Anti-Staphylococcus Enterotoxin B Polyclonal antibody

A new modality in antibody engineering has emerged in which the antigen affinity is designed to be pH dependent (PHD). In particular, combining high affinity binding at neutral pH with low affinity binding at acidic pH leads to a novel antibody that can more effectively neutralize the target antigen while avoiding antibody-mediated antigen accumulation. Here, we studied how the in vivo pharmacokinetics of the superantigen, Staphylococcal enterotoxin B (SEB), is affected by an engineered antibody with pH-dependent binding. PHD anti-SEB antibodies were engineered by introducing mutations into a high affinity anti-SEB antibody, 3E2, by rational design and directed evolution. Three antibody mutants engineered in the study have an affinity at pH 6.0 that is up to 68-fold weaker than the control antibody. The pH dependency of each mutant, measured as the pH-dependent affinity ratio (PAR - ratio of affinity at pH 7.4 and pH 6.0), ranged from 6.7-11.5 compared to 1.5 for the control antibody. The antibodies were characterized in mice by measuring their effects on the pharmacodynamics and pharmacokinetics (PK) of SEB after co-administration. All antibodies were effective in neutralizing the toxin and reducing the toxin-induced cytokine production. However, engineered PHD antibodies led to significantly faster elimination of the toxin from the circulation than wild type 3E2. The area under the curve computed from the SEB PK profile correlated well with the PAR value of antibody, indicating the importance of fine tuning the pH dependency of binding. These results suggest that a PHD recycling antibody may be useful to treat intoxication from a bacterial toxin by accelerating its clearance.

Staphylococcal enterotoxin B (SEB) has been documented to be implicated in the pathogenesis of liver injury in the experimental models of hepatitis. However, the underlying mechanism of SEB-induced acute liver injury (ALI) remains to be further explored. In our study, we explored the therapeutic effectiveness of berberine (BBR), a natural isoquinoline alkaloid, in the SEB-induced ALI. In our study, we found that injection of SEB into D-galactosamine (D-gal)-sensitized mice induced ALI, as demonstrated by an increase of levels of alanine aminotransferase and aspartate aminotransferase, massive infiltration of immune cells into the liver, and pro-inflammatory cytokine release. However, intragastric administration of BBR attenuated SEB-induced ALI in mice. Meanwhile, we discovered that BBR treatment suppressed activation of splenocytes and pro-inflammatory cytokine release in SEB-stimulated splenocytes. Moreover, mechanistic analyses demonstrated that BBR was effective at inhibiting the expression of class I HDAC, but not class II, in SEB-stimulated splenocytes. Furthermore, trichostatin A, a standard HDAC inhibitor, alleviated activation of splenocytes and pro-inflammatory cytokine release in SEB-stimulated splenocytes. Taken together, we inferred from these results that BBR attenuated SEB-mediated ALI through repressing the class I HDAC enzyme, suggesting that BBR may constitute a novel therapeutic modality to prevent SEB-mediated inflammation and ALI.