Phosphatidylcholine-Specific Phospholipase C from Listeria monocytogenes Is an Important Virulence Factor in Murine Cerebral Listeriosis

Meningoencephalitis is a serious and often fatal complication of Listeria monocytogenes infection. The aim of the present study was to analyze the role of internalin A (InlA) and B, which are involved in the invasion of L. monocytogenes into cultivated host tissue cells, and that of phosphatidylcholine-specific phospholipase C (PlcB), which mainly promotes the direct cell-to-cell spread of L. monocytogenes, in murine cerebral listeriosis by use of an InlA/B (ΔinlAB2)- and a PlcB (ΔplcB2)-deficient isogenic deletion mutant strain and the wild-type (WT) L. monocytogenes EGD. Listeria strains were directly applied to the brain, a technique which has been employed previously to study the pathogenesis of cerebral listeriosis (D. Schlüter, S. B. Oprisiu, S. Chahoud, D. Weiner, O. D. Wiestler, H. Hof, and M. Deckert-Schlüter, Eur. J. Immunol. 25:2384–2391, 1995). We demonstrated that PlcB, but not InlA or InlB, is an important virulence factor in cerebral listeriosis. Nonimmunized mice infected intracerebrally with the ΔplcB2 strain survived significantly longer and had a reduced intracerebral bacterial load compared to mice infected with the ΔinlAB2 strain or WT bacteria. In addition, immunization with the WT prior to intracerebral infection significantly increased the survival rate of mice challenged intracerebrally with the ΔplcB2 strain compared to that of mice infected with the WT or ΔinlAB2 strain. Histopathology revealed that the major difference between the various experimental groups was a significantly delayed intracerebral spread of the ΔplcB2 mutant strain, indicating that cell-to-cell spread is an important pathogenic feature of cerebral listeriosis. Interestingly, irrespective of the Listeria mutant used, the apoptosis of hippocampal and cerebellar neurons and an internal hydrocephalus developed in surviving mice, indicating that these complications are not dependent on the virulence factors InlA/B and PlcB. In conclusion, this study points to PlcB as a virulence factor important for the intracerebral pathogenesis of murine L. monocytogenes meningoencephalitis.     

Molecular cloning, sequencing, and identification of a metalloprotease gene from Listeria monocytogenes that is species specific and physically linked to the listeriolysin gene.

The entire nucleotide sequence of an open reading frame located immediately downstream of the listeriolysin gene from a virulent Listeria monocytogenes serotype 1/2a strain was determined. The product of the open reading frame was 510 amino acids with a predicted molecular weight of 57,400. The deduced amino acid sequence of this open reading frame is highly similar to that of a family of secreted metalloproteases produced by various members of the genus Bacillus, of which thermolysin is the prototype. Immunoblots performed with specific antisera raised against thermolysin from Bacillus stearothermophilus allowed the detection of a 60-kDa polypeptide, corresponding to the pro-form of the protease, in culture supernatants of L. monocytogenes strains. In maxicell experiments, Escherichia coli recombinants harboring this open reading frame also specifically directed production of a 60-kDa protein. Protease activity was low to undetectable in both Listeria strains and E. coli recombinants. This is due to lack of processing of the inactive pro-form of the protease to its mature active form in both species. We have designated this gene mpl for metalloprotease of L. monocytogenes. The gene was present only in pathogenic L. monocytogenes strains, in which it was physically linked to the listeriolysin gene.     

Fibronectin--a plasmin-sensitive glycoprotein of the transit zone: protection by aprotinin

Intravascular and extravascular fibronectin represents an essential "early information-transmitting" molecule of the transit zone. It appears to play a part especially in the flow of information provoked by sympathetic reactions (every form of stress), which is associated with a rise in plasmin levels. The rapid proteolytic cleavage of fibronectin by plasmin alters the composition of the ground substance, hence its informational contents. This is transmitted to the glycocalyx of affected cells, provoking a reaction typical of those particular cells. When a stress goes beyond the physiological margin of tolerance, an excessive break-down of fibronectin quickly ensues so that the transit zone will transmit faulty information. It has been demonstrated on human and animal tissue that initial use of the potent plasmin inhibitor aprotinin (Trasylol) can provide a selective protection of fibronectin and, consequently, of the transit zone. Clinical results obtained in patients with multiple injuries corroborate this observation.     

Induction of immune tolerance in patients with hemophilia A and inhibitors treated with porcine VIIIC by home therapy

Home therapy with porcine factor VIIIC was safe and effective when administered to five hemophilic patients over periods of 8 1/2, 6, 4, 3 1/2, and 2 years. No significant transfusion reactions occurred. Before treatment with porcine factor VIIIC, all five had high-level, high- responding anti-human VIIIC inhibitors initially lacking anti-porcine factor VIIIC activity. Although specific anti-porcine VIIIC inhibitors arose in all patients, these were generally transient, and only one patient became refractory to treatment. We believe that porcine factor VIIIC is the treatment of choice in patients whose inhibitors do not cross-react. All five patients lost their original anti-human VIIIC inhibitors after starting treatment with porcine VIIIC, permitting the reintroduction of human VIIIC in three of them. There has been no recurrence of anti-human VIIIC inhibitor activity during 2 to 3 years of regular treatment with human VIIIC in these patients. This suggests that tolerance to human VIIIC has arisen as a result of treatment with porcine VIIIC. Porcine VIIIC may have a role in the desensitization of some factor VIIIC inhibitor patients.     

