Analysis of a Genomic DNA Expression Library of Mycobacterium tuberculosis Using Tuberculosis Patient Sera: Evidence for Modulation of Host Immune Response

DNA obtained from a human sputum isolate of Mycobacterium tuberculosis, NTI-64719, which showed extensive dissemination in the guinea pig model resulting in a high score for virulence was used to construct an expression library in the lambda ZAP vector. The size of DNA inserts in the library ranged from 1 to 3 kb, and recombinants represented 60% of the total plaques obtained. When probed with pooled serum from chronically infected tuberculosis patients, the library yielded 176 recombinants with a range of signal intensities. Among these, 93 recombinants were classified into 12 groups on the basis of DNA hybridization experiments, The polypeptides synthesized by the recombinants were predominantly LacZ fusion proteins, Serum obtained from patients who were clinically diagnosed to be in the early phase of M. tuberculosis infection was used to probe the 176 recombinants obtained. interestingly, some recombinants that gave very strong signals in the original screen did not react with early-phase serum; conversely, others whose signals were extremely weak in the original screen gave very intense signals with serum from recently infected patients, This indicates the differential nature of either the expression of these antigens or the immune response elicited by them as a function of disease progression.

Structural basis for the function of anti-idiotypic antibody in immune memory

We had earlier proposed a hypothesis to explain the mechanism of perpetuation of immunological memory based on the operation of idiotypic network in the complete absence of antigen. Experimental evidences were provided for memory maintenance through anti-idiotypic antibody (Ab2) carrying the internal image of the antigen. In the present work, we describe a structural basis for such memory perpetuation by molecular modeling and structural analysis studies. A three-dimensional model of Ab2 was generated and the structure of the antigenic site on the hemagglutinin protein H of Rinderpest virus was modeled using the structural template of hemagglutinin protein of Measles virus. Our results show that a large portion of heavy chain containing the CDR regions of Ab2 resembles the domain of the hemagglutinin housing the epitope regions. The similarity demonstrates that an internal image of the H antigen is formed in Ab2, which provides a structural basis for functional mimicry demonstrated earlier. This work brings out the importance of the structural similarity between a domain of hemagglutinin protein to that of its corresponding Ab2. It provides evidence that Ab2 is indeed capable of functioning as surrogate antigen and provides support to earlier proposed relay hypothesis which has provided a mechanism for the maintenance of immunological memory.

Structural basis for the function of anti-idiotypic antibody in immune memory

We had earlier proposed a hypothesis to explain the mechanism of perpetuation of immunological memory based on the operation of idiotypic network in the complete absence of antigen. Experimental evidences were provided for memory maintenance through anti-idiotypic antibody (Ab(2)) carrying the internal image of the antigen. In the present work, we describe a structural basis for such memory perpetuation by molecular modeling and structural analysis studies. A three-dimensional model of Ab(2) was generated and the structure of the antigenic site on the hemagglutinin protein H of Rinderpest virus was modeled using the structural template of hemagglutinin protein of Measles virus. Our results show that a large portion of heavy chain containing the CDR regions of Ab(2) resembles the domain of the hemagglutinin housing the epitope regions. The similarity demonstrates that an internal image of the H antigen is formed in Ab(2), which provides a structural basis for functional mimicry demonstrated earlier. This work brings out the importance of the structural similarity between a domain of hemagglutinin protein to that of its corresponding Ab(2). It provides evidence that Ab(2) is indeed capable of functioning as surrogate antigen and provides support to earlier proposed relay hypothesis which has provided a mechanism for the maintenance of immunological memory.

Effect of the antitumor antibiotic chromomycin A3 on the humoral immune response in rats

Chromomycin A3 (250 mug/kg) suppressed the humoral immune response in rats against sheep erythrocytes when administered 48 h or later after antigenic stimulus. The antibiotic at this dose enhanced immunity when given along with or before antigen administration. The natural heterohemagglutinin levels in rabbits and guinea pigs were not affected by the antibiotic (10 mug/kg per day x 7).

