Liposomal encapsulation of polysaccharides (LEPS) confers higher protection to the host against invasive serotype 3 S. pneumoniae infection

Authors: Miles Stefko, Manmeet Bhalla

SUNY Campus: SUNY Buffalo

Presentation Type: Poster

Location: Old Union Hall

Presentation #: 47

Timeslot: Session B 10:15-11:15 AM

Abstract: Streptococcus pneumoniae (pneumococcus) serotype 3 remains a serious global health threat, causing pneumonia, bacteremia, meningitis, and cardiac toxicity, particularly in individuals over 65 and those with comorbidities. Despite its inclusion in pneumococcal conjugate vaccines, serotype 3 strains continue to escape vaccine coverage due to capsular properties, allowing immune evasion and invasive breakthrough infections. This study tested a modified Liposomal Encapsulation of Polysaccharides (LEPS) vaccine platform against serotype 3 S. pneumoniae infection. LEPS enables non-covalent coupling of pneumococcal polysaccharide (PPS) and protein antigens. We designed a vaccine that included the following antigens: PPS3, the intramembrane metalloprotease PncO and the cell-wall-associated PspA. Immunogenicity and protective efficacy were measured in young (2-3 months) and aged (18-22 months) C57BL/6J mice, comparing LEPS to the clinically available vaccine Prevnar. LEPS immunization induced antibody production against both serotype 3 polysaccharide and protein components. In a pulmonary challenge model, it significantly reduced bacterial burden in young mice lungs compared to PCV13 and prevented bacterial spread to the heart, spleen, and meninges in both age groups. LEPS also increased neutrophil and dendritic cell recruitment at the injection site compared to Prevnar. Overall, LEPS effectively protected young and aged mice against S. pneumoniae serotype 3 infections. Future research will explore immune responses in secondary lymphoid organs that mediate this protection.