Development of an in vitro Model for the Study of the Response of Equine Tendon Fibroblasts to Injury and Medication

Equine tendon fibroblasts were isolated from explants of superficial digital flexor tendon, subcultured and maintained in monolayers. The cells were characterized by light microscopy, electron microscopy and radiolabel studies for proteoglycan production. Two predominant cell morphologies were identified. The cells dedifferentiated toward a more spindle shape with repeated subcultures. Equine tendon fibroblasts were successfully cryopreserved and subsequently subcultured. The ability to produce proteoglycan was preserved.

The isolated cells were identified as fibroblasts, based on their characteristic shape by light microscopy and ultrastructure and the active production of extracellular matrix proteins. Abundant rough endoplasmic reticulum and the production of extracellular matrix products demonstrated active protein production and export. Proteoglycans were measurable via liquid scintillation counting in both the cell-associated fraction and free in the supernatant. This model is currently being utilized to study the effects of polysulfated glycosaminoglycan on tendon healing. Future uses include studying the effects of other pharmaceuticals, such as hyaluronic acid, on tendon healing.

A model was developed for in vitro investigations into tendon healing. Fibroblasts were isolated from equine superficial digital flexor tendons and maintained in monolayer culture. The tenocytes were characterized via light and electron microscopy. Proteoglycan production was measured, using radio-label techniques. The fibroblasts were cryopreserved and subsequently subcultured. The cells maintained their capacity for proteoglycan production, following repeated subculturing and cryopreservation.

The Effect of Polysulphated Glycosaminoglycan on the Production of Proteoglycan by Equine Tendon Fibroblasts in Monolayer Culture

Equine tendon fibroblasts were isolated from tissue fragments of superficial digital flexor tendon, subcultured and maintained in monolayers. The cells were treated with two dosage regimes of polysulphated glycosaminoglycan (PSGAG). The high dose group received 0,25, 50 or 200 μg/ml of PSGAG and the low dose group received 0,0.3,1 or 2 μg/ml of PSGAG. Proteoglycan production was measured via liquid scintillation counting, following radiolabel with 35SO4 (40 μCi/ml). The counts were measured in both the cell associated fraction and the supernatant fraction.

The addition of PSGAG to the culture system did not adversely affect cell viability at any treatment level. The cells in all of treatment groups produced measurable amounts of proteoglycan in both the cell associated and supernatant fractions. There were not any differences between the treatment means in any of the four groups (high dose cell-associated, high dose supernatant, low dose cell-associated, low dose supernatant). A linear trend in proteoglycan production was not documented between treatment groups in either the cell-associated or the supernatant fractions for either of the two dosage regimes. The significance of the lack of effect is equivocal. PSGAG may influence tendon healing in a manner other than by increasing proteoglycan production.

The effect of polysulphated glycosaminoglycan on the production of proteoglycans by equine tendon fibroblasts was investigated. A previously described model was utilized to grow the tendon fibroblasts in monolayer cultures. Significant treatment effects were not seen at either a high or low dose of PSGAG. Addition of the PSGAG did not adversely affect cell viability at any treatment level.

Innate Immune Response to Intramammary Mycoplasma bovis Infection

The objective of the current study was to characterize the systemic and local innate immune response of dairy cows to IMI with Mycoplasma bovis, a pathogen of growing concern to the dairy industry. Ten Holstein cows were each infused in 1 quarter with M. bovis and studied for a 10-d period. Acute phase protein synthesis, which reflects 1 parameter of the systemic response to infection, was induced within 108 h of infection, as evidenced by increased circulating concentrations of lipopolysaccharide binding protein and serum amyloid A. Transient neutropenia was observed from 84 to 168 h postinfection, whereas a constant state of lymphopenia and thrombocytopenia was observed from 84 h until the end of the study. Milk somatic cell counts initially increased within 66 h of M. bovis infusion and remained elevated, relative to control (time 0) concentrations, for the remainder of study. Increased milk concentrations of BSA, which reflect increased permeability of the mammary epithelial-endothelial barrier, were evident within 78 h of infection and were sustained from 90 h until the end of the study. Milk concentrations of several cytokines, including IFN-gamma, IL-1beta, IL-10, IL-12, tumor growth factor-alpha, and tumor necrosis factor-alpha, were elevated in response to infection over a period of several days, whereas increases in milk IL-8 were of a more limited duration. Complement activation, reflected by increased milk concentrations of complement factor 5a, was also observed over several days. Despite the indication by these observed changes that the cows mounted a prolonged inflammatory response to M. bovis intramammary infection, all quarters remained infected throughout the study with persistently high concentrations of this bacterium. Thus, a sustained inflammatory response is not sufficient to eradicate M. bovis from the mammary gland and may reflect the ongoing struggle of the host to clear this persistent pathogen.

Destruction of Mycobacterium paratuberculosis, Salmonella spp., and Mycoplasma spp. in Raw Milk by a Commercial On-Farm High-Temperature, Short-Time Pasteurizer

The 2002 NAHM's Dairy Survey indicated that 87.2% of dairy farms in the United States feed waste milk to their neonatal calves. Although cost-effective, this practice can lead to increased calf morbidity and mortality due to ingestion of pathogenic agents. In an effort to reduce the risk of infection, dairy producers are implementing on-farm pasteurization of the waste milk as a control procedure before feeding the milk to calves. In the present study, the efficacy of a commercial high-temperature, short-time (HTST) on-farm pasteurizer unit to destroy Mycobacterium paratuberculosis, Salmonella enterica spp., and Mycoplasma spp. in raw milk was evaluated. Replicate experiments were run for 3 isolates of M. paratuberculosis, 3 serovars of Salmonella (derby, dublin, typhimurium); and 4 species of Mycoplasma (bovis, californicum, canadense, serogroup 7) at 2 different levels of experimental inoculation. In addition, HTST pasteurization experiments were performed on colostrum experimentally inoculated with M. paratuberculosis. After culture of the pasteurized milk samples, no viable M. paratuberculosis, Salmonella, or Mycoplasma were recovered, regardless of species, strain, or isolate. Pasteurization of colostrum was also effective in the destruction of M. paratuberculosis but resulted in an average 25% reduction in colostral immunoglobulin. These results suggest that HTST pasteurization is effective in generating a safer product to feed to young calves.

