Fluorothiazinon, a small-molecular inhibitor of T3SS, suppresses salmonella oral infection in mice.

Therapeutic strategies that target bacterial virulence have received considerable attention. The type III secretion system (T3SS) is important for bacterial virulence and represents an attractive therapeutic target. Recently, we developed a new small-molecule inhibitor belonging to a class 2,4-disubstituted-4H-[1,3,4]-thiadiazine-5-ones, Fluorothiazinon (FT-previously called CL-55). FT effectively suppressed T3SS of Chlamydia spp., Pseudomonas aeruginosa, and Salmonella without affecting bacterial growth in vitro. FT was previously characterized by low toxicity, stability, and therapeutic efficacy in animal models. Salmonella T3SS inhibition by FT was studied using in vitro assays for effector proteins detection and estimation of salmonella replication in peritoneal macrophages. The antibacterial effect of FT in vivo was investigated in murine models of salmonella chronic systemic and acute infection. Oral administration of the virulent strain of Salmonella enterica serovar Typhimurium to mice-induced chronic systemic infection with the pathogen persistence in different lymphoid organs such as spleens, Peyer's plaques, and mesenteric lymph nodes. We found that FT suppressed orally induced salmonella infection both with therapeutic and prophylactic administration. Treatment by FT at a dose of 50 mg/kg for 4 days starting from day 7 post-infection (therapy) as well as for 4 days before infection (prevention) led to practically complete eradication of salmonella in mice. FT shows a strong potential for antibacterial therapy and could be used as a substance in the design of antibacterial drugs for pharmaceutical intervention including therapy of antibiotic-resistant infections.

Adoptive Immunotherapy Based on Chain-Centric TCRs in Treatment of Infectious Diseases.

Complications after vaccination, lack of vaccines against certain infections, and the emergence of antibiotic-resistant microorganisms point to the need for alternative ways of protection and treatment of infectious diseases. Here, we proposed a therapeutic approach to control salmonellosis based on adoptive cell therapy. We showed that the T cell receptor (TCR) repertoire of salmonella-specific memory cells contains 20% of TCR variants with the dominant-active α-chain. Transduction of intact T lymphocytes with the dominant salmonella-specific TCRα led to their enhanced in vitro proliferation in response to salmonella. Adoptive transfer of transduced T cells resulted in a significant decrease in bacterial loads in mice infected with salmonella before or after the adoptive transfer. We demonstrated that adoptive immunotherapy based on T cells, transduced with dominant-specific TCRα could be successfully applied for treatment and prevention of infectious diseases and represent a useful addition to vaccination and existing therapeutic strategies.

A small-molecule compound belonging to a class of 2,4-disubstituted 1,3,4-thiadiazine-5-ones suppresses Salmonella infection in vivo.

Therapeutic strategies that target bacterial virulence have received considerable attention. The type III secretion system (T3SS) is important for bacterial virulence and represents an attractive therapeutic target. A novel compound with a predicted T3SS inhibitory activity named CL-55 (N-(2,4-difluorophenyl)-4-(3-ethoxy-4-hydroxybenzyl)-5-oxo-5,6-dihydro-4H-[1,3,4]-thiadiazine-2-carboxamide) was previously characterized by low toxicity, high levels of solubility, stability and specific efficiency toward Chlamydia trachomatis in vitro and in vivo. In this study, we describe the action of CL-55 on Salmonella enterica serovar Typhimurium. We found that CL-55 does not affect Salmonella growth in vitro but suppresses Salmonella infection in vivo. The i.p. injection of CL-55 at a dose of 10 mg kg(-1) for 4 days significantly (500-fold) decreased the numbers of Salmonella in the spleen and peritoneal lavages and increased the survival rates in susceptible (BALB/c, I/St) and resistant (A/Sn) mice. Twelve days of therapy led to complete eradication of Salmonella in mice. Moreover, no pathogen was found 4-6 weeks post treatment. CL-55 was not carcinogenic or mutagenic, did not increase the level of chromosomal aberrations in bone marrow cells and had low toxicity in mice, rats and rabbits. Pharmacokinetic studies have shown that CL-55 rapidly disappears from systemic blood circulation and is distributed in the organs. Our data demonstrates that CL-55 affects S. enterica serovar Typhimurium in vivo and could be used as a substance in the design of antibacterial inhibitors for pharmaceutical intervention of bacterial virulence for infection.