Ectromelia-encoded virulence factor C15 specifically inhibits antigen presentation to CD4+ T cells post peptide loading.

Smallpox and monkeypox pose severe threats to human health. Other orthopoxviruses are comparably virulent in their natural hosts, including ectromelia, the cause of mousepox. Disease severity is linked to an array of immunomodulatory proteins including the B22 family, which has homologs in all pathogenic orthopoxviruses but not attenuated vaccine strains. We demonstrate that the ectromelia B22 member, C15, is necessary and sufficient for selective inhibition of CD4+ but not CD8+ T cell activation by immunogenic peptide and superantigen. Inhibition is achieved not by down-regulation of surface MHC- II or co-stimulatory protein surface expression but rather by interference with antigen presentation. The appreciable outcome is interference with CD4+ T cell synapse formation as determined by imaging studies and lipid raft disruption. Consequently, CD4+ T cell activating stimulus shifts to uninfected antigen-presenting cells that have received antigen from infected cells. This work provides insight into the immunomodulatory strategies of orthopoxviruses by elucidating a mechanism for specific targeting of CD4+ T cell activation, reflecting the importance of this cell type in control of the virus.

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane.

Several Hiyama cross-coupling reactions of oxasilacycloalkenes and aryl iodides are described that produce trisubstituted Z-styrenes in moderate to excellent yields. Both electron-rich and electron-poor aryl iodides are tolerated in the cross-coupling reaction. The oxasilacycloalkene coupling partners were prepared by ruthenium-catalyzed intramolecular anti-hydrosilylation of alkynols. One of the cross-coupling products was converted to a 1-benzoxocane, albeit in low yield, using an intramolecular Buchwald-Hartwig etherification. The cyclic ether produced contains the carbon skeleton of heliannuol A.

Fc-Small Molecule Antibody Mimetics.

Antibody therapeutics are a promising drug class due to their high specificity and favorable pharmacokinetics. While there are many methods for the development of antibodies specific to disease associated antigens, selecting antibodies against functional epitopes with high specificity and affinity can be difficult for certain epitopes. We describe a generalizable method for synthesizing antibody mimetics by site specifically conjugating small molecules (with high affinity and specificity to disease associated antigens) to an Fc fragment to develop drugs with the benefits of an antibody. As a proof of concept, an E269pAcPhe Fc antibody Fc fragment was produced and subsequently site-specifically labeled with a linker-modified folic acid compound to generate an Fc-folic acid antibody-mimetic. This was chosen as the model system because the high-affinity folate receptor FR-α is highly expressed in a number of cancer types including breast and ovarian cancer. The specificity of the Fc-folic acid conjugate was assessed via flowcytometry with the folate-receptor positive breast cancer cell line MDA-MB-231 by measuring Fc-folic acid binding in both the absence and presence of an excess of folic acid. Fc-small molecule conjugates could be developed into a unique class of antibody-like therapeutics.

Antibody microarrays utilizing site-specific antibody-oligonucleotide conjugates.

Protein arrays are typically made by random absorption of proteins to the array surface, potentially limiting the amount of properly oriented and functional molecules. We report the development of a DNA encoded antibody microarray utilizing site-specific antibody-oligonucleotide conjugates that can be used for cell immobilization as well as the detection of genes and proteins. This technology allows for the facile generation of antibody microarrays while circumventing many of the drawbacks of conventionally produced antibody arrays. We demonstrate that this method can be used to capture and detect SK-BR-3 cells (Her2+ breast cancer cells) at concentrations as low as 10(2) cells/mL (which is equivalent to 10 cells per 100 µL array) without the use of microfluidics, which is 100- to 10(5)-fold more sensitive than comparable techniques. Additionally, the method was shown to be able to detect cells in a complex mixture, effectively immobilizing and specifically detecting Her2+ cells at a concentration of 10(2) SK-BR-3 cells/mL in 4 × 10(6) white blood cells/mL. Patients with a variety of cancers can have circulating tumor cell counts of between 1 and 10(3) cells/mL in whole blood, well within the range of this technology.

Antibody conjugates with unnatural amino acids.

Antibody conjugates are important in many areas of medicine and biological research, and antibody-drug conjugates (ADCs) are becoming an important next generation class of therapeutics for cancer treatment. Early conjugation technologies relied upon random conjugation to multiple amino acid side chains, resulting in heterogeneous mixtures of labeled antibody. Recent studies, however, strongly support the notion that site-specific conjugation produces a homogeneous population of antibody conjugates with improved pharmacologic properties over randomly coupled molecules. Genetically incorporated unnatural amino acids (uAAs) allow unique orthogonal coupling strategies compared to those used for the 20 naturally occurring amino acids. Thus, uAAs provide a novel paradigm for creation of next generation ADCs. Additionally, uAA-based site-specific conjugation could also empower creation of additional multifunctional conjugates important as biopharmaceuticals, diagnostics, or reagents.

A genetically encoded aza-Michael acceptor for covalent cross-linking of protein-receptor complexes.

