Protection without neutralization?

Most antibody-related talks at the meeting stressed the importance of broadly neutralizing antibodies for protection from HIV infection. But Olga Malykhina from Tom Hope’s lab at Northwestern University said that antibodies that just bind to HIV might be sufficient for preventing infection. 

She reported evidence that many IgG antibodies can bind to vaginal and cervicovaginal mucus, which traps them and keeps them from moving. (The antibodies seem to bind to mucus through their Fc receptor end.) If such mucus-binding antibodies can also bind HIV, they should already be able to prevent infection, Malykhina said, because the antibody-bound virus would be trapped in the mucus. “As long as [the virus] is trapped, it could be expelled from the genital tract,” she said, adding that perhaps the RV144 trial showed protection at least in part because of such mucus-binding antibodies. 

Malykhina and Hope are currently trying to better understand why some antibodies can bind mucus better than others. With this knowledge in hand, they say, one could develop a vaccine that preferentially induces types of IgG antibodies that can bind to mucus very well. 

Today was the last day of the meeting, a good time to ask some of the participants whether it was a good idea to hold the HIV Vaccines meeting together with a meeting of B cell biologists. Many said that the answer is yes. “It was very good to see the state of the art of B cell biology,” said Ruth Ruprecht of the Dana-Farber Cancer Institute in Boston. “What I loved was to see movies how lymph node follicles actually look like. To see the concepts actually in pictures was fantastic—really inspiring.” 

Oh, and there is one more thing I should mention. On Tuesday, Qingsheng Li of the University of Nebraska Center for Virology presented a detailed study of the dissemination of virus in rhesus macaques during the first 10 days after rectal transmission of SIVmac251. The study was impressive; but the reason I wanted to mention Li’s talk is because he also showed a picture of a bar in Vienna where you can have drinks inside a replica of the human gastrointestinal tract that extends all the way from the mouth to the anus. The bar’s name: Bar Rectum.