Detection of Mycoplasma bovis in preservative-treated field milk samples

Control of mycoplasmal mastitis requires individual cow milk sampling for culture and identification of Mycoplasma bovis. This sampling is time-consuming and expensive. Currently, some herds sample cows monthly with the dairy herd improvement (DHI) program, but a preservative is added to this milk that kills M. bovis. In this paper, a nested polymerase chain reaction (PCR) procedure that allows for rapid testing of preservative-treated milk is validated. The specificity of the nested PCR assay was confirmed by testing isolated nucleic acids of other organisms phylogenetically related to M. bovis or common to milk. A comparison against blind-passage culture on 53 field milk samples determined its sensitivity. Exposure of seeded milk samples to the procedure resulted in a sensitivity of 5.1 cfu equivalents per milliliter. Analysis of these results proved that the nested PCR assay was as sensitive as traditional culture and can be used on preservative-treated milk.

Cross-reactive proteins among eight bovine mycoplasmas detected by monoclonal antibodies

Whole cell proteins of eight bovine mycoplasmas (M. bovoculi, M. bovis, M. dispar, M. bovirhinis, M. arginini, M. verecundum, M. canadense, M. alkalescens) were separated by SDS-PAGE and transferred to nitrocellulose paper. Rabbit anti-M. bovoculi serum was found to react with immunoblots of all mycoplasma species tested. These cross-reactive proteins were in the range of 35,000-100,000 molecular weight. Monoclonal antibody MA25.5 developed against a M. bovoculi 94 kDa surface protein cross-reacted with a band of 62 kDa from M. dispar and three bands of 89, 85 and 74 kDa from M. arginini only while MA18.13 that recognized a band of 57 kDa from M. bovoculi did not react with the other species. The role of MA25.5 monoclonal antibody in inhibiting the growth of M. bovoculi, M. dispar and M. arginini was tested using the metabolic-inhibition (MI) test. Monoclonal antibody MA25.5 inhibited the growth of M. bovoculi and also inhibited M. dispar growth but at lower MI titers, while it showed no effect on the growth of M. arginini.

Use of arbitrarily primed polymerase chain reaction to investigate Mycoplasma bovis outbreaks

Colony lineages from three Mycoplasma bovis outbreaks representing different husbandry conditions in the United States were characterized with arbitrarily primed polymerase chain reaction (AP-PCR). Cases studied included a closed beef herd, a dairy calf ranch, and a feedlot. The DNA was obtained from colony lineages and used for AP-PCR with primers REP1R-I and REP2-I. Case A and C lineages were uniform by AP-PCR analysis. Lineages from case B showed heterogeneity with AP-PCR. Outbreaks A and C were therefore both infected by one source, while the ranch (case B) was infected by multiple calf shipments. The AP-PCR typing method provides genotypic epidemiological information to successfully characterize M. bovis from sequential sampling of outbreaks and different husbandry conditions.

Pasteurization of discard mycoplasma mastitic milk used to feed calves: thermal effects on various mycoplasma

Discard milk from sick or antibiotic-treated cows is often used as an economical alternative to milk replacer at dairy farms. This practice poses a health risk to calves if the discard milk is from cows with mycoplasma mastitis. Mycoplasma bovis, Mycoplasma californicum, and Mycoplasma canadense are among the agents known to cause contagious mastitis in cattle and occasionally pneumonia, otitis media, or arthritis in calves. This report describes a recent outbreak of calf polyarthritis and respiratory disease on a midwest dairy farm. The farm fed discard mycoplasma mastitic milk to its calves. On-the-farm pasteurization of the discard milk to 65 degrees C for 1 h before feeding prevented additional illness in the calves. Discard milk samples were collected before and after heating and tested for mycoplasma by culture. Only samples collected before pasteurization yielded live cultures. Common mastitic mycoplasma agents were also tested for sensitivity to heat. It was determined that 65 degrees C killed M. bovis and M. californicum after 2 min of exposure, while M. canadense remained viable for up to 10 min. Exposure to 70 degrees C inactivated M. bovis and M. californicum after 1 min, but M. canadense samples were positive for up to 3 min. Thus, M. canadense appears to be more heat resistant than M. bovis and M. californicum. Heat treatment that results in the destruction of M. canadense should be used for the pasteurization of discard mycoplasma mastitic milk.

Immunohistochemical detection of Mycoplasma gallisepticum antigens in turkey respiratory tissues

An avidin-biotin-immunoperoxidase diagnostic test was developed to facilitate rapid identification of Mycoplasma gallisepticum in respiratory tissues of turkeys. This procedure used polyclonal primary antibodies produced in rabbits. Turkeys were inoculated into the infraorbital sinus and trachea with the R strain of M. gallisepticum, Mycoplasma synoviae, Mycoplasma meleagridis, or Frey's media. The outer walls of the infraorbital sinuses, lungs, and tracheas were collected and fixed in either 10% neutral formalin or pentanedial methyl glycol at 1, 2, 3, and 4 wk postinoculation. Tissues were subdivided and remained in each fixative for 6 or 24 hr. The avidin-biotin-immunoperoxidase diagnostic test was sufficiently sensitive to detect M. gallisepticum antigen at 1, 2, 3, and 4 wk postinoculation. Staining of M. gallisepticum was significantly more intense on infraorbital sinus epithelium than on respiratory epithelium from the trachea or lung. Statistical analysis indicated that the 6-hr fixation time offered better antigen preservation than 24 hr in a fixative. There was no difference in intensity of M. gallisepticum antigen staining in tissues fixed in methyl pentanedial glycol when compared with tissues fixed in 10% neutral buffered formalin. Significant differences in staining intensity were observed between weeks. Specificity of the avidin-biotin-immunoperoxidase test was not complete. None of the tissues from the M. meleagridis and control groups showed staining. No staining was observed in the ciliated brush border of infraorbital sinus epithelial cells from turkeys infected with M. synoviae. However, weak to moderate staining was observed in several tracheas of turkeys inoculated with M. synoviae. Improved specificity of an avidin-biotin-immunoperoxidase diagnostic test to detect M. gallisepticum in respiratory tissues of turkeys probably will require the use of multiple monoclonal antibodies directed against several different epitopes specific to the cell membrane of M. gallisepticum.

