Denying the Truth Does Not Change the Facts: A Systematic Analysis of Pseudoscientific Denial of Complex Regional Pain Syndrome

Purpose

Several articles have claimed that complex regional pain syndrome (CRPS) does not exist. Although a minority view, it is important to understand the arguments presented in these articles. We conducted a systematic literature search to evaluate the methodological quality of articles that claim CRPS does not exist. We then examined and refuted the arguments supporting this claim using up-to-date scientific literature on CRPS.

Methods

A systematic search was conducted in MEDLINE, EMBASE and Cochrane CENTRAL databases. Inclusion criteria for articles were (a) a claim made that CRPS does not exist or that CRPS is not a distinct diagnostic entity and (b) support of these claims with subsequent argument(s). The methodological quality of articles was assessed if possible.

Results

Nine articles were included for analysis: 4 narrative reviews, 2 personal views, 1 letter, 1 editorial and 1 case report. Seven points of controversy were used in these articles to argue that CRPS does not exist: 1) disagreement with the label “CRPS”; 2) the “unclear” pathophysiology; 3) the validity of the diagnostic criteria; 4) CRPS as a normal consequence of immobilization; 5) the role of psychological factors; 6) other identifiable causes for CRPS symptoms; and 7) the methodological quality of CRPS research.

Conclusion

The level of evidence for the claim that CRPS does not exist is very weak. Published accounts concluding that CRPS does not exist, in the absence of primary evidence to underpin them, can harm patients by encouraging dismissal of patients’ signs and symptoms.

First Report of Citrus leprosis virus Nuclear Type in Sweet Orange in Colombia

Colombia is ranked 18th in the world in citrus production and contributed 0.9% of the total world share. Among four important citrus-producing regions of Colombia, the Orinoco region (3 to 6°N, 68 to 74°W) consists of two citrus-producing states, Meta and Casanare. Citrus leprosis is the most important viral disease of citrus in Colombia (1,3). Three types of Citrus leprosis virus (CiLV) infect citrus, producing leprosis-like lesion symptoms. Two of the three CiLV species, Citrus leprosis virus cytoplasmic type (CiLV-C) and cytoplasmic type 2 (CiLV-C2), produce particles only in the cytoplasm (3). The other species, Citrus leprosis virus nuclear type (CiLV-N), produces particles in both the cytoplasm and nucleus (4). CiLV-C is more prevalent and destructive while CiLV-N has been reported only in Brazil, Panama, and Mexico (4). Interestingly, both CiLV-C and -C2 were reported from the same regions of Meta and Casanare States in Colombia in 2004 and 2012 (1,3). CiLV-C lesions are usually rounded (initially 2 to 3 mm in diameter and extending up to 30 mm), have dark-brown or greenish central chlorotic spots, and are surrounded by yellow halos. CiLV-N lesions have been described as smaller in size and form three well-defined regions including a necrotic center with an intermediate orange color halo and an outer chlorotic halo (2). In 2013, 'Valencia' sweet orange (Citrus sinensis L.) leaves with suspected CiLV-N symptoms were collected from 8 plants in Casanare State and shipped under permit to the USDA-APHIS-PPQ-CPHST, Beltsville, MD. Total RNA from symptomatic and healthy sweet orange leaves were extracted using the RNeasy Plant Mini Kit (Qiagen, Valencia, CA). RT-PCR primers specific to CiLV-C, CiLV-C2 (3), and CiLV-N nucleocapsid (N) (CiLV-N-NPF: 5'-ATGGCTAACCCAAGTGAGATCGATTA-3'; CiLV-N-NPR: 5'-AGTTGCCTTGAGATCATCACATTGGT-3') and putative matrix protein (M) genes (CiLV-N-MF: 5'-ATGTCTAAACAGATTAATATGTGCACTGTG-3'; CiLV-N-MR: 5'-CTAACCACTGGGTCCCGC-3') were utilized to identify the CiLV associated with the leprosis-affected leaf samples from Casanare. RT-PCR with CiLV-C primers failed to produce any amplicon, but CiLV-N primers successfully amplified the partial N gene (681 bp) and entire M gene (552 nt) amplicons from multiple leaves of all leprosis samples. In addition, a 795-bp amplicon specific to CiLV-C2 also was amplified from the CiLV-N suspected samples. Similar results were obtained when the vector, flat spider mite (Brevipalpus spp.) total RNA was used as template for RT-PCR. For further confirmation, each amplicon was cloned and sequenced. Sequencing of the N and M gene amplicons of CiLV-N (accession nos. KJ195893 and KJ195894) and coat protein gene of CiLV-C2 showed 97 to 99% nucleotide sequence identity with the CiLV-N M2345 isolate sequence (KF209275) from Mexico (4) and CiLV-C2 L147V1 isolate sequence (JX000024) from Colombia (3), respectively. Phylogenetic analyses of these N and M protein gene sequences confirmed a mixed infection of the same plant with two viruses, one from an unassigned new genus Dichorhavirus (CiLV-N) and another from genus Cilevirus (CiLV-C2). This is the first report of CiLV-N in Colombia, and also the first report of an occurrence of CiLV-N in mixed infection with CiLV-C2. All three known species of CiLV occur in the Orinoco region of Colombia. References: (1) M. G. León et al. Plant Dis. 90: 682, 2006. (2) J. P. R. Marques et al. Anais da Academia Brasileira de Ciências 82:501, 2010. (3) A. Roy et al. Phytopathology 103:488, 2013. (4) A. Roy et al. Genome Announc. 1(4): e00519-13, 2013.

