In vitro cultivation of leprosy bacilli in hyaluronic acid-based medium. 2. Progress and developing concept of the role of hyaluronic acid suggested by culture and armadillo infection studies.

Progress is summarized relating to the verification, identification of M. leprae and understanding of the process of adaptation the pathogen passes through before in vitro growth takes place. It is recognized that hyaluronic acid apparently does not serve as a source of energy but the possibility is presented that it plays a role in the reconstruction of M. leprae cell walls made "leaky" by constant intracellular life. This apparently occurs, in culture, initially by the development of coccoid forms which after a period of weeks finally give rise to acid-fast bacilli. If these understandings are correct and the bacillary cell walls are vitated by enzyme and other action occasioned by intra-macrophage existence, then cell wall antigenicity may also be vitiated or altered by intracellular parasitism and restored by in vitro cultivation. The possible importance of this hypothesis in the understanding of immunologic responses in leprosy, and in the possibilities for therapeutic use and vaccine development are discussed.