Protein antigens I, I/II, II, and III were prepared from Streptococcus mutans (serotype c). Their immunogenicities and protective effects against dental caries were investigated in 40 rhesus monkeys kept entirely on a human-type diet, containing about 15% sucrose. Antigens I, I/II and, to a lesser extent, antigen II induced significant reductions in dental caries, as compared with sham-immunized monkeys. This was achieved with 1 or 2 doses of antigen, the first of which was administered with adjuvant (Freund incomplete adjuvant or aluminum hydroxide). There was no reduction in caries in monkeys immunized with antigen III. The reduction in caries in the animals immunized with antigens I or I/II was comparable to that in monkeys immunized with whole cells. Protection against caries was associated predominantly with serum and gingival crevicular fluid immunoglobulin G antibodies, which appeared to be directed against the antigen I determinant, but antibodies to antigen II, though not to antigen III, were also protective.

Local passive immunization with monoclonal antibodies (Mc Ab) to Streptococcus mutans was attempted as an alternative approach to active systemic immunization. We prepared an immunoglobulin G class Mc Ab to the cell surface protein determinant of streptococcal antigen I/II and applied it repeatedly to the teeth of rhesus monkeys. This resulted in decreased colonization by S. mutans in fissures and smooth surfaces of teeth and no dental caries, unlike the results in control animals, which developed caries and showed a high proportion of S. mutans on their teeth. There was no significant difference in serum, salivary, or gingival fluid antibodies to S. mutans between the two groups of animals. Any objections raised over systemic immunization inducing cross-reactive antibodies are therefore overcome by local passive immunization. The mechanism of prevention of colonization has not been established, but we postulate that the Mc Ab which is directed against an important cell surface antigenic determinant of S. mutans (streptococcal antigen I/II) prevents adherence of S. mutans to the acquired pellicle on the tooth surface. S. mutans reacts with the Mc Ab and becomes opsonized, phagocytosed, and killed by the local gingival traffic of neutrophils.

No abstract

SWAP-70 is a component of an enzyme complex that recombines Ig switch regions in vitro. We report here the cloning of the human cDNA and its B lymphocyte-specific expression. Although its sequence contains three nuclear localization signals, in small resting B cells, SWAP-70 is mainly found in the cytoplasm. On stimulation, SWAP-70 translocates to the nucleus. In activated, class-switching B cell cultures, it is associated with membrane IgG, but not IgM. The membrane Ig association requires a functional pleckstrin homology domain and is controlled by the C terminus. We suggest that SWAP-70 is involved not only in nuclear events but also in signaling in B cell activation.