Katz J, Harmon C C, Buckner G P, Richardson G J, Russell M W, Michalek S M
Department of Microbiology, University of Alabama, Birmingham 35294.
Infect Immun. 1993 May;61(5):1964-71. doi: 10.1128/iai.61.5.1964-1971.1993.
The B subunit of cholera toxin (CTB) has been shown to augment mucosal responses to microbial virulence antigens, including those of Streptococcus mutans, which is the principal etiologic agent of dental caries. In the present study, the surface fibrillar protein antigen of S. mutans, antigen I/II (Ag I/II), was chemically coupled to CTB (Ag I/II-CTB), and the conjugate was examined for its effectiveness in inducing salivary immune responses protective against S. mutans infection. Weanling Fischer rats were given Ag I/II-CTB (50 micrograms) by the intranasal route and then orally infected with a virulent strain of S. mutans. Gnotobiotic or conventional rats were given two or three additional immunizations, respectively, at about 2-week intervals. One week after each immunization, individual serum, saliva, and fecal samples were collected and stored frozen until assayed for antibody activity to Ag I/II and cholera toxin (CT) by an enzyme-linked immunosorbent assay. The rats were sacrificed 1 week after the last immunization, when mandibles were also collected from individual rats for assessment of S. mutans levels in plaque and caries activity. Rats immunized only or both immunized and infected showed a salivary immunoglobulin A (IgA) anti-Ag I/II response which reached significantly (P < 0.05) higher levels than those seen in nonimmunized, infected controls. A salivary IgA anti-Ag I/II response was also seen in rats infected only with S. mutans. Essentially no salivary antibody activity to CT was detected. Some serum anti-Ag I/II and anti-CT responses were seen in immunized animals. Serum IgG anti-Ag I/II responses were seen in immunized, infected rats and also in infected-only rats, suggesting that the responses were a result of infection with S. mutans. The immunized and infected rats had significantly (P < 0.05) lower levels of S. mutans in plaque and lower caries activity than nonimmunized, infected rats. These results indicated that intranasal immunization of rats with Ag I/II-CTB induced a protective salivary immune response which was associated with a reduction in S. mutans colonization and S. mutans-induced dental caries.
霍乱毒素B亚基（CTB）已被证明可增强对微生物毒力抗原的黏膜反应，包括变形链球菌的抗原，变形链球菌是龋齿的主要病原体。在本研究中，将变形链球菌的表面纤维状蛋白抗原I/II（Ag I/II）与CTB化学偶联（Ag I/II-CTB），并检测该偶联物在诱导唾液免疫反应以抵御变形链球菌感染方面的有效性。给断奶的Fischer大鼠经鼻内途径给予Ag I/II-CTB（50微克），然后经口感染一株有毒力的变形链球菌。无菌或普通大鼠分别每隔约2周再进行2次或3次免疫接种。每次免疫接种1周后，收集个体血清、唾液和粪便样本并冷冻保存，直至通过酶联免疫吸附测定法检测其对Ag I/II和霍乱毒素（CT）的抗体活性。在最后一次免疫接种1周后处死大鼠，此时也从个体大鼠采集下颌骨，以评估菌斑中变形链球菌水平和龋齿活性。仅免疫或既免疫又感染的大鼠出现唾液免疫球蛋白A（IgA）抗Ag I/II反应，其水平显著（P<0.05）高于未免疫、感染的对照组。仅感染变形链球菌的大鼠也出现唾液IgA抗Ag I/II反应。基本上未检测到唾液对CT的抗体活性。在免疫动物中观察到一些血清抗Ag I/II和抗CT反应。在免疫、感染的大鼠以及仅感染的大鼠中均观察到血清IgG抗Ag I/II反应，这表明这些反应是变形链球菌感染的结果。与未免疫、感染的大鼠相比，免疫且感染的大鼠菌斑中变形链球菌水平显著（P<0.05）降低，龋齿活性也较低。这些结果表明，用Ag I/II-CTB对大鼠进行鼻内免疫可诱导保护性唾液免疫反应，这与变形链球菌定植减少和变形链球菌诱导的龋齿减少有关。
