# Antibody signatures elicited by potent and subpotent whole-cell pertussis vaccines in mice

## TL;DR

Researchers explored using antibody profiles in mice to replace a burdensome mouse-based test for checking the potency of whole-cell pertussis vaccines.

## Contribution

The study identifies distinct antibody signatures in mice that correlate with vaccine potency, offering a potential alternative to the Kendrick assay.

## Key findings

- Distinct antibody reactivity profiles were observed for potent and subpotent vaccines against over 30 B. pertussis antigens.
- Thermal stress reduced vaccine potency by over 10-fold in a mouse model of lung clearance.
- Identified antigens are known virulence factors or react with human convalescent sera, linking potency to immunity.

## Abstract

Inactivated, whole-cell pertussis (wP) vaccines remain at the frontline in the global fight against the resurgence of whooping cough, especially in low- and middle-income countries. However, the reliance on the intracerebral mouse potency test (ic-MPT or Kendrick assay) as the standard batch release assay is extremely burdensome for commercial wP vaccine production. The ic-MPT is technically challenging, labor intensive, and incongruous with modern animal welfare guidelines. Replacing the ic-MPT with a whole-cell Bordetella pertussis enzyme-linked immunosorbent assay, the so-called pertussis serology potency test, has shown promise but has been difficult to implement in practice. In this report, we tested the hypothesis that potent and subpotent wP vaccines have distinct serological profiles in mice that could be developed as a substitute for the ic-MPT. We established an accelerated decay (thermal stress) protocol in which wP, in the context of diphtheria-tetanus-whole-cell pertussis, was rendered >10-fold less effective than unstressed vaccine when evaluated in a mouse model of B. pertussis lung clearance following intranasal challenge. We then screened immune sera on a limited B. pertussis Tahoma I proteome array and identified >30 antigens whose antibody reactivity profiles either increased, decreased, or were unchanged as a function of wP potency. Moreover, virtually all the “indicator” antigens identified are known virulence factors or reactive with human convalescent sera, thereby establishing a potential link between wP potency and pertussis infection and immunity. These results support the development of a limited B. pertussis antigen array as a stability-indicating surrogate potency assay for the ic-MPT.

Whooping cough (pertussis) is a highly contagious respiratory disease caused by the Gram-negative bacterium, Bordetella pertussis. Globally, tens of millions of whole-cell pertussis (wP) vaccines are administered annually. Whole-cell pertussis vaccines are logistically complex to manufacture and get to market because of the need for each batch of vaccine to be evaluated in a highly laborious and challenging potency test known as the Kendrick assay, which involves mouse intracerebral challenges with B. pertussis. In this report, we describe efforts to develop a serology-based substitute for the Kendrick assay that relies on profiling antibody responses to wP vaccines.