Development of Primers and Probes for Genus and Species Specific Detection of 'Candidatus Liberibacter Species' by Real-Time PCR

Huanglongbing (HLB), also known as citrus greening, is currently the most devastating disease impacting citrus production. The disease is associated with three different 'Candidatus Liberibacter species', 'Ca. Liberibacter asiaticus', 'Ca. Liberibacter americanus', and 'Ca. Liberibacter africanus', which induce similar and overlapping symptoms. When HLB-symptomatic trees are tested, one of the Candidatus Liberibacters is normally detected by conventional or real-time PCR (qPCR). The most widely used assays use primers and probes based on the 16S ribosomal RNA (rRNA) gene. The 16S rRNA-based assays to detect the three species are species-specific and must be performed sequentially. We describe a single assay that detected all species of 'Ca. Liberibacter' at the genus level, providing increased convenience. Recent molecular analyses of 'Ca. Liberibacter species' and other bacteria suggest that the rpoB gene (encoding the β-subunit of RNA polymerase) provides an alternative target for bacterial identification. We report here the design of a single pair of degenerate primers and a hybridization probe corresponding to the rpoB region and their application for the detection of all three citrus 'Ca. Liberibacter species', enabling detection of 'Ca. Liberibacter' at the genus level. In addition, species-specific primers and probes based on the rplJ/rplK genes were designed and used for detection at the species level in a multiplexed format. Both the genus- and species-specific assays were validated in both SYBR Green I and TaqMan formats, and with both plant and insect extracts that contained the pathogen. These one-step qPCR diagnostic methods are useful for the detection of all species of Liberibacter infecting citrus. In addition, the degenerate genus-specific primers and probe successfully detected 'Ca. Liberibacter solanacearum', a psyllid-transmitted pathogen associated with disease in tomato, carrot, and potato.

Acquisition and Transmissibility of U.S. Soybean dwarf virus Isolates by the Soybean Aphid, Aphis glycines

Soybean dwarf virus (SbDV) exists as several distinct strains based on symptomatology, vector specificity, and host range. Originally characterized Japanese isolates of SbDV were specifically transmitted by Aulacorthum solani. More recently, additional Japanese isolates and endemic U.S. isolates have been shown to be transmitted by several different aphid species. The soybean aphid, Aphis glycines, the only aphid that colonizes soybean, has been shown to be a very inefficient vector of some SbDV isolates from Japan and the United States. Transmission experiments have shown that the soybean aphid can transmit certain isolates of SbDV from soybean to soybean and clover species and from clover to clover and soybean with long acquisition and inoculation access periods. Although transmission of SbDV by the soybean aphid is very inefficient, the large soybean aphid populations that develop on soybean may have epidemiological potential to produce serious SbDV-induced yield losses.

Murraya paniculata and Related Species as Potential Hosts and Inoculum Reservoirs of 'Candidatus Liberibacter asiaticus', Causal Agent of Huanglongbing

Huanglongbing (HLB), considered to be the most serious insect-vectored bacterial disease of citrus, is transmitted in nature by the Asian citrus psyllid Diaphorina citri and the African citrus psyllid Trioza erytreae. D. citri was discovered in southern Florida in 1998 and the HLB disease in 2005. Both have become established throughout citrus-producing areas of Florida. Murraya species are widely grown in southern Florida as ornamental hedges and are readily colonized by D. citri vectors. Colonies of D. citri, isolates of 'Candidatus Liberibacter asiaticus' from Taiwan and Florida, and the Murraya species were established in the BSL-3 biosecurity facility at Fort Detrick. In controlled inoculation experiments, D. citri transmitted 'Ca. L. asiaticus' into M. paniculata (34/36 plants) and M. exotica (22/23 plants), but not into Bergera (Murraya) koenigii. Disease symptoms rarely developed in Murraya plants; however, positive infections were determined by conventional and real-time polymerase chain reaction (PCR). Back-inoculations of 'Ca. L. asiaticus' from M. paniculata to Madam Vinous sweet orange resulted in disease development in 25% of the inoculated plants. Considerable variability was observed in infection rates, titer, and persistence of 'Ca. L. asiaticus' in infected Murraya.

Cultivation of 'Candidatus Liberibacter asiaticus', 'Ca. L. africanus', and 'Ca. L. americanus' associated with huanglongbing

A new medium designated Liber A has been designed and used to successfully cultivate all three 'Candidatus Liberibacter spp.,' the suspect causative agents of huanglongbing (HLB) in citrus. The medium containing citrus vein extract and a growth factor sustained growth of 'Ca. Liberibacter spp.' for four or five single-colony transfers before viability declined. Colonies, positive for 'Ca. L. asiaticus' by a 16s-based rDNA real-time polymerase chain reaction (RT-PCR) assay and sequencing, were irregular-shaped, convex, and 0.1 to 0.3 mm after 3 to 4 days. Suspect 'Ca. L. asiaticus' and 'Ca. L. americanus' cells were observed in infected tissue and on agar culture by scanning electron microscopy. The cells were ovoid to rod shaped, 0.3 to 0.4 by 0.5 to 2.0 microm, often with fimbriae-like appendages. Two strains of 'Ca. L. asiaticus' and one of 'Ca. L. americanus' grown on Liber A medium were pathogenic on citrus and could be isolated from noninoculated tissues of inoculated trees and seedlings 9 and 2 months later, respectively. The identity was confirmed by RT-PCR and 16s rDNA sequencing. This is the first report of the cultivation and pathogenicity of 'Ca. L. asiaticus' and 'Ca. L. americanus' associated with symptoms of HLB.

