Interrogation of Antigen Display on Individual Vaccine Nanoparticles for Achieving Neutralizing Antibody Responses against Hepatitis C Virus

Induction of cross-neutralizing antibodies by a permuted hepatitis C virus glycoprotein nanoparticle vaccine candidate

Hepatitis C virus (HCV) infection affects approximately 58 million people and causes ~300,000 deaths yearly. The only target for HCV neutralizing antibodies is the highly sequence diverse E1E2 glycoprotein. Eliciting broadly neutralizing antibodies that recognize conserved cross-neutralizing epitopes is important for an effective HCV vaccine. However, most recombinant HCV glycoprotein vaccines, which usually include only E2, induce only weak neutralizing antibody responses. Here, we describe recombinant soluble E1E2 immunogens that were generated by permutation of the E1 and E2 subunits. We displayed the E2E1 immunogens on two-component nanoparticles and these nanoparticles induce significantly more potent neutralizing antibody responses than E2. Next, we generated mosaic nanoparticles co-displaying six different E2E1 immunogens. These mosaic E2E1 nanoparticles elicit significantly improved neutralization compared to monovalent E2E1 nanoparticles. These results provide a roadmap for the generation of an HCV vaccine that induces potent and broad neutralization.

Emerging vaccine nanotechnology: From defense against infection to sniping cancer

Looking retrospectively at the development of humanity, vaccination is an unprecedented medical landmark that saves lives by harnessing the human immune system. During the ongoing coronavirus disease 2019 (COVID-19) pandemic, vaccination is still the most effective defense modality. The successful clinical application of the lipid nanoparticle-based Pfizer/BioNTech and Moderna mRNA COVID-19 vaccines highlights promising future of nanotechnology in vaccine development. Compared with conventional vaccines, nanovaccines are supposed to have advantages in lymph node accumulation, antigen assembly, and antigen presentation; they also have, unique pathogen biomimicry properties because of well-organized combination of multiple immune factors. Beyond infectious diseases, vaccine nanotechnology also exhibits considerable potential for cancer treatment. The ultimate goal of cancer vaccines is to fully mobilize the potency of the immune system as a living therapeutic to recognize tumor antigens and eliminate tumor cells, and nanotechnologies have the requisite properties to realize this goal. In this review, we summarize the recent advances in vaccine nanotechnology from infectious disease prevention to cancer immunotherapy and highlight the different types of materials, mechanisms, administration methods, as well as future perspectives.

DNA-Directed Patterning for Versatile Validation and Characterization of a Lipid-Based Nanoparticle Model of SARS-CoV-2

Lipid-based nanoparticles have been applied extensively in drug delivery and vaccine strategies and are finding diverse applications in the coronavirus disease 2019 (COVID-19) pandemic-from vaccine-component encapsulation to modeling the virus, itself. High-throughput, highly flexible methods for characterization are of great benefit to the development of liposomes featuring surface proteins. DNA-directed patterning is one such method that offers versatility in immobilizing and segregating lipid-based nanoparticles for subsequent analysis. Here, oligonucleotides are selectively conjugated onto a glass substrate and then hybridized to complementary oligonucleotides tagged to liposomes, patterning them with great control and precision. The power of DNA-directed patterning is demonstrated by characterizing a novel recapitulative lipid-based nanoparticle model of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-S-liposomes-that presents the SARS-CoV-2 spike (S) protein on its surface. Patterning a mixture of S-liposomes and liposomes that display the tetraspanin CD63 to discrete regions of a substrate shows that angiotensin-converting enzyme 2 (ACE2) specifically binds to S-liposomes. Subsequent introduction of S-liposomes to ACE2-expressing cells tests the biological function of S-liposomes and shows agreement with DNA-directed patterning-based assays. Finally, multiplexed patterning of S-liposomes verifies the performance of commercially available neutralizing antibodies against the two S variants. Overall, DNA-directed patterning enables a wide variety of custom assays for the characterization of any lipid-based nanoparticle.

