2,4-Dihydroxycinnamic acid as spike ACE2 inhibitor and apigenin as RdRp inhibitor in Nimbamritadi Panchatiktam Kashayam against COVID-19: an in silico and in vitro approach.

Nimbamritadi Panchatiktam Kashayam (NPK) is an ayurvedic formulation composed of ingredients with potent anti-viral activities. We studied the interaction energy of 144 phytoconstituents present in NPK against spike receptor-binding domain (RBD) complexed with ACE2 protein (PDB ID: 6LZG) and RNA-dependent RNA polymerase protein (PDB ID: 7BTF) using Biovia Drug Discovery studio. The result indicated that 2,4-hydroxycinnamic acid exerts more significant binding affinities (28.43 kcal/mol) than Umifenovir (21.24 kcal/mol) against spike ACE2. Apigenin exhibited the highest binding affinities (54.63 kcal/mol) compared with Remdesivir (24.52 kcal/mol) against RdRp. An in vitro analysis showed a reduction in the number of lentiviral particles on transfected HEK293T-hACE2 cells as assessed by pseudovirus inhibition assay. At the same time, the tested compounds showed non-toxic up to 100 µg/ml in normal cells by MTT assay. The study highlights the plausible clinical utility of this traditional medicine against SARS CoV2.

Modulation of carcinogenesis with selected GRAS nutraceuticals via Keap1-Nrf2 signaling pathway.

Keap1-Nrf2 is a fundamental signaling cascade known to promote or prevent carcinogenesis. Extensive studies identify the key target of modulatory aspects of Keap1-Nrf2 signaling against cancer. Nutraceuticals are those dietary agents with many health benefits that have immense potential for cancer chemoprevention. The nutritional supplements known as nutraceuticals are found to be one of the most promising chemoprevention agents. Upon investigating the dual nature of Nrf2, it became clear that, in addition to shielding normal cells from numerous stresses, Nrf2 may also promote the growth of tumors. In the present review, we performed a systematic analysis of the role of 12 different nutraceuticals like curcumin, sulforaphane, resveratrol, polyunsaturated fatty acids (PUFA) from fish oil, lycopene, soybean, kaempferol, allicin, thymoquinone, quercetin, gingerol, and piperine in modulating the Nrf2/Keap1 signaling mechanism. Among these, 12 Generally Recognized As Safe (GRAS) certified nutraceuticals, sulforaphane is the most extensively studied compound in modulating Keap1-Nrf signaling. Even though there is much evidence at preclinical levels, further high-quality research is still required to validate the potential role of these nutraceuticals in Keap1-Nrf2 modulation.

An insight into the role of telmisartan as PPAR-γ/α dual activator in the management of nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is the most common hepatic disease. It is rapidly emerging as the frequent cause for liver transplantation with the risk of disease recurrence, even after transplantation. Clinical evidence showed an abnormally altered expression of different peroxisome proliferator-activated receptor (PPAR) isotypes (PPAR-α/γ/δ) in NAFLD with an involvement in the induction of insulin resistance, hepatic steatosis, reactive oxygen species (ROS) formation, and hepatic inflammation. Recently, several dual PPAR-γ/α agonists were developed to simultaneously achieve the insulin-sensitizing effect of PPAR-γ as well as lipid catabolizing effect of PPAR-α. PPAR-α activation could counterbalance the steatogenic and adipogenic effects of PPAR-γ. But most of the drugs were ended in the initial level itself due to harmful adverse effects. In the present review, we discuss the possible mechanism of telmisartan, a typical angiotensin receptor blocker with excellent safety and pharmacokinetic profile, as a PPAR-γ/α dual agonist in the treatment of NAFLD.

Harnessing the immune system against cancer: current immunotherapy approaches and therapeutic targets.

