Dissecting the Immune Response to MF59-adjuvanted and Nonadjuvanted Seasonal Influenza Vaccines in Children Less Than Three Years of Age.

Annual seasonal influenza epidemics are particularly dangerous for the very young, the elderly and chronically ill individuals, in whom infection can cause severe morbidity, hospitalization and death. Existing, nonadjuvanted influenza vaccines exhibit a suboptimal immunogenicity and efficacy in immunologically naive subjects such as young children.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Early rise of blood T follicular helper cell subsets and baseline immunity as predictors of persisting late functional antibody responses to vaccination in humans

CD4+ T follicular helper cells (TFH) have been identified as the T-cell subset specialized in providing help to B cells for optimal activation and production of high affinity antibody.We recently demonstrated that the expansion of peripheral blood influenza-specific CD4+IL-21+ICOS1+ T helper (TH) cells, three weeks after vaccination, associated with and predicted the rise of protective neutralizing antibodies to avian H5N1. In this study, healthy adults were vaccinated with plain seasonal trivalent inactivated influenza vaccine (TIIV), MF591-adjuvanted TIIV (ATIIV), or saline placebo. Frequencies of circulating CD4+ TFH1 ICOS+ TFH cells and H1N1-specific CD4+- IL-21+ICOS+ CXCR5+ TFH and CXCR5- TH cell subsets were determined at various time points after vaccination and were then correlated with hemagglutination inhibition (HI) titers. All three CD4+ T cell subsets expanded in response to TIIV and ATIIV, and peaked 7 days after vaccination. To demonstrate that these TFH cell subsets correlated with functional antibody titers, we defined an alternative endpoint metric, decorrelated HI (DHI), which removed any correlation between day 28/day 168 and day 0 HI titers, to control for the effect of preexisting immunity to influenza vaccine strains. The numbers of total circulating CD4+ TFH1 ICOS+ cells and of H1N1- specific CD4+IL-21+ICOS+ CXCR5+, measured at day 7, were significantly associated with day 28, and day 28 and 168 DHI titers, respectively. Altogether, our results show that CD4+ TFH subsets may represent valuable biomarkers of vaccine-induced long-term functional immunity

Human cytomegalovirus pUL10 interacts with leukocytes and impairs TCR-mediated T-cell activation

Human cytomegalovirus (HCMV) is known to exert suppressive effects on the host immune system through expression of various viral genes, thus directly and indirectly affecting antiviral immunity of the infected individuals. We report here that HCMV UL10 encodes a protein (pUL10) with immunosuppressive properties. UL10 has been classified as a member of the HCMV RL11 gene family. Although pUL10 is known to be dispensable for viral replication in cultured cells, its amino-acid sequence is well conserved among different HCMV isolates, suggesting that the protein has a crucial role in viral survival in the host environment. We show that pUL10 is cleaved from the cell surface of fibroblasts as well as epithelial cells and interacts with a cellular receptor ubiquitously expressed on the surface of human leukocytes, demonstrated by ex vivo cell-based assays and flow cytometric analyses on both lymphoid cell lines and primary blood cells. Furthermore, preincubation of peripheral blood mononuclear cells with purified pUL10 ectodomain results in significantly impaired proliferation and substantially reduced pro-inflammatory cytokine production, in particular in CD4+ T cells upon in vitro T-cell stimulation. The inhibitory effect of pUL10 is also observed on antigen receptor-mediated intracellular tyrosine phosphorylation in a T-cell line. Based on these observations, we suggest that pUL10 is a newly identified immunomodulatory protein encoded by HCMV. Further elucidation of interactions between pUL10 and the host immune system during HCMV may contribute to finding ways towards new therapies for HCMV infection

CT043, a Protective Antigen That Induces a CD4+ Th1 Response during Chlamydia trachomatis Infection in Mice and Humans▿

Despite several decades of intensive studies, no vaccines against Chlamydia trachomatis, an intracellular pathogen causing serious ocular and urogenital diseases, are available yet. Infection-induced immunity in both animal models and humans strongly supports the notion that for a vaccine to be effective a strong CD4+ Th1 immune response should be induced. In the course of our vaccine screening program based on the selection of chlamydial proteins eliciting cell-mediated immunity, we have found that CT043, a protein annotated as hypothetical, induces CD4+ Th1 cells both in chlamydia-infected mice and in human patients with diagnosed C. trachomatis genital infection. DNA priming/protein boost immunization with CT043 results in a 2.6-log inclusion-forming unit reduction in the murine lung infection model. Sequence analysis of CT043 from C. trachomatis human isolates belonging to the most representative genital serovars revealed a high degree of conservation, suggesting that this antigen could provide cross-serotype protection. Therefore, CT043 is a promising vaccine candidate against C. trachomatis infection

One dose of an MF59-adjuvanted pandemic A/H1N1 vaccine recruits pre-existing immune memory and induces the rapid rise of neutralizing antibodies

