Matrix-M Adjuvated Seasonal Virosomal Influenza Vaccine Induces Partial Protection in Mice and Ferrets against Avian H5 and H7 Challenge

A Comprehensive Overview on the Production of Vaccines in Plant-Based Expression Systems and the Scope of Plant Biotechnology to Combat against SARS-CoV-2 Virus Pandemics

Many pathogenic viral pandemics have caused threats to global health; the COVID-19 pandemic is the latest. Its transmission is growing exponentially all around the globe, putting constraints on the health system worldwide. A novel coronavirus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), causes this pandemic. Many candidate vaccines are available at this time for COVID-19, and there is a massive international race underway to procure as many vaccines as possible for each country. However, due to heavy global demand, there are strains in global vaccine production. The use of a plant biotechnology-based expression system for vaccine production also represents one part of this international effort, which is to develop plant-based heterologous expression systems, virus-like particles (VLPs)-vaccines, antiviral drugs, and a rapid supply of antigen-antibodies for detecting kits and plant origin bioactive compounds that boost the immunity and provide tolerance to fight against the virus infection. This review will look at the plant biotechnology platform that can provide the best fight against this global pandemic.

Adjuvantation of Influenza Vaccines to Induce Cross-Protective Immunity

Influenza poses a huge threat to global public health. Influenza vaccines are the most effective and cost-effective means to control influenza. Current influenza vaccines mainly induce neutralizing antibodies against highly variable globular head of hemagglutinin and lack cross-protection. Vaccine adjuvants have been approved to enhance seasonal influenza vaccine efficacy in the elderly and spare influenza vaccine doses. Clinical studies found that MF59 and AS03-adjuvanted influenza vaccines could induce cross-protective immunity against non-vaccine viral strains. In addition to MF59 and AS03 adjuvants, experimental adjuvants, such as Toll-like receptor agonists, saponin-based adjuvants, cholera toxin and heat-labile enterotoxin-based mucosal adjuvants, and physical adjuvants, are also able to broaden influenza vaccine-induced immune responses against non-vaccine strains. This review focuses on introducing the various types of adjuvants capable of assisting current influenza vaccines to induce cross-protective immunity in preclinical and clinical studies. Mechanisms of licensed MF59 and AS03 adjuvants to induce cross-protective immunity are also introduced. Vaccine adjuvants hold a great promise to adjuvant influenza vaccines to induce cross-protective immunity.

Matrix-M™ adjuvant enhances immunogenicity of both protein- and modified vaccinia virus Ankara-based influenza vaccines in mice

Influenza viruses continuously circulate in the human population and escape recognition by virus neutralizing antibodies induced by prior infection or vaccination through accumulation of mutations in the surface proteins hemagglutinin (HA) and neuraminidase (NA). Various strategies to develop a vaccine that provides broad protection against different influenza A viruses are under investigation, including use of recombinant (r) viral vectors and adjuvants. The replication-deficient modified vaccinia virus Ankara (MVA) is a promising vaccine vector that efficiently induces B and T cell responses specific for the antigen of interest. It is assumed that live vaccine vectors do not require an adjuvant to be immunogenic as the vector already mediates recruitment and activation of immune cells. To address this topic, BALB/c mice were vaccinated with either protein- or rMVA-based HA influenza vaccines, formulated with or without the saponin-based Matrix-M™ adjuvant. Co-formulation with Matrix-M significantly increased HA vaccine immunogenicity, resulting in antigen-specific humoral and cellular immune responses comparable to those induced by unadjuvanted rMVA-HA. Of special interest, rMVA-HA immunogenicity was also enhanced by addition of Matrix-M, demonstrated by enhanced HA inhibition antibody titres and cellular immune responses. Matrix-M added to either protein- or rMVA-based HA vaccines mediated recruitment and activation of antigen-presenting cells and lymphocytes to the draining lymph node 24 and 48 h post-vaccination. Taken together, these results suggest that adjuvants can be used not only with protein-based vaccines but also in combination with rMVA to increase vaccine immunogenicity, which may be a step forward to generate new and more effective influenza vaccines.

