T-lymphocytes in leprosy lesions.
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Humans↗
Biomedical subjects
V Mehra
Publications and source records attributed to V Mehra.
3.8 million blinded by cataract each year: projections from the first epidemiological study of incidence of cataract blindness in India.
Data from a population based longitudinal study of randomly selected communities in Central India have for the first time provided direct estimates of age specific incidence of blindness from cataract. Person-time denominators have been used to compute age specific incidence rates (risk) of blindness from cataract for populations aged 35 and older. These age specific incidence measures have been applied to the 'population at risk' in each 5-year age class in order to estimate the total number of new cases of cataract blindness that occur in the country each year. The findings indicate that an estimated 3.8 million persons become blind from cataract each year in India (approximate 95% confidence limits: 3 to 4.5 million). The reasons why the estimates are considered as minima, and their implications concerning future national planning of ophthalmic services, are briefly discussed.
Adult↗
Delayed eye and other consequences from exposure to methyl isocyanate: 93% follow up of exposed and unexposed cohorts in Bhopal.
A follow up study three years after exposure to methyl isocyanate in 93% of exposed survivors and "control" residents in 10 Bhopali communities showed an excess of eye irritation, eyelid infection, cataract, and a decrease in visual acuity among the exposed people. Breathlessness was twice as common in the heavily exposed clusters as those with lower exposure, a trend that could not be explained by different age or smoking patterns (OR 2.05, 95% CI 1.36-3.08). Case referent analysis of outpatient attendances at Bhopal Eye Hospital, considering patients with severe refractive errors and astigmatism as "controls," showed a 40% increased risk of trachoma, 36% increased risk of other lid infections, and 45% increased risk of irritant symptoms among previously exposed people. "Bhopal eye syndrome" may thus include full resolution of the initial interpalpebral superficial erosion, a subsequent increased risk of eye infections, hyperresponsive phenomena (irritation, watering, and phlyctens), and possibly cataracts. It remains to be confirmed whether this reflects a more generalised disease as a consequence of previous exposure to methyl isocyanate or whether it is only the eye that is affected.
Accidents, Occupational↗
Characterization of T cell antigens associated with the cell wall protein-peptidoglycan complex of Mycobacterium tuberculosis.
Mycobacterium tuberculosis cell walls are likely to contain critical T cell Ag capable of inducing protective immunity against the development of tuberculosis in animal models. Therefore, we characterized cell wall-associated Ag that stimulate T lymphocytes in tuberculosis patients and clinically well tuberculin-positive individuals. A protein-peptidoglycan complex isolated from the M. tuberculosis cell wall had potent immunologic activity, evoking PBMC proliferative responses similar to those induced by sonicated whole M. tuberculosis. In order to characterize the immunoreactive protein determinants associated with the protein-peptidoglycan complex, T cell lines were established to cell wall Ag and used to probe M. tuberculosis proteins separated by SDS-PAGE. These T cell lines proliferated primarily to protein Ag of 10, 19, 23, 28, 30, 40 to 50, and 65 kDa. Cell wall-reactive T cell clones that recognized the 10-, 23-, 28-, and 30-kDa proteins as single bands on SDS-PAGE did so under reducing and nonreducing conditions, suggesting that these are not proteolytic fragments or subunits of larger protein aggregates. We propose that these protein monomers, when post-translationally complexed with peptidoglycan, are the key ingredients of the immunogenic protein-peptidoglycan complex. In order to assess the relationship of the cell wall-associated Ag to those secreted proteins from "early culture filtrates" of actively growing M. tuberculosis recently implicated in eliciting protective immunity, cell wall-reactive T cell clones were tested for their ability to recognize early culture filtrates. Results revealed that at least three proteins shared with the cell wall complex are contained within early culture filtrates. Our data indicate that antigenic determinants associated with the protein-peptidoglycan complex of the M. tuberculosis cell wall may be involved in protective immunity and hence are potential candidates for inclusion in an effective antituberculosis vaccine.