Varied Immune Response to FVIII: Presence of Proteolytic Antibodies Directed to Factor VIII in Different Human Pathologies

The versatility of antibodies is demonstrated by the various functions that they mediate such as neutralization, agglutination, fixation of the complement and its activation, and activation of effector cells. In addition to this plethora of functions, antibodies are capable of expressing enzymatic activity. Antibodies with catalytic function are a result of the productive interplay between the highly evolved machinery of the immune system and the chemical framework used to induce them (antigens). Catalytic antibodies are immunoglobulins with an ability to catalyze the reactions involving the antigen for which they are specific. Catalytic immunoglobulins of the IgM and IgG isotypes have been detected in the serum of healthy donors. In addition, catalytic immunoglobulins of the IgA isotype have been detected in the milk of healthy mothers. Conversely, antigen-specific hydrolytic antibodies have been reported in a number of inflammatory, autoimmune, and neoplastic disorders. The pathophysiological occurrence and relevance of catalytic antibodies remains a debated issue. Through the description of the hydrolysis of coagulation factor VIII as model target antigen, we propose that catalytic antibodies directed to the coagulation factor VIII may play a beneficial or a deleterious role depending on the immuno-inflammatory condition under which they occur.

Enhancement of immune response by the proteinaceous crystal of Bacillus thuringiensis Var thuringiensis

The proteinaceous crystal of Bacillus thuringiensis Var thuringiensis was found to enhance humoral immune response in rats and guinea pigs immunised with sheep red blood cells. The enhancement was due to the increased levels of both 19S and 7S antibodies in the sera of the treated animals. A novel synthesis of 7S haemolytic antibodies was observed in case of crystal treated animals.

The role of glycodelin as an immune-modulating agent at the feto-maternal interface

Glycodelin A is a progesterone-induced endometrial glycoprotein which has been amply documented to play a role in down-modulation of the maternal immune response to fetal allo-antigens and to be indispensable for the maintenance and progression of pregnancy. Earlier studies from our laboratory have focused on the effect of glycodelin on T cells, key regulators of both the antibody and cell-mediated arms of the acquired immune system. Glycodelin-induced apoptosis inactivated T cells occurs through a caspase-dependant intrinsic mitochondrial pathway. Interestingly, glycodelin inhibited the proliferation of B cells but did not induce apoptosis. More recently, we have studied the effect of glycodelin on the cells of the innate immune system, namely monocytes and NK cells. We have found that glycodelin induced apoptosis in monocytic cells before their differentiation to macrophages, via the mitochondrial pathway, but did not affect their phagocytic capacity after differentiation. Glycodelin induced apoptosis in NK cells but this activity was independent of caspases. In conclusion, glycodelin is observed to affect many cells of the immune system, although the nature of the effect and signaling mechanisms involved in each cell type may be distinct.

Src Homology 3-interacting Domain of Rv1917c of Mycobacterium tuberculosis Induces Selective Maturation of Human Dendritic Cells by Regulating PI3K-MAPK-NF-kappa B Signaling and Drives Th2 Immune Responses

Mycobacterium tuberculosis, an etiological agent of pulmonary tuberculosis, causes significant morbidity and mortality worldwide. Pathogenic mycobacteria survive in the host by subverting host innate immunity. Dendritic cells (DCs) are professional antigen-presenting cells that are vital for eliciting immune responses to infectious agents, including pathogenic mycobacteria. DCs orchestrate distinct Th responses based on the signals they receive. In this perspective, deciphering the interactions of the proline-glutamic acid/proline-proline-glutamic acid (PE/PPE) family of proteins of M. tuberculosis with DCs assumes significant pathophysiological attributes. In this study, we demonstrate that Rv1917c (PPE34), a representative member of the proline-proline-glutamic-major polymorphic tandem repeat family, interacts with TLR2 and triggers functional maturation of human DCs. Signaling perturbations implicated a critical role for integrated cross-talk among PI3K-MAPK and NF-kappa B signaling cascades in Rv1917c-induced maturation of DCs. However, this maturation of DCs was associated with a secretion of high amounts of anti-inflammatory cytokine IL-10, whereas Th1-polarizing cytokine IL-12 was not induced. Consistent with these results, Rv1917c-matured DCs favored secretion of IL-4, IL-5, and IL-10 from CD4(+) T cells and contributed to Th2-skewed cytokine balance ex vivo in healthy individuals and in patients with pulmonary tuberculosis. Interestingly, the Rv1917c-skewed Th2 immune response involved induced expression of cyclooxygenase-2 (COX-2) in DCs. Taken together, these results indicate that Rv1917c facilitates a shift in the ensuing immunity toward the Th2 phenotype and could aid in immune evasion by mycobacteria.

