[Induced expression of alpha-toxin gene of Clostridium perfringens in recombinant Lactobacillus casei and their immunoprotective in mice]

OBJECTIVE

The prepared an oral vaccine by constructing recombinant Lactobacillus casei expressing alpha-toxin gene of Clostridium perfringens, for preventing poisoning by Clostridium perfringens.

METHODS

The constructed cell-surface expression plasmid pPG1-alpha/L. 393 and secretion expression plasmid pPG2-alpha/L. 393, both with alpha-toxin gene, were electroporated into L. casei 393, generating recombinant bacteria pPG1-alpha/L. casei 393 and pPG2-alpha/L. casei 393. The recombinant strains were induced by 1% lactose in De Man, Rogosa and Sharp (MRS) broth, and the target protein was detected by 12% sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), Western blot and indirect immunofluorescence assay. BALB/C mouse were used as animal model immunized with recombinant strains by intragastric administration, and the immune efficacy was analyzed. Specific anti-alpha-toxin protein sIgA was detected by indirect enzyme linked immunosorbent assay (ELISA) in the feces, vaginal lavage, eye washing of mice after intragastric administration, and Specific IgG was detected by indirect ELISA in the serum of immunized mice. The resistance of immunized mice to alpha-toxin and the neutralization ability of antibodies to alpha-toxin were also tested.

RESULTS

Mice immunized with pPG1-alpha/L. casei 393 and pPG2-alpha/L. casei 393 could produce remarkable anti-alpha-toxin antibodies, sIgA and circulating antibody IgG had completely neutralization ability against alpha-toxin. The test of alpha-toxin challenge in mice showed that the immunized mice could resist three times' Minimum Lethal Dose (MLD).

CONCLUSION

All the results indicated that mice inmmunized by the recombinant L. casei expressing alpha-toxin gene of C. perfringens could elicit regional and systematic immunity response and neutralization ability.

Host defense against bacterial keratitis

PURPOSE

To define factors that protect the eye from Staphylococcus aureus keratitis and limit tissue damage once keratitis occurs.

METHODS

Rabbit tears were analyzed for bactericidal and phospholipase A(2) (PLA(2)) activities on S. aureus. Inhibition by spermidine of PLA(2) anti-staphylococcal activity in tears was tested in vitro and in vivo. Rabbits immunized with heat-inactivated alpha-toxin were challenged with intrastromal injection of S. aureus.

RESULTS

Arachidonic acid was cleaved from S. aureus by purified PLA( 2) or rabbit tears. Spermidine inhibited these reactions in vitro and facilitated keratitis in vivo. PLA(2) activity decreased with advanced age and shortly following sleep, but increased with keratitis. Antibody to alpha-toxin significantly reduced corneal damage and epithelial cell sloughing during keratitis.

CONCLUSIONS

PLA(2) is a major host-defense component of rabbit tears. Alpha-toxin is a major mediator of corneal damage, and antibody to alpha-toxin reduces pathologic changes during keratitis.

[The correction action of Phosprenyl and Gamavit on the functional activity of mouse peritoneal macrophages in response to high doses of Staphylococcus aureus alpha-toxin]

The study of the functional activity of peritoneal macrophages of BALB/c mice at different stages of the toxic action caused by S. aureus alpha-toxin (ST) was carried out. The analysis of the dynamics of toxic reaction revealed the main critical points of triggering necrotic processes: the first hour and day 2. One hour after the injection of large doses of ST a sharp increase in the process of antigen binding with its subsequent sharp decrease. Simultaneously, a decrease in the activity of the lysosomal enzymes cathepsin D and acidic phosphatase was established, which was indicative of the destabilization of both lysosomal and cellular macrophage membranes. The increase of oxygen metabolism on day 2, together with the release of lysosomal proteases into the extracellular area, correlated with the maximum death rate of mice and served as the main index of the development of necrosis. The prophylactic and therapeutic use of the preparations Gamavit and Phosprenyl revealed their antitoxic activity and capacityfor stimulating the level of natural body resistance.

Phospholipase C gamma in distinct regions of the ventral tegmental area differentially regulates morphine-induced locomotor activity

Neurotrophic factors and the signaling pathways they activate play a role in mediating long-term molecular, cellular, and behavioral adaptations associated with drug addiction. Here we mimicked the biological response of phospholipase C-gamma (PLC gamma) induction in the ventral tegmental area (VTA) observed after chronic morphine using viral-mediated gene transfer. Using a behavioral sensitization paradigm, we demonstrate that microinjections of PLC gamma 1 into distinct (rostral vs. caudal) regions of the VTA result in differential locomotor responses to morphine.