Prunus Host Range of Plum pox virus (PPV) in the United States by Aphid and Graft Inoculation

Plum pox (Sharka) is a serious virus disease of stone fruits caused by the Plum pox virus (PPV). To determine which species could function as potential hosts and virus reservoirs, we used aphid transmission and bud or chip grafting to evaluate the susceptibility of commercial, ornamental, and wild Prunus species to isolates of PPV found in Pennsylvania, USA. Following inoculation, test trees were observed for symptoms, analyzed by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), back-assayed to healthy peach, and followed through at least four cold-induced dormancy (CID) cycles over 4 years. Thirty-one of 33 Prunus species and cultivars were systemically infected following aphid transmission. Systemic infection could not be detected in P. cerasus (sour cherry) and P. × 'Snofozam' (Snow Fountains) despite repeated aphid inoculation attempts. Following grafting of PPV-infected budwood, all 40 species and varieties became infected, although species differed in their susceptibility. Within most species, some individual plants remained PPV negative throughout the study despite repeated inoculations. Infection in some species could be detected only through quantitative reverse transcription (RT)-PCR. Most species displayed clear symptoms, were highly positive by ELISA and RT-PCR, and could be back-inoculated into peach seedlings following CID. Our results indicate that a wide range of native and ornamental Prunus species are susceptible to U.S. isolates of PPV-D.

Structure-function analysis of the ADAM family of disintegrin-like and metalloproteinase-containing proteins (review)

The ADAMs belong to a disintegrin-like and metalloproteinase-containing protein family that are zinc-dependent metalloproteinases. These proteins share all or some of the following domain structure: a signal peptide, a propeptide, a metalloproteinase, a disintegrin, a cysteine-rich, and an epidermal growth factor (EGF)-like domains, a transmembrane region, and a cytoplasmic tail. ADAMs are widely distributed in many organs, tissues, and cells, such as brain, testis, epididymis, ovary, breast, placenta, liver, heart, lung, bone, and muscle. These proteins are capable of four potential functions: proteolysis, adhesion, fusion, and intracellular signaling. Because the number of ADAM genes has grown rapidly and the biological functions of most members are unclear, this review analyzes the protein structures and functions, their activation and processing, their known and potential activities, and their evolutionary relationships. A sequence alignment of human ADAMs is compiled and their homology and physical data are calculated. The conceivable functions of ADAMs in reproduction, development, and diseases are also discussed.

Identification, characterization, and relatedness of luteovirus isolates from forage legumes

ABSTRACT Virus isolates from forage legumes collected from eight different states were identified as luteoviruses closely related to soybean dwarf luteovirus dwarfing (SbDV-D) and yellowing (SbDV-Y) described in Japan. All isolates produced reddened leaf margins in subterranean clover and were transmitted in a persistent manner by Acrythosiphon pisum, but not by Aulacorthum solani. Specific monoclonal antibodies raised against SbDV-Y were differentially reactive with endemic isolates. Immunoblots probed with a SbDV-D polyclonal antiserum showed single 26-kDa coat protein bands, confirming close serological relatedness to SbDV. Analyses of genomic and subgenomic double-stranded RNAs and northern blot analyses confirmed genomic relatedness to SbDV. Based on our results, we conclude that the U.S. luteovirus isolates studied comprise a strain or strains of the soybean dwarf virus that have clovers as common hosts and the pea aphid as a common vector.

Cryptosporidium parvum sporozoite pellicle antigen recognized by a neutralizing monoclonal antibody is a beta-mannosylated glycolipid

The protozoan parasite Cryptosporidium parvum is an important cause of diarrhea in humans, calves, and other mammals worldwide. No approved vaccines or parasite-specific drugs are currently available for the control of cryptosporidiosis. To effectively immunize against C. parvum, identification and characterization of protective antigens are required. We previously identified CPS-500, a conserved, neutralization-sensitive antigen of C. parvum sporozoites and merozoites defined by monoclonal antibody 18.44. In the present study, the biochemical characteristics and subcellular location of CPS-500 were determined. CPS-500 was chloroform extractable and eluted with acetone and methanol in silicic acid chromatography, consistent with being a polar glycolipid. Following chloroform extraction and silicic acid chromatography, CPS-500 was isolated by high-pressure liquid chromatography for glycosyl analysis, which indicated the presence of mannose and inositol. To identify which component of CPS-500 comprised the neutralization-sensitive epitope recognized by 18.44, the ability of the monoclonal antibody to bind CPS-500 treated with proteases, or with alpha- or beta-glycosidases, was determined. Monoclonal antibody 18.44 did not bind antigen treated with beta-D-mannosidase but did bind antigen treated with alpha-D-mannosidase, other alpha- or beta-glycosidases, or a panel of proteases. These data indicated that the target epitope was dependent on terminal beta-D-mannopyranosyl residues. By immunoelectron microscopy, 18.44 binding was localized to the pellicle and an intracytoplasmic tubulovesicular network in sporozoites. Monoclonal antibody 18.44 also bound to antigen deposited and released onto substrate over the course travelled by gliding sporozoites and merozoites. Surface localization, adhesion and release during locomotion, and neutralization sensitivity suggest that CPS-500 may be involved in motility and invasion processes of the infective zoite stages.

