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)-alpha/beta 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-alpha/beta 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.     

Stimulation of a memory B cell response does not require primed helper T cells

The use of universally immunogenic T cell epitopes, such as those identified in tetanus toxin or malaria circumsporozoite protein, could represent a major improvement in the development of synthetic vaccines. However, one limitation of this approach is the lack of T cell cross-reactivity between the vaccine and the pathogen. To determine whether the memory B cell response elicited by immunization with a synthetic peptide containing a B cell epitope linked to a T cell epitope can be restimulated by the same B cell epitope linked to different T cell epitope(s), we used a synthetic peptide which contains non-overlapping B and T cell determinants from hepatitis B surface antigen (HBsAg) of hepatitis B virus (HBV). The results of this study clearly show that primed T cells can increase the antibody response against a B cell epitope linked to the priming T cell determinant. However, the antibody response obtained was weaker than that obtained after two injections of the peptide containing both B and T cell epitopes, showing the important role played by memory B cells in secondary antibody responses. Moreover, a strong antibody response against the B cell epitope was elicited by boosting mice with the B cell epitope linked to a heterologous carrier, thus demonstrating that a strong B cell memory response can be revealed in the absence of primed T cells. These results therefore provide new important information for the design of synthetic or recombinant vaccines.     

Ontogeny and innate properties of neonatal dendritic cells

We investigated whether a developmental immaturity of the dendritic cells (DCs) compartment could contribute to the high susceptibility to infections observed in newborns. DCs are among the first cells to colonize the spleen, but the ontogeny of DC subsets follows distinct steps. At birth, plasmacytoid DCs and CD4-CD8alpha- DCs are found in the spleen, whereas CD8alpha+ and CD4+ DCs are not present. Then, the CD8alpha+ DC compartment quickly develops and reaches an adult size by day 7, whereas the CD4+ DC compartment slowly increases to become predominant by the age of 3 weeks. The production of interleukin (IL)-12p70 by DCs is particularly efficient after birth, reflecting the stronger capacity of the neonatal CD8alpha- DCs to secrete IL-12 compared with its adult counterpart. Like-wise, neonatal DCs produced type I and II interferons. In vivo, following microbial stimulation, up-regulation of major histocompatibility complexes (MHCs) and of costimulatory molecules on DCs was induced clearly showing the activation of neonatal DCs in the neonatal environment. Therefore, despite a markedly different DC subset composition in early life compared with the adult DC compartment, neonatal DCs are fully competent in their innate immune functions.     

Extending the CD4(+) T-cell epitope specificity of the Th1 immune response to an antigen using a Salmonella enterica serovar typhimurium delivery vehicle

We analyzed the CD4 T-cell immunodominance of the response to a model antigen (Ag), MalE, when delivered by an attenuated strain of Salmonella enterica serovar Typhimurium (SL3261*pMalE). Compared to purified MalE Ag administered with adjuvant, the mapping of the peptide-specific proliferative responses showed qualitative differences when we used the Salmonella vehicle. We observed the disappearance of one out of eight MalE peptides' T-cell reactivity upon SL3261*pMalE immunization, but this phenomenon was probably due to a low level of T-cell priming, since it could be overcome by further immunization. The most striking effect of SL3261*pMalE administration was the activation and stimulation of new MalE peptide-specific T-cell responses that were silent after administration of purified Ag with adjuvant. Ag presentation assays performed with MalE-specific T-cell hybridomas showed that infection of Ag-presenting cells by this intracellular attenuated bacterium did not affect the processing and presentation of the different MalE peptides by major histocompatibility complex (MHC) class II molecules and therefore did not account for immunodominance modulation. Thus, immunodominance of the T-cell response to microorganisms is governed not only by the frequency of the available T-cell repertoire or the processing steps in Ag-presenting cells that lead to MHC presentation but also by other parameters probably related to the infectious process and to the bacterial products. Our results indicate that, upon infection by a microorganism, the specificity of the T-cell response induced against its Ags can be much more effective than with purified Ags and that it cannot completely be mimicked by purified Ags administered with adjuvant.     

重组减毒细菌运送CD8+T细胞表位的效应分析

目的:分析重组减毒菌体外运送CD8 T细胞表位的效应。方法:以表达卵清蛋白(OVA)和淋巴细胞脉络丛脑膜炎病毒(LCMV)CD8 T细胞表位的重组菌13A(ptG2F)、25A(ptG2F)和SL7207(ptG2F)感染抗原提呈细胞(APC)LKb、LLd和骨髓源树突状细胞(BMDC),应用体外抗原提呈试验检测APC对重组菌运送的CD8 T细胞表位的提呈效应。结果:感染试验证实,减毒菌13A、25A和SL7207对LKb细胞或LLd细胞均具有良好的侵袭能力,BMDC对重组菌具有很好的摄取功能。抗原提呈试验结果显示,在感染的早期(2h),LKb、LLd细胞和BMDC均可提呈重组菌13A(ptG2F)或SL7207(ptG2F)运送的T细胞表位;在感染的晚期(48h),LKb细胞对OVA257-264CD8 T细胞表位的提呈效应降低,LLd细胞对LCMV118-132CD8 T细胞表位的提呈效应增强。3种APC均不能提呈25A(ptG2F)运送的T细胞表位。另外,在同样的作用条件下,BMDC对减毒菌运送的抗原表位的提呈效应要强于LKb和LLd细胞。结论:重组菌能运送CD8 T细胞表位,为基于减毒细菌的新型基因工程疫苗的分子设计提供了有益借鉴。     