Interactions of Mycoplasma bovoculi with erythrocytes: role of p94 surface protein

The attachment of two strains of Mycoplasma bovoculi to erythrocytes was measured using 35S-methionine-labelled organisms. Receptor sites of M. bovoculi involved in this attachment are trypsin-sensitive, since mild trypsin treatment of the intact organisms abolished this process completely. Pretreatment of erythrocytes with trypsin or increasing concentrations of neuraminidase resulted in no measurable effect. Monoclonal antibody MA25.5 directed against a M. bovoculi surface antigen of 94 kDa termed p94 blocked 40% of the attachment, while MA18.13 directed against a 57 kDa protein band of M. bovoculi had no effect on the attachment process. Other properties of M. bovoculi were tested using six strains of the mycoplasma and erythrocytes from several animal species. None of the strains showed haemagglutinating or haemadsorbing activities.

Differential serologic response to Mycoplasma ovipneumoniae and Mycoplasma arginini in lambs affected with chronic respiratory disease

An enzyme-linked immunoabsorbent assay (ELISA) was used to evaluate the levels of antibodies to Mycoplasma ovipneumoniae and M. arginini in lambs with chronic respiratory disease. Sera were obtained from lambs in several flocks at various stages of the clinical disease and tested with sodium dodecyl sulfate (SDS)-treated M. ovipneumoniae and M. arginini whole cells and a crude capsular extract of M. ovipneumoniae as the antigens. There were low levels of antibody to M. ovipneumoniae in flocks sampled at the early stages of infection, whereas increased levels of antibody were present in lambs from flocks that had apparently recovered from the clinical disease. Slowly rising titers of circulating antibodies to M. ovipneumoniae were confirmed by sequential bleeding of lambs during the course of the clinical disease. However, antibody levels of M. arginini were more likely to increase earlier in the disease process. There was significant cross-reactivity between the 2 SDS-treated antigens in both the ELISA test and western immunoblotting. In contrast, the crude capsular extract was specific for detecting antibodies to M. ovipneumoniae.

Identification and localization of a 94 kDa membrane protein found in Mycoplasma bovoculi strains

Six isolates of Mycoplasma bovoculi obtained from cattle herds with bovine keratoconjunctivitis were analyzed by gel electrophoresis and immunoblotting techniques. All six strains showed similarity in their protein profiles although no two patterns were identical. Antigenic differences between strains were detected in immunoblots reacted with post-exposure calf serum. A common 94 kDa protein band designated p94 was detected in all six strains reacted with monoclonal antibody MA25.5 developed to one of the strains. The p94 was also recognized in these strains by the calf serum. Trypsin treatment of intact mycoplasma cells resulted in the removal of p94 from immunoblots reacted with MA or hyperimmune rabbit serum. Other trypsin-resistant antigens shared between strains or being strain-specific in nature were identified when trypsin-treated mycoplasma cells were reacted with hyperimmune rabbit serum. The p94 antigen was shown to be of mycoplasmal origin by radio-immunoprecipitation using the MA or hyperimmune rabbit serum. These studies identify the presence of a surface antigen (p94) on M. bovoculi membrane in all strains examined that is trypsin sensitive by the use of monoclonal antibody, calf serum and hyperimmune rabbit serum.

Occurrence of autoantibodies to cilia in lambs with a 'coughing syndrome'

A respiratory disease of lambs that has been termed the 'coughing syndrome' has been observed in the mid-western region of the United States of America. Mycoplasma ovipneumoniae (M. ovipneumoniae) and Mycoplasma arginini (M. arginini) were routinely isolated from the respiratory tract of lambs with this disease. A high level of antibodies reactive with ovine cilia of the upper respiratory tract was detected in the sera from many of the lambs in affected flocks but not in sera of lambs from unaffected flocks. The reactivity of these antibodies with cilia was demonstrated by ELISA and confirmed by indirect immunofluorescent staining and western immunoblotting. These antibodies were predominantly of the IgG isotype. They were distinct from cold or warm agglutinins and could be absorbed from the sera with cilia but not with antigens of common bacterial pathogens of the sheep respiratory tract including M. ovipneumoniae, M. arginini, Pasteurella haemolytica, Pasteurella multocida or Neisseria ovis. In addition, their occurrence appeared to be independent of the specific antibodies to M. ovipneumoniae and M. arginini. Western immunoblotting indicated that the antibodies were directed primarily against an antigen with apparent molecular weight of 50 kDa. In one flock from which serial serum samples were collected from the same lambs over a 10-month period, antibodies to ovine cilia developed before the onset of the clinical disease and persisted for a period of several months until most of the lambs had apparently recovered. However, colonization of the respiratory tract of the lambs by M. ovipneumoniae preceded the production of these antibodies. Sequential serum samples taken from another flock, with no known history of this coughing, showed no such antibodies throughout the sampling period. It is suggested that an immunopathologic mechanism involving production of autoantibodies directed against a ciliary antigen of the lambs could be a contributing factor to the pathogenesis of this clinical disease.

Demonstration of a capsule on Mycoplasma ovipneumoniae

OBJECTIVE

To examine Mycoplasma ovipneumoniae for presence of a capsule and its potential role in adherence.

SAMPLE POPULATION

17 isolates of M ovipneumoniae and 2 isolates of M arginini, recovered from sheep with respiratory tract disease.

PROCEDURE

Mycoplasmas were cultured in modified Fills broth medium, ovine fetal lung cells, or ovine tracheal ring explants. Pelleted mycoplasmas or ring cultures infected with mycoplasmas were treated with ruthenium red or polycationic ferritin and visualized by transmission electron microscopy. Reactivity of several lectins with the mycoplasmas was studied by use of a microtitration plate agglutination test.

