Ruth Ruprecht said IgM has a high affinity for its antigens (Representational)

Scientists have discovered a promising class of forgotten antibodies which may offer protection against HIV-1 virus.

The antibody called Immunoglobulin M (IgM) -- which is naturally produced by plasma cells located under the surface lining of body cavities -- was effective in preventing infection after mucosal AIDS virus exposure, the researchers found.

IgM resulted in what is called immune exclusion. It lumped up the virus, preventing it from crossing the mucosal barrier and spreading to the rest of the body.

"IgM is sort of the forgotten antibody. Most scientists believed its protective effect was too short-lived to be leveraged as any kind of protective shield against an invading pathogen like HIV-1." said lead author Ruth Ruprecht from Texas Biomedical Research Institute in the US.

The team treated Rhesus monkeys with a man-made version of IgM.

Half an hour later, the same animals were exposed to SHIV (simian-human immunodeficiency virus) and were then monitored for 82 days.

The findings, published in the journal AIDS, showed that four out of the six animals treated using IgM were completely protected against the virus.

Ms Ruprecht said IgM has a high affinity for its antigens. It grabs them very quickly and does not let go.

"Our study reveals for the first time the protective potential of mucosal anti-HIV-1 IgM. IgM has a five-times higher ability to bind to virus particles compared to the standard antibody form called IgG. It basically opens up a new area of research. IgM can do more than it has been given credit," Ms Ruprecht added.