Immobilized cytokines as biomaterials for manufacturing immune cell based vaccines

Manufacturing of bioactive cell culture substrates represents a major challenge for the development of cell therapy for tissue repair and immune treatment of cancers, infectious diseases, or immunodeficiencies. In this context, we evaluated the capacity of several differentiation factors, including Granulocyte Macrophage Colony Stimulating Factor (GM-CSF) and Macrophage Colony Stimulating Factor (M-CSF), to drive differentiation of primary cell cultures, once immobilized on surfaces. We show that covalently immobilized signal factors fully retain their biological properties and efficiently promote differentiation of mouse and/or human precursor cells leading to the production of dendritic cells and macrophages. For GM-CSF, we also show that the efficiency of receptor signaling is comparable using either soluble or tethered molecules. Such artificial bioactive interfaces are suitable for the development and automated production of cell-based vaccines and therapies.     

A fully synthetic immunogen carrying a carcinoma-associated carbohydrate for active specific immunotherapy

Aberrant glycosylation of mucins leads to the exposure of cryptic carbohydrate antigens at the surface of carcinoma cells, which, therefore, represent potent targets for anticancer therapeutic vaccines. To date, the development of immunogens to stimulate immune response to such saccharidic antigens is based on carbohydrate conjugation to carrier proteins. However, these traditional protein conjugates are poorly defined in chemical composition and structure. As an alternative, we synthesized a multiple antigenic O-linked glycopeptide (MAG) carrying the carbohydrate Tn antigen associated with a CD4+ T-cell epitope (MAG:Tn-PV). This fully synthetic immunogen is highly defined in composition and carries a high saccharidic epitope ratio over the entire molecule. The MAG:Tn-PV was able to induce anti-Tn IgG antibodies that recognize human tumor cell lines. A therapeutic immunization protocol performed with this fully synthetic immunogen increased the survival of tumor-bearing mice. Thus, the accurately defined and versatile MAG system represents an efficient strategy to induce carbohydrate-specific antitumor immune responses but may also be applicable to the prevention of infectious diseases, if it is based on bacterial oligosaccharides.     

Control by H-2 genes of the Th1 response induced against a foreign antigen expressed by attenuated Salmonella typhimurium.

Attenuated salmonellae represent an attractive vehicle for the delivery of heterologous protective antigens to the immune system. Here, we have investigated the influence of the genetic background of the host which regulates the growth and elimination of Salmonella cells on the cellular response induced against a foreign antigen delivered by an aroA Salmonella strain. We have tested CD4+ T-cell responses (cell proliferation and cytokine production) in various mouse strains following immunization with Salmonella typhimurium SL3261 expressing a high level of the recombinant Escherichia coli MalE protein. We were able to detect a CD4+ T-cell response against the recombinant MalE protein only in a restricted number of mouse strains, whereas all mice produced good levels of anti-MalE immunoglobulin G antibodies. The Ity gene did not play a major role in these differences in T-cell responses, since both Ity-resistant and -susceptible strains of mice were found to be unresponsive to MalE delivered by recombinant salmonellae. In contrast, when B10 congenic mice were used, a correlation was established between MalE-specific T-cell unresponsiveness and H-2 genes. The discrepancies described in this paper in the ability of various strains of mice to develop an efficient Th1 response against a recombinant antigen displayed by a live Salmonella vaccine underscore the difficulties that can be encountered in the vaccination of human populations by such a strategy.     

Induction of a polarized Th1 response by insertion of multiple copies of a viral T-cell epitope into adenylate cyclase of Bordetella pertussis

The adenylate cyclase (CyaA) of Bordetella pertussis delivers the N-terminal catalytic domain into the cytosol of a large number of eukaryotic cells, in particular, professional antigen-presenting cells. This allows the delivery of CD8(+) T-cell epitopes to the major histocompatibility complex class I presentation pathway. We have previously shown that immunization of mice with CyaA carrying a single CD8(+) T-cell epitope leads to antiviral protection as well as to protective and therapeutic antitumor immunity associated with the induction of specific cytotoxic T-lymphocyte (CTL) responses. Here, we evaluated the capacity of CyaA carrying one to four copies of the CD8(+) CD4(+) T-cell epitope from the nucleoprotein of the lymphocytic choriomeningitis virus to induce T-cell responses. Both CTL and Th1-like specific responses were detected in mice immunized with recombinant CyaA with or without adjuvant. Although the insertion of the larger peptides resulted in partial loss of the invasive capacity of recombinant CyaA, insertion of several copies of the same epitope led to a strong enhancement of Th1 responses and, to a lesser degree, CTL responses. These results underscore the potency of CyaA for vaccine design with a new impact on diseases in which the Th1 response has been described to have a beneficial effect.     

Parameters Affecting the Immunogenicity of Recombinant T Cell Epitopes Inserted into Hybrid Proteins

In the past few years a considerable number of studies have focused on the mechanisms of antigen presentation by classical major histocompatibility complex (MHC) class I and class II encoded molecules. Among different approaches, the engineering of recombinant chimeric genes and proteins has provided new tools to analyze the parameters influencing the intracellular processing of antigenic determinants. This review will summarize and discuss the different models of recombinant genes and molecules that have been used to analyze the influence of the molecular environment of a T cell determinant on its efficient processing and MHC presentation. This approach may also represent an interesting tool for developing new vaccine strategies for inducing T cell responses against pathogens.