A Nanoparticle Vaccine Displaying Conserved Epitopes of the Preexisting Neutralizing Antibody Confers Broad Protection against SARS-CoV-2 Variants.

The rapid development of the SARS-CoV-2 vaccine has been used to prevent the spread of coronavirus 2019 (COVID-19). However, the ongoing and future pandemics caused by SARS-CoV-2 variants and mutations underscore the need for effective vaccines that provide broad-spectrum protection. Here, we developed a nanoparticle vaccine with broad protection against divergent SARS-CoV-2 variants. The corresponding conserved epitopes of the preexisting neutralizing (CePn) antibody were presented on a self-assembling Helicobacter pylori ferritin to generate the CePnF nanoparticle. Intranasal immunization of mice with CePnF nanoparticles induced robust humoral, cellular, and mucosal immune responses and a long-lasting immunity. The CePnF-induced antibodies exhibited cross-reactivity and neutralizing activity against different coronaviruses (CoVs). CePnF vaccination significantly inhibited the replication and pathology of SARS-CoV-2 Delta, WIV04, and Omicron strains in hACE2 transgenic mice and, thus, conferred broad protection against these SARS-CoV-2 variants. Our constructed nanovaccine targeting the conserved epitopes of the preexisting neutralizing antibodies can serve as a promising candidate for a universal SARS-CoV-2 vaccine.

An Intranasal Multivalent Epitope-Based Nanoparticle Vaccine Confers Broad Protection against Divergent Influenza Viruses.

The development of a universal influenza vaccine to control public health threats from circulating and emerging influenza viruses is highly desirable. Here we report an intranasal multivalent epitope-based nanoparticle vaccine with broad protection against divergent influenza A and B viruses. Three highly conserved epitopes consisting of the A α-helix of hemagglutinin (H), the ectodomain of matrix protein 2 (M) and the HCA-2 of neuraminidase (N) are presented on a self-assembling recombinant human heavy chain ferritin cage (F) to generate the HMNF nanoparticle. Intranasal immunization of mice with HMNF mobilized potent immune responses, including high levels of antigen-specific antibodies and T cell-mediated responses, which exhibited cross-reactivity to various antigen mutations. Vaccination with HMNF conferred full protection against lethal challenge with divergent influenza A and B viruses. The broad protection of HMNF nanoparticles could be attributed to the synergistic function of antibodies and T cells. Moreover, the induced immune responses are long-lasting, and protection is maintained six months after vaccination. Our constructed HMNF nanoparticle can serve as a promising candidate for a universal influenza vaccine.

Self-Assembling Nanovaccine Confers Complete Protection Against Zika Virus Without Causing Antibody-Dependent Enhancement.

The Zika virus (ZIKV) epidemic poses a substantial threat to the public, and the development of safe and effective vaccines is a demanding challenge. In this study, we constructed a kind of self-assembling nanovaccine which confers complete protection against ZIKV infection. The ZIKV envelop protein domain III (zEDIII) was presented on recombinant human heavy chain ferritin (rHF) to form the zEDIII-rHF nanoparticle. Immunization of mice with zEDIII-rHF nanoparticle in the absence of an adjuvant induced robust humoral and cellular immune responses. zEDIII-rHF vaccination conferred complete protection against lethal infection with ZIKV and eliminated pathological symptoms in the brain. Importantly, the zEDIII-rHF nanovaccine induced immune response did not cross-react with dengue virus-2, overcoming the antibody-dependent enhancement (ADE) problem that is a safety concern for ZIKV vaccine development. Our constructed zEDIII-rHF nanovaccine, with superior protective performance and avoidance of ADE, provides an effective and safe vaccine candidate against ZIKV.

T-Cell Immunoglobulin and Mucin Domain 1 (TIM-1) Is a Functional Entry Factor for Tick-Borne Encephalitis Virus.

Tick-borne encephalitis virus (TBEV) is the causative agent of a potentially fatal neurological infection affecting humans. The host factors required for viral entry have yet to be described. Here, we found that T-cell immunoglobulin and mucin domain 1 (TIM-1) acted as the cellular entry factor for TBEV. Using a virus overlay protein binding assay, TIM-1 was identified as a virion-interacting protein. Cells that were relatively resistant to TBEV infection became highly susceptible to infection when TIM-1 was ectopically expressed. TIM-1 knockout and viral RNA bypass assays showed that TIM-1 functioned in the entry phase of TBEV infection. TIM-1 mediated TBEV uptake and was cointernalized with virus particles into the cell. Antibodies for TIM-1, soluble TIM-1, or TIM-1 knockdown significantly inhibited TBEV infection in permissive cells. Furthermore, in TIM-1 knockout mice, TIM-1 deficiency markedly lowered viral burden and reduced mortality and morbidity, highlighting the functional relevance of TIM-1 in vivo. With TIM-1, we have identified a key host factor for TBEV entry and a potential target for antiviral intervention. IMPORTANCE TBEV is a tick-transmitted flavivirus that causes serious diseases in the human central nervous system in Eurasia. The host determinants required for viral entry remain poorly understood. Here, we found that TIM-1 is a cellular entry factor for TBEV. Antibodies directed at TIM-1 or soluble TIM-1 treatment decreased virus infection in cell cultures. TIM-1 was cointernalized with virus particles into cells. TIM-1 deficiency significantly lowered viral burden and attenuated pathogenesis in the murine TBEV infection model. The demonstration of TIM-1 as a cellular entry factor for TBEV will improve understanding of virus infection and provide a target for antiviral development.

Self-Assembled Nanoparticles: Exciting Platforms for Vaccination.

Vaccination is successfully advanced to control several fatal diseases and improve human life expectancy. However, additional innovations are required in this field because there are no effective vaccines to prevent some infectious diseases. The shift from the attenuated or inactivated pathogens to safer but less immunogenic protein or peptide antigens has led to a search for effective antigen delivery carriers that can function as both antigen vehicles and intrinsic adjuvants. Among these carriers, self-assembled nanoparticles (SANPs) have shown great potential to be the best representative. For the nanoscale and multiple presentation of antigens, with accurate control over size, geometry, and functionality, these nanoparticles are assembled spontaneously and mimic pathogens, resulting in enhanced antigen presentation and increased cellular and humoral immunity responses. In addition, they may be applied through needle-free routes due to their adhesive ability, which gives them a great future in vaccination applications. This review provides an overview of various SANPs and their applications in prophylactic vaccines.

Three-Fragment Fluorescence Complementation for Imaging of Ternary Complexes under Physiological Conditions.

Protein-protein interactions (PPIs) occur in a vast variety of cellular processes, and many processes are regulated by multiple protein interactions. Identification of PPIs is essential for the analysis of biological pathways and to further understand underlying molecular mechanisms. However, visualization and identification of multiprotein complexes, including ternary complexes in living cells under physiological conditions, remains challenging. In this work, we reported a three-fragment fluorescence complementation (TFFC) by splitting the Venus fluorescent protein for visualizing ternary complexes in living cells under physiological conditions. With this Venus-based TFFC system, we identified the multi-interaction of weak-affinity ternary complexes under physiological conditions. The TFFC system was further applied to the analysis of multi-interactions during the HIV-1 integration process, revealing the important role of the barrier-to-autointegration factor protein in HIV-1 integration. This TFFC system provides a useful tool for visualizing and identifying ternary complexes in living cells under physiological conditions.