeutic vaccination of macaques with a recombinant fowlpoxvirus co-expressing interferon-gamma. Journal of Medical Primatology 29(3-4):240-247, 2000.

Kent SJ et al. Enhanced T-cell immunogenicity and protective efficacy of a human immunodeficiency virus type 1 vaccine regimen consisting of consecutive priming with DNA and boosting with recombinant fowlpox virus. Journal of Virology 72: 10180-10188, 1998.