Various Adjuvants Effect on Immunogenicity of Puumala Virus Vaccine

Achievement and Challenges in Orthohantavirus Vaccines

Orthohantaviruses (also known as hantaviruses) are pathogens that cause two distinct, yet related forms of severe human disease: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). These diseases pose a significant threat to global public health due to their high case fatality rates, which can range from 1% to 50%. In recent years, an increasing number of countries and regions have reported human cases, underscoring the urgent need for improved understanding, prevention, and treatment strategies. Given the severity of these diseases and the lack of specific post-exposure antiviral treatments, preventive measures are critical. For several decades, substantial efforts have been dedicated to developing orthohantavirus vaccines, leading to significant advancements. The first large-scale deployment involved inactivated vaccines, which played a crucial role in reducing HFRS incidence in South Korea and China. Subunit vaccines, viral vector vaccines, and virus-like particle (VLP) vaccines have also been extensively researched. Nucleic acid vaccines, including both mRNA and DNA vaccines, hold the greatest potential for future development due to their rapid design and production cycles, ability to elicit robust immune responses, ease of storage and transportation, and adaptable production platforms. Ongoing advancements in computer technology and artificial intelligence promise to further enhance the development of more effective orthohantavirus vaccines.

Safety and Immunogenicity of an Andes Virus DNA Vaccine by Needle-Free Injection: A Randomized, Controlled Phase 1 Study

BACKGROUND

Andes virus (ANDV), a rodent-borne hantavirus, causes hantavirus pulmonary syndrome (HPS). The safety and immunogenicity of a novel ANDV DNA vaccine was evaluated.

METHODS

Phase 1, double-blind, dose-escalation trial randomly assigned 48 healthy adults to placebo or ANDV DNA vaccine delivered via needle-free jet injection. Cohorts 1 and 2 received 2 mg of DNA or placebo in a 3-dose (days 1, 29, 169) or 4-dose (days 1, 29, 57, 169) schedule, respectively. Cohorts 3 and 4 received 4 mg of DNA or placebo in the 3-dose and 4-dose schedule, respectively. Subjects were monitored for safety and neutralizing antibodies by pseudovirion neutralization assay (PsVNA50) and plaque reduction neutralization test (PRNT50).

RESULTS

While 98% and 65% of subjects had at least 1 local or systemic solicited adverse event (AE), respectively, most AEs were mild or moderate; no related serious AEs were detected. Cohorts 2, 3, and 4 had higher seroconversion rates than cohort 1 and seropositivity of at least 80% by day 197, sustained through day 337. PsVNA50 geometric mean titers were highest for cohort 4 on and after day 197.

CONCLUSIONS

This first-in-human candidate HPS vaccine trial demonstrated that an ANDV DNA vaccine was safe and induced a robust, durable immune response. Clinical Trials Registration. NCT03682107.

Plant Viruses as Adjuvants for Next-Generation Vaccines and Immunotherapy

Vaccines are the cornerstone of infectious disease control and prevention. The outbreak of SARS-CoV-2 has confirmed the urgent need for a new approach to the design of novel vaccines. Plant viruses and their derivatives are being used increasingly for the development of new medical and biotechnological applications, and this is reflected in a number of preclinical and clinical studies. Plant viruses have a unique combination of features (biosafety, low reactogenicity, inexpensiveness and ease of production, etc.), which determine their potential. This review presents the latest data on the use of plant viruses with different types of symmetry as vaccine components and adjuvants in cancer immunotherapy. The discussion concludes that the most promising approaches might be those that use structurally modified plant viruses (spherical particles) obtained from the Tobacco mosaic virus. These particles combine high adsorption properties (as a carrier) with strong immunogenicity, as has been confirmed using various antigens in animal models. According to current research, it is evident that plant viruses have great potential for application in the development of vaccines and in cancer immunotherapy.

Immune response evaluation in the guinea pigs after immunization with the experimental Puumala virus vaccine

In the Russian Federation, the vaccine against hemorrhagic fever with renal syndrome is at the stage of preclinical and clinical trials. The aim of the study was to analyze an effect of vaccine schedule on neutralizing antibodies (nAB) dynamics in guinea pig models applied with experimental Puumala virus based hantavirus vaccine (HV). Quantitative evaluation of neutralizing antibodies was presented as antibody titer geometric mean expressed in binary logarithms (log2) by the 50% reduction of focus-forming units (FRNT50) in Vero cell in the focus reduction neutralization test. The HV dual inoculation to guinea pigs was carried out in 14 day intervals, booster injection was applied on day 182 after the onset, in the thigh muscle tissue by using 0.3 ml undiluted (HV-u/d) and in the 1/10 dilution (HV-1/10). nAB titer on day 14 after the first HV-u/d and HV-1/10 injection was measured to be at titer of 5.50.3 and 4.80.3, respectively. After the second injection, the nAB peak was as high as 90.2 on day 42 after the first HV-u/f injection, and 6.50.2 on day 14 after the HV-1/10 injection. nAB decreased down to 6.20.3 and 50.3, respectively, on day 364 after the first injection. The booster HV-u/d and HV-1/10 injection induced increase in nAB up to 9.50.3 and 6.50.3, respectively. After the booster injection, it induced significantly higher nAB observed on day 238 after the first HV-u/d injection and delayed up to the 294 day for the HV-1/10. The results of the study indicated the early formation of the immune response, long-term nAB persistence and significantly enhanced immune response after the booster injection on day 182, which indicated a potential for the booster injection a year later. The immunological efficacy and protective activity of the vaccine schedule may be finally assessed according to the results of clinical trials.

