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Production and bioactivity of anti-Streptococcus equinus antibodies.

G. Balieiro Neto




Production and bioactivity of anti-Streptococcus equinus antibodies.
G. Balieiro Neto*1, L. E. Ferreira2, A. Daurea2, L. Bertelli2. 1Animal Science Institute of Department of Agriculture and Food Supply Ribeir�o Preto, S�o Paulo, Brazil, 2Premix Ribeir�o Preto, S�o Paulo, Brazil.

Organisms previously classified as Streptococcus bovis (i.e., S. equinus) are common in the rumen and feces and have been described as commensal bacteria in humans and animals. They may act as opportunistic pathogens contributing to ruminal acidosis and mastitis. Any microorganism that colonizes the rumen must possess the capability of adherence to the ruminal surface for multiplication. The adhesins responsible for bacterial adhesion are generally targets of antibodies that can inhibit attachment. In this study we evaluated the production and bioactivity of antibodies against S. equinus. Twenty-four hens allocated to 8 cages were divided in 2 groups: one group was immunized with the control vaccine (adjuvant plus phosphate-buffered saline) and the other was administered the test vaccine containing S. equinus strain JB1 as the antigen. The IgY concentrations in egg yolks were determined with Chicken IgY ELISA Kit Fine Test and analyzed by the unpaired t-test. IgY bioactivity was evaluated by plate trapped antigens-enzyme linked immuno sorbent assay (PTA-ELISA). In the PTA-ELISA 5.3 � 108 colony-forming units/mL of S. equinus were pre-coated onto the wells of a multi well-plate for both control and sample testing. These wells were incubated with serially diluted anti-S. equinus antibody and then with the second antibody-enzyme conjugate followed by the chromogenic enzyme substrate in duplicate. The control and test production were 22.5 and 104.1 mg/yolk of IgY, respectively. The PTA-ELISA revealed high yield bioactivity of IgY against S. equinus, and the 1:16 dilution was selected for greater formation of antibody-antigen complexes. Both antibody affinity and the accessibility of epitopes on the plate are critical factors in determining whether the diluted antibody levels exceed the threshold required for complex formation. These results provide a good approximation of the optimal relationship between antigen and antibody, guiding the dosages in further animal tests.

Keywords: antibody-antigen complex, immunization, microbiome.