Antigenicity of phosphatidyl inositomannosides of Mycobacterium tuberculosis

Induction of immunity against experimental tuberculosis with mycobacterial mannophosphoinositides encapsulated in liposomes containing lipid A

Mycobacterial mannophosphoinositides (PIMs) encapsulated in liposomes made of egg phosphatidylcholine (EPC) and cholesterol (CH) (2:1.5 molar ratio) were able to induce humoral and delayed type hypersensitivity (DTH, foot-pad swelling reaction) responses in mice without the help of any carrier protein. Animals immunized with this glycophospholipid antigen demonstrated enhanced percent survival on intravenous challenge with virulent M. tuberculosis. On fractionation of PIMs, pentamannophosphoinositide (PIM5) was found to induce higher antibody and DTH reaction and proved to be more immunoprotective than other fractions. Inclusion of lipid A as immunomodulator in liposomes containing PIMs or PIM5 resulted in a significantly increased immune response. Further, mice immunized with PIMs or PIM5 in lipid A-containing liposomes exhibited decreased mortality on challenge with M. tuberculosis H37Rv, which was comparable to BCG vaccinated animals.

The synthesis and resolution of (+/-)-1,5,6-tri-O-benzyl-myo-inositol

Racemic 1,5,6-tri-O-benzyl-myo-inositol was prepared by five routes and converted into 1,5,6-tri-O-benzyl-2,3-O-isopropylidene-myo-inositol, the camphanates of which were readily separated by chromatography. The absolute configurations of the chiral derivatives were established by their conversion into the known chiral 1,4,5,6-tetra-O-benzyl-myo-inositols. 1D-1,5,6-Tri-O-benzyl-2,3-O-isopropylidene-myo-inositol was converted into 1D-1,3,5,6-tetra-O-benzyl-myo-inositol and thence into 1D-2,4-di-O-methyl-myo-inositol. 1D-1,5,6-Tri-O-benzyl-myo-inositol was converted into 1D-1,2,5,6-tetra-O-benzyl-myo-inositol, the diacetate of which is a chiral analogue of "thermosalient crystals". The potential of the above compounds for the synthesis of natural products is surveyed.

Activation of mouse peritoneal macrophages by mannophosphoinositides of mycobacteria

Peritoneal macrophages isolated from mannoside-methylated bovine serum albumin (MBSA)-immunized mice showed significantly enhanced phagocytosis of Mycobacterium smegmatis compared to control or MBSA-immunized groups. Immune macrophages also exhibited bacteriostatic activity against M. smegmatis. Pretreatment of mycobacteria with mannoside antibodies did not further alter the phagocytosis and bacteriostatic effect of immune macrophages.

Comparative evaluation of the diagnostic significance of circulating immune complexes and antibodies to phosphatidylinositomannosides in pulmonary tuberculosis by enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay was developed to detect circulating immune complexes (CIC) and antibodies to phosphatidylinositomannosides (PIM) of mycobacteria for the diagnosis of pulmonary tuberculosis. Identification of PIM in CIC of smear and culture positive (SPCP) cases revealed 88% sensitivity and antibodies to PIM were detected in circulation in 94% cases. The smear negative and culture positive (SNCP) group had 67% positivity with regards to PIM in CIC and 83% for antibodies to PIM in circulation. In the smear negative and culture negative (SNCN) group, 40% samples were found to have PIM in CIC and 20% exhibited antibodies to PIM. The high degree of sensitivity was observed with both antigen detection in CIC and antibodies to PIM in circulation.

Protective immunity to experimental tuberculosis by mannophosphoinositides of mycobacteria

Mannophosphoinositides isolated from mycobacterial cells were found to induce both humoral and cell-mediated immune responses in mice when injected as mannoside-methylated bovine serum albumin (MBSA) complexes. Immunization of mice with mannoside-MBSA complexes elicited significant protection against challenge with LD50 dose of M. tuberculosis H37Rv as revealed by high survival rate, low values of root-specific lung weight, lung densities and colony forming units recovered from lung, liver and spleen, compared to the nonimmunized group. These observations were further substantiated by histopathological studies. The protective immunity elicited by mannoside-MBSA complexes against challenge with M. tuberculosis H37Rv was mediated by the cooperation of T-B cells, as shown by the passive transfer of immune cells/sera into syngeneic sublethally irradiated recipient mice.

Subcellular distribution of mannophosphoinositides in Mycobacterium smegmatis during growth

Subcellular distribution of total phospholipids and mannophosphoinositides (mannosides) was examined in Mycobacterium smegmatis ATCC 607 during its transition from the early exponential to the stationary phase of growth. There was relatively more of these substances in the cell membrane than in the cell wall, and the total amount increased with the age of the culture. Among individual mannosides, dimannophosphoinositides (dimannosides) were distributed equally in the cell wall and membrane. However, hexamannophosphoinositides (hexamannosides) were more predominant in the cell membrane, and the level increased with the age of the culture.

Immunological studies with sulpholipids of mycobacteria

Antibodies to sulpholipids of mycobacteria were produced in rabbits when injected as sulpholipid-MBSA complexes and were detected by kaolin agglutination and double diffusion techniques. Sulpholipid antibodies did not cross react with any other lipids of mycobacteria except cord-factor. The antigenicity of sulpholipids appears to be due to alpha-D-trehalose and sulphate groups. Guinea pigs immunized with sulpholipid-MBSA complexes showed partial protection against tuberculous infection with M. tuberculosis H37Rv, as revealed by mortality rate and score of lesions.

Immunogenicity of type-specific C-mycoside glycopeptidolipids of mycobacteria

Specific rabbit antibodies were obtained from the inoculation of a complex composed of methylated bovine serum albumin and the superficial type-specific C-mycoside glycopeptidolipid (GPL) antigens from serovar 20 of the Mycobacterium avium-M. intracellulare-M. scrofulaceum complex. Although the GPLs on their own are serologically active, they require the protein carrier for immunogenicity. Antibodies to the complex were detected by seroagglutination, gel diffusion, and indirect immunofluorescence. Cross-reaction was observed in the case of just one of 16 M. avium-M. intracellulare-M. scrofulaceum complex serovars tested (serovar 41). Double gel diffusion and immunoelectrophoresis showed two major antigen-antibody complexes in the reaction between anti-GPL-methylated bovine serum albumin and the GPL antigens. The studies of migration pattern and absorption indicated that immunoglobulin M was responsible for one of these complexes, whereas the antibody responsible for the second complex was unidentified. The specific anti-GPL serum is a useful tool for the identification and classification of atypical mycobacteria and for the study of the fate of the organisms and their superficies during phagocytosis.

Antibody response to sulfolipids in experimental tuberculosis

Live Mycobacterium tuberculosis H37Rv, when injected into guinea pigs, induced antibodies to sulfolipids whereas antibodies were not detected in animals injected with heat killed cells. The antibody titre was found to be related to the degree of infection. A significant decrease in the titre was noted after streptomycin treatment, suggesting that antibodies were produced in response to an increasing bacterial load that occurred as the infection progressed.

Antibodies to phospholipids in experimental nocardiosis

Live Nocardia asteroides injected intraperitoneally into guinea pigs produced antibodies to phospholipids of Nocardia whereas antibodies were not detected in animals injected with heat-killed N. asteroides. The antibody titer was found to be related with the degree of infection; a significant decrease was noted after sulfadiazine treatment suggesting that antibodies were produced in response to an increasing bacterial load that occurred as the infection progressed.