A cellular deficiency of gangliosides causes hypersensitivity to Clostridium perfringens phospholipase C

Clostridium perfringens phospholipase C (Cp-PLC), also called alpha-toxin, is the major virulence factor in the pathogenesis of gas gangrene. Previously, a cellular UDP-Glc deficiency was related with a hypersensitivity to the cytotoxic effect of Cp-PLC. Because UDP-Glc is required in the synthesis of proteoglycans, N-linked glycoproteins, and glycosphingolipids, the role of these gly-coconjugates in the cellular sensitivity to Cp-PLC was studied. The cellular sensitivity to Cp-PLC was significantly enhanced by glycosphingolipid synthesis inhibitors, and a mutant cell line deficient in gangliosides was found to be hypersensitive to Cp-PLC. Gangliosides protected hypersensitive cells from the cytotoxic effect of Cp-PLC and prevented its membrane-disrupting effect on artificial membranes. Removal of sialic acids by C. perfringens sialidase increases the sensitivity of cultured cells to Cp-PLC and intramuscular co-injection of C. perfringens sialidase, and Cp-PLC in mice potentiates the myotoxic effect of the latter. This work demonstrated that a reduction in gangliosides renders cells more susceptible to the membrane damage caused by Cp-PLC and revealed a previously unrecognized synergism between Cp-PLC and C. perfringens sialidase, providing new insights toward understanding the pathogenesis of clostridial myonecrosis.

Immunization with the C‐Domain of α‐Toxin Prevents Lethal Infection, Localizes Tissue Injury, and Promotes Host Response to Challenge withClostridium perfringens

Clostridium perfringens gas gangrene is characterized by rapid tissue destruction, impaired host response, and, often, death. Phospholipase C (alpha -toxin) is the virulence factor most responsible for these pathologies. The present study investigated the efficacy of active immunization with the C-terminal domain of alpha -toxin (Cpa247-370) in a murine model of gas gangrene. Primary end points of the study were survival, progression of infection, and tissue perfusion. Secondary end points, which were based on findings of histologic evaluation of tissues, included the extent of tissue destruction and microvascular thrombosis, as well as the magnitude of the tissue inflammatory response. Survival among C-domain-immunized animals was significantly greater than that among sham-immunized control animals. Furthermore, immunization with the C-domain localized the infection and prevented ischemia of the feet. Histopathologic findings demonstrated limited muscle necrosis, reduced microvascular thrombosis, and enhanced granulocytic influx in C-domain-immunized mice. We conclude that immunization with the C-domain of phospholipase C is a viable strategy for the prevention of morbidity and mortality associated with C. perfringens gas gangrene.

Immunization with alpha-toxin toxoid protects the cornea against tissue damage during experimental Staphylococcus aureus keratitis

Alpha-toxin is a major virulence factor in Staphylococcus aureus keratitis. Active or passive immunization with alpha-toxin toxoid could protect against corneal damage. Results show that either form of immunization did not kill bacteria but did significantly protect against corneal pathology, especially epithelial erosion.

Effects of Clostridium perfringens recombinant and crude phospholipase C and theta-toxin on rabbit hemodynamic parameters

Clostridium perfringens exotoxins have been implicated as major virulence factors responsible for shock and organ failure in gas gangrene, yet the mechanism(s) by which they mediate cardiovascular dysfunction remain enigmatic. Recombinant (r) phospholipase C (PLC), r theta-toxin, culture supernatant (crude toxin), or 0.9% NaCl was infused intravenously into awake rabbits. Cardiac index (CI), mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), arterial blood gases, and hematocrit were measured 1 h before and for 3 h after toxin infusion. Crude toxin and rPLC decreased CI, MAP, and HR and increased CVP; mortality was 87.5% and 83%, respectively. r theta-toxin did not decrease CI or MAP and mortality was 25%. Further, crude toxin and rPLC but not r theta-toxin inhibited cardiac contractility (dF/dt) in isolated rabbit atrial muscles. These results suggest that PLC-induced myocardial dysfunction contributes to shock in C. perfringens infection.