New formulation of a recombinant anthrax vaccine stabilised with structurally modified plant viruses

Anthrax is a disease caused by Bacillus anthracis. The most promising approach to the development of anthrax vaccine is use of the anthrax protective antigen (PA). At the same time, recombinant PA is a very unstable protein. Previously, the authors have designed a stable modified recombinant anthrax protective antigen with inactivated proteolytic sites and substituted deamidation sites (rPA83m). As a second approach to recombinant PA stabilisation, plant virus spherical particles (SPs) were used as a stabiliser. The combination of these two approaches was shown to be the most effective. Here, the authors report the results of a detailed study of the stability, immunogenicity and protectiveness of rPA83m + SPs compositions. These compositions were shown to be stable, provided high anti-rPA83m antibody titres in guinea pigs and were able to protect them from a fully virulent 81/1 Bacillus anthracis strain. Given these facts, the formulation of rPA83m + SPs compositions is considered to be a prospective anthrax vaccine candidate.

Long-term humoral immunogenicity, safety and protective efficacy of inactivated vaccine against reindeer rabies

The core element of the reindeer rabies eradication strategy is regular application of vaccines to obtain and uphold a vaccination coverage sufficient for the ceasing of rabies virus transmission. This article presents the results of reindeer humoral immunity intensity and duration study after the immunization with two form of inactivated rabies vaccines (adjuvanted liquid vaccine and non-adjuvanted lyophilized vaccine) based on the Shchelkovo-51 rabies virus strain. Efficiency of post-vaccine immunity was assessed by measuring the animal blood serum virus-neutralizing antibody level in a neutralization test. The study determined the efficient rabies vaccine injection dose as equal to 3 ml. A single dose of 3 ml of these vaccines induced stable production of specific neutralizing antibodies in reindeer as early as 7 day after administration, and by 30 days after immunization, it significantly exceeded the minimal threshold level accepted by OIE. Two doses of vaccines administration with an interval of 30 days are required to achieve a strong immunity with the rabies-specific virus-neutralizing antibody titer of more than 0.5 IU/ml for at least 2 years. Our data do not support the benefit of an adjuvanted vaccine for the prevention of rabies in reindeer.

Plant Viruses: New Opportunities under the Pandemic

During the pandemic, an urgent task has become to develop new vaccine platforms that will help fight the infection caused by SARS-CoV-2 and quickly respond to newly emerging pathogens. Plant viruses can make a significant contribution to the solution of this problem. Phytoviruses, having the properties of any viral particles (self-assembly, immunogenicity, nanosize), are safe for humans since plants and mammals have no common infectious agents. As a result of thermal rearrangement of the tobacco mosaic virus, spherical particles of a protein nature have been obtained, which have unique immunostimulation and adsorption properties and can play the role of a universal adjuvant platform to create vaccines. Based on these particles, a scheme for obtaining vaccine preparations is proposed. This technology resembles a toy construction set for children. The basis is spherical particles, on the surface of which there are toy blocks-antigens. The "blocks" can be removed, added, or replaced, and this does not take much time and resources. Based on spherical particles, a polyvalent vaccine candidate against COVID-19 has been created as an adjuvant platform.

Structurally Modified Plant Viruses and Bacteriophages with Helical Structure. Properties and Applications

Structurally modified virus particles can be obtained from the rod-shaped or filamentous virions of plant viruses and bacteriophages by thermal or chemical treatment. They have recently attracted attention of the researchers as promising biogenic platforms for the development of new biotechnologies. This review presents data on preparation, structure, and properties of the structurally modified virus particles. In addition, their biosafety for animals is considered, as well as the areas of application of such particles in biomedicine. A separate section is devoted to one of the most relevant and promising areas for the use of structurally modified plant viruses – design of vaccine candidates based on them.

Vaccine Candidate Against COVID-19 Based on Structurally Modified Plant Virus as an Adjuvant

A recombinant vaccine candidate has been developed based on the major coronaviruses’ antigen (S protein) fragments and a novel adjuvant—spherical particles (SPs) formed during tobacco mosaic virus thermal remodeling. The receptor-binding domain and the highly conserved antigenic fragments of the S2 protein subunit were chosen for the design of recombinant coronavirus antigens. The set of three antigens (Co1, CoF, and PE) was developed and used to create a vaccine candidate composed of antigens and SPs (SPs + 3AG). Recognition of SPs + 3AG compositions by commercially available antibodies against spike proteins of SARS-CoV and SARS-CoV-2 was confirmed. The immunogenicity testing of these compositions in a mouse model showed that SPs improved immune response to the CoF and PE antigens. Total IgG titers against both proteins were 9–16 times higher than those to SPs. Neutralizing activity against SARS-CoV-2 in serum samples collected from hamsters immunized with the SPs + 3AG was demonstrated.