Cancer immunotherapy is a rapidly evolving concept that has been given the tag "fifth pillar" of cancer therapy while radiation therapy, chemotherapy, surgery and targeted therapy remain the other four pillars. This involves the stimulation of the immune system to control tumor growth and it specifically targets the neoplastic cells rather than the normal cells. Conventional chemotherapy has many limitations which include drug resistance, recurrence of cancer and severe adverse effects. Immunology has made major treatment breakthroughs for several cancers such as colorectal cancer, prostate cancer, breast cancer, lung cancer, liver cancer, kidney cancer, stomach cancer, acute lymphoblastic leukaemia etc. Currently, therapeutic strategies harnessing the immune system involve Checkpoint inhibitors, Chimeric antigen receptor T cells (CAR T cells), Monoclonal antibodies, Cancer vaccines, Cytokines, Radio-immunotherapy and Oncolytic virus therapy. The molecular characterization of several tumor antigens (TA) indicates that these TA can be utilized as promising candidates in cancer immunotherapy strategies. Here in this review, we highlight and summarize the different categories of emerging cancer immunotherapies along with the immunologically recognized tumor antigens involved in the tumor microenvironment.

Inevitable role of TGF-ß1 in progression of nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is a major health concern and the most commonly diagnosed chronic liver manifestation among 25% worldwide population. Obesity, insulin resistance, accumulation of toxic lipid free radicals, generation of oxidative stress, overconsumption of fat containing dietary meals and lack of exercise are the paramount factors accountable for the development of NAFLD. During NAFLD, increased oxidative stress and production of enormous number of toxic free radicals activates a number of pro-inflammatory and inflammatory pathways. TGF-ß signaling mechanisms play a central role in maintaining the normal homeostasis of liver. TGF-ß1, one of the three isoforms of TGF-ß family has significant role in different stages of chronic liver conditions. TGF-ß1 promotes HSC activation and extracellular matrix production (ECM), which further contributes in the progression of NAFLD. In this review, we outline the role of TGF-ß1 in different phases of progressive NAFLD along with the signaling mechanism.

Mast cells and the gut-liver Axis: Implications for liver disease progression and therapy.

The role of mast cells, traditionally recognized for their involvement in immediate hypersensitivity reactions, has garnered significant attention in liver diseases. Studies have indicated a notable increase in mast cell counts following hepatic injury, underscoring their potential contribution to liver disorder pathogenesis. Predominantly situated in connective tissue that envelops the hepatic veins, bile ducts, and arteries, mast cells are central to both initiating and perpetuating liver disorders. Additionally, they are crucial for maintaining gastrointestinal barrier function. The gut-liver axis emphasizes the complex, two-way communication between the gut microbiome and the liver. Past research has implicated gut microbiota and their metabolites in the progression of hepatic disorders. This review sheds light on how mast cells are activated in various liver conditions such as alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), viral hepatitis, hepatic fibrogenesis, and hepatocellular carcinoma. It also briefly explores the connection between the gut microbiome and mast cell activation in these hepatic conditions.

Unveiling the role of the Hedgehog signaling pathway in chronic liver disease: Therapeutic insights and strategies.

The Hedgehog (Hh) signaling plays a crucial role in adult liver repair by promoting the expansion and differentiation of hepatic progenitor cells into mature hepatocytes and cholangiocytes. Elevated Hh signaling is associated with severe chronic liver diseases, making Hh inhibitors a promising therapeutic option. Sonidegib and vismodegib, both FDA-approved Smoothened (Smo) inhibitors for basal cell carcinoma (BCC), have shown potential for application in chronic liver disorders based on clinical evidence. We highlight the vital role of the Hh pathway in metabolic dysfunction-associated steatotic liver disease (MASLD)/metabolic dysfunction-associated steatohepatitis (MASH), liver fibrosis, and hepatocellular carcinoma (HCC). Moreover, therapeutic strategies targeting the Hh pathway in chronic liver diseases have been discussed, providing a basis for improving disease management and outcomes.

Role of Culinary Indian Spices in the Regulation of TGF-ß Signaling Pathway in Inflammation-Induced Liver Cancer.

