Evaluating the storage stability of a Plasmodium vivax circumsporozoite protein vaccine candidate

Abstract

Malaria is a serious public health problem, with approximately 263 million cases recorded worldwide in 2023. The prevention of this disease and the development of vaccines against it remain critical issues to resolve. However, the ability of newly developed formulations to remain stable and biologically active under storage is a challenge to overcome but highly relevant, considering the places where such vaccines are needed. In this study, we evaluated the six-month storage stability of yPvCSP-All epitopes, a Plasmodium vivax malaria vaccine candidate, comprising a recombinant protein expressed in the yeast Pichia pastoris. The stability of the liquid and lyophilized formulations after storage at three different temperatures was determined using SDS-PAGE, immunoblotting, circular dichroism, SEC, RP-HPLC, and immunization assays. In liquid formulation, only the recombinant protein stored at –20°C remained stable for 180 days. By contrast, the lyophilized formulations showed no signs of degradation for six months when stored at –20°C and 5°C, and they all induced high antibody titers. These results demonstrate that the vaccine formulations can remain stable under some of the tested conditions, which is promising considering the difficulty of maintaining the cold chain in regions where malaria is endemic.