Invasion of Bovine Peripheral Blood Mononuclear Cells and Erythrocytes by Mycoplasma bovis

Abstract

Mycoplasma bovis is a small, cell wall-less bacterium that contributes to a number of chronic inflammatory diseases in both dairy and feedlot cattle, including mastitis and bronchopneumonia. Numerous reports have implicated M. bovis in the activation of the immune system, while at the same time inhibiting immune cell proliferation. However, it is unknown whether the specific immune-cell population M. bovis is capable of attaching to and potentially invading. Here, we demonstrate that incubation of M. bovis Mb1 with bovine peripheral blood mononuclear cells (PBMC) resulted in a significant reduction in their proliferative responses while still remaining viable and capable of gamma interferon secretion. Furthermore, we show that M. bovis Mycoplasma bovis is a small, pleomorphic cell wall-less bacterium that is known to be a major contributing factor in the development of chronic pneumonia in feedlot cattle and mastitis in dairy cows. In addition to these two diseases, M. bovis has been linked to the development of otitis, keratoconjunctivitis, and arthritis (12). These diseases have large economic impacts, resulting in losses to both beef and dairy industries in Europe, Canada, and the United States (20). Furthermore, since M. bovis lacks a cell wall, the use of antibiotics to combat infections is limited, and the development of resistance to available antibiotics (tetracyclines and spectinomycin) has been observed (20). Interestingly, infection with M. bovis has been implicated in the potential exacerbation and enhancement of respiratory disease to other pathogens since coinfections with Histophilus somnus, bovine viral diarrhea virus, Mannheimia haemolytica, bovine respiratory syncytial virus, bovine parainfluenza virus type 3 have been observed (3,4,16,25). These findings suggest an important synergism in the development of disease during the coinfection of animals involving M. bovis and other pathogens.A number of factors appear to play an important role in the virulence and development of disease during M. bovis infection, although the specific mechanisms involved in these processes are still incompletely understood. M. bovis lacks a specialized organelle for attachment, as seen in M. pneumoniae and M. genitalium (1, 6), but instead expresses variable surface proteins (Vsps) that play a critical role in its attachment (24).These membrane surface proteins undergo substantial antigenic variation involving high-frequency phenotypic switching, resulting in an increased ability of M. bovis to evade the host's immune system (13,14,21). Furthermore, M. bovis can suppress the immune system via a secreted 26-amino-acid peptide that is 84% homologous to the C-terminal end of the VspL protein (33). This peptide appears to take part in the downregulation of lymphocyte proliferation and thereby ameliorates an appropriate immune response by the host. Another mechanism of immune evasion may involve the ability of M. bovis to inhibit neutrophil oxidative burst by a mechanism that appears to involve protein kinase C signaling...

In VitroInfection of Bovine Monocytes with Mycoplasma bovis Delays Apoptosis and Suppresses Production of Gamma Interferon and Tumor Necrosis Factor Alpha but Not Interleukin-10

“…Bacterial antigen has also been observed in synovial membranes (9) and in liver and kidneys (10) of infected cattle. While M. bovis infects all subsets of bovine peripheral mononuclear cells (PBMC) and inhibits lymphocyte proliferation (11), interactions between M. bovis and a distinct PBMC population have not been characterized. Furthermore, the strategies used by M. bovis to achieve systemic dissemination have not been elucidated.…”

Effect of Mycoplasma bovis on Production of Pro-Inflammatory Cytokines by Peripheral Blood Mononuclear Cells

“…Besides bovine γδ T-cells are activated, which are also part of innate immunity. Van der Merwe et al (2010) showed persistence of M. bovis in bovine peripheral blood mononuclear cells and erythrocytes. This study was conducted to evaluate the effect of M. bovis on production of pro-inflammatory cytokines by bovine PBMCs.…”

Mycoplasma bovis in Australian feeder cattle

“…In addition, a number of studies have reported that co-infections involving M. bovis and Histophilus somni, Mannheimia haemolytica, BVDV, bovine respiratory syncytial virus (BRSV) and bovine parainfluenza virus type 3 (BPIV-3) exacerbates BRD , Gourlay et al, 1989, Perez-Casal and Prysliak, 2007. These findings suggest an important synergism in the development of disease during co-infection of animals involving M. bovis and other BRD pathogens (van der Merwe et al, 2010).…”

“…The specific mechanisms involved in these processes is still incompletely understood (van der Merwe et al, 2010). The pathogenicity of M. bovis is highly dependent on its cytoplasmic membrane, and in particular the proteins within or tethered to the outer surface of it (Adamu et al, 2013).…”

“…They comprise a large family of lipoprotein antigens located on the surface of M. bovis and have been suggested as playing a critical role in the attachment of M. bovis cells to host cells (Beier et al, 1998, Lysnyansky et al, 1999, Nussbaum et al, 2002, van der Merwe et al, 2010. Within the M. bovis PG45 type strain genome, a total of 13 single-copy vsp genes organised in a chromosomal cluster have been identified and characterised (Lysnyansky et al, 1999).…”