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Design and Biological Assembly of Polyester Beads Displaying Pneumococcal Antigens as Particulate Vaccine
Majela González-Miró1,2, Anna-Maria Radecker2, Laura M Rodríguez-Noda1
1Finlay Vaccine Institute, 27th Avenue, No. 19805 between 198 and 202, La Lisa, Havana 11600, Cuba.
Insights
New polyester beads carrying pneumolysin or pneumococcal polysaccharide antigens significantly boost immune responses against Streptococcus pneumoniae infections in mice.
Area of Science:
- Vaccine development
- Immunology
- Biotechnology
Background:
- Streptococcus pneumoniae causes severe infections, particularly in vulnerable populations.
- Current conjugate vaccines offer serotype-specific protection but are ineffective against emerging serotypes.
- Pneumolysin (Ply) is a conserved, serotype-independent protein target for broader protection.
Purpose of the Study:
- To engineer polyhydroxybutyrate (PHB) polyester beads as carriers for pneumococcal antigens.
- To enhance the immunogenicity of pneumolysin (Ply) and capsular polysaccharide (CPS) 19F using PHB beads.
- To evaluate the immune responses induced by PHB bead-conjugated antigens compared to soluble forms.
Main Methods:
- Engineered recombinant Escherichia coli to produce Ply fused to polyhydroxybutyrate (PHB) synthase (PhaC) for surface display on PHB beads.
- Chemically conjugated capsular polysaccharide (CPS) 19F to isolated PHB beads.
- Immunized Balb/c mice with Ply-PhaC beads, 19F-PhaC beads, and their soluble counterparts, then assessed IgG levels, antibody recognition, splenocyte cytokine production, and opsonophagocytic activity.
Main Results:
- Mice immunized with Ply-PhaC and 19F-PhaC beads showed significantly higher specific IgG levels than those immunized with soluble antigens.
- Antibodies induced by Ply-PhaC beads recognized pneumolysin from multiple S. pneumoniae serotypes and promoted a balanced INF-γ/IL-17A cytokine profile.
- 19F-PhaC beads elicited high opsonophagocytic antibody titers against serotype 19F, while unconjugated CPS 19F showed no immune response.
Conclusions:
- PHB beads are effective carriers for enhancing the immunogenicity of both protein (Ply) and polysaccharide (CPS) antigens.
- This PHB bead-based platform shows promise for developing novel, broadly protective vaccines against Streptococcus pneumoniae.
- The study highlights the potential of self-assembled polyester beads for next-generation vaccine design.
Abstract:
Streptococcus pneumoniae can cause life-threatening infections mostly in infants, children, and elderly people. Capsular polysaccharide conjugate vaccines provide serotype-dependent protection against S. pneumoniae infections but fail to protect against new emerging serotypes. To overcome these limitations, pneumolysin (Ply), a serotype-independent and conserved protein was selected. As such subunit vaccines lack immunogenicity, we engineered Ply to be attached to self-assembled polyester beads in order to boost immunogenicity. To display Ply at the surface of these polyester beads, it was translationally fused to the N-terminus of the polyhydroxybutyrate (PHB) synthase (PhaC), which mediates PHB bead assembly inside recombinant Escherichia coli. We also chemically conjugated the capsular polysaccharide (CPS) 19F to isolated PHB beads to further assess their antigen carrier properties. CPS conjugated to soluble tetanus toxoid served as control. Balb/c mice immunized with Ply-PhaC beads and 19F-PhaC beads induced specific and higher IgG levels than the respective soluble counterparts. The induced IgG antibodies recognized Ply in whole cell lysates of six different serotypes of S. pneumoniae. Additionally, restimulated splenocytes from animals immunized with Ply-PhaC beads produced a balanced INF-γ/IL-17A profile unlike animals immunized with soluble Ply. The 19F-PhaC beads induced production of antibodies showing high opsonophagocytic titers against the homologous strain, serotype 19F, while CPS 19F only mixed with PhaC beads did not elicit any detectable immune response. This study provided insight into the design of PHB beads as a carrier of proteinaceous antigens and CPS in order to induce immune responses for the prevention of pneumococcal infections.
