In findings illustrating the difficulty of developing an AIDS vaccine, UCLA AIDS Institute researchers report the immune systems in two HIV-positive identical twins responded to the infection in different ways. Detailed in the Dec. 5 issue of the peer-reviewed Journal of Virology (http://jvi.asm.org), the findings show that the body’s defenses against the virus are random rather than genetically determined. The researchers followed the cases of male twins who were infected shortly after their 1983 births in Los Angeles by blood transfusions administered from the same donor at the same time. Infected with the same strain of the virus, the twins continue to live in the Los Angeles area and grew up exposed to the same environmental forces. Yet their T-cell receptors (TCR) reacted differently in each twin, showing that the body’s defense response was random--and unpredictable. TCRs play an important role in the immune system by binding viruses and other antigens to receptors on their surface, killing the invader. HIV escapes this action by changing shape so that it does not fit into those receptors.
