AIDS and HIV Vaccines

AIDS or acquired immunodeficiency Syndrome is caused by human immunodeficiency virus (HIV). The World Health Organization (WHO) is an International Organization associated with the community health programs throughout the world and it is the reward of concerted efforts that the diseases like smallpox and polio have completely been eradicated through vaccination. Now the worldwide focus is on the development of an effective vaccine to control the spread of AIDS and providing prophylaxis to health professionals. An ideal HIV vaccine would be the one which could mount a good humoral and cell mediated immune response both locally and systemically. HIV is an enveloped virus that contains two copies of genomic ribonucleic acid (RNA). There is a glycoprotein of 120 kD molecular weight commonly known as gp120, through which the virus binds to the cellular receptors at the surface of T-helper lymphocytes or CD4⁺ cells. The binding of virus to the CD4 receptor in association with chemokine co-receptor causes a dynamic change in gp120 and further activates trans-membrane protein gp41. These changes cause fusion of HIV envelope to the cell membrane of CD4⁺ cell and further make way for the entry of virus into the cytoplasm of CD4⁺ cell, replicate there, destroy cell and infect new cells.

Experimental studies in animals have shown that a considerable amount of T-cell response can be induced with HIV vaccines thereby limiting the viral RNA levels in plasma and minimizing the destruction of CD4⁺ T-cells. The survival of CD4⁺ T-cells through vaccination might help control infection and prolong disease-free survival of immunized person. The HIV vaccine capable of controlling the viral replication may also reduce the secondary transmission since the progression of secondary transmission is directly related to the plasma viral load. The oldest procedure of vaccine development has been tried wherein live attenuated viruses are used as vaccine but could not be put to the practice in case of HIV vaccine due to danger of infection if the virus particle were not completely killed or attenuated. Novel strategies are being used wherein certain immunogenic viral peptides (non-infectious and genetically engineered) have been tried and put to clinical trials. HIV vaccines developed on the guidelines of viral vectors containing vaccines and DNA vaccines are under way of active clinical trials. The vaccine war is going on against HIV.