How HIV vaccine might have increased odds of infection

November 3, 2008

In September 2007, a phase II HIV-1 vaccine trial was abruptly halted when researchers found that the vaccine may have promoted, rather than prevented, HIV infection. A new study by a team of researchers at the Montpellier Institute of Molecular Genetics in France shows how the vaccine could have enhanced HIV infection. The study, lead by Matthieu Perreau, will be published online on November 3 of the Journal of Experimental Medicine.

The HIV-1 vaccine used in Merck's STEP trial relied on a weakened form of a common cold virus, Adenovirus 5 (Ad5), to carry bits of HIV into the body. Those bits would presumably trigger the immune system to fight off later infection with the virus. One worry about the Ad5 vaccine vector was that widespread immunity to adenoviruses might cause the vaccine to be ousted from the body before an anti-HIV response could develop. Yet three years after the trial began, researchers realized that more of the vaccine recipients who had prior immunity to adenoviruses had been infected with HIV than those without such immunity.

The new study shows how the presence of long-lasting Ad5-specific antibodies—generated during natural infections with adenoviruses—may have altered the immune response to the HIV vaccine. In the presence of antibodies from Ad5-immune individuals, HIV infection spread through cell cultures three times faster than without them. The antibodies tethered the Ad5-HIV vaccine to receptors on the surface of specialized immune cells, called antigen-presenting cells (APCs), thus facilitating entry of the vaccine into the cell. Once inside, components of the vaccine then activated these cells, allowing the APCs in turn to activate T cells. Since HIV prefers to infect active T cells, the virus was thus provided with more cells to infect.

Merck's vaccine may have made it to phase II trials because primates, used in the phase 1 trials, don't naturally come in contact with human adenoviruses, and therefore the potential problem went unrecognized.

Source: Rockefeller University

Explore further: Team devises a new method that could speed up vaccine development for HIV

Related Stories

Scientists jump hurdle in HIV vaccine design

May 26, 2017

Scientists at The Scripps Research Institute (TSRI) have made another important advance in HIV vaccine design. The development was possible thanks to previous studies at TSRI showing the structures of a protein on HIV's surface, ...

Study reveals new insight into susceptibility to pneumonia

May 3, 2017

A new research study of immune responses to pneumococcal vaccines, commonly given to people with compromised immune systems, young children and people over 65, has identified a type of immune cell which is important in generating ...

Researchers take an important step toward an HIV vaccine

May 17, 2017

Researchers from the University of Copenhagen have developed a strategy that can revolutionize vaccine design. The new strategy is used to develop vaccines that can prevent HIV infection and the development of AIDS.

Recommended for you

Study reveals how HIV virus destroys lung tissue

May 17, 2017

Up to 30 percent of HIV patients who are appropriately treated with antiretroviral therapies develop the chronic lung disease emphysema. New research from Weill Cornell Medicine investigators has uncovered a mechanism that ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.