Recent outbreaks of infectious syphilis, United Kingdom, January 2012 to April 2014

Six outbreaks of infectious syphilis in the United Kingdom, ongoing since 2012, have been investigated among men who have sex with men (MSM) and heterosexual men and women aged under 25 years. Interventions included case finding and raising awareness among healthcare professionals and the public. Targeting at-risk populations was complicated as many sexual encounters involved anonymous partners. Outbreaks among MSM were influenced by the use of geospatial real-time networking applications that allow users to locate other MSM within close proximity.

HLA class I (A, B, C) and class II (DRB1, DQA1, DQB1, DPB1) alleles and haplotypes in the Han from southern China

In this study, polymerase chain reaction-sequence-specific oligonucleotide prode (SSOP) typing results for the human leukocyte antigen (HLA) class I (A, B, and C) and class II (DRB1, DQA1, DQB1, and DPB1) loci in 264 individuals of the Han ethnic group from the Canton region of southern China are presented. The data are examined at the allele, genotype, and haplotype level. Common alleles at each of the loci are in keeping with those observed in similar populations, while the high-resolution typing methods used give additional details about allele frequency distributions not shown in previous studies. Twenty distinct alleles are seen at HLA-A in this population. The locus is dominated by the A*1101 allele, which is found here at a frequency of 0.266. The next three most common alleles, A*2402, A*3303, and A*0203, are each seen at frequencies of greater than 10%, and together, these four alleles account for roughly two-thirds of the total for HLA-A in this population. Fifty alleles are observed for HLA-B, 21 of which are singleton copies. The most common HLA-B alleles are B*4001 (f= 0.144), B*4601 (f= 0.119), B*5801 (f= 0.089), B*1301 (f= 0.068), B*1502 (f= 0.073), and B*3802 (f= 0.070). At the HLA-C locus, there are a total of 20 alleles. Four alleles (Cw*0702, Cw*0102, Cw*0801, and Cw*0304) are found at frequencies of greater than 10%, and together, these alleles comprise over 60% of the total. Overall, the class II loci are somewhat less diverse than class I. Twenty-eight distinct alleles are seen at DRB1, and the most common three, DRB1*0901, *1202, and *1501, are each seen at frequencies of greater than 10%. The DR4 lineage also shows extensive expansion in this population, with seven subtypes, representing one quarter of the diversity at this locus. Eight alleles are observed at DQA1; DQA1*0301 and 0102 are the most common alleles, with frequencies over 20%. The DQB1 locus is dominated by four alleles of the 03 lineage, which make up nearly half of the total. The two most common DQB1 alleles in this population are DQB1*0301 (f= 0.242) and DQB1*0303 (f= 0.15). Eighteen alleles are observed at DPB1; DPB1*0501 is the most common allele, with a frequency of 37%. The class I allele frequency distributions, expressed in terms of Watterson's (homozygosity) F-statistic, are all within expectations under neutrality, while there is evidence for balancing selection at DRB1, DQA1, and DQB1. Departures from Hardy-Weinberg expectations are observed for HLA-C and DRB1 in this population. Strong individual haplotypic associations are seen for all pairs of loci, and many of these occur at frequencies greater than 5%. In the class I region, several examples of HLA-B and -C loci in complete or near complete linkage disequilibrium (LD) are present, and the two most common, B*4601-Cw*0102 and B*5801-Cw*0302 account for more than 20% of the B-C haplotypes. Similarly, at class II, nearly all of the most common DR-DQ haplotypes are in nearly complete LD. The most common DRB1-DQB1 haplotypes are DRB1*0901-DQB1*0303 (f= 0.144) and DRB1*1202-DQB1*0301 (f= 0.131). The most common four locus class I and class II combined haplotypes are A*3303-B*5801-DRB1*0301-DPB1*0401 (f= 0.028) and A*0207-B*4601-DRB1*0901-DPB1*0501 (f= 0.026). The presentation of complete DNA typing for the class I loci and haplotype analysis in a large sample such as this can provide insights into the population history of the region and give useful data for HLA matching in transplantation and disease association studies in the Chinese population.

