[Genetic characteristics of the first human infection with the G4 genotype eurasian avian-like H1N1 swine influenza virus in Shaanxi Province,China].

Objective: To analyze the genetic characteristics of the first human infection with the G4 genotype of Eurasian avian H1N1 swine influenza virus (EA H1N1 SIV) in Shaanxi Province. Methods: The patient's throat swab samples were collected, and MDCK cells were inoculated for virus isolation to obtain the virus strain. The whole genome deep sequencing method was used to obtain the eight gene segments of the isolated strain. The nucleotide homology analysis was conducted through the Blast program in the GenBank database, and a phylogenetic tree was constructed to analyze the genetic characteristics of the virus. Results: The throat swab specimens of the case were confirmed as EA H1N1 SIV in the laboratory, and the isolated strain was named A/Shaanxi-Weicheng/1351/2022(H1N1v). Homology analysis found that the PB2, NP, HA, NA, and M genes of this isolate had the highest nucleotide homology with A/swing/Beijing/0301/2018 (H1N1), about 98.29%, 98.73%, 97.41%, 97.52%, and 99.08%, respectively. The phylogenetic tree showed that the isolate belonged to G4 genotype EA H1N1 SIV, with PB2, PB1, PA, NP and M genes from pdm/09 H1N1, HA and NA genes from EA H1N1, and NS gene from Triple-reassortant H1N1. The cleavage site of the HA protein was IPSIQSR↓G, which was the molecular characteristic of the low pathogenic influenza virus. No amino acid mutations associated with neuraminidase inhibitors were found in the NA protein. PB2 protein 701N mutation, PA protein P224S mutation, NP protein Q357K mutation, M protein P41A mutation, and NS protein 92D all indicated its enhanced adaptability to mammals. Conclusion: The patient is the first human infection with G4 genotype EA H1N1 SIV in Shaanxi province. The virus is low pathogenic, but its adaptability to mammals is enhanced. Therefore, it is necessary to strengthen the monitoring of such SIVs.

Hantavirus infection in rodents and haemorrhagic fever with renal syndrome in Shaanxi province, China, 1984-2012.

The transmission of haemorrhagic fever with renal syndrome (HFRS) is deeply influenced by the reservoir and hantavirus prevalence rate. In this study, a surveillance on human HFRS cases, relative rodent abundance, and hantavirus infection prevalence was conducted in Shaanxi province, China, during 1984-2012. A generalized linear model with Poisson-distributed residuals and a log link was used to quantify the relationship between reservoir, virus and HFRS cases. The result indicated that there was a significant association of HFRS incidence with relative rodent density and the prevalence rate. This research provides evidence that the changes of infection prevalence in the reservoir could lead directly to the emergence of a new epidemic. It was concluded that the measurement of a number of these variables could be used in disease surveillance to give useful advance warning of potential disease epidemics.

Dorsomorphin and LDN-193189 inhibit BMP-mediated Smad, p38 and Akt signalling in C2C12 cells.

Bone morphogenetic proteins (BMPs) are key regulators of cell fate decisions during embryogenesis and tissue homeostasis. BMPs signal through a coordinated assembly of two types of transmembrane serine/threonine kinase receptors to induce Smad1/5/8 plus non-Smad pathways, such as MAPK and Akt. The recent discovery of BMP receptor inhibitors opened new avenues to study specific BMP signalling and to delineate this effect from TGF-ß and Activin signalling. Here we present comprehensive and quantitative analyses on both canonical and non-Smad mediated BMP signalling under Dorsomorphin (DM) and LDN-193189 (LDN) treatment conditions. We demonstrate for the first time, that both compounds affect not only the Smad but also the non-Smad signalling pathways induced by either BMP2, BMP6 or GDF5. The activation of p38, ERK1/2 and Akt in C2C12 cells was inhibited by DM and LDN. In addition "off-target" effects on all branches of BMP non-Smad signalling are presented. From this we conclude that the inhibition of BMP receptors by DM and more efficiently by LDN-193189 affects all known BMP induced signalling cascades.

Biophysical characteristics of anti-Gal(alpha)1-3Gal IgM binding to cell surfaces: implications for xenotransplantation.

