Multi-OMICs analysis reveals metabolic and epigenetic changes associated with macrophage polarization.

Macrophages (MФ) are an essential immune cell for defense and repair that travel to different tissues and adapt based on local stimuli. A critical factor that may govern their polarization is the crosstalk between metabolism and epigenetics. However, simultaneous measurements of metabolites, epigenetics, and proteins (phenotype) have been a major technical challenge. To address this, we have developed a novel triomics approach using mass spectrometry to comprehensively analyze metabolites, proteins, and histone modifications in a single sample. To demonstrate this technique, we investigated the metabolic-epigenetic-phenotype axis following polarization of human blood-derived monocytes into either 'proinflammatory M1-' or 'anti-inflammatory M2-' MФs. We report here a complex relationship between arginine, tryptophan, glucose, and the citric acid cycle metabolism, protein and histone post-translational modifications, and human macrophage polarization that was previously not described. Surprisingly, M1-MФs had globally reduced histone acetylation levels but high levels of acetylated amino acids. This suggests acetyl-CoA was diverted, in part, toward acetylated amino acids. Consistent with this, stable isotope tracing of glucose revealed reduced usage of acetyl-CoA for histone acetylation in M1-MФs. Furthermore, isotope tracing also revealed MФs uncoupled glycolysis from the tricarboxylic acid cycle, as evidenced by poor isotope enrichment of succinate. M2-MФs had high levels of kynurenine and serotonin, which are reported to have immune-suppressive effects. Kynurenine is upstream of de novo NAD+ metabolism that is a necessary cofactor for Sirtuin-type histone deacetylases. Taken together, we demonstrate a complex interplay between metabolism and epigenetics that may ultimately influence cell phenotype.

A unique PE_PGRS protein inhibiting host cell cytosolic defenses and sustaining full virulence of Mycobacterium marinum in multiple hosts.

Despite intense research, PE_PGRS proteins still represent an intriguing aspect of mycobacterial pathogenesis. These cell surface proteins influence virulence in several pathogenic species, but their diverse and exact functions remain unclear. Herein, we focussed on a PE_PGRS member from Mycobacterium marinum, MMAR_0242, characterized by an extended and unique C-terminal domain. We demonstrate that an M. marinum mutant carrying a transposon insertion in MMAR_0242 is highly impaired in its ability to replicate in macrophages and amoebae, because of its inability to inhibit lysosomal fusion. As a consequence, this mutant failed to survive intracellularly as evidenced by a reduced number of cytosolic actin tail-forming bacteria and by quantitative electron microscopy, which mainly localized MMAR_0242::Tn within membrane-defined vacuoles. Functional complementation studies indicated that the C-terminus, but not the N-terminal PE_PGRS domain, is required for intracellular growth/survival. In line with these findings, disruption of MMAR_0242 resulted in a highly attenuated virulence phenotype in zebrafish embryos, characterized by restricted bacterial loads and a failure to produce granulomas. Furthermore, expression of MMAR_0242 in Mycobacterium smegmatis, a non-pathogenic species naturally deficient in PE_PGRS production, resulted in increased survival in amoebae with enhanced cytotoxic cell death and increased survival in infected mice with splenomegaly. Overall, these results indicate that MMAR_0242 is required for full virulence of M. marinum and sufficient to confer pathogenic properties to M. smegmatis.

A new dehydratase conferring innate resistance to thiacetazone and intra-amoebal survival of Mycobacterium smegmatis.

