Monkeys repeatedly immunized with a particular form the HIV-1 envelope glycoprotein generated antibodies capable of neutralizing diverse strains of HIV-1, according to a paper published online in the Journal of Experimental Medicine on August 2.

Antibodies in the blood of monkeys immunized with a HIV-1 envelope trimer neutralized a broader variety of HIV-1 strains than antibodies in the blood of humans immunized with an HIV-1 envelope monomer during the VAX04 phase III clinical trial.

However, the immunized monkeys showed only weak protection against subsequent rectal infection with a simian HIV virus. This weak protection may be due to the fact that neutralizing antibody titers were at least 1,000-fold lower in rectal and vaginal tissues than in the blood.

These findings suggest that methods to boost neutralizing antibody abundance in rectal and vaginal tissues might be needed to better prevent HIV-1 transmission.