S-phase induction and transformation of quiescent NIH 3T3 cells by microinjection of phospholipase C

Two inositol phospholipid-specific phospholipase C (PLC) isozymes (PLC-I and -II) have been purified from bovine brain. When PLC-I or PLC-II was microinjected (100-700 micrograms/ml) into quiescent NIH 3T3 cells, a time- and dose-dependent induction of DNA synthesis occurred, as demonstrated by [3H]thymidine incorporation into nuclear DNA. In addition, approximately to 8 hr after PLC injection, NIH 3T3 fibroblasts appeared spindle-shaped, refractile, and highly vacuolated, displaying a morphology similar to transformed cells. The morphologic transformation was apparent for 26-30 hr after which the injected cells reverted back to a normal phenotype. Microinjected PLC at a high concentration (1 mg/ml) was cytotoxic, dissolving the cytoplasmic membrane and leaving behind cellular ghosts. PLC is a key regulatory enzyme involved in cellular membrane signal transduction. Introduction of exogenous PLC into NIH 3T3 cells by microinjection induced a growth and oncogenic potential, as demonstrated by the ability of microinjected PLC (approximately 10,000 molecules per cell) to override the cellular G0 block, inducing DNA synthesis and morphologic transformation of growth-arrested fibroblast cells.

Differential effects of combinations of phospholipase A2 and phospholipase C on the activity of rat epididymal nuclear and microsomal 4-ene steroid 5 alpha-reductase

Epididymal 4-ene steroid 5 alpha-reductase converts testosterone to 5 alpha-dihydrotestosterone. The enzyme is localized to the nuclear and microsomal fractions, and the activity can be altered by modifying the phospholipids in the membrane environment. To investigate the membrane dependence of 4-ene steroid 5 alpha-reductase, we have treated nuclear and microsomal membranes with combinations of phospholipase A2 and phospholipase C, and examined the effects on 4-ene steroid 5 alpha-reductase activity. Sequential addition of phospholipase A2 and phospholipase C to the nuclear fraction, reduced the 4-ene steroid 5 alpha-reductase activity to approx 25% of the control level. Neither the nature of the phospholipase, nor the sequence of addition altered the inhibition. When both phospholipases were added simultaneously, nuclear 4-ene steroid 5 alpha-reductase activity was inhibited in a linear fashion, and in tests for cooperativity, the effects of phospholipase A2 and phospholipase C were clearly additive. The microsomal enzyme responded differently to sequential phospholipase treatments; if phospholipase A2 was followed by phospholipase C, or phospholipase C followed by phospholipase A2, the 4-ene steroid 5 alpha-reductase activity was, respectively, 13 and 27% of the control. In contrast, sequential addition of the same phospholipase reduced the activity of 4-ene steroid 5 alpha-reductase to approx 40% of the control level. Furthermore, simultaneous addition of phospholipase A2 and phospholipase C to the microsomal fraction, resulted in non-linearity of 4-ene steroid 5 alpha-reductase activity with time, whereas when added individually, linearity of 4-ene steroid 5 alpha-reductase was maintained. Consequently, it was not possible to test for cooperative effects of phospholipases on the microsomal 4-ene steroid 5 alpha-reductase. These findings suggest that for the nuclear 4-ene steroid 5 alpha-reductase, the polar and non-polar regions of the membrane environment have similar functions, which are most likely involved in the maintenance of the structural integrity of the enzyme. For the microsomal enzyme, the polar and non-polar regions of the membrane appear to have different functions, not only for the maintenance of enzyme integrity, but also in the mechanism at the active site.

Selective elimination of lymphocyte subpopulations by monoclonal antibody-enzyme conjugates

A novel method for the selective depletion of lymphocyte subpopulations has been developed. Conjugates of glucose oxidase (GOx) and phospholipase-C (PL-C) coupled to a monoclonal mouse anti-rat IgG (MAR) were shown to be selectively cytotoxic for targeted lymphocyte subsets in the presence of various rat monoclonal antibodies directed toward murine cell surface antigens. The ability of both conjugates to bind specifically to rat monoclonal antibodies was demonstrated by flow cytometry. The PL-C-MAR conjugate was more stable than the GOx-MAR conjugate. The PL-C conjugate, in conjunction with primary rat anti-mouse monoclonal antibodies, produced selective killing of T or B cells as detected by a loss of proliferative capacity in response to mitogens and by specific cell depletion demonstrated by flow cytometry. Normal mouse serum protected against the cytotoxicity of free enzymes but had no protective effect on enzyme conjugates. Because the substrates of these enzymes are abundant in vivo and serum did not interfere with their cytotoxicity, these enzyme-antibody conjugates may be valuable for selective lymphocyte depletion in vivo.