RESULTS

Electron microscopy revealed a large number of M ovipneumoniae cells covered with an electron dense-stained amorphous material suggesting that it was a capsule. Multiple passages of the microorganisms in modified Friis broth medium decreased thickness of the capsule, but not percentage of cells encapsulated. Marked differences were observed when M ovipeumoniae isolates grown in modified Friis broth medium or co-cultured with ovine fetal lung cells were compared for capsular thickness or percentage of encapsulation. In thin sections of ruthenium red-stained tracheal ring cultures, the mycoplasmas appeared to be in close contact with cilia through their capsule. All isolates of M ovipneumoniae reacted strongly with wheat germ agglutinin lectin.

CONCLUSIONS

Mycoplasma ovipneumoniae produces a polysaccharide capsule with variable thickness that is dependent on culture conditions and strain. Morphologic observations suggest that this capsule facilitates adherence of the organism to ciliated epithelium.

Field isolates of Mycoplasma ovipneumoniae exhibit distinct cytopathic effects in ovine tracheal organ cultures

Ovine tracheal ring explants were infected with four different Mycoplasma ovipneumoniae and one M. arginini field isolate and their ability to induce cytopathic effects was tested by measuring ciliary activity and intracellular calmodulin release. Infected tracheal rings showed significantly decreased ciliary activity as compared to the non-infected control rings. There were, however, marked differences between isolates in the onset and severity of the effects which correlated with their ability to produce hydrogen peroxide. Infected tracheal rings released more calmodulin than the non-infected controls. The amount of calmodulin released also varied between isolates, and somewhat reflected the degree of loss of ciliary activity in the corresponding rings induced by the different isolates. Light and electron microscopic examinations of infected tracheal rings revealed disorganisation and sloughing of the epithelium, and association of mycoplasmas only with the cilia. Following repeated in vitro passages, the organisms had reduced ability to inhibit ciliary activity which correlated with decreased hydrogen peroxide production. Addition of catalase to the organ cultures delayed loss of ciliary activity. These results suggest that M. ovipneumoniae induced ciliostasis in ovine tracheal ring explants which correlated with hydrogen peroxide production. Furthermore, these M. ovipneumoniae-induced injuries to respiratory epithelial cells could contribute to the role that this organism may play in sheep respiratory disease.

Expression of functions by normal sheep alveolar macrophages and their alteration by interaction with Mycoplasma ovipneumoniae

Normal sheep alveolar macrophages collected by bronchial lavage were exposed to live or heat-killed Mycoplasma ovipneumoniae organisms, and their capability to ingest Staphylococcus aureus and to elicit antibody-dependent cellular cytotoxicity against sensitized chicken red blood cells was tested. Controls consisted of non-infected macrophages in M199 medium. In addition, the effect of M. ovipneumoniae on expression of surface molecules on these sheep alveolar macrophages was determined. The percentage of S. aureus ingested by nontreated sheep alveolar macrophages was significantly higher than that of infected macrophages. Live mycoplasmas were more effective in suppressing the ingestion of S. aureus by these macrophages than killed mycoplasmas. Both live and killed mycoplasmas suppressed the cytolytic effect of the sheep alveolar macrophages to a similar degree. About 78% and 45% of the normal sheep alveolar macrophages had IgG and complement receptors, respectively. Infection of these macrophages with M. ovipneumoniae decreased significantly the expression of IgG receptors but had no effects on complement receptors. There were substantial increases in the expression of both MHC class I and class II by the mycoplasma-induced macrophages as compared with unstimulated macrophages. Live mycoplasmas were more effective in inducing expression of both classes than killed mycoplasmas. The results, taken together, suggest that M. ovipneumoniae induced alterations in macrophage activities and this may be a contributing factor in the pathogenesis of respiratory disease induced by the organism.

Mycoplasma bovis-associated pneumonia and arthritis complicated with pyogranulomatous tenosynovitis in calves

Immunohistochemistry and bacteriologic culturing were used to detect Mycoplasma bovis in tissue specimens from feedlot calves affected with pneumonia and arthritis. Two herds with 110 Charolais calves and 25 Angus calves were examined. Clinical signs included severe respiratory distress, anorexia, pyrexia, and lameness, which affected nearly a third of the calves. Lung lesions were characterized by numerous abscesses. Synovial lesions of the limbs included pyogranulomatous tenosynovitis, bursitis, and synovitis, particularly in the areas of the carpal and elbow joints. Abscesses in lung and synovial tissues contained accumulations of M bovis antigens, as revealed by immunohistochemistry. The findings of this report indicate that infection with M bovis may result in a pneumonia-arthritis syndrome with pyogranulomatous lesions in calves.

Membrane-associated and cytosolic species-specific antigens of Mycoplasma bovis recognized by monoclonal antibodies

Mycoplasma bovis is a causative agent of bovine mastitis, arthritis, and pneumonia. Six monoclonal antibodies (MAbs) against M. bovis were prepared and used to characterize specific antigens of the mycoplasma. Reactivity of the MAbs to six M. bovis strains was tested by IFA, ELISA, and immunoblotting. The specificity of these MAbs was tested by the same methods against 8 other species of bovine mycoplasmas and 1 mycoplasma species of sheep and goats (Mycoplasma agalactiae) that is highly cross-reactive with M. bovis. Three of the MAbs were used on Western blots of trypsin-treated whole organisms to determine if the antigens were exposed on the surface of M. bovis By isotyping, MAbs were identified as kappa chain IgG1 (3 MAbs), and IgM (3MAbs). The MAbs reacted with all six M. bovis strains in IFA, ELISA, and Western blots. Four of the antigens recognized were highly specific for M. bovis in ELISA, and 3 were cross-reactive with M. agalactiae or other bovine mycoplasmas in Western blots. One MAb reacted with multiple bands with all M. bovis strains, indicating recognition of a size-variant antigen. The size-variant antigen and one of the M. bovis-specific antigens were recognized as surface proteins. A large M. bovis-specific antigen was a conserved cytosolic protein. The M. bovis antigens discovered may be used for specific detection of the organism or measurement of antibody responses, particularly if used in tests with nondenatured alkali-treated antigen, such as ELISA.

