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.

Human circulating influenza-CD4+ ICOS1+IL-21+ T cells expand after vaccination, exert helper function, and predict antibody responses.

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.

Approach to discover T- and B-cell antigens of intracellular pathogens applied to the design of Chlamydia trachomatis vaccines.

Natural immunity against obligate and/or facultative intracellular pathogens is usually mediated by both humoral and cellular immunity. The identification of those antigens stimulating both arms of the immune system is instrumental for vaccine discovery. Although high-throughput technologies have been applied for the discovery of antibody-inducing antigens, few examples of their application for T-cell antigens have been reported. We describe how the compilation of the immunome, here defined as the pool of immunogenic antigens inducing T- and B-cell responses in vivo, can lead to vaccine candidates against Chlamydia trachomatis. We selected 120 C. trachomatis proteins and assessed their immunogenicity using two parallel high-throughput approaches. Protein arrays were generated and screened with sera from C. trachomatis-infected patients to identify antibody-inducing antigens. Splenocytes from C. trachomatis-infected mice were stimulated with 79 proteins, and the frequency of antigen-specific CD4(+)/IFN-γ(+) T cells was analyzed by flow cytometry. We identified 21 antibody-inducing antigens, 16 CD4(+)/IFN-γ(+)-inducing antigens, and five antigens eliciting both types of responses. Assessment of their protective activity in a mouse model of Chlamydia muridarum lung infection led to the identification of seven antigens conferring partial protection when administered with LTK63/CpG adjuvant. Protection was largely the result of cellular immunity as assessed by CD4(+) T-cell depletion. The seven antigens provided robust additive protection when combined in four-antigen combinations. This study paves the way for the development of an effective anti-Chlamydia vaccine and provides a general approach for the discovery of vaccines against other intracellular pathogens.

Adjuvanted H5N1 vaccine induces early CD4+ T cell response that predicts long-term persistence of protective antibody levels.

Immune responses to vaccination are tested in clinical trials. This process usually requires years especially when immune memory and persistence are analyzed. Markers able to quickly predict the immune response would be very useful, particularly when dealing with emerging diseases that require a rapid response, such as avian influenza. To address this question we vaccinated healthy adults at days 1, 22, and 202 with plain or MF59-adjuvanted H5N1 subunit vaccines and tested both cell-mediated and antibody responses up to day 382. Only the MF59-H5N1 vaccine induced high titers of neutralizing antibodies, a large pool of memory H5N1-specific B lymphocytes, and H5-CD4(+) T cells broadly reactive with drifted H5. The CD4(+) response was dominated by IL-2(+) IFN-gamma(-) IL-13(-) T cells. Remarkably, a 3-fold increase in the frequency of virus-specific total CD4(+) T cells, measurable after 1 dose, accurately predicted the rise of neutralizing antibodies after booster immunization and their maintenance 6 months later. We suggest that CD4(+) T cell priming might be used as an early predictor of the immunogenicity of prepandemic vaccines.

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.

Efficacy, immunogenicity, and safety of a parenteral vaccine against Helicobacter pylori in healthy volunteers challenged with a Cag-positive strain: a randomised, placebo-controlled phase 1/2 study.

BACKGROUND: Intramuscular immunisation with a vaccine composed of three recombinant Helicobacter pylori antigens-vacuolating cytotoxin A (VacA), cytotoxin-associated antigen (CagA), and neutrophil-activating protein (NAP)-prevented infection in animal models and was well tolerated and highly immunogenic in healthy adults. We aimed to assess the efficacy of the vaccine in prevention of a H pylori infection after challenge with a CagA-positive strain (BCM 300) in healthy volunteers. METHODS: In this randomised phase 1/2, observer-blind, placebo-controlled, single-centre study, healthy non-pregnant adults aged 18-40 years who were confirmed negative for H pylori infection were randomly assigned (3:4) to three intramuscular doses of either placebo or vaccine at 0, 1, and 2 months. Randomisation was via a computer-generated list with study numbers ensuring the correct ratio within a block size of seven. Participants were consecutively assigned in a double-blind manner to existing study numbers of the study protocol. Investigators and participants were blinded to allocation throughout the study. One month after the third immunisation, participants underwent challenge with a CagA-positive H pylori strain, which, for safety reasons, was initially administered in a subset of participants. The primary efficacy outcome was the efficacy of the vaccine as measured by the proportion of participants infected with H pylori 12 weeks after the challenge. At the end of the study, participants infected with H pylori were treated for 14 days with combination therapy consisting of a proton pump inhibitor and two antibiotics twice daily. Safety and immunogenicity were monitored at pre-established visits. This trial is registered with ClinicalTrials.gov, number NCT00736476, and is completed. FINDINGS: 63 patients were randomly assigned, 27 to placebo and 36 to the vaccine. 34 participants (19 in the vaccinated group and 15 in the placebo group) underwent infectious challenge, all but one of whom experienced transient mild-to-moderate epigastric symptoms. 12 weeks after infectious challenge, six (32%) of 19 people in the vaccinated group and six (40%) of 15 people in the placebo group remained positive for H pylori. Eradication was successful in everyone who remained infected at 12 weeks. The geometric mean concentrations of antibodies specific to CagA (202 [95% CI 69-588] vs 4·73 [95% CI 1·41-16]; p=0·001), VacA (1469 [838-2577] vs 73 [39-138]; p=0·001), and NAP (208 [139-313] vs 8·01 [5·05-13]; p=0·001) were significantly higher in the vaccine group than in the placebo group 12 weeks after infectious challenge. INTERPRETATION: Compared with placebo, the vaccine did not confer additional protection against H pylori infection after challenge with a CagA-positive strain, despite increased systemic humoral responses to key H pylori antigens. The finding of spontaneous clearance of H pylori infection in more than half the participants in the placebo group is remarkable and suggests important immune protection in the healthy adult population. FUNDING: Novartis Vaccine and Diagnostics.

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.

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 (T(FH)) 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 (T(H)) 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), MF59(®)-adjuvanted TIIV (ATIIV), or saline placebo. Frequencies of circulating CD4(+) T(FH)1 ICOS(+) T(FH) cells and H1N1-specific CD4(+-)IL-21(+)ICOS(+) CXCR5(+) T(FH) and CXCR5(-) T(H) 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 T(FH) 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(+)T(FH)1 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(+) T(FH) subsets may represent valuable biomarkers of vaccine-induced long-term functional immunity.

Dissecting the immune response to MF59-adjuvanted and nonadjuvanted seasonal influenza vaccines in children less than three years of age.

INTRODUCTION: 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. METHODS: This phase II, randomized clinical trial was conducted to evaluate the antibody and cell-mediated responses to a trivalent influenza vaccine administered without adjuvant (TIV) or adjuvanted with MF59 (ATIV) in previously nonvaccinated children less than 3 years of age. RESULTS: The MF59-adjuvanted vaccine was well tolerated, and induced higher titers of hemagglutination inhibition antibodies able to recognize strains different from the one used in the vaccine (heterovariant) than TIV. The presence of the adjuvant MF59 induced a larger expansion of vaccine-specific CD4 T cells. Interestingly, the adjuvant MF59 did not modify the cytokine profile of the elicited T cells, characterized by the production of IL-2 and TNF-α, and did not bias the response toward either Th1 or Th2. The advantage of ATIV over TIV was more pronounced for the virus strains that had not circulated in the years that preceded this study and for the heterovariant strains. CONCLUSION: These data highlight the relevant role played by the oil-in-water adjuvant MF59 in enhancing the immunogenicity of inactivated influenza vaccines in immunologically naive individuals.

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.