Proteome Analysis Is a Valuable Tool to Monitor Antigen Expression during Upstream Processing of Whole-Cell Pertussis Vaccines

Physicochemical
and immunochemical assays were applied to substantiate
the relation between upstream processing and the quality of whole-cell
pertussis vaccines. Bordetella pertussis bacteria
were cultured on a chemically defined medium using a continuous cultivation
process in stirred tank reactors to obtain uniform protein expression.
Continuous culture favors the consistent production of proteins known
as virulence factors. Magnesium sulfate was added during the steady
state of the culture in order to diminish the expression of virulence
proteins. Changes in gene expression and antigen composition were
measured by microarrays, mass spectrometry and ELISA. Transcriptome
and proteome data revealed high similarity between the biological
triplicates demonstrating consistent cultivation of B. pertussis. The addition of magnesium sulfate resulted in an instant downregulation
of the virulence genes in B. pertussis, but
a gradual decrease of virulence proteins. The quantity of virulence
proteins concurred highly with the potency of the corresponding whole-cell
pertussis vaccines, which were determined by the Kendrick test. In
conclusion, proteome analysis provided detailed information on the
composition and proportion of virulence proteins present in the whole-cell
preparations of B. pertussis. Moreover, proteome
analysis is a valuable method to monitor the production process of
whole-cell biomass and predict the product quality of whole-cell pertussis
vaccines.