Multi-epitope chimeric antigen used as a serological marker to estimate Plasmodium falciparum transmission intensity in the border area of China-Myanmar

Background:Following the decline of malaria transmission in many countries and regions,serological parameters have become particularly useful for estimating malaria transmission in low-intensity areas.This study evaluated a novel serological marker,Malaria Random Constructed Antigen-1(M.RCAg-1),which contains 11 epitopes from eight Plasmodium falciparum antigens,as a tool for assessing malaria transmission intensity along the border area of China-Myanmar.Method:Serum from Plasmodium falciparum and P.vivax patients was used to detect the properties of M.RCAg-1 and antibody responses.Cross-sectional surveys were conducted at the China-Myanmar border and in Hainan province in 2012 and 2013 using cluster sampling.Filter blood spot papers were collected from all participants.Antibodies against M.RCAg-1 were detected using indirect ELISA.The Mann–Whitney test and Spearman’s rank correlation test were performed to analyze antibody data.P.falciparum malaria transmission intensity was estimated using a catalytic conversion model based on the maximum likelihood of generating a community seroconversion rate(SCR).Results:M.RCAg-1 was well-recognized by the naturally acquired anti-malaria antibodies in P.falciparum patients and had very limited cross-reactivity with P.vivax infection.The total amount of IgG antibodies was decreased with the decrease in parasitemia after taking medication and lasted several weeks.In a population survey,the antibody levels were higher in residents living close to the China-Myanmar border than those living in non-epidemic areas(P<0.0001),but no significant difference was observed between residents from Hainan and non-epidemic areas.The calculated SCR was 0.0128 for Jieyangka,0.004 for Susuzhai,0.0047 for Qiushan,and 0.043 for Kayahe.The estimated exposure rate obtained from the anti-M.RCAg-1 antibody level correlated with traditional measures of transmission intensity derived from altitude.Conclusion:Our study demonstrates that M.RCAg-1 is potentially useful as a serological indicator of exposure to P.falciparum malaria,especially for malaria surveillance in low transmission areas.