Cellular immunity to Streptococcus pneumoniae: implications for vaccine-mediated prevention

Area of Science:

• Immunology
• Vaccinology
• Microbiology

Background:

• Streptococcus pneumoniae causes mucosal and invasive diseases.
• Current vaccines induce serotype-dependent humoral immunity, but over 100 serotypes limit effectiveness.
• The role of cellular immunity in protection against S. pneumoniae is not fully understood in humans.

Purpose of the Study:

• To summarize evidence on cellular immune responses to S. pneumoniae exposure.
• To review cellular immune responses induced by candidate pneumococcal vaccines.
• To highlight the need for broader immunological strategies beyond antibodies.

Main Methods:

• Review of existing literature on cellular immunity against S. pneumoniae.
• Analysis of data from animal models and human challenge studies.
• Overview of immune responses elicited by various vaccine platforms (whole-cell, protein-based, MAPS).

Main Results:

• Animal models suggest CD4+ (Th1, Th17) and CD8+ T cells contribute to protection.
• Human studies indicate potential roles for CD8+ T cells, CD4+ Th17 cells, and tissue-resident memory T cells.
• Candidate vaccines aim to elicit diverse cellular immune responses.

Conclusions:

• Improving pneumococcal vaccines requires multipronged immune responses.
• New immunological benchmarks beyond capsular antibodies are needed.
• Defining protective cellular responses is a critical research priority.