Researchers find peptite that promotes HIV infection in simians

Boffins conducting a recent research have found a peptite that promotes HIV infection in simians.

The study, conducted by UCLA AIDS Institute researchers has revealed that when a vital portion of a peptide structure in monkeys, that defends against viruses, bacteria and other foreign invaders, is reversed the peptide in fact encourages infection with HIV.

The findings, published in the April issue of AIDS Research and Human Retroviruses, could lead to the use of such peptides in gene therapy using HIV-based vectors as the delivery method.
"Although it may seem counterintuitive to value or even study a peptide that increases the ability of HIV-1 to enter a broad range of human cells, retroviral vectors are currently being explored as vehicles for gene therapy," the authors wrote. "In this area, at least, agents that enhance retroviral uptake could contribute to an emerging field of medicine."

"So many people have tried to deliver genes into different kinds of cells. If you know of some method that can enhance gene delivery, you would have a useful tool," said study co-author Shen Pang, adjunct associate professor at the UCLA School of Dentistry and a member of the UCLA AIDS Institute.

Retrocyclin-1 (RC-100) is a spherical peptide that has been shown in earlier studies to slow down the infection of CD4 cells with HIV. RC-111 is also recurring and has the same amino acid sequence as retrocyclin-1. In both peptides, the amino acids are strung like 18 beads along the molecule's backbone. The amino acids in RC-111, however, are in reverse order.

At first the researchers wanted to enumerate previous research by Dr. Robert I. Lehrer, eminent professor of medicine in the division of infectious diseases at the David Geffen School of Medicine at UCLA and a co-author of the present study.

Surprisingly, the researchers discovered that while retrocyclin-1 repressed infection of CD4 cells with HIV-1 by about 95 percent, the RC-111 variant enhanced viral infection five-fold.

There are three structural varieties of peptides, also known as defensins, alpha, beta and theta, Lehrer said. Humans have only alpha and beta, while monkeys have all three.

"Here's a peptide whose normal structure allows it to protect against viruses, yet if you make the same peptide and place its amino acids in a reverse order, that lets the virus in," Lehrer said. "We would like to learn why it happens, but at the moment there's no explanation for this paradoxical result."