Streptococcus pneumoniae is a leading infectious pathogen, causing pneumonia, bacteremia, meningitis, acute
otitis media, and nearly one million deaths worldwide each year. S. pneumoniae can be carried in the
nasopharynx asymptomatically, which contributes to pathogen spread, as pneumococcal carriage often
precedes active infection. Infections occur with increased frequency in high-risk populations, such as individuals
with diabetes, asthma, chronic obstructive pulmonary disease, cardiovascular disease, and HIV. Several
vaccines are currently in use to prevent pneumococcal infection; however, several factors warrant further
research, including limited serotype coverage of current vaccines, limited vaccine efficacy against some vaccine-
included serotypes, increased incidence of colonization and infection with non-vaccine serotypes, and
widespread drug and multidrug antibiotic resistance among non-vaccine serotypes. This R01 proposal will
address these limitations by defining the structural determinants mediating the serotype breadth and
protective efficacy of broadly-reactive human mAbs that prevent and treat pneumococcal infection. The
scientific premise of this proposal is that mAbs to conserved pneumococcal antigens that are broadly reactive
could serve as priority or adjunctive therapies for pneumococcal disease management. This proposal will focus
on mAbs to pneumococcal antigens that are highly conserved and are targets of B cells during pneumococcal
colonization and infection. Our work will advance the field by generating new therapeutic options for the
prevention and treatment of pneumococcal infection for diverse serotypes, including encapsulated and
nonencapsulated serotypes, and by identifying protective epitopes on pneumococcal surface proteins. Our
innovative hypothesis is that human mAbs targeting conserved pneumococcal surface proteins will exhibit
substantial serotype breadth, can treat pneumococcal infection, and that mAb protective efficacy and serotype
breadth is correlated to epitope specificity. Our data will provide new findings for the pneumococcal protein
vaccine field. In Aim 1, the serotype breadth and protective efficacy of human mAbs targeting conserved protein
antigens will be determined in models of both primary and secondary (following influenza virus infection)
pneumococcal infection. In Aim 2, we will define the epitopes mediating the protective efficacy of the human
mAbs using X-ray crystallography and cryo-EM, which will be critical to the field by informing the development
of protein-based pneumococcal vaccines, as we have shown in our preliminary data that the epitope on
pneumococcal proteins impacts mAb breadth and protective efficacy. In Aim 3, we will conduct in depth in vitro
and in vivo mechanistic studies to assess mAb functions, including opsonophagocytic and agglutination activity,
and inhibition of bacterial growth, adhesion, invasion, and biofilm formation. We will also assess the specific
immunological pathways important for mAb-mediated bacterial clearance. Overall, our work is both practically
and conceptually innovative, and will challenge current treatment paradigms for pneumococcal infection.