Alternative to Animal Use for Detecting Biologically Active Staphylococcal Enterotoxin Type A

Streptococcal pyrogenic exotoxin B is a superantigen that induces murine splenocyte proliferation and secretion of IL-2 and IFN-γ ex vivo

Streptococcus pyogenes is a significant human pathogen, producing a range of virulence factors, including streptococcal pyrogenic exotoxin B (SpeB) that is associated with foodborne outbreaks. It was only known that this cysteine protease mediates cleavage of transmembrane proteins to permit bacterial penetration and is found in 25% of clinical isolates from streptococcal toxic shock syndrome patients with extreme inflammation. Its interaction with host and streptococcal proteins has been well characterized, but doubt remains about whether it constitutes a superantigen. In this study, for the first time it is shown that SpeB acts as a superantigen, similarly to other known superantigens such as staphylococcal enterotoxin A or streptococcal pyrogenic exotoxin type C, by inducing proliferation of murine splenocytes and cytokine secretion, primarily of interleukin-2 (IL-2), as shown by cytometric bead array analysis. IL-2 secretion was confirmed by enzyme-linked immunosorbent assay (ELISA) as well as secretion of interferon-γ. ELISA showed a dose-dependent relationship between SpeB concentration in splenocyte cells and IL-2 secretion levels, and it was shown that SpeB retains activity in milk pasteurized for 30 min at 63°C.

Development of Thermally Stable Nanobodies for Detection and Neutralization of Staphylococcal Enterotoxin B

In this study, sixteen unique staphylococcal enterotoxin B (SEB)-reactive nanobodies (nbs), including ten monovalent and six bivalent nbs, were developed. All characterized nbs were highly specific for SEB and did not cross-react with other staphylococcal enterotoxins (SE). Several formats of highly sensitive enzyme-linked immunosorbent assays (ELISAs) were established using SEB nbs and a polyclonal antibody (pAb). The lowest limit of detection (LOD) reached 50 pg/mL in PBS. When applied to an ELISA to detect SEB-spiked milk (a commonly contaminated foodstuff), a LOD as low as 190 pg/mL was obtained. The sensitivity of ELISA was found to increase concurrently with the valency of nbs used in the assay. In addition, a wide range of thermal tolerance was observed among the sixteen nbs, with a subset of nbs, SEB-5, SEB-9, and SEB-6², retaining activity even after exposure to 95 °C for 10 min, whereas the conventional monoclonal and polyclonal antibodies exhibited heat-labile properties. Several nbs demonstrated a long shelf-life, with one nb (SEB-9) retaining 93% of its activity after two weeks of storage at room temperature. In addition to their usage in toxin detection, eleven out of fifteen nbs were capable of neutralizing SEB's super-antigenic activity, demonstrated by their inhibition on IL-2 expression in an ex vivo human PBMC assay. Compared to monoclonal and polyclonal antibodies, the nbs are relatively small, thermally stable, and easy to produce, making them useful in applications for sensitive, specific, and cost-effective detection and management of SEB contamination in food products.

Ex Vivo and In Vitro Methods for Detection of Bioactive Staphylococcal Enterotoxins

Staphylococcus aureus is a major bacterial cause of clinical infections and foodborne illnesses.Through the synthesis of a group of Staphylococcal enterotoxins (SEs), gastroenteritis occurs and the SEs function as superantigens to massively activate T cells. The ability to rapidly detect and quantify SEs is imperative in order to learn the causes of staphylococcal outbreaks and to stop similar outbreaks in the future. Also, the ability to discern active toxin is essential for development of food treatment and processing methods. Here, we discuss the various methodologies for detection and analysis of SEs.

Crocetin attenuating Urinary tract Infection and adherence of uropathogenic E. coli in NRK-52E cells via an inflammatory pathway

BACKGROUND AND OBJECTIVE

Urinary tract infections (UTI) are commonly treated with broad-spectrum antibiotics, but treatment has limitation due to causes of nephrotoxicity in uroepithelial cells. Recently, the researcher focuses their research on alternative therapy for the treatment of UTI. This study evaluated the anti-infectious effect of crocetin against adherence of pathogenic [2-¹⁴ C]-acetate labeled Escherichia coli (MTCC-729) to rat proximal renal tubular cells (NRK-52E cells) and explores the possible mechanism of action.

