Abstract
BackgroundMalaria 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.MethodsIFN- 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.ResultsWhile 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).DiscussionNaturally 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.
Highlights
More than 200 million people each year develop clinical malaria, mostly in sub-Saharan Africa (WHO, 2012)
None tested positive for P. falciparum infection by microscopy during the sample collections in April 2008, October 2008 or April 2009
The present study demonstrates that IFN-γ responses to several pre-erythrocytic and blood stage P. falciparum candidate vaccine antigens decrease in the absence of malaria transmission
Summary
More than 200 million people each year develop clinical malaria, mostly in sub-Saharan Africa (WHO, 2012). How to cite this article Ayieko et al (2017), Interferon-γ responses to Plasmodium falciparum vaccine candidate antigens decrease in the absence of malaria transmission. Even after life-long exposure to malaria, many people living in malaria endemic areas have asymptomatic Plasmodium infection and poor responses to common P. falciparum antigens (Egan et al, 1996; Owusu-Agyei et al, 2001). Evidence from mathematical model suggest that interventions that interrupt malaria infection may lead to loss of immunity (Ghani et al, 2009). These observations suggest inefficiencies in the process of maintaining protective immunity to malaria antigens. Even short periods of malaria interruption may significantly decrease IFN-γ responses to P. falciparum antigens
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