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Review
. 2021 Apr 1;9(4):337.
doi: 10.3390/vaccines9040337.

The Bacterial and Viral Agents of BRDC: Immune Evasion and Vaccine Developments

Rachael Lynda Bell  1 , Hannah Louise Turkington  1 , Sara Louise Cosby  1   2
Affiliations
Review

The Bacterial and Viral Agents of BRDC: Immune Evasion and Vaccine Developments

Rachael Lynda Bell et al. Vaccines (Basel). .

Abstract

Bovine respiratory disease complex (BRDC) is a multifactorial disease of cattle which presents as bacterial and viral pneumonia. The causative agents of BRDC work in synergy to suppress the host immune response and increase the colonisation of the lower respiratory tracts by pathogenic bacteria. Environmental stress and/or viral infection predispose cattle to secondary bacterial infections via suppression of key innate and adaptive immune mechanisms. This allows bacteria to descend the respiratory tract unchallenged. BRDC is the costliest disease among feedlot cattle, and whilst vaccines exist for individual pathogens, there is still a lack of evidence for the efficacy of these vaccines and uncertainty surrounding the optimum timing of delivery. This review outlines the immunosuppressive actions of the individual pathogens involved in BRDC and highlights the key issues in the development of vaccinations against them.

Keywords: bacterial agents; bovine respiratory disease complex (BRDC); immune evasion; immunity; respiratory viruses; vaccine development.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Differential infection of upper and lower respiratory epithelia and subsequent bacterial colonisation. Viral infection leads to inhibition of function and cell death. This both increases bacterial adherence to, and colonisation, of the lower respiratory tracts. (Created in BioRender.com, accessed on 24 March 2021).
Figure 2
Figure 2
Leukocyte evasion and inhibition by BRDC pathogens. Viral and bacterial infections inhibit functionality, impact signalling and induce cytotoxicity in cells of the adaptive and innate immune response. (Created in BioRender.com, accessed on 24 March 2021).
Figure 3
Figure 3
Inter- and intra-cell signalling dysregulation induced by bacterial and viral infections. Interferences with MHC protein expression and cytokine regulation result in limited anti-viral and bacterial immune responses and poor immune memory production. (Created in BioRender.com, accessed on 24 March 2021).
Figure 4
Figure 4
Viral reactivation from latency and establishment in sites of immune tolerance by BoHV-1 and BVDV, respectively. BoHV-1 is commonly a lifelong infection, arising in times of stress. BVDV maintains persistent infections within herds due to non-cytopathic spread from cow to foetus. (Created in BioRender.com, accessed on 24 March 2021).
See this image and copyright information in PMC

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