Labeling Antibodies.

This introduction outlines general strategies for labeling proteins, with an emphasis on methods that are used primarily for labeling antibodies. It covers the specific site of modification, cross-linker options, types of labels, and postlabeling cleanup methodology, along with the advantages and disadvantages of each method. In general, polyclonal antibodies are more versatile and resistant to activity loss than are monoclonal antibodies. Greater care must be taken when labeling monoclonal antibodies to ensure a quality conjugate. The methods outlined here can be adapted for a variety of labels including multiple labels on the same immunoglobulin. The most important consideration when undertaking an antibody labeling experiment is to maintain the activity of the antibody. This is an empirical process and will often require additional experiments to optimize the label of a particular antibody. When successful, these reagents are very useful and adaptable biomolecules. This introduction provides the reader with methods and options for producing a variety of labeled immunological tools.

Conjugation of Peptides to Thiol-Reactive Gel for Affinity Purification of Antibodies.

Thiol-reactive linkers, such as iodoacetyl or maleimide, bound to cross-linked agarose are used to attach cysteine-containing peptides covalently to this resin for use in affinity-purification protocols. It is critical to confirm that the peptide contains a reduced cysteine so that the thiol is available for conjugation to the thiol-reactive linker. The column should be sized appropriately for the amount of peptide to be used and the volume of serum to be processed. Excess binding sites on the column must be blocked with free cysteine before use.

Peptide Affinity Purification of Antibodies.

This protocol describes antibody purification using a peptide affinity column. Peptides can be designed that use naturally occurring cysteines within the protein target's primary sequence, or a cysteine can be added to either end of the peptide to provide free thiols for attachment. The peptides can then be covalently attached to resins bearing thiol-reactive linkers. The most commonly used thiol-reactive moieties are iodoacetyl and maleimide, both of which react selectively with peptides containing cysteine thiols. Although gravity can be used to cycle the antibody solution (e.g., serum) over the column (it is recommended that the antibody be cycled multiple times to obtain maximal yield), the use of a pump to apply the serum to the column in a continuous flow manner improves the yield of antibody. Similarly, washing the column after application of the antibody without and with 0.5 m NaCl should be performed with at least 20 column volumes.

Purification of Antibodies: Diethylaminoethyl (DEAE) Chromatography.

Because IgG from most species (other than rodents) tends to have an isoelectric point around neutral, two approaches can be used when separating IgG using diethylaminoethyl (DEAE) resins. When serum containing antibodies is applied to DEAE at a slightly acidic pH, the IgG flows through the column while most other serum proteins bind to the DEAE. This method is best performed using a batch method. The DEAE beads can be kept in a disposable syringe containing a polypropylene frit, a glass reactor containing a coarse-sintered glass frit, or other suitable vessel. If the antibody solution is adjusted to a basic pH of 8-8.5, then IgG binds to the DEAE resin. After washing the column, the antibody is eluted by adding a buffer of increasing ionic strength to the column. Prepacked columns of many sizes are available for the isolation of antibodies by DEAE chromatography. Alternatively, DEAE medium can be swelled or prepped according to the manufacturer's instructions and a column can be poured when needed.

Peptide-conjugated PAMAM dendrimer as a universal DNA vaccine platform to target antigen-presenting cells.

DNA-based vaccines hold promise to outperform conventional antigen-based vaccines by virtue of many unique features. However, DNA vaccines have thus far fallen short of expectations, due in part to poor targeting of professional antigen-presenting cells (APC) and low immunogenicity. In this study, we describe a new platform for effective and selective delivery of DNA to APCs in vivo that offers intrinsic immune-enhancing characteristics. This platform is based on conjugation of fifth generation polyamidoamine (G5-PAMAM) dendrimers, a DNA-loading surface, with MHC class II-targeting peptides that can selectively deliver these dendrimers to APCs under conditions that enhance their immune stimulatory potency. DNA conjugated with this platform efficiently transfected murine and human APCs in vitro. Subcutaneous administration of DNA-peptide-dendrimer complexes in vivo preferentially transfected dendritic cells (DC) in the draining lymph nodes, promoted generation of high affinity T cells, and elicited rejection of established tumors. Taken together, our findings show how PAMAM dendrimer complexes can be used for high transfection efficiency and effective targeting of APCs in vivo, conferring properties essential to generate effective DNA vaccines.

Calcium/calmodulin-dependent phosphorylation of tumor protein D52 on serine residue 136 may be mediated by CAMK2delta6.

