vaccines

HIV vaccine failed because of interaction with microbiome

Scanning electron micrograph of HIV-1, colored green, on a lymphocyte.

Scanning electron micrograph of HIV-1, colored green, on a lymphocyte.

From 2009 to 2013, scientists at Duke University and the National Institute of Allergy and Infectious Diseases had been working on what looked like a promising cure to HIV. The study was terminated in 2013 because it was clear that the vaccine was not effective in protecting against HIV infection. An article recently published by Science Magazine gave insight into why the HIV vaccine unfortunately failed. Hint: it has something to do with the microbiome.

The vaccine was administered in the study to adult males in the form of an initial vaccine as well as a second booster vaccine. The HIV vaccine looked promising because it stimulated the body’s immune system to produce antibodies that recognize HIV. The unexpected result, however, was that these antibodies also recognized bacteria like Escherichia coli, a very important bacteria that lives in the human gut. It should be easy to see why this is a bad thing for the microbiome. Destroying important gut bacteria is very detrimental to humans, which we see over and over again here on the blog. Additionally, because the antibodies were reactive to bacteria as well as the HIV virus, it took away from the effectiveness of fighting HIV.

This study is very important in the search towards finding a cure to HIV, because it presented an unexpected obstacle that a lot can be learned from. Moving forward, questions are already being raised by the scientists such as, would this vaccine work for children if immunization was given to pregnant mothers? Perhaps the still-developing immune system would better be able to work with the vaccine. Only more research can prove whether the HIV vaccine is indeed still promising.  In addition, this may provide insights into the efficacy of vaccines for other diseases.  Perhaps the microbiome plays a large role in their effectiveness.  Vaccine research going forward should begin to take the microbiome into account.

Please email blog@MicrobiomeInstitute.org for any comments, news, or ideas for new blog posts.

The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.

Gut bacteria protect against malaria transmission

Malaria is a deadly disease transmitted through mosquitoes and most widespread in tropical and subtropical regions around the world, especially in Africa. According to the Center for Disease Control and Prevention (CDC), 627,000 people died in 2012 and there were a total of 207 million cases worldwide. Through studying the microbiome, scientists last week published a major discovery in Cell that may lead to better vaccinations for malaria that could help prevent the disease from being transmitted.

Scientists in Portugal, collaborating with colleagues in the United States, Australia, and Mali, found that the parasite the causes malaria, Plasmodium, expresses the same sugar molecule that is seen in a type of Escherichia coli (E. coli).  This sugar molecule from the E. coli called alpha-gal (a-gal) results in the body’s immune system producing antibodies against this molecule and therefore also protecting against the malaria parasite. It is known that adults who are exposed to malaria are at lower risk of contracting the disease than children under the age of 5 and the researchers hypothesized that this was due to the children lacking this specific E. coli in their body and therefore unable to fight back against Plasmodium exposure.   

The scientists studied the gut bacteria of a group of individuals in Mali who had very high rates of malaria transmission. They found that those who had higher levels of anti-a-gal antibodies had lower risk of transmitting malaria and those with low levels of these antibodies had greater risk of transmitting the disease.  This showed that children are at greater risk for the disease because they do not produce enough anti-a-gal antibodies to prevent the parasite from infecting the body.

The scientists also found that the transmission of the parasite is blocked almost immediately following its introduction into the body through the skin. The antibodies against a-gal attach to the Plasmodium as soon as it is exposed to the body, and a part of the immune system called the component cascade is activated, killing the parasite before it can leave the skin and reach the blood stream.   

They found that by vaccinating mice against a kind of a-gal, the mice produced enough anti-a-gal antibodies that were highly efficient in protecting the mice from malaria transmission.  The scientists believe that it may now be possible to translate this work to humans and develop vaccines that would increase anti-a-gal antibodies and prevent malaria transmission. If successful, vaccinations could be given to children who are at high risk for the disease and could prevent hundreds of thousands of deaths every year.  These findings also illustrate the protective aspects of the microbiome in regulating immunity, and the potential treasure-trove of molecules produced by the microbiome that could be used in therapeutics.

Please email blog@MicrobiomeInstitute.org for any comments, news, or ideas for new blog posts.

The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.

The microbiome may affect vaccination efficacy

We know that vaccines are often not as effective in developing nations as they are in industrialized nations and a recent study published in September in Immunity may provide insight into why this discrepancy exists.  Researchers in the US and Brazil examined a possible link between the microbiome and the effectiveness of vaccines. 

Previous research had shown that expression of TLR5, a cell-surface receptor for bacterial flagellum, correlates with TIV (a popular flu vaccine) vaccination antibody response in humans. In this study, researchers observed this correlation between TLR5 expression and the immune response from the TIV vaccine through a series of experiments.

First, researchers found evidence to suggest that the correlation between TLR5 and antibody response is not because of any kind of contamination in the vaccine. They also saw a significant decrease in antibody response in mice with a mutated TLR5 gene, when they were given the TIV vaccine, even though they showed no prior immunodeficiency. Other evidence was found to suggest that the gut microbiome is necessary for a rapid antibody response after vaccination, because the response of antibody secreting cells depends on the microbiome. Research also suggested that multiple types of bacterial communities are necessary, and not just a few specific species, for gut bacteria to mediate immune responses. 

These findings of the microbiome’s role on the effectiveness of a vaccine in inducing an immune response could impact future vaccine development. Further research may be done to better understand the role that diet, health, and other factors that affect the human microbiome play in vaccine response. Microbiome differences between individuals in developing nations and those in industrialized nations could play a significant role in the efficacy of existing and future vaccines.  

Please email blog@MicrobiomeInstitute.org for any comments, news, or ideas for new blog posts.

The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.