Department of Infectious Diseases, Tokai University School of Medicine, Isehara, Kanagawa, Japan.
Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Sci Rep. 2021 Feb 5;11(1):3201. doi: 10.1038/s41598-021-82928-4.
Merozoite surface protein 9 (MSP9) constitutes a ligand complex involved in erythrocyte invasion by malarial merozoites and is a promising vaccine target. Plasmodium vivax MSP9 (PvMSP9) is immunogenic upon natural malaria exposure. To address whether sequence diversity in PvMSP9 among field isolates could affect natural antibody responses, the recombinant proteins representing two variants each for the N- and the C-terminal domains of PvMSP-9 were used as antigens to assess antibody reactivity among 246 P. vivax-infected patients' sera from Tak and Ubon Ratchathani Provinces in Thailand. Results revealed that the seropositivity rates of IgG antibodies to the N-terminal antigens were higher than those to the C-terminal antigens (87.80% vs. 67.48%). Most seropositive sera were reactive to both variants, suggesting the presence of common epitopes. Variant-specific antibodies to the N- and the C-terminal antigens were detected in 15.85% and 16.70% of serum samples, respectively. These seropositivity rates were not significant difference between provinces. The seropositivity rates, levels and avidity of anti-PvMSP9 antibodies exhibited positive trends towards increasing malaria episodes. The IgG isotype responses to the N- and the C-terminal antigens were mainly IgG1 and IgG3. The profile of IgG responses may have implications for development of PvMSP9-based vaccine.
裂殖子表面蛋白 9（MSP9）构成了参与疟原虫裂殖子入侵红细胞的配体复合物，是一种很有前途的疫苗靶点。在自然疟疾感染时，间日疟原虫 MSP9（PvMSP9）具有免疫原性。为了研究 PvMSP9 在现场分离株中的序列多样性是否会影响自然抗体反应，使用代表 PvMSP-9 的 N-和 C-末端结构域的两种变体的重组蛋白作为抗原，来评估来自泰国塔科和乌汶叻差他尼省的 246 例间日疟原虫感染患者血清中的抗体反应性。结果表明，针对 N-末端抗原的 IgG 抗体的血清阳性率高于针对 C-末端抗原的血清阳性率（87.80% vs. 67.48%）。大多数血清阳性的血清对两种变体都有反应，表明存在共同的表位。针对 N-和 C-末端抗原的变体特异性抗体分别在 15.85%和 16.70%的血清样本中被检测到。这些血清阳性率在两个省份之间没有显著差异。抗 PvMSP9 抗体的血清阳性率、水平和亲和力与疟疾发作次数呈正相关。针对 N-和 C-末端抗原的 IgG 亚型反应主要是 IgG1 和 IgG3。IgG 反应谱可能对 PvMSP9 为基础的疫苗的开发具有重要意义。
