Glycoside-bearing liposomal delivery systems against macrophage-associated disorders involving Mycobacterium leprae and Mycobacterium tuberculosis.

Asiaticoside, a plant glycoside with rhamnose as end sugar and having microbicidal properties was tested against Mycobacterium leprae and Mycobacterium tuberculosis both in vivo and in vitro. As rhamnose is reported to have no tissue specificity, corchorusin D having glucose as end sugar was used for targeting with an equimolar proportion of asiaticoside in liposomal form for testing the drug value. Results showed that liposomal asiaticoside had better microbicidal property against M. leprae and M. tuberculosis when compared to that of free asiaticoside whereas liposomes containing asiaticoside and corchorusin D were found to be equally or more active in comparison to liposomal asiaticoside alone. It is inferred that appropriate glycosides, if used in liposomal form (incorporated or covalently grafted) have enhanced drug efficacy and such glycoside bearing liposomes as targeted delivery systems could be used for chemotherapeutic control of several other diseases.

Nature of peritoneal macrophages from DCC immunized mice.

Peritoneal macrophages from mice immunized with the delipidified cell component (DCC) of Mycobacterium leprae showed changes in various parameters such as increased protein synthesis, levels of hydrolytic enzyme and augmented phagocytic ability indicating activation of the cells. Furthermore, the surface structure of the cells were quite different from that of the macrophages of normal mice. These observations indicate that the peritoneal macrophages have been activated to phagocytose and kill M. leprae better in the immunized mice. The ability to kill the pathogen by these cells was reported by us earlier.

In vivo effect of delipidified cell component of Mycobacterium leprae in relation to infection with leprosy bacteria in mice.

The delipidified cell component (DCC) of Mycobacterium leprae was used as an immunomodulatory agent in Swiss white mice. The peritoneal macrophages of these mice were activated to produce increased amount of reactive oxygen intermediates like hydrogen peroxide (H2O2) and superoxide. These macrophages also attained the ability to kill M. Leprae in vitro as shown by several assay systems including the conventional mouse foot-pad technique. The increased levels of superoxide seem to be responsible for the killing of M. leprae as addition of the enzyme superoxide dismutase, which breaks down O2, resulted in survival of these bacilli inside the macrophages. The increased production of H2O2 does not seem to be responsible for killing M. leprae. The results indicate that the DCC of M. leprae acts as an effective immunomodulator in mice leading to the activation of macrophages with increased production of H2O2 and superoxide as well as enabling them to kill M. leprae via the action of superoxide anions.

Antigenic similarity of a cultivable acid fast bacterium to Mycobacterium leprae.

A cultivable acid fast stainable bacterium obtained from leprosy nodule showed similarity to M. leprae in antigenicity to serum antibodies of lepromatous leprosy patients. The antigenic similarity has been seen more clearly in the delipidified cell components of both these bacteria. An antigen of 35-38 kDa has been seen as a common antigen between M. leprae and the cultivable bacilli with binding ability to sera from leprosy patients. This cultivable bacterial component could be used for serodiagnosis of lepromatous leprosy.

Delipidified cell components of Mycobacterium leprae and its applications.

Delipidified cell components (DCC) of Mycobacterium leprae obtained as an insoluble material consist of several proteins. This preparation, DCC, has ability to differentially bind to sera from lepromatous leprosy patients and antibodies to this complex get reduced as patients improve under chemotherapy. The antigenic complex has no ability to bind to proteins of sera from normal healthy individuals or tuberculoid leprosy patients. The DCC is antigenic and is recognised by immune deficient cells of lepromatous leprosy patients, leading to lymphocyte proliferation, production of Interleukin II and interferon gamma, and resulting in activation of the phagocytes to initiate killing of endocytosed M.leprae through reactive oxygen intermediates, primarily superoxide. The DCC has also immunomodulatory properties to protect mice against M.leprae infection. Experiments with mice and isolated peripheral blood cells from patients have indicated the probable molecular mechanism of immunomodulation by DCC.

Correlation of in vitro Fc receptor assay with in vivo mouse foot pad method.