SCOPE: Hepatocellular carcinoma (HCC) results from various etiologies, such as Hepatitis B and C, Alcoholic and Non-alcoholic fatty liver disorders, fibrosis, and cirrhosis. About 80 to 90% of HCC cases possess cirrhosis, which is brought on by persistent liver inflammation. TGF-ß is a multifunctional polypeptide molecule that acts as a pro-fibrogenic marker, inflammatory cytokine, immunosuppressive agent, and pro-carcinogenic growth factor during the progression of HCC. The preclinical and clinical evidence illustrates that TGF-ß can induce epithelial-to-mesenchymal transition, promoting progression and hepatocyte immune evasion. Therefore, targeting the TGF-ß pathway can be a promising therapeutic option against HCC. METHODS AND RESULTS: We carry out a systemic analysis of eight potentially selected culinary Indian spices: Turmeric, Black pepper, Ginger, Garlic, Fenugreek, Red pepper, Clove, Cinnamon, and their bioactives in regulation of the TGF-ß pathway against liver cancer. CONCLUSION: Turmeric and its active constituent, curcumin, possess the highest therapeutic potential in treating inflammation-induced HCC and they also have the maximum number of ongoing in-vivo and in-vitro studies.

Tumor-Specific Growth Factor (TSGF): A Futuristic Tumor Biomarker in Early Diagnosis of Cancer.

Despite the significant improvement in the treatment modalities, cancer is one of the fastest-growing chronic disease conditions all over the world. Genetic and Epigenetic alterations in the normal physiology of the cell are the key factor for tumor development. These changes can trigger the production of abnormal protein expressions through stimulation of different signaling pathways and can deeply affect normal cell growth and proliferation. Any altered protein expression, genetic variation, micro-RNA or post-translational protein modifications that indicate tumorigenesis can act as an early signal termed as biomarker. Cancer, being a multistep process with accumulating genetic and epigenetic alterations, could be detected early with suitable biomarkers. There are several proteins such as AFP, CA-125, PSA, troponin, CEA, osteopontin, CA 19-9 that act as biomarkers which help in early detection, prognosis, and monitoring of disease progression, a hunt for newer biomarkers with higher specificity and sensitivity is still ongoing. Tumor-specific growth factor (TSGF) is one such budding and prevailing tumor biomarker used for the early-stage detection of several types of carcinomas. TSGF is a gene that helps in tumor angiogenesis and gets released during the preliminary stages from cancer cells that ensure the vascular proliferation of the same. In this review, the clinical investigations of TSGF in different kinds of malignancy is discussed in detail and suggests the possibility of using TSGF as a biomarker in early diagnosis of cancer.

Decoding the Mechanism of Drugs of Heterocyclic Nature against Hepatocellular Carcinoma.

OBJECTIVES: Hepatocellular carcinoma (HCC) is the sixth most common type of cancer and accounts for ~90% of cases, with an approximated incidence of >1 million cases by 2025. Currently, the backbone of HCC therapy is the oral multi-kinase inhibitor, Sorafenib, which consists of a Pyridine heterocycle ring system. This review highlights the introspective characteristics of seven anticancer drugs of heterocyclic nature against HCC along with their structural activity relationships and molecular targets. METHODS: Literature collection was performed using PubMed, Google Scholar, SCOPUS, and Cross ref. Additional information was taken from the official website of the FDA and GLOBOCAN. Key findings/ Results: Based on the available literature, approved heterocyclic compounds show promising results against HCC, including Sorafenib (Pyridine), Regorafenib (Pyridine), Lenvatinib (Quinoline), Cabozantinib (Quinoline), Gemcitabine (Pyrimidine), 5-Fluorouracil (Pyrimidine)and Capecitabine (Pyrimidine), their mechanism of action and key aspects regarding its structural activity were included in the review. CONCLUSION: Heterocyclic compounds represent almost two-thirds of the novel drugs approved by FDA between 2010 and 2020 against Cancer. This review summarizes the clinical relevance, mechanism of action, structural activity relationship, and challenges of the seven available anticancer drugs with heterocyclic ring systems against HCC.

Evaluation of the Nimbamrithadhi Panchathiktha Kashayam against SARS CoV-2 based on Network Pharmacology and Molecular Docking analysis.

