HIV-1, the virus that causes AIDS, remains a potent global threat, especially in sub-Saharan Africa and other low-income areas. And while new treatments over the past 40 years have greatly improved the prognosis for those infected, prevention of HIV-1 infection by vaccines or immunoglobulins is not yet established.

That may change with a finding at the Southwest National Primate Research Center (SNPRC) in San Antonio, Texas. A team led by Dr. Ruth Ruprecht has shown for the first time that an antibody called Immunoglobulin M (IgM) can be effective in preventing infection in the mucosa after exposure to the virus. This is significant because an estimated 90% of new HIV-1 cases are caused through exposure in the mucosal cavities such as the lining of the sexual organs or rectum.

Rhesus monkeys at the SNPRC on the campus of the Texas Biomedical Research Institute were treated with a man-made version of IgM. Thirty minutes later, the same animals were exposed to simian-human immunodeficiency virus, a hybrid virus containing elements of the monkey and human immunodeficiency virus. Four of the six animals treated this way were fully protected against the virus.

“IgM can grab multiple particles like HIV-1 and SHIV very quickly and does not let go,” said Dr. Ruprecht. “Our study reveals for the first time the protective potential of IgM. It basically opens up a new area of research – IgM can do more than it has been given credit for.”

IgM, which had been thought by most scientists to have too short-lived a protective effect, may now lead the way to an effective barrier against HIV-1 infection.