BACKGROUND: Natural antibodies directed against cell surface carbohydrates are thought to be vital to host defense and to initiate the rejection of xenografts and ABO-incompatible allografts. The biophysical properties underlying the association and dissociation of these antibodies from cell surfaces is incompletely understood. We investigated those properties for the binding of Galalpha1-3Gal antibodies to porcine endothelial cell surfaces, because such interactions might be relevant to the clinical application of xenotransplantation. RESULTS AND CONCLUSIONS: The initial rate of binding of anti-Galalpha1-3Gal antibodies to endothelial cells was found to depend on antibody concentration, antibody diffusion, and antigen concentration. The presence of an intact glycocalyx had a greater impact on antibody binding than mobility of antigen in cell membranes. Disruption of glycocalyx increased the amount of antibody bound at equilibrium by more than 50%. Although the binding of anti-Galalpha1-3Gal antibodies to cell surfaces could be inhibited by soluble Galalpha1-3Gal, once bound, some anti-Galalpha1-3Gal could not be dissociated by competitive inhibitors of binding or by denaturation of the bound Ig with chaotropic reagents, but could be dissociated by reduction of disulfide bonds, suggesting that attachment to cell surfaces was, at least in part, by means other than specific reaction with the epitope.

Hapten-induced primary and memory humoral responses are inhibited by the infusion of anti-CD20 monoclonal antibody (IDEC-C2B8, Rituximab).

Blocking the elicited humoral immune response has proven useful in treating individuals with autoimmune disorders or those who are at risk of developing antibodies which might be pathologic, e.g., transplant patients. Unfortunately, humoral immunity has evaded efforts at ablation and those therapies aimed at ameliorating it have resulted in only partial success. In addition, some of the current anti-humoral therapies not only target B-cells but also cross-react with other elements of immune response, making these therapies nonspecific. Thus there is a need in the clinical arena for specific anti-humoral therapies. Here we report the impact of infusion of a chimeric monoclonal, an anti-CD20 IgG, on the primary humoral and memory response against a simple hapten (DNP) in a nonhuman primate model. Anti-CD20 IgG interfered with the elicited humoral response and with the memory response when administered prior to antigen exposure. Furthermore, we provide evidence that anti-CD20 blocks the humoral response by eliminating those B-cells capable of responding to the hapten.

Naturally occurring anti-alpha-galactosyl antibodies: relationship to xenoreactive anti-alpha-galactosyl antibodies.

Antibodies produced by an individual without a known history of sensitization to the relevant antigen are called "natural" antibodies. Some natural antibodies, called xenoreactive antibodies, react with the cells of foreign species. Most xenoreactive antibodies in humans and higher primates bind to a nonreducing terminal galactose expressed by pigs and other lower mammals. Although human natural antibodies which bind to one or more of a variety of terminal alpha-galactosyl structures have been identified previously, the antigen recognized by anti-alpha-galactosyl antibodies on the cells of foreign species is thought to be exclusively Galalpha1-3Gal. Thus, anti-alpha-galactosyl antibodies which do not react with Galalpha1-3Gal are thought to be nonxenoreactive. Here, we identify natural antibodies in human serum which bind to Galalpha1-6Hexosepyrranosides but not Galalpha1-3Gal, indicating that these antibodies are not xenoreactive. Various lower mammals were found to have natural anti-Galalpha1-2Gal antibodies in their sera, suggesting that at least some anti-Galalpha1-2Gal antibodies might not be xenoreactive and indicating, surprisingly, that anti-alpha-galactosyl antibodies are much more phylogenetically disperse than previously known. Also surprising was the finding that some natural antibodies which bind to Galalpha1-3Gal in vitro do not bind to porcine xenografts. These studies show that naturally occurring anti-alpha-galactosyl antibodies in mammalian serum include antibodies with a greater variety of reactivities than previously thought, only some of which would bind to a porcine xenograft. Further, these studies show that the methods used to detect anti-alpha-galactosyl antibodies of relevance in xenotransplantation must be carefully evaluated to avoid detection of anti-alpha-galactosyl antibodies which would not bind to a porcine organ and which therefore are not involved in xenograft rejection.

Immunochemical properties of anti-Gal alpha 1-3Gal antibodies after sensitization with xenogeneic tissues.

