Interferon-γresponses toPlasmodium falciparumvaccine candidate antigens decrease in the absence of malaria transmission

Abstract

BackgroundMalaria elimination campaigns are planned or active in many countries. The effects of malaria elimination on immune responses such as antigen-specific IFN-γresponses are not well characterized.MethodsIFN-γresponses to theP. falciparumantigens 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.ResultsWhile one individual (0.4%) tested positive forP. falciparumby 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-γto all antigens decreased significantly from April 2008 to April 2009 (allP< 0.001).DiscussionNaturally acquired IFN-γresponses toP. falciparumantigensare short-lived in the absence of repeatedP. falciparuminfection. Even short periods of malaria interruption may significantly decrease IFN-γresponses toP. falciparumantigens.