Δ9-Tetrahydrocannabinol Prevents Mortality from Acute Respiratory Distress Syndrome through the Induction of Apoptosis in Immune Cells, Leading to Cytokine Storm Suppression.

Acute Respiratory Distress Syndrome (ARDS) causes up to 40% mortality in humans and is difficult to treat. ARDS is also one of the major triggers of mortality associated with coronavirus-induced disease (COVID-19). We used a mouse model of ARDS induced by Staphylococcal enterotoxin B (SEB), which triggers 100% mortality, to investigate the mechanisms through which Δ9-tetrahydrocannabinol (THC) attenuates ARDS. SEB was used to trigger ARDS in C3H mice. These mice were treated with THC and analyzed for survival, ARDS, cytokine storm, and metabolome. Additionally, cells isolated from the lungs were used to perform single-cell RNA sequencing and transcriptome analysis. A database analysis of human COVID-19 patients was also performed to compare the signaling pathways with SEB-mediated ARDS. The treatment of SEB-mediated ARDS mice with THC led to a 100% survival, decreased lung inflammation, and the suppression of cytokine storm. This was associated with immune cell apoptosis involving the mitochondrial pathway, as suggested by single-cell RNA sequencing. A transcriptomic analysis of immune cells from the lungs revealed an increase in mitochondrial respiratory chain enzymes following THC treatment. In addition, metabolomic analysis revealed elevated serum concentrations of amino acids, lysine, n-acetyl methionine, carnitine, and propionyl L-carnitine in THC-treated mice. THC caused the downregulation of miR-185, which correlated with an increase in the pro-apoptotic gene targets. Interestingly, the gene expression datasets from the bronchoalveolar lavage fluid (BALF) of human COVID-19 patients showed some similarities between cytokine and apoptotic genes with SEB-induced ARDS. Collectively, this study suggests that the activation of cannabinoid receptors may serve as a therapeutic modality to treat ARDS associated with COVID-19.

Staphylococcal enterotoxins as good candidates for cancer immunotherapy: a systematic review.

BACKGROUND: Cancer is considered as one of the leading causes of death today. The wrong lifestyles have led to an increase in the incidence rate of this deadly disease. There are many complications associated with common treatments of this disease. Immunotherapy is one of the new approaches taken recently. The purpose of this systematic review was to evaluate the studies on Staphylococcus aureus enterotoxins as a treatment of cancer worldwide. STUDY DESIGN: We conducted a systematic review of articles published in PubMed, Cochrane, Scopus and Google scholar databases from 1995 to 2016 to evaluate the effects of Staphylococci enterotoxins on cancer. METHODS: Eligible studies were evaluated qualitatively based on a checklist prepared by two independent reviewers, and they were subsequently matched. RESULTS: Our review identified 97 records through searching PubMed and Cochrane database and 1306 records through searching Google scholar and Scopus. Forty six studies were excluded from PubMed and Cochrane database and 1281 studies were excluded from Google scholar and Scopus after screening abstracts and titles. Therefore, our systematic review was based on 51 publications on PubMed and Cochrane, and 25 publications on Google scholar and Scopus, which met our criteria. Staphylococcal enterotoxin A was the most commonly used toxin in these studies. The side effects of using this toxin in immunotherapy have been reported to be low and all studies have identified this toxin as a suitable option for immunotherapy. CONCLUSIONS: The data obtained from these studies showed that due to the low rates of complications, Staphylococcal enterotoxins have the potential to induce immune system against various cancers as super-antigens. Therefore, they can be considered as a suitable candidate for immunotherapy of cancer.

Sensitisation to staphylococcal enterotoxins and asthma severity: a longitudinal study in the EGEA cohort.