Structure-function relations of heparin-mimetic sulfated xylan oligosaccharides: inhibition of human immunodeficiency virus-1 infectivity in vitro

Heparins/heparan sulfates modulate the function of proteins and cell membranes in numerous biological systems including normal and disease processes in humans. Heparin has been used for many years as an anticoagulant, and anticoagulant heparin-mimetics were developed several decades ago by chemical sulfation of non-mammalian polysaccharides, e.g., an antithrombotic sulfated xylan. This pharmaceutical, which comprises a mixture of sulfated oligoxylans, also mimics most other biological actions of natural heparins in vitro, including inhibition of the human immunodeficiency virus, but the molecular basis for these actions has been unclear. Here, numerous Components of the sulfated oligoxylan mixture were isolated and when bioassayed in the case of anti-HIV-1 infectivity revealed that a structural specificity underlines the capacity of sulfated xylan to inhibit HIV-1, rather than a non-specific mechanism. Components were isolated by chromatographic fractionation through Bio-Gel P10 in 0.5 M ammonium bicarbonate. This fractionation revealed an elution range associated with apparent molecular weights of approximately 22000 to <1500 relative to standard heparin and heparan sulfates and newly prepared sulfated oligosaccharide standards. Components were characterized by metachromatic absorption spectroscopy, ultracentrifugation, GlcA analysis, and potency against HIV-1 infectivity, both in the tetrazolium cytotoxicity assay and in syncytium-forming assays, in CD4-lymphocytes. Structural specificity was indicated by the differential potencies exhibited by the Components: Highest activity (cytotoxicity) was exhibited by Components in the chromatographic region > or = approximately 5500 in mass (50% effective (inhibitory) concentration = 0.5-0.7 microg ml(-1) in the first fractionation series, and 0.1-0.5 microg ml(-1) in a second series). The potency declined sharply below approximately 5400 in mass, but with an exception; a second structure exhibiting relatively high potency eluted among low-mass oligosaccharides which had an average size of approximately a nonomer. Components displayed differential potencies also against the syncytium-forming infectivity of HIV-1. The high potency against syncytium-formation was retained by Components down to a minimum size of about 4500 in mass, smaller than the > or = approximately 5400 required above. One in ten of the beta1,4-linked xyloses in the native xylan are substituted with a monomeric alpha1,2 DGlcA branch. We have speculated that pharmaceutical actions of sulfated xylan might be related to structures involving the alpha-D linked substituents and this was examined using a space-filling model of a sulfated octaxylan and by analyses of Components for GlcA content. Understanding structure/function relations in the heparin-like actions of these agents would be of general significance for the careful examination of their potential clinical usefulness in many human processes modulated by heparins, including AIDS.

Protective monoclonal antibody defines a circumsporozoite-like glycoprotein exoantigen of Cryptosporidium parvum sporozoites and merozoites

The apicomplexan protozoan parasite Cryptosporidium parvum causes a diarrheal disease in humans and other mammals for which specific therapy and immunoprophylaxis are unavailable. Passive immunization with Abs against whole C. parvum organisms has variable efficacy in immunocompromised or neonatal hosts. Because apical and surface-exposed zoite Ags of the Apicomplexa are critical to infectivity and targets of protective immunity, we examined the ability of mAbs generated against such Ags in C. parvum sporozoites to passively protect against infection and identify biologically relevant parasite molecules. A panel of mAbs was produced against affinity-purified native Ags using sporozoite apical- and surface-reactive mAb C4A1 as binding ligand. One resulting mAb, designated 3E2, elicited prominent morphologic changes in sporozoites and merozoites characterized by rapid and progressive formation, posterior movement, and release of membranous Ag-mAb precipitates. These changes had a striking resemblance to the malarial circumsporozoite precipitate (CSP) reaction. Sporozoite infectivity was completely neutralized after in vitro exposure to 3E2 and the CSP-like reaction. Furthermore, orally administered 3E2 completely prevented or markedly reduced infection in neonatal BALB/c mice. 3E2 bound to apical complex and surface molecules of zoites and was demonstrated in membranous precipitates by immunoelectron microscopy. In Western blots, 3E2 recognized multiple 46 to approximately 770 kDa sporozoite Ags and an approximately 1300-kDa Ag designated CSL, also expressed by merozoites. CSL was characterized as a soluble glycoprotein exoantigen released by infectious sporozoites. Further, CSL was determined to be the molecular species mechanistically involved in the CSP-like reaction by its identification in SDS-PAGE gels and Western blots of purified membranous precipitates. These findings indicate that CSL has a functional role in sporozoite infectivity and is a candidate molecular target for passive or active immunization against cryptosporidiosis.

Protective monoclonal antibody defines a circumsporozoite-like glycoprotein exoantigen of Cryptosporidium parvum sporozoites and merozoites

The apicomplexan protozoan parasite Cryptosporidium parvum causes a diarrheal disease in humans and other mammals for which specific therapy and immunoprophylaxis are unavailable. Passive immunization with Abs against whole C. parvum organisms has variable efficacy in immunocompromised or neonatal hosts. Because apical and surface-exposed zoite Ags of the Apicomplexa are critical to infectivity and targets of protective immunity, we examined the ability of mAbs generated against such Ags in C. parvum sporozoites to passively protect against infection and identify biologically relevant parasite molecules. A panel of mAbs was produced against affinity-purified native Ags using sporozoite apical- and surface-reactive mAb C4A1 as binding ligand. One resulting mAb, designated 3E2, elicited prominent morphologic changes in sporozoites and merozoites characterized by rapid and progressive formation, posterior movement, and release of membranous Ag-mAb precipitates. These changes had a striking resemblance to the malarial circumsporozoite precipitate (CSP) reaction. Sporozoite infectivity was completely neutralized after in vitro exposure to 3E2 and the CSP-like reaction. Furthermore, orally administered 3E2 completely prevented or markedly reduced infection in neonatal BALB/c mice. 3E2 bound to apical complex and surface molecules of zoites and was demonstrated in membranous precipitates by immunoelectron microscopy. In Western blots, 3E2 recognized multiple 46 to approximately 770 kDa sporozoite Ags and an approximately 1300-kDa Ag designated CSL, also expressed by merozoites. CSL was characterized as a soluble glycoprotein exoantigen released by infectious sporozoites. Further, CSL was determined to be the molecular species mechanistically involved in the CSP-like reaction by its identification in SDS-PAGE gels and Western blots of purified membranous precipitates. These findings indicate that CSL has a functional role in sporozoite infectivity and is a candidate molecular target for passive or active immunization against cryptosporidiosis.

