Microbes in the Rectum Might Be The Key to Effective HIV Vaccines

According to findings published in the journal mSphere, microbes living in the rectum may have benefits when it comes to the effectiveness of experimental HIV vaccines.

Researchers at the University of California, Davis sought to figure out whether microbes living in the rectum and vagina interacted with experimental HIV vaccines similarly to the HVTN 111 vaccine, an HIV DNA and protein vaccine currently in early stage clinical trials.

Researchers studied vaginal and rectal microbes before and after participants were vaccinated, and noted their effectiveness at producing antibodies. According to Smith Iyer, assistant professor at the UC Davis Center, vaccines that produce antibodies at the mucosal membranes where HIV transmission takes place (the rectum and vagina in this case) are crucial in preventing HIV contraction. 

Iyer’s team discovered that while vaginal microbes didn’t show much of a difference, rectal microbes revealed that Bacteroidetes-type bacteria, like Prevotella, decreased upon vaccination.

Participants with high levels of the gut bacteria Lactobacillus or Clostridia were shown to make more antibodies to the HIV proteins gp120 and gp140. However, Prevotella bacteria showed the opposite, and was correlated with weaker immune system responses.

Evidence suggested that Lactobacillus supplements were able to boost production of these antibodies, while antibiotics can actually inhibit positive immune responses.

According to a UC Davis report, it’s still not clear what needs to happen for some bacteria to boost immune responses, but targeting these bacteria might be important to get the best possible results from HIV vaccines that fail to produce a strong immune response.

The authors conclude that the microbiome could be an important factor to consider when evaluating vaccines, and it should not be overlooked.