Tumor protein D52 is expressed at relatively high levels in cells within the gastrointestinal tract that undergo classical exocytosis and is overexpressed in several cancers. Current evidence supports a role for D52 in the regulation of vesicular trafficking. D52 function(s) are regulated by calcium-dependent phosphorylation; however, the intracellular mechanisms that mediate this process are not well characterized. The goal of this study was to identify the calcium-dependent phosphorylation site(s) in D52 and to characterize the protein kinase(s) that mediate this phosphorylation. Using mass spectrometry and site-directed mutagenesis, we identified a single amino acid residue, S(136), that undergoes increased phosphorylation upon elevation of intracellular Ca(2+) concentration. A phosphospecific antibody (pS(136)) was produced and used to characterize D52 kinase activity in gastric mucosal, colonic T84, and HEK293 cells. By using D52 as a substrate, a protein kinase with a molecular weight (M(r)) of approximately 50 kDa was identified with "in gel" assays. This kinase comigrated with rat brain calcium/calmodulin-dependent protein kinase (CAMK2)alpha cross-reacted with pan-specific CAMK2 antibodies as well as with anti-active CAMK2 (pT(286/287)) antibody when activated. Carbachol-stimulated phosphorylation of S(136) was inhibited by the CAMK2 inhibitor KN93 (IC(50) 38 microM) and by the calmodulin antagonist W7 (IC(50) 3.3 nM). A previously uncharacterized CAMK2 isoform, CAMK2delta6, which has the same domain structure and M(r) as CAM2alpha, was identified in gastric mucosa by RT-PCR. The cloned, expressed protein comigrated with D52 kinase and colocalized with D52 protein in T84 and HEK293 cells. These findings support a role for CAMK2delta6 in the mediation of D52 phosphorylation.

Childhood anxiety in a diverse primary care population: parent-child reports, ethnicity and SCARED factor structure.

OBJECTIVE: To explore in a multiethnic primary care population the impact of child gender and of race/ethnicity on parent and child reports of school-age anxiety and on the factor structure of the Screen for Childhood Anxiety and Related Emotional Disorders (SCARED). METHOD: A consecutive sample of 515 children (8 to <13 years) and their parent presenting for primary care completed self-report (C) and parent-report (P) versions of the SCARED-41. RESULTS: Neither SCARED scores nor parent-child difference varied significantly with race/ethnicity. Predictors of higher SCARED scores were less parental education, younger child age and female gender. Exploratory factor analysis conducted separately for SCARED-C and SCARED-P yielded four factors. There was large variation in factor structure between SCARED-C and SCARED-P and across ethnic and gender subgroups, greatest for somatic/panic/generalized anxiety and Hispanic children. CONCLUSIONS: Primary care triage of anxious children requires data from both the parent and child and must go beyond cross-sectional symptom inventories. Clinicians must elicit from each family their perhaps culturally bound interpretation of the child's somatic and psychological symptoms.

Identification of surface-exposed components of MOMP of Chlamydia trachomatis serovar F.

The identification of surface-exposed components of the major outer membrane protein (MOMP) of Chlamydia is critical for modeling its three-dimensional structure, as well as for understanding the role of MOMP in the pathogenesis of Chlamydia-related diseases. MOMP contains four variable domains (VDs). In this study, VDII and VDIV of Chlamydia trachomatis serovar F were proven to be surface-located by immuno-dot blot assay using monoclonal antibodies (MAbs). Two proteases, trypsin and endoproteinase Glu-C, were applied to digest the intact elementary body of serovar F under native conditions to reveal the surface-located amino acids. The resulting peptides were separated by SDS-PAGE and probed with MAbs against these VDs. N-terminal amino acid sequencing revealed: (1) The Glu-C cleavage sites were located within VDI (at Glu61) and VDIII (at Glu225); (2) the trypsin cleavage sites were found at Lys79 in VDI and at Lys224 in VDIII. The tryptic peptides were then isolated by HPLC and analyzed with a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer and a quadrupole-orthogonal-TOF mass spectrometer coupled with a capillary liquid chromatograph. Masses and fragmentation patterns that correlated to the peptides cleaved from VDI and VDIII regions, and C-terminal peptides Ser333-Arg358 and Ser333-Lys350 were observed. This result demonstrated that these regions are surface-exposed. Data derived from comparison of nonreduced outer membrane complex proteolytic fragments with their reduced fractions revealed that Cys26, 29, 33, 116, 208, and 337 were involved in disulfide bonds, and Cys26 and 337, and 116 and 208 were paired. Based on these data, a new two-dimensional model is proposed.

