Obesity and vaccine response

Vaccines train immune cells to make antibodies and remember a germ later. A mouse study published April 13 found obesity weakened both parts of that response against a *Pseudomonas aeruginosa* vaccine. (pmc.ncbi.nlm.nih.gov) The study tested a nanoemulsion protein subunit vaccine called L-PaF/ME/BECC in mice fed three diets: high-fat feed with 60% fat, low-fat feed with 10% fat, and regular chow with 3% to 4% fat. The obese, high-fat group showed lower IgA, IgG1, and IgG3 antibody levels after vaccination. (pmc.ncbi.nlm.nih.gov) The weak spot was in germinal centers, which are short-lived immune “training camps” inside lymph nodes and spleen where B cells refine antibodies and build memory. In the high-fat group, the researchers found impaired germinal-center B cells and T follicular helper cells, the partner cells that help B cells improve their aim. (pmc.ncbi.nlm.nih.gov) That matters for vaccines that depend on strong antibody production in blood. The paper says the defects also reached lung-resident memory B cells, suggesting the problem was not only short-term antibody output but also longer-lasting immune memory. (pmc.ncbi.nlm.nih.gov) The bacterium in this study is a common hospital pathogen that can cause pneumonia, bloodstream infections, urinary tract infections, and surgical-site infections. The Centers for Disease Control and Prevention says *Pseudomonas aeruginosa* infections often occur in healthcare settings and can be hard to treat because the germ can resist antibiotics. (cdc.gov) The obesity side of the story is not niche. The Centers for Disease Control and Prevention says 40.3% of United States adults ages 20 and older had obesity in August 2021 through August 2023. (cdc.gov) The paper did find one immune backup system. Vaccinated obese mice developed expanded lung tissue-resident memory T cells, which are immune cells that stay parked in lung tissue instead of circulating in blood, and those cells appeared to support early protection after infection challenge. (pmc.ncbi.nlm.nih.gov) Lead author Wendy L. Picking of the University of Missouri said the results point toward vaccines designed to build protection directly in tissues, not only higher antibody counts in blood. The researchers said their next step is to identify the molecular signals that let those lung-resident T cells activate despite chronic inflammation linked to obesity. (news-medical.net)