Biophysical characterization of a recombinant soluble interleukin 2 receptor (Tac). Evidence for a monomeric structure

The interleukin 2 receptor (IL2R) plays a prominent role in the biology of T cells, B cells, and NK cells during activation. Of the three chains described, the alpha-chain of the receptor (Tac; IL2R alpha; CD25) is the most subject to regulation and is shed from the surface of activated cells to generate a soluble form in serum and tissues. Conflicting results have been reported on the native structure of soluble Tac, suggesting variously a monomer, a dimer, or higher noncovalent forms, spawning different models for its mechanism of action. We similarly show a large M(r)(app) by HPLC sieving chromatography, suggesting a tetrameric form. However, stoichiometry-ordered size (SOS) analysis of antibody-antigen complexes indicated only a single epitope per Tac molecule, compatible with a monomeric form. This larger M(r)(app) also conflicted with prior in vivo data showing rapid filtration of soluble Tac through the renal glomerulus that was not expected of a larger complex. Using different solvents, denaturants, and columns in the chromatography suggested that the elevated M(r)(app) values were an artifact of solute-column interactions, termed "ionic exclusion", rather than reflecting larger native structures. Analytical ultracentrifugation using a new type of analysis specific to glycoproteins demonstrated monomeric masses under all salt conditions with no tendency to form dimers or higher aggregates. Finally, circular dichroism spectroscopy showed no salt-dependent changes to suggest conformational alterations that might correlate with mobility changes on high pressure liquid chromatography. We conclude therefore that Tac is monomeric under physiologic conditions. Assessments of higher molecular weight for the purified soluble protein by other methods may be explained by the highly acidic nature of the molecule, which hampers matrix penetration with chromatographic media and by the high carbohydrate content and low partial specific volumes that accelerate the molecule in sedimentation media relative to pure protein standards.

Three isoforms of human myelin basic protein: purification and structure

Myelin basic protein (MBP) occurs in multiple forms. Three of these isoforms from human MBP (HMBP) have been highly purified. HMBP, component 1 (18.5 kDa HMBP-1), was purified by ion-exchange chromatography at pH 10.6 in 2 M urea. During this ion-exchange chromatography, a fraction (Fraction 3), which contained HMBP component 3 (monophosphorylated or deamidated 18.5 kDa) and 17.2 kDa HMBP, was collected and further purified by fast protein liquid chromatography, which separated 17.2 kDa HMBP and HMBP component 3. When the latter was subjected to limited thrombic digestion, all of HMBP component 3 not phosphorylated at theonine 98 was cleaved. This digestion mixture was separated on Sephadex, and yielded pure component 3, monophosphorylated at theonine 98 (HMBP 3pT98), for which phosphate analysis yielded approximately 1 mole P/mole protein, and NMR showed only one phosphorylation site present. Circular dichroism (CD) studies were carried out on dilute solutions of HMBP-1 (18.5 kDa), 17.2 kDa HMBP, and HMBP3pT98 (phosphorylated 18.5 kDa). The CD spectrum of HMBP-1 was similar to that reported for rabbit MBP-1 and bovine MBP-1, but the spectra of 17.2 kDa HMBP and HMBP 3pT98 were distinctly different from HMBP-1. When analyzed by best-fit computations, 17.2 kDa HMBP showed about a 9% increase of ordered structure, and a greater increase, about 12%, was estimated for HMBP3pT98, attributable to beta-structure and beta turn.

Relation between structure and immunologic properties of the Vi capsular polysaccharide

The Vi capsular polysaccharide of Salmonella typhi is a linear homopolymer of poly-alpha(1----4)GalNAcp variably O acetylated at the C-3 position. Serum antibodies elicited by this antigen confer protective immunity against typhoid fever. The relation between the immunologic properties and structure of Vi was investigated by carboxyl reduction, O deacetylation, and acid hydrolysis. The immunogenicity of Vi was closely related to its degree of O acetylation. Partial O deacetylation slightly increased immunogenicity; complete O deacetylation eliminated the immunogenicity of Vi. O-deacetylated Vi, however, still reacted with antisera prepared by injection of whole bacteria. Carboxyl reduction, in contrast, had a comparatively slight effect upon both the immunogenicity and antigenicity of Vi. Retention levels of antigenicity after acid treatment were greater for both the native and carboxyl-reduced Vi than for the O-deacetylated product. The Courtauld-Koltun space-filling model of a pentamer of Vi demonstrated that the bulky nonpolar O-acetyls, which protrude in rows on both sides, make up most of the surface. The carboxyls are less exposed and are partially shielded by the O-acetyls. The molecular model thus provides an explantation for the dominant role of the O-acetyls, as well as the lesser effect of carboxyl reduction, upon the immunologic properties of Vi.

Role of phosphorylation in conformational adaptability of bovine myelin basic protein

Controlled thrombic digestion of a preparation of components 2 + 3 isolated from the 18.5 kDa bovine myelin basic protein (MBP) yielded a polypeptide that was monophosphorylated on threonine 97 (component 3pT97). This is the first posttranslationally phosphorylated MBP isolated in pure form. We studied the effect of this single phosphate on the conformational adaptability of 18.5 kDa bovine MBP by comparing the circular dichroism (CD) spectrum of component 3pT97 with the spectra of highly purified nonphosphorylated components 1 and 2. The CD spectra of nonphosphorylated component 1 and component 2 [monodeamidated form(s) of component 1] were indistinguishable, while component 3pt97 exhibited a different spectrum. The singly phosphorylated MBP component exhibited 13% more ordered conformations than that adopted by nonphosphorylated MBP in dilute aqueous solutions. This was estimated from the CD spectra, and apparently involved about 17 additional amino acid residues in beta-structure(s).

