Comparative study of the adjuvanticity of Bacillus thuringiensis Cry1Ab protein and cholera toxin on allergic sensitisation and elicitation to peanut

We aimed to investigate the adjuvanticity of Cry1Ab on allergic sensitisation and elicitation to peanut in mice, in comparison with cholera toxin (CT), a known mucosal Th2 adjuvant. Balb/c mice were gavaged with phosphate buffer saline (PBS) (control), peanut protein extract (PE) alone or PE co-administered either with CT or Cry1Ab. Peanut-specific IgE, IgG1 and IgG2a and Th1/Th2/Th17 cytokine secretion by splenocytes were assayed. Gavaged mice were further challenged with PE. Markers of the immediate and late phases of the allergic reaction were assayed in bronchoalveolar lavages (BAL) fluids collected 10 minutes or 36 hours after airway challenge, respectively. Sensitisation to peanut was only observed in mice receiving PE plus CT, as demonstrated by specific IgE and IgG1 production in sera and secretion of Th2 (and Th17) cytokines by splenocytes. Following challenge, mice sensitised with PE plus CT produced leukotrienes (LT) E4 and C4, then Th2/Th17-cytokines and showed eosinophil/neutrophil influx in BAL. Interestingly, LT production, Th2/Th17 cytokine release and eosinophil influx were also significant in mice gavaged with PE plus Cry-1Ab, but not with PBS or PE alone. Cry1Ab did not demonstrate adjuvant effects on oral sensitisation to peanut. However, this study shows possible adjuvant properties of Cry1Ab on the elicitation of the allergic reaction, at least in the Balb/c mouse model and in the experimental conditions used.