Locus assignment of two alpha-globin structural mutants from the Caribbean basin: alpha Fort de France (alpha 45 Arg) and alpha Spanish Town (alpha 27 Val)

Two alpha-globin structural mutants were mapped to their encoding loci by in vitro translation of hybrid-selected alpha 1- and alpha 2-globin mRNA. The more highly expressed mutant, alpha Spanish Town (alpha 27Val), is encoded at the alpha 2 locus and the less expressed mutant, alpha Fort de France (alpha 45Arg), is encoded at the alpha 1 locus. These results further define the distribution of alpha-globin structural mutations within the alpha-globin gene cluster and substantiate the dominant role of the alpha 2-globin locus in alpha- globin expression.     

Influence of dietary (n-3)-polyunsaturated fatty acids on leukotriene B4 and prostaglandin E2 synthesis and course of experimental tuberculosis in guinea pigs

Summary In the present study eicosanoid synthesis was studied in macrophages of guinea pigs fed different amounts of (n-6)- and (n-3)-polyunsaturated fatty acids (PUFA). Three groups of weanling guinea pigs were fed by isocaloric diets differing only in their contents of PUFA: controls with 2.8 Cal% of linoleic acid (LA; 18:2(n-6)); (n-6)-rich fed animals with 15.4 Cal% of LA; and (n-3)-rich fed animals with 10.1 Cal% of LA, 1.4 Cal% of eicosapentaenoic acid (20:5(n-3)) and docosahexaenoic acid (22:6(n-3)). After 13 weeks half the number of animals from each group was infected i.m. by 180 colony forming units ofMycobacterium tuberculosis strain H37Rv. Seven weeks after infection the release of leukotriene (LT)B₄ and prostaglandin (PG)E₂ was quantified in calcium ionophore stimulated whole blood, peritoneal macrophage cultures and alveolar macrophages by immunoassays after high performance liquid chromatography. Synthesis of LTB₄ and PGE₂ was found to be reduced in (n-3)-rich fed guinea pigs (p<0.05), and equivalent between controls and (n-6)-rich fed animals. Controls and (n-6)-rich fed animals showed the same mycobacterial counts in the spleen whereas (n-3)-rich fed guinea pigs demonstrated an increased number of mycobacteria (p<0.05). Our results demonstrate that an increased dietary intake of (n-3)-PUFA suppress LTB₄ and PGE₂ synthesis. The increased number ofM. tuberculosis found in the spleens of (n-3)-rich fed animals could represent persistence of the experimental infection. It may be speculated that a functional relationship exists between the two findings.

---

Einfluß einer Diät mit (n-3)-mehrfach ungesättigten Fettsäuren auf die Leukotrien B₄- und Prostaglandin E₂-Synthese und den Verlauf der experimentellen Tuberkulose bei Meerschweinchen

Zusammenfassung In der vorliegenden Studie wurde die Eikosanoidsynthese in Makrophagen von Meerschweinchen untersucht, die mit unterschiedlichen Gehalten (n-6)- und (n-3)-mehrfach ungesättigten Fettsäuren (PUFA) gefüttert wurden. Drei Gruppen entwöhnter Meerschweinchen wurden mit isokalorischen Diäten gefüttert, die sich nur in ihrem Gehalt an PUFA unterschieden: Kontrollen mit 2,8 Cal% Linolsäure (LA. (18:2(n-6)); Tiere mit (n-6)-angereichertem Futter mit 15,4 Cal% LA und Tiere mit (n-3)-angereichertem Futter mit 10,1 Cal% LA, 1,4 Cal% Eikosapentaensäure (20:5(n-3)) und 0,9 Cal% Dokosahexaensäure (22:6(n-3)). Nach 13 Wochen wurde die Hälfte der Tiere aus jeder Gruppe mit 180 Kolonie-bildenden Einheiten des StammesMycobacterium tuberculosis H37Rv i.m. infiziert. Sieben Wochen nach Infektion wurde die Freisetzung von LTB₄ und PGE₂ in Kalzium-Ionophor stimuliertem Vollblut, Peritonealmakrophagen und Alveolarmakrophagen mittels Immunoassays nach Hochdruckflüssigkeitschromatographie quantifiziert. Die Synthese von LTB₄ und PGE₂ war reduziert bei den (n-3)-reich gefütterten Meerschweinchen (p<0,05) und äquivalent bei den Kontrollen und (n-6)-reich gefütterten Tieren. Kontrolltiere und (n-6)-reich gefütterte Meerschweinchen wiesen die gleiche Zahl von Mykobakterien in der Milz auf, während sich bei den (n-3)-gefütterten Tieren eine erhöhte Zahl von Mykobakterien zeigte (p<0,05). Unsere Ergebnisse zeigen, daß eine höhere diätetische Zufuhr von (n-3)-PUFA die Synthese von LTB₄ und PGE₂ unterdrückt. Die erhöhte Zahl vonM. tuberculosis in den Milzen von (n-3)-gefütterten Tieren spricht für eine Persistenz der experimentellen Tuberkulose unter diesen Bedingungen. Möglicherweise existiert zwischen beiden Befunden ein funktioneller Zusammenhang.