BACKGROUND: Nimbamrithadhi Panchathiktha Kashayam (NPK) is an Ayurvedic formulation of potent plant ingredients with immune-modulating effects and anti-viral activities. OBJECTIVES: The present study is intended to identify the key target involved in immune and inflammatory response against SARS-COV-2 via network pharmacology and also investigates the potent phytoconstituent within NPK in combating or modulating target response via molecular docking. METHODS: Active phytoconstituents of NPK were filtered based on overall bioavailability and druglikeness by Lipinski's and ADMETOX prediction. RESULTS: Results indicate that IRF 7 can be selected as an efficient target in regulating immunomodulatory and anti-viral activity via network pharmacology. Molecular docking studies show that apigenin (22.22 Kcal /mol), thiamine (24.89 Kcal /mol) and esculetin (25.21 Kcal /mol) within Nimbamrithadhi Panchathiktha Kashayam(NPK) possess better binding affinity in comparison with standard drug gemcitabine (14.56 Kcal /mol). Even though docking score is more for Esculetin and Thiamine, Apigenin within Solanum Virgianum (Yellow nightshade) and Azadirachta Indica (Neem) is considered as the active phytoconstituent in modulating immune responses and anti-viral activities based on the number and nature of amino acid interaction. CONCLUSION: To the best of our knowledge, no scientific validation has been done on NPK against COVID-19. The study indicates that NPK can be a better alternative prophylaxis strategy against SARS-COV-2 infection if further validated via suitable preclinical studies.

Identification of Kaempferol as Viral Entry Inhibitor and DL-Arginine as Viral Replication Inhibitor from Selected Plants of Indian Traditional Medicine against COVID-19: An in silico Guided in vitro Approach.

BACKGROUND: Indian traditional medicinal plants are known for their great potential in combating viral diseases. Previously, we reported a systematic review approach of seven plausible traditional Indian medicinal plants against SARS-CoV-2. METHODS: Molecular docking was conducted with Biovia Discovery Studio. Three binding domains for spike glycoprotein (PDB IDs: 6LZG, 6M17, 6M0J) and one binding domain of RdRp (PDB ID: 7BTF) were used. Among 100 phytoconstituents listed from seven plants by the IMPPAT database used for virtual screening, the best six compounds were again filtered using Swiss ADME prediction and Lipinski's rule. Additionally, a pseudovirion assay was performed to study the interaction of SARS-CoV-2 S1-protein with the ACE 2 receptor to further confirm the effect. RESULTS: Chebulagic acid (52.06 Kcal/mol) and kaempferol (48.84 Kcal/mol) showed increased interaction energy compared to umifenovir (33.68 Kcal/mol) for the 6LZG binding domain of spike glycoprotein. Epicatechin gallate (36.95 Kcal/mol) and arachidic acid (26.09 Kcal/mol) showed equally comparable interaction energy compared to umifenovir (38.20 Kcal/mol) for the 6M17 binding domain of spike glycoprotein. Trihydroxychalcone (35.23 Kcal/mol) and kaempferol (36.96 Kcal/mol) showed equally comparable interaction energy with umifenovir (36.60 Kcal/mol) for 6M0J binding domain of spike glycoprotein. Upon analyzing the phytoconstituents against RdRp binding domain, DL-arginine (41.78 Kcal/mol) showed comparable results with the positive control remdesivir (47.61 Kcal/mol). ADME analysis performed using Swiss ADME revealed that kaempferol and DL arginine showed drug-like properties with appropriate pharmacokinetic parameters. Further in vitro analysis of kaempferol by pseudovirion assay confirmed an acceptable decrease of the lentiviral particles in transfected HEK293T-hACE2 cells. CONCLUSION: The study highlights that kaempferol and DL-arginine could be the significant molecules to exhibit potent action against SARS-CoV-2 and its variants.

Decoding Immune Signature to Detect the Risk for Early-Stage HCC Recurrence.

Hepatocellular carcinoma (HCC) is often recognized as an inflammation-linked cancer, which possesses an immunosuppressive tumor microenvironment. Curative treatments such as surgical resection, liver transplantation, and percutaneous ablation are mainly applicable in the early stage and demonstrate significant improvement of survival rate in most patients. However, 70-80% of patients report HCC recurrence within 5 years of curative treatment, representing an important clinical issue. However, there is no effective recurrence marker after surgical and locoregional therapies, thus, tumor size, number, and histological features such as cancer cell differentiation are often considered as risk factors for HCC recurrence. Host immunity plays a critical role in regulating carcinogenesis, and the immune microenvironment characterized by its composition, functional status, and density undergoes significant alterations in each stage of cancer progression. Recent studies reported that analysis of immune contexture could yield valuable information regarding the treatment response, prognosis and recurrence. This review emphasizes the prognostic value of tumors associated with immune factors in HCC recurrence after curative treatment. In particular, we review the immune landscape and immunological factors contributing to early-stage HCC recurrence, and discuss the immunotherapeutic interventions to prevent tumor recurrence following curative treatments.