MATERIALS AND METHODS

In vitro cytotoxicity and radio acetate labeled tests were performed on NRK-52E cells. The rats were divided into five different groups as follows: normal control (NC), disease control (DC), and various doses of crocetin (1.25, 2.5, and 5 mg/kg) treated group rats. White blood cells in blood, urine, and bacterial colony counts were estimated at regular intervals. Pro-inflammatory cytokines, such as interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), interleukin-10 (IL-10), and interleukin-8 (IL-8), were also estimated. In the current study, we estimated the mRNA expression of toll-like receptor-4 (TLR-4) and toll-like receptor-2 (TLR-2) in the renal and bladder tissues.

RESULTS

Crocetin significantly (p < .05) inhibited the adherence of E. Coli in NRK-52E cells. Crocetin suppresses the lipid peroxidation (LPO) 42% in cells treated with H₂ O₂ cells without crocetin. The white blood cells (WBC) count in blood and urine were augmented and crocetin treatment significantly (p < .05) reduced the WBC in urine and blood. The pro-inflammatory cytokines, such as IL-6, MCP-1, IL-10, and IL-8, significantly (p < .05) increased in the DC group and crocetin significantly (p < .05) reduced the pro-inflammatory cytokines. Dose-dependent treatment of crocetin significantly reduced the mRNA expression of TLR2 and TLR4 in the renal and bladder tissues.

CONCLUSION

Crocetin considerably reduced the bacterial adherence to NRK-52E cells, attenuated the H₂ O₂ induced toxicity in NRK-52E cells and also improved the renal tubular function, and reduced the inflammatory response via altering the inflammatory and antioxidant markers.

PRACTICAL APPLICATION

As we all know that urinary tract infection is the most common disease worldwide. In this study, we scrutinized the protective effect of crocetin against urinary tract infection. Crocetin treatment considerably reduced the zone of inhibition and improved radioactivity. Crocetin significantly reduced the levels of cytokines and inflammatory mediators. Crocetin can be used as a protective drug in the treatment of urinary tract infections.

Human Leukemia T-Cell Lines as Alternatives to Animal Use for Detecting Biologically Active Staphylococcal Enterotoxin Type B

Staphylococcal enterotoxin type B (SEB) is associated with food poisoning. Current methods for the detection of biologically active SEB rely upon its ability to cause emesis when administered to live kittens or monkeys. This technique suffers from poor reproducibility and low sensitivity and is ethically disfavored over concerns for the welfare of laboratory animals. The data presented here show the first successful implementation of an alternative method to live animal testing that utilizes SEB super-antigenic activity to induce cytokine production for specific novel cell-based assays for quantifiable detection of active SEB. Rather than using or sacrificing live animals, we found that SEB can bind to the major histocompatibility complex (MHC) class II molecules on Raji B-cells. We presented this SEB–MHC class II complex to specific Vβ5.3 regions of the human T-cell line HPB-ALL, which led to a dose-dependent secretion of IL-2 that is capable of being quantified and can further detect 10 pg/mL of SEB. This new assay is 100,000 times more sensitive than the ex vivo murine splenocyte method that achieved a detection limit of 1 µg/mL. The data presented here also demonstrate that SEB induced proliferation in a dose-dependent manner for cells obtained by three different selection methods: by splenocyte cells containing 22% of CD4⁺ T-cells, by CD4⁺ T-cells enriched to >90% purity by negative selection methods, and by CD4⁺ T-cells enriched to >95% purity by positive selection methods. The highly enriched and positively isolated CD4⁺ T-cells with the lowest concentration of antigen-presenting cells (APC) (below 5%) provided higher cell proliferation than the splenocyte cells containing the highest concentration of APC cells.