Bacteria-mediated cancer therapy has become a topic of interest under the broad umbrella of oncotherapy. Among many bacterial species, Salmonella remains at the forefront due to its ability to localize and proliferate inside tumor microenvironments and often suppress tumor growth. Salmonella Typhimurium is one of the most promising mediators, with engineering plasticity and cancer specificity. It can be used to deliver toxins that induce cell death in cancer cells specifically, and also as a cancer-specific instrument for immunotherapy by delivering tumor antigens and exposing the tumor environment to the host immune system. Salmonella can be used to deliver prodrug converting enzymes unambiguously against cancer. Though positive responses in Salmonella-mediated cancer treatments are still at a preliminary level, they have paved the way for developing combinatorial therapy with conventional chemotherapy, radiotherapy, and surgery, and can be used synergistically to combat multi-drug resistant and higher-stage cancers. With this background, Salmonella-mediated cancer therapy was approved for clinical trials by U.S. Food and Drug Administration, but the results were not satisfactory and more pre-clinical investigation is needed. This review summarizes the recent advancements in Salmonella-mediated oncotherapy in the fight against cancer. The present article emphasizes the demand for Salmonella mutants with high stringency toward cancer and with amenable elements of safety by virulence deletions.

No abstract

With widespread resistance to pentavalent antimonial in the endemic eastern terai belt of Nepal and Bihar, India, Amphotericin B deoxycholate is now the first-line antileishmanial drug for the treatment of visceral leishmaniasis (VL). However, universal occurrence of infusion-related fever and rigors with amphotericin B (AmB), occasional serious life-threatening toxicities like cardiotoxicity, anaphylaxis, hypokalemia, and nephrotoxicity are major barriers to its use in areas with limited medical facilities. Liposomal amphotericins, however, are devoid of adverse effects, high cost makes it unaffordable. We had formulated nanoparticles (10-20 nm) from amphotericin B deoxycholate (1-2 μm) applying high pressure (150 atm) milling homogenization in argon atmosphere and tested its ex vivo efficacy in Leishmania infected J774A cell line and peritoneal macrophage. The ex vivo ED50 for intracellular amastigotes in peritoneal macrophage by nano-amphotericin was 0.0027 ± 0.001 μg/mL which was significantly less (p = 0.0029) than the required dose of amphotericin B (0.0426 ± 0.003 μg/mL). Similarly, in J774A cell line, 50 % of intracellular amastigotes were cleared by 0.0038 ± 0.001 μg/mL of nano-amphotericin while the dose was a bit more for AmB (0.0196 ± 0.001 μg/mL) illustrating the significant difference (p value, 0.0122). The nanoformulation has also shown high efficacy (ED50, 0.0028-0.0035 μg/mL) in inhibition of infected macrophage count. The new formulation accumulated to spleen, the targeted organ, 7 days after inoculation of drug to the infected hamster as traced in vivo by TEM convincing it as potential drug. Given a favorable safety profile and very low cost of production contemplated, it may prove to be a feasible alternative for conventional amphotericin B.

In the present study, two prospective Salmonella delivery strains, JOL2782 and JOL2837, were developed by gene deletions of lon and cpxR, which are related to cellular adhesion and intracellular survival. Additionally, sifA deletion was introduced for JOL2782, which confers immune susceptibility and improves antigen delivery. Similarly, the rfaL deletion and lpxE substitution for pagL were accomplished in JOL2837 to reduce virulence and endotoxicity. Thus, enhanced adhesion and invasion and reduced intracellular survival were attained. Furthermore, aspartic acid auxotrophic (asd) was deleted to impose Darwinian selection on retention of the foreign antigen-expressing plasmid. Both delivery strains induced sufficient cytokine expression, but the level was significantly lower than that of the wild-type strain; the lowest cytokine expression was induced by the JOL2837 strain, indicating reduced endotoxicity. In parallel, IgG production was significantly enhanced by both delivery strains. Thus, the innate and adaptive immunogenicity of the strains was ensured. The environmental safety of these strains was ascertained through faecal dissemination assays. The nonpathogenicity of these strains to the host was confirmed by body weight monitoring, survival assays, and morphological and histological assessments of the vital organs. The in vitro assay in murine and human cell lines and in vivo safety assessments in mice suggest that these novel strains possess safety, invasiveness, and immunogenicity, making them ideal delivery strains. Overall, the results clearly showed that strain JOL2782 with sifA deletion had higher invasiveness, demonstrating superior vaccine deliverability, while JOL2837 with lpxE substitution for pagL and rfaL deletion had outstanding safety potential with drastically abridged endotoxicity.

Peripheral blood mononuclear cells (PBMCs) are commonly used to assess in vitro immune responses. However, PBMC isolation is a time-consuming procedure, introduces technical variability, and requires a relatively large volume of blood. By contrast, whole blood assay (WBA) is faster, cheaper, maintains more physiological conditions, and requires less sample volume, laboratory training, and equipment. Herein, this study aimed to develop a porcine WBA for in vitro evaluation of immune responses. Heparinized whole blood (WB) was diluted (non-diluted, 1/2, 1/8, and 1/16) in RPMI-1640 media, followed by phorbol myristate acetate and ionomycin (PMA/ION) stimulation in humidi ed air at 37°C and 5% CO 2 . After 24 h, cells were stained for IFN-γ secreting T-cells followed by ow cytometry, and the supernatant was analyzed for TNF-α. In addition, diluted WB was stimulated by lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid (poly I:C), eld isolate (FI), reference strain KCTC3557 (RS) of heat-killed (HK) Streptococcus suis, and porcine reproductive and respiratory syndrome virus (PRRSV). Cell surface immune-uorescent staining showed consistent results at all dilutions following stimulation of WB by PMA/ION, while in non-diluted WB, intracellular cytokine staining was obstinate. The frequency of cytotoxic T-cells (CTLs) and concentration of TNF-α in the supernatant of WB increased with increasing dilution factor and were optimal at 1/8. WB TNF-α and IL-10 cytokine levels increased signi cantly following stimulation with LPS or poly I: C. Further, FI and RS induced IL-10 production in WB.Additionally, PRRSV strains increased the frequency of CTLs, and IFN-γ was non-signi cantly induced in the supernatant of re-stimulated samples. We propose that the WBA is a rapid, reliable, and simple method to evaluate immune responses and WB should be diluted to trigger immune cells.