Summary auto-generated
Researchers successfully synthesized immunogenic, non-infectious poliovirus empty capsids in baker's yeast (Saccharomyces cerevisiae) by expressing polioviral genes encoding structural proteins and viral protease. Initially, assembled capsids were unstable and denatured (H-antigen form), lacking neutralizing epitopes. However, adding pirodavir—a capsid-binding compound that mimics natural stabilizers found in infected cells—preserved the native capsid conformation (N-antigen form) during assembly and purification. Using immunoaffinity chromatography with monoclonal antibodies, researchers purified the N-antigenic empty capsids to homogeneity from yeast extracts. Immunogenicity testing in mice demonstrated that these yeast-derived empty capsids induced antibody responses comparable to native poliovirus virions, including neutralizing antibodies that could inhibit viral infection. The approach produced approximately 100 micrograms of purified N-antigenic particles per liter of yeast culture. These results demonstrate that yeast can serve as an alternative production system for non-infectious poliovirus vaccine candidates and potentially for other picornavirus vaccines.
Key findings
- Poliovirus empty capsids synthesized in yeast were initially denatured (H-antigen); adding pirodavir during induction and purification stabilized them to the native N-antigenic form with intact neutralizing epitopes.
- N-antigenic empty capsids were successfully purified from yeast extracts using immunoaffinity chromatography with site-specific monoclonal antibodies, achieving high purity with minimal contamination.
- Yeast-derived N-antigenic empty capsids induced neutralizing antibody responses in mice equivalent to those elicited by authentic poliovirus virions.
- The yeast expression system produced approximately 100 micrograms of purified N-antigenic empty capsids per liter of culture.
- This work demonstrates feasibility of using yeast as a scalable production platform for non-infectious poliovirus vaccine candidates.
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Abstract
Polioviral genes coding for P1, the precursor for the structural proteins, and 3CD, the viral protease, were cloned in a Saccharomyces cerevisiae inducible expression system. N-antigenic empty capsids could be isolated from the yeast cell extract provided that pirodavir, a capsid-binding compound and capsid stabilizer, was added during the induction period and during purification. Purification was by immunoaffinity chromatography. The purified empty capsids had the same immunogenicity as poliovirus virions. The techniques described might be useful for the production of new non-infectious vaccines.