Nontuberculous mycobacteria are innately resistant to most antibiotics, although the mechanisms responsible for their drug resistance remain poorly understood. They are particularly refractory to thiacetazone (TAC), a second-line antitubercular drug. Herein, we identified MSMEG_6754 as essential for the innate resistance of Mycobacterium smegmatis to TAC. Transposon-mediated and targeted disruption of MSMEG_6754 resulted in hypersusceptibility to TAC. Conversely, introduction of MSMEG_6754 into Mycobacterium tuberculosis increased resistance 100-fold. Resolution of the crystal structure of MSMEG_6754 revealed a homodimer in which each monomer comprises two hot-dog domains characteristic of dehydratase-like proteins and very similar to the HadAB complex involved in mycolic acid biosynthesis. Gene inactivation of the essential hadB dehydratase could be achieved in M. smegmatis and M. tuberculosis only when the strains carried an integrated copy of MSMEG_6754, supporting the idea that MSMEG_6754 and HadB share redundant dehydratase activity. Using M. smegmatis-Acanthamoeba co-cultures, we found that intra-amoebal growth of the MSMEG_6754 deleted strain was significantly reduced compared with the parental strain. This in vivo growth defect was fully restored upon complementation with catalytically active MSMEG_6754 or HadABC, indicating that MSMEG_6754 plays a critical role in the survival of M. smegmatis within the environmental host.

Increased phagocytosis of Mycobacterium marinum mutants defective in lipooligosaccharide production: a structure-activity relationship study.

Mycobacterium marinum is a waterborne pathogen responsible for tuberculosis-like infections in ectotherms and is an occasional opportunistic human pathogen. In the environment, M. marinum also interacts with amoebae, which may serve as a natural reservoir for this microorganism. However, the description of mycobacterial determinants in the early interaction with macrophages or amoebae remains elusive. Lipooligosaccharides (LOSs) are cell surface-exposed glycolipids capable of modulating the host immune system, suggesting that they may be involved in the early interactions of M. marinum with macrophages. Herein, we addressed whether LOS composition affects the uptake of M. marinum by professional phagocytes. Mutants with various truncated LOS variants were generated, leading to the identification of several previously uncharacterized biosynthetic genes (wbbL2, MMAR_2321, and MMAR_2331). Biochemical and structural approaches allowed resolving the structures of LOS precursors accumulating in this set of mutants. These strains with structurally defined LOS profiles were then used to infect both macrophages and Acanthamoebae. An inverse correlation between LOS completeness and uptake of mycobacteria by phagocytes was found, allowing the proposal of three mutant classes: class I (papA4), devoid of LOS and highly efficiently phagocytosed; class II, accumulating only early LOS intermediates (wbbL2 and MMAR_2331) and efficiently phagocytosed but less than class I mutants; class III, lacking LOS-IV (losA, MMAR_2319, and MMAR_2321) and phagocytosed similarly to the control strain. These results indicate that phagocytosis is conditioned by the LOS pattern and that the LOS pathway used by M. marinum in macrophages is conserved during infection of amoebae.

Sirtuin-dependent metabolic and epigenetic regulation of macrophages during tuberculosis.

Macrophages are the preeminent phagocytic cells which control multiple infections. Tuberculosis a leading cause of death in mankind and the causative organism Mycobacterium tuberculosis (MTB) infects and persists in macrophages. Macrophages use reactive oxygen and nitrogen species (ROS/RNS) and autophagy to kill and degrade microbes including MTB. Glucose metabolism regulates the macrophage-mediated antimicrobial mechanisms. Whereas glucose is essential for the growth of cells in immune cells, glucose metabolism and its downsteam metabolic pathways generate key mediators which are essential co-substrates for post-translational modifications of histone proteins, which in turn, epigenetically regulate gene expression. Herein, we describe the role of sirtuins which are NAD+-dependent histone histone/protein deacetylases during the epigenetic regulation of autophagy, the production of ROS/RNS, acetyl-CoA, NAD+, and S-adenosine methionine (SAM), and illustrate the cross-talk between immunometabolism and epigenetics on macrophage activation. We highlight sirtuins as emerging therapeutic targets for modifying immunometabolism to alter macrophage phenotype and antimicrobial function.

CD44 receptor targeted nanoparticles augment immunity against tuberculosis in mice.

