The effect of oral administration of soluble antigen preparations containing glucosyltransferase on dental caries in hamsters was studied. Immunization was accomplished by feeding glucosyltransferase for 21 to 27 consecutive days. This immunization regimen resulted in the formation of salivary antibody, which was detected by functional inhibition of enzymatic activity and by a modified enzymelinked immunosorbent assay. A serum response also occurred in two of the three experiments performed. After infection with cariogenic Streptococcus mutans strain 6715, glucosyltransferase-fed hamsters had significantly fewer S. mutans cells recoverable from molar surfaces on six of nine occasions, compared with buffer-fed control groups. Hamsters orally immunized with glucosyltransferase also always had lower mean caries scores and mean numbers of lesions than comparably infected sham-immunized groups. The results of this study suggest that significant protection from experimental dental caries can be accomplished by oral administration of soluble antigen preparations containing glucosyltransferase.

Oral infection of mice with Trichinella spiralis has been shown to induce a potentiation of the delayed hypersensitive (DTH) response to BCG. The present investigation was initiated to determine whether nematode-induced potentiation of DTH influenced the induction and progression of a transplantable mouse tumor. B6D2F1/J mice were orally infected with 200 T. spiralis larvae 176 days preceding subcutaneous administration of 5 × 10⁵ viable B-16 melanoma cells. The antineoplastic effects of long-term nematode infection were assessed by daily observation of the animals monitoring development and progression of neoplastic nodules. Control mice developed tumors by day 28 following tumor challenge, while none of the corresponding T. spiralis-infected animals demonstrated any signs of neoplasia. All control mice died within 60 days, while none of the nematode-infected animals developed detectable neoplasms. This phenomenon suggested that the presence of well-established larval cysts was capable of stimulating host antineoplastic activity.

Mice were infected with 200 Trichinella spiralis 14 days after intravenous administration of 4 x 106 viable BCG cells. Individual groups were tested for delayed hypersensitive footpad responses at 14, 20, 29, 57, or 85 days after T. spiralis infection. An initial suppression in the 14-day test group was observed; however, mice tested at later time intervals exhibited potentiation of the 24-h footpad reaction to old tuberculin over that elicited by appropriate controls. This suggested that T. spiralis induces a potentiation of the cellular immune response to BCG. Adoptive transfer studies support the cell-mediated nature of the observed footpad reaction and indicated that the initial suppression was not due to physiological factors preventing the expression of the footpad swelling reaction.

Experiments were performed to study the effect of antibody to Streptococcus mutans glucosyltransferase (GTF) on the implantation of these organisms in hamsters. Salivary (immunoglobulin A) and serum (immunoglobulin G) antibodies to GTF and GTF-inhibiting activity were elicited by injection of GTF in Freund complete adjuvant in the salivary gland region. Sham-immunized and GTFimmunized groups were then orally challenged with approximately 107, 108, or 109 colony-forming units of cariogenic S. mutans 6715. The results were evaluated by systematically swabbing molars 4 days and approximately 4 weeks after challenge. In general, fewer GTF-immunized hamsters became infected with S. mutans after challenge with 107 or 108 organisms than did identically challenged sham-immunized hamsters. Of the animals that did become infected, fewer S. mutans colony-forming units were recovered from GTF-immunized hamsters. These results indicate that the presence of antibody to GTF can diminish the ability of S. mutans to implant in the oral cavity of immunized hamsters. Studies of the effect of immunization with glucosyltransferase (GTF) from Streptococcus mutans on experimental dental caries have revealed several features of antibody interactions with GTF. In vitro studies have shown that salivary antibody obtained by immunization with GTF from one serotype of S. mutans combines with and inhibits the activity of GTF enzyme from several other serotypes of S. mutans (14, 15). Antibody having specificity for GTF can inhibit in vitro bacterial accumulation on glass surfaces and may alter the composition so that acid may more readily diffuse through these deposits (M. A

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