An Insight Into the Role of Alpha-Fetoprotein (AFP) in the Development and Progression of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the primary malignancy of hepatocytes and the second most common cause of cancer-related mortality across the globe. Despite significant advancements in screening, diagnosis, and treatment modalities for HCC, the mortality-to-incidence ratio remain unacceptably high. A recent study indicates that a minor population of HCCs are AFP negative or express the normal range of AFP levels. Although it is a gold standard and a more reliable biomarker in the advanced stage of HCC and poorly differentiated tumors, it does not serve as a suitable means for screening HCC. AFP plays a significant role in the development and progression of HCC and understanding its role is crucial. By examining the molecular mechanisms involved in AFP-mediated tumorigenesis, we can better understand HCC pathogenesis and identify potential therapeutic targets. This article details the role of alpha-fetoprotein (AFP) in the carcinogenic transformation of hepatocytes. The article also focuses on information about the structure, biosynthesis, and regulation of AFP at the gene level. Additionally, it discusses the immune evasion, metastasis, and control of gene expression that AFP mediates during HCC.

Biology, Significance and Immune Signaling of Mucin 1 in Hepatocellular Carcinoma.

Mucin 1 (MUC 1) is a highly glycosylated tumor-associated antigen (TAA) overexpressed in hepatocellular carcinoma (HCC). This protein plays a critical role in various immune-mediated signaling pathways at its transcriptional and post-transcriptional levels, leading to immune evasion and metastasis in HCC. HCC cells maintain an immune-suppressive environment with the help of immunesuppressive tumor-associated antigens, resulting in a metastatic spread of the disease. The development of intense immunotherapeutic strategies to target tumor-associated antigen is critical to overcoming the progression of HCC. MUC 1 remains the most recognized tumor-associated antigen since its discovery over 30 years ago. A few promising immunotherapies targeting MUC 1 are currently under clinical trials, including CAR-T and CAR-pNK-mediated therapies. This review highlights the biosynthesis, significance, and clinical implication of MUC 1 as an immune target in HCC.

Deciphering the role of transforming growth factor-beta 1 as a diagnostic-prognostic-therapeutic candidate against hepatocellular carcinoma.

Transforming growth factor-beta (TGF-ß) is a multifunctional cytokine that performs a dual role as a tumor suppressor and tumor promoter during cancer progression. Among different ligands of the TGF-ß family, TGF-ß1 modulates most of its biological outcomes. Despite the abundant expression of TGF-ß1 in the liver, steatosis to hepatocellular carcinoma (HCC) progression triggers elevated TGF-ß1 levels, contributing to poor prognosis and survival. Additionally, elevated TGF-ß1 levels in the tumor microenvironment create an immunosuppressive stage via various mechanisms. TGF-ß1 has a prime role as a diagnostic and prognostic biomarker in HCC. Moreover, TGF-ß1 is widely studied as a therapeutic target either as monotherapy or combined with immune checkpoint inhibitors. This review provides clinical relevance and up-to-date information regarding the potential of TGF-ß1 in diagnosis, prognosis, and therapy against HCC.

Unravelling the Immune Modulatory Effect of Indian Spices to Impede the Transmission of COVID-19: A Promising Approach.

Months after WHO declared COVID-19 as a Global Public Health Emergency of International Concern, it does not seem to be flattening the curve as we are still devoid of an effective treatment modality and vaccination is in the first phase in many countries. Amid such uncertainty, being immune is the best strategy to defend against corona attacks. As the whole world is referring back to immune-boosting traditional remedies, interest is rekindled in the Indian system of Medicine, which is gifted with an abundance of herbal medicines as well as remedies. Among them, spices (root, rhizome, seed, fruit, leaf, bud, and flower of various plants used to add taste and flavors to food) are bestowed with immense medicinal potential. A plethora of clinical as well as preclinical studies reported the effectiveness of various spices for various ailments. The potential immune-boosting properties together with their excellent safety profiles are making spices the current choice of phytoresearch as well as the immune-boosting home remedies during these sceptical times. The present review critically evaluates the immune impact of various Indian spices and their potential to tackle the novel coronavirus, with comments on the safety and toxicity aspects of spices.

