Howard R F, Jensen J B, Franklin H L
Seattle Biomedical Research Institute, Washington 98109.
Infect Immun. 1993 Jul;61(7):2960-5. doi: 10.1128/iai.61.7.2960-2965.1993.
Immunization of monkeys with the 82-kDa rhoptry protein (p82) of Plasmodium falciparum can protect them against a lethal blood stage challenge, and monoclonal antibodies to p82 inhibit parasite growth in vitro. The role that a p82-specific immune response might play in human immunity to the parasite is not known. To determine to what extent humans produce antibodies to p82 following infection with P. falciparum, sera from individuals believed to be hyperimmune, semi-immune, or never infected with the parasite were examined. Portions of the p82 gene were expressed separately as fusion proteins and used on immunoblots to test for antibodies to the recombinant proteins. All but 1 of the 30 immune sera possessed antibodies to p82, while nonimmune sera produced, at best, only a marginal signal to the fusion proteins. The signal intensity produced with the human immune sera depended on the region of p82 being assayed, with the N-terminal 37% of p82 producing stronger signals than more C-terminal parts of p82. This N-terminal domain contains a tandem octapeptide repeat (consensus KSSSPSXT/V) of the structure (repeat)2-Q-T-S-G-S/L-(repeat)3. It is shown here that the sequence of this repetitive motif is conserved among four parasite isolates at both the nucleotide and amino acid levels; the five-residue repeat interruption peptide QTSGS/L separating the two sets of repeats contains the only amino acid substitution (Ser or Leu) detected in this region to date. Despite their conservation of structure, the repeats do not appear to be the only epitope recognized by the human antibodies, since sera which recognize the N-terminal fusion protein containing the repeats also bind a related protein after truncation and removal of the repeats. These results indicate that the structurally conserved p82 molecule contains multiple B-cell epitopes and is likely to be immunogenic in most individuals during natural infections with P. falciparum. These observations are consistent with the idea that antibodies to p82 generated during parasite infection have a role in the development of immunity to the organism.
用恶性疟原虫的82-kDa棒状体蛋白（p82）免疫猴子可使其免受致命的血液阶段攻击，并且针对p82的单克隆抗体在体外可抑制寄生虫生长。p82特异性免疫反应在人类对该寄生虫的免疫中可能发挥的作用尚不清楚。为了确定人类在感染恶性疟原虫后产生针对p82的抗体的程度，检测了被认为是超免疫、半免疫或从未感染过该寄生虫的个体的血清。p82基因的部分片段分别作为融合蛋白表达，并用于免疫印迹以检测针对重组蛋白的抗体。30份免疫血清中除1份外均含有针对p82的抗体，而非免疫血清对融合蛋白最多仅产生微弱信号。人类免疫血清产生的信号强度取决于所检测的p82区域，p82的N端37%产生的信号比p82更靠C端的部分更强。该N端结构域包含一个串联八肽重复序列（共有序列KSSSPSXT/V），结构为（重复）2-Q-T-S-G-S/L-（重复）3。本文表明，该重复基序的序列在四个寄生虫分离株的核苷酸和氨基酸水平上均保守；分隔两组重复序列的五残基重复中断肽QTSGS/L包含迄今为止在该区域检测到的唯一氨基酸取代（丝氨酸或亮氨酸）。尽管其结构保守，但这些重复序列似乎并非人类抗体识别的唯一表位，因为识别包含重复序列的N端融合蛋白的血清在截断和去除重复序列后也会结合一种相关蛋白。这些结果表明，结构保守的p82分子包含多个B细胞表位，并且在大多数个体自然感染恶性疟原虫期间可能具有免疫原性。这些观察结果与寄生虫感染期间产生的针对p82的抗体在对该生物体的免疫发展中起作用的观点一致。
