High molecular weight components containing N-linked oligosaccharides of Ascaris suum extract inhibit the dendritic cells activation through DC-SIGN and MR

Helminths, as well as their secretory/excretory products, induce a tolerogenic immune microenvironment. High molecular weight components (PI) from Ascaris suum extract down-modulate the immune response against ovalbumin (OVA). The PI exerts direct effect on dendritic cells (DCs) independent of TLR 2, 4 and MyD88 molecule and, thus, decreases the T lymphocytes response. Here, we studied the glycoconjugates in PI and the role of C-type lectin receptors (CLRs), DC-SIGN and MR, in the modulation of DCs activity. Our data showed the presence of glycoconjugates with high mannose- and complex-type N-linked oligosaccharide chains and phosphorylcholine residues on PI. In addition, these N-linked glycoconjugates inhibited the DCs maturation induced by LPS. The binding and internalization of PI-Alexa were decreased on DCs previously incubated with mannan, anti-DC-SIGN and/or anti-MR antibodies. In agreement with this, the incubation of DCs with mannan, anti-DC-SIGN and/or anti-MR antibodies abolished the down-modulatory effect of PI on these cells. It was also observed that the blockage of CLRs, DC-SIGN and MR on DCs reverted the inhibitory effect of PI in in vitro T cells proliferation. Therefore, our data show the involvement of DC-SIGN and MR in the recognition and consequent modulatory effect of N-glycosylated components of PI on DCs.Fil: Favoretto, Bruna C.. Governo do Estado de Sao Paulo. Secretaria da Saude. Instituto Butantan; BrasilFil: Casabuono, Adriana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Portes Junior, José A.. Governo do Estado de Sao Paulo. Secretaria da Saude. Instituto Butantan; BrasilFil: Jacysyn, Jacqueline F.. Universidade de Sao Paulo; BrasilFil: Couto, Alicia Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Faquim Mauro, Eliana L.. Governo do Estado de Sao Paulo. Secretaria da Saude. Instituto Butantan; Brasi

A glycosyltransferase with a length-controlling activity as a mechanism to regulate the size of polysaccharides

Cyclic β-1,2-glucans (CβG) are osmolyte homopolysaccharides with a cyclic β-1,2-backbone of 17–25 glucose residues present in the periplasmic space of several bacteria. Initiation, elongation, and cyclization, the three distinctive reactions required for building the cyclic structure, are catalyzed by the same protein, the CβG synthase. The initiation activity catalyzes the transference of the first glucose from UDP-glucose to a yet-unidentified amino acid residue in the same protein. Elongation proceeds by the successive addition of glucose residues from UDP-glucose to the nonreducing end of the protein-linked β-1,2-oligosaccharide intermediate. Finally, the protein-linked intermediate is cyclized, and the cyclic glucan is released from the protein. These reactions do not explain, however, the mechanism by which the number of glucose residues in the cyclic structure is controlled. We now report that control of the degree of polymerization (DP) is carried out by a β-1,2-glucan phosphorylase present at the CβG synthase C-terminal domain. This last activity catalyzes the phosphorolysis of the β-1,2-glucosidic bond at the nonreducing end of the linear protein-linked intermediate, releasing glucose 1-phosphate. The DP is thus regulated by this “length-controlling” phosphorylase activity. To our knowledge, this is the first description of a control of the DP of homopolysaccharides

Host immune responses accelerate pathogen evolution

Pathogens face a hostile and often novel environment when infecting a new host, and adaptation is likely to be an important determinant of the success in colonization and establishment. We hypothesized that resistant hosts will impose stronger selection on pathogens than susceptible hosts, which should accelerate pathogen evolution through selection biased toward effector genes. To test this hypothesis, we conducted an experimental evolution study on Xanthomonas citri subsp. citri (Xcc) in a susceptible plant species and a resistant plant species. We performed 55 rounds of repeated reinoculation of Xcc through susceptible host grapefruit (isolates G1, G2, G3) and resistant host kumquat (isolates K1, K2, K3). Consequently, only K1 and K3 isolates lost their ability to elicit a hypersensitive response (HR) in kumquat. Illumina sequencing of the parental and descendant strains P, G1, G2, G3, K1, K2 and K3 revealed that fixed mutations were biased toward type three secretion system effectors in isolates K1 and K3. Parallel evolution was observed in the K1 and K3 strains, suggesting that the mutations result from selection rather than by random drift. Our results support our hypothesis and suggest that repeated infection of resistant hosts by pathogens should be prevented to avoid selecting for adaptive pathogens

Ellagitannins and Lignan Glycosides from Balanophora japonica (Balanophoraceae)

Three new ellagitannins named balanophotannins A?C having a 1,1′-(3,3′,4,4′-tetrahydroxy)dibenzofurandicarboxyl group in their molecules and four known lignan glycosides were isolated from the extracts of fresh aboveground and underground parts of a medicinal parasitic plant Balanophora japonica (Balanophoraceae). Their structures were elucidated on the basis of spectral and chemical evidence. Chemotaxonomic significance of the known lignan glycosides in Balanophora japonica was discussed