Adherence to bovine neutrophils and suppression of neutrophil chemiluminescence by Mycoplasma bovis.

The adherence of viable and heat-treated Mycoplasma bovis to bovine peripheral blood neutrophils was studied by specific immunofluorescence staining and flow cytometry. Viable and heat-treated M. bovis cells, adhered to bovine neutrophils in dose-dependent fashion within a 30 min incubation. Fluorescence quenching using crystal violet indicated that unopsonized M. bovis cells remained on the surface of bovine neutrophils without experiencing significant ingestion. The effect of M. bovis adherence on neutrophil microbicidal function was examined by measuring luminol enhanced chemiluminescence (CL). Adherent M. bovis cells did not elicit a bovine neutrophil CL response over a 75 min incubation period. M. bovis inhibited the capacity of bovine neutrophils to mount a CL response. Inhibition occurred whether viable or heat-treated M. bovis cells were used and it occurred when neutrophils were stimulated with opsonized zymosan (OZ) or phorbol myristate acetate (PMA). Inhibition of the PMA stimulated neutrophil CL response required cytadherence by M. bovis cells. These findings suggest that activation of the bovine neutrophil respiratory burst was inhibited at or distal in the pathway to the activation of protein kinase C (PKC), the site of PMA stimulation, and that it was mediated by a direct interaction between the adhering M. bovis cells and the bovine neutrophil membrane.

Pseudallescheria boydii keratomycosis in a horse.

The fungal organism Pseudallescheria boydii was isolated from the cornea of a Quarter Horse with ulcerative keratitis. Despite aggressive hourly medication through a subpalpebral lavage system, with drugs including miconazole and natamycin, the cornea developed a stromal abscess. Orbital exenteration was performed after 3 weeks. The fungal isolate was later determined to be resistant to all 8 antifungal drugs tested. Microscopic examination of the cornea revealed fungal hyphae throughout the corneal stroma and penetrating the Descemet membrane. Pseudallescheria boydii has not been implicated previously as a cause of keratomycosis in horses or in other domestic animals, although cases in human beings have been described.

Coxsackievirus B3 murine myocarditis: a pathologic spectrum of myocarditis in genetically defined inbred strains.

Group B coxsackieviruses are the most frequent causative agents in human viral myocarditis. Susceptibility to viral infections varies widely among individuals. In the mouse, coxsackievirus B3 also causes myocarditis. The differential susceptibility of different inbred strains of mice to coxsackie B3-induced myocarditis also appears to be under genetic control. This study details the histopathology of coxsackie B3 myocarditis in six different inbred strains of mice for the first 45 days after coxsackie B3 infection. These strains differ either in the haplotypes of their major histocompatibility complex or in their background genome. During the first 7 days after coxsackie B3 infection, there are dramatic differences among strains with respect to prevalence and severity of myocarditis. Focal zones of myocyte necrosis involving polymorphonuclear leukocytes as well as contraction band injury appear to be the early manifestations of direct viral injury. Four of the six strains, though, continue to show myocardial inflammation after day 9. This late phase myocarditis is characterized by the emergence of mononuclear cells within healing foci of myocyte necrosis as well as a distinctive diffuse interstitial pattern of myocarditis. The strains that develop this late ongoing myocardial inflammation frequently produce heart-specific autoantibodies. Thus the pathologic features of murine coxsackie B3 myocarditis change over the course of the illness, and genetic susceptibility to both early and late phase myocarditis differs markedly among various mouse strains.

Cardiac myosin and autoimmune myocarditis.

Infection with type 3 of the group B Coxsackieviruses (CB3) sometimes leads to the development of myocarditis in humans. Circumstantial evidence in the form of heart-reactive antibodies in these cases of human myocarditis suggests that the later phases of the disease may be due to autoimmunization. Since human myocarditis is a relatively rare sequel to infection with CB3 virus, we propose that it reflects a genetic predisposition in some individuals. To investigate this possibility we established an experimental murine model of viral myocarditis. By testing a large number of strains of inbred mice infected with CB3 we found that a few strains developed an ongoing myocarditis characterized by diffuse interstitial mononuclear infiltration and by the production of heart-specific IgG autoantibodies. These antibodies reacted with myocardial sarcolemma and myofibrils as well as with muscle striations. The principal myocardial autoantigen, identified by means of postinfectious sera of mice with heart-specific autoantibodies, was found to be the cardiac isoform of myosin. Immunization of susceptible mice with cardiac myosin stimulated the production of heart-specific antibodies reactive with both cardiac muscle striations and sarcolemma, accompanied by mononuclear infiltration of the myocardium. From these results we infer that cardiac myosin is an autoantigen capable of inducing postinfectious myocarditis in genetically predisposed individuals.

Variations in the susceptibility to Coxsackievirus B3-induced myocarditis among different strains of mice.

This study was undertaken to examine the inherent predisposition of different inbred strains of mice to develop Coxsackievirus B3-induced myocarditis. A time course study established the pertinent, differential parameters of the disease and their corresponding genetic control. The A.BY/SnJ (H-2b), A.SW/SnJ (H-2s), A.CA/SnJ (H-2f), B10.S/SgSf (H-2s), B10.PL/SgSf (H-2u), and C3H.NB/SnJ (H-2p) strains were found to vary widely in the extent and duration of viremia, in the temporal appearance and titer of neutralizing antibody, and in the prevalence, severity, and duration of myocardial disease. The A.BY/SnJ (H-2b), A.SW/SnJ (H-2s), A.CA/SnJ (H-2f), and C3H.NB/SnJ (H-2p) mice developed continuing, chronic myocardial disease, whereas B10.S/SgSf (H-2s) and B10.PL/SgSf (H-2u) did not. The four strains that displayed prolonged myocarditis also produced heart-specific myocardial autoantibodies. Heart-specific autoantibodies were not found in the B10.S/SgSf and B10.PL/SgSf animals. Differences in prevalence and titer of these heart-specific autoantibodies were noted among the three A strain H-2 congenic lines. The influence of the major histocompatibility complex (MHC) on disease production was demonstrated by comparison of the three A strain and two B10 strain H-2 congenics. Differences between A.SW/SnJ (H-2s) and B10.S/SgSf (H-2s) suggested non-MHC control of disease. These studies additionally indicate that the genetic regulation of susceptibility to CB3 infection and the direct virus-induced inflammation differ from the later immunopathic myocarditis.

Heart-specific autoantibodies following murine coxsackievirus B3 myocarditis.

The sera from A.SW/SnJ mice infected with Coxsackievirus B3 (CB3) were tested on normal mouse tissue by indirect immunofluorescence. Heart-reactive antibodies were found. Absorption studies with organ extracts showed some of these autoantibodies to be heart-specific. Additional antibodies were crossreactive with skeletal muscle and kidney. These findings suggest a role for autoimmunity in the pathogenesis of murine CB3-induced myocarditis. This study establishes an animal model for the study of the humoral autoimmune response in human viral myocarditis.