3D printing technologies for in vitro vaccine testing platforms and vaccine delivery systems against infectious diseases

Recent advances in 3D printing (3DP) and tissue engineering approaches enable the potential application of these technologies to vaccine research. Reconstituting the native tissue or cellular microenvironment will be vital for successful evaluation of pathogenicity of viral infection and screening of potential vaccines. Therefore, establishing a reliable in vitro model to study the vaccine efficiency or delivery of viral disease is important. Here, this review summarizes two major ways that tissue engineering and 3DP strategies could contribute to vaccine research: (1) 3D human tissue models to study the response to virus can be served as a testbed for new potential therapeutics. Using 3D tissue platform attempts to explore alternative options to pre-clinical animal research for evaluating vaccine candidates. (2) 3DP technologies can be applied to improve the vaccination strategies which could replace existing vaccine delivery. Controlled antigen release using carriers that are generated with biodegradable biomaterials can further enhance the efficient development of immunity as well as combination of multiple-dose vaccines into a single injection. This mini review discusses the up-to-date report of current 3D tissue/organ models for potential vaccine potency and known bioengineered vaccine delivery systems.

Immunopotentiating and Delivery Systems for HCV Vaccines

Development of preventive vaccines against hepatitis C virus (HCV) remains one of the main strategies in achieving global elimination of the disease. The effort is focused on the quest for vaccines capable of inducing protective cross-neutralizing humoral and cellular immune responses, which in turn dictate the need for rationally designed cross-genotype vaccine antigens and potent immunoadjuvants systems. This review provides an assessment of the current state of knowledge on immunopotentiating compounds and vaccine delivery systems capable of enhancing HCV antigen-specific immune responses, while focusing on the synergy and interplay of two modalities. Structural, physico-chemical, and biophysical features of these systems are discussed in conjunction with the analysis of their in vivo performance. Extreme genetic diversity of HCV-a well-known hurdle in the development of an HCV vaccine, may also present a challenge in a search for an effective immunoadjuvant, as the effort necessitates systematic and comparative screening of rationally designed antigenic constructs. The progress may be accelerated if the preference is given to well-defined molecular immunoadjuvants with greater formulation flexibility and adaptability, including those capable of spontaneous self-assembly behavior, while maintaining their robust immunopotentiating and delivery capabilities.

Structure-Based and Rational Design of a Hepatitis C Virus Vaccine

A hepatitis C virus (HCV) vaccine is a critical yet unfulfilled step in addressing the global disease burden of HCV. While decades of research have led to numerous clinical and pre-clinical vaccine candidates, these efforts have been hindered by factors including HCV antigenic variability and immune evasion. Structure-based and rational vaccine design approaches have capitalized on insights regarding the immune response to HCV and the structures of antibody-bound envelope glycoproteins. Despite successes with other viruses, designing an immunogen based on HCV glycoproteins that can elicit broadly protective immunity against HCV infection is an ongoing challenge. Here, we describe HCV vaccine design approaches where immunogens were selected and optimized through analysis of available structures, identification of conserved epitopes targeted by neutralizing antibodies, or both. Several designs have elicited immune responses against HCV in vivo, revealing correlates of HCV antigen immunogenicity and breadth of induced responses. Recent studies have elucidated the functional, dynamic and immunological features of key regions of the viral envelope glycoproteins, which can inform next-generation immunogen design efforts. These insights and design strategies represent promising pathways to HCV vaccine development, which can be further informed by successful immunogen designs generated for other viruses.

From Structural Studies to HCV Vaccine Design

Hepatitis C virus (HCV) is a serious and growing public health problem despite recent developments of antiviral therapeutics. To achieve global elimination of HCV, an effective cross-genotype vaccine is needed. The failure of previous vaccination trials to elicit an effective cross-reactive immune response demands better vaccine antigens to induce a potent cross-neutralizing response to improve vaccine efficacy. HCV E1 and E2 envelope (Env) glycoproteins are the main targets for neutralizing antibodies (nAbs), which aid in HCV clearance and protection. Therefore, a molecular-level understanding of the nAb responses against HCV is imperative for the rational design of cross-genotype vaccine antigens. Here we summarize the recent advances in structural studies of HCV Env and Env-nAb complexes and how they improve our understanding of immune recognition of HCV. We review the structural data defining HCV neutralization epitopes and conformational plasticity of the Env proteins, and the knowledge applicable to rational vaccine design.

To Include or Occlude: Rational Engineering of HCV Vaccines for Humoral Immunity

Direct-acting antiviral agents have proven highly effective at treating existing hepatitis C infections but despite their availability most countries will not reach the World Health Organization targets for elimination of HCV by 2030. A prophylactic vaccine remains a high priority. Whilst early vaccines focused largely on generating T cell immunity, attention is now aimed at vaccines that generate humoral immunity, either alone or in combination with T cell-based vaccines. High-resolution structures of hepatitis C viral glycoproteins and their interaction with monoclonal antibodies isolated from both cleared and chronically infected people, together with advances in vaccine technologies, provide new avenues for vaccine development.

