Evaluation of standard Dharmendra lepromin.

Dharmendra lepromin standardized at Central JALMA Institute for Leprosy (CJIL) by bacterial counts was used by different observers in four different Centres to assess the early and late reactions. Patients taken into the study were from different ethnic groups in different regions of the country. Comparable skin reactions were found at the Bombay Leprosy Project (BLP), Bombay and at the CJIL, Agra wherein a large number of patients were taken in the study. Similarly, when a smaller number of patients were taken in the study at the Base Hospital (BH), Barrackpore, and at the Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Pondicherry, the skin reactions noted in patients at these Centres were again found to be statistically comparable.

Assessment of diluted Dharmendra lepromin.

Twenty-one patients of lepromatous and tuberculoid type were tested with standard, 1:2 and 1:4 diluted Dharmendra lepromin. It was found that correlation exists between the degree of induration and the number of bacilli in the lepromin. Uniform and reproducible results were obtained with Dharmendra antigen containing 40 million bacilli/ml. This is of special significance in enhancing the present meagre supplies of lepromin.

Recommended safety requirements for the preparation of lepromin: a WHO Memorandum.

The need for standardizing the preparation of lepromin and establishing safety requirements for it was recognized by the Scientific Working Group on the Immunology of Leprosy (IMMLEP) and its Steering Committee in 1978. It has now recommended the preparation of standard integral (Mitsuda-type) lepromin and, in collaboration with the WHO Biologicals unit, has drafted requirements for its preparation and testing. These direct that the source material should be Mycobacterium leprae from biopsy specimens of skin obtained from human (lepromatous) tissues or from the tissues of armadillos infected with M. leprae. The procedures to be followed for processing and testing the source material and for the preparation of lepromin from it are described. Requirements are laid down for the safety testing and labelling of the final product. In future, IMMLEP will consider supporting only those projects involving the use of lepromin prepared in accordance with these regulations.

Studies towards the standardization of lepromin. Progress and prospects.

Because of the wide range of concentrations of Mycobacterium leprae in existing lepromins the authors studied methods of producing a standardizable lepromin containing 160 million bacilli/ml. The effects of using different dilutions of lepromin on the incidence of false-positive reactions were also studied.Progress reported includes a convenient method for preparing large batches of non-sedimenting lepromin, which is directly suitable for microscopic counting of Myco. leprae cells; and a validation of current methods for microscopic enumeration of Myco. leprae. Skin tests with diluted lepromins have demonstrated that dilutions up to 1:16 increase progressively the ability to distinguish between lepromatous and tuberculoid leprosy. This work has provided further evidence that 20 million bacilli/ml (a 1:8 dilution of the initial lepromin) should produce adequate Mitsuda reactions in general populations, provided that 3-mm reactions are taken as the criterion for 1+ positivity. The net effect of these findings is equivalent to expanding the world supply of lepromin by 8 times.Recommendations for further research are proposed.