Xiaoming Zhang

Coactivation of Syk Kinase and MyD88 Adaptor Protein Pathways by Bacteria Promotes Regulatory Properties of Neutrophils

Neutrophils are one of the first lines of defense against microbial pathogens and are rapidly recruited at the infection site upon inflammatory conditions. We show here that after bacterial stimulation, and in contrast to monocytes and macrophages, murine neutrophils contributed poorly to inflammatory responses; however, they secreted high amounts of the anti-inflammatory cytokine IL-10 in a DAP12 adaptor-Syk kinase and MyD88 adaptor-dependent manner. Cotriggering of TLR-MyD88- and C-type lectin receptor (CLR)-Syk-dependent pathways led to a quick and sustained phosphorylation of p38 MAP and Akt kinases in neutrophils. In vivo, both Gram-negative bacteria and mycobacteria induced the recruitment of neutrophils secreting IL-10. In acute mycobacterial infection, neutrophil-derived IL-10 controlled the inflammatory response of dendritic cells, monocytes and macrophages in the lung. During a chronic infection, neutrophil depletion promoted inflammation and decreased the mycobacterial burden. Therefore, neutrophils can have a previously unsuspected regulatory role during acute and chronic microbial infections.

Type I interferons protect neonates from acute inflammation through interleukin 10–producing B cells

Newborns and infants are highly susceptible to viral and bacterial infections, but the underlying mechanism remains poorly understood. We show that neonatal B cells effectively control the production of proinflammatory cytokines by both neonatal plasmacytoid and conventional dendritic cells, in an interleukin (IL) 10–dependent manner, after Toll-like receptor (TLR) 9 triggering. This antiinflammatory property of neonatal B cells may extend to other TLR agonists (Pam3CSK4, lipopolysaccharide, and R848) and viruses. In the absence of B cells or of CD5+ B cell subsets, neonatal mice developed stronger inflammatory responses and became lethally susceptible to CpG challenge after galactosamine sensitization, whereas wild-type (WT) mice were resistant. Paradoxically, interferon (IFN)-α/β enhanced the inflammatory response to CpG challenge in adult mice, whereas they helped to control neonatal acute inflammation by stimulating the secretion of IL-10 by neonatal B cells. Finally, WT neonatal B cells rescued IL-10−/− neonates from a lethal CpG challenge, whereas IFN-α/β receptor–deficient B cells did not. Our results show that type I IFNs support a negative regulatory role of neonatal B cells on TLR-mediated inflammation, with important implications for neonatal inflammation and infection.

Regulatory functions of innate-like B cells

Innate-like B cells (ILBs) are heterogeneous populations of unconventional B cells with innate sensing and responding properties. ILBs in mice are composed of B1 cells, marginal zone (MZ) B cells and other related B cells. ILBs maintain natural IgM levels at steady state, and after innate activation, they can rapidly acquire immune regulatory activities through the secretion of natural IgM and IL-10. Thus, ILBs constitute an important source of IL-10-producing regulatory B cells (Bregs), which have been shown to play critical roles in autoimmunity, inflammation and infection. The present review highlights the latest advances in the field of ILBs and focuses on their regulatory functions. Understanding the regulatory activities of ILBs and their underlying mechanisms could open new avenues in manipulating their functions in inflammatory, infectious and other relevant diseases.

CD4 T Cells with Effector Memory Phenotype and Function Develop in the Sterile Environment of the Fetus

