Identification of tumors which over-express Epidermal Growth Factor Receptor (EGFR) is important in selecting patients for anti-EGFR therapies. Enzymatic bioconjugation was used to introduce positron-emitting radionuclides (89Zr, 64Cu) into an...

Background: In protein drug development, in vitro molecular optimization or protein maturation can be used to modify protein properties. One basic approach to protein maturation is the introduction of random DNA mutations into the target gene sequence to produce a library of variants that can be screened for the preferred protein properties. Unfortunately, the capability of this approach has been restricted by deficiencies in the methods currently available for random DNA mutagenesis and library generation. Current DNA based methodologies generally suffer from nucleotide substitution bias that preferentially mutate particular base pairs or show significant bias with respect to transitions or transversions. In this report, we describe a novel RNAbased random mutagenesis strategy that utilizes Qβ replicase to manufacture complex mRNA libraries with a mutational spectrum that is close to the ideal.

Ricin is a potent glycoprotein toxin that is structurally composed of two subunits joined via a disulfide bond: a ~30 kDa subunit A (RTA) and a ~32 kDa subunit B (RTB). There are fears of ricin being used as a weapon for warfare and terrorism and, as such, there is an increasing need for the development of immunodiagnostic reagents targeted towards this toxin. This article describes the production and characterization of a panel of six ricinspecific monoclonal IgG antibodies (mAbs), previously selected based upon their ability to inhibit ricin-mediated killing of cultured cells. Subsequent epitope binding analysis using the surface plasmon resonance (SPR) array biosensor (ProteOn XPR36) indicated three distinct, non-competitive binding epitopes ("bins"). The association (k a ) and dissociation (k d ) rate constants and binding affinities (K D ) of each of the mAbs to ricin were also determined by SPR using Biacore T100 instrument. Affinities (K D ) ranged from 0.1 nM to 9 nM. We present the coding sequences of the variable domains of the six mAbs, the expression, kinetic and cytotoxicity assays for two recombinant Fab (rFab) fragments and demonstrate a rFab affinity improvement by chain-shuffling. Together, these antibodies and constituent rFabs represent a panel of reagents for high-affinity recognition of ricin with potential national security biosensor applications. OPEN ACCESS Antibodies 2014, 3 216

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