The extended leader peptide of Haemophilus parasuis trimeric autotransporters conditions their protein expression in Escherichia coli

- The VtaAs are surface-exposed proteins belonging to the type V secretion system.
- VtaAs of H. parasuis are targets for vaccine and diagnostic tool development.
- Optimal expression of recombinant VtaAs require deletion of the ESPR.
- Optimal expression was achieved with 10-200 ng/mL of AHT at 2-4 h post-induction.
- Purification yields depend on the size of the recombinant VtaA.

Trimeric autotransporters are surface-exposed proteins of Gram-negative bacteria belonging to the type V secretion system. They are involved in virulence and are targets for vaccine and diagnostic tool development, so optimal systems for their expression and purification are required. In the present study, the impact of the extended leader peptide of the Haemophilus parasuis virulence-associated trimeric autotransporters (VtaA) in its production as recombinant proteins in Escherichia coli was evaluated. The 13 genes encoding the VtaA1 to VtaA13 passenger domains of the strain Nagasaki were cloned in the pASK-IBA33plus plasmid and expressed in E. coli. Recombinant protein production was higher for truncated forms in which the entire leader peptide was deleted, and the recombinant protein accumulated in the cytoplasm of the cells. The yield of protein production of the different VtaAs was size dependent, and reached maximal amount at 2-4 h post -induction. The optimization of these conditions allowed to scale-up the production to obtain enough recombinant protein to immunize large animals.