Enriquez F J, Riggs M W
Department of Veterinary Science and Microbiology, University of Arizona, Tucson, Arizona 85721, USA.
Infect Immun. 1998 Sep;66(9):4469-73. doi: 10.1128/IAI.66.9.4469-4473.1998.
Cryptosporidium parvum is an important diarrhea-causing protozoan parasite of immunocompetent and immunocompromised hosts. Immunoglobulin A (IgA) has been implicated in resistance to mucosal infections with bacteria, viruses, and parasites, but little is known about the role of IgA in the control of C. parvum infection. We assessed the role of IgA during C. parvum infection in neonatal mice. IgA-secreting hybridomas were developed by using Peyer's patch lymphocytes from BALB/c mice which had been orally inoculated with viable C. parvum oocysts. Six monoclonal antibodies (MAbs) were selected for further study based on indirect immunofluorescence assay reactivity with sporozoite and merozoite pellicles and the antigen (Ag) deposited on glass substrate by gliding sporozoites. Each MAb was secreted in dimeric form and recognized a 23-kDa sporozoite Ag in Western immunoblots. The Ag recognized comigrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with P23, a previously defined neutralization-sensitive zoite pellicle Ag. MAbs were evaluated for prophylactic or therapeutic efficacy against C. parvum, singly and in combinations, in neonatal BALB/c mice. A combination of two MAbs given prophylactically prior to and 12 h following oocyst challenge reduced the number of intestinal parasites scored histologically by 21.1% compared to the numbers in mice given an isotype-matched control MAb (P < 0.01). Individual MAbs given therapeutically in nine doses over a 96-h period following oocyst challenge increased efficacy against C. parvum infection. Four MAbs given therapeutically each reduced intestinal infection 34.4 to 42.2% compared to isotype-matched control MAb-treated mice (P < 0.05). One MAb reduced infection 63.3 and 72. 7% in replicate experiments compared to isotype-matched control MAb-treated mice (P < 0.0001). We conclude that IgA MAbs directed to neutralization-sensitive P23 epitopes may have utility in passive immunization against murine C. parvum infection.
微小隐孢子虫是免疫功能正常和免疫功能低下宿主中一种重要的致腹泻原生动物寄生虫。免疫球蛋白A（IgA）与抵抗细菌、病毒和寄生虫的黏膜感染有关，但关于IgA在控制微小隐孢子虫感染中的作用知之甚少。我们评估了IgA在新生小鼠微小隐孢子虫感染过程中的作用。通过使用来自经口接种活微小隐孢子虫卵囊的BALB/c小鼠的派尔集合淋巴结淋巴细胞，制备了分泌IgA的杂交瘤。基于间接免疫荧光试验与子孢子和裂殖子表膜的反应性以及滑行子孢子沉积在玻璃基质上的抗原（Ag），选择了六种单克隆抗体（MAb）进行进一步研究。每种MAb均以二聚体形式分泌，并在蛋白质免疫印迹中识别一种23 kDa的子孢子Ag。所识别的Ag在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳中与P23共迁移，P23是先前定义的对中和敏感的虫体表膜Ag。在新生BALB/c小鼠中，单独或联合评估MAb对微小隐孢子虫的预防或治疗效果。与给予同型对照MAb的小鼠相比，在卵囊攻击前和攻击后12小时预防性给予两种MAb的组合，组织学评分显示肠道寄生虫数量减少了21.1%（P < 0.01）。在卵囊攻击后的96小时内分九剂治疗性给予单个MAb，可提高对微小隐孢子虫感染的疗效。与同型对照MAb处理的小鼠相比，治疗性给予的四种MAb每种均使肠道感染减少34.4%至42.2%（P < 0.）。在重复实验中，一种MAb与同型对照MAb处理的小鼠相比，使感染减少了63.3%和72.7%（P < 0.0001）。我们得出结论，针对对中和敏感的P23表位的IgA MAb可能在被动免疫预防小鼠微小隐孢子虫感染中具有应用价值。
