Induction of potent neutralizing antibody responses by a designed protein nanoparticle accine for respiratory syncytial virus

Respiratory syncytial virus (RSV) is a worldwide public health concern for which no vaccine is available. Elucidation of the prefusion structure of the RSV F glycoprotein and its identification as the main target of neutralizing antibodies have provided new opportunities for development of an effective vaccine. Here, we describe the structure-based design of a self-assembling protein nanoparticle presenting a prefusion-stabilized variant of the F glycoprotein trimer (DS-Cav1) in a repetitive array on the nanoparticle exterior. The two-component nature of the nanoparticle scaffold enabled the production of highly ordered, monodisperse immunogens that display DS-Cav1 at controllable density. In mice and nonhuman primates, the full-valency nanoparticle immunogen displaying 20 DS-Cav1 trimers induced neutralizing antibody responses ∼10-fold higher than trimeric DS-Cav1. These results motivate continued development of this promising nanoparticle RSV vaccine candidate and establish computationally designed two-component nanoparticles as a robust and customizable platform for structure-based vaccine design

Cellular and molecular mechanisms for induction of broad anti-viral B cell responses through vaccination

Viral infections contribute to significant morbidity and mortality worldwide. The immense diversity across and within viral families poses a substantial challenge for the development of prophylaxis and therapeutics. Vaccines are one of the most effective medical interventions to prevent infectious diseases. This thesis focused on characterizing anti-viral B cell responses elicited by vaccination and the mechanisms for inducing diversified responses that encompass broad reactivity. All studies were performed in the non-human primate (NHP) model to mimic the human immune system and increase the translational value of the results. In paper I, we characterized how two common routes of parenteral immunization, intramuscular (IM) and subcutaneous (SC) injections, differentially affect the early innate immune responses and the development of adaptive immune responses. The main difference observed between the SC and IM routes was the specific lymph node (LN) clusters to which the vaccine was transported. SC immunization targeted the more superficial LNs in the SC fat while the IM route targeted LNs deeper in the tissue located near major veins. The induction of vaccine-specific adaptive immune responses did not differ. In papers II and III, we performed a detailed analysis of the responses to a novel selfassembling protein nanoparticle that displayed multiple copies of the surface fusion (F) glycoprotein of human respiratory syncytial virus (HRSV). In mice, the multivalent display by the nanoparticle enhanced antibody responses compared to single copies of the HRSV-F protein. This occurred in a valency-dependent manner and relied on the assembly of the multivalent nanoparticle. Importantly, the improved responses were also observed in NHPs. In NHPs, the increased antigen display valency skewed antibody specificities, epitope-focused B cells, and led to an increase in the genetic diversity of responding B cell clonotypes. This resulted in the elicitation of pneumovirus cross-reactive antibodies. We could partly attribute this effect to increased avidity and/or B cell receptor cross-linking from repetitive arraying of antigen on the nanoparticle surface. To follow up on this phenomenon and understand the development of antibody breadth, in paper IV we characterized a pneumovirus crossneutralizing antibody lineage elicited by nanoparticle immunization. Through molecular and structural analyses of antibody variants and evolutionary intermediates, we found that this antibody had acquired cross-reactivity through affinity maturation, with critical residues located in the second heavy chain complementarity determining region (HCDR2), and that similar antibody lineages with the potential to also acquire breadth may have been elicited in multiple other animals. In conclusion, this thesis improves our understanding of the mechanisms by which vaccine formulation and delivery can modulate the quality and breadth of anti-viral B cell responses. This type of information is important for development and refinement of vaccines that are broadly protective, “universal”, within viral families

Induction of Robust B Cell Responses after Influenza mRNA Vaccination Is Accompanied by Circulating Hemagglutinin-Specific ICOS+ PD-1+ CXCR3+ T Follicular Helper Cells

Modified mRNA vaccines have developed into an effective and well-tolerated vaccine platform that offers scalable and precise antigen production. Nevertheless, the immunological events leading to strong antibody responses elicited by mRNA vaccines are largely unknown. In this study, we demonstrate that protective levels of antibodies to hemagglutinin were induced after two immunizations of modified non-replicating mRNA encoding influenza H10 encapsulated in lipid nanoparticles (LNP) in non-human primates. While both intradermal (ID) and intramuscular (IM) administration induced protective titers, ID delivery generated this response more rapidly. Circulating H10-specific memory B cells expanded after each immunization, along with a transient appearance of plasmablasts. The memory B cell pool waned over time but remained detectable throughout the 25-week study. Following prime immunization, H10-specific plasma cells were found in the bone marrow and persisted over time. Germinal centers were formed in vaccine-draining lymph nodes along with an increase in circulating H10-specific ICOS+ PD-1+ CXCR3+ T follicular helper cells, a population shown to correlate with high avidity antibody responses after seasonal influenza vaccination in humans. Collectively, this study demonstrates that mRNA/LNP vaccines potently induce an immunological repertoire associated with the generation of high magnitude and quality antibodies