INTRODUCTION: Evidence is accumulating that Staphylococcus aureus plays an important role as disease modifier in upper and lower airway diseases. Sensitisation to S. aureus enterotoxins (SEs) was associated with an increased risk of severe asthma in previous cross-sectional studies, but evidence from longitudinal studies is lacking. We aimed to assess associations between SE-sensitisation and the subsequent risk for asthma severity and exacerbations. METHODS: This is a nested case-control study from the 20-year Epidemiological Study of the Genetics and Environment of Asthma (EGEA) cohort, including 225 adults (75 without asthma, 76 with mild asthma and 74 with severe asthma) in EGEA2 (2003-2007). For 173 of these individuals, SE-sensitisation was measured on samples collected 11 years earlier (EGEA1). Cross-sectional associations were conducted for EGEA1 and EGEA2. Longitudinal analyses estimated the association between SE-sensitisation in EGEA1 and the risk of severe asthma and asthma exacerbations assessed in the follow-up. Models were adjusted for sex, age, smoking, parental asthma/allergy and skin-prick test to house dust mite. RESULTS: SE-sensitisation varied between 39% in controls to 58% and 76% in mild and severe asthma, respectively, in EGEA1. An adjusted cross-sectional association showed that SE-sensitisation was associated with an increased risk of severe, but not for mild asthma. SE-sensitisation in EGEA1 was associated with severe asthma (adjusted OR 2.69, 95% CI 1.18-6.15) and asthma exacerbations (adjusted OR 4.59, 95% CI 1.40-15.07) assessed 10-20 years later. CONCLUSION: For the first time, this study shows that being sensitised to SEs is associated with an increased subsequent risk of severe asthma and asthma exacerbations.

Zinc alleviates arsenism in common carp: Varied change profiles of cytokines and tight junction proteins among two intestinal segments.

This study was designed to evaluate the effects of zinc on inflammation and tight junction (TJ) in different intestinal regions of common carp under sub-chronic arsenic insult. Fish were exposed to zinc (0, 1 mg/L) and arsenic trioxide (0, 2.83 mg/L) in individual or combination for a month. Inflammatory infiltration and TJ structure changes were displayed by H&E staining and transmission electron microscope. To further explore these changes, biochemical indicator (SOD), gene or protein expressions of inflammatory responses (NF-κB, IL-1ß, IL-6 and IL-8) and TJ proteins (Occludin, Claudins and ZOs) were determined. In the anterior intestine, arsenic decreased activity of SOD, mRNA levels of Occludin, Claudins and ZOs, increased mRNA levels of ILs. However, unlike the anterior intestine, arsenic has an upregulation effects of Occludin and Claudin-4 in the mid intestine. These anomalies induced by arsenic, except IL-8, were completely or partially recovered by zinc co-administration. Furthermore, transcription factor (NF-κB) nuclear translocation paralleled with its downstream genes in both intestinal regions. In conclusion, our results unambiguously suggested that under arsenic stress, zinc can partly relieve intestinal inflammation and disruption of tight junction segment-dependently.

Reduction of Murine Colon Tumorigenesis Driven by Enterotoxigenic Bacteroides fragilis Using Cefoxitin Treatment.

BACKGROUND: Chronic inflammation and composition of the colon microbiota have been associated with colorectal cancer in humans. The human commensal enterotoxigenic Bacteroides fragilis (ETBF) is linked to both inflammatory bowel disease and colorectal cancer and, in our murine model, causes interleukin 17A (IL-17A)-dependent colon tumors. In these studies, we hypothesized that persistent colonization by ETBF is required for tumorigenesis. METHODS: We established a method for clearing ETBF in mice, using the antibiotic cefoxitin. Multiple intestinal neoplasia mice were colonized with ETBF for the experiment duration or were cleared of infection after 5 or 14 days. Gross tumors and/or microadenomas were then evaluated. In parallel, IL-17A expression was evaluated in wild-type littermates. RESULTS: Cefoxitin treatment resulted in complete and durable clearance of ETBF colonization. We observed a stepwise increase in median colon tumor numbers as the duration of ETBF colonization increased before cefoxitin treatment. ETBF eradication also significantly decreased mucosal IL-17A expression. CONCLUSIONS: The timing of ETBF clearance profoundly influences colon adenoma formation, defining a period during which the colon is susceptible to IL-17A-dependent tumorigenesis in this murine model. This model system can be used to study the microbiota-dependent and molecular mechanisms contributing to IL-17A-dependent colon tumor initiation.

