Human Anti-Human CD300LF Antibody Fab Fragment

Murine norovirus (MNoV) is closely related to human norovirus (HNoV), an infectious agent responsible for acute gastroenteritis worldwide. Here we report the X-ray crystal structure of the dimeric MNoV VP1 protruding (P) domain in complex with its cellular receptor CD300lf. CD300lf binds the P domain with a 2: 2 stoichiometry, engaging a cleft between the AB and DE loops of the P2 subdomain at a site that overlaps the epitopes of neutralizing antibodies. We also identify that bile acids are cofactors enhancing MNoV cell-binding and infectivity. Structures of CD300lf-P domain in complex with glycoche-nodeoxycholic acid (GCDCA) and lithocholic acid (LCA) reveal two bile acid binding sites at the P domain dimer interface distant from receptor binding sites. The structural determinants for receptor and bile acid binding are supported by numerous biophysical assays utilizing interface residue mutations. We find that the monomeric affinity of CD300lf for the P domain is low and is divalent cation dependent. We have also determined the crystal structure of CD300lf in complex with phosphocholine, revealing that MNoV engages its receptor in a manner mimicking host ligands including similar metal coordination. Docking of the cocomplex structures onto a cryo-EM-derivedmodel of MNoV suggests that each virion can make multiple CD300lf engagements, and thus, infection may be driven by the avidity of cell surface clustered CD300lf. These studies identify multiple potential modulators of norovirus infection that may act to regulate the interaction between the viral capsid P domain and its cognate cellular receptor.

Background-Fibrinogen is a multifunctional circulating glycoprotein involved in wound healing, thrombosis, platelet aggregation, and inflammation, and elevated levels predict vascular disease. Despite evidence of crucial biological function and moderate heritability, comprehensive analysis of the influence of genetic variation on fibrinogen is not available. Methods and Results-To address this issue, we undertook a genome-wide association study evaluating the potential relationships between 337 343 single-nucleotide polymorphisms (SNPs) and plasma fibrinogen levels among 17 686 apparently healthy women participating in the Women's Genome Health Study. As C-reactive protein is also an inflammatory marker known to predict cardiovascular diseases, we compared the determinants of fibrinogen levels with those of C-reactive protein. Four novel loci were identified, in addition to the fibrinogen gene cluster, which were associated with fibrinogen levels at genome-wide levels of significance (range of probability values from 8.82X10(-09) to 8.04X10(-39)). Two of the loci are related to common chronic inflammatory diseases: the first, at locus 5q31.1 (SLC22A5, SLC22A4, IRF1), lies immediately adjacent to a locus linked to Crohn disease (P value for lead SNP, 1.24X10(-12)) and the second, at locus 17q25.1 (CD300LF, SLC9A3R1, NAT9), has been associated with psoriasis (P value for lead SNP, 7.72X10(-11)). A third locus at 1q21.3 (IL6R) lies within the interleukin 6 receptor gene, a critical component of the inflammatory cascade (P value for lead SNP, 1.80X10(-11)). A novel locus at 2q34 (CPSI) participates in the urea cycle (P=8.82X10(-09)). The majority of implicated SNPs showed little evidence of dual association with C-reactive protein levels. Conclusions-A genome-wide survey of the human genome identifies novel loci related to common chronic inflammatory diseases as genetic determinants of fibrinogen levels, in addition to loci that relate to the inflammatory cascade, the urea cycle, and the fibrinogen gene cluster. (Circ Cardiovasc Genet. 2009; 2: 134-141.)