The efficacy of oral vaccination of mice with alginate encapsulated outer membrane proteins of Pasteurella haemolytica and One-Shot.

The goal of this study was to examine the efficacy of oral delivery of alginate encapsulated outer membrane proteins (OMP) of Pasteurella haemolytica and a commercial One-Shot vaccine in inducing protection in mice against lethal challenge with virulent P. haemolytica. We examined two alginate microsphere formulations and compared them with oral unencapsulated and subcutaneously administered vaccines. Alginate microspheres were made by the emulsion-cross-linking technique. They were examined for size, hydrophobicity, and antigen loading efficiency before they were used in the study. Mice were vaccinated by administering 200 microg of antigens in 200 microl of microspheres suspension orally or subcutaneously. One group of mice received blank microspheres and a second group was given unencapsulated antigen orally. A third and a fourth group received different formulations of alginate encapsulated antigens by oral administration. Three groups received subcutaneous inoculations (alginate encapsulated, non-adjuvanted and unencapsulated antigens, and adjuvanted One-Shot), and one group received water (naïve group). Mice were vaccinated orally for four consecutive days and challenged with P. haemolytica 5 weeks after the first vaccination. Weekly serum and feces samples were assayed for antigen specific antibodies. The number of dead mice in each group 4 days post challenge was used to compare the efficacy of the various vaccination groups. The mean volume sizes of blank alginate microsphere formulations A, and AA were 15.9, 16 and 9.2 microm, respectively. Hydrophobicity of the microspheres was evaluated by measuring contact angle on a glass slide coated with the microspheres. The contact angles on A and AA were 37.8 and 74.3 degrees, respectively. Antigen concentration in a 1:1 w/w suspension of microspheres in water was 0.9 mg/ml. Rate of death for the blank group was 42.8% whereas for groups vaccinated with antigens encapsulated in A and AA the death rates were 40 and 33.33%, respectively. The death rate in mice vaccinated with unencapsulated antigens was 55.6%. Groups vaccinated by subcutaneous inoculation showed the lowest death rate. These results show that encapsulating OMP and One-Shot in alginate microspheres improves their performance as an oral vaccine.

Swelling of hydroxypropyl methylcellulose matrix tablets. 2. Mechanistic study of the influence of formulation variables on matrix performance and drug release.

We characterized the effect of hydroxypropyl methylcellulose (HPMC)/lactose ratio and HPMC viscosity grade (molecular weight) on solute release and swelling of matrix tablets. We used a semiquantitative optical imaging method to monitor the swelling of matrices with HPMC content from 20% to 80% (w/w) and four viscosity grades. Several aspects of the swelling process common to all formulations were revealed: (i) swelling is anisotropic with a preferential expansion in the axial direction, (ii) swelling is isotropic with respect to the gel layer thickness and composition in both axial and radial directions, (iii) the gel layer develops in three stages, and (iv) water penetration is Fickian in nature and essentially constant for all formulations. We monitored simultaneously drug, lactose, and HPMC release. Lactose and drug release rates were superimposed, indicating a similar diffusional release mechanism and no interaction with HPMC. The strong dependence of HPMC release on viscosity grade is explained on the basis of the concept of polymer disentanglement concentration. We analyzed drug release rates using a model for a reservoir-type release system that incorporates swelling kinetics. HPMC/lactose ratio modulates drug release rate by altering drug diffusivity, a function of gel composition. In contrast, HPMC viscosity grade impacts matrix dissolution and gel layer thickness development below a critical molecular weight. For slowly dissolving matrices containing high viscosity grade (> 4000 cps) HPMC, similar drug release rates are observed mainly due to the same drug diffusivity as a result of the identical gel composition and thickness. For fast dissolving matrices (< or = 100 cps) swelling inhomogeneity is proposed as being responsible for a higher apparent drug diffusivity and release rate.