An update on clinical trials in the first plenary session at AIDS Vaccine 2009 today showed that more effective HIV vaccines are in the pipeline than any that have been tested before.
Gary Nabel, director of the Vaccine Research Centre at the US National Institute of Allergy and Infectious Diseases, said: “We have exciting new candidates that are eliciting response that have not been seen before.”
He told the packed hall that the HIV Vaccine Trials Network is currently testing a product that has shown great promise immunologically – in the lab delivering a “robust” response in stimulating CD4 cells and antibodies.
The HVTN 505 trial is testing a multiclade (includes different sub-types of HIV) DNA vaccine with an Adno booster (intended to stimulate the immune system). This Phase II trial started this year and will wrap up in 2012.
He also described new concepts around T-cell vectors (vaccines that stimulate cell-mediated immune response) and said this field was making advances. In particular he reported on the efficacy of the LCMV (a type of virus) at stimulating a powerful immune response in lab tests and he talked about a new generation of vaccines using the “mosaic” concept.
“On the T-cell side we can look forward to a lot of improvements,” he indicated.
Nabel said progress has been made on stimulating antibody immunity, guided by the analyses of blood from people who successfully generate broad neutralising antibodies.
“These individuals can serve as a guide to vaccine development,” he said.
Nabel emphasised the need to find new ways to measure immunity that will correlate (show a link to) protection against HIV and the important the window of opportunity to stop HIV as soon as it infects the cervix.
HIV vaccine scientists have been fighting an uphill battle for 25 years searching for a way to block the rapidly mutating virus.
Now a new approach to finding a vaccine has shown potential, the results of which are published this week online by Nature
Scientists at the the Rockefeller University in New York said they have identified “a diverse team of antibodies in ‘slow-progressing’ HIV patients.
“(Their) coordinated pack hunting knocks down the virus just as well as their super-antibody cousins fighting solo”.
Several HIV vaccine studies so far have focused on the ‘Famous Four’ — a few powerful, engineered antibodies that block a protein (gp140) HIV needs to infect immune cells.
But efforts to jolt the human body into producing them have failed.
Lead scientist of this research Michel Nussenzweig, head of the Laboratory of Molecular Immunology at Rockefeller University, said: “We wanted to try something different, so we tried to reproduce what’s in the patient.”
The team isolated 433 antibodies that “specifically targeted the envelope protein (gp140)”.
They cloned these antibodies and identified which part of gp140 these antibodies neutralised, and how effectively.
Nussenzweig said these antibodies have limited impact individually but as united teams they were “quite powerful” — and could shed light on how to develop an effective vaccine.
The latest research suggests that “an effective HIV vaccine may come from a shotgun approach using of a wide range of natural antibodies rather than an engineered magic bullet”, reports EurekAlert.