Selective covalent bond formation at a protein-protein interface potentially can be achieved by genetically introducing into a protein an appropriately "tuned" electrophilic unnatural amino acid that reacts with a native nucleophilic residue in its cognate receptor upon complex formation. We have evolved orthogonal aminoacyl-tRNA synthetase/tRNACUA pairs that genetically encode three aza-Michael acceptor amino acids, N(ε)-acryloyl-(S)-lysine (AcrK, 1), p-acrylamido-(S)-phenylalanine (AcrF, 2), and p-vinylsulfonamido-(S)-phenylalanine (VSF, 3), in response to the amber stop codon in Escherichia coli. Using an αErbB2 Fab-ErbB2 antibody-receptor pair as an example, we demonstrate covalent bond formation between an αErbB2-VSF mutant and a specific surface lysine ε-amino group of ErbB2, leading to near quantitative cross-linking to either purified ErbB2 in vitro or to native cellular ErbB2 at physiological pH. This efficient biocompatible reaction may be useful for creating novel cell biological probes, diagnostics, or therapeutics that selectively and irreversibly bind a target protein in vitro or in living cells.

Self-assembled antibody multimers through peptide nucleic acid conjugation.

With the recent clinical success of bispecific antibodies, a strategy to rapidly synthesize and evaluate bispecific or higher order multispecific molecules could facilitate the discovery of new therapeutic agents. Here, we show that unnatural amino acids (UAAs) with orthogonal chemical reactivity can be used to generate site-specific antibody-oligonucleotide conjugates. These constructs can then be self-assembled into multimeric complexes with defined composition, valency, and geometry. With this approach, we generated potent bispecific antibodies that recruit cytotoxic T lymphocytes to Her2 and CD20 positive cancer cells, as well as multimeric antibody fragments with enhanced activity. This strategy should accelerate the synthesis and in vitro characterization of antibody constructs with unique specificities and molecular architectures.

Synthesis of bispecific antibodies using genetically encoded unnatural amino acids.

Bispecific antibodies were constructed using genetically encoded unnatural amino acids with orthogonal chemical reactivity. A two-step process afforded homogeneous products in excellent yield. Using this approach, we synthesized an anti-HER2/anti-CD3 bispecific antibody, which efficiently cross-linked HER2+ cells and CD3+ cells. In vitro effector-cell mediated cytotoxicity was observed at picomolar concentrations.

Antibody Therapeutics in Oncology.

One of the newer classes of targeted cancer therapeutics is monoclonal antibodies. Monoclonal antibody therapeutics are a successful and rapidly expanding drug class due to their high specificity, activity, favourable pharmacokinetics, and standardized manufacturing processes. Antibodies are capable of recruiting the immune system to attack cancer cells through complement-dependent cytotoxicity or antibody dependent cellular cytotoxicity. In an ideal scenario the initial tumor cell destruction induced by administration of a therapeutic antibody can result in uptake of tumor associated antigens by antigen-presenting cells, establishing a prolonged memory effect. Mechanisms of direct tumor cell killing by antibodies include antibody recognition of cell surface bound enzymes to neutralize enzyme activity and signaling, or induction of receptor agonist or antagonist activity. Both approaches result in cellular apoptosis. In another and very direct approach, antibodies are used to deliver drugs to target cells and cause cell death. Such antibody drug conjugates (ADCs) direct cytotoxic compounds to tumor cells, after selective binding to cell surface antigens, internalization, and intracellular drug release. Efficacy and safety of ADCs for cancer therapy has recently been greatly advanced based on innovative approaches for site-specific drug conjugation to the antibody structure. This technology enabled rational optimization of function and pharmacokinetics of the resulting conjugates, and is now beginning to yield therapeutics with defined, uniform molecular characteristics, and unprecedented promise to advance cancer treatment.

Nicotinamide phosphoribosyltransferase can affect metastatic activity and cell adhesive functions by regulating integrins in breast cancer.

NAD(+) metabolism is an essential regulator of cellular redox reactions, energy pathways, and a substrate provider for NAD(+) consuming enzymes. We recently demonstrated that enhancement of NAD(+)/NADH levels in breast cancer cells with impaired mitochondrial NADH dehydrogenase activity, through augmentation of complex I or by supplementing tumor cell nutrients with NAD(+) precursors, inhibits tumorigenicity and metastasis. To more fully understand how aberrantly low NAD(+) levels promote tumor cell dissemination, we here asked whether inhibition of NAD(+) salvage pathway activity by reduction in nicotinamide phosphoribosyltransferase (NAMPT) expression can impact metastasis and tumor cell adhesive functions. We show that knockdown of NAMPT, the enzyme catalyzing the rate-limiting step of the NAD(+) salvage pathway, enhances metastatic aggressiveness in human breast cancer cells and involves modulation of integrin expression and function. Reduction in NAMPT expression is associated with upregulation of select adhesion receptors, particularly αvß3 and ß1 integrins, and results in increased breast cancer cell attachment to extracellular matrix proteins, a key function in tumor cell dissemination. Interestingly, NAMPT downregulation prompts expression of integrin αvß3 in a high affinity conformation, known to promote tumor cell adhesive interactions during hematogenous metastasis. NAMPT has been selected as a therapeutic target for cancer therapy based on the essential functions of this enzyme in NAD(+) metabolism, cellular redox, DNA repair and energy pathways. Notably, our results indicate that incomplete inhibition of NAMPT, which impedes NAD(+) metabolism but does not kill a tumor cell can alter its phenotype to be more aggressive and metastatic. This phenomenon could promote cancer recurrence, even if NAMPT inhibition initially reduces tumor growth.