Advances in nanomaterial vaccine strategies to address infectious diseases impacting global health

Despite the overwhelming success of vaccines in preventing infectious diseases, there remain numerous globally devastating diseases without fully protective vaccines, particularly human immunodeficiency virus (HIV), malaria and tuberculosis. Nanotechnology approaches are being developed both to design new vaccines against these diseases as well as to facilitate their global implementation. The reasons why a given pathogen may present difficulties for vaccine design are unique and tied to the co-evolutionary history of the pathogen and humans, but there are common challenges that nanotechnology is beginning to help address. In each case, a successful vaccine will need to raise immune responses that differ from the immune responses raised by normal infection. Nanomaterials, with their defined compositions, commonly modular construction, and length scales allowing the engagement of key immune pathways, collectively facilitate the iterative design process necessary to identify such protective immune responses and achieve them reliably. Nanomaterials also provide strategies for engineering the trafficking and delivery of vaccine components to key immune cells and lymphoid tissues, and they can be highly multivalent, improving their engagement with the immune system. This Review will discuss these aspects along with recent nanomaterial advances towards vaccines against infectious disease, with a particular emphasis on HIV/AIDS, malaria and tuberculosis.

Biomaterials-based formulations and surfaces to combat viral infectious diseases

Rapidly growing viral infections are potent risks to public health worldwide. Accessible virus-specific antiviral vaccines and drugs are therapeutically inert to emerging viruses, such as Zika, Ebola, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Therefore, discovering ways to prevent and control viral infections is among the foremost medical challenge of our time. Recently, innovative technologies are emerging that involve the development of new biomaterial-based formulations and surfaces endowed with broad-spectrum antiviral properties. Here, we review emerging biomaterials technologies for controlling viral infections. Relevant advances in biomaterials employed with nanotechnology to inactivate viruses or to inhibit virus replication and further their translation in safe and effective antiviral formulations in clinical trials are discussed. We have included antiviral approaches based on both organic and inorganic nanoparticles (NPs), which offer many advantages over molecular medicine. An insight into the development of immunomodulatory scaffolds in designing new platforms for personalized vaccines is also considered. Substantial research on natural products and herbal medicines and their potential in novel antiviral drugs are discussed. Furthermore, to control contagious viral infections, i.e., to reduce the viral load on surfaces, current strategies focusing on biomimetic anti-adhesive surfaces through nanostructured topography and hydrophobic surface modification techniques are introduced. Biomaterial surfaces functionalized with antimicrobial polymers and nanoparticles against viral infections are also discussed. We recognize the importance of research on antiviral biomaterials and present potential strategies for future directions in applying these biomaterial-based approaches to control viral infections and SARS-CoV-2.

Lipid-based vaccine nanoparticles for induction of humoral immune responses against HIV-1 and SARS-CoV-2

The current health crisis of corona virus disease 2019 (COVID-19) highlights the urgent need for vaccine systems that can generate potent and protective immune responses. Protein vaccines are safe, but conventional approaches for protein-based vaccines often fail to elicit potent and long-lasting immune responses. Nanoparticle vaccines designed to co-deliver protein antigens and adjuvants can promote their delivery to antigen-presenting cells and improve immunogenicity. However, it remains challenging to develop vaccine nanoparticles that can preserve and present conformational epitopes of protein antigens for induction of neutralizing antibody responses. Here, we have designed a new lipid-based nanoparticle vaccine platform (NVP) that presents viral proteins (HIV-1 and SARS-CoV-2 antigens) in a conformational manner for induction of antigen-specific antibody responses. We show that NVP was readily taken up by dendritic cells (DCs) and promoted DC maturation and antigen presentation. NVP loaded with BG505.SOSIP.664 (SOSIP) or SARS-CoV-2 receptor-binding domain (RBD) was readily recognized by neutralizing antibodies, indicating the conformational display of antigens on the surfaces of NVP. Rabbits immunized with SOSIP-NVP elicited strong neutralizing antibody responses against HIV-1. Furthermore, mice immunized with RBD-NVP induced robust and long-lasting antibody responses against RBD from SARS-CoV-2. These results suggest that NVP is a promising platform technology for vaccination against infectious pathogens.

