There are over 63,000 people in Canada living with Human Immunodeficiency Virus (HIV), and six new people are infected each day. If managed correctly, life with HIV can be long and healthy. However, there is still no cure and treatment can be arduous.
But now, researchers from the University of Manitoba and University of Toronto are one step closer to developing an HIV vaccine.
The researchers have demonstrated that, with a little help from the chickenpox (varicella-zoster) virus, it could be possible to safely deliver HIV genes and generate immunity to HIV, without the risk of using the actual HIV virus.
A blended chickenpox/HIV vaccine would take advantage of the fact that the chickenpox virus undergoes silent cycles of reactivation in the body. Each time it ‘wakes up’ from its dormant state, the body’s immunity quickly controls it and a person’s immunity is boosted.
By inserting select HIV genes into the chickenpox virus, the researchers expect the vaccine to stimulate HIV immunity in a similar way. Immunity that would also be refreshed each time the chickenpox virus is reactivated. In theory, this would counteract a virus that, due to its extremely high mutation rate, is able to escape both host immunity and, in some cases, antiretroviral drug treatment.
Despite potential, this work had stalled due to concerns that the approach would trigger an immune reaction and activate CD4-positive T cells, the type of immune cell the HIV virus uses to cause infection. If activated, this could actually increase a person’s susceptibility to HIV.
“Our study investigated an important safety concern that posed a barrier to this vaccine strategy,” explains Kelly MacDonald, a professor of internal medicine and immunology at both the University of Manitoba and Toronto.
To test whether a high-dose chickenpox vaccine would trigger this ‘HIV-welcoming’ immune reaction, MacDonald and her team vaccinated 44 healthy, HIV-negative women who were at low risk for HIV exposure and tested positive for immunity to chickenpox.
Working alongside the Kenyan AIDS Vaccine Initiative, the researchers tested each participant’s blood and mucosal cells in the cervix and rectum over the next 12 weeks, looking for activated CD4-positive T cells. They found no significant difference compared to pre-vaccination levels, meaning no increased risk of HIV infection as a result of the vaccine.
Based on these findings, the stage is set to move forward with the hybrid chickenpox-based HIV vaccine, with the potential to produce a safe, long-lasting, protective immune response to HIV.