Th-cytotoxic T-lymphocyte chimeric epitopes extended by Nepsilon-palmitoyl lysines induce herpes simplex virus type 1-specific effector CD8+ Tc1 responses and protect against ocular infection.

Molecularly defined vaccine formulations capable of inducing antiviral CD8+ T-cell-specific immunity in a manner compatible with human delivery are limited. Few molecules achieve this target without the support of an appropriate immunological adjuvant. In this study, we investigate the potential of totally synthetic palmitoyl-tailed helper-cytotoxic-T-lymphocyte chimeric epitopes (Th-CTL chimeric lipopeptides) to induce herpes simplex virus type 1 (HSV-1)-specific CD8+ T-cell responses. As a model antigen, the HSV-1 glycoprotein B498-505 (gB498-505) CD8+ CTL epitope was synthesized in line with the Pan DR peptide (PADRE), a universal CD4+ Th epitope. The peptide backbone, composed solely of both epitopes, was extended by N-terminal attachment of one (PAM-Th-CTL), two [(PAM)2-Th-CTL], or three [(PAM)3-Th-CTL] palmitoyl lysines and delivered to H2b mice in adjuvant-free saline. Potent HSV-1 gB498-505-specific antiviral CD8+ T-cell effector type 1 responses were induced by each of the palmitoyl-tailed Th-CTL chimeric epitopes, irrespective of the number of lipid moieties. The palmitoyl-tailed Th-CTL chimeric epitopes provoked cell surface expression of major histocompatibility complex and costimulatory molecules and production of interleukin-12 and tumor necrosis factor alpha proinflammatory cytokines by immature dendritic cells. Following ocular HSV-1 challenge, palmitoyl-tailed Th-CTL-immunized mice exhibited a decrease of virus replication in the eye and in the local trigeminal ganglion and reduced herpetic blepharitis and corneal scarring. The rational of the molecularly defined vaccine approach presented in this study may be applied to ocular herpes and other viral infections in humans, providing steps are taken to include appropriate Th and CTL epitopes and lipid groups.

Identification of protein components in human acquired enamel pellicle and whole saliva using novel proteomics approaches.

Precursor proteins of the acquired enamel pellicle derive from glandular and non-glandular secretions, which are components of whole saliva. The purpose of this investigation was to gain further insights into the characteristics of proteins in whole saliva and in vivo formed pellicle components. To maximize separation and resolution using only micro-amounts of protein, a two-dimensional gel electrophoresis system was employed. Protein samples from parotid secretion, submandibular/sublingual secretion, whole saliva, and pellicle were subjected to isoelectric focusing followed by SDS-PAGE. Selected protein spots were excised, subjected to "in-gel" trypsin digestion, and examined by mass spectrometry (MS). The data generated, including peptide maps and tandem MS spectra, were analyzed using protein data base searches. Components identified in whole saliva include cystatins (SA-III, SA, and SN), statherin, albumin, amylase, and calgranulin A. Components identified in pellicle included histatins, lysozyme, statherin, cytokeratins, and calgranulin B. The results showed that whole saliva and pellicle have more complex protein patterns than those of glandular secretions. There are some similarities and also distinct differences between the patterns of proteins present in whole saliva and pellicle. MS approaches allowed identification of not only well characterized salivary proteins but also novel proteins not previously identified in pellicle.

Tandem mass spectrometry for structural characterization of proline-rich proteins: application to salivary PRP-3.

Proline-rich proteins (PRPs), including collagens, complement 1q, and salivary PRPs, are unusually difficult to sequence by mass spectrometry, due to the high efficiency of cleavage at the amide bond on the N-terminal of proline residues and the consequently low relative abundance of fragment arising from cleavages at other amide bonds. To fully characterize these proteins by mass spectrometry, specialized approaches to fragmentation are needed for the peptides with high proline content. Our work reported herein focused on the analysis of the set of peptides derived by tryptic cleavage of the salivary protein PRP-3. Two methods of fragmentation were compared: Collision-induced dissociation (CID) and electron capture dissociation (ECD). The data obtained demonstrated that ECD spectra of peptides containing more than 30% proline residues are simpler and easier to interpret than are CID spectra of those peptides. Factors that limit the two methods of fragmentation include the complexity of information contained in the CID spectra and the low efficiency of ECD processes. A complementary approach using both decomposition methods provides more complete and interpretable sequence information and yielded >93% sequence coverage for the 11-kDa PRP-3 isolated from human saliva.