Myelin-associated glycoprotein interacts with ganglioside GT1b. A mechanism for neurite outgrowth inhibition

Myelin-associated glycoprotein (MAG) is expressed on myelinating glia and inhibits neurite outgrowth from post-natal neurons. MAG has a sialic acid binding site in its N-terminal domain and binds to specific sialylated glycans and gangliosides present on the surface of neurons, but the significance of these interactions in the effect of MAG on neurite outgrowth is unclear. Here we present evidence to suggest that recognition of sialylated glycans is essential for inhibition of neurite outgrowth by MAG. Arginine 118 on MAG is known to make a key contact with sialic acid. We show that mutation of this residue reduces the potency of MAG inhibitory activity but that residual activity is also a result of carbohydrate recognition. We then go on to investigate gangliosides GT1b and GD1a as candidate MAG receptors. We show that MAG specifically binds both gangliosides and that both are expressed on the surface of MAG-responsive neurons. Furthermore, antibody cross-linking of cell surface GT1b, but not GD1a, mimics the effect of MAG, in that neurite outgrowth is inhibited through activation of Rho kinase. These data strongly suggest that interaction with GT1b on the neuronal cell surface is a potential mechanism for inhibition of neurite outgrowth by MAG.

Detection of microchimerism by PCR is a function of amplification strategy

BACKGROUND

Suitable detection methods are needed to support larger studies of microchimerism and the allogeneic exposures that may be etiologically related to it.

STUDY DESIGN AND METHODS

A twotier PCR strategy for microchimerism detection was developed on the basis of the observation that assay sensitivity for the detection of microchimerism depends on the specificity with which primer pairs recognize sequences unique to the minor population. First, specimens are tested to determine the host HLA class II genotype by using a locus-specific PCR strategy with low sensitivity for microchimerism. Then, a sequence-specific PCR analysis having high sensitivity for detection of microchimerism is applied to detect and quantitate the minor population. Locus-specific, group-specific, and sequence-specific amplification strategies for the detection of distinct minor WBC populations prepared ex vivo were compared. In addition, 39 clinical samples from patients with known transfusion-associated microchimerism and 20 umbilical cord blood (CB) specimens containing maternal WBCs were studied.

RESULTS

Locus-specific amplification detected 17 (94%) of 18 cases in which microchimerism was present at 10 percent, but only 1 of 51 cases with microchimerism < or = 1 percent. Group-specific amplification detected all 63 cases with minor populations present at > or = 0.10 percent, but only 16 of 21 cases at the 0.01 percent level. Sequence-specific amplification detected 100 percent of cases down to the 0.01 percent level. When applied to clinical samples, locus-specific amplification reliably identified the major population but proved insensitive to low-level minor populations.

CONCLUSIONS

For the detection of microchimerism, assay sensitivity is a function of amplification strategy. These results suggest a simple approach to population screening for microchimerism: the background population of WBCs is typed by a locus-specific method, while minor population(s) can then be sought by using one or several sequence-specific amplifications.

Topological constraint on scroll wave pinning

Scroll waves in an excitable medium rotate about tubelike filaments, whose ends, when they exist, can lie on the external boundary of the medium or be pinned to an inclusion. We derive a topological rule that governs such pinning. It implies that some configurations cannot occur although they might otherwise have been expected. Heart tissue provides an application of these concepts. Computational illustrations based on a FitzHugh-Nagumo model are given.

HLA class II haplotype associations with inflammatory bowel disease in Jewish (Ashkenazi) and non-Jewish caucasian populations

