Identification and evaluation of immunogenic MHC-I and MHC-II binding peptides from Mycobacterium tuberculosis.

Due to several limitations of the only available BCG vaccine, to generate adequate protective immune responses, it is important to develop potent and cost-effective vaccines against tuberculosis (TB). In this study, we have used an immune-informatics approach to identify potential peptide based vaccine targets against TB. The proteome of Mycobacterium tuberculosis (Mtb), the causative agent of TB, was analyzed for secretory or surface localized antigenic proteins as potential vaccine candidates. The T- and B-cell epitopes as well as MHC molecule binding efficiency were identified and mapped in the modelled structures of the selected proteins. Based on antigenicity score and molecular dynamic simulation (MD) studies two peptides namely Pep-9 and Pep-15 were analyzed, modelled and docked with MHC-I and MHC-II structures. Both peptides exhibited no cytotoxicity and were able to induce proinflammatory cytokine secretion in stimulated macrophages. The molecular docking, MD and in-vitro studies of the predicted B and T-cell epitopes of Pep-9 and Pep-15 peptides with the modelled MHC structures exhibited strong binding affinity and antigenic properties, suggesting that the complex is stable, and that these peptides can be considered as a potential candidates for the development of vaccine against TB.

Molecular docking of bioactive compounds derived from Moringa oleifera with p53 protein in the apoptosis pathway of oral squamous cell carcinoma.

Moringa oleifera is nowadays raising as the most preferred medicinal plant, as every part of the moringa plant has potential bioactive compounds which can be used as herbal medicines. Some bioactive compounds of M. oleifera possess potential anti-cancer properties which interact with the apoptosis protein p53 in cancer cell lines of oral squamous cell carcinoma. This research work focuses on the interaction among the selected bioactive compounds derived from M. oleifera with targeted apoptosis protein p53 from the apoptosis pathway to check whether the bioactive compound will induce apoptosis after the mutation in p53. To check the toxicity and drug-likeness of the selected bioactive compound derived from M. oleifera based on Lipinski's Rule of Five. Detailed analysis of the 3D structure of apoptosis protein p53. To analyze protein's active site by CASTp 3.0 server. Molecular docking and binding affinity were analyzed between protein p53 with selected bioactive compounds in order to find the most potential inhibitor against the target. This study shows the docking between the potential bioactive compounds with targeted apoptosis protein p53. Quercetin was the most potential bioactive compound whereas kaempferol shows poor affinity towards the targeted p53 protein in the apoptosis pathway. Thus, the objective of this research can provide an insight prediction towards M. oleifera derived bioactive compounds and target apoptosis protein p53 in the structural analysis for compound isolation and in-vivo experiments on the cancer cell line.

Mycobacterium tuberculosis Rv3034c regulates mTORC1 and PPAR-γ dependant pexophagy mechanism to control redox levels in macrophages.

Mycobacterium tuberculosis survives inside the macrophages by employing several host immune evasion strategies. Here, we reported a novel mechanism in which M. tuberculosis acetyltransferase, encoded by Rv3034c, induces peroxisome homeostasis to regulate host oxidative stress levels to facilitate intracellular mycobacterial infection. Presence of M. tuberculosis Rv3034c induces the expression of peroxisome biogenesis and proliferation factors such as Pex3, Pex5, Pex19, Pex11b, Fis-1 and DLP-1; while depletion of Rv3034c decreased the expression of these molecules, thereby selective degradation of peroxisomes via pexophagy. Further studies revealed that M. tuberculosis Rv3034c inhibit induction of pexophagy mechanism by down-regulating the expression of pexophagy associated proteins (p-AMPKα, p-ULK-1, Atg5, Atg7, Beclin-1, LC3-II, TFEB and Keap-1) and adaptor molecules (NBR1 and p62). Inhibition was found to be dependent on the phosphorylation of mTORC1 and activation of peroxisome proliferator activated receptor-γ. In order to maintain intracellular homeostasis during oxidative stress, M. tuberculosis Rv3034c was found to induce degradation of dysfunctional and damaged peroxisomes through activation of Pex14 in infected macrophages. In conclusion, this is the first report which demonstrated that M. tuberculosis acetyltransferase regulate peroxisome homeostasis in response to intracellular redox levels to favour mycobacterial infection in macrophage.

Mycobacterium tuberculosis LprE Suppresses TLR2-Dependent Cathelicidin and Autophagy Expression to Enhance Bacterial Survival in Macrophages.

Despite representing a very important class of virulence proteins, the role of lipoproteins in the pathogenesis of Mycobacterium tuberculosis remains elusive. In this study, we investigated the role of putative lipoprotein LprE in the subversion of host immune responses using the M. tuberculosis CDC1551 LprE (LprE Mtb ) mutant (Mtb∆LprE). We show that deletion of LprE Mtb results in reduction of M. tuberculosis virulence in human and mouse macrophages due to upregulation of vitamin D3-responsive cathelicidin expression through the TLR2-dependent p38-MAPK-CYP27B1-VDR signaling pathway. Conversely, episomal expression of LprE Mtb in Mycobacterium smegmatis improved bacterial survival. Infection in siTLR2-treated or tlr2-/- macrophages reduced the survival of LprE Mtb expressing M. tuberculosis and M. smegmatis because of a surge in the expression of cathelicidin. Infection with the LprE Mtb mutant also led to accumulation of autophagy-related proteins (LC3, Atg-5, and Beclin-1) and augmented recruitment of phagosomal (EEA1 and Rab7) and lysosomal (LAMP1) proteins, thereby resulting in the reduction of the bacterial count in macrophages. The inhibition of phago-lysosome fusion by LprE Mtb was found to be due to downregulation of IL-12 and IL-22 cytokines. Altogether, our data indicate that LprE Mtb is an important virulence factor that plays a crucial role in mycobacterial pathogenesis in the context of innate immunity.

