HIV Vaccines

Introduction:
When HIV (Human Immunodeficiency virus) was discovered and established as the causative agent of AIDS in 1983-1984(1), the majority of people thought that vaccines against this HIV would be developed and applied rapidly. But, this was not going to happen in case of HIV as in AIDS, virus-induced immune response possess no ability to prevent re-infection and also not capable of slowing down the progression to disease. The development of an HIV vaccine took almost 30 years of intense laboratory and clinical work. And because of this intense work, today we are closer to develop an HIV vaccine but, it is difficult to predict the time when we have the vaccine that possesses sufficient efficacy for implementation in public health programs

Although it is a difficult challenge but it is not an impossible target to achieve. There has been the evidence that the early stages of transmission of HIV are susceptible to intervention of immune response (7).The first experiment involving the immunization of humans against HIV-Ι(a strain of HIV) begun in November 1986 involving a sufficient number of HIV healthy volunteers. In this experiment, vaccinia virus recombinant (V25) that expresses gp160 env at the surface of infected cells are applied. gp160 env are the determinants of HTLVΙΙΙB. The results of this experiment showed that immune response against HIV can be achieved in humans (8). Following this experiment, almost more than 256 clinical trials (phase Ι and phase ΙΙ) including over 44, ooo healthy volunteers have tested candidate vaccines against HIV (8-13). Of these clinical trials, only six candidate vaccines have achieved clinical efficacy. These six vaccines include

Then the focus of HIV vaccines turned on to Cytotoxic T-lymphocytes [8-13]. Because in immune system Cytotoxic T-lymphocytes play a significant role in controlling the levels of virus during the natural infection of HIV. So targeting CTLs has also been a preference for research and development of HIV vaccine (3). The development of HIV vaccine is a difficult challenge because of lengthy, time consuming and expensive clinical trials for testing HIV candidate vaccines (2). In spite of the difficult and enormous challenge, the recent success provide a way forward towards the development of vaccine against HIV (2).
Brief History of HIV vaccine development:
This section provides summary of some of the key events in the history of development and research of HIV vaccines (2, 15).
Sr. No Year Achievements
1. 1984 Discovery of HIV-Ι
2. 1986 Approval of first HIV-Ι vaccine for clinical trials
3. 1989 Development of simian immunodeficiency vaccine(SIV) that provide immunity in small group of