Antigens, Bacterial↗
Isolation and characterization of the highly immunogenic cell wall-associated protein of Mycobacterium leprae.
In a recent study, we demonstrated that certain reactivities crucial to the immune response in leprosy are due to protein associated with the cell wall peptidoglycan "core" of Mycobacterium leprae. We now describe a primary method for the isolation of a highly immunogenic, large molecular-size, cell wall protein (CW-P) complex from M. leprae, freed of soluble proteins, bound mycolates, arabinogalactan, and much of the peptidoglycan. The complex is of apparent relative molecular size 2 x 10(6) to 20 x 10(6) Da, is distinguished by a high content of Ala, Gly, Leu, Asx, and Glx, and some peptidoglycan, and represents up to 7% of the bacterial mass. It is stable to a variety of dissociation and reductive processes and, in accord with its size, is not resolvable by polyacrylamide gel electrophoresis. The mAb to the CW-P complex also react with the heat shock 65-kDa protein of M. leprae. Conversely, antibodies that recognize internal epitopes within the polypeptide chain of the heat shock protein also react with CW-P; however, antibodies that recognize the N and C termini of the 65-kDa protein fail to react with CW-P, and some anti-CW-P mAb do not recognize any of the soluble proteins of M. leprae. Alternate methods to derive the large peptidoglycan-associated protein result in lower yield and less of the associated heat shock protein, implying that the 65-kDa protein may not be crucial to the immunogenicity of the complex. In an accompanying paper, we demonstrate that T cell clones raised to CW-P also selectively recognize soluble proteins, primarily of 7-kDa and 16-kDa size. Thus, the image of the CW-P complex of M. leprae is of a few immunoreactive polypeptides in avid association with a modicum of peptidoglycan to which the 65-kDa polypeptide may be variably attached, perhaps due to involvement in assembly of the complex.
Amino Acids↗
Characterization of Mycobacterium leprae cell wall-associated proteins with the use of T lymphocyte clones.
Development of a vaccine against leprosy depends on the identification of Ag that stimulate cell-mediated immune responses. We have previously demonstrated that cell wall proteins of Mycobacterium leprae are highly immunogenic. By using human cell wall-specific T cell clones we have begun to characterize soluble proteins that integrate into the cell wall skeleton. T cells from leprosy lesions were expanded with IL-2 in vitro yet retained specificity to Ag of the insoluble cell wall core (CWC) in vitro, indicating that T cells had been activated by CWC Ag in vivo. A cell wall protein-peptidoglycan complex and cell wall protein preparations lacking carbohydrates and lipids from CWC retained T cell reactivity. To identify immunogenic protein component(s) of cell wall protein, T cell lines were established to cell walls and tested against M. leprae proteins separated by SDS-PAGE and transferred to nitrocellulose. Greatest T cell reactivity was observed to proteins of Mr 7 kDa, 16 kDa, and 28 kDa. T cell clones reactive with 7-kDa and 16-kDa Ag from gels failed to respond to proteins of other Mr separated under either reducing or nonreducing conditions, indicating that these molecules are not subunits of larger proteins and may represent monomeric units polymerized into cell walls. The approaches described herein for characterization of immunodominant T cell Ag of M. leprae may be useful for study of T cell Ag in cell walls of bacterial pathogens of man.
Bacterial Proteins↗
Dehydrational crises: a major risk factor in blinding cataract.
An earlier case control investigation has indicated a strong relationship between dehydrational crises and risk of presenile cataract. A second methodologically distinct case control study of risk factors in cataract has been carried out in a population very different in terms of environmental and sociocultural characteristics from the population investigated in the earlier study in Central India. The results strongly confirm the findings from the first study and indicate that an estimated 38% of blinding cataract may be attributable to repeated dehydrational crises resulting from severe life threatening diarrhoeal disease and/or heatstroke. The risk of blinding cataract was strongly related to level of exposure to dehydrational crises in a consistent and dose dependent manner, thus indicating a causal association. The findings are discussed in relation to possible sources of bias in the study, confounding in the data, and the steps that were taken to minimise their undesirable effects.