Application of optical properties of the Vi capsular polysaccharide for quantitation of the Vi antigen in vaccines for typhoid fever

The capsular polysaccharide of Salmonella typhi and of Citrobacter freundii (Vi) is a linear homopolymer of alpha 1,4-linked N-acetylgalactosaminuronic acid, variably O-acetylated at the C-3 position. Vaccines composed of Vi confer protection against typhoid fever with an efficacy of about 70%; Vi has recently been conjugated to proteins to increase its immunogenicity and effectiveness (I.L. Acharya, R. Tapa, V.L. Gurubacharya, M.B. Shrestha, C.U. Lowe, D.D. Bryla, R. Schneerson, J.B. Robbins, T. Crampton, B. Trollfors, M. Cadoz, D. Schulz, and J. Armand, N. Engl. J. Med. 317:1101-1104, 1987; K.P. Klugman, I. Gilbertson, H.J. Kornhof, J.B. Robbins, R. Schneerson, D. Schulz, M. Cadoz, and J. Armand, Lancet ii:1165-1169, 1987; S.C. Szu, A.L. Stone, J.D. Robbins, R. Schneerson, and J.B. Robbins, J. Exp. Med. 166:1510-1524, 1987). Vi, however, cannot be measured by conventional colorimetric methods. Two optical techniques were adapted to quantitate Vi in vaccines. The first, Fourier-transformed infrared spectroscopy, was performed on salt-free, freeze-dried samples. The intensities of the absorbance peaks of Vi were proportional to the amount of Vi within the range of 0.25 to 2.0 mg. The amount of Vi was determined from integrated absorptions at the 1,235- or 1,417-cm-1 band. The second technique, spectrophotometric titration, was more sensitive than the Fourier-transformed infrared spectroscopy and could be performed on dilute solutions. The metachromatic effect of the reaction between the aromatic cationic dye acridine orange and the carboxyl groups of Vi was quantitative within +/- 2% in the range of 20 to 700 micrograms of Vi per ml. The accuracy of the titration of Vi in the vaccines was within +/- 8%. These two methods may be applicable to measure other capsular polysaccharides in vaccines.

Vi capsular polysaccharide-protein conjugates for prevention of typhoid fever. Preparation, characterization, and immunogenicity in laboratory animals

The Vi has proven to be a protective antigen in two double masked, controlled clinical trials in areas with high rates of typhoid fever (approximately 1% per annum). In both studies the protective efficacy of the Vi was approximately 70%. Approximately 75% of subjects in these areas responded with a fourfold or greater rise of serum Vi antibodies. In contrast, the Vi elicited a fourfold or greater rise in 95-100% of young adults in France and the United States. Methods were devised, therefore, to synthesize Vi-protein conjugates in order to both enhance the antibody response and confer T-dependent properties to the Vi (and theoretically increase its protective action in populations at high risk for typhoid fever). We settled on a method that used the heterobifunctional crosslinking reagent, N-succinimidyl-3-(2-pyridyldithio)-propionate (SPDP), to bind thiol derivatives of the Vi to proteins. This synthetic scheme was reproducible, provided high yields of Vi-protein conjugates, and was applicable to several medically relevant proteins such as diphtheria and tetanus toxoids. The resultant conjugates were more immunogenic in mice and juvenile Rhesus monkeys than the Vi alone. In contrast to the T-independent properties of the Vi, conjugates of this polysaccharide with several medically relevant proteins induced booster responses in mice and in juvenile Rhesus monkeys. Clinical studies with Vi-protein conjugates are planned. This scheme is also applicable to synthesize protein conjugates with other polysaccharides that have carboxyl functions.

Low-ultraviolet circular dichroism spectroscopy of sequential peptides 1-63, 64-95, 96-128, and 129-168 derived from myelin basic protein of rabbit

Four sequential peptides (sequences 1-63, 64-95, 96-128, and 129-168) derived from rabbit myelin basic protein by thrombic cleavage were examined by low-ultraviolet circular dichroism spectroscopy in 0.5 mM tris(hydroxymethyl)aminomethane hydrochloride (pH approximately 7.2) containing 0-92% trifluoroethanol (TFE). In the absence of the alcohol, all of the peptides contained a significant amount (17-29%) of beta-structure. In the presence of relatively low concentrations (up to 30%) of TFE, all of the peptides except 96-128 adopted considerable alpha-helix (16-33%). This involved a transition from the beta-structure in peptide 1-63 and transitions from the nonordered structure in peptides 1-63, 64-95, and 129-168. Furthermore, additional alpha-helix formed in peptide 1-63 between 30% and 92% TFE at the expense of nonordered structure, whereas the alpha-helix formation above 50% TFE in peptide 129-168 resulted largely from a beta-structure----alpha-helix transition. With the exception of the 129-168 peptide, approximately 65-100% of the maximum level of beta-structure persisted throughout the entire range of TFE concentration. In the case of peptide 129-168, however, most of the beta-structure was converted to alpha-helix and nonordered structure at 75% TFE. While the present results support our previous assignments of beta-structure- and alpha-helix-forming regions to specific amino acid sequences of the basic protein, they also demonstrate that the beta-structure----alpha-helix transitions evidenced at various concentrations of TFE were influenced to a considerable degree by the length of the peptide, presumably due to the presence or absence of interactions between noncontiguous portions of the myelin basic protein polypeptide chain.

