Michela Seveso

Tetanus and botulinum neurotoxins: turning bad guys into good by research

The neuroparalytic syndromes of tetanus and botulism are caused by neurotoxins produced by bacteria of the genus Clostridium. They are 150 kDa proteins consisting of three-domains, endowed with different functions: neurospecific binding, membrane translocation and specific proteolysis of three key components of the neuroexocytosis apparatus. After binding to the presynaptic membrane of motoneurons, tetanus neurotoxin (TeNT) is internalized and transported retroaxonally to the spinal cord, where it blocks neurotransmitter release from spinal inhibitory interneurons. In contrast, the seven botulinum neurotoxins (BoNT) act at the periphery and inhibit acetylcholine release from peripheral cholinergic nerve terminals. TeNT and BoNT-B, -D, -F and -G cleave specifically at single but different peptide bonds, VAMP/synaptobrevin, a membrane protein of small synaptic vesicles. BoNT types -A, -C and -E cleave SNAP-25 at different sites within the COOH-terminus, whereas BoNT-C also cleaves syntaxin. BoNTs are increasingly used in medicine for the treatment of human diseases characterized by hyperfunction of cholinergic terminals.

Structure of the Neutrophil-activating Protein from Helicobacter pylori

Helicobacter pylori is a major human pathogen associated with severe gastroduodenal diseases, including ulcers and cancers. An H.pylori protein that is highly immunogenic in humans and mice has been identified recently. This protein has been termed HP-NAP, due to its ability of activating neutrophils. In order to achieve a molecular understanding of its unique immunogenic and pro-inflammatory properties, we have determined its three-dimensional structure. Its quaternary structure is similar to that of the dodecameric bacterial ferritins (Dps-like family), but it has a different surface potential charge distribution. This is due to the presence of a large number of positively charged residues, which could well account for its unique ability in activating human leukocytes.

Pharmacology: Screening inhibitors of anthrax lethal factor

The disease anthrax is caused by lethal factor, an enzyme component of the toxin produced by the spore-forming bacterium Bacillus anthracis. Here we describe substrate molecules for this factor that offer a means for high-throughput screening of potential inhibitors for use in anthrax treatment. Our assay should help to answer the urgent call for new and specific therapies to combat this pathogen after its recent emergence as a terrorist bioweapon.

Screening inhibitors of anthrax lethal factor

The disease anthrax is caused by lethal factor, an enzyme component of the toxin produced by the spore-forming bacterium Bacillus anthracis. Here we describe substrate molecules for this factor that offer a means for high-throughput screening of potential inhibitors for use in anthrax treatment. Our assay should help to answer the urgent call for new and specific therapies to combat this pathogen after its recent emergence as a terrorist bioweapon.

Transgene Expression of Green Fluorescent Protein and Germ Line Transmission in Cloned Pigs Derived from In Vitro Transfected Adult Fibroblasts

The pig represents the xenogeneic donor of choice for future organ transplantation in humans for anatomical and physiological reasons. However, to bypass several immunological barriers, strong and stable human genes expression must occur in the pigs organs. In this study we created transgenic pigs using in vitro transfection of cultured cells combined with somatic cell nuclear transfer (SCNT) to evaluate the ubiquitous transgene expression driven by pCAGGS vector in presence of different selectors. pCAGGS confirmed to be a very effective vector for ubiquitous transgene expression, irrespective of the selector that was used. Green fluorescent protein (GFP) expression observed in transfected fibroblasts was also maintained after nuclear transfer, through pre- and postimplantation development, at birth and during adulthood. Germ line transmission without silencing of the transgene was demonstrated. The ubiquitous expression of GFP was clearly confirmed in several tissues including endothelial cells, thus making it a suitable vector for the expression of multiple genes relevant to xenotransplantation where tissue specificity is not required. Finally cotransfection of green and red fluorescence protein transgenes was performed in fibroblasts and after nuclear transfer blastocysts expressing both fluorescent proteins were obtained.

Ureteral Stenosis in HDAF Pig‐to‐Primate Renal Xenotransplantation: A Phenomenon Related to Immunological Events?

