Six recombinant human Fab fragments that were derived from the same human immunodeficiency virus type 1 (HIV-1)-infected individual and are directed against the CD4 binding site (CD4bs) of the gpl20 envelope glycoprotein were studied. A range of neutralizing activity against the HIV-1 (HXBc2) isolate was observed, with Fab b12 exhibiting the greatest potency among the Fabs tested. The neutralizing potency of Fab b12 was better than that of monoclonal whole antibodies directed against the third variable (V3) region of gpl20. To explore the basis for the efficient neutralizing activity of b12, the recognition of a panel of HIV-1 gpl20 mutants by the six Fabs was studied. The patterns of sensitivity to particular gpl20 amino acid changes were similar for all six Fabs to those seen for anti-CD4bs monoclonal antibodies derived from HIV-1-infected individuals

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We have used a binary system of repliconcompatible plasmids to test the potential for promiscuous recombination of heavy and light chains within sets of human Fab fragments isolated from combinatorial antibody libraries.

Protein Fv (pFv) is a recently described 175-kD gut-associated sialoprotein with a potent capacity for augmentation of antibody-dependent immune functions. To investigate the molecular basis for Fab-mediated binding of pFv, we evaluated a panel of 52 monoclonal IgM and found that -40% bound pFv. Whereas the majority (2 75% ) of VH3 and VH6IgM strongly bound pFv, only a small minority (< 20%) of IgM from other V H families bound pFv, and these antibodies had weaker binding interactions. Inhibition studies suggested that all binding occurred at the same (or overlapping) site(s) on pFv. Surface plasmon resonance studies demonstrated binding affinity constants up to 6.7 x 10 M-l for pFv. Biopanning of IgM and IgG Fab phage-display libraries with pFv preferentially selected for V H3 and V H6 antibodies, but also obtained certain V H4 1gM. V H sequence analyses of 36 pFv-binding antibodies revealed that binding did not correlate with CDR sequence, JH, or L chain usage. However, there was preferential selection of pFv binders with V H CDR3 of small size. These studies demonstrate that a protein which enhances immune defense in the gut has structural and functional properties similar to known superantigens. (J. Clin. Invest. 1995. 96:417-426.)

Staphylococcal protein A (SpA) is a 45-kDa bacterial membrane protein that can interact with either Fc gamma, a constant region portion of IgG, or with the Fab portion that also mediates conventional Ag binding. In recent reports, SpA has been shown to specifically interact with Fab derived from the VH3 family and is little affected by VH CDR3, JH, or light chain usage. To identify a site on SpA responsible for VH3 Fab binding, we cloned and expressed in Escherichia coli the 61 amino acid sequence of SpA that represents domain D, and this small protein exhibited both the VH3 Fab and Fc gamma binding specificities. Surface plasmon resonance measurements demonstrated that domain D and native SpA had the strongest binding interactions with an IgM-kappa encoded by the germline configuration of the VH3 gene VH26c. In contrast, the apparent affinities for Fc gamma binding were at least fivefold weaker. A variant of domain D was also created that is devoid of the three-codon insertion that distinguishes domain D from all other domains in SpA. Although this deletion did not significantly affect the VH3 Fab-mediated SpA binding activity, it did improve the affinity of Fc gamma binding by an order of magnitude. These observations characterize a site on SpA responsible for binding interactions with B cell Ag receptors that are highly analogous to that of superantigens for T cell receptors.

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San Diego’s economy, fueled by its innovation ecosystem, has experienced meteoric growth over the past several decades, with the region now ranked amongst the top life sciences clusters in the world. This growth has been inextricably linked to the military presence over the decades and the region has benefited from the symbiotic presence of both the military and private and public sector innovation partners, creating an ecosystem that may be unique in the nation. This unique combination of market forces is turbo-charging the creation of “multi-use” technologies and startups, through regional collaborations and associated programs that align the research discoveries and capabilities of universities, with the strategic needs of the government, while feeding the growth of commercial industry partners and the economy as a whole.  One key to the continued competitiveness and success of San Diego will be to strengthen this virtuous cycle, to drive productivity and propagate the impact of the engagement across multiple innovation sectors or clusters.