Immune responses to the capsular polysaccharide of Mycoplasma dispar in calves and mice

Humoral and cell-mediated immune responses to the capsular polysaccharide (CPS) of M. dispar and polygalacturonic acid (pGaIU--a structurally similar polysaccharide) were investigated in calves experimentally infected with Mycoplasma dispar and in mice immunized with CPS or pGaIU. Sera, tracheobronchial lavage and nasal fluids, collected before and after infection in calves, were checked for the presence of anti-CPS and anti-pGaIU antibodies. The sera from mice injected with CPS or pGaIU were checked for different classes of anti-CPS and anti-pGaIU antibodies. Peripheral blood lymphocytes from calves and splenic lymphocytes from mice were monitored for specific proliferative responses to CPS and pGaIU. At about 2 weeks post-infection, anti-CPS IgM response in serum, anti-CPS and anti-pGaIU IgM and IgA response in lavage fluid and lymphocyte proliferative response was seen in the calves. Mice immunized with CPS and pGaIU gave exclusively IgM responses. No secondary response was seen in mice immunized with CPS in contrast to mice immunized with pGaIU. Antibodies cross-reactive with pGaIU were present in the sera of CPS-immunized mice but antibodies cross-reactive with CPS were not found in pGaIU-immunized mice. No significant blastogenic response was shown by mouse splenocytes to CPS or pGaIU.

Immunohistochemical and pathological study of Mycoplasma bovis-associated lung abscesses in calves

Out of 45 cases of fatal chronic pneumonia in calves examined for Mycoplasma bovis infection from February to July 1994, 11 cases with pulmonary abscesses that were culture positive for M. bovis were encountered. The cases were studied in detail using a recently developed monoclonal antibody-based immunoperoxidase technique. Mycoplasma bovis organisms were detected in specific locations at all stages of abscessation observed. In bronchioles or terminal airways within which abscesses developed, M. bovis was located at the epithelial surface and in close association with infiltrating neutrophils and macrophages. Abscessed airways that had lost the epithelium were encapsulated and were seen as coagulative necrotic foci that stained intensely for M. bovis, especially at the periphery. Some foci stained weakly and such might have been resolving lesions. Mycoplasma bovis was also demonstrated at sites of mild mononuclear cell infiltration in the livers and kidneys of 2 calves. The mycoplasma was detected within bile ducts in the liver and in the tubular epithelium of the kidney. Abscesses not staining for M. bovis, presumably caused by other pathogens, were seen concurrently with M. bovis-associated abscesses in some lungs. Thirteen other M. bovis-positive cases showed no abscesses, possibly indicating heterogeneity among M. bovis strains. Three other cases with abscesses were negative for M. bovis by culture and immunoperoxidase staining. The monoclonal antibody-based immunohistochemical technique is efficient for specific detection of M. bovis in cases of enzootic pneumonia of calves with or without abscessation. Mycoplasma bovis is implicated in the pathogenesis of lung abscesses in some calves.

Impaired tracheobronchial clearance of bacteria in calves infected with Mycoplasma dispar

Infection of tracheal organ cultures with Mycoplasma dispar results in degeneration of respiratory epithelial cells with loss of ciliary activity. To assess the effect of these changes on the clearance of bacteria from the respiratory tract, the tracheobronchial clearance of a suspension of Serratia marcescens was determined in calves before and after infection with M. dispar. Tracheobronchial samples were obtained at various times after deposition of the marker bacteria. Clearance of S. marcescens was significant by 3 h after inoculation and only few colonies were detected 4 h after challenge. By contrast, in the same animals 5 days after intratracheal exposure to M. dispar, clearance of S. marcescens did not decrease significantly 4 h after inoculation. Histopathological and scanning electron microscopy (SEM) studies of infected lungs revealed that, as a result of infection with M. dispar, areas of degeneration and destruction of the respiratory ciliated epithelium occur in intermediate and small airways. These lesions may be responsible for the altered clearance observed in these mycoplasma-exposed calves.

Mycoplasma bovoculi--augmented bovine natural killer activity

The effect of conjunctival Mycoplasma bovoculi infection on local and systemic natural killer activity was studied in cattle. A standard in vitro assay against the mouse tumor cell line, YAC-1, was used to measure increases in effector cell activity. Local responses in the eye were investigated by examination of stained exfoliative conjunctival cells and tissue biopsies. An increase in systemic cytolytic activity was seen in infected calves, and maximal values were observed on the second day post infection (DPI). An elevation in the number of large granular lymphocytes was noted in the conjunctival samples, and maximal numbers were again observed at 2 days post infection. It is proposed that natural killer cell activity may play a role in the initial host responses of cattle to M. bovoculi infection.

Interaction of Mycoplasma dispar with bovine alveolar macrophages

The capacity to avoid phagocytosis and the activation of bovine alveolar macrophages (BAM) by encapsulated Mycoplasma dispar or purified M. dispar capsule was investigated. Encapsulated and unencapsulated M. dispar were cocultured with BAM in the presence or absence of antisera prepared against unencapsulated M. dispar or purified capsule antiserum. Unopsonized mycoplasmas resisted phagocytosis, while only anti-capsule antibodies enhanced the phagocytosis of encapsulated mycoplasmas. BAM were cultured in the presence of purified M. dispar capsule or either live or heat-killed encapsulated or unencapsulated M. dispar. These BAM were then activated with Escherichia coli endotoxin or left without further activation. The supernatants of these cultures were assayed for tumor necrosis factor, interleukin 1, and glucose consumption as indicators of macrophage activation. Tumor necrosis factor and interleukin 1 were produced by BAM stimulated with unencapsulated M. dispar but not when encapsulated M. dispar or its purified capsule was used. Similarly, glucose consumption was increased in the presence of unencapsulated M. dispar, but not when BAM were cocultured with encapsulated M. dispar or purified capsule. When BAM were treated with purified capsule or encapsulated mycoplasmas, they could not be subsequently activated by endotoxin. These results indicate that encapsulated M. dispar or purified capsule exerts an inhibitory effect on the activity of BAM and prevents the activation of these cells.

