Kaushal Deep C, Kaushal Nuzhat A, Narula Atul, Kumar Niraj, Puri S K, Dutta Shitij, Lanar David E
Divisions of Microbiology, Central Drug Research Institute, Post Box 173, Lucknow 226001, India.
Indian J Biochem Biophys. 2007 Dec;44(6):429-36.
Plasmodium vivax is one of the most widely distributed human malaria parasites and due to drug-resistant strains, its incidence and prevalence has increased, thus an effective vaccine against the parasites is urgently needed. One of the major constraints in developing P. vivax vaccine is the lack of suitable in vivo models for testing the protective efficacy of the vaccine. P. vivax and P. cynomolgi bastianelli are the two closely related malaria parasites and share a similar clinical course of infection in their respective hosts. The merozoite surface protein-1 (MSP-1) of these parasites has found to be protective in a wide range of host-parasite systems. P. vivax MSP-1 is synthesized as 200 kDa polypeptide and processed just prior to merozoite release from the erythrocytes into smaller fragments. The C- terminal 42 kDa cleavage product of MSP-1 (MSP-1(42)) is present on the surface of merozoites and a major candidate for blood stage malaria vaccine. In the present study, we have biochemically and immunologically characterized the soluble and refolded 42 kDa fragment of MSP-1 of P. vivax (PvMSP-1(42)) and P. cynomolgi B (PcMSP-1(42)). SDS-PAGE analysis showed that both soluble and refolded E. coli expressed P. vivax and P. cynomolgi B MSP-1(42) proteins were homogenous in nature. The soluble and refolded MSP-1(42) antigens of both parasites showed high reactivity with protective monkey sera and conformation-specific monoclonal antibodies against P. cynomolgi B and P. vivax MSP-1(42) antigens. Immunization of BALB/c mice with these antigens resulted in the production of high titres of cross-reactive antibodies primarily against the conformational epitopes of MSP-1(42) protein. The immune sera from rhesus monkeys. immunized with soluble and refolded MSP-1(42) antigens of both parasites also showed high titered cross-reactive antibodies against MSP-1(42) conformational epitopes. These results suggested that the soluble and refolded forms of E. coli expressed P. vivax MSP-1(42) antigens were highly immunogenic and thus a viable candidate for vaccine studies.
间日疟原虫是分布最广泛的人类疟原虫之一，由于耐药菌株的出现，其发病率和流行率有所上升，因此迫切需要一种有效的抗该寄生虫疫苗。开发间日疟原虫疫苗的主要限制之一是缺乏合适的体内模型来测试疫苗的保护效力。间日疟原虫和食蟹猴疟原虫巴斯蒂安内利疟原虫是两种密切相关的疟原虫，在各自宿主中的感染临床过程相似。已发现这些寄生虫的裂殖子表面蛋白-1（MSP-1）在广泛的宿主-寄生虫系统中具有保护作用。间日疟原虫MSP-1最初作为200 kDa多肽合成，并在裂殖子从红细胞释放之前加工成较小的片段。MSP-1的C末端42 kDa裂解产物（MSP-1(42)）存在于裂殖子表面，是血期疟疾疫苗的主要候选物。在本研究中，我们对间日疟原虫（PvMSP-1(42)）和食蟹猴疟原虫B（PcMSP-1(42)）的MSP-1的42 kDa可溶性和复性片段进行了生化和免疫学表征。SDS-PAGE分析表明，大肠杆菌表达的间日疟原虫和食蟹猴疟原虫B的可溶性和复性MSP-1(42)蛋白在性质上是均一的。两种寄生虫的可溶性和复性MSP-1(42)抗原与保护性猴血清以及针对食蟹猴疟原虫B和间日疟原虫MSP-1(42)抗原的构象特异性单克隆抗体均表现出高反应性。用这些抗原免疫BALB/c小鼠导致产生高滴度的主要针对MSP-1(42)蛋白构象表位的交叉反应性抗体。用两种寄生虫的可溶性和复性MSP-1(42)抗原免疫的恒河猴的免疫血清也显示出针对MSP-1(42)构象表位的高滴度交叉反应性抗体。这些结果表明，大肠杆菌表达的间日疟原虫MSP-1(42)抗原的可溶性和复性形式具有高度免疫原性，因此是疫苗研究的可行候选物。