Assessment of the performance of three multiplex array panels for the detection of circulating cytokines and chemokines in naive, LPS, and SEB-treated cynomolgus macaques.

To assess relative sensitivity for detection of cytokines and chemokines in cynomolgus serum samples, we tested three commercially available multiplex array kits using the Luminex® platform with sera from animals exposed by intravenous injection to 150 µg/kg staphylococcal enterotoxin B (SEB) or 20 µg/kg lipopolysaccharide (LPS). Each of these kits detected similar patterns of changes in circulating cytokines/chemokines in response to SEB or LPS stimulation, especially the induction of high amounts of interleukin (IL)-2 and interferon-gamma (IFN-γ) in response to SEB but not LPS. However, there were clear differences in sensitivity for particular analytes, especially for IL-10. Additional experiments that focused on one multiplex array kit demonstrated very low or undetectable levels of cytokines in naive cynomolgus macaques, except for highly variable background levels of IL-8, monocyte chemoattractant protein-1, and macrophage inflammatory protein-1ß. Therefore, multiplex array analysis of circulating cytokine/chemokine patterns was capable of detection of systemic activation of diverse immune cell subsets.

The A subunit of Escherichia coli heat-labile enterotoxin functions as a mucosal adjuvant and promotes IgG2a, IgA, and Th17 responses to vaccine antigens.

Enterotoxigenic Escherichia coli (ETEC) produces both heat-labile (LT) and heat-stable (ST) enterotoxins and is a major cause of diarrhea in infants in developing countries and in travelers to those regions. In addition to inducing fluid secretion, LT is a powerful mucosal adjuvant capable of promoting immune responses to coadministered antigens. In this study, we examined purified A subunit to further understand the toxicity and adjuvanticity of LT. Purified A subunit was enzymatically active but sensitive to proteolytic degradation and unable to bind gangliosides, and even in the presence of admixed B subunit, it displayed low cyclic AMP (cAMP) induction and no enterotoxicity. Thus, the AB5 structure plays a key role in protecting the A subunit from proteolytic degradation and in delivering the enzymatic signals required for secretion. In contrast, the A subunit alone was capable of activating dendritic cells and enhanced immune responses to multiple antigens following intranasal immunization; therefore, unlike toxicity, LT adjuvanticity is not dependent on the AB5 holotoxin structure or the presence of the B subunit. However, immune responses were maximal when signals were received from both subunits either in an AB5 structure or with A and B admixed. Furthermore, the quality of the immune response (i.e., IgG1/IgG2 balance and mucosal IgA and IL-17 secretion) was determined by the presence of an A subunit, revealing for the first time induction of Th17 responses with the A subunit alone. These results have important implications for understanding ETEC pathogenesis, unraveling immunologic responses induced by LT-based adjuvants, and developing new mucosal vaccines.

Staphylococcal-derived superantigen enhances peanut induced Th2 responses in the skin.

BACKGROUND: The allergen-induced activation and expansion of IL-4 producing T helper type 2 (Th2) cells is a key event in the initiation and progression of allergic disease. Intriguingly, concomitant early childhood staphylococcal skin infections are being increasingly implicated in the allergen-induced switch of primary T cell responses towards the Th2 phenotype. OBJECTIVE: We sought to identify whether or not staphylococcal-derived superantigen can influence the primary T cell response in the skin to food allergens with a view to determining whether such exposures create the immune pathology that predisposes to the development of food allergy. METHODS: Using a novel Th2 reporter model, we determined the ability of the staphylococcal superantigen (SEB) to influence priming in the skin of IL-4 expressing Th2 cells by peanut extract (PE). Factors including the effect of SEB on the magnitude of the Th2 response in the skin draining lymph nodes, T cell receptor V region usage and the influence of endotoxin were evaluated. RESULTS: Primary exposure to PE and SEB lead to significantly enhanced PE specific Th2 responses when the mice were subsequently exposed to PE alone. The enhancement of the Th2 response was dependent on the Vß-binding properties of the SEB, but was not affected by endotoxin-mediated TLR-4 effects or strain differences in the mice. CONCLUSIONS AND CLINICAL RELEVANCE: These results identify that in the skin environment, the presence of SEB can significantly increase the numbers of allergen-induced Th2 cells which develop in response to subsequent allergen exposure. These data highlight the process by which individuals may become pathologically sensitized to food allergens in early life.