We describe a role of CD44-mediated signaling during host-defense against tuberculosis (TB) using a mouse model of TB and studies in M. tuberculosis (Mtb) infected human macrophage (MФ). Liposomes targeting CD44 using thioaptamers (CD44TA-LIP) were designed and tested as new vaccines to boost host immunity in TB. CD44TA-LIP enhanced killing of Mtb in human MФ, which correlated with an increased production of pro-inflammatory cytokines IL-1ß, TNF-α and IL-12. CD44TA-LIP activated MФ showed an enhanced MHC-II dependent antigen presentation to CD4 T-cells. Inhibition of cellular proliferation and cytoskeleton rearrangement pathways downstream of CD44 signaling abrogated CD44TA-LIP-induced antimicrobial effects. Blockade of inflammatory pathways also reduced antigen presentation by MФ and activation of CD4 T cells. Mtb infected MФ treated with CD44TA-LIP exhibited increased nitric oxide and HßD2 defensin peptide production. Among Mtb infected mice with increased lung and spleen loads of organisms, intranasal administration of CD44TA-LIP led to a ten-fold reduction of colony forming units of Mtb and elevated IFN-γ + CD4, effector, central and resident memory T cells. Biodistribution studies demonstrated that CD44TA-LIP preferentially accumulated in the lungs and were associated with CD11b + cells. CD44TA-LIP treated mice showed no weight loss or increased liver LDH levels. This study highlights the importance of CD44-mediated signaling in host-defense during TB and the therapeutic potential of CD44TA-LIP.

Human Macrophages Exhibit GM-CSF Dependent Restriction of Mycobacterium tuberculosis Infection via Regulating Their Self-Survival, Differentiation and Metabolism.

GM-CSF is an important cytokine that regulates the proliferation of monocytes/macrophages and its various functions during health and disease. Although growing evidences support the notion that GM-CSF could play a major role in immunity against tuberculosis (TB) infection, the mechanism of GM-CSF mediated protective effect against TB remains largely unknown. Here in this study we examined the secreted levels of GM-CSF by human macrophages from different donors along with the GM-CSF dependent cellular processes that are critical for control of M. tuberculosis infection. While macrophage of different donors varied in their ability to produce GM-CSF, a significant correlation was observed between secreted levels of GM-CSF, survial of macrophages and intra-macrophage control of Mycobacterium tuberculosis bacilli. GM-CSF levels secreted by macrophages negatively correlated with the intra-macrophage M. tuberculosis burden, survival of infected host macrophages positively correlated with their GM-CSF levels. GM-CSF-dependent prolonged survival of human macrophages also correlated with significantly decreased bacterial burden and increased expression of self-renewal/cell-survival associated genes such as BCL-2 and HSP27. Antibody-mediated depletion of GM-CSF in macrophages resulted in induction of significantly elevated levels of apoptotic/necrotic cell death and a simultaneous decrease in autophagic flux. Additionally, protective macrophages against M. tuberculosis that produced more GM-CSF, induced a stronger granulomatous response and produced significantly increased levels of IL-1ß, IL-12 and IL-10 and decreased levels of TNF-α and IL-6. In parallel, macrophages isolated from the peripheral blood of active TB patients exhibited reduced capacity to control the intracellular growth of M. tuberculosis and produced significantly lower levels of GM-CSF. Remarkably, as compared to healthy controls, macrophages of active TB patients exhibited significantly altered metabolic state correlating with their GM-CSF secretion levels. Altogether, these results suggest that relative levels of GM-CSF produced by human macrophages plays a critical role in preventing cell death and maintaining a protective differentiation and metabolic state of the host cell against M. tuberculosis infection.

Antibody-Mediated LILRB2-Receptor Antagonism Induces Human Myeloid-Derived Suppressor Cells to Kill Mycobacterium tuberculosis.

Tuberculosis is a leading cause of death in mankind due to infectious agents, and Mycobacterium tuberculosis (Mtb) infects and survives in macrophages (MФs). Although MФs are a major niche, myeloid-derived suppressor cells (MDSCs) are an alternative site for pathogen persistence. Both MФs and MDSCs express varying levels of leukocyte immunoglobulin-like receptor B (LILRB), which regulate the myeloid cell suppressive function. Herein, we demonstrate that antagonism of LILRB2 by a monoclonal antibody (mab) induced a switch of human MDSCs towards an M1-macrophage phenotype, increasing the killing of intracellular Mtb. Mab-mediated antagonism of LILRB2 alone and its combination with a pharmacological blockade of SHP1/2 phosphatase increased proinflammatory cytokine responses and phosphorylation of ERK1/2, p38 MAPK, and NF-kB in Mtb-infected MDSCs. LILRB2 antagonism also upregulated anti-mycobacterial iNOS gene expression and an increase in both nitric oxide and reactive oxygen species synthesis. Because genes associated with the anti-mycobacterial function of M1-MФs were enhanced in MDSCs following mab treatment, we propose that LILRB2 antagonism reprograms MDSCs from an immunosuppressive state towards a pro-inflammatory phenotype that kills Mtb. LILRB2 is therefore a novel therapeutic target for eradicating Mtb in MDSCs.

