( to a first viral infection to suppress ...)HIV exploits competition among T-cells

to a first viral infection to suppress the creation of new immune cells in response to a second infection by a related strain. The second type of competition, immunodominance, occurs when several viral strains simultaneously infect one person. In this case, T cells compete to recognize the different strains. The winners ?the T cells that the body produces in mass quantities to fight the disease ?are the ones with the best overall record against the most recogniztable strains. Among the losers, however, there may be T cells that better control the other less recognizable, but still deadly, strains.

"Once the immune system chooses a winning set of T cells, it has a natural tendency to go with those cells when it's confronted by new strains of the same disease in the future," Deem said. "For HIV, which mutates rapidly, this is an Achilles' heel. We found a direct correlation between the level of competition among T cells and the rate at which the virus escaped."

Deem said one strategy to combat this effect would be to vaccinate against the strains of HIV that will inevitably evolve in the body in a manner that was designed to reduce immunodominance. One such strategy ?polytopic vaccination ?involves giving vaccines against different strains of the same disease simultaneously in different parts of the body. The approach capitalizes on the fact that different lymph nodes ?the sites where T cells compete to be chosen as the winners against a particular disease ?act as collection points for different parts of the body. Moreover, because it takes 4-5 days for T cells produced in a lymph node to begin to leave it, the possibility exists to set up simultaneous, independent competition against each of the multiple strains that will evolve by injecting each strain simultaneously so that they drain to different lymph nodes. In this case, no single T cell is chosen as a winner. Instead, a separate winner for each strain is picked in each affected lymph node befo
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Source:Rice University

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