Bacillus cereus Toxins.

Bacillus cereus sensu stricto is an important pathogen causing food poisoning, as well as extraintestinal diseases [...].

[Studies on the biological activities and emetic mechanism of staphylococcal enterotoxins].

Staphylococcus aureus food poisoning was shown by Dack et al. in 1930 to be caused by staphylococcal enterotoxin (SE) produced by S. aureus, rather than by the bacterial infection. However, the emetic mechanism of SE has remained unclear. In this study, we analyzed the emetic activity of SE in several emetic animal models and tried to elucidate the mechanism of emesis. We established a small primate, common marmoset, as a novel emetic model for SE. We also analyzed the immunofluorescence analysis of the gastrointestinal tract of the common marmoset and found that SE binds to submucosal mast cells in the gastrointestinal tract and SE induces degranulation of the mast cells. Furthermore, we showed that SE induces histamine releases, which is inhibited by mast cell stabilizer. In addition, treatment of common marmosets with either mast cell stabilizer or histamine H1 receptor antagonists suppressed the emetic response induced by SE. These results indicate that orally administered SE binds to submucosal mast cells in the gastrointestinal tract and causes degranulation, resulting in the release of histamine, which in turn causes emesis.

The safety of a mucosal vaccine using the C-terminal fragment of Clostridium perfringens enterotoxin.

The C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE) is a claudin-4 binder. Very recently, we found that nasal immunization of mice with C-CPE-fused antigen activated antigen-specific humoral and mucosal immune responses and that the deletion of the claudin-4-binding domain attenuated the immune responses. C-CPE-fusion strategy may be useful for mucosal vaccination. C-CPE is a fragment of enterotoxin, and the safety of C-CPE-fused protein is very important for its future application. In the present study, we investigated whether C-CPE-fused antigen induces immune responses without mucosal injury by using ovalbumin (OVA) as a model antigen. Immunohistochemical analysis showed that claudin-4 was expressed in epithelial cell sheets bordering the nasal cavity. Nasal immunization with C-CPE-fused OVA dose-dependently elevated the OVA-specific serum IgG titer, which was 1000-fold greater than the titer achieved by immunization with OVA or a mixture of OVA and C-CPE at 5 microg of OVA. Nasal immunization with C-CPE-fused OVA (5 microg of OVA) activated Th1 and Th2 responses. Histological analysis showed no mucosal injury in the nasal cavity or nasal passage. C-CPE-fused OVA exhibited mucosal vaccination without mucosal injury. These findings indicate thatclaudin-4-targeting using C-CPE can be a potent strategy for mucosal vaccination.

Monomicrobial Fournier's Gangrene Caused by Panton-Valentine Leukocidin-negative Methicillin-susceptible Staphylococcus aureus ST8 in Japan.

Methicillin-resistant Staphylococcus aureus USA300, belonging to sequence type (ST) 8, is a rare cause of necrotizing fasciitis in the USA. We herein report a case of monomicrobial Fournier's gangrene caused by an ST8, methicillin-susceptible Staphylococcus aureus (designated ksw1). Whole-genome sequencing and analyses for virulence determinants revealed that, unlike USA300, ksw1 lacked virulence genes, such as Panton-Valentine leukocidin and SCCmec, while harboring the toxic shock syndrome toxin-1 gene. These genomic features correlate with ST8 CA-MRSA/J, which is the major genotype of ST8 in Japan.

Structure and Function of Bovine Whey Derived Oligosaccharides Showing Synbiotic Epithelial Barrier Protective Properties.