Umbilical cord blood from healthy neonates with no known infectious exposure contains T cells with an effector memory–like phenotype. Neonatal T Cells Wise Beyond Their Years The uterine environment was traditionally thought to be sterile, and thus, healthy neonates were not predicted to have any memory T cells, because they have not been exposed to infection. However, Zhang et al. found that, contrary to all expectations, umbilical cord blood from healthy neonates does contain T cells that have all the hallmarks of memory cells. Why those cells are there and what role they serve in the fetal environment is still unknown, but these findings suggest that the fetal immune system may be more complex than had been previously suspected, which may affect future vaccine design and treatments for fetal and neonatal infections. The T cell compartment is considered to be naïve and dedicated to the development of tolerance during fetal development. We have identified and characterized a population of fetally developed CD4 T cells with an effector memory phenotype (TEM), which are present in cord blood. This population is polyclonal and has phenotypic features similar to those of conventional adult memory T cells, such as CD45RO expression. These cells express low levels of CD25 but are distinct from regulatory T cells because they lack Foxp3 expression. After T cell receptor activation, neonatal TEM cells readily produced tumor necrosis factor–α (TNF-α) and granulocyte-macrophage colony-stimulating factor (GM-CSF). We also detected interferon-γ (IFN-γ)–producing T helper 1 (TH1) cells and interleukin-4 (IL-4)/IL-13–producing TH2-like cells, but not IL-17–producing cells. We used chemokine receptor expression patterns to divide this TEM population into different subsets and identified distinct transcriptional programs using whole-genome microarray analysis. IFN-γ was found in CXCR3+ TEM cells, whereas IL-4 was found in both CXCR3+ TEM cells and CCR4+ TEM cells. CCR6+ TEM cells displayed a genetic signature that corresponded to TH17 cells but failed to produce IL-17A. However, the TH17 function of TEM cells was observed in the presence of IL-1β and IL-23. In summary, in the absence of reported pathology or any major infectious history, T cells with a memory-like phenotype develop in an environment thought to be sterile during fetal development and display a large variety of inflammatory effector functions associated with CD4 TH cells at birth.

Priming with a DNA vaccine delivered by attenuated Salmonella typhimurium and boosting with a killed vaccine confers protection of chickens against infection with the H9 subtype of avian influenza virus.

Control of the circulation of H9 low-pathogenic avian influenza virus (LPAIV) is a major concern for both animal and public health. To improve vaccine efficacy against H9 LPAIV, we have utilized a novel prime-boost vaccination strategy. Specific-pathogen free (SPF) chickens were first orally immunized with a hemagglutinin (HA) DNA vaccine delivered by attenuated Salmonella typhimurium, followed by boosting with a killed avian influenza (AI) vaccine. Chickens in this combined vaccination group were completely protected against both oropharyngeal and cloacal virus shedding after intranasal challenge with H9N2 AIV, while viruses were detected from these sites in other vaccination groups. Prior to challenge, chickens in the prime-boost group also had higher (P<0.05) serum hemagglutination inhibition (HI) titers and intestinal mucosal IgA ELISA titers against AIV, and higher lymphoproliferation stimulation indices than those from other groups. Thus, we have demonstrated the efficacy of a novel prime-boost vaccination strategy against H9N2 avian influenza virus, which could be also applied for the development of vaccines against other mucosally infectious pathogens.

Glycosidic Tn-based vaccines targeting dermal dendritic cells favor germinal center B-cell development and potent antibody response in the absence of adjuvant

In vivo targeting of C-type lectin receptors is an effective strategy for increasing antigen uptake and presentation by dendritic cells (DCs). To induce efficient immune response, glycosylated tumor-associated Tn antigens were used to target DCs through binding to macrophage galactose-type lectin (MGL). The capacity of Tn-glycosylated antigens-and the multiple antigenic glycopeptide Tn3 therapeutic candidate vaccine-to target mouse and human MGL(+) DCs are demonstrated, especially regarding dermal DCs. In mice, MGL(+) CD103(-) dermal DCs efficiently captured and processed glycosylated Tn antigen in vivo, inducing a potent major histocompatibility complex (MHC) class II-restricted T-cell response. Intradermal immunization with Tn-glycopeptides induced high levels of Th2 cytokines-even in the presence of unmethylated cytosine-phosphate-guanosine-and was associated with increased expansion of the germinal center B-cell population. Therefore, MGL acts as an efficient endocytic antigen receptor on dermal DCs in vivo, able to prime Tn-specific T- and B-cell responses. Moreover, even in the absence of adjuvant, immunization with this glycosidic Tn-based vaccine induced high levels of anti-Tn antibody responses, recognizing human tumor cells. In vivo DC-targeting strategies, based on Tn-MGL interactions, constitute a promising strategy for enhancing antigen presentation and inducing potent antibody response.

Unique aspects of the perinatal immune system

The early stages of life are associated with increased susceptibility to infection, which is in part due to an ineffective immune system. In the context of infection, the immune system must be stimulated to provide efficient protection while avoiding insufficient or excessive activation. Yet, in early life, age-dependent immune regulation at molecular and cellular levels contributes to a reduced immunological fitness in terms of pathogen clearance and response to vaccines. To enable microbial colonization to be tolerated at birth, epigenetic immune cell programming and early life-specific immune regulatory and effector mechanisms ensure that vital functions and organ development are supported and that tissue damage is avoided. Advancement in our understanding of age-related remodelling of immune networks and the consequent tuning of immune responsiveness will open up new possibilities for immune intervention and vaccine strategies that are designed specifically for early life.