Resistant strains of M. leprae have been reported to the various antileprosy drugs. There is currently no accepted test to identify the susceptibility pattern of M. leprae to the drugs in a short period. The only accepted test is the mouse foot method which takes a long period to yield results. The Fc receptor assay using the ability of viable M. leprae to alter the membrane of the macrophage is well established. It takes only ten days and is inexpensive. In 6 cases of leprosy patients the susceptibility pattern was worked out both with the in vitro Fc receptor assay and the vivo in mouse foot method The results correlated very well leading to the fact that the assay system is reliable. Hence it can be used not only to study the status of a patient, but also to shortlist the number of compounds to be tested on the mouse foot pad as anti-leprosy drug candidates.

Mycobacterium leprae mediated stimulation of macrophages from leprosy patients and hydrogen peroxide production.

Macrophages cultured from the peripheral blood of normal individuals, tuberculoid leprosy patients and long-term-treated, bacteriologically negative lepromatous leprosy patients are able to release hydrogen peroxide on stimulation with Mycobacterium leprae. Macrophages from lepromatous leprosy patients who are bacteriologically positive produce considerably lower levels of hydrogen peroxide, even though stimulation of these cells with Mycobacterium leprae is definitely demonstrable. This differential stimulation of macrophages appears to be largely specific to Mycobacterium leprae. There is also a good indication that decreased stimulation of macrophages from positive patients could be due to an after-effect of infection. It is possible that while other factors aid survival of Mycobacterium leprae in the macrophages, hydrogen peroxide may not be as effective in the killing of the bacteria in infected patients as it would be, perhaps, in other infections.

Superoxide production from macrophages of leprosy patients after stimulation with Mycobacterium leprae.

The macrophages from peripheral blood of normal healthy individuals respond to live or killed Mycobacterium leprae by producing superoxide. On the other hand, the macrophages from bacteriologically positive (B + LL) or long term treated bacteriologically negative (B – LL) and tuberculoid leprosy patients are unable to produce superoxide when stimulated with live Mycobacterium leprae. While killed Mycobacterium leprae induce superoxide with the cells from tuberculoid and B(–)LL patients, cells from B(+)LL patients fail to respond. The deficiency in B(–)LL patients to produce superoxide appears to be specific with Mycobacterium leprae and the defect can be counteracted by the addition of colchicine. These observations indicate a preexisting membrane disposition which does not favour superoxide production. A similar situation is seen in the cells from tuberculoid leprosy patients. Thus it appears that both cured and active lepromatous leprosy patients have defective macrophages, unable to respond to live Mycobacterium leprae to produce superoxide anion, in contrast to the situation with the cells from normal healthy individuals.

Importance of determining viability of Mycobacterium leprae inside macrophages—an in vitro method using uracil.

It has been demonstrated that Mycobacterium leprae, are capable of taking up uracil and incorporating it into trichloroacetic acid-insoluble materials, both as free suspension of bacteria, as well as when they are inside the macrophages, a host cell for their in vivo survival. Same amount of bacteria show better incorporation inside macrophages than as free bacterial suspension. Both types of incorporation are inhibited by rifampicin an antileprosy drug and an RNA synthesis inhibitor. Thus uracil uptake by Mycobacterium leprae inside macrophages has been used for standardising a rapid in vitro viability assay for the leprosy causing bacteria.

A rapid method for viability and drug sensitivity of Mycobacterium leprae cultured in macrophages and using fluorescein diacetate.

The ability of viable M. leprae to hydrolyze Fluorescein diacetate and retain fluorescein inside the bacteria was used to identify viable M. leprae inside the cultured in vitro macrophages. The subjective microscopic count of the FDA test was demonstrated as useful routine test by confirming the results obtained therein with a quantitative and non subjective measurement of fluorescence in spectrofluorimeter. Using this method loss of viability of M. leprae in presence of dapsone and rifampicin was demonstrated. Such an assay, was well correlated with another in vitro assay, the Fc receptor test and also the in vivo mouse foot test. The drug resistance of clinical isolates of M. leprae demonstrated by mouse foot pad was also correlated with FDA test system. Thus we have reported a reliable, consistent and rapid in vitro test system for determining viability and drug sensitivity of M. leprae.

A comparative study of the efficacy of WHO and IAL multidrug therapy regimens for leprosy--an in-vivo and in-vitro study.