Evaluation of the active constituents of Nilavembu Kudineer for viral replication inhibition against SARS-CoV-2: An approach to targeting RNA-dependent RNA polymerase (RdRp).

The World Health Organization has declared the novel coronavirus (COVID-19) outbreak a global pandemic and emerging threat to people in the 21st century. SARS-CoV-2 constitutes RNA-Dependent RNA Polymerase (RdRp) viral proteins, a critical target in the viral replication process. No FDA-approved drug is currently available, and there is a high demand for therapeutic strategies against COVID-19. In search of the anti-COVID-19 compound from traditional medicine, we evaluated the active moieties from Nilavembu Kudineer (NK), a poly-herbal Siddha formulation recommended by AYUSH against COVID-19. We conducted a preliminary docking analysis of 355 phytochemicals (retrieved from PubChem and IMPPAT databases) present in NK against RdRp viral protein (PDB ID: 7B3B) using COVID-19 Docking Server and further with AutoDockTool-1.5.6. MD simulation studies confirmed that Orientin (L1), Vitexin (L2), and Kasuagamycin (L3) revealed better binding activity against RdRp (PDB ID: 7B3B) in comparison with Remdesivir. The study suggests a potential scaffold for developing drug candidates against COVID-19. PRACTICAL APPLICATIONS: Nilavembu Kudineer is a poly-herbal Siddha formulation effective against various diseases like cough, fever, breathing problems, etc. This study shows that different phytoconstituents identified from Nilavembu Kudineer were subjected to in silico and ADME analyses. Out of the former 355 phytochemical molecules, Orientin (L1), Vitexin (L2), and Kasuagamycin (L3) showed better binding activity against RdRp viral protein (PDB ID: 7B3B) in comparison with the synthetic repurposed drug. Our work explores the search for an anti-COVID-19 compound from traditional medicine like Nilavembu Kudineer, which can be a potential scaffold for developing drug candidates against COVID-19.

Critical biomarkers of hepatocellular carcinoma in body fluids and gut microbiota.

Hepatocellular carcinoma (HCC) is the most prevalent primary liver cancer and one of the major causes of cancer-related death. The development of specific non-invasive or diagnostic markers from blood, urine and feces may represent a valuable tool for detecting HCC at an early stage. Biomarkers are considered novel potential targets for therapeutic intervention. It helps in the prediction of prognosis or recurrence of HCC, and also assist in the selection of appropriate treatment modality. We summarize the most relevant existing data about various biomarkers that play a key role in the progression of HCC.

The Ineluctable Role of ACE-2 Receptors in SARS COV-2 Infection and Drug Repurposing as a Plausible SARS COV-2 Therapy: A Concise Treatise.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiological agent for the COVID-19 infectious disease that spreads via the respiratory route and has reached a drastic level of a global pandemic. Symptoms of COVID-19 may vary from mild (fever, dry cough, shortness of breath) to severe pneumonia-like respiratory symptoms as exacerbation of disease occurs. Unlike SARS-CoV, the SARSCoV- 2 has a higher binding affinity to ACE-2 receptors, which signifies its higher transmission rate from person to person. Even though ACE-2 is significant in the reninangiotensin- aldosterone system (RAAS) regulation that exhibits protection to various organs, it plays a significant role in COVID-19 disease pathogenesis. Viral interferences with the ACE-2 peptidase activity are found in SARS-CoV-2 infected patients leading to pro-inflammatory responses, hypertension and multi-organ damage. Angiotensinconverting enzyme-2 is constrained to a variety of organ systems, but surface ACE-2 receptors on lung epithelia are largely affected, which lead to pathological alterations in lung histology which may progress to respiratory failure. The viral tropism mainly occurs by the attachment to the angiotensin-converting enzymes-2 receptors in the host cell; thus drugs targeting ACE-2 expressions may arise as the future therapeutic strategy to combat COVID-19 infections. The innovative approach of repurposing drugs has shown temporary effectiveness to curb the rising pandemic. This article mainly focuses on the prominence of ACE-2 receptors which are expressed during the COVID infections and the repurposing strategy of available drug therapies.