Effective Functional Immunogenicity of a DNA Vaccine Combination Delivered via In Vivo Electroporation Targeting Malaria Infection and Transmission

Yi Cao, Department of Global Health, Milken Institute School of Public Health, George Washington University, Washington, DC 20052, USA.
Clifford T. Hayashi, Department of Global Health, Milken Institute School of Public Health, George Washington University, Washington, DC 20052, USA.
Fidel Zavala, Department of Molecular Microbiology & Immunology, Johns Hopkins Malaria Research Institute, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA.
Abhai K. Tripathi, Department of Molecular Microbiology & Immunology, Johns Hopkins Malaria Research Institute, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA.
Hayk Simonyan, Department of Pharmacology and Physiology, School of Medicine and Health Sciences, George Washington University, Washington, DC 20052, USA.
Colin N. Young, Department of Pharmacology and Physiology, School of Medicine and Health Sciences, George Washington University, Washington, DC 20052, USA.
Leor C. Clark, Department of Global Health, Milken Institute School of Public Health, George Washington University, Washington, DC 20052, USA.
Yukari Usuda, Department of Global Health, Milken Institute School of Public Health, George Washington University, Washington, DC 20052, USA.
Jacob M. Van Parys, Department of Global Health, Milken Institute School of Public Health, George Washington University, Washington, DC 20052, USA.
Nirbhay Kumar, Department of Global Health, Milken Institute School of Public Health, George Washington University, Washington, DC 20052, USA.

Document Type

Journal Article

Publication Date

7-16-2022

Journal

Vaccines

Volume

10

Issue

7

DOI

10.3390/vaccines10071134

Keywords

Plasmodium falciparum; combined DNA vaccine; pre-erythrocytic vaccine; transmission blocking vaccine

Abstract

 circumsporozoite protein (PfCSP) and Pfs25 are leading candidates for the development of pre-erythrocytic and transmission-blocking vaccines (TBV), respectively. Although considerable progress has been made in developing PfCSP- and Pfs25-based vaccines, neither have elicited complete protection or transmission blocking in clinical trials. The combination of antigens targeting various life stages is an alternative strategy to develop a more efficacious malaria vaccine. In this study, female and male mice were immunized with DNA plasmids encoding PfCSP and Pfs25, administered alone or in combination via intramuscular in vivo electroporation (EP). Antigen-specific antibodies were analyzed for antibody titers, avidity and isotype by ELISA. Immune protection against sporozoite challenge, using transgenic expressing PfCSP and a GFP-luciferase fusion protein (PbPfCSP-GFP/Luc), was assessed by in vivo bioluminescence imaging and blood-stage parasite growth. Transmission reducing activity (TRA) was evaluated in standard membrane feeding assays (SMFA). High levels of PfCSP- and Pfs25-specific antibodies were induced in mice immunized with either DNA vaccine alone or in combination. No difference in antibody titer and avidity was observed for both PfCSP and Pfs25 between the single DNA and combined DNA immunization groups. When challenged by PbPfCSP-GFP/Luc sporozoites, mice immunized with PfCSP alone or combined with Pfs25 revealed significantly reduced liver-stage parasite loads as compared to mice immunized with Pfs25, used as a control. Furthermore, parasite liver loads were negatively correlated with PfCSP-specific antibody levels. When evaluating TRA, we found that immunization with Pfs25 alone or in combination with PfCSP elicited comparable significant transmission reduction. Our studies reveal that the combination of PfCSP and Pfs25 DNAs into a vaccine delivered by in vivo EP in mice does not compromise immunogenicity, infection protection and transmission reduction when compared to each DNA vaccine individually, and provide support for further evaluation of this DNA combination vaccine approach in larger animals and clinical trials.

Department

Global Health

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