The ability of genetically detoxified lipopolysaccharide (LPS) to stimulate adaptive immune responses is an ongoing area of investigation with significant consequences for the development of safe and effective bacterial vaccines and adjuvants. One approach to genetic detoxification is the deletion of genes whose products modify LPS. The msbB1 and msbB2 genes, which encode late acyltransferases, were deleted in the Shigella flexneri 2a human challenge strain 2457T to evaluate the virulence, inflammatory potential, and acquired immunity induced by strains producing underacylated lipid A. Consistent with a reduced endotoxic potential, S. flexneri 2a msbB mutants were attenuated in an acute mouse pulmonary challenge model. Attenuation correlated with decreases in the production of proinflammatory cytokines and in chemokine release without significant changes in lung histopathology. The levels of specific proinflammatory cytokines (interleukin-1␤ [IL-1␤], macrophage inflammatory protein 1␣ [MIP-1␣], and tumor necrosis factor alpha [TNF-␣]) were also significantly reduced after infection of mouse macrophages with either single or double msbB mutants. Surprisingly, the msbB double mutant displayed defects in the ability to invade, replicate, and spread within epithelial cells. Complementation restored these phenotypes, but the exact nature of the defects was not determined. Acquired immunity and protective efficacy were also assayed in the mouse lung model, using a vaccination-challenge study. Both humoral and cellular responses were generally robust in msbB-immunized mice and afforded significant protection from lethal challenge. These data suggest that the loss of either msbB gene reduces the endotoxicity of Shigella LPS but does not coincide with a reduction in protective immune responses.Shigellosis, or bacillary dysentery, is an acute colitis caused by Shigella flexneri, a gram-negative enteroinvasive bacterium that is transmitted to humans via the fecal-oral route. Shigella triggers its uptake into the M cells of the lower intestine, where they are taken up by the underlying antigen-presenting cells (macrophages and dendritic cells) (18). Shigella bacteria are released from macrophages after inducing cell death (12,29) and invade the surrounding enterocytes, where they begin to multiply and spread to adjacent cells. Effector proteins secreted through a molecular-needle-like complex called the type III secretion system (TTSS) mediate the processes of macrophage cytotoxicity, enterocyte invasion, and modulation of the host cell immune response. The TTSS and associated effector proteins are encoded on a large virulence plasmid that is present in all invasive strains of Shigella (46). During replication and dissemination in host cells, components of the bacterial cell wall (lipopolysaccharide [LPS] and peptidoglycan) are released, inducing proinflammatory cytokines and chemokines which activate the innate immune response (reviewed in reference 31). Although the immune mechanisms of protection remain relatively undef...

As part of the Stage 3 of the Pig-a international trial, we evaluated 7,12-dimethylbenz(a)anthracene (DMBA) for induction of Pig-a gene mutation using a 28-day repeat dose study design in Sprague-Dawley rats. In the same study, chromosomal damage in peripheral blood and primary DNA damage in liver were also investigated by the micronucleus (MN) assay and the Comet assay, respectively. In agreement with previously published data (Dertinger et al., [2010]: Toxicol Sci 115:401-411), DMBA induced dose-dependent increases of CD59-negative erythrocytes/reticulocytes and micronucleated reticulocytes (MN-RETs). However, there was no significant increase in DNA damage in the liver cells when tested up to 10 mg/kg/day, which appears to be below the maximum tolerated dose. When tested up to 200 mg/kg/day in a follow-up 3 dose study, DMBA was positive in the liver Comet assay. Additionally, we evaluated diethylnitrosamine (DEN), a known mutagen/hepatocarcinogen, for induction of Pig-a mutation, MN and DNA damage in a 28-day study. DEN produced negative results in both the Pig-a mutation assay and the MN assay, but induced dose-dependent increases of DNA damage in the liver and blood Comet assay. In summary, our results demonstrated that the Pig-a mutation assay can be effectively integrated into repeat dose studies and the data are highly reproducible between different laboratories. Also, integration of multiple genotoxicity endpoints into the same study not only provides a comprehensive evaluation of the genotoxic potential of test chemicals, but also reduces the number of animals needed for testing, especially when more than one in vivo genotoxicity tests are required.

