Phase I AIDS vaccine trial begins

The Vaccine Research Center (VRC) at the US National Institute of Allergy and Infectious Diseases in partnership with the US company GenVec recently began a Phase I clinical trial to evaluate the safety and immunogenicity of a novel adenovirus serotype 35 (Ad35)-based AIDS vaccine candidate in 15 volunteers. Adenovirus can cause some forms of the common cold and there are several serotypes circulating worldwide. Another adenovirus serotype, known as Ad5, is already being used as a vector in other AIDS vaccine candidates to deliver pieces of HIV to the immune system (see September 2004 Primer on Understanding Viral Vectors). Ad5-based vaccine candidates are now being tested in a series of Phase II trials by the VRC and in two large Phase IIb trials by the US company Merck. However one possible drawback to candidates that use Ad5 as a vector is the high prevalence of the virus in certain parts of the world. People who have been previously exposed to Ad5 may have pre-existing immunity towards the viral vector, and that could hinder their immune responses to the AIDS vaccine candidate. The potential advantage of using Ad35 is that it has a much lower prevalence globally.

This two-part trial is the first to test another serotype of adenovirus in clinical trials. The first part will evaluate the safety of an intramuscular injection of the vaccine candidate at three different doses. Once the safety data is reviewed researchers will evaluate the safety and immunogenicity of the candidate when administered in combination with the VRC's Ad5 candidate. The Ad35 vaccine candidate was developed by the VRC and GenVec.

All articles written by Kristen Jill Kresge