Enhanced neutralization potency of botulinum neurotoxin antibodies using a red blood cell-targeting fusion protein.

Botulinum neurotoxin (BoNT) potently inhibits cholinergic signaling at the neuromuscular junction. The ideal countermeasures for BoNT exposure are monoclonal antibodies or BoNT antisera, which form BoNT-containing immune complexes that are rapidly cleared from the general circulation. Clearance of opsonized toxins may involve complement receptor-mediated immunoadherence to red blood cells (RBC) in primates or to platelets in rodents. Methods of enhancing immunoadherence of BoNT-specific antibodies may increase their potency in vivo. We designed a novel fusion protein (FP) to link biotinylated molecules to glycophorin A (GPA) on the RBC surface. The FP consists of an scFv specific for murine GPA fused to streptavidin. FP:mAb:BoNT complexes bound specifically to the RBC surface in vitro. In a mouse model of BoNT neutralization, the FP increased the potency of single and double antibody combinations in BoNT neutralization. A combination of two antibodies with the FP gave complete neutralization of 5,000 LD50 BoNT in mice. Neutralization in vivo was dependent on biotinylation of both antibodies and correlated with a reduction of plasma BoNT levels. In a post-exposure model of intoxication, FP:mAb complexes gave complete protection from a lethal BoNT/A1 dose when administered within 2 hours of toxin exposure. In a pre-exposure prophylaxis model, mice were fully protected for 72 hours following administration of the FP:mAb complex. These results demonstrate that RBC-targeted immunoadherence through the FP is a potent enhancer of BoNT neutralization by antibodies in vivo.

Development of a novel DNA SynCon tetravalent dengue vaccine that elicits immune responses against four serotypes.

The increased transmission and geographic spread of dengue fever (DF) and its most severe presentations, dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), make it one of the most important mosquito-borne viral disease of humans. Four distinct serotypes of dengue viruses are transmitted to humans through the bites of the mosquitoes. Currently there is no vaccine or antiviral drug against DV infections. Cross-protection between dengue virus serotypes is limited and antibody dependent enhancement (ADE) contributes significantly to the severity of the disease. The major challenge is to induce a broad durable immune response against all four serotypes of dengue virus simultaneously while avoiding the possible exacerbation of risk of developing the severe forms of disease through incomplete or modified responses. In order to address this worldwide concern, we present a synthetic consensus (SynCon) human codon optimized DNA vaccine that elicits immunity against all four dengue serotypes. We cloned consensus DIII domain of E protein from all serotypes and expressed them as a single open reading frame in a mammalian expression vector, called pDV-U-DIII (dengue-vaccine universal). In mice, this dengue-universal construct elicits significant level of anti-DIII antibody that neutralizes all four dengue subtypes and prevents cell death induced by dengue infection. This is the first SynCon DNA vaccine that provides tetravalent immunity against all four serotypes of dengue virus.

Expression, purification, and kinetic characterization of full-length human fibroblast activation protein.

Human fibroblast activation protein (FAP), an integral membrane serine protease, was produced in insect cells as a hexa-His-tagged protein using a recombinant baculovirus expression system. Two isoforms of FAP, glycosylated and nonglycosylated, were identified by Western blotting using an anti-His-tag antibody and separated by lectin chromatography. The glycosylated FAP was purified to near homogeneity using immobilized metal affinity chromatography and was shown to have both postprolyl dipeptidyl peptidase and postgelatinase activities. In contrast, the nonglycosylated isoform demonstrated no detectable gelatinase activity by either zymography or a fluorescence-based gelatinase activity assay. The kinetic parameters of the dipeptidyl peptidase activity for glycosylated FAP were determined using dipeptide Ala-Pro-7-amino-trifluoromethyl-coumarin as the substrate. The k(cat) is 2.0 s(-1) and k(cat)/K(m) is 1.0 x 10(4) M(-1) s(-1) at pH 8.5. The pH dependence of k(cat) reveals two ionization groups with pK(a1) of 7.0 and pK(a2) of 11.0. The pH profile of k(cat)/K(m) yields similar results with pK(a1) 6.2 and pK(a2) 11.0. The neutral pK(a1) is associated with His at the active site. The basic pK(a2) might be contributed from an ionization group that is not involved directly in catalysis, instead associated with the stability of the active site structure.

Absence of post-translational aspartyl beta-hydroxylation of epidermal growth factor domains in mice leads to developmental defects and an increased incidence of intestinal neoplasia.

The BAH genomic locus encodes three distinct proteins: junctin, humbug, and BAH. All three proteins share common exons, but differ significantly based upon the use of alternative terminal exons. The biological roles of BAH and humbug and their functional relationship to junctin remain unclear. To evaluate the role of BAH in vivo, the catalytic domain of BAH was specifically targeted such that the coding regions of junctin and humbug remained undisturbed. BAH null mice lack measurable BAH protein in several tissues, lack aspartyl beta-hydroxylase activity in liver preparations, and exhibit no hydroxylation of the epidermal growth factor (EGF) domain of clotting Factor X. In addition to reduced fertility in females, BAH null mice display several developmental defects including syndactyly, facial dysmorphology, and a mild defect in hard palate formation. The developmental defects present in BAH null mice are similar to defects observed in knock-outs and hypomorphs of the Notch ligand Serrate-2. In this work, beta-hydroxylation of Asp residues in EGF domains is demonstrated for a soluble form of a Notch ligand, human Jagged-1. These results along with recent reports that another post-translational modification of EGF domains in Notch gene family members (glycosylation by Fringe) alters Notch pathway signaling, lends credence to the suggestion that aspartyl beta-hydroxylation may represent another post-translational modification of EGF domains that can modulate Notch pathway signaling. Previous work has demonstrated increased levels of BAH in certain tumor tissues and a role for BAH in tumorigenesis has been proposed. The role of hydroxylase in tumor formation was tested directly by crossing BAH KO mice with an intestinal tumor model, APCmin mice. Surprisingly, BAH null/APCmin mice show a statistically significant increase in both intestinal polyp size and number when compared with BAH wild-type/APCmin controls. These results suggest that, in contrast to expectations, loss of BAH catalytic activity may promote tumor formation.