Monia Bardelli

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-γ− 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.

Vascular Endothelial Growth Factor-D Activates VEGFR-3 Expressed in Osteoblasts Inducing Their Differentiation

Vascular endothelial growth factor (VEGF)-D is a member of the VEGF family of angiogenic growth factors that recognizes and activates the vascular endothelial growth factor receptor (VEGFR)-2 and VEGFR-3 on blood and/or lymphatic vessels. We show that in the long bones of newborn mice, VEGF-D and VEGFR-3 are expressed in the osteoblasts of the growing plate. The treatment of primary human osteoblasts with recombinant VEGF-D induces the expression of osteocalcin and the formation of mineralized nodules in a dose-dependent manner. A monoclonal neutralizing antibody, anti-VEGF-D, or silencing of VEGFR-3 by lentiviral-mediated expression of VEGFR-3 small hairpin RNA affects VEGF-D-dependent osteocalcin expression and nodule formation. Moreover, in primary human osteoblasts, VEGF-D expression is under the control of VEGF, and inhibition of VEGF-D/VEGFR-3 signaling, by monoclonal antibodies or VEGFR-3 silencing, affects VEGF-dependent osteoblast differentiation. These experiments establish that VEGF-D/VEGFR-3 signaling plays a critical role in osteoblast maturation and suggest that VEGF-D is a downstream effector of VEGF in osteogenesis.

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.

Morphogenesis of human endothelial cells is inhibited by DAB2 via Src.

Disabled‐2 (DAB2) is an adaptor protein implicated in signal transduction pathways and in protein traffic regulation. Here, we show that DAB2 is highly expressed in human endothelial cells. DAB2 silencing in endothelial cells by lentiviral‐mediated small hairpin RNA expression affects cell migration and differentiation into capillary‐like structures while increasing cell proliferation and viability. DAB2 knockdown causes activation of the Src‐FAK signal pathway, extracellular‐signal regulated kinase and c‐Jun NH2‐terminal kinase activation, and inhibition of p38 phosphorylation. In DAB2 silenced endothelial cells, pharmacological inhibition of Src with its specific inhibitor PP2 abolishes focal adhesion kinase activation and restores differentiation of endothelial cells. These results suggest that DAB2, via Src and focal adhesion signaling, plays a role in human endothelial cell function.

VEGF-D is expressed in activated lymphoid cells and in tumors of hematopoietic and lymphoid tissues.

Vascular Endothelial Growth Factor (VEGF)-D is a member of the VEGF family of angiogenic growth factors that activate the Vascular Endothelial Growth Factor Receptor (VEGFR)-2 and VEGFR-3, which are mainly expressed in blood and lymphatic vessels. Here we have analyzed by using monoclonal antibodies, the expression of VEGF-D and its cognate receptor VEGFR-3 in normal and pathologic bone marrow and lymph node biopsies. This analysis revealed that VEGF-D is expressed in B cells of the germinal centers, scattered B and T blasts, myeloid progenitors, acute leukemia, several types of non Hodgkin lymphoma, and classical Hodgkins lymphoma. In normal tissues VEGFR-3 was only expressed in fenestrated capillaries of bone marrow and in lymphatic vessels of lymph nodes, while in VEGF-D expressing tumors newly formed vessels, but not malignant cells, showed high VEGFR-3 expression. These data suggest that VEGF-D could contribute to leukemia and lymphoma growth via the induction of angiogenesis in bone marrow and lymphoid tissues.

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

ABSTRACT 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.