Capsulelike surface material of Mycoplasma dispar induced by in vitro growth in culture with bovine cells is antigenically related to similar structures expressed in vivo

Electron microscopy has been used to show that Mycoplasma dispar produces an external capsulelike material in vivo that has an affinity for both ruthenium red and polycationic ferritin. This extracellular material is lost upon passage in culture medium but can be regained with a single passage on bovine lung fibroblast (BLF) cells. To confirm that the extracellular material associated with cell-grown mycoplasmas was the same as that observed in infected calves, rabbit antibodies were produced to purified capsulelike material isolated by protease digestion of cell-grown organisms. These antibodies bound to capsulelike material on the surface of M. dispar cells colonizing the bronchial epithelium of infected calves and to capsulelike material from cell-grown mycoplasmas. Calves infected with M. dispar produced antibodies in lung secretions that were capable of binding to the purified capsulelike material. The Fab fragments of rabbit antibodies to in vitro-produced capsulelike material could block this binding, indicating that the capsulelike material was similar in both in vivo-grown and cell-grown organisms. The carbohydrate nature of the capsular material suggested by the ruthenium red and polycationic staining characteristics was confirmed by its binding to Ricinus communis agglutinin, a galactose-specific lectin. These studies confirm that capsule material produced during infections with M. dispar share antigenic determinants with the material produced under in vitro conditions and that association with mammalian cells induces production of this material.

Adherence of Mycoplasma hyopneumoniae to cell monolayers

This work was an attempt to develop an in vitro adherence model for Mycoplasma hyopneumoniae, using monolayers of human and porcine lung fibroblasts and porcine kidney cells. Mycoplasma hyopneumoniae grown in Friis mycoplasma broth was radiolabeled with 35[S]-methionine, washed, concentrated, and inoculated on the monolayers. After 15 minutes of centrifugation to facilitate adherence, monolayers were washed 3 times, dissolved with 0.1N NaOH, and suspended in scintillation liquid, and the radioactivity was determined in a liquid scintillation counter. Adherence, measured as a percentage of counts added, varied according to the mycoplasma strain and the cell line used. Comparison of strains J, 144L, and 232 of M hyopneumoniae revealed 7.5 +/- 5.9, 31.9 +/- 13, and 9.6 +/- 5% adherence to porcine kidney cells, respectively. Slightly different, but proportionally the same relationships were obtained with swine or human fibroblasts. Adherence was decreased slightly by repeated washings of the mycoplasma-treated cell monolayers; however, a plateau was reached, indicating irreversibility of the adherence process. Pretreatment of cell monolayers with nonlabeled organisms substantially blocked adherence by labeled organisms. Dilution of labeled organisms resulted in an increased proportion adhering. Therefore, it appears that the adherence was a receptor-dependent event. Treatment of the mycoplasmas with trypsin prior to the inoculation of monolayers resulted in a marked reduction in adherence. Treatment of the mycoplasmas with hyperimmune swine serum against M hyopneumoniae or normal swine serum resulted in 80 to 90% reduction of adherence; however, no inhibition occurred when mycoplasmas were treated with purified IgG from the hyperimmune serum.

Effect of host cell on the in vitro characteristics expressed by two bovine viral diarrhea virus strains

Growth curves, immunofluorescence assays and radioimmunoprecipitation analysis of bovine viral diarrhea virus (BVDV)-specified polypeptides were used to determine the susceptibility of bovine endothelial cells (BECs) to infection with strains of BVDV. One strain of the virus, NY1, normally non-cytopathic when grown in bovine turbinate cells (BTUs), did not parallel this type behavior in BECs. Virus replication kinetics, morphological changes in infected cells and resolution of viral polypeptides suggest that NY1 replicated and showed cytopathologic changes in infected BECs similar to a cytopathic strain of BVDV, strain C24V. Two previously unreported viral polypeptides were identified in NY1-infected endothelial cells. These polypeptides had molecular weights of 92,000 (92kDa) and 72kDa. These findings suggest that BVDV-cell interactions occurring in BECs differ from those observed in similarly infected BTUs.

Comparative characterization of the leukocidic and hemolytic activity of Moraxella bovis

The cytotoxic effect of Moraxella bovis 118F on bovine neutrophils was evaluated and characterized by use of a 51Cr release assay. Neutrophils harvested from healthy adult cattle were labeled with 51Cr. The leukocidic activity produced by M bovis 118F, a hemolytic strain of M bovis, was heat-labile. A live culture of strain 118F, at a ratio of 100 bacteria/neutrophil, released 97.7% of the 51Cr from labeled neutrophils. Neither a heat-killed preparation of M bovis 118F nor a live or heat-killed preparation of M bovis IBH63 (a nonhemolytic and nonpathogenic strain) induced significant (P greater than 0.05) release of 51Cr. Moraxella bovis 118F broth culture filtrates prepared for evaluation of leukocidic activity also were evaluated for hemolytic activity. These 2 toxic activities had several characteristics in common. Both were filterable, heat-labile, produced by a hemolytic strain, and were released during early logarithmic phase growth from broth cultures. Leukocidic and hemolytic activities were protected from degradation by phenylmethyl sulfonyl fluoride, a serine protease inhibitor. Leukocidic and hemolytic activities were dependent on calcium ions. Filtrate resulted in 54.1% 51Cr release from labeled neutrophils and contained 646.7 hemolytic U/ml, respectively, when saline (0.85% NaCl) + 10 mM CaCl2 solution was used as diluent. Neither saline solution nor saline + 10 mM MgCl2 solution supported leukocidic or hemolytic activity. Serum, obtained from several calves 10 to 38 days after M bovis inoculation, substantially neutralized leukocidic and hemolytic activities, compared with paired preinoculation serum samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological reactivity of Moraxella bovis lipopolysaccharide

Lipopolysaccharide (LPS) was isolated from Moraxella bovis 118F and ATCC 10900, M ovis ATCC 33078, and M phenylpyruvica ATCC 23333 by hot phenol-water extraction. In silver-stained sodium dodecyl sulfate polyacrylamide electrophoresis gels, M bovis 118F LPS had a smooth profile, whereas the other Moraxella preparations appeared to be rough. The LPS preparations induced pyrogenicity and dermal Shwartzman reactions in rabbits, and induced production of tumor necrosis factor and interleukin-1 in vitro. Induction of tumor necrosis factor appeared to be among the most potent biological activities of M bovis LPS.

