Interferon- γ Responses to Plasmodium falciparum Vaccine Candidate Antigens Decrease in the Absence of Malaria Transmission

PeerJ. 2017 Jan 10;5:e2855. doi: 10.7717/peerj.2855. eCollection 2017.

Abstract

Background: Malaria elimination campaigns are planned or active in many countries. The effects of malaria elimination on immune responses such as antigen-specific IFN- γ responses are not well characterized.

Methods: IFN- γ responses to the P. falciparum antigens circumsporozoite protein, liver stage antigen-1, thrombospondin-related adhesive protein, apical membrane antigen-1, MB2, and merozoite surface protein-1 were tested by ELISA in 243 individuals in highland Kenya in April 2008, October 2008, and April 2009, after a one-year period of interrupted malaria transmission from April 2007 to March 2008.

Results: While one individual (0.4%) tested positive for P. falciparum by PCR inOctober 2008 and another two (0.9%) tested positive in April 2009, no clinical malaria cases were detected during weekly visits. Levels of IFN-γ to all antigens decreased significantly from April 2008 to April 2009 (all P < 0.001).

Discussion: Naturally acquired IFN- γ responses to P. falciparum antigensare short-lived in the absence of repeated P. falciparum infection. Even short periods of malaria interruption may significantly decrease IFN-γ responses to P. falciparum antigens.

Keywords: Highland Kenya; Interferon gamma; Malaria; Plasmodium falciparum.

Grant support

This work was supported by grants from the National Institute of Allergy and Infectious Diseases (Grant 5U01 A1056270 to CCJ) and the Fogarty International Center (Grant D43 TW008085 to CCJ). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.