Repurposing of antiparasitic niclosamide to inhibit respiratory syncytial virus (RSV) replication.

Despite being an important health problem, there are only supportive care treatments for respiratory syncytial virus (RSV) infection. Thus, discovery of specific therapeutic drugs for RSV is still needed. Recently, an antiparasitic drug niclosamide has shown a broad-spectrum antiviral activity. Here, our in vitro model was used to study the antiviral effect of niclosamide on RSV and its related mechanism. Niclosamide inhibited RSV with time and dose-dependent manner. Pretreatment with submicromolar concentration of niclosamide for 6 h presented the highest anti-RSV activity of 94 % (50 % effective concentration; EC50 of 0.022 µM). Niclosamide efficiently blocked infection of laboratory strains and clinical isolates of both RSV-A and RSV-B in a bronchial epithelial cell line. Although a disruption of the mechanistic target of rapamycin complex 1 (mTORC1) pathway by niclosamide was previously hypothesized as a mechanism against pH-independent viruses like RSV, using a chemical mTORC1 inhibitor, temsirolimus, and a chemical mTORC1 agonist, MHY1485 (MHY), we show here that the mechanism of RSV inhibition by niclosamide was mTORC1 independent. Indeed, our data indicated that niclosamide hindered RSV infection via proapoptotic activity by a reduction of AKT prosurvival protein, activation of cleaved caspase-3 and PARP (poly ADP-ribose polymerase), and an early apoptosis induction.

Inhibition of human immunodeficiency virus type 1 by niclosamide through mTORC1 inhibition.

Niclosamide has been known to inhibit a number of pH-dependent viruses via the neutralization of endosomal acidic pH. It has also been shown to disrupt the mTORC1 signaling pathway. The replication of many viruses requires mTORC1 activation. Here, we investigated the inhibitory activity of niclosamide against HIV-1, and determined whether mTORC1 inhibition was involved. The cytotoxicity and anti-HIV-1 activity of niclosamide were tested in TZM-bl and SupT1 cells. Niclosamide showed a dose- and time-dependent inhibitory activity against HIV-1 replication, but the inhibition did not involve the reverse transcription and transcription steps. The mechanism of mTORC1 inhibition was explored by using MHY1485, an mTORC1 activator, to reverse the mTORC1 inhibition, which could partially restore HIV-1 replication. In addition, niclosamide was found to downregulate mTORC1 via AMPK activation, resulting in a decreased phosphorylation of the downstream substrates of S6K and 4EBP1. Niclosamide could also reduce the synthesis of HIV-1 p24 protein. Likewise, MHY-1485 could partially reverse the inhibitory effect of niclosamide by increasing the phosphorylation in the mTORC1 pathway and HIV-1 viral protein synthesis. Our findings, therefore, demonstrated the antiviral mechanism of niclosamide is via the AMPK-mTORC1 pathway, which could be a common therapeutic target for various viruses.

SEROTYPES AND ANTIMICROBIAL RESISTANCE OF SALMONELLA ENTERICA ISOLATED FROM PORK, CHICKEN MEAT AND LETTUCE, BANGKOK AND CENTRAL THAILAND.

Food of animal origins, particularly pork and chicken meat, has long been recognized as major sources of human salmonellosis. There have been recent reports of human salmonellosis outbreaks due to consumption of leafy green vegetables such as lettuce. In this study, 120 (40 pork, 40 chicken meat and 40 lettuce) samples were randomly collected from retail markets in Bangkok and central Thailand during June to August 2015 for Salmonella serotype identification and antimicrobial susceptibility testing. Salmonella was found in 82%, 62% and 20% of pork, chicken meat and lettuce samples, respectively. The top 5 most common Salmonella serotypes were Panama (15%), Schwarzengrund (12%), Rissen, Anatum, and Stanley (11% each), Albany (9%), and Indiana (8%). A high percentage of Salmonella isolated from food of animal origin were resistant to multiple antimicrobial drugs, including ampicillin, chloramphenicol, nalidixic acid, sulfamethoxazole-trimethoprim, and tetracycline. From antibiogram pattern analysis, the most common serotypes constituted isolates that were multidrug resistant. The study indicates that Salmonella was still present in various kinds of food and that certain serotypes have become predominant, a phenomenon not previously reported in Thailand.