Meeting Report: Controlled Human Influenza Virus Infection Model Studies: Current Status and Future Directions for Innovation.

On November 13-14, 2023, the National Institute of Allergy and Infectious Diseases (NIAID) in partnership with the Task Force for Global Health, Flu Lab, the Canadian Institutes of Health Research, and the Centers for Disease Control and Prevention convened a meeting on controlled human influenza virus infection model (CHIVIM) studies to review the current research landscape of CHIVIM studies and to generate actionable next steps. Presentations and panel discussions highlighted CHIVIM use cases, regulatory and ethical considerations, innovations, networks and standardization, and the utility of using CHIVIM in vaccine development. This report summarizes the presentations, discussions, key takeaways, and future directions for innovations in CHIVIMs.

Rodent Inferior Vena Cava Venoplasty Balloon Model.

Balloon venoplasty is a commonly used clinical technique to treat deep vein stenosis and occlusion as a consequence of trauma, congenital anatomic abnormalities, acute deep vein thrombosis (DVT), or stenting. Chronic deep venous obstruction is histopathologically characterized by thrombosis, fibrosis, or both. Currently, no direct treatment is available to target these pathological processes.

Regulatory workshop on challenge strain development and GMP manufacture - A stakeholder meeting report.

Within the Innovative Health Initiative (IHI) Inno4Vac CHIMICHURRI project, a regulatory workshop was organised on the development and manufacture of challenge agent strains for Controlled Human Infection Model (CHIM) studies. Developers are often uncertain about which GMP requirements or regulatory guidelines apply but should be guided by the 2022 technical white paper "Considerations on the Principles of Development and Manufacturing Qualities of Challenge Agents for Use in Human Infection Models" (published by hVIVO, Wellcome Trust, HIC-Vac consortium members). Where those recommendations cannot be met, regulators advise following the "Principles of GMP" until definitive guidelines are available.

The oxylipin analog CS585 prevents platelet activation and thrombosis through activation of the prostacyclin receptor.

Cardiovascular disease remains the primary cause of morbidity and mortality globally. Platelet activation is critical for maintaining hemostasis and preventing the leakage of blood cells from the vessel. There has been a paucity in the development of new drugs to target platelet reactivity.

Smart thrombosis inhibitors without bleeding side effects via charge tunable ligand design.

Current treatments to prevent thrombosis, namely anticoagulants and platelets antagonists, remain complicated by the persistent risk of bleeding. Improved therapeutic strategies that diminish this risk would have a huge clinical impact. Antithrombotic agents that neutralize and inhibit polyphosphate (polyP) can be a powerful approach towards such a goal.

Experimental venous thrombus resolution is driven by IL-6 mediated monocyte actions.

Deep venous thrombosis and residual thrombus burden correlates with circulating IL-6 levels in humans. To investigate the cellular source and role of IL-6 in thrombus resolution, Wild type C57BL/6J (WT), and IL-6 mice underwent induction of VT via inferior vena cava (IVC) stenosis or stasis. Vein wall (VW) and thrombus were analyzed by western blot, immunohistochemistry, and flow cytometry.

Investigating the role of receptor interacting protein kinase 3 in venous thrombosis.

Objective: Venous thromboembolism is a disease that encompasses both deep vein thrombosis and pulmonary embolism. Recent investigations have shown that receptor interacting protein kinase 3 (RIPK3), a protein known for its role in the programmed form of cell death necroptosis, may play a role in thrombosis. Specifically, RIPK3 has been shown to promote platelet activation in arterial thrombosis and mixed lineage kinase domain-like pseudokinase (MLKL), a protein downstream of RIPK3 in the necroptosis pathway, has been shown to promote neutrophil extracellular trap formation in deep vein thrombosis.

Modulation of interleukin-6 and its effect on late vein wall injury in a stasis mouse model of deep vein thrombosis.

Objective: Deep vein thrombosis (DVT) and its sequela, post-thrombotic syndrome (PTS), remain a clinically significant problem. Interleukin-6 (IL-6) is a proinflammatory cytokine that is elevated in patients who develop PTS. We hypothesized that genetic deletion of IL-6 and the use of anti-IL-6 pharmacologic agents would be associated with decreased late vein wall injury.

Durability of mRNA-1273 vaccine-induced antibodies against SARS-CoV-2 variants.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mutations may diminish vaccine-induced protective immune responses, particularly as antibody titers wane over time. Here, we assess the effect of SARS-CoV-2 variants B.1.

Durability of mRNA-1273-induced antibodies against SARS-CoV-2 variants.

Unlabelled: SARS-CoV-2 mutations may diminish vaccine-induced protective immune responses, and the durability of such responses has not been previously reported. Here, we present a comprehensive assessment of the impact of variants B.1.

Safety and Immunogenicity of SARS-CoV-2 mRNA-1273 Vaccine in Older Adults.

Background: Testing of vaccine candidates to prevent infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in an older population is important, since increased incidences of illness and death from coronavirus disease 2019 (Covid-19) have been associated with an older age.

Methods: We conducted a phase 1, dose-escalation, open-label trial of a messenger RNA vaccine, mRNA-1273, which encodes the stabilized prefusion SARS-CoV-2 spike protein (S-2P) in healthy adults. The trial was expanded to include 40 older adults, who were stratified according to age (56 to 70 years or ≥71 years).

Ly6CLo Monocyte/Macrophages are Essential for Thrombus Resolution in a Murine Model of Venous Thrombosis.