Low-ultraviolet circular dichroism spectroscopy of oligopeptides 1-95 and 96-168 derived from myelin basic protein of rabbit

Myelin basic protein (MBP) is a major protein constituent of the myelin sheath of the central nervous system, where it is believed to have functional alpha-helical segments. One element of the function of the protein might be "conformational adaptability" of specific regions of its amino acid sequence, since the purified protein appears to be largely devoid of ordered structure. To pursue this question, low-ultraviolet circular dichroism (CD) spectroscopy was conducted on the sequential thrombic peptides 1-95 and 96-168 of the protein in the presence of 0-92% trifluoroethanol (TFE), a solvent known to promote stable secondary structures in polypeptides. The series of CD spectra of the oligopeptides were subjected to a computerized best-fit analysis of four peptide conformations, the alpha-helix, beta-structure, beta-turn, and nonordered form. Agreement between experimental and best-fit composite spectra was achieved when standard CD curves of peptide conformations were derived from known theoretical spectra and experimental spectra of polypeptides. In dilute buffer alone, oligopeptides 1-95 and 96-168 evidence no alpha-helix but significant beta-structure (18% and 23%, respectively), as well as a predominant, extended nonordered conformation. However, the two parts of the protein differed in conformational adaptability. From 0% to 30% TFE, 96-168 exhibited concomitant transitions to 10% helix and 32% beta-structure from the nonordered form. In contrast, in 10-30% TFE, 1-95 underwent a transition to approximately 21% helix with partial loss of beta-structure as well as nonordered form; higher concentrations of TFE (40-75%) promoted additional transitions to both helix and beta-structure (totaling 33% and 25%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Far-ultraviolet circular dichroism and uronic acid components of anticoagulant deca-, dodeca-, tetradeca-, and octadecasaccharide heparin fractions

The therapeutic anticoagulant action of heparin is mediated by the ability of a multifunctional octadecasaccharide region of the molecule to bind to and differentially alter the conformational integrity of antithrombin, and the sugar sequence of the primary binding domain is known. Low ultraviolet circular dichroism spectroscopy of heparin-derived anticoagulant octa-, deca-, dodeca-, tetradeca-, and octadecasaccharides has been useful in elucidating the nature of the sugars that are contained within the second functional domain of the octadecasaccharide. The difference between the spectra of the molar ellipticity of the above sequential oligosaccharides was taken to be the CD spectrum of the corresponding additional disaccharide unit(s). Optical models of the component disaccharides of heparin were derived from CD spectra of heparins having a high degree of sulfation, synthetic glycosides of N-acetylglucosamine, and glycosides of component uronic acids. These were sufficiently distinct in magnitude and spectral position to warrant interpretation of the experimental difference CD spectra. The uronic acids of the disaccharides between deca- and octamer, dodeca- and decamer, and tetradeca- and dodecamer were thereby ascribed to sulfated iduronate, unsulfated iduronate, and glucuronate residues, respectively, while those of the tetrasaccharide between the octadeca- and tetradecasaccharide were tentatively assigned to sulfated iduronate moieties. Interpretation of the difference CD spectra on the basis of the optical models was less certain in regard to the amino sugar components. It appears that the amino sugar derivative between the dodeca- and decamer was N-acetylglucosamine, while the other disaccharides of the octa- to octadecasaccharide probably contained the N-sulfated derivative. A speculative disaccharide sequence drawn from these data indicates that relatively less strongly anionic disaccharides, having nonsulfated uronic acid moieties and N-acetylglucosamine, were flanked by trisulfated disaccharide units, constituting a structural element similar to that which contains the primary binding domain of the anticoagulant.

Circular dichroism spectroscopy of heparin-antithrombin interactions

We have utilized circular dichroism spectroscopy to examine the interaction of antithrombin with heparin-derived oligosaccharides and mucopolysaccharides of various sizes. Our studies demonstrate that the various complexes exhibit two major types of chiral absorption spectra. The first of these patterns is seen when octasaccharide, decasaccharide, dodecasaccharide, or tetradecasaccharide fragments bind to the protease inhibitor. The circular dichroism spectra of these complexes when compared to the spectrum of free antithrombin show several distinguishing characteristics. On the one hand, there is a marked general increase in positive chiral absorption that is maximal at 296 and 288 nm and 290 and 282.5 nm. These observations indicate perturbation of "buried" and "exposed" tryptophan residues. On the other hand, a significant augmentation in circular dichroism that peaks at 269.5 and 263 nm is noted. These findings are probably due to the summed positive and negative contributions arising from tryptophan residue(s), disulfide bridge(s), and phenylalanine residue(s). Given that these heparin fragments are able to accelerate factor Xa-antithrombin interactions but not thrombin-antithrombin interactions, the above spectral transitions must be associated with either the binding of a critical domain of the oligosaccharides to the protease inhibitor or the "activation" of the protease inhibitor with respect to factor Xa neutralization. The second of these patterns is apparent when octadecasaccharide, low molecular weight heparin (6,500), and high molecular weight heparin (22,000) interact with antithrombin. The circular dichroism spectra of these complexes compared to the spectrum of free protease inhibitor are similar to the first pattern except for changes within the 292- to 282-nm and 275- to 255-nm regions. The subtraction of the first pattern from the second pattern reveals a shallow negative band between 300 and 275 nm with potential negative minima at 290 and 283 nm as well as a deep negative band between 275 and 255 nm with possible negative minima at 268 and 262 nm. This chiral absorption profile is most likely to arise from conformational changes of a disulfide bridge(s). However, we cannot completely exclude the possibility that the above circular dichroism difference curve might be explained on the basis of transitions originating from a tryptophan residue(s). Given our method for generating the above data, these spectral alterations must be associated with the binding of a second critical domain of the mucopolysaccharide to antithrombin that is required for rapid complex formation with thrombin or the activation of the protease inhibitor with respect to the neutralization of the latter enzyme.