A Formulated TLR7/8 Agonist is a Flexible, Highly Potent and Effective Adjuvant for Pandemic Influenza Vaccines

Since 1997, highly pathogenic avian influenza viruses of the H5N1 subtype have been transmitted from avian hosts to humans. The severity of H5N1 infection in humans, as well as the sporadic nature of H5N1 outbreaks, both geographically and temporally, make generation of an effective vaccine a global public health priority. An effective H5N1 vaccine must ultimately provide protection against viruses from diverse clades. Toll-like receptor (TLR) agonist adjuvant formulations have a demonstrated ability to broaden H5N1 vaccine responses in pre-clinical models. However, many of these agonist molecules have proven difficult to develop clinically. Here, we describe comprehensive adjuvant formulation development of the imidazoquinoline TLR-7/8 agonist 3M-052, in combination with H5N1 hemagglutinin (HA) based antigens. We find that 3M-052 in multiple formulations protects both mice and ferrets from lethal H5N1 homologous virus challenge. Furthermore, we conclusively demonstrate the ability of 3M-052 adjuvant formulations to broaden responses to H5N1 HA based antigens, and show that this broadening is functional using a heterologous lethal virus challenge in ferrets. Given the extensive clinical use of imidazoquinoline TLR agonists for other indications, these studies identify multiple adjuvant formulations which may be rapidly advanced into clinical trials in an H5N1 vaccine.

Universal influenza vaccine design: directing the antibody repertoire

Influenza infections are responsible for a large health and economic burden. Vaccination is the best strategy to reduce influenza-related disease burden, but current vaccines have limited breadth and need near-annual reformulation. Developing new influenza vaccines that provide broad and long-lasting protection is an important goal. This review represents an overview of the current knowledge of the universal vaccine approach that focuses on the induction of broadly neutralizing antibodies targeting the hemagglutinin (HA) stem of influenza viruses. Adjuvation of existing influenza vaccines has so far had limited effect on the induction of broadly neutralizing antibodies. HA stem-based immunogens that lack the immunodominant HA head have shown promising results in preclinical models, providing evidence that a universal influenza vaccine is within reach.

Protection against H5N1 Influenza Virus Induced by Matrix-M Adjuvanted Seasonal Virosomal Vaccine in Mice Requires Both Antibodies and T Cells

Background

It remains important to develop the next generation of influenza vaccines that can provide protection against vaccine mismatched strains and to be prepared for potential pandemic outbreaks. To achieve this, the understanding of the immunological parameters that mediate such broad protection is crucial.

Method

In the current study we assessed the contribution of humoral and cellular immune responses to heterosubtypic protection against H5N1 induced by a Matrix-M (MM) adjuvanted seasonal influenza vaccine by serum transfer and T-cell depletion studies.

Results

We demonstrate that the heterosubtypic protection against H5N1 induced by MM adjuvanted vaccine is partially mediated by antibodies. The serum contained both H5N1 cross-reactive hemagglutinin (HA)- and neuraminidase (NA)-specific antibodies but with limited virus neutralizing and no hemagglutination inhibiting activity. The cross-reactive antibodies induced antibody-dependent cellular cytotoxicity (ADCC) in vitro, suggesting a role for the Fc part of the antibodies in protection against H5N1. Besides H5N1 specific antibody responses, cross-reactive HA- and NA-specific T-cell responses were induced by the adjuvanted vaccine. T-cell depletion experiments demonstrated that both CD4⁺ and CD8⁺ T cells contribute to protection.

Conclusion

Our study demonstrates that cross-protection against H5N1 induced by MM adjuvanted seasonal virosomal influenza vaccine requires both the humoral and cellular arm of the immune system.

Matrix-M™ adjuvation broadens protection induced by seasonal trivalent virosomal influenza vaccine

Background

Influenza virus infections are responsible for significant morbidity worldwide and therefore it remains a high priority to develop more broadly protective vaccines. Adjuvation of current seasonal influenza vaccines has the potential to achieve this goal.

Methods

To assess the immune potentiating properties of Matrix-M™, mice were immunized with virosomal trivalent seasonal vaccine adjuvated with Matrix-M™. Serum samples were isolated to determine the hemagglutination inhibiting (HAI) antibody titers against vaccine homologous and heterologous strains. Furthermore, we assess whether adjuvation with Matrix-M™ broadens the protective efficacy of the virosomal trivalent seasonal vaccine against vaccine homologous and heterologous influenza viruses.

Results

Matrix-M™ adjuvation enhanced HAI antibody titers and protection against vaccine homologous strains. Interestingly, Matrix-M™ adjuvation also resulted in HAI antibody titers against heterologous influenza B strains, but not against the tested influenza A strains. Even though the protection against heterologous influenza A was induced by the adjuvated vaccine, in the absence of HAI titers the protection was accompanied by severe clinical scores and body weight loss. In contrast, in the presence of heterologous HAI titers full protection against the heterologous influenza B strain without any disease symptoms was obtained.

Conclusion

The results of this study emphasize the promising potential of a Matrix-M™-adjuvated seasonal trivalent virosomal influenza vaccine. Adjuvation of trivalent virosomal vaccine does not only enhance homologous protection, but in addition induces protection against heterologous strains and thus provides overall more potent and broad protective immunity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-015-0435-9) contains supplementary material, which is available to authorized users.