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 byPCRinOctober 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 (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.
Bibliographical noteFunding Information:
We thank the study participants and the field assistants at Kipsamoite and Kapsisiywa villages in Nandi County. We are also indebted to Jackson Abuya, David Koech, the late Livingstone Wanyama, Bartholomew Ondigo, Kelvin Onoka, Jackline Omundi, Lilian Kisia and Jonathan Bett for technical assistance in field collections and with the assays. 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.
© 2017 Ayieko et al.
- Highland Kenya
- Interferon gamma
- Plasmodium falciparum