Glutaraldehyde modifies the catalytic and binding subunits of pertussis toxin, affecting its toxicity and immunogenicity

Pertussis toxin (PTx) is a key virulence factor of the organism Bordetella pertussis, which must undergo proper detoxification as a component of acellular pertussis vaccines. Chemical detoxification using glutaraldehyde causes significant changes to the toxin surface, reducing its toxicity and potentially affecting its antigen properties. Although previous studies have thoroughly investigated the toxicity of chemically detoxified PT toxoid (PTd), there is limited understanding regarding how detoxification influences its antigenic properties and immunogenicity. Moreover, the specific parameters—such as glutaraldehyde concentration and buffer pH—and their effects on toxicity and immunogenicity are poorly defined. This study began by examining the influence of these parameters on the structural profiles of PTd. Subsequently, the toxicity and antigenic properties of PTd were characterized in vitro. Next, neutralizing epitopes remaining on PTd were quantified to assess the antigenicity. Finally, the immunogenicity of acellular pertussis vaccine candidates containing PTd was further evaluated in vivo. We found that the glutaraldehyde treatment caused more dramatic structural changes in B oligomer than A protomer of PTx, independent of variance in glutaraldehyde concentration and buffer pH. As a result, residual toxicity was reduced, and antigenic properties were altered. Following this, changes in antigenic properties were proved to be related to compromised immunogenicity. This study demonstrates that glutaraldehyde modulates the two functional domains of PTx, affecting both its toxicity and immunogenicity; two factors-glutaraldehyde concentration and buffer pH reduce the biochemical activities by bias influencing A protomer and B-oligomer. This work also underscores the importance of maintaining a delicate balance between immunogenicity and toxicity in detoxification.