Ulcerative colitis (UC) and Crohn's disease (CD) are the clinical entities comprising idiopathic inflammatory bowel disease (IBD). Previous studies on the association of IBD and human leukocyte antigen (HLA) class II genes suggested a role for HLA in this disease. Here we present HLA class II (DRB1, DQB1, DQA1, DPB1) allele and haplotype distributions determined using the polymerase chain reaction and sequence-specific oligonucleotide probe methods. A total of 578 UC and CD Caucasian patients and controls from Jewish (Ashkenazi) and non-Jewish populations was examined. Our previously reported association of DR1-DQ5 with CD was attributable to DRB1*0103. A dramatic association with IBD and the highly unusual DRB1*0103-DQA1*0501-DQB1*0301 haplotype (OR = 6.6, p = 0.036) was found. The more common DR1 haplotype, DRB1*0103-DQA1*0101-DQB1*0501, was also associated with IBD (OR = 3.1, p = 0.014), a result suggesting that interaction between DR and DQ may determine the extent of disease risk. Our previously reported association of DR2 with UC was attributable to DRB1*1502 (OR = 2.6, p = 0.006). At the DPB1 locus, a significant association of DPB1*0401 with CD was observed for the combined populations (OR = 1.85, p = 0.007). These observations indicate that some class II alleles and haplotypes confer susceptibility to both UC and CD, implying common immunogenetic mechanisms of pathogenesis, while others confer risk to only one of these diseases, and illustrate the value of DNA HLA typing in disease susceptibility analyses.

Molecular analysis of sialoside binding to sialoadhesin by NMR and site-directed mutagenesis

The molecular interactions between sialoadhesin and sialylated ligands have been investigated by using proton NMR. Addition of ligands to the 12 kDa N-terminal immunoglobulin-like domain of sialoadhesin result in resonance shifts in the protein spectrum that have been used to determine the affinities of sialoadhesin for several sialosides. The results indicate that alpha2, 3-sialyl-lactose and alpha2,6-sialyl-lactose bind respectively 2- and 1.5-fold more strongly than does alpha-methyl-N-acetylneuraminic acid (alpha-Me-NeuAc). The resonances corresponding to the methyl protons within the N-acetyl moiety of sialic acid undergo upfield shifting and broadening during titrations, reflecting an interaction of this group with Trp2 in sialoadhesin as observed in co-crystals of the terminal domain with bound ligand. This resonance shift was used to measure the affinities of mutant and wild-type forms of sialoadhesin in which the first three domains are fused to the Fc region of human IgG1. Substitution of Arg97 by alanine completely abrogated measurable interaction with alpha-Me-NeuAc, whereas a conservative substitution with lysine resulted in a 10-fold decrease in affinity. These results provide the first direct measurement of the affinity of sialoadhesin for sialosides and confirm the critical importance of the conserved arginine in interactions between sialosides and members of the siglec family of sialic acid-binding, immunoglobulin-like lectins.

A unified theory of carcinogenesis based on order-disorder transitions in DNA structure as studied in the human ovary and breast

Fourier transform-infrared/statistics models demonstrate that the malignant transformation of morphologically normal human ovarian and breast tissues involves the creation of a high degree of structural modification (disorder) in DNA, before restoration of order in distant metastases. Order-disorder transitions were revealed by methods including principal components analysis of infrared spectra in which DNA samples were represented by points in two-dimensional space. Differences between the geometric sizes of clusters of points and between their locations revealed the magnitude of the order-disorder transitions. Infrared spectra provided evidence for the types of structural changes involved. Normal ovarian DNAs formed a tight cluster comparable to that of normal human blood leukocytes. The DNAs of ovarian primary carcinomas, including those that had given rise to metastases, had a high degree of disorder, whereas the DNAs of distant metastases from ovarian carcinomas were relatively ordered. However, the spectra of the metastases were more diverse than those of normal ovarian DNAs in regions assigned to base vibrations, implying increased genetic changes. DNAs of normal female breasts were substantially disordered (e.g., compared with the human blood leukocytes) as were those of the primary carcinomas, whether or not they had metastasized. The DNAs of distant breast cancer metastases were relatively ordered. These findings evoke a unified theory of carcinogenesis in which the creation of disorder in the DNA structure is an obligatory process followed by the selection of ordered, mutated DNA forms that ultimately give rise to metastases.

