Although hemolytic lipids have been discovered from many human pathogens including Group B Streptococcus (GBS), strategies that neutralize their function are lacking. GBS is a leading cause of pregnancy-associated neonatal infections, and adult GBS infections are on the rise. The GBS hemolytic lipid toxin or granadaene, is cytotoxic to many immune cells including T and B cells. Researchers previously showed that mice immunized with a synthetic nontoxic analog of granadaene known as R-P4 had reduced bacterial dissemination during systemic infection. However, mechanisms important for R-P4 mediated immune protection was not understood. Here, they show that immune serum from R-P4-immunized mice facilitate GBS opsonophagocytic killing and protect naïve mice from GBS infection.