Commensal gut microbiota and probiotics have numerous effects on the host's metabolic and protective systems, which occur primarily through the intestinal epithelial cell interface. Prebiotics, like galacto-oligosaccharides (GOS) are widely used to modulate their function and abundance. However, important structure-function relations may exist, requiring a detailed structural characterization. Here, we detailed the structural characterization of bovine whey derived oligosaccharide preparations enriched with GOS or not, dubbed GOS-enriched milk oligosaccharides (GMOS) or MOS, respectively. We explore GMOS's and MOS's potential to improve intestinal epithelial barrier function, assessed in a model based on barrier disruptive effects of the Clostridioides difficile toxin A. GMOS and MOS contain mainly GOS species composed of ß1-6- and ß1-3-linked galactoses, and 3'- and 6'-sialyllactose. Both GMOS and MOS, combined with lactobacilli, like Lactobacillus rhamnosus (LPR, NCC4007), gave synergistic epithelial barrier protection, while no such effect was observed with Bifidobacterium longum (BL NCC3001), Escherichia coli (Nissle) or fructo-oligosaccharides. Mechanistically, for barrier protection with MOS, (i) viable LPR was required, (ii) acidification of growth medium was not enough, (iii) LPR did not directly neutralize toxin A, and (iv) physical proximity of LPR with the intestinal epithelial cells was necessary. This is the first study, highlighting the importance of structure-function specificity and the necessity of the simultaneous presence of prebiotic, probiotic and host cell interactions required for a biological effect.

Cerebral gene expression of superantigen encephalitis in the lewis rat induced by staphylococcal enterotoxin a.

Superantigens were suggested to play a role in the pathogenesis of different autoimmune diseases including multiple sclerosis (MS). Previously, it was demonstrated that local expression of the superantigen, staphylococcal enterotoxin A (SEA) in the brain of rats may lead to encephalitis which was amplified by using intravenous injection of concanavalin A (ConA)-activated splenocytes. In the present investigation, gene expression was studied in the rat brain 8 days after an injection of 50 mul of 1 mg/ml SEA or saline and 5 days after an intravenous injection of 1 x 10(7) ConA-activated spleen cells. Of 8800 genes investigated (Affymetrix, rat genome U34A), the expression of 106 genes was significantly and at least threefold increased with SEA, while the expression of 29 genes was decreased at least threefold. Increased gene expression was compatible with an intracerebral inflammatory response mediated by antigen-presenting cells and CD8+ T lymphocytes. Elevated chemokines comprised RANTES (CCL5), osteopontin, MCP-1 (CCL2) and CXCL10. Further, genes with increased expression were assigned to the extracellular matrix, microglia/macrophage cell elements, astrocytes (GFAP) and phagocytosis. There was considerable conformity between previously reported gene expression profiles for experimental autoimmune encephalomyelitis (EAE) or MS and the present findings. Our data are in line with the concept that T-cell superantigen locally expressed in the central nervous system induces an inflammatory response. Therefore, the study of gene expression profiles does not seem to allow clear conclusions with respect to the aetiology of central nervous system autoimmune diseases.

Computer aided boar semen motility analysis for cereulide detection in different food matrices.

