Which subunit of PTx is least suitable for generating a vaccine against B. pertussis?

• A. S1
• B. S2
• C. S4
• D. S5

Answer: (A)

The subunit S1 of pertussis toxin (PTx) is least suitable for generating a vaccine against Bordetella pertussis because it is primarily responsible for the toxic effects of the toxin and plays a critical role in facilitating the bacterium's pathogenicity. While targeting S1 may elicit an immune response, it might not effectively neutralize the symptoms caused by the other components of the toxin, or contribute to overall bacterial clearance.

In contrast, other subunits like S2, S4, and S5 are more involved in the structural integrity or the overall immunogenicity of the toxin, making them potentially more effective targets for vaccine development. These subunits may elicit a more comprehensive immune response that better targets the bacteria, potentially leading to stronger protection against infection.

By focusing on subunits that contribute to structural and functional aspects of PTx, vaccines can be designed to prevent the disease more effectively by provoking an immune response that can neutralize the effects of the toxin and promote clearance of the bacterium.