Scientists at the Texas Biomedical Research Institute have found a promising new type of defense against the virus that can cause AIDS.
A team led by Dr. Ruth Ruprecht, director of the institute’s AIDS research program, for the first time has demonstrated that an antibody called Immunoglobulin M (IgM) is effective in preventing AIDS virus transmission.
The Texas Biomed team’s findings are outlined in a study published earlier in July in the scientific journal AIDS.
Researchers at the far West Side institute gave six rhesus monkeys at the Southwest National Primate Research Center a man-made version of IgM. Thirty minutes later, the researchers exposed the same six monkeys to a hybrid simian-human immunodeficiency virus (SHIV), which carries the envelope gene of the human immunodeficiency virus (HIV), the human AIDS virus.
Four of the six monkeys were fully protected from SHIV infection because the IgM blocked the virus from entering the animals’ bloodstream.
“This landscape has completely changed,” Ruprecht told the Rivard Report, describing her field of work.
All vertebrate animals have IgM, a large antibody molecule, and IgM is the first antibody produced to respond to an infection. IgM is naturally produced by plasma cells beneath the surface lining of body cavities.
Although much research has been conducted with immunoglobulin G (IgG), which is five times smaller than IgM, there had been practically no prior research involving IgM and its interaction with HIV or related AIDS viruses.
“I looked at my team and asked, ‘Why don’t we address this?’” Ruprecht said.
The Texas Biomed team focused on warding off infection following AIDS virus exposure through a mucous membrane. An estimated 90 percent of new HIV-1 cases worldwide are caused through exposure in the mucosal cavities, such as the inside lining of the vagina or rectum.
“It seemed logical to mobilize as many mucosal defenses as possible if 90 percent of new HIV infections among people occur through mucosal exposure,” Ruprecht said.
The Texas Biomed team cloned the IgM antibody from an IgG antibody. In the lab, researchers saw IgM effectively neutralize the hybrid virus, SHIV, thanks largely to its ability to effectively capture virus particles.
“This strength is mainly due to IgM’s size and structure,” Ruprecht said.
After the monkeys were given the antibody followed by exposure to the virus, they were monitored for 82 days.
In the four protected monkeys, IgM antibodies caused immune exclusion, which involves binding of IgM to the virus and forming clumps, thereby keeping it from crossing the mucosal barrier and spreading to the rest of the body.
The technique of introducing pre-formed antibodies into the body to produce immunity is known as passive immunization.
The significance of the Texas Biomed discovery was emphasized in an AIDS journal editorial: “This study is important because the role of IgM in neutralizing virus infections has long been neglected.”
The breakthrough is timely. The annual International AIDS Conference is taking place in Amsterdam this week. Ruprecht said she hopes research locally and beyond will help answer questions, such as how to induce long-lasting IgM responses with a vaccine to directly fight HIV-1 and other viral infections.
Ruprecht added that the primate research center, based at the Texas Biomed campus, will be key in continuing AIDS research.
“It’s in the right place at the right time,” she said.
Ruprecht urged people to realize the AIDS epidemic is still problematic since the disease first became widely publicized in the early 1980s.
The Centers for Disease Control announced in June that annual HIV infections and diagnoses are decreasing nationwide overall, but that yearly infections and diagnoses have increased among some specific groups.
Between 2011 and 2015, HIV diagnoses went up 14 percent among Hispanic/Latino gay and bisexual men nationwide. Texas has the third highest population of HIV-positive individuals in the nation.
“This isn’t a good trend, and many people don’t realize it doesn’t have to be this way,” Ruprecht said.
Knowing one’s own HIV status through testing is critical, she said, as is treatment of HIV-positive individuals with antiviral drugs to prevent the virus from destroying the immune system and causing AIDS.