Bioaccumulation of mercury in marine bacteria: A novel approach of mercury remediation

Most of the environmental bacteria that are continuously exposed to mercury present in soil and sediments of lakes and rivers might adopt the heavy metal genotype to sustain in the toxic environment. The most widely studied genetic mechanism of mercury involves mer operon mediated mechanism. mer operon present in mercury resistant bacteria harbours certain functional genes like merA, merB, merT, merP etc. merB codes for organ mercurial lyase which cleaves the C-Hg bond in organo mercurial compounds which is subsequently converted to non toxic metallic mercury by mercuric ion reductase encoded by merA gene. In the present study, for the first time an attempt has been made to understand the non mer mediated mercury resistance mechanism in potent marine bacterial isolates and their role in bioremediation of mercury contamination in the environment. Ten strains from four different sites of Odisha coast showing minimum inhibitory concentration of 25-50 ppm were isolated, which were further studied in order to deduce non mer mediated mercury resistance mechanism. The potent mercury resistant isolates when grown under mercury stress were studied to understand bioaccumulation and thus their role in mercury bioremediation in the environment. From the above results it was concluded that marine bacteria play a significant role in detoxification of mercury in the environment either by reducing it to non toxic or by accumulating it inside their cells and therefore they are a key regulator in reducing the environmental pollution

IL-22: An Underestimated Player in Natural Resistance to Tuberculosis?

Approximately 10% of individuals latently infected with Mycobacterium tuberculosis (Mtb) develop active tuberculosis (TB) during their lifetime. Although it is well recognized that T-helper 1 immune responses are crucial for containing latent TB infection, the full array of host factors conferring protective immunity from TB progression are not completely understood. IL-22 is produced by cells of the innate and adaptive immune system including innate lymphoid cells, and natural killer cells as well as T lymphocytes (Th1, Th17, and Th22) and binds to its cognate receptor, the IL-22R1, which is expressed on non-hematopoietic cells such as lung epithelial cells. However, recent studies suggest that Mtb induces expression of the IL-22R1 on infected macrophages and multiple studies have indicated a protective role of IL-22 in respiratory tract infections. Reduced concentrations of circulating IL-22 in active TB compared to latent TB and decreased percentages of Mtb-specific IL-22 producing T cells in TB patients compared to controls designate this cytokine as a key player in TB immunology. More recently, it has been shown that in type 2 diabetes (T2D) and TB co-morbidity serum IL-22 concentrations are further reduced compared to TB patients without co-morbidities. However, whether a causative link between low IL-22 and increased susceptibility to TB and disease severity of TB exists remains to be established. This review summarizes the contribution of IL-22, a potentially under-appreciated key player in natural resistance to TB, at the interface between the immune response to Mtb and the lung epithelium

Genome Plasticity in Cultured Leishmania donovani: Comparison of Early and Late Passages

Leishmania donovani possesses a complex heteroxenic life cycle where infective metacyclic promastigotes are pre-adapted to infect their host and cope up with intracellular stress. Exploiting the similarities between cultured and sandfly derived promastigotes, we used early and late passage cultured promastigotes to show specific changes at genome level which compromise pathogen fitness reflected in gene expression and infection studies. The pathogen loses virulence mostly via transcriptional and translational regulations and long-time cultivation makes them struggle to convert to virulent metacyclics. At the genomic level very subtle plasticity was observed between the early and the late passages mostly in defense-related, nutrient acquisition and signal transduction genes. Chromosome Copy number variation is seen in the early and late passages involving several genes that may be playing a role in pathogenicity. Our study highlights the importance of ABC transporters and calpain like cysteine proteases in parasite virulence in cultured promastigotes. Interestingly, these proteins are emerging as important patho-adaptive factors in clinical isolates of Leishmania. We found that the currently available genome of Leishmania in the NCBI database are from late passages. Our early passage genome can act as a reference for future studies on virulent isolates of Leishmania. The annotated leads from this study can be used for virulence surveillance and therapeutic studies in the Indian subcontinent

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

Global gene expression profiling of myeloid immune cell subsets in response to in vitro challenge with porcine circovirus 2b

