Science Highlights Aids Vaccine 04

Understanding protection correlates

Today, one of the major focuses in HIV research consists in understanding how our immunity is stimulated by a vaccine and how the latter enables our body to defend itself. In technical terms, these are called "protection correlates" . New discoveries have been made in this field and some will be presented at the AIDS VACCINE 2004 conference. While cytotoxic CTL cells (CD8+) are indispensable for killing cells infected by HIV, these cells lose their cytotoxic capacity when the virus replicates continually. They become exhausted. Researchers have recently discovered that certain molecules and cells in our body precede and preserve the eliminating activity of CTLs. For example, T CD4+ lymphocytes secrete interleukin-2 (IL-2), an immune system regulating factor which seems to have a crucial role in controlling the proliferation of HIV.

Renewal in the search for HIV neutralising antibodies

Because HIV mutates so rapidly, and the targets at which antibodies are directed are often hidden or folded in on themselves, research for a "humoral" vaccine has slowed down in recent years. Indeed, researchers have progressively moved away from trying to provoke an immune reaction (humoral) that seeks to produce antibodies that can neutralise the virus, instead pursuing more actively the option of creating so-called cellular immunity. However, recent research has moved current thinking in HIV vaccine research to revisit the idea and clinical studies will be looking at how antibodies can fix themselves on HIV and thus efficiently block its entry into host cells, thereby facilitating its elimination.

Hopes for a "prime boost"

Contrary to classical vaccine boosters, a new strategy is being developed comprising two different "antigen transporters" (vectors). A first dose of antigen A in vector X is administered, followed by a booster using the same antigen A in vector Y this time. In this way, immune reactions to, and the consequent destruction of, the transporter are reduced. The first injection wakes up ("primes" ) the immune system, the second "boosts" it. This has been developed since single administration does not seem to offer efficient protection against HIV.

However, researchers still need to identify the best candidates for the "prime" and the most efficient for the "boost" . During AIDS VACCINE 04, the results of several studies will be presented. Given the results of some Phase I studies, it would appear that the use of "naked" DNA as prime followed by a boost based on poxvirus or adenovirus has proven its immunogenic efficacy. "Prime-boosting" is promising; some combinations will move into Phase II.

An increased understanding of biological mechanisms coupled with the development of new anti-HIV vaccines will not be sufficient to fight the pandemic without increased collaboration within the scientific and medical community. Global collaboration implies that every sphere of activity, from politics to industry, must support the global effort of researchers to find a vaccine against HIV, regardless of frontiers. Emerging countries must be involved and supported in the fight against AIDS. Current treatments are expensive and inaccessible to the majority of the world's population. International assistance is therefore indispensable in order to reach the best means of prevention of HIV: a vaccine.

The AIDS vaccine '04 conference is attended by about 800 scientists and features the most significant advances in the field. The Conference is co-organised by the Lausanne University Hospital (CHUV) and EuroVacc, a foundation registered in Switzerland whose mission is to develop a vaccine against human immunodeficiency virus (HIV) and other agents of human infectious diseases.