Biology subjects

Moresi, C.

Publications and source records attributed to Moresi, C..

4 recordsLinked to original sources

bioRxiv2023

A rationally designed inactivated Salmonella Typhimurium vaccine induces strong and long-lasting immune responses in pigs

Salmonella enterica subspecies enterica serovar Typhimurium (S.Tm) poses a considerable threat to public health due to its zoonotic potential. Human infections are mostly foodborne, and pork and pork products are ranked among the top culprits for transmission. In addition, the high percentage of antibiotic resistance, especially in monophasic S.Tm, limits treatment options when needed. Better S.Tm control would therefore be of benefit both for farm animals and for safety of the human food chain. A promising pre-harvest intervention is vaccination. In this study we tested safety and immunogenicity of an oral inactivated S.Tm vaccine, which has been recently shown to generate an "evolutionary trap" and to massively reduce S.Tm colonization and transmission in mice. We show that this vaccine is highly immunogenic and safe in post-weaning pigs and that administration of a single oral dose results in a strong and long-lasting serum IgG response. This has several advantages over existing - mainly live - vaccines against S.Tm, both in improved seroconversion and reduced risk of vaccine-strain persistence and reversion to virulence.

immunology↗

bioRxiv2022

Microbiota colonization tunes the antigen threshold of microbiota-specific T cell activation in the gut

Harnessing the potential of commensal bacteria for immunomodulatory therapy in the gut requires the identification of conditions that modulate immune activation towards incoming colonizing bacteria. In this study, we used the commensal Bacteroides thetaiotaomicron (B.theta) and combined it with B.theta-specific transgenic T cells, in the context of defined colonization of gnotobiotic and immunodeficiency mouse models, to probe the factors modulating bacteria-specific T cell activation against newly colonizing bacteria. After colonizing germ-free (GF) and conventionally raised (SPF) mice with B.theta, we only observed proliferation of B.theta-specific T cells in GF mice. Using simple gnotobiotic communities we could further demonstrate that T-cell activation against newly colonizing gut bacteria is restricted by previous bacteria colonization in GF mice. However, this restriction requires a functional adaptive immune system as Rag1-/- allowed B.theta-specific T cell proliferation even after previous colonization. Interestingly, this phenomenon seems to be dependent on the type of TCR-transgenic model used. B.theta-specific transgenic T cells also proliferated after gut colonization with an E.coli strain carrying the B.theta-specific epitope. However, this was not the case for the SM-1 transgenic T cells as they did not proliferate after similar gut colonization with an E.coli strain expressing the cognate epitope. In summary, we found that activation of T cells towards incoming bacteria in the gut is modulated by the influence of colonizing bacteria on the adaptive immune system of the host.

immunology↗

bioRxiv2022

Combined oral vaccination with niche competition can generate sterilizing immunity against entero-pathogenic bacteria

Colonization of the intestinal lumen precedes invasive infection for a wide range of enteropathogenic and opportunistic pathogenic bacteria. Here we show that combining oral vaccination with engineered or selected niche-competitor strains permits pathogen exclusion and strain replacement in the mouse gut lumen. This approach can be applied both prophylactically to prevent invasion of non-typhoidal Salmonella strains, or therapeutically to displace an established Escherichia coli. Both intact adaptive immunity and metabolic niche competition are necessary for efficient vaccine-enhanced competition. Our findings imply that mucosal antibodies have evolved to work in the context of gut microbial ecology, by influencing the outcome of competition. This has broad implications for the elimination of pathogenic and antibiotic-resistant bacterial reservoirs, and for rational microbiota engineering.

microbiology↗

bioRxiv2022

Fitness advantage of Bacteroides thetaiotaomicron capsular polysaccharide is dependent on the resident microbiota

Many microbiota-based therapeutics rely on our ability to introduce a microbe of choice into an already-colonized intestine. However, we remain largely blind to the quantitative effects of processes determining colonization success. In this study, we used genetically-barcoded Bacteroides thetaiotaomicron (B.theta) strains in combination with mathematical modeling to quantify population bottlenecks experienced by B.theta during gut colonization. Integrating population bottlenecks sizes with careful quantification of net growth rates in vivo and in vitro allows us to build models describing the events during intestinal colonization in the context of gnotobiotic and complex microbiotas. Using these models, we estimated the decrease in niche size for B.theta colonization with increasing microbiota complexity. In addition, our system can be applied to mechanistically dissect colonization defects of mutant strains. As a proof of concept, we demonstrated that the competitive disadvantage of a B.theta mutant lacking capsular polysaccharide is due to a combination of an increased lag-phase before growth initiation in the gut, combined with an increased clearance rate. Crucially, the requirement for the B.theta capsule depended strongly on microbiota composition, suggesting that the dominant role may be protection from bacterial or phage aggression rather than from host-induced bactericidal mechanisms.

microbiology↗