Adult↗
Vaccine development. On relating immunology to the Third World: some studies on leprosy.
Leprosy is of interest to immunologists because the varied clinical manifestations of the disease correlate closely with the immunological spectrum. Resistance to infection is dependent on appropriate cell-mediated immunity, but patients with the lepromatous form fail to respond to antigens of M. leprae. In vitro studies have revealed the existence of T-suppressor cells of the phenotype CD8+, CD3+, HLA-DR+, FcR+, 9.3-, which are restricted by major histocompatibility complex (MHC) class II antigens. Several new candidate vaccines against leprosy have been effective in breaking immunological unresponsiveness and engendering cell-mediated immunity in lepromatous leprosy patients, including the combination of BCG+ killed M. leprae. Because BCG has unique adjuvant properties, we have begun to use molecular genetic approaches to develop BCG into a multivaccine vehicle capable of immunizing simultaneously against several pathogens. Both phage-based and plasmid-based strategies have been successfully developed for introducing selectable markers into BCG for the first time.
Bacterial Vaccines↗
Mechanisms of immunological unresponsiveness in the spectra of leprosy and leishmaniasis.
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Humans↗
Immunological significance of Mycobacterium leprae cell walls.
Cell walls of Mycobacterium leprae, prepared by differential solvent extraction, were shown to contain arabinogalactan, mycolates, and peptidoglycan. In addition, amino acid analysis revealed the unexpected presence of large amounts of protein that retained potent immunological reactivity. Purified cell walls stimulated proliferation of T cells from tuberculoid, but not from lepromatous leprosy, patients and elicited delayed-type hypersensitivity skin reactions in guinea pigs and patients sensitized to M. leprae. Analysis of the precursor frequency of antigen-reactive human peripheral T cells revealed that as many cells (approximately equal to 1/6000) proliferate to antigen contained in cell walls as to intact M. leprae. Sequential removal of mycolates and arabinogalactan resulted in a large peptidoglycan-protein complex that retained all the immunological activity. This immunological reactivity and the inherent protein were destroyed by proteolysis. Thus, cell wall protein is a major contributor to cell-mediated immune reactivity to this pathogenic mycobacterium.
Amino Acids↗
A rapid method of grading cataract in epidemiological studies and eye surveys.
A rapid method of grading clinically important central lens opacities has been developed for use in eye surveys and in epidemiological studies of cataract and has been field-tested in a specifically designed observer agreement study in a survey of a rural community in Central India. The grading method is based on simple measurement of the area of lens opacity that obscures the red reflex relative to the area of clear red reflex, as visualised through the undilated normal pupil. Good to almost perfect agreements were attained between two ophthalmologists and two trained ophthalmic assistants for overall grades of central lens opacity. Most disagreements were trivial in nature and were concerned with difficulties in distinguishing grade 0 from grade 1, and with hazy appearance of the red reflex in high myopes and in cases of early nuclear sclerosis. Teaching materials including video tape and slides for training survey teams and other workers are in preparation.
Cataract↗
Exposure and response to methyl isocyanate: results of a community based survey in Bhopal.
In the two weeks immediately after the Bhopal disaster a community based survey was carried out in a series of eight exposed and two non-exposed clusters of households. The primary concern was the effect of the gas (subsequently identified as methyl isocyanate) on the eyes of the victims but data were also sought on respiratory status and the first symptoms of the exposure. No case of blindness was encountered that could be attributed to the gas. The most frequent symptoms reported were burning of the eyes, coughing, watering of the eyes, and vomiting. Among these, the frequency of cough most closely followed the rate of death in the different clusters. Although much rarer overall, the frequency of reported diarrhoea appeared to bear a stronger relation to death rates. Reports of photophobia and the clinical finding of superficial interpalpebral erosion of the cornea were more frequent where the death rates were lower. This clinical and epidemiological picture is consistent with different effects of the gas at different doses (as estimated from distance from the factory).