Evaluation of a Series of Lipidated Tucaresol Adjuvants in a Hepatitis C Virus Vaccine Model

Hepatitis C virus (HCV) infections represent a global health challenge; however, developing a vaccine for treatment of HCV infection has remained difficult as heterogeneous HCV contains distinct genotypes, and each genotype contains various subtypes and different envelope glycoproteins. Currently, there is no effective preventive vaccine for achieving global control over HCV. In our efforts to improve upon current HCV vaccines we designed a synthetically accessible adjuvant platform, wherein we synthesized 11 novel lipidated tucaresol analogues to assess their immunological potential. Using a tucaresol-based adjuvant approach, truncated lipid-variants together with an engineered E1E2 antigen construct, namely E2ΔTM3, elicited antibody (Ab) responses that were significantly higher than tucaresol. In sum, antibody end-point titer values largely corroborated HCV neutralization data with a simplified lipidated tucaresol variant affording the highest end point titer and % neutralization. This study lays the groundwork for additional permutations in tucaresol adjuvant design, including the examination of other proteins in vaccine development.

Nano-based approaches in the development of antiviral agents and vaccines

Outbreaks and the rapid transmission of viruses, such as coronaviruses and influenza viruses, are serious threats to human health. A major challenge in combating infectious diseases caused by viruses is the lack of effective methods for prevention and treatment. Nanotechnology has provided a basis for the development of novel antiviral strategies. Owing to their large modifiable surfaces that can be functionalized with multiple molecules to realize sophisticated designs, nanomaterials have been developed as nanodrugs, nanocarriers, and nano-based vaccines to effectively induce sufficient immunologic memory. From this perspective, we introduce various nanomaterials with diverse antiviral mechanisms and summarize how nano-based antiviral agents protect against viral infection at the molecular, cellular, and organismal levels. We summarize the applications of nanomaterials for defense against emerging viruses by trapping and inactivating viruses and inhibiting viral entry and replication. We also discuss recent progress in nano-based vaccines with a focus on the mechanisms by which nanomaterials contribute to immunogenicity. We further describe how nanotechnology may improve vaccine efficacy by delivering large amounts of antigens to target immune cells and enhancing the immune response by mimicking viral structures and activating dendritic cells. Finally, we provide an overview of future prospects for nano-based antiviral agents and vaccines.

Optimized Hepatitis C Virus (HCV) E2 Glycoproteins and their Immunogenicity in Combination with MVA-HCV

Hepatitis C virus (HCV) represents a major global health challenge and an efficient vaccine is urgently needed. Many HCV vaccination strategies employ recombinant versions of the viral E2 glycoprotein. However, recombinant E2 readily forms disulfide-bonded aggregates that might not be optimally suited for vaccines. Therefore, we have designed an E2 protein in which we strategically changed eight cysteines to alanines (E2.C8A). E2.C8A formed predominantly monomers and virtually no aggregates. Furthermore, E2.C8A also interacted more efficiently with broadly neutralizing antibodies than conventional E2. We used mice to evaluate different prime/boost immunization strategies involving a modified vaccinia virus Ankara (MVA) expressing the nearly full-length genome of HCV (MVA-HCV) in combination with either the E2 aggregates or the E2.C8A monomers. The combined MVA-HCV/E2 aggregates prime/boost strategy markedly enhanced HCV-specific effector memory CD4⁺ T cell responses and antibody levels compared to MVA-HCV/MVA-HCV. Moreover, the aggregated form of E2 induced higher levels of anti-E2 antibodies in vaccinated mice than E2.C8A monomers. These antibodies were cross-reactive and mainly of the IgG1 isotype. Our findings revealed how two E2 viral proteins that differ in their capacity to form aggregates are able to enhance to different extent the HCV-specific cellular and humoral immune responses, either alone or in combination with MVA-HCV. These combined protocols of MVA-HCV/E2 could serve as a basis for the development of a more effective HCV vaccine.

