A naturally occurring vaginal microorganism has been modified by investigators at Stanford University to inhibit HIV, and could have the potential to protect women from infection with HIV. The laboratory study is published in the early on-line edition of the Proceedings of the National Academy of Sciences of the USA.
Lactobacillus jensenii is found abundantly in the mucosal linings of the vagina. Previously published research suggests that even in an unmodified form the bacteria provides some protection against infection with HIV. Women with no, or low amounts of lactobacillus were found to be at higher risk of contracting HIV and other sexually transmitted infections than women with large amounts of the microorganism.
In the Stanford research, investigators created lactobacillus that secreted CD4 proteins. In the process of infection, HIV attaches itself to the CD4 molecule on immune cells. The investigators theorised that if HIV is captured by the CD4 secreted by lactobacillus, it would prevent HIV from infecting immune cells.
Genetically modified lactobacillus was shown in laboratory tests to reduce by half the number of immune cells infected by HIV. As vaginal transmission of HIV is relatively inefficient, such a decrease, say the investigators, could inhibit the transmission of HIV at both an individual and population level.
Further research involving cell models will, however, be difficult, as an acid which occurs in lactobacillus, and which provides protection against infections, kills cells. Good animal models for vaginal HIV transmission are also lacking, but early investigations involving monkeys have shown that the modified vaginal microorganisms grew well and were safe.
Should the research progress further, it is hoped to develop a discreet vaginal suppository that women could change on a regular basis to provide on-going protection against infection with HIV. The investigators are stressing how novel their research is, pointing out that although genetically modified bacteria have been used in vaccines to stimulate a strong immune response, their current approach was completely different. "We are trying to get the bacteria to directly bind and neutralise the pathogens themselves," said Dr Peter P. Lee of Stanford University School of Medicine.
Further information on this website
Chang T et al. Inhibition of HIV infectivity by a natural human isolate of Lactobacillus jesenii engineered to express functional two-domain CD4. Proceedings of the National Academy of Sciences of the USA, early edition, 2003.