Human M1 macrophages express unique innate immune response genes after mycobacterial infection to defend against tuberculosis.

Mycobacterium tuberculosis (Mtb) is responsible for approximately 1.5 million deaths each year. Though 10% of patients develop tuberculosis (TB) after infection, 90% of these infections are latent. Further, mice are nearly uniformly susceptible to Mtb but their M1-polarized macrophages (M1-MΦs) can inhibit Mtb in vitro, suggesting that M1-MΦs may be able to regulate anti-TB immunity. We sought to determine whether human MΦ heterogeneity contributes to TB immunity. Here we show that IFN-γ-programmed M1-MΦs degrade Mtb through increased expression of innate immunity regulatory genes (Inregs). In contrast, IL-4-programmed M2-polarized MΦs (M2-MΦs) are permissive for Mtb proliferation and exhibit reduced Inregs expression. M1-MΦs and M2-MΦs express pro- and anti-inflammatory cytokine-chemokines, respectively, and M1-MΦs show nitric oxide and autophagy-dependent degradation of Mtb, leading to increased antigen presentation to T cells through an ATG-RAB7-cathepsin pathway. Despite Mtb infection, M1-MΦs show increased histone acetylation at the ATG5 promoter and pro-autophagy phenotypes, while increased histone deacetylases lead to decreased autophagy in M2-MΦs. Finally, Mtb-infected neonatal macaques express human Inregs in their lymph nodes and macrophages, suggesting that M1 and M2 phenotypes can mediate immunity to TB in both humans and macaques. We conclude that human MФ subsets show unique patterns of gene expression that enable differential control of TB after infection. These genes could serve as targets for diagnosis and immunotherapy of TB.

Human monocyte-derived macrophage responses to M. tuberculosis differ by the host's tuberculosis, diabetes or obesity status, and are enhanced by rapamycin.

Human macrophages play a major role in controlling tuberculosis (TB), but their anti-mycobacterial mechanisms remain unclear among individuals with metabolic alterations like obesity (TB protective) or diabetes (TB risk). To help discern this, we aimed to: i) Evaluate the impact of the host's TB status or their comorbidities on the anti-mycobacterial responses of their monocyte-derived macrophages (MDMs), and ii) determine if the autophagy inducer rapamycin, can enhance these responses. We used MDMs from newly diagnosed TB patients, their close contacts and unexposed controls. The MDMs from TB patients had a reduced capacity to activate T cells (surrogate for antigen presentation) or kill M. tuberculosis (Mtb) when compared to non-TB controls. The MDMs from obese participants had a higher antigen presenting capacity, whereas those from chronic diabetes patients displayed lower Mtb killing. The activation of MDMs with rapamycin led to an enhanced anti-mycobacterial activity irrespective of TB status but was not as effective in patients with diabetes. Further studies are warranted using MDMs from TB patients with or without metabolic comorbidities to: i) elucidate the mechanisms through which host factors affect Mtb responses, and ii) evaluate host directed therapy using autophagy-inducing drugs like rapamycin to enhance macrophage function.

A recombinant bovine adenoviral mucosal vaccine expressing mycobacterial antigen-85B generates robust protection against tuberculosis in mice.