In silico discovery of potential drug molecules to improve the treatment of isoniazid-resistant Mycobacterium tuberculosis.

The emergence of multidrug-resistant Mycobacterium tuberculosis (M.tb) has become one of the major hurdles in the treatment of tuberculosis (TB). Drug-resistant M.tb has evolved with various strategies to avoid killing by the anti-tubercular drugs. Thus, there is a rising need to develop effective anti-TB drugs to improve the treatment of these strains. Traditional drug design approach has earned little success due to time and the cost involved in the process of development of anti-infective drugs. Numerous reports have demonstrated that several mutations in the drug target sites cause emergence of drug-resistant M.tb strains. In this study, we performed computational mutational analysis of M.tb inhA, fabD, and ahpC genes, which are the primary targets for first-line isoniazid (INH) drug. In silico virtual drug screening was performed to identify the potent drugs from a ChEMBL compound library to improve the treatment of INH-resistant M.tb. Further, these compounds were analyzed for their binding efficiency against active drug binding cavity of M.tb wild-type and mutant InhA, FabD and AhpC proteins. The drug efficacy of predicted lead compounds was verified by molecular docking using M.tb wild-type and mutant InhA, FabD and AhpC protein template models. Different in silico and pharmacophore analysis predicted three potent lead compounds with better drug-like properties against both M.tb wild-type and mutant InhA, FabD, and AhpC proteins as compared to INH drug, and thus may be considered as effective drugs for the treatment of INH-resistant M.tb strains. We hypothesize that this work may accelerate drug discovery process for the treatment of drug-resistant TB. Communicated by Ramaswamy H. Sarma.

Computational discovery of potent drugs to improve the treatment of pyrazinamide resistant Mycobacterium tuberculosis mutants.

Emergence of multi-drug resistance tuberculosis has become a serious health problem globally. Accumulation of mutations in the drug target led to the development of multi-drug resistant mycobacterial strains that have made most of the conventional drugs ineffective. Hence, there is desperate need for the development of new therapeutic strategies. Here, we focused on the analysis of mutations in Mycobacterium tuberculosis (Mtb) PncA (pyrazinamidase) that is responsible for resistance against first-line anti-tuberculosis pyrazinamide (PZA) drug. First, PZA and its two isoforms were analyzed for their binding affinity toward ligand binding cavity of Mtb wild-type and mutant PncA proteins. The observations suggested that some drug resistant mutations cause strong binding of PncA with the active form of PZA and impair its release, which is required to inhibit the growth of Mtb. To improve the treatment of PZA resistant Mtb, high throughput virtual drug screening was performed to identify potent drug molecules from a library of compounds derived from ChEMBL database. From this library, we predicted a lead molecule (terta-butyl(2S,4S)-4-amino-2-cyclopropyl-6-(trifluoromethyl)-3,4-dihydro-2H-quinoline-1-carboxylate) to be more effective against PZA resistant Mtb strains in comparison to PZA. The lead molecule showed better drug-like properties such as high affinity and atomic interactions with wild-type and drug-resistant mutations in Mtb PncA proteins. Further, molecular dynamic simulation studies showed that this lead molecule has better conformational stability and compatibility with drug-resistant PncA proteins in comparison to PZA drug. We hypothesized that the predicted lead compound could be more effective, and thus may improve the treatment of PZA resistant tuberculosis.

Elucidation of the Inhibitory Effect of Phytochemicals with Kir6.2 Wild-Type and Mutant Models Associated in Type-1 Diabetes through Molecular Docking Approach.

Among all serious diseases globally, diabetes (type 1 and type 2) still poses a major challenge to the world population. Several target proteins have been identified, and the etiology causing diabetes has been reasonably well studied. But, there is still a gap in deciding on the choice of a drug, especially when the target is mutated. Mutations in the KCNJ11 gene, encoding the kir6.2 channel, are reported to be associated with congenital hyperinsulinism, having a major impact in causing type 1 diabetes, and due to the lack of its 3D structure, an attempt has been made to predict the structure of kir6.2, applying fold recognition methods. The current work is intended to investigate the affinity of four phytochemicals namely, curcumin (Curcuma longa), genistein (Genista tinctoria), piperine (Piper nigrum), and pterostilbene (Vitis vinifera) in a normal as well as in a mutant kir6.2 model by adopting a molecular docking methodology. The phytochemicals were docked in both wild and mutated kir6.2 models in two rounds: blind docking followed by ATP-binding pocket-specific docking. From the binding pockets, the common interacting amino acid residues participating strongly within the binding pocket were identified and compared. From the study, we conclude that these phytochemicals have strong affinity in both the normal and mutant kir6.2 model. This work would be helpful for further study of the phytochemicals above for the treatment of type 1 diabetes by targeting the kir6.2 channel.