AIDSWEEKLY Plus, 9 Sep 1996
Daniel J. DeNoon, Senior Editor

The findings may speed HIV vaccine development by identifying key epitopes for vaccine inclusion and by facilitating the testing of candidate vaccines.

"We observed statistically robust serum-isolate neutralization clusters," reported Philippe Nyambi of The Institute of Tropical Medicine, Antwerp, Belgium. "The possibility exists that these isolate-neutralization clusters may contain some specific amino-acid motifs which distinguish these clusters."

Nyambi reported the findings at the XI International Conference on AIDS, held July 7-12, 1996, in Vancouver, British Columbia, Canada.

Nyambi and colleagues tested sera from 14 individuals with HIV infection for their ability to neutralize a wide variety of HIV-1 isolates.

The 16 primary isolates studied included main-group (group M) subtypes A through H and an outlying-group (group O) strain.

The researchers mapped the "neutralization spectra" for each of the sera and for each of the strains.

"This analysis revealed eight serum-neutralization-spectra and isolate-neutralization-spectra clusters which did not correlate with the known genetic clades," Nyambi reported.

"Furthermore, three key HIV-1 isolates were identified which allowed us to predict the neutralizing antibody titers of each of the 14 sera to the remaining 13 HIV-1 isolates."

Predictions based on ability to neutralize one of the three key isolates were 90 percent accurate.

"Our method of analysis will facilitate the evaluation as well as the design of suitable HIV-1 vaccines that induce high-titer inter-clade cross-neutralizing antibodies," Nyambi concluded.

NCI researcher Peter Nara, co-chair for the AIDS conference session at which Nyambi spoke ("Humoral Immune Response"), noted that the study findings contribute to a new model of how the immune system responds to HIV.

"We are getting a picture now that a large number of antibodies made in response to infection are made to envelope, which is in at least two or three different forms," Nara said.

"We can generally surmise that a fair amount of antibodies that are made are binding but don't appear to be doing good things for the host, and may be directed to various immunodominant epitopes as part of a shunting process that this virus, as well as other pathogens, have evolved to decoy some of the immune responses. If this is true we are going to separate the wheat from the chaff with regard to functionality and vaccine design."

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