Although the BCG vaccine offers partial protection, tuberculosis remains a leading cause of infectious disease death, killing ∼1.5 million people annually. We developed mucosal vaccines expressing the autophagy-inducing peptide C5 and mycobacterial Ag85B-p25 epitope using replication-defective human adenovirus (HAdv85C5) and bovine adenovirus (BAdv85C5) vectors. BAdv85C5-infected dendritic cells (DCs) expressed a robust transcriptome of genes regulating antigen processing compared to HAdv85C5-infected DCs. BAdv85C5-infected DCs showed enhanced galectin-3/8 and autophagy-dependent in vitro Ag85B-p25 epitope presentation to CD4 T cells. BCG-vaccinated mice were intranasally boosted using HAdv85C5 or BAdv85C5 followed by infection using aerosolized Mycobacterium tuberculosis (Mtb). BAdv85C5 protected mice against tuberculosis both as a booster after BCG vaccine (>1.4-log10 reduction in Mtb lung burden) and as a single intranasal dose (>0.5-log10 reduction). Protection was associated with robust CD4 and CD8 effector (TEM), central memory (TCM), and CD103+/CD69+ lung-resident memory (TRM) T cell expansion, revealing BAdv85C5 as a promising mucosal vaccine for tuberculosis.

Human mesenchymal stem cell based intracellular dormancy model of Mycobacterium tuberculosis.

Understanding the biology of the tuberculosis pathogen during dormant asymptomatic infection, called latent tuberculosis is crucial to decipher a resilient therapeutic strategy for the disease. Recent discoveries exhibiting presence of pathogen's DNA and bacilli in mesenchymal stem cells (MSCs) of human and mouse despite completion of antitubercular therapy, indicates that these specific cells could be one of the niches for dormant Mycobacterium tuberculosis in humans. To determine if in vitro infection of human MSCs could recapitulate the in vivo characteristics of dormant M. tuberculosis, we examined survival, phenotype, and drug susceptibility of the pathogen in MSCs. When a very low multiplicity of infection (1:1) was used, M. tuberculosis could survive in human bone marrow derived MSCs for more than 22 days without any growth. At this low level of infection, the pathogen did not cause any noticeable host cell death. During the later phase of infection, MSC-residing M. tuberculosis exhibited increased expression of HspX (a 16-kDa alpha-crystallin homolog) with a concurrent increase in tolerance to the frontline antitubercular drugs Rifampin and isoniazid. These results present a human MSC-based intracelllular model of M. tuberculosis infection to dissect the mechanisms through which the pathogen acquires and maintains dormancy in the host.

Emerging Prevention and Treatment Strategies to Control COVID-19.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has now become a serious global threat after inflicting more than 8 million infections and 425,000 deaths in less than 6 months. Currently, no definitive treatment or prevention therapy exists for COVID-19. The unprecedented rise of this pandemic has rapidly fueled research efforts to discover and develop new vaccines and treatment strategies against this novel coronavirus. While hundreds of vaccines/therapeutics are still in the preclinical or early stage of clinical development, a few of them have shown promising results in controlling the infection. Here, in this review, we discuss the promising vaccines and treatment options for COVID-19, their challenges, and potential alternative strategies.

NOD2/RIG-I Activating Inarigivir Adjuvant Enhances the Efficacy of BCG Vaccine Against Tuberculosis in Mice.

Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) kills about 1.5 million people each year and the widely used Bacille Calmette-Guérin (BCG) vaccine provides a partial protection against TB in children and adults. Because BCG vaccine evades lysosomal fusion in antigen presenting cells (APCs), leading to an inefficient production of peptides and antigen presentation required to activate CD4 T cells, we sought to boost its efficacy using novel agonists of RIG-I and NOD2 as adjuvants. We recently reported that the dinucleotide SB 9200 (Inarigivir) derived from our small molecule nucleic acid hybrid (SMNH)® platform, activated RIG-I and NOD2 receptors and exhibited a broad-spectrum antiviral activity against hepatitis B and C, Norovirus, RSV, influenza and parainfluenza. Inarigivir increased the ability of BCG-infected mouse APCs to secrete elevated levels of IL-12, TNF-α, and IFN-ß, and Caspase-1 dependent IL-1ß cytokine. Inarigivir also increased the ability of macrophages to kill MTB in a Caspase-1-, and autophagy-dependent manner. Furthermore, Inarigivir led to a Capsase-1 and NOD2- dependent increase in the ability of BCG-infected APCs to present an Ag85B-p25 epitope to CD4 T cells in vitro. Consistent with an increase in immunogenicity of adjuvant treated APCs, the Inarigivir-BCG vaccine combination induced robust protection against tuberculosis in a mouse model of MTB infection, decreasing the lung burden of MTB by 1-log10 more than that afforded by BCG vaccine alone. The Inarigivir-BCG combination was also more efficacious than a muramyl-dipeptide-BCG vaccine combination against tuberculosis in mice, generating better memory T cell responses supporting its novel adjuvant potential for the BCG vaccine.

