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. 2019 Nov 4;7(4):176.
doi: 10.3390/vaccines7040176.

A Marker-Free Bordetella bronchiseptica aroA/ bscN Double Deleted Mutant Confers Protection Against Lethal Challenge

Weicheng Ai  1   2 , Zhong Peng  3   4 , Fei Wang  5   6 , Yue Zhang  7   8 , Sisi Xie  9   10 , Wan Liang  11   12   13 , Lin Hua  14   15 , Xiangru Wang  16   17 , Huanchun Chen  18   19 , Bin Wu  20   21
Affiliations

A Marker-Free Bordetella bronchiseptica aroA/ bscN Double Deleted Mutant Confers Protection Against Lethal Challenge

Weicheng Ai et al. Vaccines (Basel). .

Abstract

Bordetella bronchiseptica is a leading cause of swine respiratory disorders which depict a great threat to well-flourished porcine industry. Vaccination remains an effective way for the prevention of B. bronchiseptica infections, as live B. bronchiseptica vaccines possess many advantages compared to inactivated vaccines and/or sub-unit vaccines, however, their safety is not up to the mark. In present study, we constructed marker-free aroA/bscN double deleted B. bronchiseptica QH09 through two-step homologous recombination strategy. Our data showed that QH09 attenuated virulence to mice compared with the parent aroA deleted B. bronchiseptica QH0814. We also found that QH09 meets the vaccine safety standards, upon challenge in piglets, did not cause any visible clinical signs or lesions on organs. Finally, we demonstrated that vaccination of QH09 activated the systemic as well as the mucosal immunity in pigs and provided protection against lethal bacterial challenge. These findings suggest that the aroA/bscN double deleted B. bronchiseptica QH09 may be an effective vaccine candidate, with safety assurance of animals against B. bronchiseptica infections.

Keywords: Bordetella bronchiseptica; aroA/bscN double deleted mutant; attenuated live vaccine; immune efficacy; safety.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Strategy for the construction of the marker-free aroA/bscN double deleted B. bronchiseptica strain QH09. (A) Schematic diagram showing the strategy for the construction of the aroA/bscN-deletion strain. (B) PCR determination of the bscN-deletion in the aroA-deletion strain QH0814. M: DL 15,000 DNA marker; Lane 1: ddH2O as the negative control; Lane 2: QH0814 as the positive control (2661-bp); Lanes 3–4: bscN-deletion (2120-bp).
Figure 2
Figure 2
Histological analysis on pig lungs challenged with QH09, HH0809, and PBS in the pig safety tests (bar 100 μm). Panel A is a lung histological section from a pig challenged with PBS; Panel B is a lung histological section from a pig challenged with QH09 at 3 × 1011 CFU; Panel C is a lung histological section from a pig challenged with HH0809 at 1 × 1011 CFU.
Figure 3
Figure 3
ELISA titers of IgG in serum (A), IgA in serum (B), sIgA in BALF (C), in piglets induced by the attenuated live vaccine (QH09), the inactivated vaccine (HH0809), and PBS. “*” p < 0.5.
Figure 4
Figure 4
Lesions on the nasal cavities of pigs immunized with different vaccines after infection. (A) lesions on the nasal cavities of pigs immunized with the attenuated live vaccine (QH09); (B) lesions on the nasal cavities of pigs immunized with the inactivated vaccine (HH0809); (C) lesions on the nasal cavities of pigs immunized with PBS; (D) the nasal cavities of the healthy pigs.
See this image and copyright information in PMC

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