Proof of concept for rational design of hepatitis C virus E2 core nanoparticle vaccines

Hepatitis C virus (HCV) envelope glycoproteins E1 and E2 are responsible for cell entry, with E2 being the major target of neutralizing antibodies (NAbs). Here, we present a comprehensive strategy for B cell-based HCV vaccine development through E2 optimization and nanoparticle display. We redesigned variable region 2 in a truncated form (tVR2) on E2 cores derived from genotypes 1a and 6a, resulting in improved stability and antigenicity. Crystal structures of three optimized E2 cores with human cross-genotype NAbs (AR3s) revealed how the modified tVR2 stabilizes E2 without altering key neutralizing epitopes. We then displayed these E2 cores on 24- and 60-meric nanoparticles and achieved substantial yield and purity, as well as enhanced antigenicity. In mice, these nanoparticles elicited more effective NAb responses than soluble E2 cores. Next-generation sequencing (NGS) defined distinct B cell patterns associated with nanoparticle-induced antibody responses, which target the conserved neutralizing epitopes on E2 and cross-neutralize HCV genotypes.

Biomaterials as Tools to Decode Immunity

The immune system has remarkable capabilities to combat disease with exquisite selectivity. This feature has enabled vaccines that provide protection for decades and, more recently, advances in immunotherapies that can cure some cancers. Greater control over how immune signals are presented, delivered, and processed will help drive even more powerful options that are also safe. Such advances will be underpinned by new tools that probe how immune signals are integrated by immune cells and tissues. Biomaterials are valuable resources to support this goal, offering robust, tunable properties. The growing role of biomaterials as tools to dissect immune function in fundamental and translational contexts is highlighted. These technologies can serve as tools to understand the immune system across molecular, cellular, and tissue length scales. A common theme is exploiting biomaterial features to rationally direct how specific immune cells or organs encounter a signal. This precision strategy, enabled by distinct material properties, allows isolation of immunological parameters or processes in a way that is challenging with conventional approaches. The utility of these capabilities is demonstrated through examples in vaccines for infectious disease and cancer immunotherapy, as well as settings of immune regulation that include autoimmunity and transplantation.

Materials for Immunotherapy

Breakthroughs in materials engineering have accelerated the progress of immunotherapy in preclinical studies. The interplay of chemistry and materials has resulted in improved loading, targeting, and release of immunomodulatory agents. An overview of the materials that are used to enable or improve the success of immunotherapies in preclinical studies is presented, from immunosuppressive to proinflammatory strategies, with particular emphasis on technologies poised for clinical translation. The materials are organized based on their characteristic length scale, whereby the enabling feature of each technology is organized by the structure of that material. For example, the mechanisms by which i) nanoscale materials can improve targeting and infiltration of immunomodulatory payloads into tissues and cells, ii) microscale materials can facilitate cell-mediated transport and serve as artificial antigen-presenting cells, and iii) macroscale materials can form the basis of artificial microenvironments to promote cell infiltration and reprogramming are discussed. As a step toward establishing a set of design rules for future immunotherapies, materials that intrinsically activate or suppress the immune system are reviewed. Finally, a brief outlook on the trajectory of these systems and how they may be improved to address unsolved challenges in cancer, infectious diseases, and autoimmunity is presented.

Hepatitis C Virus Vaccine: Challenges and Prospects

The hepatitis C virus (HCV) causes both acute and chronic infection and continues to be a global problem despite advances in antiviral therapeutics. Current treatments fail to prevent reinfection and remain expensive, limiting their use to developed countries, and the asymptomatic nature of acute infection can result in individuals not receiving treatment and unknowingly spreading HCV. A prophylactic vaccine is therefore needed to control this virus. Thirty years since the discovery of HCV, there have been major gains in understanding the molecular biology and elucidating the immunological mechanisms that underpin spontaneous viral clearance, aiding rational vaccine design. This review discusses the challenges facing HCV vaccine design and the most recent and promising candidates being investigated.

Integrating Biomaterials and Immunology to Improve Vaccines Against Infectious Diseases

Despite the success of vaccines in preventing many infectious diseases, effective vaccines against pathogens with ongoing challenges - such as HIV, malaria, and tuberculosis - remain unavailable. The emergence of new pathogen variants, the continued prevalence of existing pathogens, and the resurgence of yet other infectious agents motivate the need for new, interdisciplinary approaches to direct immune responses. Many current and candidate vaccines, for example, are poorly immunogenic, provide only transient protection, or create risks of regaining pathogenicity in certain immune-compromised conditions. Recent advances in biomaterials research are creating new potential to overcome these challenges through improved formulation, delivery, and control of immune signaling. At the same time, many of these materials systems - such as polymers, lipids, and self-assembly technologies - may achieve this goal while maintaining favorable safety profiles. This review highlights ways in which biomaterials can advance existing vaccines to safer, more efficacious technologies, and support new vaccines for pathogens that do not yet have vaccines. Biomaterials that have not yet been applied to vaccines for infectious disease are also discussed, and their potential in this area is highlighted.