Protective antibody responses to a single dose of 2009 pandemic vaccines have been observed in the majority of healthy subjects aged more than 3 years. These findings suggest that immune memory lymphocytes primed by previous exposure to seasonal influenza antigens are recruited in the response to A/H1N1 pandemic vaccines and allow rapid seroconversion. However, a clear dissection of the immune memory components favoring a fast response to pandemic vaccination is still lacking. Here we report the results from a clinical study where antibody, CD4+ T cell, plasmablast and memory B cell responses to one dose of an MF59-adjuvanted A/H1N1 pandemic vaccine were analyzed in healthy adults. While confirming the rapid appearance of antibodies neutralizing the A/H1N1 pandemic virus, we show here that the response is dominated by IgG-switched antibodies already in the first week after vaccination. In addition, we found that vaccination induces the rapid expansion of pre-existing CD4+ T cells and IgG-memory B lymphocytes cross-reactive to seasonal and pandemic A/H1N1 antigens. These data shed light on the different components of the immune response to the 2009 H1N1 pandemic influenza vaccination and may have implications in the design of vaccination strategies against future influenza pandemics

A phase I, randomized, controlled, dose-ranging study of investigational acellular pertussis (aP) and reduced tetanus-diphtheria-acellular pertussis (TdaP) booster vaccines in adults

Despite high vaccination coverage worldwide, pertussis has re-emerged in many countries. This randomized, controlled, observer-blind phase I study and extension study in Belgium (March 2012–June 2015) assessed safety and immunogenicity of investigational acellular pertussis vaccines containing genetically detoxified pertussis toxin (PT) (NCT01529645; NCT02382913). 420 healthy adults (average age: 26.8 ± 5.5 years, 60% female) were randomized to 1 of 10 vaccine groups: 3 investigational aP vaccines (containing pertussis antigens PT, filamentous hemagglutinin [FHA] and pertactin [PRN] at different dosages), 6 investigational TdaP (additionally containing tetanus toxoid [TT] and diphtheria toxoid [DT]), and 1 TdaP comparator containing chemically inactivated PT. Antibody responses were evaluated on days 1, 8, 30, 180, 365, and approximately 3 years post-booster vaccination. Cell-mediated immune responses and PT neutralization were evaluated in a subset of participants in pre-selected groups. Local and systemic adverse events (AEs), and unsolicited AEs were collected through day 7 and 30, respectively; serious AEs and AEs leading to study withdrawal were collected through day 365 post-vaccination. Antibody responses against pertussis antigens peaked at day 30 post-vaccination and then declined but remained above baseline level at approximately 3 years post-vaccination. Responses to FHA and PRN were correlated to antigen dose. Antibody responses specific to PT, toxin neutralization activity and persistence induced by investigational formulations were similar or significantly higher than the licensed vaccine, despite lower PT doses. Of 15 serious AEs, none were considered vaccination-related; 1 led to study withdrawal (premature labor, day 364; aP4 group). This study confirmed the potential benefits of genetically detoxified PT antigen. All investigational study formulations were well tolerated

H1N1-specific CD4⁺IL-21⁺ICOS⁺CXCR5⁺ T_FH cells predict functional antibody responses.

<p>Correlations between the number of H1N1-specific CD4⁺IL-21⁺ICOS⁺CXCR5⁺ T_FH cells and H1N1-specific DHI responses measured at (A) day 28 and (B) day 168 after immunizzation. Dashed lines represent the least squares regressions fit to the data. R: Pearson product-moment correlation coefficient. <i>p</i>: correlation-associated p value.</p

H1N1-specific CD4⁺IL-21⁺ICOS⁺ T_H cells subsets expressing or not CXCR5 expand after influenza vaccination.

<p>Number of CD4⁺IL-21⁺ICOS⁺ T_H cells, showing a CXCR5⁺ (black) or CXCR5^- (gray) phenotype, in vaccinated participants after overnight stimulation with A/California/7/2009 (H1N1) antigen or SEB. Data show saline placebo (n=7), and merged TIIV (n=18) and ATIIV (n=17) cohorts at baseline (D0), day 7 (D7) and day 28 (D28) after a single dose of influenza vaccine. Data are expressed as number of cells in 10⁶ live CD4⁺ T cells; mean ± SEM is shown. Non-parametric Wilcoxon’s signed rank test was used for statistical analyses: *<i>p</i> < 0.05, **<i>p</i> < 0.01, and ***<i>p</i> < 0.001 compared to day 0.</p

Expansion of ICOS⁺ and PD-1⁺ T_FH1 cells after TIIV and ATIIV vaccination.

<p>(<b>A</b>) Number of CD4⁺ T cells expressing CXCR5 and ICOS in human PBMCs after seasonal influenza vaccination. (<b>B</b> and <b>C</b>) Number of T_FH1 cells expressing ICOS and PD-1. Data show three cohorts: saline placebo (n=7), TIIV (n=18) and ATIIV (n=17) at baseline (D0), day 7 (D7) and day 28 (D28) after a single dose of influenza vaccine. Data are shown for each participant and expressed as number of cells in 10⁶ live PBMCs acquired. Non-parametric Wilcoxon’s signed rank test was used for statistical analyses: *<i>p</i> < 0.05, **<i>p</i> < 0.01, and ***<i>p</i> < 0.001 compared to day 0; ^§<i>p</i> < 0.05, ^§§<i>p</i> < 0.01 and ^§§§<i>p</i> < 0.001 compared to saline placebo.</p