Microbes to effectively respond to vaccines: which and how many

For years, the scientific community has been studying the trillions of micro-organisms that colonise our bodies from birth. The composition of this group of microorganisms can change over the course of a lifetime and as a result of different environmental factors around us, ranging from what we eat to whether we were born vaginally or by caesarean section. These factors can be key, as the number and types of microbes that make up each person's microbiome can be determinant for the development and course of some diseases, as well as for the response to vaccines or treatments, among others. In this sense, the IrsiCaixa AIDS Research Institute –a centre jointly promoted by the "la Caixa" Foundation and the Department of Health of the Generalitat de Catalunya– is studying the microbiome of people who respond better to the HIV vaccine than those who do not, in order to predict who will respond successfully to this cure strategy. These will be some of the points to be discussed at the International Human Microbiome Consortium Congress 2021 (IHMC2021), a world-leading congress that will be the meeting point for more than 500 experts from 36 different countries, in which all the applications of the microbiome in human health will be debated.

This is the first time that the city of Barcelona has hosted this congress after the International Human Microbiome Consortium (IHMC) assigned the scientific coordination to Francisco Guarner, from the Digestive System Research Unit of the Vall d'Hebron Hospital Research Institute, and assigned the organisation to FLS-Science and IrsiCaixa. The congress, which this year celebrates its eighth edition, will take place on 27, 28 and 29 June in virtual format, and will begin with an inaugural talk by Guarner himself, Àngel Font, corporate director of Research and Strategy of the "la Caixa" Foundation, the congress sponsor, and Bonaventura Clotet, director of IrsiCaixa. Even if attendees connect from home, they will be able to access the 140 presentations of the congress by entering the Universe Room of the CosmoCaixa, where the congress will be hosted virtually, offering a 3D experience to users.

Microbes and vaccines

The bacteria that constitute the microbiome can have very diverse functions, and many of them are related to the regulation of the immune system, which is responsible for fighting diseases or responding to vaccines, among others. "It is possible that, depending on the composition and functions of the microbes we have, our defences react in one way or another when a vaccine is administered", explains Roger Paredes, principal investigator of the Microbial Genomics group at IrsiCaixa. Although the 'ideal' microbiome for responding well to vaccines is still unknown, the scientific literature of recent years shows that there is no exact recipe and that the combination of microbes required may be different depending on the vaccine administered. In the case of tetanus, for example, it has been shown that people who have more bacteria of the actinobacteria family in their faeces are able to have a stronger immune system response against the vaccine administered.

"IrsiCaixa is conducting a pilot study to understand the difference between the intestinal microbiome of people who respond successfully to the HIV vaccine and those who do not", says Alessandra Borgognone, postdoctoral researcher at IrsiCaixa who will give one of the four talks at the CaixaResearch symposium. The study will be the basis of MISTRAL, a European project coordinated by IrsiCaixa with funding of almost 10 million euros. "These results would make it possible to use the intestinal microbiome as a potential marker of response to the HIV vaccine, that is, to predict through the study of faeces who has the most favourable conditions to activate the immune system and control the virus", she adds.

The microbiome, as unique as the fingerprint

Hundreds of environmental and body factors can influence which bacteria, viruses, fungi or archaea make up the microbiome, as well as which functions each of these microorganisms performs. The neonatal stage is a turning point in the creation of the microbiome. "Gestation and the first days after birth are crucial for the baby's microbiome. Childbirth, in fact, is the primary mechanism for microbiome transfer in mammals, as it is the first major exposure to a complex set of microorganisms", explains Guarner, who is also the moderator of the IHMC 2021 neonatal microbiome session.

Another main key factor in determining the composition of the microbiome is the diet. Previous studies have shown that a varied and fibre-rich diet, such as the Mediterranean diet, is important for a diverse and functionally balanced map of microorganisms. In fact, the metabolites produced by the gut microbiome –which are determined by the diet– can influence the energy balance of each individual. In addition, the composition of microorganisms can change people's food preferences. These two aspects will be explained at the Caixa Research Symposium, by Sonia Fernández Veleda, from the Pere Virgili Health Research Institute Foundation of the Joan XXIII University Hospital of Tarragona, and Carlos Ribeiro, a researcher at the Champalimaud Foundation in Portugal, respectively.

Francesca Crovetto, researcher at BCNatal, will explain, in this symposium, a study in which two of the factors that influence the composition of the microbiome converge: diet and the neonatal stage. She will do so by commenting on the results of her study, which show that reducing stress or having healthy eating habits can drastically change the microbiome of the newborn.

"Understanding which and how many bacteria are ideal in each context would allow us to find strategies to modify the microbiome in order to have better responses to vaccines or treatments, for example", concludes Bonaventura Clotet, director of IrsiCaixa and researcher on the scientific committee of the congress.

Who makes IHMC2021 possible?

The organisation has counted on the support of FLS-Science and sponsors who have made the congress possible. The platinum and gold sponsors are "la Caixa" Foundation and Danone Nutricia Research, respectively. Silver sponsors include Abbott Laboratories, Biofortis Mérieux NutriSciences, DNA Genotek and Sanofi. Finally, bronze sponsors include AB-BIOTICS, Bayer Steigerwald Arzneimittelwerk, Biose Industrie, Canadian Institutes of Health Research (CIHR), Clinical Microbiomics, Ferring International Center, MetaGenoPolis INRA, Merck Sharp & Dohme Corp., MicroViable Therapeutics, Societe des Produits Nestle, Nexbiome Therapeutics, Pharmabiotic Research Institute (PRI) and Vaiomer. In addition, Phase Genomics, Soho Flordis International (SFI), Vedanta Biosciences and Zymo Research Europe are supporting IHMC2021 with general sponsorship and Cambridge University Press as academic sponsor.