Human natural killer cells mediate adaptive immunity to viral antigens.

Adaptive immune responses are defined as antigen sensitization-dependent and antigen-specific responses leading to establishment of long-lived immunological memory. Although natural killer (NK) cells have traditionally been considered cells of the innate immune system, mounting evidence in mice and nonhuman primates warrants reconsideration of the existing paradigm that B and T cells are the sole mediators of adaptive immunity. However, it is currently unknown whether human NK cells can exhibit adaptive immune responses. We therefore tested whether human NK cells mediate adaptive immunity to virally encoded antigens using humanized mice and human volunteers. We found that human NK cells displayed vaccination-dependent, antigen-specific recall responses in vitro, when isolated from livers of humanized mice previously vaccinated with HIV-encoded envelope protein. Furthermore, we discovered that large numbers of cytotoxic NK cells with a tissue-resident phenotype were recruited to sites of varicella-zoster virus (VZV) skin test antigen challenge in VZV-experienced human volunteers. These NK-mediated recall responses in humans occurred decades after initial VZV exposure, demonstrating that NK memory in humans is long-lived. Our data demonstrate that human NK cells exhibit adaptive immune responses upon vaccination or infection. The existence of human memory NK cells may allow for the development of vaccination-based approaches capable of establishing potent NK-mediated memory functions contributing to host protection.

Blood levels of polycyclic aromatic hydrocarbons in children and their association with oxidative stress indices: an Indian perspective.

BACKGROUND: Polycyclic aromatic hydrocarbons (PAHs), some ubiquitous environmental contaminants are capable to cause oxidative stress, during its metabolism. It is believed that many diseases that have a common origin in oxidative stress begin in childhood. Considering oxidative stress evolved during PAHs metabolism as one main mechanism responsible for health hazards related to PAHs exposure in children, we biomonitored blood PAHs levels in connection with redox status among children of Lucknow (India). METHODS: The study consisted of children (n = 50) who visited to the Pediatrics Department (KGMU) Lucknow for usual health check-up camp over the study period (August 2005-July 2006). Blood samples were drawn and levels of acenaphthylene, anthracene, phenanthrene, fluoranthene, naphthalene, pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene and benzo(a)pyrene were determined by HPLC-FD/UV. Malondialdehyde (MDA), glutathione (GSH) levels, catalase (CAT) and superoxide dismutase (SOD) activity were also determined to evaluate redox status. RESULTS: Significantly elevated carcinogenic blood PAHs levels (125.55 +/- 26.99ppb, p < 0.05) were found in rural children compared to children from urban region (23.96 +/- 13.46). Results revealed that remoteness between residence and highway/traffic, significantly influences the blood levels of carcinogenic PAHs. There were significant correlations between total PAHs and MDA (r = 0.82, p < 0.001), carcinogenic PAHs and SOD activity (r = 0.35, p < 0.01), Total PAHs and blood GSH level (r = - 0.49, p < 0.01) and carcinogenic PAHs and CAT activity (r = 0.42, p < 0.01). Blood MDA level was also found correlated with increasing body mass index (BMI) (r = 0.29, p < 0.05). CONCLUSION: Our results showed blood PAHs levels in children significantly correlated with oxidative stress and altered antioxidant status. It supports our hypothesis that the children exposed to high PAHs level will suffer more to oxidative stress that may lead to possible health risks. Additional studies with large sample size are considered necessary to strengthen the database and also to explore the PAHs associated health risks in children.

Biomonitoring of organochlorines, glutathione, lipid peroxidation and cholinesterase activity among pesticide sprayers in mango orchards.

