No abstract

Protection against influenza is mediated by neutralizing antibodies, and their induction at high and sustained titers is key for successful vaccination. Optimal B cells activation requires delivery of help from CD4 + T lymphocytes. In lymph nodes and tonsils, T-follicular helper cells have been identified as the T cells subset specialized in helping B lymphocytes, with interleukin-21 (IL-21) and inducible costimulatory molecule (ICOS1) playing a central role for this function. We followed the expansion of antigen-specific IL-21 + CD4 + T cells upon influenza vaccination in adults. We show that, after an overnight in vitro stimulation, influenza-specific IL-21 + CD4 + T cells can be measured in human blood, accumulate in the CXCR5 − ICOS1 + population, and increase in frequency after vaccination. The expansion of influenza-specific ICOS1 + IL-21 + CD4 + T cells associates with and predicts the rise of functionally active antibodies to avian H5N1. We also show that blood-derived CXCR5 − ICOS1 + CD4 + T cells exert helper function in vitro and support the differentiation of influenza specific B cells in an ICOS1-and IL-21-dependent manner. We propose that the expansion of antigen-specific ICOS1 + IL-21 + CD4 + T cells in blood is an early marker of vaccine immunogenicity and an important immune parameter for the evaluation of novel vaccination strategies.CD4 help | predictivity | humoral response T o confer protection, human vaccines rely on the induction of neutralizing antibodies and on the generation of a pool of memory lymphocytes able to mount an accelerated response upon encounter with the target pathogen. In recent years, novel vaccines, adjuvants, and delivery systems that are able to improve vaccine immunogenicity while reducing their reactogenicity have been developed. As vaccines are given to healthy subjects, their development is a challenging endeavor that requires extensive studies to assess safety, immunogenicity, and clinical efficacy. To accelerate the screening of novel candidates, research has focused on the identification of early biomarkers, molecular and transcriptional signatures predicting vaccine efficacy (1). Predictors should be easy to test in large clinical trials and have a clear mechanistic relationship with the correlates or surrogates of protection taken as the study endpoint. We have previously shown that an early postvaccination increase in the number of vaccine-specific CD4 + T cells is correlated in a predictive manner with the rise and long-term maintenance of protective antibody titers to avian influenza (2). The aim of the present study was to characterize the CD4 + T cells subset responsible for this function.T follicular helper (Tfh) cells have been identified in lymph nodes and tonsils as the CD4 + T cells subpopulation specialized in providing help to B cells (3-11). The recent identification of a circulating counterpart of this T cells subset in blood led us to investigate whether vaccine-specific IL-21 + CD4 + T cells are detectable in human blood, if their frequency is...

Helicobacter pylori is a gram-negative bacterium that colonizes the human gastric mucosa causing gastritis and peptic ulcer and increasing the risk of gastric cancer. The efficacy of current antibiotic-based therapies can be limited by problems of patient compliance and increasing antibiotic resistance; the vaccine approach can overcome these limits. The present study describes the therapeutic vaccination of experimentally H. pyloriinfected beagle dogs, an animal model that reproduces several aspects of the human infection with H. pylori. The vaccine consisted of three recombinant H. pylori antigens, CagA, VacA, and NAP, formulated at different doses (10, 25, or 50 g each) with alum and administered intramuscularly either weekly or monthly. No adverse effects were observed after vaccination and a good immunoglobulin G response was generated against each of the three antigens. Bacterial colonization and gastritis were decreased after the completion of the vaccination cycle, especially in the case of the monthly immunization schedule. In conclusion, therapeutic vaccination in the beagle dog model was safe and immunogenic and was able to limit H. pylori colonization and the related gastric pathology.Helicobacter pylori is a spiral-shaped, gram-negative bacterium that infects the stomach of Ͼ50% of the population worldwide, with higher prevalence in the developing countries. H. pylori induces chronic inflammation of the stomach mucosa, causing chronic gastritis and peptic ulcer (9, 33); moreover, H. pylori infection is related to gastric mucosa-associated lymphoid tissue lymphoma (4) and to an increased risk of gastric cancer (36), as also proved in animal models (13,38).Current therapies, based on one antisecretory agent plus antibiotics, although effective in 80 to 90% of cases, face problems of patient compliance, increasing antibiotic resistance, and possible recurrence or reinfection; in spite of continuous effort to improve these treatments, no major breakthroughs have been achieved in the most recent years (30).To overcome the limits of antibiotic-based therapies, the vaccine approach has been undertaken since the last decade, leading us to identify some relevant bacterial antigens as candidates for vaccines (2). On the other hand, animal models of H. pylori infection have been developed to study the interaction between the bacterium and the host, the mechanisms of immune response to either infection or vaccination, and to determine the efficacy of both prophylactic and therapeutic vaccination (2,17,26,34). Among these animal models, that of the beagle dog reproduces several aspects of the human infection with H. pylori. In fact, in the beagle dog model, intragastric administration of H. pylori results in a long-term chronic infection, characterized by gastritis, epithelial alterations, superficial erosions, and the appearance of macroscopic follicles in the gastric mucosa, mainly in the antral region of the stomach (28,29).Most of the examples of vaccination against H. pylori in animal models reported in the...

Recent data indicate that the human pathogen group B Streptococcus (GBS) produces pilus-like structures encoded in genomic islands with similar organization to pathogenicity islands. On the basis of the amino acid sequence of their protein components, 3 different types of pili have been identified in GBS, at least 1 of which is present in all isolates. We recently demonstrated that recombinant pilus proteins protect mice from lethal challenge with GBS and are thus potential vaccine candidates. Here, we show that GBS pilin island 1, transferred into the nonpathogenic microorganism Lactococcus lactis, leads to pilus assembly. We also show that systemically or mucosally delivered Lactococcus expressing pilin island 1 protects mice from challenge with GBS isolates carrying pilus 1. Furthermore, lactococci engineered to express hybrid pili containing GBS pilus 1 and pilus 2 components confer protection against strains expressing either of the 2 pilus types. These data pave the way to the design of pilus-based, multivalent live vaccines against streptococcal pathogens.

The aim of this study was to assess the role of TLR2, TLR4 and MyD88 accessory molecule in the effector and secretory response of macrophages to viable microbial agents. Using TLR-deleted macrophage cell lines generated from the bone marrow of genetically engineered mice (TLR4 gene-deficient, MyD88- and TLR2-knockout mice) and wild-type control mice, we found that TLR2-deleted macrophages exhibit increased ability to contain Candida albicans infection compared to TLR2+/+ counterpart. In contrast, both MyD88-/- and TLR4-/- macrophages retain levels of functional activity comparable to that of the respective wild-type MyD88+/+ and TLR4+/+ controls. The difference in anticandidal effector functions observed between TLR2-/- and TLR2+/+ macrophages is abrogated upon opsonization of the fungal target and interestingly is not observed when using other microbial targets, such as Streptococcus pneumoniae and Helicobacter pylori. When tested for secretory response to C. albicans, TLR2-deleted macrophages show a pattern of cytokine production similar to that of TLR2+/+ controls. Finally, flow cytometry analysis reveals that TLR2-deleted macrophages express only TLR4, while, as expected, TLR2+/+ macrophages are both TLR2 and TLR4 positive; in no cases, modulation of such markers occurs in macrophages exposed to C. albicans infection. In conclusion, these data indicate that TLR2 and TLR4 have different biological relevance, in which TLR2 but not TLR4, is involved in the accomplishment of macrophage-mediated anticandidal activity, while the secretory response to C. albicans appears to be TLR4 but not TLR2-dependent.