Computer Aided Semen Analysis (CASA) study of the boar semen motility has been demonstrated to be an appropriate assay for detection of cereulide (Bacillus cereus emetic toxin). Application of the boar semen bio-assay to detect cereulide directly in foods requires investigation of potential interference of food components, preservatives and other microbial and chemical food contaminants with the bio-assay. Current study provides evidence that none of included Staphylococcus aureus enterotoxins A, B, C and D nor B. cereus Hemolysin BL (HBL) and non-hemolytic enterotoxin (NHE) and three mycotoxins (Sterigmatocystin, Fumonisin B1 and Patulin) exhibited a toxic impact on semen progressive motility. Aflatoxin M1, M3 and zearalenone impaired semen motility only at concentrations (0.004 mg ml(-1), 0.1 mg ml(-1) and 10 mg ml(-1), respectively) much higher than those found in foods and those permitted by legislation, in comparison to cereulide which induces motility cease at concentrations lower than 20 ng ml(-1). Ten commonly used preservatives, namely potassium sorbate, sodium benzoate, (DL) malic acid, citric acid, (L+) tartaric acid, acetic acid, (DL) lactic acid, (L+) ascorbic acid, sodium chloride and sucrose induced no cease in spermatozoa motility even at preservative concentrations higher than permitted by legislation. Dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and acrylamide had no acute effect on spermatozoa motility at concentrations of 500 and 10,000 mg ml(-1), respectively. Robustness of computer aided boar semen motility analysis, tested with 14 different foods inoculated with cereulide producing B. cereus, showed distinct cereulide production in seven samples (although B. cereus growth to counts higher than 8 log CFU g(-1) was noted in 11 samples), in amounts close to those reported in foodborne outbreaks. Test evaluation in 33 samples suspected to hold cereulide showed actual cereulide presence in ten samples and no interference of food matrix with the assay.

BL22 and lymphoid malignancies.

BL22 is a recombinant immunotoxin containing a truncated form of the bacterial toxin Pseudomonas exotoxin A attached to an Fv fragment of an anti-CD22 monoclonal antibody. Its mechanism of action involves binding to CD22, being internalized into the target cell by endocytosis, being processed to generate a free toxin fragment which is translocated into the cytoplasm, and finally induction of cell death by catalytic inactivation of elongation factor 2. In phase-I testing BL22 was very active in chemoresistant hairy-cell leukemia (HCL), with 19 (61%) of 31 patients achieving complete remission (CR). The low blood counts (cytopenias) which are characteristic of HCL improved in all complete and partial responders. Dose-limiting toxicity in HCL was due to a reversible hemolytic uremic syndrome (HUS), observed only during cycles 2 or 3. Already under way are a phase-II trial in HCL and phase-I trials in chronic lymphocytic leukemia (CLL) and acute lymphocytic leukemia (ALL) administering BL22 in a modified protocol in an effort to prevent HUS.

Monkey Feeding Assay for Testing Emetic Activity of Staphylococcal Enterotoxin.

Staphylococcal enterotoxins (SEs) are unique bacterial toxins that cause gastrointestinal toxicity as well as superantigenic activity. Since systemic administration of SEs induces superantigenic activity leading to toxic shock syndrome that may mimic enterotoxic activity of SEs such as vomiting and diarrhea, oral administration of SEs in the monkey feeding assay is considered as a standard method to evaluate emetic activity of SEs. This chapter summarizes and discusses practical considerations of the monkey feeding assay used in studies characterizing classical and newly identified SEs.

A Randomized Phase II/III Study of Naptumomab Estafenatox + IFNα versus IFNα in Renal Cell Carcinoma: Final Analysis with Baseline Biomarker Subgroup and Trend Analysis.

PURPOSE: To prospectively determine the efficacy of naptumomab estafenatox (Nap) + IFNα versus IFN in metastatic renal cell carcinoma (RCC). EXPERIMENTAL DESIGN: In a randomized, open-label, multicenter, phase II/III study, 513 patients with RCC received Nap (15 µg/kg i. v. in three cycles of four once-daily injections) + IFN (9 MU s.c. three times weekly), or the same regimen of IFN monotherapy. The primary endpoint was overall survival (OS). RESULTS: This phase II/III study did not meet its primary endpoint. Median OS/PFS for Nap + IFN patients was 17.1/5.8 months versus 17.5/5.8 months for the patients receiving IFN alone (P = 0.56; HR, 1.08/P = 0.41; HR, 0.92). Post hoc exploratory subgroup and trend analysis revealed that the baseline plasma concentrations of anti-SEA/E-120 (anti-Nap antibodies) for drug exposure and IL6 for immune status could be used as predictive biomarkers. A subgroup of patients (SG; n = 130) having concentrations below median of anti-SEA/E-120 and IL6 benefitted greatly from the addition of Nap. In SG, median OS/PFS for the patients treated with Nap + IFN was 63.3/13.7 months versus 31.1/5.8 months for the patients receiving IFN alone (P = 0.02; HR, 0.59/P = 0.02; HR, 0.62). Addition of Nap to IFN showed predicted and transient immune related AEs and the treatment had an acceptable safety profile. CONCLUSIONS: The study did not meet its primary endpoint. Nap + IFN has an acceptable safety profile, and results from post hoc subgroup analyses showed that the treatment might improve OS/PFS in a baseline biomarker-defined RCC patient subgroup. The results warrant further studies with Nap in this subgroup. Clin Cancer Res; 22(13); 3172-81. ©2016 AACR.

