Ability of SPI2 mutant of S. typhi to effectively induce antibody responses to the mucosal antigen enterotoxigenic E. coli heat labile toxin B subunit after oral delivery to humans.

We have evaluated an oral vaccine based on an Salmonella enteric serovar typhi (S. typhi) Ty2 derivative TSB7 harboring deletion mutations in ssaV (SPI-2) and aroC together with a chromosomally integrated copy of eltB encoding the B subunit of enterotoxigenic Escherichia coli heat labile toxin (LT-B) in volunteers. Two oral doses of 10(8) or 10(9)CFU were administered to two groups of volunteers and both doses were well tolerated, with no vaccinemia, and only transient stool shedding. Immune responses to LT-B and S. typhi lipopolysaccharide were demonstrated in 67 and 97% of subjects, respectively, without evidence of anti-carrier immunity preventing boosting of LT-B responses in many cases. Further development of this salmonella-based (spi-VEC) system for oral delivery of heterologous antigens appears warranted.

The assessment of chemically induced liver injury in rats.

The object of this investigation was to study the relationship between acute hepatic injury and blood coagulation. Most of the clotting factors are synthesised by the hepatocytes and therefore it would seem likely that hepatic injury would lead to an impairment of blood clotting. Dimethylnitrosamine (DMN) and carbon tetrachloride (CCl4) were selected as model hepatotoxins to induce an acute hepatic lesion. Single doses of each compound were administered to male rats and groups of animals killed 3, 6, 16 and 24 h later in order to study the morphological development of the lesion and to relate this to changes in the haematological profiles. Both compounds produced a centrilobular necrosis, but with DMN there was a haemorrhagic component due to damage to endothelial cells, which contrasts with the classical coagulative necrosis produced by CCl4. After 6 h apoptosis was commonly seen in the centrilobular areas of the DMN treated rats. This process of cell death has not previously been demonstrated in chemically induced acute hepatic injury and was not seen in the CCl4 treated rats. Significantly prolonged clotting times were seen in both DMN and CCl4 treated rats and occurred in parallel with some of the early morphological changes but prior to the appearance of extensive haemorrhagic or coagulative necrosis. This preliminary data suggests that the measurement of blood coagulation times may provide a relatively specific and sensitive indicator of acute hepatic injury in rats.

Acute toxicity and recovery in the hemopoietic system of rats after treatment with ethylene glycol monomethyl and monobutyl ethers.

Male rats were given ethylene glycol monomethyl ether (EGM) or ethylene glycol monobutyl ether (EGB) po for 4 consecutive days at doses of 100 or 500 mg/kg body wt/day for EGM, and 500 or 1000 mg/kg body wt/day for EGB. Animals were killed on Days 1, 4, 8, and 22 after the final treatment. Both EGM and EGB produced thymic atrophy and lymphocytopenia and, in the case of EGM, neutropenia also. Hemolytic anemia induced by EGB resulted in splenic extramedullary hemopoiesis, hyperplasia of both spleen and bone marrow, and reticulocytosis. Apart from residual slight increases in spleen weight, mean red cell volume, and mean corpuscular hemoglobin at the end of the recovery period, other effects were reversible. With EGM, reduction in the numbers of circulating red cells was only slight. Treatment with EGM also abolished splenic extramedullary hemopoiesis which partially recovered on Day 4, followed by a marked response on Day 8, and return to the moderate control values on Day 22. Femoral bone marrow was hemorrhagic 1 day after treatment with EGM which appeared to be associated with sinus endothelial cell damage. By Day 4 the histologic appearance of the marrow was normal. Testicular atrophy was also produced in EGM-treated animals which persisted for the duration of the experiment. It is concluded that EGM and EGB differ considerably in the spectrum of toxic changes induced, and apart from testicular atrophy, these changes were largely reversible within a short time of the end of treatment.