Comparison of Immunogenicity and Protection of Two Pneumococcal Protein Vaccines Based on PsaA and PspA

Area of Science:

• Immunology
• Vaccinology
• Microbiology

Background:

• Streptococcus pneumoniae causes significant invasive pneumococcal disease, particularly in young children.
• Current polysaccharide vaccines offer type-specific immunity, but broader coverage is needed.
• Protein-based vaccines are essential for extending protection to more pneumococcal serotypes.

Purpose of the Study:

• To evaluate the efficacy of a novel systemic protein-based vaccine against Streptococcus pneumoniae.
• To compare the systemic vaccine with an intranasal mucosal vaccine.
• To assess antibody responses, bacterial load, and survival rates post-challenge.

Main Methods:

• Mice were immunized subcutaneously with a systemic vaccine (PsaA-PspA23, PspA4, aluminum hydroxide).
• Mice were immunized intranasally with a mucosal vaccine (PspA2-PA-BLP, PspA4-PA-BLP).
• Immunized mice were challenged with Streptococcus pneumoniae, and immune responses, bacterial loads, and survival were analyzed.

Main Results:

• Both systemic and mucosal vaccines significantly increased serum IgG antibodies against PspAs.
• The mucosal vaccine uniquely induced specific IgA in mucosal tissues.
• Both vaccines provided protection, with the systemic vaccine yielding higher serum IgG and the mucosal vaccine reducing bacterial load in lungs and blood.

Conclusions:

• Both systemic and mucosal protein-based vaccines are effective against Streptococcus pneumoniae challenge.
• Systemic vaccination elicits stronger systemic antibody responses, while mucosal vaccination enhances mucosal immunity and reduces bacterial dissemination.
• Combined systemic and mucosal immunization strategies may offer a promising approach for broader pneumococcal protection.