The aim of this study was to analyze the incidence of ureteral stenosis in a life‐supporting human decay‐accelerating factor (hDAF) transgenic pig‐to‐cynomolgus monkey kidney transplantation model and determine the role of possible immunological events in its pathogenesis.

Effects of long-term administration of high-dose recombinant human antithrombin in immunosuppressed primate recipients of porcine xenografts.

Background. Fibrin deposition is central to the acute humoral rejection process occurring in the presence of consumptive coagulopathy when pig organs are transplanted into primates. Methods. To assess whether strategies aimed at preventing fibrin formation may extend xenograft survival, we administered high daily doses of recombinant human antithrombin (rhAT) (500 U/kg twice daily) to obtain both anticoagulant and anti-inflammatory effects in immunosuppressed primate recipients of porcine kidneys. Results. Some degree of consumptive coagulopathy developed in both rhAT-treated (n=3) and untreated (n=3) primates. No major differences in the coagulation parameters analyzed were observed between the 2 groups. Similarly, no difference in survival was seen between rhAT-treated (20.6±4 days; range: 15–23 days) and untreated animals (17.3±11.6 days; range: 7–30 days), although the rhAT-treated primates had a higher bleeding tendency. Despite the high daily dose of rhAT, considerable fibrin deposition was observed in the graft as early as 2 weeks after transplantation. Conclusions. These results suggest that a high daily dose of rhAT fails to influence survival or prevent fibrin formation and deposition in the graft in our pig-to-primate model. However, the potential role of rhAT administered in combination with heparins or other clotting inhibitor concentrates in this model remains to be determined.

Alterations in the coagulation profile in renal pig-to-monkey xenotransplantation.

Five monkey recipients of a porcine renal xenograft were studied to determine the relationship between fibrin formation in acute humoral xenograft rejection (AHXR) and procoagulant and anticoagulant factor levels to establish whether changes in coagulation parameters could be used to predict AHXR and determine whether AHXR is associated with overt disseminated intravascular coagulopathy (DIC) in this 
 model.

De novo Anti-HLA Antibody Responses after Renal Transplantation: Detection and Clinical Impact

Numerous retrospective and prospective studies have been conducted to determine the prevalence and significance on long-term graft survival of de novo post-transplant donor-specific antibodies (DSA), directed against both HLA and non-HLA molecules. Moreover, it has been postulated that the development of anti-HLA antibodies may precede the clinical manifestation of chronic rejection, therefore being considered a predictive marker. In this context, the detection of C4d deposition in the failing kidney in patients presenting de novo DSA supports the hypothesis that antibody production and complement deposition could be involved in the pathogenesis of graft failure. Due to the development of more sensitive meth-ods to detect alloantibodies, the number of transplanted patients which show the appearance of DSA at different times following transplantation has increased. Nevertheless, this increased sensitivity has allowed the identification of circulating donor-specific anti-HLA antibodies in many patients with otherwise good graft function. Such findings are worthy of discussion, as it has yet to be determined whether these circulating antibodies can only be considered an early marker of humoral rejection or whether they could play a protective role. The possible relevance of the post-transplant appearance of non-DSA should also be mentioned. This review will focus primarily on de novo anti-donor HLA antibody responses in kidney transplant patients and will only briefly deal with anti-non HLA and non-DSA that will be discussed elsewhere in this issue.

In vitro and in vivo effects of the carbon monoxide-releasing molecule, CORM-3, in the xenogeneic pig-to-primate context.

Abstract: Background:  Carbon monoxide (CO) interferes with inflammatory and apoptotic processes associated with ischemia–reperfusion injury and graft rejection. Here, the in vitro effects of carbon monoxide releasing molecule‐3 (CORM‐3), a novel water‐soluble carbonyl CO carrier, have been investigated on porcine aortic endothelial cells (PAEC) and primate peripheral blood mononuclear cells (PBMC). Furthermore, the pharmacodynamics and pharmacotolerance of CORM‐3 after administration of single and multiple doses in the primate have been assessed in view of its potential application in pig‐to‐primate xenotransplantation models.