T-cell and B-cell dynamics following prime-boost immunization with W135 meningococcal conjugate vaccine in mice.

Introduction: Glycoconjugate vaccines convert T-cell-independent polysaccharides into T-cell-dependent antigens, but the cellular dynamics of prime‑boost responses remain incompletely defined. Methods: Mice were immunized with the W135 meningococcal conjugate vaccine (PSW135‑TT), unconjugated PSW135, or TT alone in a two‑dose regimen given at a 2‑week interval. B‑cell and T‑cell responses were evaluated at multiple time points after each immunization. Results: PSW135‑TT accelerated PSW135‑specific IgG class switching and maintained higher IgM levels compared to PSW135 alone, with an IgG1‑dominant profile consistent with a Th2‑biased humoral response. The conjugate induced more sustained B‑cell activation across tissues and a splenic plasmablast/early plasma cell peak that coincided with antibody appearance. T‑cell analysis revealed repeated waves of early CD4⁺ T‑cell activation in blood and a triphasic late activation pattern in spleen after PSW135‑TT, suggesting prolonged activation; CD8⁺ T‑cell activation after booster was also observed. Nonspecific stimulation showed overall Th2 bias, whereas antigen‑specific restimulation induced a Th1‑dominant recall response; a late Th17 increase was observed only in the conjugate group. Conclusion: Thus, PSW135‑TT modulates B‑cell and T‑cell responses, supporting its potential as a vaccine candidate against W135 meningococcal disease.