Martin M, Metzger D J, Michalek S M, Connell T D, Russell M W
Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
Infect Immun. 2000 Jan;68(1):281-7. doi: 10.1128/IAI.68.1.281-287.2000.
Cholera toxin (CT) and the heat-labile enterotoxin of Escherichia coli (LT-I) are members of the serogroup I heat-labile enterotoxins (HLT) and can serve as systemic and mucosal adjuvants. However, information is lacking with respect to the structurally related but antigenically distinct serogroup II HLT, LT-IIa and LT-IIb, which have different binding specificities for ganglioside receptors. The purpose of this study was to assess the effectiveness of LT-IIa and LT-IIb as mucosal adjuvants in comparison to the prototypical type I HLT, CT. BALB/c mice were immunized by the intranasal (i.n.) route with the surface protein adhesin AgI/II of Streptococcus mutans alone or supplemented with an adjuvant amount of CT, LT-IIa, or LT-IIb. Antigen-specific antibody responses in saliva, vaginal wash, and plasma were assayed by enzyme-linked immunosorbent assay. Mice given AgI/II with LT-IIa or LT-IIb by the i.n. route had significantly higher mucosal and systemic antibody responses than mice immunized with AgI/II alone. Anti-AgI/II immunoglobulin A (IgA) antibody activity in saliva and vaginal secretions of mice given AgI/II with LT-IIa or LT-IIb was statistically similar in magnitude to that seen in mice given AgI/II and CT. LT-IIb significantly enhanced the number of AgI/II-specific antibody-secreting cells in the draining superficial cervical lymph nodes compared to LT-IIa and CT. LT-IIb and CT induced significantly higher plasma anti-AgI/II IgG titers compared to LT-IIa. When LT-IIb was used as adjuvant, the proportion of plasma IgG2a relative to IgG1 anti-AgI/II antibody was elevated in contrast to the predominance of IgG1 antibodies promoted by AgI/II alone or when CT or LT-IIa was used. In vitro stimulation of AgI/II-specific cells from the superficial lymph nodes and spleen revealed that LT-IIa and LT-IIb induced secretion of interleukin-4 and significantly higher levels of gamma interferon compared to CT. These results demonstrate that the type II HLT LT-IIa and LT-IIb exhibit potent and distinct adjuvant properties for stimulating immune responses to a noncoupled protein immunogen after mucosal immunization.
霍乱毒素（CT）和大肠杆菌不耐热肠毒素（LT-I）属于血清群I不耐热肠毒素（HLT），可作为全身和黏膜佐剂。然而，关于结构相关但抗原性不同的血清群II HLT，即LT-IIa和LT-IIb，目前缺乏相关信息，它们对神经节苷脂受体具有不同的结合特异性。本研究的目的是评估与典型的I型HLT即CT相比，LT-IIa和LT-IIb作为黏膜佐剂的有效性。将BALB/c小鼠通过鼻内（i.n.）途径单独用变形链球菌表面蛋白黏附素AgI/II免疫，或补充佐剂量的CT、LT-IIa或LT-IIb。通过酶联免疫吸附测定法检测唾液、阴道灌洗液和血浆中的抗原特异性抗体反应。通过i.n.途径给予AgI/II与LT-IIa或LT-IIb的小鼠，其黏膜和全身抗体反应显著高于单独用AgI/II免疫的小鼠。给予AgI/II与LT-IIa或LT-IIb的小鼠唾液和阴道分泌物中的抗AgI/II免疫球蛋白A（IgA）抗体活性在统计学上与给予AgI/II和CT的小鼠相似。与LT-IIa和CT相比，LT-IIb显著增加了引流的浅表颈淋巴结中AgI/II特异性抗体分泌细胞的数量。与LT-IIa相比，LT-IIb和CT诱导的血浆抗AgI/II IgG滴度显著更高。当使用LT-IIb作为佐剂时，与单独使用AgI/II或使用CT或LT-IIa时促进的IgG1抗体占优势相比，血浆IgG2a相对于IgG1抗AgI/II抗体的比例升高。对浅表淋巴结和脾脏中AgI/II特异性细胞的体外刺激显示，与CT相比，LT-IIa和LT-IIb诱导白细胞介素-4分泌以及γ干扰素水平显著更高。这些结果表明，II型HLT LT-IIa和LT-IIb在黏膜免疫后对刺激针对非偶联蛋白免疫原的免疫反应表现出强大且独特的佐剂特性。
