No abstract

The solvent evaporation method was employed to encapsulate Mycoplasma hyopneumoniae vaccine (MHV) using cellulose acetate phthalate (CAP) as an enteric coating material. Glucose was used as a diluent. The effect of some factors, such as encapsulating temperature, surfactant concentration, mechanical agitation and CAP concentration on the formation condition, particle size distribution, morphology, surface topography and antigen content of MHV microspheres, was investigated. The result indicates that the optimal operating conditions were: encapsulating temperatures, 20 degrees C; stirring speed, 400 rpm; span 80 concentration, 0.6; and 8 per cent of CAP concentration, 30 ml. The optimal condition can be used to prepare the desirable microspheres. The content uniformity of MHV microspheres was also indicated.

The aim of this study was to find a titering method that could rapidly and accurately determine the antigenic activities of Mycoplasma hyopneumoniae under specific conditions. By using the enzyme‐linked immunosorbent assay (ELISA) method, the activity of M. hyopneumoniae was found to be affected by acidic environment, temperature, and the existence of trypsins.

The in vitro stability (temperature, pH, and trypsin) of Mycoplasma hyopneumoniae antigen (MHA) with and without enteric-coated microencapsulation were examined. Microencapsulation of MHA with cellulose acetate phthalate (CAP) is an effective route to produce enteric-coated vaccine microspheres for oral administration. The effect of temperature on the rate of inactivation of MHA was studied by exposing MHA to various temperatures, such as 25, 37, 50 and 60 degrees C. The MHA microspheres were thermally more stable than that of the unencapsulated MHA. The kinetic parameters were observed to follow an Arrhenius-type temperature dependence. The MHA microspheres were also more stable in acidic regions (pH 1.2-4.0) than that of the free one. The enteric-coated MHA microspheres exhibited an excellent enteric function to prevent acidic degradation. A model similar to the well-known Michaelis-Menten equation was formulated to describe the effect of trypsin on the antigenic degradation of MHA. The equilibrium constant K(A) and the maximum reaction velocity V(m) were obtained from experimental data for both free and microencapsulated MHA. Both K(A) and V(m) values of the microencapsulated MHA were smaller than that of the free one, i.e., the resistance to proteolytic enzyme such as trypsin was enhanced by microencapsulation. The storage stability of enteric-coated MHA microspheres has been satisfactorily prolonged that they could preserve more than 90% of original antigenicity after 30 days, and over 80% of antigenicity of MHA was retained in the microspheres for 95 days when it was stored at 4 degrees C.

Cellulose acetate phthalate was used to prepare the Mycoplasma hyopneumoniae vaccine (MHV) microspheres using a solvent evaporation method. Swine serum was used as an additive in the antigen to form the core materials.The addition of serum had a significant effect on surface topography of the MHV lnicrospheres.By using this modified solvent evaporation method, the recoveries of antigens in the MHV microspheres were generally over 90% of the weight and antigenicity of antigens originally added in the formulation.