Accidents, Occupational↗
Triglyceride tolerance test: is it feasible?
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Coronary Disease↗
Suppressor T lymphocytes from lepromatous leprosy skin lesions.
The immune response in leprosy forms a spectrum with lepromatous leprosy patients exhibiting specific unresponsiveness to antigens of Mycobacterium leprae. This unresponsiveness is thought to be related to the prevalence of T8-positive lymphocyte in these lepromatous lesions. To analyze the immunoregulatory function of these T8 cells, we developed simple procedures to extract lymphocytes from skin biopsy specimens of patients with leprosy. These lymphocytes were sorted for T8 and T4 positive cells, and cell lines were established by expansion with interleukin 2 (IL 2) and irradiated feeder cells. All T8 positive lines tested were positive for IL 2 receptors and HLA-DR determinants. These lines were additionally assayed for lepromin-induced suppression of the normal peripheral blood lymphocyte Con A proliferative response. Thirteen of 32 lines from six lepromatous patients showed significant suppressor activity, whereas nine lines from six tuberculoid patients and one line from normal peripheral blood failed to show suppression (p less than 0.001). Taken together, the finding of M. leprae-triggered suppressor cells within lepromatous skin lesions may in part explain the M. leprae unresponsiveness of lepromatous leprosy patients.
Antigens↗
In situ and in vitro characterization of the cellular immune response in erythema nodosum leprosum.
We sought to evaluate cell-mediated immune responses in erythema nodosum leprosum (ENL), a reactional state occurring in lepromatous leprosy. Skin biopsies from patients with leprosy were studied with monoclonal antibodies against T lymphocyte antigenic determinants, interleukin 2 (IL 2), and IL 2 receptors (Tac) by using immunoperoxidase staining of frozen sections. Peripheral blood lymphocytes from 18 ENL patients were tested in vitro for lepromin-induced suppression of Con A stimulation. Serial studies of seven lepromatous patients who developed ENL during the course of the study showed increases in both the Leu-3a:Leu-2a ratio and the number of IL 2-positive cells. IL 2-positive cells comprised 0.3% of the cells in all of the ENL lesions studied as compared with the 0.03% found in nonreactional lepromatous lesions (P less than 0.001). Lepromin-induced suppression of the Con A response, present in nonreactional lepromatous patients, significantly decreased in patients developing the ENL reaction, but returned after recovery from ENL. These changes in tissues and peripheral blood suggest that the pathogenesis of ENL is related to cell-mediated immune processes. Despite these immunologic changes, however, ENL patients do not recover antigen-specific skin tests or eliminate Mycobacterium leprae.
Antibodies, Monoclonal↗
Efficient mapping of protein antigenic determinants.
A recombinant DNA expression strategy has been used to deduce the amino acid sequences of six different antigenic determinants in a single protein of Mycobacterium leprae, the etiologic agent of leprosy. The gene encoding the M. leprae 65-kDa antigen was sequenced and a lambda gt11 gene sublibrary was constructed with fragments of the gene. Recombinant DNA clones producing specific antigenic determinants were isolated by screening with monoclonal antibodies, and the sequences of their insert DNAs were determined with a rapid primer-extension method. The amino acid sequence of each determinant was deduced from the minimum overlap of insert DNAs from multiple antibody-positive DNA clones. Amino acid sequences for six different epitopes were elucidated. A peptide containing sequences for one of these epitopes was synthesized and shown to bind the appropriate monoclonal antibody; this antigenic determinant is unique to M. leprae. The approach described here can be used to rapidly elucidate protein epitopes that are recognized by antibodies or T cells.
Amino Acid Sequence↗
Bhopal disaster: eye follow-up and analytical chemistry.
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Accidents, Occupational↗