Omosun Y O, Anumudu C I, Adoro S, Odaibo A B, Sodeinde O, Holder A A, Nwagwu M, Nwuba R I
Department of Zoology, University of Ibadan, Ibadan, Nigeria.
Acta Trop. 2005 Sep;95(3):233-47. doi: 10.1016/j.actatropica.2005.06.019.
Malaria remains a major parasitic disease in Africa, with 300-500 million new infections each year. There is therefore an urgent need for the development of new effective measures, including vaccines. Plasmodium falciparum merozoite surface protein-1(19) (MSP-1(19)) is a prime candidate for a blood-stage malaria vaccine. Blood samples were collected from children aged 10 days to 15 years in the months of January-March (N = 351) and October-November (N = 369) corresponding to the dry and rainy seasons, respectively. P. falciparum infection was determined by microscopy and enzyme linked immunosorbent assay (ELISA) was used to determine the total IgG and IgG subclasses. There was a significant increase in the mean anti-MSP-1(19) antibody titre in the dry season (p < 0.05), compared to the rainy season. A significantly positive correlation between the anti-MSP-1(19) antibody titre and parasite density (p < 0.01, r = 0.138) was observed. In the rainy season, unlike in the dry season, P. falciparum positive children had higher anti-MSP-1(19) antibody titres than P. falciparum negative children and this difference was significant (p < 0.05). When all individuals were grouped together, the anti-MSP-1(19) antibody titre increased with age in both seasons (r = 0.186 and 0.002), this increase was more apparent in the dry season. However, when the study population was divided into P. falciparum positive and negative groups, it was observed that in the rainy season, there was a negative correlation between anti-MSP-1(19) titre and age in P. falciparum positive individuals, while those who were P. falciparum negative had a positive correlation between anti-MSP-1(19) titre and age. Analysis of anti-MSP-1(19) IgG subclass showed that IgG1 and IgG3 mean titres were highest in both the dry and rainy seasons with an increase in the mean antibody titres for IgG1, IgG2 and IgG3 in the rainy season. In the dry season there was a positive correlation between IgG1, IgG2, and IgG3 titres with age, while IgG4 was negative, whereas in the rainy season there was a positive correlation between IgG2 and IgG4 (non-cytophilic antibodies) with age and a negative correlation for IgG1 and IgG3 (cytophilic antibodies) with age. Seasonal differences in the level of MSP-1(19) IgG subclass titres were observed for P. falciparum negative and positive individuals. Only samples, which were positive for IgG2 and IgG4, showed positive correlation between parasitemia and total IgG. The incidence of P. falciparum infection, which increases during the rainy season, might be an important determinant of anti-MSP-1(19) antibody levels in children living in Igbo-Ora and the results point to the fact that non-cytophilic antibodies to MSP-1(19) in children might be associated with an increase in total IgG and parasitemia.
疟疾仍是非洲的一种主要寄生虫病，每年有3亿至5亿新感染病例。因此，迫切需要开发新的有效措施，包括疫苗。恶性疟原虫裂殖子表面蛋白-1（19）（MSP-1（19））是血源性疟疾疫苗的主要候选对象。分别在1月至3月（N = 351）和10月至11月（N = 369）对应旱季和雨季期间，收集了10天至15岁儿童的血样。通过显微镜检查确定恶性疟原虫感染情况，并使用酶联免疫吸附测定（ELISA）来测定总IgG和IgG亚类。与雨季相比，旱季抗MSP-1（19）抗体平均滴度显著升高（p < 0.05）。观察到抗MSP-1（19）抗体滴度与寄生虫密度之间存在显著正相关（p < 0.01，r = 0.138）。在雨季，与旱季不同，恶性疟原虫阳性儿童的抗MSP-1（19）抗体滴度高于恶性疟原虫阴性儿童，且这种差异具有显著性（p < 0.05）。当将所有个体归为一组时，两个季节中抗MSP-1（19）抗体滴度均随年龄增加（r = 0.186和0.002），这种增加在旱季更为明显。然而，当将研究人群分为恶性疟原虫阳性和阴性组时，观察到在雨季，恶性疟原虫阳性个体中抗MSP-1（19）滴度与年龄呈负相关，而恶性疟原虫阴性个体中抗MSP-1（19）滴度与年龄呈正相关。抗MSP-1（19）IgG亚类分析表明，旱季和雨季中IgG1和IgG3平均滴度最高，雨季中IgG1、IgG2和IgG3的平均抗体滴度有所增加。在旱季，IgG1、IgG2和IgG3滴度与年龄呈正相关，而IgG4呈负相关，而在雨季，IgG2和IgG4（非嗜细胞性抗体）与年龄呈正相关，IgG1和IgG3（嗜细胞性抗体）与年龄呈负相关。观察到恶性疟原虫阴性和阳性个体的MSP-1（19）IgG亚类滴度水平存在季节性差异。仅IgG2和IgG4呈阳性的样本显示寄生虫血症与总IgG之间存在正相关。雨季期间增加的恶性疟原虫感染发生率可能是伊博奥拉地区儿童抗MSP-1（19）抗体水平的一个重要决定因素，结果表明儿童中针对MSP-1（19）的非嗜细胞性抗体可能与总IgG和寄生虫血症的增加有关。