Characterization and immune response of a protein produced by a cDNA clone of foot and mouth disease virus, type Asia 1 63/72

A 0.9 kb double stranded cDNA of foot and mouth disease virus (FMDV) Type Asia 1, 63/72 was cloned in an expression vector, pUR222. A protein of 38 kd was produced by the clone which reacted with the antibodies raised against the virus. A 20 kd protein which may be derived from the 38 kd protein contained the antigenic epitopes of the protein VP1 of the virus. Injection of 10-20 micrograms of the partially purified 38 and 20 kd proteins or a lysate of cells containing 240 micrograms of the proteins elicited high titers of FMDV specific antibodies in guinea pigs and cattle respectively. Also, at these concentrations, the proteins protected 5 of 8 guinea pigs and 3 of 8 cattle when challenged with a virulent virus.

Immune responses to hemagglutinin-neuraminidase protein of peste des petits ruminants virus expressed in transgenic peanut plants in sheep

Peste des petits ruminants (PPR) is an acute, highly contagious disease of small ruminants caused by a morbillivirus, Peste des petits ruminants virus (PPRV). The disease is prevalent in equatorial Africa, the Middle East, and the Indian subcontinent. A live attenuated vaccine is in use in some of the countries and has been shown to provide protection for at least three years against PPR. However, the live attenuated vaccine is not robust in terms of thermotolerance. As a step towards development of a heat stable subunit vaccine, we have expressed a hemagglutinin-neuraminidase (HN) protein of PPRV in peanut plants (Arachis hypogea) in a biologically active form, possessing neuraminidase activity. Importantly. HN protein expressed in peanut plants retained its immunodominant epitopes in their natural conformation. The immunogenicity of the plant derived HN protein was analyzed in sheep upon oral immunization. Virus neutralizing antibody responses were elicited upon oral immunization of sheep in the absence of any mucosal adjuvant. In addition, anti-PPRV-HN specific cell-mediated immune responses were also detected in mucosally immunized sheep. (C) 2010 Elsevier B.V. All rights reserved.

Pattern recognition and cellular immune responses to novel Mycobacterium tuberculosis-antigens in individuals from Belarus

Background: Tuberculosis (TB) is an enduring health problem worldwide and the emerging threat of multidrug resistant (MDR) TB and extensively drug resistant (XDR) TB is of particular concern. A better understanding of biomarkers associated with TB will aid to guide the development of better targets for TB diagnosis and for the development of improved TB vaccines. Methods: Recombinant proteins (n = 7) and peptide pools (n = 14) from M. tuberculosis (M.tb) antigens associated with M.tb pathogenicity, modification of cell lipids or cellular metabolism, were used to compare T cell immune responses defined by IFN-gamma production using a whole blood assay (WBA) from i) patients with TB, ii) individuals recovered from TB and iii) individuals exposed to TB without evidence of clinical TB infection from Minsk, Belarus. Results: We identified differences in M.tb target peptide recognition between the test groups, i.e. a frequent recognition of antigens associated with lipid metabolism, e.g. cyclopropane fatty acyl phospholipid synthase. The pattern of peptide recognition was broader in blood from healthy individuals and those recovered from TB as compared to individuals suffering from pulmonary TB. Detection of biologically relevant M.tb targets was confirmed by staining for intracellular cytokines (IL-2, TNF-alpha and IFN-gamma) in T cells from non-human primates (NHPs) after BCG vaccination. Conclusions: PBMCs from healthy individuals and those recovered from TB recognized a broader spectrum of M.tb antigens as compared to patients with TB. The nature of the pattern recognition of a broad panel of M.tb antigens will devise better strategies to identify improved diagnostics gauging previous exposure to M.tb; it may also guide the development of improved TB-vaccines.