Effect of monoclonal antibodies on the colonization of rats by Streptococcus sobrinus

Local passive immunization has been suggested as a method of preventing colonization of teeth by mutans streptococci. In this study we describe the effect of local application of monoclonal antibodies (Mabs) on the colonization of Streptococcus sobrinus. The rats, 37 days old, were divided in 4 groups: group 1 received Mab OMVU10 (Mab reactive with Antigen B of S. sobrinus, IgG2b), group 2 received Clone 24 (Mab reactive with lipid A of Escherichia coli, IgG2b), group 3 received uninoculated culture medium, and group 4 received phosphate-buffered saline (PBS). Mabs were applied 6 times on the surfaces of the molars and the labial surfaces of the incisors of the rats, on days 37, 40, 44, 46, 49 and 54 after birth. After the third application of Mabs, all rats were inoculated with S. sobrinus (day 45). Subsequently, the rats were fed a cariogenic diet containing 20% sucrose and 5% glucose. The rats were killed 34 days after inoculation and the maxillary molars were extracted and homogenized in order to determine the numbers of S. sobrinus. The proportions of S. sobrinus, expressed as a percentage of the total cultivable microflora, in rats which received OMVU10 (group 1) were 23.1 +/- 14.8%, whereas in rats which received Clone 24, culture medium or PBS the levels were 34.5 +/- 11.3%, 40.7 +/- 14.9% and 36.7 +/- 9.7%, respectively. Statistical analysis showed that the level of colonization of rats which received OMVU10 was significantly lower than that of rats which received Clone 24, culture medium or PBS (p < 0.001, p < 0.013 and p < 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)