"Changing this one amino acid in HIV to resemble variants found in SIV enhanced the entry of SHIVs into monkey CD4 T cells by a thousand-fold," Li said.
Moving quickly forward on the heels of this discovery, Li and Shaw have created a set of "designer SHIVs" that contain HIV envelopes of particular research interest.
"These results have given us hope that the new SHIVs will indeed be a game-changer for HIV vaccine research," Shaw said.
Now, Shaw, Li, and their colleagues have found a way to overcome these obstacles and to make a much better SHIV -- one that closely mimics HIV infection in humans.
In the PNAS study, Li and Shaw hypothesized that changing the binding affinity of the HIV envelope to rhesus monkey CD4, the primary receptor for HIV, would be the key to successful SHIV design.
"We identified rhesus macaque CD4 binding as a critical determinant for productive SHIV infection in the monkeys and Env375 mutations that influence this," Shaw said.