Compelling evidence suggests that the early interaction between porcine circovirus 2 (PCV-2) and the innate immune system is the key event in the pathogenesis of Post-Weaning Multisystemic Wasting Syndrome (PMWS). Furthermore, PCV2 has been detected in bone-marrow samples, potentially enabling an easy spread and reservoir for the virus. To assess the gene-expression differences induced by an in-vitro PCV2b infection in different three different myeloid innate immune cell subsets generated from the same animal, we used the Agilent Porcine Gene Expression Microarray (V2). Alveolar macrophages (AMØs), monocyte-derived dendritic cells (MoDCs) and bone-marrow cells (BMCs) were generated from each animal, and challenged with a UK-isolate of a PCV2 genotype b-strain at a MOI of 0.5. Remarkably, analysis showed a highly distinct and cell-type dependent response to PCV2b challenge. Overall, MoDCs showed the most marked response to PCV2b challenge in vitro and revealed a key role for TNF in the interaction with PCV2b, whereas only few genes were affected in BMCs and AMØs. These observations were further supported by an enrichment of genes in the downstream NF-κB Signalling pathway as well as an up regulation of genes with pro-apoptotic functions post-challenge. PCV2b challenge increases the expression of a large number of immune-related and pro-apoptotic genes mainly in MoDC, which possibly explain the increased inflammation, granulomatous inflammation and lymphocyte depletion seen in PMWS-affected pigs

Proteomic and Genomic Analysis of Leishmania donovani Parasites for their Survival in Mammalian Host and Designing Therapeutic Strategies to Combat the Disease

Visceral leishmaniasis (VL) is an immunosuppressive disease which is fatal if left untreated. Non-availability of vaccine, invasive methods of diagnosis and limitations of currently available therapies further complicate the problem. Designing effective therapies need detailed understanding of both parasite and host factors responsible for infection. Leishmania secrete virulence factors which modulate host immunity for their survival. We observed loss of virulence in Leishmania donovani promastigotes as a result of continuous axenic cultivation, resulting in differential modulation of macrophage microbicidal activity in vitro and higher immunostimulation in animals. Comparative proteomic screening of L. donovani AG83 promastigotes of early and late passages identified decrease in expression of some important virulence factors viz., gp63, HSP70, LACK, EF1-, dihydrolipoamide acetyltransferase, etc. providing the basis for loss of virulence. Post-transcriptional and post-translational modifications determine the ultimate protein repertoire in Leishmania. We generated RNA-Seq data to compare the transcript abundance in early (2nd), intermediate (11th), and late (25th) passages, and found altered metabolism, signaling, DNA repair and RNA editing processes which may account for the gross changes in protein expression when grown for longer periods in culture. We could cite similarity of parasite multiplication and dissemination with cancer cell division and metastasis in terms of gene expression pattern. Thus we propose that common pathway or target based clinical interventions can be designed for VL and cancer. Based on our understanding of the parasite and host factors of VL we did mechanistic study on previously developed cationic drug free and pentavalent antimonial (SbV) entrapped phosphatidylcholine (PC) - stearylamine (SA) liposomes and compared their efficacy with PC-dioctadecyldimethylammonium bromide (DDAB) vesicles. We observed increased retention and slow release of liposomal drug responsible for resistance reversal and phosphatidylserine-mediated direct leishmanicidal activity in vitro and host-protective immomodulation for effective therapy in vivo, with PC-DDAB being a better antileishmanial requiring a 4-times less dose for equivalent activity. To further improve this formulation we entrapped TGF-β signaling inhibitor SB-505124 (SB), earlier used in cancer therapy, in PC-SA and encapsulated globally used form of SbV, meglumine antimoniate (MA) into it (PC-SA-SB-MA). After successful in vitro screening we observed near sterile cure in a mice model of infection with a dose of 10 mg/kg b.w. w.r.t. PC of PC-SA entrapping 50mg/kg b.w of SB and encapsulating 6 mg/kg b.w. of MA, whereas 20 mg/kg b.w of only PC-SA-MA was inferior in clearing parasites from liver, spleen and bone marrow of infected mice. Clearance of parasites was accompanied with higher IFN-/IL-10 ratio for successful cure. Thus our liposomal formulations can act as dual modulators of parasite and host. To conclude, similarities between VL and cancer can be exploited in identifying drug and vaccine targets and designing common clinical interventions for these diseases

