Researchers at the University of Alabama at Birmingham (UAB) have confirmed initial findings that a unique HIV vaccine formula is effective in eliciting strong and balanced immune responses.
Their study built on a previous study wherein experts at Advanced BioScience Laboratories and University of Massachusetts Medical School tested the vaccine formula on healthy human volunteers.
In the current study, published in the Journal of Virology, the UAB researchers carried out further assays on samples taken from the same volunteers who participated in the previous study.
The team says that their study confirms the presence of long lasting and high quality T cell responses against HIV antigens.
The phase I clinical trial, sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), saw volunteers receive their injections of a DNA vaccine which expresses protective antigens from the HIV virus, followed by two injections of a protein vaccine whose components matched those included in the DNA vaccine.
A research article on the trial conducted by scientists at ABL and UMMS appeared in the journal Virology, saying that a "DNA prime-protein boost" combination vaccination method seemed to be highly effective in inducing strong antibody and cell-mediated immune responses in human volunteers.
"Given the challenges of developing a vaccine against HIV, scientists have long believed that a final, effective HIV vaccine will require the induction of balanced responses from both arms of human immune system. Our results demonstrate that it is feasible to use this combination approach to achieve this objective," said Dr. Phillip Markham of ABL, the Principal Investigator (PI) on this vaccine development effort.
One unique design underlying this combination HIV vaccine formulation is the use of a "cocktail" of five different envelope (Env) proteins, key protective antigens, collected from HIV viruses circulating in different parts of the world.
The objective behind the study was to elicit broad antibody responses against a wide range of HIV viruses in order to counter the issue of frequent HIV mutations.
Indeed, the high titer antibodies found in volunteers' sera were able to recognize each of a very diverse group of Env antigens that were included in the study.
The majority of participants developed positive neutralizing antibodies against a good portion of the five HIV subtypes included in the assay.
Dr. Shan Lu, professor of medicine and biochemistry and molecular pharmacology at the University of Massachusetts Medical School and the co- Principal Investigator (co-PI) of the vaccine development program, said that the finding of neutralizing antibodies in the study was "a major step forward."
"Previously, we didn't know where to start. The neutralizing antibody titers in our study are still relatively low, but, these results are promising and open the door for future efforts to optimize HIV vaccine formulations in order to achieve a protective HIV vaccine," said Dr. Lu.
The dominant approaches in the current HIV vaccine field rely on viral vector-based delivery systems, an approach that produced disappointing results in a recent efficacy trial.
Drs. Markham and Dr. Lu said that their HIV vaccine strategy might offer an alternative approach to focus on the induction of protective antibodies for HIV vaccine development, while maintaining strong cell-mediated immune responses.