A bivalent vaccine to protect against Streptococcus pneumoniae and Salmonella typhi

Area of Science:

• Vaccinology
• Immunology
• Pediatric Infectious Diseases

Background:

• Pneumococcal and Salmonella typhi infections are significant childhood diseases in developing nations.
• Current vaccines for young children (<2 years) against typhoid fever are ineffective, and pneumococcal vaccines have limitations like cost and serotype coverage.
• Previous research demonstrated a fusion conjugate vaccine's efficacy against pneumococcal disease in mice.

Purpose of the Study:

• To develop a bivalent conjugate vaccine targeting both Streptococcus pneumoniae (pneumococcus) and Salmonella typhi (typhoid fever).
• To evaluate the immunogenicity and protective efficacy of this novel bivalent vaccine in a mouse model.

Main Methods:

• Two conserved pneumococcal antigens (SP1572, SP2070) were fused to a pneumolysoid (PdT).
• SP1572-PdT was conjugated to Vi polysaccharide, and SP2070-PdT to pneumococcal cell wall polysaccharide (CWPS).
• Mice were immunized with the bivalent conjugate and challenged with pneumococcus and S. typhi to assess protection and antibody responses.

Main Results:

• The bivalent conjugate vaccine protected mice against pneumococcal colonization and sepsis.
• Mice immunized with the bivalent conjugate produced 40-fold higher anti-Vi antibody concentrations compared to those receiving antigen mixtures.
• Plasma from immunized mice demonstrated enhanced in vitro killing of Vi-bearing Salmonellae.

Conclusions:

• The developed bivalent fusion conjugate vaccine is immunogenic and protective against pneumococcal and S. typhi challenges in mice.
• This approach offers a potential strategy for a combined vaccine to prevent pneumococcal disease and typhoid fever in young children.
• Further evaluation of this bivalent immunogen is warranted for clinical development.