Infectious bovine keratoconjunctivitis epizootic associated with area-wide emergence of a new Moraxella bovis pilus type

Pilus-mediated adherence is a virulence attribute of Moraxella bovis. Several pilus types have been shown to exist among strains of this bacterium, but correlation between pilus type and specific field cases of the disease has not been done. During the summer of 1987, an epizootic of infectious bovine keratoconjunctivitis was reported in 7 Iowa counties. Eight isolates of M bovis were secured from 12 episodes studied. All 8 of the isolates were nearly homogeneous in biochemical properties and had the same plasmid biotype. Pilus typing performed by immunofluorescence and immunogold electron microscopy identified a single new pilus type among 5 of the 8 isolates. This pilus type was identified in field cases that developed within a narrow time frame and over large distances. The implication of these findings is that infectious bovine keratoconjunctivitis epizootics may be associated with emergence of a novel pilus type, and that rapid dissemination over wide distances can occur, presumably by transportation of carrier cattle.

Attachment of Mycoplasma bovoculi to bovine conjunctival epithelium and lung fibroblasts

A specialized tip structure in some mycoplasmas facilitates their attachment to host cells. Mycoplasma bovoculi strains FS8-7 and M165/69 did not have specialized membrane structure and did not exhibit capsule when stained with ruthenium red and examined by use of transmission electron microscopy. The organisms attached in vitro to bovine lung fibroblasts, with no apparent specialized structure. Attachment to conjunctival epithelium in vivo was observed (after death) in a calf infected with M bovoculi. Close association between M bovoculi and the host cells was noticed. Mycoplasmal cells pretreated with hyperimmune rabbit serum and labeled with protein A-gold complex had gold particles randomly distributed around the membrane. Gold-labeled monoclonal antibodies, M25.5 and M7.3, which were directed against 2 surface antigens of M bovoculi, also were distributed randomly on the mycoplasmal surface as seen in results of double-labeling experiments.

Immune responses in Mycoplasma bovoculi conjunctivitis

Calves infected with Mycoplasma bovoculi respond with conjunctivitis, extensive colonization of cell-adherent mycoplasmas, and a transient influx of neutrophils to ocular surfaces. Antibody responses can be detected in the circulation and in lacrimal fluid by enzyme-linked immunosorbent assay (ELISA). Serum responses were primarily IgM and IgG and included complement-independent metabolic inhibition activity, while lacrimal fluid responses were primarily IgA and did not exhibit metabolic inhibiting activity. Cell-mediated immune responses also followed the initial infection. In all cases, these immune responses were concurrent with persistent colonization of ocular surfaces. Clearance of persistent infections was observed after variable periods of time and was followed by resistance to challenge. Parenteral presentation of antigen gave similar systemic responses with no lacrimal responses. Animals given antigen parenterally exhibited inflammatory responses and persistent colonization after challenge. These reactions were more intense than those following infections in unstimulated cattle.

Vaccination of cattle with Mycoplasma bovoculi antigens: evidence for field immunity

Cattle previously exposed to Mycoplasma bovoculi developed a high serum IgG and cellular responses detected by ELISA and lymphocyte blastogenesis respectively, when immunized with three M. bovoculi antigen preparations (two non-ionic detergent extracts and a killed whole organism). Similar responses to the detergent immunogen were observed in colostrum-deprived calves free of M. bovoculi. Following ocular challenge with live M. bovoculi all animals including the control group cleared the organism. However the organism colonized the eyes of the colostrum-deprived calves. These observations indicate that previous exposure to M. bovoculi confers immunity to reinfection and that none of the vaccines provided a protective activity against the organism.

Outer membrane protein antigens of Moraxella bovis

Outer membranes were isolated from bovine isolates and type strains of Moraxella bovis, M phenylpyruvica, M lacunata, and M ovis by sodium N lauroyl sarcosinate extraction and differential centrifugation. Analysis of outer membranes from these organisms by sodium dodecyl sulfate-polyacrylamide-gel electrophoresis revealed that all M bovis isolates shared a common polypeptide pattern that was readily distinguishable from other Moraxella spp. Nine major outer membrane protein bands were identified by sodium dodecyl sulfate-polyacrylamide-gel electrophoresis analysis of M bovis. Immunoblotting of protein antigens of M bovis revealed several outer membrane proteins that seemed to be common antigens of all M bovis isolates.

Mycoplasma bovoculi infection increases ocular colonization by Moraxella ovis in calves

To determine whether infection with Mycoplasma bovoculi increases ocular colonization of cattle eyes with Moraxella bovis and other bacteria, colonization of ocular gram-negative bacteria were measured in eyes of cattle infected with Mycoplasma bovoculi. Strains of Moraxella ovis were chosen because these are among the most commonly isolated species of gram-negative bacteria from cattle eyes. Five strains of M ovis were characterized biochemically and by pilus structure, permitting the recognition of 2 biotypes. All strains were tested in a mouse corneal pathogenicity model. One strain of each biotype was selected for testing in calves. All 5 strains were apathogenic for mice, and the 2 strains tested in cattle did not induce keratitis. Infection of calves with Mycoplasma bovoculi increased the amount and persistence of colonization with the strains of M ovis.