Core-Shell-Heterostructured Magnetic-Plasmonic Nanoassemblies with Highly Retained Magnetic-Plasmonic Activities for Ultrasensitive Bioanalysis in Complex Matrix

Herein, a facile self-assembly strategy for coassembling oleic acid-coated iron oxide nanoparticles (OC-IONPs) with oleylamine-coated gold nanoparticles (OA-AuNPs) to form colloidal magnetic-plasmonic nanoassemblies (MPNAs) is reported. The resultant MPNAs exhibit a typical core-shell heterostructure comprising aggregated OA-AuNPs as a plasmonic core surrounded by an assembled magnetic shell of OC-IONPs. Owing to the high loading of OA-AuNPs and reasonable spatial distribution of OC-IONPs, the resultant MPNAs exhibit highly retained magnetic-plasmonic activities simultaneously. Using the intrinsic dual functionality of MPNAs as a magnetic separator and a plasmonic signal transducer, it is demonstrated that the assembled MPNAs can achieve the simultaneous magnetic manipulation and optical detection on the lateral flow immunoassay platform after surface functionalization with recognition molecules. In conclusion, the core-shell-heterostructured MPNAs can serve as a nanoanalytical platform for the separation and concentration of target compounds from complex biological samples using magnetic properties and simultaneous optical sensing using plasmonic properties.

Multilamellar Vaccine Particle Elicits Potent Immune Activation with Protein Antigens and Protects Mice against Ebola Virus Infection

Recent outbreaks of emerging infectious diseases, such as Ebola virus disease (EVD), highlight the urgent need to develop effective countermeasures, including prophylactic vaccines. Subunit proteins derived from pathogens provide a safe source of antigens for vaccination, but they are often limited by their low immunogenicity. We have developed a multilamellar vaccine particle (MVP) system composed of lipid-hyaluronic acid multi-cross-linked hybrid nanoparticles for vaccination with protein antigens and demonstrate their efficacy against Ebola virus (EBOV) exposure. MVPs efficiently accumulated in dendritic cells and promote antigen processing. Mice immunized with MVPs elicited robust and long-lasting antigen-specific CD8⁺ and CD4⁺ T cell immune responses as well as humoral immunity. A single-dose vaccination with MVPs delivering EBOV glycoprotein achieved an 80% protection rate against lethal EBOV infection. These results suggest that MVPs offer a promising platform for improving recombinant protein-based vaccine approaches.

Immunogenicity of recombinant fragment of orthopoxvirus p35 protein in mice

Despite the elimination of smallpox, orthopoxviruses continue to be a source of biological danger for humans, as cowpox and monkey pox viruses circulate in nature and the last virus can cause both sporadic cases of human diseases and outbreaks of smallpox-like infection. In addition, periodic vaccination is necessary for representatives of some professions (scientists studying pathogenic orthopoxviruses, medical personnel, etc.). Vaccination against smallpox virus with live vaccinia virus, which was widely used during the elimination of smallpox, induces the formation of long-term immunity in vaccinated people. However, providing a high level of protection, the vaccination is often accompanied by serious post-vaccination complications, the probability of which is particularly great for individuals with compromised immunity. In this regard, the development of preparations for the prevention and treatment of infections caused by orthopoxviruses remains important today. The aim of this study was to assess the immunogenicity in the mouse model of recombinant protein р35Δ12, designed previously on the base of the cowpox virus protein p35. It was previously shown that the protein р35Δ12 was recognized by fully human neutralizing anti-orthopoxviral antibody with high affinity. In this work, recombinant protein р35Δ12 produced in E. coli cells XL1-blue and purified by chromatography was used for two-time immunization of mice. Two weeks after the second immunization, blood samples were taken from mice and serum antibodies were analyzed. It was shown by ELISA and Western-blot analysis that immunized mice sera contained IgG antibodies specific to recombinant protein р35Δ12. Confocal microscopy showed that antibodies induced by the р35Δ12 protein were able to recognize Vero E6 cells infected with the LIVP-GFP vaccinia virus. In addition, the antibodies in the serum of immunized mice were able to neutralize the infectivity of the vaccinia virus LIVP-GFP in the plaque reduction neutralization test in vitro. These experiments have demonstrated promising properties of the р35Δ12 protein if it were used as a component of vaccine for prophylaxis of orthopoxvirus infections.