No abstract

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-␥ ؊ 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.H5N1 influenza vaccine ͉ MF59 adjuvant ͉ prepandemic vaccination ͉ immune memory ͉ protection

Mapping of epitopes recognized by functional monoclonal antibodies (mAbs) is essential for understanding the nature of immune responses and designing improved vaccines, therapeutics, and diagnostics. In recent years, identification of B-cell epitopes targeted by neutralizing antibodies has facilitated the design of peptide-based vaccines against highly variable pathogens like HIV, respiratory syncytial virus, and Helicobacter pylori; however, none of these products has yet progressed into clinical stages. Linear epitopes identified by conventional mapping techniques only partially reflect the immunogenic properties of the epitope in its natural conformation, thus limiting the success of this approach. To investigate antigen-antibody interactions and assess the potential of the most common epitope mapping techniques, we generated a series of mAbs against factor H binding protein (fHbp), a key virulence factor and vaccine antigen of Neisseria meningitidis. The interaction of fHbp with the bactericidal mAb 12C1 was studied by various epitope mapping methods. Although a 12-residue epitope in the C terminus of fHbp was identified by both Peptide Scanning and Phage Display Library screening, other approaches, such as hydrogen/ deuterium exchange mass spectrometry (MS) and X-ray crystallography, showed that mAb 12C1 occupies an area of ∼1,000 Å 2 on fHbp, including >20 fHbp residues distributed on both N-and C-terminal domains. Collectively, these data show that linear epitope mapping techniques provide useful but incomplete descriptions of B-cell epitopes, indicating that increased efforts to fully characterize antigen-antibody interfaces are required to understand and design effective immunogens.meningococcus | structure | surface plasmon resonance | structural mass spectrometry | antigen-antibody complex

Dendritic cell (DC) populations play unique and essential roles in the detection of pathogens, but information on how different DC types work together is limited. In this study, 2 major DC populations of human blood, myeloid (mDCs) and plasmacytoid (pDCs), were cultured alone or together in the presence of pathogens or their products. We show that pDCs do not respond to whole bacteria when cultured alone, but mature in the presence of mDCs. Using purified stimuli, we dissect this cross-talk and demonstrate that mDCs and pDCs activate each other in response to specific induction of only one of the cell types. When stimuli for one or both populations are limited, they synergize to reach optimal activation. The cross-talk is limited to enhanced antigen presentation by the nonresponsive population with no detectable changes in the quantity and range of cytokines produced. We propose that each population can be a follower or leader in immune responses against pathogen infections, depending on their ability to respond to infectious agents. In addition, our results indicate that pDCs play a secondary role to induce immunity against human bacterial infections, which has implications for more efficient targeting of DC populations with improved vaccines and therapeutics. IntroductionDendritic cells (DCs) are arrayed with diverse pathogen sensors (eg, Toll-like receptors (TLR)) and reside in tissues throughout the body, rendering them uniquely poised to detect invading pathogens. 1,2 During the initiation and amplification of the immune response, DCs rally other cells of both the innate and adaptive immune systems for the elimination of infections. 3,4 In the context of different infections, DC populations are also critical in determining the quality of the response through the efficient and rapid production of discrete subsets of cytokines, chemokines, and interferons (IFNs), which selectively direct the recruitment and activation of other immune effectors. 3,4 Because DCs are key antigen-presenting cells (APCs), the instructive role of DC soluble factors shapes adaptive immunity in various ways, resulting in focused and optimized antigen-specific responses to different pathogen classes (eg, viruses vs bacteria). 5,6 There are numerous distinct DC populations that vary in their tissue distribution, cytokine/chemokine secretion, and/or their interactions with infectious agents and other cells of the host. [7][8][9][10] Of these, blood myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) represent 2 well-characterized populations that differ in their morphology, phenotype, TLR expression, and cytokine, chemokine, and type I IFN production. [10][11][12][13][14] These differences imply that mDCs and pDCs have evolved to sense distinct classes of pathogens and selectively steer subsequent innate and adaptive immunity. Even though both DC types are considered effective APCs, 11,15 the nonoverlapping distribution of TLRs and the pattern of cytokine production in human mDCs and pDCs suggest specialized and perhaps complementary functi...