Venous thrombosis (VT) resolution is a complex process, resembling sterile wound healing. Infiltrating blood-derived monocyte/macrophages (Mo/MΦs) are essential for the regulation of inflammation in tissue repair. These cells differentiate into inflammatory (CD11bLy6C) or proreparative (CD11bLy6C) subtypes.

Pre-Clinical Model to Study Recurrent Venous Thrombosis in the Inferior Vena Cava.

Background: Patients undergoing deep vein thrombosis (VT) have over 30% recurrence, directly increasing their risk of post-thrombotic syndrome. Current murine models of inferior vena cava (IVC) VT model host one thrombosis event.

Objective: We aimed to develop a murine model to study IVC recurrent VT in mice.

Intranasal Live Influenza Vaccine Priming Elicits Localized B Cell Responses in Mediastinal Lymph Nodes.

Pandemic live attenuated influenza vaccines (pLAIV) prime subjects for a robust neutralizing antibody response upon subsequent administration of a pandemic inactivated subunit vaccine (pISV). However, a difference was not detected in H5-specific memory B cells in the peripheral blood between pLAIV-primed and unprimed subjects prior to pISV boost. To investigate the mechanism underlying pLAIV priming, we vaccinated groups of 12 African green monkeys (AGMs) with H5N1 pISV or pLAIV alone or H5N1 pLAIV followed by pISV and examined immunity systemically and in local draining lymph nodes (LN).

In a randomized trial, the live attenuated tetravalent dengue vaccine TV003 is well-tolerated and highly immunogenic in subjects with flavivirus exposure prior to vaccination.

Unlabelled: Infection caused by the four serotypes of dengue virus (DENV-1-4) is a leading cause of mosquito-borne disease. Clinically-severe dengue disease is more common when secondary dengue infection occurs following prior infection with a heterologous dengue serotype. Other flaviviruses such as yellow fever virus, Japanese encephalitis virus, and Zika virus, can also elicit antibodies which are cross-reactive to DENV.

A Live Attenuated Chimeric West Nile Virus Vaccine, rWN/DEN4Δ30, Is Well Tolerated and Immunogenic in Flavivirus-Naive Older Adult Volunteers.

West Nile virus (WNV) is a major cause of mosquito-borne illness in the United States. Human disease ranges from mild febrile illness to severe fatal neurologic infection. Adults aged >60 years are more susceptible to neuroinvasive disease accompanied by a high mortality rate or long-lasting neurologic sequelae.

Intact Toll-like receptor 9 signaling in neutrophils modulates normal thrombogenesis in mice.

Background: Deletion of Toll-like receptor 9 (Tlr9) signaling, which is important for sterile inflammatory processes, results in impaired resolution of venous thrombosis (VT) in mice. The purpose of this study was to determine if deletion of Tlr9 affected sterile necrosis, apoptosis, and neutrophil extracellular trap (NET) production in VT.

Methods: Stasis and nonstasis murine models of VT were used in wild-type (WT) and Tlr9 mice, with assessment of thrombus size and determination of NETs, necrosis, and apoptosis markers.

Gram-Negative Pneumonia Alters Large-Vein Cell-Adhesion Molecule Profile and Potentiates Experimental Stasis Venous Thrombosis.

Background/aims: Pneumonia is a significant risk factor for the development of venous thrombosis (VT). Cell-adhesion molecules (CAMs) are linked to the pathogenesis of both pneumonia and VT. We hypothesized that remote infection would confer a prothrombogenic milieu via systemic elevation of CAMs.

In Vivo Role of Neutrophil Extracellular Traps in Antiphospholipid Antibody-Mediated Venous Thrombosis.

Objective: Antiphospholipid syndrome (APS) is a leading acquired cause of thrombotic events. Although antiphospholipid antibodies have been shown to promote thrombosis in mice, the role of neutrophils has not been explicitly studied. The aim of this study was to characterize neutrophils in the context of a new model of antiphospholipid antibody-mediated venous thrombosis.

Alterations in macrophage phenotypes in experimental venous thrombosis.

Objective: Macrophages are involved in venous thrombus (VT) resolution and vein wall remodeling. This study was undertaken to identify variations in macrophage phenotypes in thrombi and vein wall in multiple models of VT to clarify the natural history of macrophage polarization in clearance of VT. We also sought to demonstrate the feasibility of macrophage phenotyping in human VT.

Generation and Protective Ability of Influenza Virus-Specific Antibody-Dependent Cellular Cytotoxicity in Humans Elicited by Vaccination, Natural Infection, and Experimental Challenge.

Background: Nonneutralizing antibodies (Abs) involved in antibody-dependent cellular cytotoxicity (ADCC) may provide some protection from influenza virus infection. The ability of influenza vaccines to induce ADCC-mediating Abs (ADCC-Abs) in adults and children is unclear.

Methods: We quantified ADCC-Abs in serum samples from adults who received a dose of inactivated subunit vaccine (ISV) targeting monovalent 2009 pandemic influenza A(H1N1) virus or live-attenuated influenza vaccine (LAIV) or who had laboratory-confirmed influenza A(H1N1) virus infection.

The live attenuated dengue vaccine TV003 elicits complete protection against dengue in a human challenge model.

A dengue human challenge model can be an important tool to identify candidate dengue vaccines that should be further evaluated in large efficacy trials in endemic areas. Dengue is responsible for about 390 million infections annually. Protective efficacy results for the most advanced dengue vaccine candidate (CYD) were disappointing despite its ability to induce neutralizing antibodies against all four dengue virus (DENV) serotypes.