How Mannheimia haemolytica defeats host defence through a kiss of death mechanism

Abstract

-Mannheimia haemolytica induced pneumonias are only observed in goats, sheep and cattle. The bacterium produces several virulence factors,whose principal ones are lipopolysaccharide and leukotoxin. The latter is cytotoxic only for ruminant leukocytes, a phenomenon that is correlated with its ability to bind and interact with the ruminant β2-integrin Lymphocyte Function-associated Antigen 1. This paper globally reviews all the information available on host-pathogen interactions underlying respiratory mannheimiosis (formerly pasteurellosis), from the stable and the Petri dish to the biochemical cascade of events triggered by the leukotoxin inside ruminant leukocytes. One conclusion can be made: the most widespread cattle respiratory disease with the most important impact on beef production worldwide, is probably due to a tiny ruminant-specific focal variation in the CD18-and/or CD11a-expressing genes.

Electronic nose responses and acute phase proteins correlate in blood using a bovine model of respiratory infection☆

“…Especially in fatal bovine respiratory diseases of feedlot calves, M. haemolytica was the most common agent identified in peracute, acute, and subacute pathologic processes [11]. Experimental models of infection have been used for decades and for many reasons; for example to understand the pathogenesis of this particular bacterium in the bovine respiratory system [12][13][14][15][16], to determine the effect of treatments [17][18][19], or to develop different vaccination protocols [20][21][22][23]. In this experimental study, calves with Mannheimia haemolytica infection were used as a model to assess host response under the defined condition of a gram-negative bacterial infection in a natural host.…”

Characterization of Mannheimia (Pasteurella) haemolytica leukotoxin interaction with bovine alveolar macrophage β2 integrins

“…The disease is a cause of considerable economic loss to the beef and dairy cattle industries of North America [56]. The bacterium produces a variety of virulence factors [8], of these a large body of evidence indicates that the leukotoxin (LktA) and lipopolysaccharide (LPS) play a significant role in the pathogenesis that lead to the lung 772 P. Thumbikat et al pathology characteristic of the disease [59]. The LktA is a calcium dependent cytolytic protein belonging to the RTX (repeats in toxin) family of cytolytic proteins.…”

Effect of Corticosteroids and Neuropeptides on the Expression of Defensins in Bovine Tracheal Epithelial Cells

“…A myriad of factors predispose cattle to this disease, including transportation, weaning, overcrowding, disrupted social structures, and other stressors in addition to precipitation, fluctuating environmental temperatures, and viral infection with bovine viral diarrhea virus, infectious bovine rhinotracheitis virus, bovine respiratory syncytial virus, and parainfluenza 3 virus (20). These factors are thought to compromise respiratory defenses, thus allowing opportunistic pathogens to proliferate, invade, and colonize the lung and incite the inflammatory reaction responsible for the clinical signs of the disease (54). The interactions between these multiple host, agent, and environmental factors are complex, and the importance of the innate pulmonary defense system and how stressors alter its function are the subject of current investigation.…”