Isolation and characterization of a 70 kDa protein from Mycobacterium avium.

Mycobacterium avium complex (MAC) is an intracellular pathogen which causes disseminated bacterial infection in immunocompromised individuals. This organism predominantly infects macrophages. Attachment of MAC to macrophages is the first step prior to invasion. We have previously shown that a 70 kDa protein of M. avium (Ma) is one of nine monocyte-binding proteins. In the present study, we have purified this protein from sonic extracts of Ma and studied some of its properties. The N-terminal sequence of this protein was identified and found to exhibit a strong homology to the 70 kDa heat shock protein (hsp) of M. leprae (Ml) and M. tuberculosis (Mtb). This protein was found to be present on the surface of the organism and was able to inhibit the attachment of intact Ma to human monocyte derived macrophages (MDM) up to 49% in an in vitro attachment assay using intact fluorescein isothiocyanate (FITC)-labelled Ma. Bovine serum albumin (BSA) and recombinant 70 kDa hsp from Mtb, which were used as controls, inhibited this attachment by 9.8 and 18%, respectively. These results suggest that the 70 kDa protein may have a role in the attachment of intact Ma to MDM. When tested in lymphocyte activation assays, this protein did not appear to significantly stimulate proliferation. However, it was found to stimulate the production of tumor necrosis factor (TNF)-alpha by MDM. This protein may be one of several Ma antigens that trigger host immune response by binding to MDM and stimulating the production of inflammatory cytokines such as TNF-alpha by these cells.

Clinical and electroneurophysiological assessment of leprosy patients on dapsone monotherapy--a two year follow-up study.

Fifty-three persons with tuberculoid type of leprosy having a thickened nerve on one side and a clinically normal nerve on the contralateral side were studied before, during and after two years of therapy for electrophysiological abnormalities in apparently normal and in obviously thickened nerves. Twenty-seven patients had received treatment with dapsone 100 mg orally and 26 cases had received rifampicin therapy. It was found that there was no extension of anesthesia or diminution of motor power over a period of two years. There was no significant difference between the initial and final recordings of motor and sensory nerve conductions if aggregate figures were taken. However, taking individual cases, deterioration in nerve conduction (increased latency and decreased velocity) was found in two patients, of whom one had received dapsone and the other had received rifampicin.

Identification of a 68 kd surface antigen of Mycobacterium avium that binds to human macrophages.

Infection caused by Mycobacterium avium is the major cause of bacteremia in patients with AIDS. A critical event in the initiation of a variety of bacterial infections is the adherence of bacteria to host cell surfaces, which is often brought about by the interaction of specific molecules on the bacterial surface with host cell surface receptors. In the present study, a sonicate of M. avium was used to isolate monocyte-binding proteins by affinity chromatography with CNBr-Sepharose-4B coupled to extracts of monocytes. A 68 kd protein present on the surface of M. avium was identified as one of nine monocyte-binding proteins. This protein was isolated and further characterized. The N-terminal amino acid sequence (22 residues) of the protein was determined and was found to exhibit strong homology with the 65 kd heat shock proteins of M. tuberculosis, M. leprae, and M. bovis. However, a previously characterized monoclonal antibody directed against a 66 kd antigen of M. avium was found to cross-react with the 68 kd protein from M. avium but not with the 65 kd proteins from M. leprae and M. bovis, suggesting that the 68 kd antigen may differ from the 65 kd proteins of M. leprae and M. bovis with respect to certain epitopes. In an in vitro inhibition assay, the 68 kd protein was found to compete with the attachment of intact fluorescein isothiocyanate-labeled M. avium to monocyte-derived macrophages, inhibiting this attachment in a dose-dependent manner up to 42%. The 65 kd proteins of M. leprae and M. bovis, on the other hand, did not appear to inhibit this attachment substantially (13.9% and 14.6%, respectively). These results suggest that the 68 kd protein of M. avium may be involved in binding to receptors on macrophages and help in the attachment of the organism to its host cell.

Electro neuro physiological studies in early tuberculoid leprosy.

Electro physiological studies were carried out in early tuberculoid type of leprosy in order to study their utility in detecting nerve damage before the onset of obvious functional deficit. Fifty-three cases showing one mixed nerve thickening in one limb were selected. Nerve conduction studies (both motor and sensory) were done using single blind technique. There was no statistically significant difference between the findings obtained from clinically thickened and non-thickened nerves. There was also no direct relationship between clinical sensory deficit and electro physiological abnormality. Clinical motor power loss was well correlated with electro physiological abnormalities.

Evaluation of disability knowledge and skills among leprosy workers.

The leprosy workers' knowledge and skills regarding disability prevention and control were quantified by a specially designed Objective Structured Clinical Examination (OSCE). The scorings were similar and showed no significant difference between supervisors and peripheral workers. It is suggested that the training component of disability control should be improved with emphasis on problem-oriented learning.

A study of leprosy affected beggars in Aska.

A study conducted among beggars in and around Aska, Orissa revealed 41 of them to be leprosy patients. Almost all had taken treatment and had been released from control. Only 2 of them were mildly positive in their skin smears for AFB. All of them had disabilities and deformities. It is evident that at least in this area beggar leprosy patients cannot be contributing to the transmission of the disease. Their treatment regularity record was also very good.