研究発表を行った学会；第５回　熊本エイズセミナー　（国際シンポジウム）
２００４年９月９日〜９月１０日（熊本）
タイトル；Involvement of C3 mutation in neutralization sensitivity of HIV-1 for anti-V3 antibodies.
発表者；柴田　潤二　氏
　　　（熊本大学　エイズ学研究センター　病態制御分野）
Abstract；
Background
It has been reported that some primary isolates of HIV are resistant to antibody-mediated neutralization despite conservation of the binding epitopes. However, the mechanism of the neutralization resistance has not been elucidated. We have reported that some mutations in upstream C3 domain of gp120 induced resistance to neutralization by autologous antibody.

Methods
In order to elucidate the epitope responsible for neutralization resistance conferred by mutation in C3 domain of gp120, we constructed pseudotype viruses which had luciferase gene and chimeric envelope sequences derived from pretreatment or rebound viruses of the same patients and tested the changes in the reactivity and neutralization sensitivity against a panel of neutralizing monoclonal antibodies by neutralization assay and flow cytometry.

Results
There was significant difference in neutralizing sensitivity to anti V3 monoclonal antibody between the pretreatment and rebound virus despite the two have the same V3 epitope. We then tested the neutralization sensitivity of pseudotype virus that has a chimeric envelope of upstream C3 region from the sensitive virus in the backbone of resistant virus. We found that the neutralization resistant virus became sensitive to anti V3 antibody by exchanging upstream C3 region. We next examined the binding activity of anti V3 antibody to the surface of envelope expressing cells by flow cytometer. Mean fluorescence intensity (MFI) obtained with neutralization sensitive envelope expressing cell was higher than mutant or resistant ones.

Conclusion
These results suggest that the mutations in C3 region of envelope render neutralization resistance against anti-V3 antibody by altering the accessibility for antibody binding. As a result, HIV may escape from neutralizing antibody without changing V3 epitope which is important for viruses to bind to chemokine receptors.