Study offers hope for reducing incidence of AIDS with potential preventive vaccine

The HIV epidemic is the largest in the world and represents one of the most serious public health problems, according to data from the World Health Organization (WHO). Only 30% of the more than 10 million patients in need have the access to the antiretroviral treatment. The total number of infected people exceeds 30 million and there are about 3 million new infections per year. The best hope for reducing the incidence of AIDS (Acquired Immune Deficiency Syndrome) is a preventive vaccine.

The most effective preventive vaccines act by inducing a response based on neutralizing antibodies. Some groups had shown that HIV-infected patients can produce a broad neutralizing response. But so far, all studies have excluded patients on antiretroviral therapy with undetectable viral load, i.e., having an improved profile compared to untreated patients.

To better understand the induction of neutralizing antibodies in these patients, researchers from IDIBAPS/Hospital Clinic of Barcelona, bound to the program HIVACAT (Research Project AIDS Vaccine), for the first time, have included samples of patients treated with a low level of viral replication. 508 samples were analyzed in 364 patients (191 treated and 173 with no antiretroviral treatment) through a new strategy based on the use of recombinant viruses.

The study represents the first big test and evaluation of the neutralization in HIV-infected persons with undetectable viral load. "We have shown that patients receiving antiretroviral treatment are able to induce a broad and strong humoral immune response (broad-spectrum neutralizing antibodies) for HIV despite having undetectable viremia", says the last author of the study, Eloisa Yuste. In these patients, the low level of antigenic stimulation may be compensated by an improved B cell function induced by antiretroviral treatment.

The report concludes that the percentage of treated and untreated patients that generated broad-spectrum neutralizing antibodies was very similar: 2.3%. This is the first step in identifying the epitope able to induce the development of these antibodies and therefore would be an excellent candidate for potential AIDS preventive vaccine based on the development of broad-spectrum neutralizing antibodies. This is how other highly effective preventive vaccines such as them against human papillomavirus, hepatitis A and B and polio, among others.

Neutralizing antibodies do not work when HIV infection is already established. But their presence induced by a vaccine could prevent infection if an uninfected person comes in contact with the virus. So, the next step is to get the induction of broad-spectrum neutralizing antibodies are generated in patients who have not acquired the virus. "The next stages of the research will characterize these broad-spectrum neutralizing antibodies and identify the virus that has led and could serve as a potential preventive vaccine in healthy people", she concludes.