Unmodified rabies mRNA vaccine elicits high cross-neutralizing antibody titers and diverse B cell memory responses

Abstract Licensed rabies virus vaccines based on whole inactivated virus are effective in humans. However, there is a lack of detailed investigations of the elicited immune response, and whether responses can be improved using novel vaccine platforms. Here we show that two doses of a lipid nanoparticle-formulated unmodified mRNA vaccine encoding the rabies virus glycoprotein (RABV-G) induces higher levels of RABV-G specific plasmablasts and T cells in blood, and plasma cells in the bone marrow compared to two doses of Rabipur in non-human primates. The mRNA vaccine also generates higher RABV-G binding and neutralizing antibody titers than Rabipur, while the degree of somatic hypermutation and clonal diversity of the response are similar for the two vaccines. The higher overall antibody titers induced by the mRNA vaccine translates into improved cross-neutralization of related lyssavirus strains, suggesting that this platform has potential for the development of a broadly protective vaccine against these viruses

Induction of Potent Neutralizing Antibody Responses by a Designed Protein Nanoparticle Vaccine for Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is a worldwide public health concern for which no vaccine is available. Elucidation of the prefusion structure of the RSV F glycoprotein and its identification as the main target of neutralizing antibodies have provided new opportunities for development of an effective vaccine. Here, we describe the structure-based design of a self-assembling protein nanoparticle presenting a prefusion-stabilized variant of the F glycoprotein trimer (DS-Cav1) in a repetitive array on the nanoparticle exterior. The two-component nature of the nanoparticle scaffold enabled the production of highly ordered, monodisperse immunogens that display DS-Cav1 at controllable density. In mice and nonhuman primates, the full-valency nanoparticle immunogen displaying 20 DS-Cav1 trimers induced neutralizing antibody responses ∼10-fold higher than trimeric DS-Cav1. These results motivate continued development of this promising nanoparticle RSV vaccine candidate and establish computationally designed two-component nanoparticles as a robust and customizable platform for structure-based vaccine design

Induction of Potent Neutralizing Antibody Responses by a Designed Protein Nanoparticle Vaccine for Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is a worldwide public health concern for which no vaccine is available. Elucidation of the prefusion structure of the RSV F glycoprotein and its identification as the main target of neutralizing antibodies have provided new opportunities for development of an effective vaccine. Here, we describe the structure-based design of a self-assembling protein nanoparticle presenting a prefusion-stabilized variant of the F glycoprotein trimer (DS-Cav1) in a repetitive array on the nanoparticle exterior. The two-component nature of the nanoparticle scaffold enabled the production of highly ordered, monodisperse immunogens that display DS-Cav1 at controllable density. In mice and nonhuman primates, the full-valency nanoparticle immunogen displaying 20 DS-Cav1 trimers induced neutralizing antibody responses ∼10-fold higher than trimeric DS-Cav1. These results motivate continued development of this promising nanoparticle RSV vaccine candidate and establish computationally designed two-component nanoparticles as a robust and customizable platform for structure-based vaccine design

Delayed generation of functional virus-specific circulating T follicular helper cells correlates with severe COVID-19

Effective humoral immune responses require well-orchestrated B and T follicular helper (Tfh) cell interactions. Whether these interactions are impaired and associated with COVID-19 disease severity is unclear. Here, longitudinal blood samples across COVID-19 disease severity are analysed. We find that during acute infection SARS-CoV-2-specific circulating Tfh (cTfh) cells expand with disease severity. SARS-CoV-2-specific cTfh cell frequencies correlate with plasmablast frequencies and SARS-CoV-2 antibody titers, avidity and neutralization. Furthermore, cTfh cells but not other memory CD4 T cells, from severe patients better induce plasmablast differentiation and antibody production compared to cTfh cells from mild patients. However, virus-specific cTfh cell development is delayed in patients that display or later develop severe disease compared to those with mild disease, which correlates with delayed induction of high-avidity neutralizing antibodies. Our study suggests that impaired generation of functional virus-specific cTfh cells delays high-quality antibody production at an early stage, potentially enabling progression to severe disease. T follicular helper cells (Tfh) enhance antibody responses and can circulate or be resident in lymph nodes. Here the authors show that during acute SARS-CoV-2 infection, circulating Tfh cells correlate with antibody titres and plasmablast levels but in more severe COVID-19 cases, cTfh generation is delayed.Funding Agencies|Swedish Research Council [2020-06100, 2020-05764, 2020-06312, 2021-03046]; Swedish Heart-Lung Foundation [20220143, 20210085, 20200034]; Bill &amp; Melinda Gates Foundation [INV-018945]; Knut and Alice Wallenberg Foundation through SciLifeLab; Karolinska Institutet; Knut and Alice Wallenberg Foundation, National Bioinformatics Infrastructure Sweden at SciLifeLab [KAW 2017.0003]</p