BACKGROUND: Pesticide sprayers in mango orchards of Malihabad, Lucknow (India) are generally exposed to organophosphate (OP) and pyrethroid pesticides. We determined the pesticide exposure levels along with their biochemical and clinical effects in 31 sprayers, compared with 18 controls. METHODS: Assay of acetyl and butyrylcholinesterases (AChE, BChE respectively) as an indirect measurement of OP exposure and levels of malondialdehyde (MDA) and glutathione (GSH) were estimated in blood samples to determine their impact on redox potential. Organochlorines were estimated by GLC-ECD. RESULTS: Significantly inhibited AChE, BChE activities and higher MDA level were found among sprayers compared to controls (p<0.05). Mean of total organochlorines were surprisingly higher (97.65+/-13.38 ppb) in sprayers than in those of controls (20.42+/-3.56 ppb) (p<0.05). Respiratory morbidity (32.4%), ocular problems (8.8%), gastrointestinal (17.6%) and skin problems (23.5%) were found in sprayers. There was significant correlation between AChE and GSH (r=0.29, p<0.05) and AChE with MDA (r=-0.34, p<0.05). CONCLUSION: Results indicated the significantly enhanced lipid peroxidation in sprayers correlated with cholinesterases inhibition. A small sample size limits the significance of this study. However, it paves the way for a larger Indian study with extended practical significance.

Increased virulence of Mycobacterium tuberculosis H37Rv overexpressing LipY in a murine model.

We have investigated the role of Rv3097c-encoded lipase (LipY) on the virulence of Mycobacterium tuberculosis. It has been shown that the overexpression of LipY in strain H37Rv induced increase in virulence of recombinant H37Rv::LipY strain. Compared to H37Rv, infection with H37Rv::LipY caused enhanced mortality, weight loss, bacterial load in lungs, splenomegaly, worsening lung morphology and pathology. Mice immunized with recombinant LipY antigen were protected against challenge with H37Rv::LipY, which correlated with enhanced survival of challenged mice and striking decrease in pathological features observed in unimmunized mice. To probe the cause of increase in virulence of H37Rv::LipY, the immune status of the host infected with H37Rv and H37Rv::LipY was compared. It was found that overexpression of LipY compromised immune responses resulting in attenuation of Th1 and Th17 responses, significant increase in IL-10, decrease in number of macrophages and T cells, and increase in numbers of Treg, and DCs in the lungs whereas in mice immunized with LipY an increased pool of T cells and DCs was observed. This led us to conclude that the increase in the virulence of H37Rv::LipY was due to downregulation of the host's protective immunity and the Rv3097c encoded LipY lipase is a virulence factor of M. tuberculosis.

Overexpression of Rv3097c in Mycobacterium bovis BCG abolished the efficacy of BCG vaccine to protect against Mycobacterium tuberculosis infection in mice.

Rv3097c of Mycobacterium tuberculosis encoding lipase (LipY) was overexpressed in Mycobacterium bovis BCG. Efficacy of recombinant BCG to protect against infection of M. tuberculosis was evaluated in mice. Whereas the parent BCG vaccine protected the mice against infection, recombinant BCG overexpressing LipY offered no protection as judged by viable counts of tubercule bacilli in lungs, weight of infected mice, pathology of lungs and survival of challenged mice. Downregulation of overexpression of LipY by antisense approach considerably restored protection of infected mice as observed with parent BCG vaccine. Overexpression of lipase in BCG caused extensive hydrolysis of triacylglycerol (TG) as identified by TLC, HPLC and NMR spectroscopy. A good correlation could be inferred between hydrolysis of TG and decrease in Th1 secreted IFNγ and IL-2, proinflammatory cytokines and survival of infected mice. Mice immunized with purified LipY antigen were protected and both proinflammatory and Th1 specific cytokines were augmented. TG was found to be a poor vaccine providing no protection, which appears to be due to attenuation of Th1 and proinflammatory immune responses. In conclusion this is the first experimental report to show that immunogenicity of BCG vaccine was impaired by LipY-induced hydrolysis of specific lipids leading to suppression of host immune responses.