Pre-adaptation of Leishmania promastigotes to intracellular life: ensuring a successful infection

Leishmaniasis is a group of diseases with diverse phenotype from self-healing cutaneous lesions to fatal visceral infections. The complex life-cycle of the parasite Leishmania in its vector and host as well as the vector and host characteristics determine the severity of infection. Leishmania has evolved several strategies to survive as extracellular promastigotes in the sandfly vector and successfully transform to amastigotes sensing an increase in temperature and acidic pH inside the macrophages. In this review we have discussed the physiological and biochemical changes in promastigotes which make them infective and how these infection ready parasites respond to intramacrophagic stress. We have summed up the changes in expression of structural proteins, virulence factors (including species-specific virulence factors), and stress related proteins when the parasites convert to metacyclic promastigotes and then from metacyclics to amastigotes, and how these pathways have been targeted for therapy. The trends in global gene expression of Leishmania under various conditions and at various life-stages using modern molecular biology approaches such as genomics, transcriptomics, proteomics and metabolomics have been discussed in conjunction with the theory of pre-adaptation of the parasites for life inside macrophages

IL-22: an underestimated player in natural resistance to tuberculosis?

Approximately 10% of individuals latently infected with Mycobacterium tuberculosis (Mtb) develop active tuberculosis (TB) during their lifetime. Although it is well recognized that T-helper 1 immune responses are crucial for containing latent TB infection, the full array of host factors conferring protective immunity from TB progression are not completely understood. IL-22 is produced by cells of the innate and adaptive immune system including innate lymphoid cells, and natural killer cells as well as T lymphocytes (Th1, Th17, and Th22) and binds to its cognate receptor, the IL-22R1, which is expressed on non-hematopoietic cells such as lung epithelial cells. However, recent studies suggest that Mtb induces expression of the IL-22R1 on infected macrophages and multiple studies have indicated a protective role of IL-22 in respiratory tract infections. Reduced concentrations of circulating IL-22 in active TB compared to latent TB and decreased percentages of Mtb-specific IL-22 producing T cells in TB patients compared to controls designate this cytokine as a key player in TB immunology. More recently, it has been shown that in type 2 diabetes (T2D) and TB co-morbidity serum IL-22 concentrations are further reduced compared to TB patients without co-morbidities. However, whether a causative link between low IL-22 and increased susceptibility to TB and disease severity of TB exists remains to be established. This review summarizes the contribution of IL-22, a potentially under-appreciated key player in natural resistance to TB, at the interface between the immune response to Mtb and the lung epithelium

Comparison of liposome based antigen delivery systems for protection against Leishmania donovani

Liposomes have been widely exploited as antigen delivery systems for a variety of diseases including leishmaniasis. These vesicles can be prepared in various ways which may affect the immunogenicity of the encapsulated antigens. In this study we compared the vaccine potentiality of three cationic formulations with Leishmania donovani promastigote membrane antigens (LAg) and the best vesicle was evaluated for long-term protection against experimental visceral leishmaniasis. We immunized mice with LAg encapsulated in multilamellar vesicles (MLV), dehydration–rehydration vesicles (DRV) and reverse-phase evaporation vesicles (REV) and challenged them with parasites ten days after vaccination. LAg in MLV or DRV induced almost complete protection, while LAg alone or entrapped in REV exhibited partial resistance. Protection observed with antigen incorporated MLV or DRV was predominantly Th1 as evidenced by elicitation of significantly high DTH, IgG2a antibodies and IFN-γ. MLV encapsulated LAg demonstrated durable cell-mediated immunity and mice challenged ten weeks after vaccination could also resist experimental challenge strongly. Field trials of L. donovani vaccine were unsatisfactory mainly due to lack of an appropriate adjuvant. Cationic MLV when used as adjuvant with protein antigens induced sustained Th1 immunity. Adjuvant potential of cationic MLV can be utilized to design subunit vaccines