Genetic Evidence of an East Asian Origin and Paleolithic Northward Migration of Y-chromosome Haplogroup N

The Y-chromosome haplogroup N-M231 (Hg N) is distributed widely in eastern and central Asia, Siberia, as well as in eastern and northern Europe. Previous studies suggested a counterclockwise prehistoric migration of Hg N from eastern Asia to eastern and northern Europe. However, the root of this Y chromosome lineage and its detailed dispersal pattern across eastern Asia are still unclear. We analyzed haplogroup profiles and phylogeographic patterns of 1,570 Hg N individuals from 20,826 males in 359 populations across Eurasia. We first genotyped 6,371 males from 169 populations in China and Cambodia, and generated data of 360 Hg N individuals, and then combined published data on 1,210 Hg N individuals from Japanese, Southeast Asian, Siberian, European and Central Asian populations. The results showed that the sub-haplogroups of Hg N have a distinct geographical distribution. The highest Y-STR diversity of the ancestral Hg N sub-haplogroups was observed in the southern part of mainland East Asia, and further phylogeographic analyses supports an origin of Hg N in southern China. Combined with previous data, we propose that the early northward dispersal of Hg N started from southern China about 21 thousand years ago (kya), expanding into northern China 12–18 kya, and reaching further north to Siberia about 12–14 kya before a population expansion and westward migration into Central Asia and eastern/northern Europe around 8.0–10.0 kya. This northward migration of Hg N likewise coincides with retreating ice sheets after the Last Glacial Maximum (22–18 kya) in mainland East Asia.

Plasmacytoid Dendritic Cells Engagement by Influenza Vaccine as a Surrogate Strategy for Driving T-Helper Type 1 Responses in Human Neonatal Settings

BACKGROUND The elicitation of T-helper type 1 (Th1) cellular immunity to eradicate intracellular pathogens is a challenging task because of the interleukin 12 (IL-12) deficit observed in early infancy. METHODS Screening cord blood responses to various pediatric vaccines and Toll-like receptor (TLR) agonists for innate responses and CD4(+) T-cell differentiation. RESULTS We identified that nonadjuvanted inactivated trivalent influenza vaccine (TIV) was able to cosignal T cells for the production of interferon γ (IFN-γ) in a neonatal setting. This process includes the mobilization of neonatal plasmacytoid dendritic cells (pDCs) as antigen-presenting cells (APCs) that efficiently engage Th1 cells in an IL-12-independent but type I IFN-dependent manner. In addition, cord blood pDCs efficiently cross-presented antigen to CD8(+) T cells. Importantly, activation by TIV mainly requires TLR7; however, R848/TLR7- and CpGB/TLR9-activated pDCs, which poorly produced IFN-α, induce neonatal Th2 responses. CONCLUSIONS TLR pathway engagement in pDCs is necessary but not sufficient for a successful neonatal Th1 outcome. We provide evidence of a mature and functional neonatal immune system at the level of APCs and T cells and propose to implement the IFN-α/IFN-γ axis in pediatric vaccination as a surrogate for the defective IL-12/IFN-γ axis.

Neonatal Plasmacytoid Dendritic Cells (pDCs) Display Subset Variation but Can Elicit Potent Anti-Viral Innate Responses

Neonates are highly susceptible to infectious diseases and defective antiviral pDC immune responses have been proposed to contribute to this phenomenon. Isolated cord blood pDCs innately responded to a variety of TLR7 and TLR9 dependent viruses, including influenza A virus (IAV), human immunodeficiency virus (HIV) or herpes-simplex virus (HSV) by efficiently producing IFN-α, TNF-α as well as chemokines. Interestingly, following activation by CpGA, but not viruses, cord pDCs tend to survive less efficiently. We found that a hallmark of pDCs in neonates is an extended CD2+pDCs compartment compared to adult pDCs without affecting the antiviral IFN-α response. Within CD2+pDCs, we identified a subpopulation expressing CD5 and responsible for IL-12p40 production, however this population is significantly decreased in cord blood compared to adult blood. Therefore, neonatal pDCs clearly display variation in phenotype and subset composition, but without major consequences for their antiviral responses.