In antigen-driven immune responses to proteins, antibodies of low avidity and limited complement fixing capacity undergo affinity maturation to yield antibodies of higher avidity which fix complement to a greater extent. The products of antigen-driven responses to carbohydrates are less defined. To investigate the evolution of natural antibodies against carbohydrates following sensitization, we studied natural antibodies specific for Gal alpha 1-3Gal in patients sensitized to that antigen as a result of perfusion of their blood through porcine livers for the treatment of hepatic failure. The natural antibodies against Gal alpha 1-3Gal, which occur in all unsensitized individuals, were predominantly IgM and IgG2, with average functional avidities of 5 x 10(-9) and 2 x 10(-8) M, respectively. After sensitization, the classes of anti-Gal alpha 1-3Gal included IgM, IgG2, and IgG1, and the average functional avidities of IgM and IgG were 3 x 10(-9) and 2 x 10(-9) M, respectively. The activation of complement by anti-Gal alpha 1-3Gal per microgram of Ab, measured by the fixation of C3bi on porcine cells, increased after sensitization owing to changes in subclass and avidity. Deposition of C3bi correlated with the concentrations of IgG1 and IgM but not IgG2 against Gal alpha 1-3Gal. Consistent with this finding, purified IgG1, but not IgG2, anti-Gal alpha 1-3Gal fixed complement on porcine cells. These results demonstrate that the properties of anticarbohydrate antibodies evolve after sensitization to increase complement fixation on potential targets. These properties may result from the altered costimulation of the humoral response to Gal alpha 1-3Gal due to sensitization.

Specificity and function of "natural" antibodies in immunodeficient subjects: clues to B cell lineage and development.

The origin of natural antibodies has long been a subject of controversy. Polyreactive natural antibodies recognize multiple ligands and are thought to arise from B1 B cells. Natural antibodies against carbohydrate antigens such as Gal alpha 1-3Gal or against blood groups A and B are thought to be "elicited" by gut bacteria, but their origin is uncertain. To explore the origin of naturally occurring anticarbohydrate antibodies, the specificity and function of the xenoreactive antibodies and isohemagglutinins were investigated in immunodeficient subjects. Subjects with defects in T cell-dependent antibody synthesis had normal levels of xenoreactive natural antibodies, most of which, like xenoreactive antibodies from normal individuals, were specific for Gal alpha 1-3Gal. On the other hand, some subjects with hyper-IgM syndrome who were able to synthesize abundant quantities of xenoreactive antibodies and polyreactive antibodies were devoid of anti-Gal alpha 1-3Gal antibodies. These results suggest that the lineages of B cells giving rise to anti-Gal alpha 1-3Gal antibodies and isohemagglutinins are distinct from B1 B cells or at least exist at a more "advanced" stage of development than those B1 B cells that give rise to polyreactive antibodies. The findings also suggest that B cells which synthesize anti-Gal alpha 1-3Gal antibodies and isohemagglutinins may be distinct from B2 B cells or exist at a more "primitive" stage of development than B2 B cells that synthesize elicited antibodies in normal individuals.

Modulation of natural IgM binding and complement activation by natural IgG antibodies: a role for IgG anti-Gal alpha1-3Gal antibodies.

The most abundant natural IgG Abs in human serum are thought to be Abs specific for Gal alpha1-3Gal, a carbohydrate expressed in lower mammals. IgG Abs specific for Gal alpha1-3Gal have been postulated to contribute to host defense and to participate in the rejection of interspecies organ grafts. Our previous studies indicated, however, that IgM and not IgG anti-Gal alpha1-3Gal Abs activate complement on foreign surfaces, and thus the physiologic role of IgG anti-Gal alpha1-3Gal remains uncertain. We tested whether the IgG anti-Gal alpha1-3Gal in a human serum might in fact compete with IgM for binding and thus modulate complement fixation by IgM. Several lines of evidence suggested such competition might occur. First, the functional avidity of IgG and IgM for Gal alpha1-3Gal on cell surfaces were nearly within the same order of magnitude, and in some sera the molar concentrations of IgG and IgM anti-Gal alpha1-3Gal were comparable. Second, binding of human IgM to Gal alpha1-3Gal on cell surfaces was inversely correlated with the concentration of IgG anti-Gal alpha1-3Gal in serum. Third, combination of IgG and IgM Abs specific for Gal alpha1-3Gal demonstrated direct competition for binding. The presence of IgG anti-Gal alpha1-3Gal, which was predominantly IgG2, attenuated by up to 80% the fixation of C1q mediated by IgM, presumably by competing for antigenic sites recognized by IgM Abs that fix complement. Thus, IgG Abs specific for Gal alpha1-3Gal modulate complement activation by IgM specific for that structure and might in this way modulate the consequences that ensue when human blood is brought into contact with foreign organisms or xenogenic cells.