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. 2022 Jan 25;90(1):e00377-21. doi: 10.1128/IAI.00377-21

FIG 2.

FIG 2

Detection of naturally acquired antibody response against CyRPA. (A) Antibody response against CyRPA and other key merozoite antigens, namely RH5, MSP-Fu, and EBA-175, were analyzed in plasma from 54 malaria-infected individuals obtained from a region in central India where malaria is endemic, Balaghat (Madhya Pradesh), by enzyme-linked immunosorbent assay (ELISA). CyRPA exhibited detectable levels of antibodies, with absolute ELISA values ranging from ∼0.1 to 0.48 optical density (OD) units. However, MSP-Fu and EBA-175 exhibited high immunogenicity, with values ranging from 0.29 to 3.8 and 0.17 to 3.9 ELISA OD units, respectively. Similarly, RH5 had higher ELISA OD unit values (0.5 to 3.0) than CyRPA. Note that the recombinantly produced F2 domain region of EBA-175 was used in ELISA to analyze the immunogenicity against EBA-175. (B) Among 54 plasma samples, only ∼28% showed a positive response against CyRPA. Similarly, RH5 was positively detected in only ∼30% samples. On the other hand, EBA-175 and MSP-Fu showed high seropositivity, with ∼94% and ∼87% samples, respectively, exhibiting a positive response. (C) The immunogenicity of individual components of MSP-Fu, MSP-119, and MSP-311 was also analyzed in the malaria-infected plasma samples. MSP-311 exhibited a high antibody response, with ELISA OD values ranging from 0.4 to 3.8 units. MSP-119 antibody response was low compared to that of MSP-311 antibody, ranging between 0.01 and 0.9 ELISA OD units. (D) Percent seropositivity of MSP-119 and MSP-311 shows that around 43% of individuals were positive for MSP-119-specific antibodies, while ∼88% of plasma samples exhibited a positive response for MSP-311. The mean OD of control malaria-naive samples, 5, plus 3× the standard deviation was taken as a cutoff and was used to calculate the percentages of positive and negative responders. An ELISA OD value above the cutoff was described as a positive response, and a value below the cutoff was considered a negative response. (A and C) Graph showing median values and ranges; a horizontal dashed line indicates the cutoff.