Combination chemotherapy with Clostridium perfringens phospholipase C and cytosine antimetabolites: complementary inhibition directed at membrane lipids

Tumor cell membranes were susceptible to the action of Clostridium perfringens phospholipase C, and this was reflected by inhibition of cellular replication in culture. The differential susceptibility of two neoplastic cell lines to this enzyme was studied in detail. The growth of sarcoma 180 cells cultured in Fischer's medium was markedly inhibited by phospholipase C; whereas, in contrast, cultured L1210 leukemia cells were relatively resistant to the cytotoxic effects of this enzyme. The differential sensitivity of these two neoplastic cell lines to phospholipase C was corroborated by dye-exclusion tests. Thus, leukemia L1210 cells exposed to a concentration of 0.2 mg of phospholipase C per ml of Fischer's medium for 30 min at 37 degrees C were able to exclude Trypan Blue; whereas, only about 21% of sarcoma 180 cells treated under identical conditions were able to exclude the dye. That the cytotoxicity of phospholipase C to sarcoma 180 was the result of hydrolysis of phospholipids of the plasma membrane was supported by measurements of the rate of hydrolysis of radioactivity from the phospholipid of neoplastic cells prelabeled with [3H]choline. Eighty-two percent of incorporated radioactive choline was released from sarcoma 180 cells treated with phospholipase C in Fischer's medium, whereas, only 20% of the label from [3H]choline was solubilized from L1210 leukemia cells treated with the enzyme under similar conditions. Scanning electron microscopy revealed significant damage to sarcoma 180 cells exposed to phospholipase C in Fischer's medium, which was characterized by alterations in size and shape of cells, disappearance of microvilli, and appearance of fistulas in cell membranes; relatively resistant L1210 leukemic cells did not appear to be markedly damaged by comparable enzyme treatment. Exposure of leukemia L1210 cells to phospholipase C in Puck's saline A increased the sensitivity of these cells to enzymatic action. Under these conditions, a comparable amount of phospholipid was hydrolyzed from surface membranes of sarcoma 180 and leukemia L1210 cells, and the degree of membrane damage appeared to be similar, as measured by the capacity of the tumor cell lines to exclude Trypan Blue and by scanning electron microscopy. The extensive damage to membranes by hydrolysis of phospholipids was not accompanied by a change in the degree of specific binding of [3H]concanavalin A(ConA).(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition of implantation by the intrauterine administration of phospholipases in the rat

Phospholipases A2 and C (93 and 500 mU) were administered to uterine horns of Long-Evans adult rats during the first five days of pregnancy. As control material, saline (0.15 M) was administered to contralateral uterine horns. The animals were sacrificed on the ninth day of pregnancy, the uterine horns were removed and the number of implanted embryos were counted. Both horns were examined with light and electron microscopes. For electron microscopy, Ruthenium red was used to visualize possible changes of the outer coat (glycocalix) of the plasma membrane of endometrial epithelial cells. Implantation was inhibited when phospholipases A2 and C were administered during the first three days of pregnancy. Ultrastructural modifications included decrease of glycoproteins as demonstrated by diminution of the Ruthenium red staining that may indicate a decrease in the negative surface charges of endometrial surface epithelium.

Muscle extract infusion in rabbits. A new experimental model of the crush syndrome

Previous studies provide inconclusive data concerning the nephrotoxicity of myoglobin following muscle injury. We investigated the possibility that released muscle constituents other than myoglobin may be associated with renal damage, and studied accompanying hematological and coagulation changes. An extract of homologous or autologous muscle was infused intravenously in rabbits in a dose of 100 mg of muscle extract protein/kg; equine myoglobin was given to control animals. Experimental animals developed proteinuria, cylindruria, and a 50% reduction in glomerular filtration rate. Leukopenia, thrombocytopenia and evidence of intravascular coagulation also were seen. The muscle extract was shown to have thromboplastic activity; however inhibition of this by phospholipase C did not prevent the changes induced by muscle extract infusion possibly because the intrinsic changes coagulation pathway still was activated. Although moderate hypotension and ECG changes developed in some rabbits, these were not consistent and the renal functional changes appeared to be independent of these factors. Pulmonary and glomerular microthrombi were seen in experimental animals and there was vacuolation of the renal proximal tubular cells. The studies indicate that a number of biological systems are activated following muscle extract infusion and that these may be more important than the nephrotoxicity of myoglobin in the pathogenesis of the renal injury.