PubMed · 7758305
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P Zenarola, A Gimma, M Lomuto. 1995. Systemic contact dermatitis from thimerosal.. https://doi.org/10.1111/j.1600-0536.1995.tb00756.x
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The effect of reconstituting freeze-dried vaccine cultures of Mycoplasma mycoides subsp. mycoides small colony biotype (MmmSC) strain T(1)44 grown in standard vaccine medium using variable quantities of un-buffered solutions of 1 M MgSO(4) (the current O.I.E.-recommended procedure) has been investigated. Compared to the culture pH prior to desiccation, a drop of up to 2.2 pH units was observed, dependent upon the volume and pH of 1 M MgSO(4) used (1-30 x original culture volume, using 1 M MgSO(4) in the pH range 5.4-7.6). This pH drop appears to be due to the removal of the HPO(4)(2-) buffer capacity of the medium by the formation of insoluble Mg(3)(PO(4))(2) and the release of free H(+) ions. As a result of this lower pH, markedly reduced culture viability was observed over an 8-h period at 37 degrees C for vaccines re-suspended in 1 M MgSO(4) (ca. 6 log(10) drop in titre) compared to re-suspension in dH(2)O (ca. 1.5 log(10) drop in titre). Re-suspension in 1 M MgSO(4) did exhibit a thermoprotective effect at 46 degrees C, but only when the pH was maintained above pH 7.0 by use of HEPES-buffered growth medium (1 log(10) drop in titre compared to 6 log(10) drop using dH(2)O over an 8-h period). Since all current O.I.E.-recommended growth media for MmmSC are based upon a phosphate buffer system, it is therefore recommended that the use of 1 M MgSO(4) as a reconstitution fluid be discontinued as soon as possible and buffered saline be used instead. The use of this reconstitution procedure with the T(1)44 vaccine strain could be a significant factor in the poor efficacy observed with current freeze-dried vaccines against contagious bovine pleuropneumonia in Africa.
The antigenic extract Hot Saline from Brucella ovis was microencapsulated by the spray-drying technique with different polyesters (poly-lactide-co-glycolide RG502H [PLGA], and blends with poly- epsilon -caprolactone [PEC]) in order to obtain microparticles smaller than 5 microm. Microparticles were tested for encapsulation efficiency, release studies, acidification of the in vitro release medium, and in vitro J744-macrophage experiments (phagocytosis and toxicity of the preparations) to determine the optimal formulation for vaccination purposes. Formulation containing no PCL showed the highest encapsulation efficiency, although the differences were not significant. The in vitro release kinetics were characterized by a high burst effect after 1 h of incubation, followed by a slow and continuous release. For the formulation based on PLGA, the pH of the medium during release dropped from 7.4 to 3.5 while the presence of PEC attenuated the pH drop. All formulations showed light toxicity by the MTT assay, but differences were observed in terms of phagocytosis, as particles prepared with PEC showed the higher uptake by J744-macrophages and cell respiratory burst, determined by oxygen peroxide release. All these characteristics suggest that the microparticulated antigenic formulation containing the higher ratio of PEC is susceptible to be used in animal vaccination studies.
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