No abstract

Background: Small heat shock proteins are ubiquitous family of stress proteins, having a role in virulence and survival of the pathogen. M. leprae, the causative agent of leprosy is an uncultivable organism in defined media, hence the biology and function of proteins were examined by cloning M. leprae genes in heterologous hosts. The study on sHsp18 was carried out as the knowledge about the functions of this major immunodominant antigen of M. leprae is scanty.

No abstract

Even though both cellular and humoral immunities contribute to host defense, the role played by humoral immunity against the airborne opportunistic fungal pathogen Aspergillus fumigatus has been underexplored. In this study, we aimed at deciphering the role of complement-system, the major humoral immune component, against A. fumigatus. Mass-spectrometric analysis of the proteins extracted from A. fumigatus conidial (asexual spores and infective propagules) surfaces opsonized with human serum indicated that C3 is the major complement protein involved. Flow cytometry and immunolabelling assays further confirmed C3b (activated C3) deposition on the conidial surfaces. Assays using cell wall components of conidia indicated that the hydrophobin RodAp, β-(1,3)-glucan (BG) and galactomannan (GM) could efficiently activate C3. Using complement component-depleted sera, we show that while RodAp activated C3 by the alternative pathway, BG and GM partially follow the classical and lectin pathways, respectively. Opsonization facilitated conidial aggregation and phagocytosis, and complement receptors (CR3 and CR4) blockage on phagocytes significantly inhibited phagocytosis, indicating that the complement-system exerts a protective role against conidia by opsonizing them and facilitating their phagocytosis mainly through complement receptors. Conidial opsonization with human bronchoalveolar lavage fluid (BALF) confirmed C3 to be the major complement protein interacting. Nevertheless, complement C2 and mannose binding lectin (MBL), the classical and lectin pathway components respectively, were not identified, indicating that BALF activates the alternative pathway on the conidial surface. Moreover, the cytokine profiles were different upon stimulation of phagocytes with serum or BALF opsonized conidia, highlighting the importance of studying the conidial interaction in their biological niche.

Department of Genetic Engineering, School of Biotechnology, Madurai Kamaraj University, Madurai, Tamil Nadu, IndiaThe aim of this study is to examine the in vivo role of a small heat-shock protein (sHsp18) from Mycobacterium leprae in the survival of heterologous recombinant hosts carrying the gene encoding this protein under different environmental conditions that are normally encountered by M. leprae during its infection of the human host. Using an Escherichia coli system where shsp18 expression is controlled by its native promoter, we show that expression of shsp18 is induced under low oxygen tension, nutrient depletion and oxidative stress, all of which reflect the natural internal environment of the granulomas where the pathogen resides for long periods. We demonstrate the in vivo chaperone activity of sHsp18 through its ability to confer survival advantage to recombinant E. coli at heat-shock temperatures. Additional evidence for the protective role of sHsp18 was obtained when Mycobacterium smegmatis harbouring a copy of shsp18 was found to multiply better in human macrophages. Furthermore, the autokinase activity of sHsp18 protein demonstrated for what is believed to be the first time in this study implies that some of the functions of sHsp18 might be controlled by the phosphorylation state of this protein.Results from this study suggest that shsp18 might be one of the factors that facilitate the survival and persistence of M. leprae under stress and autophosphorylation of sHsp18 protein could be a mechanism used by this protein to sense changes in the external environment. INTRODUCTIONMycobacterium leprae, the aetiological agent of leprosy, is known to persist in the host for a long period, and hence poses a major hurdle in eradicating leprosy. The incubation period of M. leprae can vary anywhere between 4 and 10 years (Noordeen, 1994). To achieve elimination and eradication of leprosy, sensitive diagnostic methods that can detect the active and persistent bacteria, as well as drugs that could eliminate both these populations, are needed.Many factors that contribute to the virulence and persistence of M. leprae are not well understood. It is important to characterize virulence factors that would advance our understanding on M. leprae pathogenesis. One potential virulence factor worth considering is a small heatshock protein, sHsp18. Young and his co-workers (Young et al., 1985) reported sHsp18 as one of the major immunogenic proteins of M. leprae. Studies on the immunological properties of sHsp18 show that this protein is a good stimulator of CD4 + T-cell response (Booth et al., 1988) and is probably involved in inducing protective immunity against M. leprae infection (Dockrell et al., 1989). Despite the evidence implying sHsp18 in a protective role and control of infection, there is evidence that suggests that shsp18 could be an important survival factor for M. leprae. Comparative analysis of the genome of M. leprae with that of Mycobacterium tuberculosis has revealed the loss of a large number of singl...