Chatterjee S, Wery M, Sharma P, Chauhan V S
Prince Leopold Institute of Tropical Medicine, Antwerp, Belgium.
Infect Immun. 1995 Nov;63(11):4375-81. doi: 10.1128/iai.63.11.4375-4381.1995.
Minutes after injection into the circulation, malaria sporozoites enter hepatocytes. The speed and specificity of the invasion process suggest that it is receptor mediated. The region II sequence of Plasmodium falciparum circumsporozoite (CS) protein includes a nonapeptide (WSPCSVTCG) which is highly conserved in all of the CS proteins sequenced to data, including the one from Plasmodium berghei. We have found that two peptides based on the P. falciparum region II sequence, P18 (EWSPCSVTCGNGIQVRIK) and P32 (IEQYLKKIKNS ISTEWSPCSVTCGNGIQVRIK), significantly inhibited P. berghei sporozoite invasion into Hep-G2 cells in vitro. This inhibition was enhanced if either peptide was preincubated with Hep-G2 cells prior to sporozoite invasion. We confirm that region II is a sporozoite ligand for the hepatocyte receptor; moreover, despite the few differences between P. falciparum and P. berghei region II sequences around the nonapeptide sequence (66% homology), the functional characteristics of the motif sequences are not affected. Since the conserved motifs represent a crucial sequence involved in Plasmodium sporozoite invasion of hepatocytes, antibodies to region II should inhibit sporozite invasion into hepatocytes. Indeed, we found that polyclonal antibodies generated to the P. falciparum-based peptide P32 inhibited P. berghei sporozoite invasion of Hep-G2 cells. Furthermore, inbred mice (C57BL/6) immunized with P32 were protected against a lethal challenge of P. berghei sporozoites. Our results suggest that the conserved region II of the CS protein contains crucial B- and T-cell epitopes, that such peptide sequences from the human malaria parasite P. falciparum can be screened in the P. berghei rodent model, and, finally, that region II can be considered useful as one of the components of a malaria vaccine.
注入循环系统数分钟后，疟原虫子孢子进入肝细胞。入侵过程的速度和特异性表明这是受体介导的。恶性疟原虫环子孢子（CS）蛋白的区域II序列包含一个九肽（WSPCSVTCG），该序列在所有已测序的CS蛋白中高度保守，包括来自伯氏疟原虫的CS蛋白。我们发现，基于恶性疟原虫区域II序列的两种肽，P18（EWSPCSVTCGNGIQVRIK）和P32（IEQYLKKIKNS ISTEWSPCSVTCGNGIQVRIK），在体外显著抑制伯氏疟原虫子孢子对Hep-G2细胞的入侵。如果在子孢子入侵之前将任何一种肽与Hep-G2细胞预孵育，这种抑制作用会增强。我们证实区域II是子孢子与肝细胞受体的配体；此外，尽管在九肽序列周围恶性疟原虫和伯氏疟原虫区域II序列之间存在一些差异（66%的同源性），但基序序列的功能特性并未受到影响。由于保守基序代表了疟原虫子孢子入侵肝细胞所涉及的关键序列，针对区域II的抗体应该能够抑制子孢子对肝细胞的入侵。事实上，我们发现针对基于恶性疟原虫的肽P32产生的多克隆抗体抑制了伯氏疟原虫子孢子对Hep-G2细胞的入侵。此外，用P32免疫的近交系小鼠（C57BL/6）对伯氏疟原虫子孢子的致命攻击具有抵抗力。我们的结果表明，CS蛋白的保守区域II包含关键的B细胞和T细胞表位，来自人类疟原虫恶性疟原虫的此类肽序列可以在伯氏疟原虫啮齿动物模型中进行筛选，最后，区域II可被视为疟疾疫苗的有用成分之一。
