A VAR2CSA:CSP conjugate capable of inducing dual specificity antibody responses

Matondo Sungwa1, Thrane Susan, Janitzek Christoph Mikkel, Kavishe Reginald Adolph, Mwakalinga Steven Boniface1, Theander Thor Grundtvig, Salanti Ali, Nielsen Morten Agertoug, Sander Adam Frederik
.
1. Kilimanjaro Christian Medical University-College, and Kilimanjaro Clinical Research Institute, Moshi, Tanzania.
2. Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical
Sciences, University of Copenhagen and at Department of Infectious Diseases, Copenhagen University Hospital
(Rigshospitalet), Denmark.

Abstract:
Background:Vaccine antigens targeting specific P. falciparumparasite stages are under pre-clinical and clinical development. It seems plausible that vaccine with multiple specificities will offer higher protection. With this hypothesis, we exploited the SpyTag/SpyCatcher conjugation system to make a, post expression, dual antigen conjugate vaccine, comprising two clinically tested antigen candidates (CSP and VAR2CSA).

Methods:The DBL1x-DBL2x-ID2a region of VAR2CSA was genetically fused with SpyTag at N-terminus. The full-length CSP antigen was genetically fused to C-terminal SpyCatcher peptide. The covalent interaction between SpyTag/SpyCatcher enables the formation of DBL1x-DBL2x-ID2a:CSP conjugate vaccine. Immunogenicity and quality of antibody responses induced by the conjugate vaccine, as well as a control CSP-SpyCatcher vaccine, was tested in BALB/c mice.

Results: Serum samples obtained from mice immunized with the conjugate vaccine were able to recognize both untagged DBL1x-DBL2x-ID2a as well as CSP antigen. Moreover, the geometric mean anti-CSP antibody titer was 1.9-fold higher in serum (at day 35 and 55 post-first immunization) from mice immunized with the conjugate vaccine, as compared to mice receiving the control vaccine.

Conclusion: The data obtained in this study serves as proof-of-concept for the simultaneous induction of antibodies directed against individual antigen components in a dual stage anti-malaria vaccine.

Keywords:Malaria vaccine, Circumsporozoite protein, VAR2CSA, CSP-SpyCatcher, SpyTag-DBL1x-DBL2x-ID2a,
bacterial superglue, DBL1x-DBL2x-ID2a:CSP conjugate.