The molecular mechanisms of severe typhoid fever.

Salmonella typhi continues to cause severe disease in many parts of the world, its most feared complication being perforation of ulcerated Peyer's patches within the small intestine, leading to peritonitis with associated mortality. The pathogenesis of this process is not well understood. In this article, we present a theoretical mechanism as to how bacterial factors and host immunological mediators within infected tissue might contribute to the observed intestinal pathology, and propose that necrosis of the Peyer's patches observed in typhoid is caused by a mechanism similar to the Shwartzman and Koch reactions.

Superantigen-based immunotherapy: a phase I trial of PNU-214565, a monoclonal antibody-staphylococcal enterotoxin A recombinant fusion protein, in advanced pancreatic and colorectal cancer.

PURPOSE: To establish the maximum-tolerated dose (MTD) and define the toxicities of a single-dose infusion of PNU-214565, a recombinant Escherichia coli-derived fusion protein of Staphylococcal enterotoxin A (SEA) and the Fab-fragment of the C242 monoclonal antibody in patients with advanced colorectal and pancreatic carcinomas. To investigate the capability of PNU-214565 to induce a superantigen (SAg) response resulting in cytokine production and tumor regression. PATIENTS AND METHODS: Twenty-one patients (age range, 39 to 76 years; median, 64; 12 men, nine women; 18 colorectal, three pancreatic cancers) were treated with a single 3-hour infusion of PNU-214565, with doses ranging from 0.01 to 1.5 ng/kg. All patients had prior chemotherapy and a good performance status Eastern Cooperative Oncology Group [ECOG] performance status [PS] = 0 [n = 10]; PS = 1 [n = 11]), 10 had prior radiation, and 18 had prior surgery. RESULTS: Fever and hypotension were the most common toxicities. Fever of any grade occurred in 16 of 21 patients (76%): four of 21 (19%) with grade 2 and two of 21 (9.5%) with grade 3. Hypotension of any grade occurred in 13 of 21 (62%): four of 21 with grade 2 and one of 21 (5%) with grade 3. Interleukin-2 (IL-2) and tumor necrosis factor alpha (TNF alpha) induction correlated with toxicity. In the two patients with grade 3 fever, peak IL-2 and TNF alpha levels were 2.9 IU/mL and 165 pg/mL, and 8.3 IU/mL and 245 pg/mL, respectively. Transient, > or = 50% decreases in circulating monocytes were observed in 17 of 21 patients as early as 0.5 hours (median time, 2 hours) from the start of infusion. Decreases (mean 33%) in circulating lymphocytes were observed in seven of 21 patients. All three patients with grade 3 toxicity were treated at the 0.5-ng/kg dose. The significance of baseline anti-SEA, human antimouse antibody (HAMA), CA242-soluble antigen levels, and T-cell receptor variable beta region (TCR V beta) subsets and histocompatibility leukocyte antigen-DR (HLA-DR) genotypes was assessed as possible predictors of toxicity. All toxicities were transient and easily managed. No grade 3 toxicity occurred at the higher dose levels. CONCLUSION: PNU-214565, a SAg-based tumor targeted therapy, is safe when given as a single 3-hour infusion at doses up to 1.5 ng/kg. The MTD for a single dose was not determined. The safety of a repeated dose schedule is currently under investigation, beginning with doses determined to be safe in this trial.