Crystal structure of the N-terminal domain of sialoadhesin in complex with 3' sialyllactose at 1.85 A resolution

The structure of the functional N-terminal domain from the extracellular region of the cell surface receptor sialoadhesin has been determined in complex with the oligosaccharide 3' sialyllactose. This provides structural information for the siglec family of proteins. The structure conforms to the V-set immunoglobulin-like fold but contains several distinctive features, including an intra-beta sheet disulphide and a splitting of the standard beta strand G into two shorter strands. These novel features appear important in adapting the V-set fold for sialic acid-mediated recognition. Analysis of the complex with 3'sialyllactose highlights three residues, conserved throughout the siglec family, as key features of the sialic acid-binding template. The complex is representative of the functional recognition interaction with carbohydrate and as such provides detailed information for a heterotypic cell adhesion interaction.

Control of spatial orientation and lifetime of scroll rings in excitable media

Excitable media, which range from autocatalytic chemical systems to biological cells and tissues, can maintain organized structures in the form of rotating spiral waves of excitation. The dynamics of spiral waves in two-dimensional systems have been shown to be susceptible to control by external fields (such as electric, thermal and optical). In three dimensions, the analogues of spiral waves are scroll waves. Here we show that an external field--a temperature gradient--can be used to control a particular class of scroll waves called scroll rings. The gradient allows scroll rings to be precisely oriented in space, and their spontaneous shrinkage to be accelerated, decelerated or even reversed (so that the ring expands). The temperature gradient also influences the lifetimes of the scroll rings. We suggest that these dynamics are likely to be generic to other types of field gradients and other excitable media.

Localization of the putative sialic acid-binding site on the immunoglobulin superfamily cell-surface molecule CD22

B-lymphocyte antigen CD22 is a member of the recently described sialoadhesin family of immunoglobulin-like cell-surface glycoproteins that bind glycoconjugates terminating in sialic acid. One prominent ligand for CD22 is the highly glycosylated leukocyte surface protein CD45. Using surface plasmon resonance spectroscopy, we characterized the interaction of recombinant mouse CD22 with native CD45 purified from rat thymus (CD45-thy). By in situ desialylation and resialylation of immobilized CD45-thy, we show that mouse CD22 binds to the sialoglycoconjugate NeuGc alpha 2-6Gal beta 1-4GlcNAc carried on CD45-thy N-glycans. Previous studies have shown that the sialic acid-binding site lies within the two membrane-distal domains of CD22 (domains 1 and 2), which are V-set and C2-set immunoglobulin superfamily domains, respectively. To further localize the binding site, we have made 42 single amino acid substitutions throughout both domains. All 12 mutations that abrogated binding to CD45-thy without disrupting antibody binding were of residues within the GFCC'C" beta-sheet of domain 1. These residues are predicted to form a contiguous binding site centered around an arginine residue in the F strand that is conserved in all members of the sialoadhesin family. Our results provide further evidence that immunoglobulin superfamily cell adhesion molecules use the GFCC'C" beta-sheet of membrane-distal V-set domains to bind structurally diverse ligands, suggesting that this surface is favored for cell-cell recognition.

Characterization of the sialic acid-binding site in sialoadhesin by site-directed mutagenesis

The sialoadhesins are a distinct subgroup of the immunoglobulin superfamily, comprising sialoadhesin, CD22, the myelin-associated glycoprotein, and CD33. They can all mediate sialic acid-dependent binding to cells with distinct specificities. Sialoadhesin is a murine macrophage-restricted cell-surface molecule with 17 extracellular immunoglobulin-like domains that recognizes NeuAc alpha 2-3Gal in N- and O-glycans and interacts preferentially with cells of the granulocytic lineage. Its sialic acid-binding site is located within the NH2-terminal (membrane-distal) V-set domain. Here we have carried out site-directed mutagenesis in an attempt to identify the binding site of sialoadhesin. A subset of nonconservative mutations disrupted sialic acid-dependent binding without affecting binding of three monoclonal antibodies directed to two distinct epitopes of sialoadhesin. A CD8 alpha-based molecular model predicts that these residues form a contiguous binding site on the GFCC'C" beta-sheet of the V-set domain centered around an arginine in the F strand. A conservative mutation of this arginine to lysine also abolished binding. This amino acid is conserved among all members of the sialoadhesin family and is therefore likely to be a key residue in mediating sialic acid-dependent binding of sialoadhesins to cells.