In the absence of definite evidence on utility of intensive therapy with rifampicin in multibacillary leprosy cases, a laboratory based investigation was undertaken basically to compare the efficacy of WHO and IAL regimens. In each group 4 untreated BL-LL patients were included and their skin biopsies were subjected for viability test both in vitro and in vivo systems. A consistant fall in BI with good clinical improvement was observed in both the groups. However good viability was maintained till about third pulse dose in WHO group whereas under IAL group rapid fall in viability was observed after intensive phase. Viable bacilli were seen even after 12,15,18 and 24 doses in both groups. These findings question the need for additional 21 doses of rifampicin in IAL schedule. However such studies are to be repeated on larger samples.

Lipase activity in Mycobacterium leprae--an indicator of metabolic function.

Presence of lipase, in Mycobacterium leprae obtained from human nodules and infected armadillo tissues, has been detected by demonstrating the ability of the bacteria to hydrolyze tributyrin. This capacity is expressed during incubation of the bacteria with the substrate and needs a source of carbon and other energy metabolites. The activity is blocked by anti M. leprae drug rifampicin. It is concluded that expression of lipase activity is a metabolic event of M. leprae, while they are maintained in an energy providing medium.

Minimum inhibitory concentration of drugs against Mycobacterium leprae as determined by an in vitro assay.

The observations that live Mycobacterium leprae after entry into cultured peritoneal macrophages from mice, reduced the EA rosetting macrophages, have been exploited to determine the minimum inhibitory concentration of diamino diphenyl sulphone and rifampicin. Diamino diphenyl sulphone showed a minimum inhibitory concentration of 0·028 μg/ml and rifampicin 0·11 μg/ml when given externally. However, there was accumulation of diamino diphenyl sulphone inside the macrophages. At an external concentration of 0·028 μg/ml the concentration inside the macrophage was 0·5 μg/ml. The minimum inhibitory concentration for diamino diphenyl sulphone in this assay system is higher by several folds and that for rifampicin is slightly lower, than what is reported earlier with mice foot pad experiments. The minimum inhibitory concentration reported in this assay system is quite close to what is observed for in vitro inhibition of Mycobacterium lufu with both the drugs.

In vitro drug screening system using membrane alteration in macrophages by Mycobacterium leprae.

The observation that live Mycobacterium leprae on entry into macrophages from lepromatous leprosy patients reduced the number of EA rosetting macrophages, was extended to macrophages from Swiss white mice also. Further, the fact that dead Mycobacterium leprae do not bring about such a change in macrophages from mice, allowed us to develop this into a bacterial viability testing system. Thus drug treated macrophages in the presence of Mycobacterium leprae showed normal rosetting ability if Mycobacterium leprae are inactivated by the drug, but showed reduced level of rosetting when bacteria were not susceptible to the drug. It was shown that a drug like dapsone, does act on Mycobacterium leprae based on its permeability, quantity available inside the macrophages and inhibition of its action by Para amino benzoic acid. The inactivation of Mycobacterium leprae by sulphone and rifampicin was also proved by the flourescence diacetate method, which showed poorly viable bacteria after exposure to drugs. Thus it has been possible to develop a rapid drug screening method for testing the activity of unknown compound against Mycobacterium leprae.

Hydrolytic enzymes in macrophages from leprosy patients in presence of Mycobacterium leprae.

Presence of Mycobacterium leprae in association with in vitro cultured macrophages, from bacillary negative long term treated lepromatous leprosy patients, induces reduced level of protein and lowering of hydrolytic enzymes like p-glucuronidase, Lysozyme and Lactic dehydrogenase. Alkaline phosphatase, on the other hand is increased. In the macrophages from normal healthy individuals or tuberculoid leprosy patients, presence of M.leprae increases both protein and levels of all the above enzymes. This observation shows that macrophages from lepromatous leprosy patients are unable to manifest in presence of M. leprae, the key enzymes involved in degradation of complex biological entities phagocytosed by the cells.

An in vitro test using cholesterol metabolism of macrophages to determine drug sensitivity and resistance of Mycobacterium leprae.

Macrophages that have ingested live Mycobacterium leprae show a preferential accumulation of cholesterol ester. Such an accumulation is not seen, on the ingestion of dead bacteria. Among the macrophages that ingest live Mycobacterium leprae, the presence of dapsone or rifampicin prevents largely the alteration in the anticipated increase in the cholesterol ester indicating the sensitivity of the bacteria to the drug. In the small number of relapsed patients, the presence of dapsone did not reduce the cholesterol ester increase, suggesting that the Mycobacterium leprae present are either resistant or escaped detection. The method provides a rapid drug screening system for anti-Mycobacterium leprae activity of known and unknown compounds.