Tuberculin sensitivity and morphological immune response in guinea pigs after application of minimal sensitizing dose of BCG vaccine, substrain Sofia SL222.

During the investigation of the BCG allergenic potency it is advisable to vaccinate with decreasing doses, estimating the lowest dose that induces tuberculin sensitivity and specific morphological inflammation. Although the biological test does not reveal the mathematical correlation of dose-effect relationships, it is important to look for the determination of the minimal sensitizing dose for every BCG vaccine. In this study, three groups of twenty four guinea pigs were vaccinated with decreasing doses of reconstituted BCG vaccine: 120 ng, 12 ng and 1.2 ng. Tuberculin tests were performed in different groups at the 30th, 60th, 90th and 120th day after BCG injection. The negative tuberculin reactions converted to positive between the 60th and 90th day. The dose of 12 ng elicited the largest tuberculin reactions in the animals. This dose contains 65 viable bacteria and could be regarded as the smallest effective sensitizing dose of the BCG vaccine, substrain Sofia SL222. The morphological examination demonstrated that very low inoculums (1.2 ng or 6 viable cells) were sufficient to induce a specific inflammation after BCG vaccination. The immune response in lungs and bronchus-associated lymphoid tissue (BALT) of all BCG doses applied was strongest on the day 60. In the same term, lymph nodes and spleens were characterized with blast transformed lymphoid follicles with epitheloid and Langhans giant cells even with the smallest injected dose of 1.2 ng.

BCG vaccine therapy for treatment of superficial bladder cancer.

A total of 42 patients were involved in the study of the effectiveness of BCG vaccine on superficial bladder tumours. The new Bulgarian vaccine CALGEVAX was administered intravesically in consecutive instillations once weekly and then once monthly for a period of 11 months. For intradermal application the F-70 subcellular preparation was used. On the grounds of their initial experience in the treatment of superficial bladder tumours with unspecific immunotherapy the authors would like to express their confidence in the effectiveness of the intravesical application of BCG vaccine.

Studies on the biological activity of two strains of BCG: influence of production conditions.

Batches of freeze-dried BCG vaccine were produced by using two different substrains--Moscow (SL 374a) and Paris (SL 1173 P2). The biological activity of the vaccines was studied by the following tests: In the laboratory--viability, heat stability, homogeneity, skin reactivity, allergenic potency and immunogenicity in guinea pigs. In the field--local lesions and postvaccination tuberculin sensitivity. All the batches were produced by using the same technique and production methods. The Paris substrain vaccines showed less viability, but higher heat stability and skin reactivity. It is to be noted that when the VKL medium was used (instead of Sauton) the Paris substrain vaccines showed much lower immunogenicity in guinea pigs and, at the same time, much higher skin reactivity. In the field studies the Moscow substrain vaccines showed higher local lesions and tuberculin sensitivity. In other experiments vaccines produced from the same substrain (Moscow) but in different production centers were compared. It was found that the vaccines differed (according to the production methods used) in terms of some laboratory tests (viability, heat stability, homogeneity) but these differences were not associated with significant differences when studied in the field.