Interferon-γ responses to Plasmodium falciparum vaccine candidate antigens decrease in the absence of malaria transmission
Cyrus Ayieko, Bilha S Ogola, Lyticia Ochola, Gideon AM Ngwena, George Ayodo, James S Hodges, Gregory S Noland, Chandy C John
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Background. Malaria elimination campaigns are planned or active in many countries. The effects of malaria elimination on immune responses such as antigen-specific IFNγ 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. 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-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 shortlived in the absence of repeated P. falciparum infection. Even short periods of malaria interruption may significantly decrease IFN-γ responses to P. falciparum antigens.
- Department of Zoology