Antibody response in calves experimentally or naturally exposed to Mycoplasma bovoculi

An antiglobulin-ELISA has been developed to detect antibody activity to Mycoplasma bovoculi in sera, nasal fluids and lacrimal fluids of field and experimentally exposed calves. Low IgG activity with no IgM or IgA was detected in sera of experimental calves. In nasal and lacrimal fluids, IgA appeared as early as the first week following exposure to M. bovoculi and predominated in both of these fluids throughout the 9 wk observation period. Sera from field-exposed animals showed high IgG and IgM activities. The metabolic-inhibition (MI) test was applied to detect growth inhibition of M. bovoculi in those fluids. This property was found only in sera of exposed animals and thus could be used to test for M. bovoculi infection. The ELISA test and the MI test were considered reliable tests for the detection of antibodies to M. bovoculi infection. The implications of finding no growth-inhibiting activity in nasal and lacrimal fluids concurrent with a high IgA activity are discussed.

Immunogenicity of Moraxella bovis hemolysin

Anti-Moraxella bovis hemolysin activity was observed in 35 cattle exposed to field infections of infectious bovine keratoconjunctivitis (IBK). All cattle in infected herds seroconverted with respect to antihemolysin whether or not clinical IBK was noted. Cattle previously exposed to IBK possessed higher antihemolysin titers than did younger, nonexposed cattle. Antihemolysin activity was noted in bovine sera up to 7 years after exposure to IBK. Sera from experimentally infected calves were found to possess antihemolytic activity against all 33 strains of M bovis tested. Antihemolytic activity could be demonstrated in random-bred mice inoculated with whole doxycycline-treated M bovis, frozen or lyophilized whole M bovis, and membrane fractions treated with sodium lauryl sarcosinate, Triton X 100, and Triton X 100 + EDTA, but not with formalin-treated whole M bovis.

Moraxella bovis hemolysin

Moraxella bovis hemolysin was readily filterable through polycarbonate membrane filters, but not through nitrocellulose filters. The hemolysin was filterable through polycarbonate filters with pore diameters of greater than or equal to 0.015 micron (APD). Of the hemolytic activity of cell-free filtrates, 74% could be pelleted by ultracentrifugation at 100,000 X g for 2 1/2 hours. Hemolytic activity could be demonstrated in preparations of outer membrane fragments isolated from log-phase cultures. Hemolysin in M bovis broth cultures reached a maximum concentration in late logarithmic phase (4.5 hours after inoculation) and declined thereafter. Hemolysin was inactivated by heat, trypsin, formalin, and lyophilization.

In vitro adherence of Moraxella bovis to intact corneal epithelium

An in vitro assay is described using radiolabeled Moraxella bovis for studying adherence to intact bovine corneal epithelial surfaces. The assay was optimized for time (45 min) and for the ratio of epithelial cells to bacteria (1:1000) that demonstrated a significant difference in adherence between M. bovis strain 118F, a piliated organism and a nonpiliated variant, strain 118F/4-2. Adherence of these organisms correlated with previous pathogenicity studies involving experimental infection of calves. Scanning electron microscopy of tissues treated in the assay revealed a predilection of M. bovis for dark epithelial cells and for association with depressions in the tissue surface. This assay technique is discussed in comparison with other in vitro adherence assay methods.

Reaction of convalescent bovine antisera with strain-specific antigens of parapoxviruses

Two strains of papular stomatitis (PS) virus, 1 of milker's nodules (MN) virus and 1 of contagious ecthyma (CE) virus possessed 2 distinct external structures when examined by electron microscopy. The innermost, designated coat was closely apposed to the tubular surface, whereas the outer envelope loosely surrounded the virion. When convalescent sera from cattle infected with PS virus were used for immunoelectron microscopy, antibody reacted with coats and envelopes of the PS virus strains, but only with coats of MN and CE viruses. Convalescent sera from cattle infected with PS or MN virus contained complement-dependent antibodies cytolytic to cells infected with the homologous virus. In an indirect immunofluorescence test, the sera reacted with homologous strains to higher titers than with heterologous strains.

Comparisons between two isolates of stomatitis papulosa virus

The cytopathology and length of latency in single-step growth curves of two isolates of stomatitis papulosa virus are compared in this report. Isolate 721 was obtained from a calf with oral ulcers and isolate 8665 was obtained from a calf with respiratory disease and oral ulcers. In single-step growth curves, the latency period of isolate 721 was 8 h while that of isolate 8665 was 6 h. The cytopathic effect produced by isolate 721 in bovine lung cells was characterized by enlargement of the cell, cell-to-cell adherence and large intracytoplasmic accumulations of viral inclusion material. Isolate 8665 caused rapid cell degeneration and detachment, with small accumulation of viral inclusion material. Neither of the two strains grew in bovine alveolar macrophage cultures or in the respiratory epithelium of fetal bovine tracheal explants. Intragingival inoculation of these isolates in cattle resulted in oral lesions without clinical signs of respiratory of systemic involvement. Virus was recovered from the oral lesions and from nasal secretions for as long as 10 days. Inoculation of dexamethasone-treated cattle resulted in a similar clinical condition although virus was recovered for 20 days from oral lesions and nasal secretions. Seroconversions from negative to 1 : 2560 were detected in inoculated cattle by indirect immunofluorescence.

Bovine mycoplasmal conjunctivitis: experimental reproduction and characterization of the disease

Epizootic conjunctivitis was studied in eight Iowa cattle herds. Mycoplasma bovoculi was isolated from the eyes of cattle in all affected herds and Ureaplasma sp. was isolated from the eyes of cattle in 3 of the herds. When either of these two organisms was experimentally inoculated into the conjunctival sac of healthy calves, conjunctivitis became apparent within 3 to 4 days after infection and persisted for more than 1 month. Calves inoculated with M. bovoculi responded with mild localized conjunctivitis and with serous lacrimation while calves inoculated with Ureaplasma sp. had diffuse conjunctivitis with watery lacrimation. With both microorganisms, the symptoms varied in intensity with peaks of recrudescence through the observation period. The microorganisms were recovered for periods of 1 to 2 months from the conjunctival mucosae of cattle undergoing natural or experimental infections.