Intranasal trivalent candidate vaccine elicits broad humoral and cellular immunity against pneumococcal pneumonia

Fangyu Ren^1,2Luyun Huang^1,3Shilu Luo^2,3Changjin Liu^2,3Xianlian Chen^2,3Xin Yao^2,3Qiqi Linghu^2,3Huaqin Hu^2,3Xiaoyu Huang^2,3Yuanqin Hu^2,3Jian Huang^2,3*Xun Min^2,3*

• ¹Department of Laboratory Medicine, First Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou Province, China
• ²Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China
• ³School of Laboratory Medicine, Zunyi Medical University, Zunyi, Guizhou Province, China

Streptococcus pneumoniae is an important pathogen causing public health problems worldwide.Existing pneumococcal vaccines provide protection against only a few of the more than 100 pneumococcal serotypes, highlighting the urgent need for new preventive strategies. Pneumococcal protein vaccines have attracted considerable attention owing to their favorable immunogenicity and antigen conservation, and have demonstrated protective potential against non-serotype-dependent infections. Mice immunized with a trivalent vaccine targeting protein PepN, PepO, and SPD_1609 elicited a robust humoral immune response, as well as Th1, Th2, and Th17 cellular immune responses. The antiserum derived from the trivalent vaccine significantly inhibited Streptococcus pneumoniae adhesion to A549 cells, reduced pneumococcal colonization in the nasopharynx, and improved lung tissue damage and inflammatory responses compared to the monovalent or bivalent vaccine group. In terms of in vivo protection, the trivalent vaccine significantly increased the survival rate of infected mice. The findings suggest that the trivalent vaccine targeting PepN, PepO, and SPD_1609 is a promising multivalent vaccine candidate against Streptococcus pneumoniae.