We investigated the inflammatory response in pigs exposed to salmon fibrinogen/thrombin dressings. Animals were exposed to the material in 3 ways: (a) thrombin and fibrinogen were injected intravenously, (b) dual full-thickness skin lesions were surgically created on the dorsal aspect of the swine and treated with the fibrinogen/thrombin bandage and a commercial bandage or (c) a fibrinogen/thrombin bandage was inserted through an abdominal incision into the peritoneal cavity. Blood was collected twice weekly and animals were sacrificed at 7, 10 or 28 days. Animals in the 28-day dermal lesion group were given an injection of salmon fibrinogen/thrombin at the 10 day point to simulate a second bandage application. The immune response manifested itself as induction of germinal centers in mesenteric lymph nodes and in the white pulp of the spleen. Examination of the histology of the skin and organs showed a cellular inflammatory response with granulation tissue and signs of edema that resolved by the 28-day stage. Antibodies reactive to salmon and human thrombin and fibrinogen were detected, but fibrinogen levels and coagulation processes were not affected. In conclusion, animals treated with salmon fibrinogen/thrombin bandages demonstrated a smooth recovery course in terms of both tissue healing and the immune response without adverse effects from the exposure to the fish proteins.

The 2015 annual National Toxicology Program (NTP) Satellite Symposium, entitled “Pathology Potpourri” was held in Minneapolis, Minnesota at the ACVP/ASVCP/STP combined meeting. The goal of this symposium is to present and discuss diagnostic pathology challenges or nomenclature issues. Because of the combined meeting, both laboratory and domestic animal cases were presented. This article presents summaries of the speakers’ talks, including challenging diagnostic cases or nomenclature issues that were presented, along with select images that were used for audience voting and discussion. Some lesions and topics covered during the symposium included hepatocellular lesions; a proposed harmonized diagnostic approach to rat cardiomyopathy; crop milk in a bird; avian feeding accoutrement; heat exchanger in a tuna; metastasis of a tobacco carcinogen-induced pulmonary carcinoma; neurocytoma in a rat; pituicytoma in a rat; rodent mammary gland whole mounts; dog and rat alveolar macrophage ultrastructure; dog and rat pulmonary phospholipidosis; alveolar macrophage aggregation in a dog; degenerating yeast in a cat liver aspirate; myeloid leukemia in lymph node aspirates from a dog; Trypanosoma cruzi in a dog; solanum toxicity in a cow; bovine astrovirus; malignant microglial tumor; and nomenclature challenges from the Special Senses International Harmonization of Nomenclature and Diagnostic Criteria (INHAND) organ working group (OWG).

The 2014 annual National Toxicology Program (NTP) Satellite Symposium, entitled “Pathology Potpourri” was held in Washington DC, in advance of the Society of Toxicologic Pathology’s 33rd annual meeting. The goal of this annual NTP Symposium is to present current diagnostic pathology or nomenclature issues to the toxicologic pathology community. This article presents summaries of the speakers’ presentations, including diagnostic or nomenclature issues that were presented, along with select images that were used for audience voting and discussion. Some lesions and topics covered during the symposium included a pulmonary mucinous adenocarcinoma in a male B6C3F1 mouse; plexiform vasculopathy in Wistar Han rats; staging of the estrous cycle in rats and mice; peri-islet fibrosis, hemorrhage, lobular atrophy and inflammation in male Sprague Dawley rats; retinal dysplasia in Wistar Han rats and B6C3F1 mice; multicentric lymphoma with intravascular microemboli and tumor lysis syndrome, and two cases of myopathy and vascular anomaly in Tg.rasH2 mice; benign thymomas in Wistar Han rats; angiomatous lesions in the mesenteric lymph nodes of Wistar Han rats; an unusual foveal lesion in a cynomolgous monkey; and finally a series of nomenclatures challenges from the endocrine International Harmonization of Nomenclature and Diagnostic Criteria (INHAND) organ working group (OWG).