Studies on a molecular basis for the heparin-induced regulation of enzymatic activity of mouse striatal tyrosine hydroxylase in vitro. Inhibition of heparin activation and of the enzyme by poly-L-lysyltyrosine and poly-L-lysylphenylalanine and their constituent peptides

Tyrosine hydroxylase was purified up to 10-fold from hypotonic extracts of mouse striatum by heparin affinity chromatography. The purified enzyme (a) had a low Km for tyrosine (around 15 microM) and was not inhibited by tyrosine at concentrations up to 0.2 mM when tetrahydrobiopterin was cofactor and (b) was activated by heparin. The interaction of heparin with tyrosine hydroxylase was studied in ways relating to the known interaction with antithrombin. Heparin and keratan sulfates failed to activate tyrosine hydroxylase in place of heparin; several fractions of the bulk heparin (constituting 5 and 15%) had enriched tyrosine hydroxylase-activating potency; and two lysine copolypeptides ((polylysyltyrosine and polylysylphenylalanine) inhibited the activation of tyrosine hydroxylase by heparin. The lysine copolymers also directly inhibited the enzyme. Heparin (but not heparan and keratan sulfates) protected tyrosine hydroxylase from this inhibition. The constituent lysyltyrosyl (but not lysylphenylalanyl) peptide inhibited tyrosine hydroxylase, and heparin also reversed this inhibition, which was sigmoidal (IC50 of 490 microM) and partially competitive with tyrosine. Tyrosine hydroxylase was purified up to sevenfold by lysyltyrosyl-affinity chromatography. This enzyme preparation exhibited an eightfold greater sensitivity to lysyltyrosylamide than tyrosine hydroxylase purified by heparin affinity. The data indicate that tyrosine hydroxylase is regulated in vitro by a negatively charged site. Occupancy of this site by cationic effectors results in allosteric inhibition which mediates changes in the apparent Km for tyrosine.

Aggregation of ampholine on heparin and other acidic polysaccharides in isoelectric focusing

The mechanism of complexation of pI range 3.5--5 Ampholine to heparin in isoelectric focusing has been explored by the dye-binding technique at different pH values in solution. There is no significant interaction between heparin and Ampholine at pH 6.7. Weak, or selective, binding occurs at pH 5.1, and very strong interaction at pH 3.5. In the latter system, the Ampholine components appear to behave as polycations due to their ordered sequence of positive charges, each two methylene groups apart, which favors a strong binding to polyanions. In addition, there appear to be variable stoichiometries for the strong binding between heparin and Ampholine, depending on their relative amounts. It is proposed that at a low ratio of heparin to Ampholine (Ampholine excess), aggregation is perpendicular to the heparin chain, with the end ammonium charge of each Ampholine molecule neutralizing one negative charge along the heparin molecule; at higher ratios (heparin excess), the bound Ampholine segment is aligned parallel to the heparin molecule, so that on the average one Ampholine component neutralizes approx. three negative charges. The banding of heparin in isoelectric focusing in the pH range 3.0--4.5 can be explained by aggregation of the various components on heparin in amounts dependent upon the net charge on the Ampholine species at the given pH, and upon the changing stoichiometries as a function of the variation in ratio of heparin to Ampholine along the pH gradient. Binding of Ampholine to polygalacturonate was also demonstrated in excess Ampholine in a pH range dependent on the degree of protonation of the carboxyl groups of this acidic polysaccharide as well as on the net positive charge of the Ampholine. The aggregation seen at pH 4.2--4.5 led to the prediction and subsequent demonstration that polygalacturonate would also exhibit binding upon isoelectric focusing. This supports the hypothesis that aggregation of Ampholine on polyanions having sufficient charge density is a general phenomenon which can lead to spurious banding of certain polymers at appropriate pH ranges in isoelectric focusing. On the basis of their behavior in isoelectric focusing at pH 3.0--4.5, strength of aggregation of the polyanions studied appears to be heparin A = heparin B greather than polyglutamate greater than carboxyl-reduced heparin B greater than polygalacturonic acid.

The aggregation of basic polypeptide residues bound to heparin

The molecular basis for heparin interactions with proteins has been explored with L-lysine copolymer : heparin complexes, measuring the conformational change and charge neutralization which accompany the complexation, using optical methods. Previous studies had shown that the basic homopolypeptides (poly-L-lysine, poly-L-arginine) assume alpha-helical conformation upon interaction with numerous glycosaminoglycans (including heparin). Thus, the unique specificity for heparin in the anticoagulation system (which involves two or more lysine residues on the antithrombin molecule) is not paralleled by the findings with the basic homopolymers. Results with mixed polypeptides, poly(lysine : tyrosine, 1 : 1) and poly(lysine : phenylalanine, 1.4 : 1), show that these protein models assume different conformational forms upon complexation with heparin, the former shows a poly-L-lysine-like beta-structure circular dichroism spectrum and the latter an alpha-helical structure. The change in circular dichroism spectra increases with the addition of heparin until the ratio of positive to negative charge is about one. Dye-binding studies of the two copolymer systems reveal that the charged groups of both reactants are largely blocked in the polypeptide complexes at a calculated charge ratio equal to one. The data indicate that heparin interaction with the cationic polypeptides causes them to assume either the alpha-helical or beta-structure depending upon the nature of the neighboring uncharged amino acid and its proclivity for alpha-helix or beta-structure.

Optical Stability In Bipyridyl Compounds

not available