Effect of Different Adjuvants on the Longevity and Strength of Humoral and Cellular Immune Responses to the HCV Envelope Glycoproteins

Comparison of the oncolytic activity of a replication-competent and a replication-deficient herpes simplex virus 1

In 2015, the oncolytic herpes simplex virus 1 (HSV-1) T-VEC (talimogene laherparepvec) was approved for intratumoral injection in non-resectable malignant melanoma. To determine whether viral replication is required for oncolytic activity, we compared replication-deficient HSV-1 d106S with replication-competent T-VEC. High infectious doses of HSV-1 d106S killed melanoma (n = 10), head-and-neck squamous cell carcinoma (n = 11), and chondrosarcoma cell lines (n = 2) significantly faster than T-VEC as measured by MTT metabolic activity, while low doses of T-VEC were more effective over time. HSV-1 d106S and, to a lesser extent T-VEC, triggered caspase-dependent early apoptosis as shown by pan-caspase inhibition and specific induction of caspases 3/7, 8, and 9. HSV-1 d106S induced a higher ratio of apoptosis-inducing infected cell protein (ICP) 0 to apoptosis-blocking ICP6 than T-VEC. T-VEC was oncolytic for an extended period of time as viral replication continued, which could be partially blocked by the antiviral drug aciclovir. High doses of T-VEC, but not HSV-1 d106S, increased interferon-β mRNA as part of the intrinsic immune response. When markers of immunogenic cell death were assessed, ATP was released more efficiently in the context of T-VEC than HSV-1 d106S infection, whereas HMGB1 was induced comparatively well. Overall, the early oncolytic effect on three different tumour entities was stronger with the non-replicative strain, while the replication-competent virus elicited a stronger innate immune response and more pronounced immunogenic cell death.

Intranasal administration of unadjuvanted SARS-CoV-2 spike antigen boosts antigen-specific immune responses induced by parenteral protein subunit vaccine prime in mice and hamsters

With the continued transmission of SARS-CoV-2 across widely vaccinated populations, it remains important to develop new vaccines and vaccination strategies capable of providing protective immunity and limiting the spread of disease. Heterologous prime-boost vaccination based on the selection of different vaccine formulations and administration routes for priming and booster doses presents a promising strategy for inducing broader immune responses in key systemic and respiratory mucosal compartments. Intranasal vaccination can induce mucosal immune responses at the site of SARS-CoV-2 infection; however, the lack of clinically approved mucosal adjuvants makes it difficult to induce robust immune responses with protein subunit vaccines. Herein, we evaluated the immunogenicity of heterologous prime-boost regimens in mice and hamsters based on a parenteral vaccination of the antigen in combination with sulfated lactosylarchaeol (SLA) archaeosomes, a liposome adjuvant comprised of a single semisynthetic archaeal lipid, followed by an intranasally administered unadjuvanted SARS-CoV-2 spike antigen. Intranasal administration of unadjuvanted spike to mice and hamsters increased serum spike-specific IgG titers and spike-neutralizing activity compared with nonboosted animals. Spike-specific IgA responses were also detected in the bronchoalveolar lavage fluid in the lungs of mice that received an intranasal boost. In hamsters, the intranasal boost showed high efficacy against SARS-CoV-2 infection by protecting from body weight loss and reducing viral titers in the lungs and nasal turbinate. Overall, our heterologous intramuscular prime-intranasal boost with SLA-adjuvanted and unadjuvanted spike, respectively, demonstrated the potential of protein subunit formulations to promote antigen-specific systemic and mucosal immune responses.

Sulfated Lactosyl Archaeol Archaeosome-Adjuvanted Vaccine Formulations Targeting Rabbit Hemorrhagic Disease Virus Are Immunogenic and Efficacious

Vaccines play an important role in maintaining human and animal health worldwide. There is continued demand for effective and safe adjuvants capable of enhancing antigen-specific responses to a target pathogen. Rabbit hemorrhagic disease virus (RHDV) is a highly contagious calicivirus that often induces high mortality rates in rabbits. Herein, we evaluated the activity of an experimental sulfated lactosyl archaeol (SLA) archaeosome adjuvant when incorporated in subunit vaccine formulations targeting RHDV. The subunit antigens consisted of RHDV-CRM₁₉₇ peptide conjugates or recombinant RHDV2 VP60. SLA was able to enhance antigen-specific antibody titers and cellular responses in mice and rabbits. Three weeks following immunization, antigen-specific antibody levels in rabbits vaccinated with RHDV2 VP60 + SLA were significantly higher than those immunized with antigen alone, with geomean titers of 7393 vs. 117. In addition, the SLA-adjuvanted VP60-based formulations were highly efficacious in a rabbit RHDV2 challenge model with up to 87.5% animals surviving the viral challenge. These findings demonstrate the potential utility of SLA adjuvants in veterinary applications and highlight its activity in different types of mammalian species.

Ether lipids from archaeas in nano-drug delivery and vaccination

Archaea are microorganisms more closely related to eukaryotes than bacteria. Almost 50 years after being defined as a new domain of life on earth, new species continue to be discovered and their phylogeny organized. The study of the relationship between their genetics and metabolism and some of their extreme habitats has even positioned them as a model of extraterrestrial life forms. Archaea, however, are deeply connected to the life of our planet: they can be found in arid, acidic, warm areas; on most of the earth's surface, which is cold (below 5 °C), playing a prominent role in the cycles of organic materials on a global scale and they are even part of our microbiota. The constituent materials of these microorganisms differ radically from those produced by eukaryotes and bacteria, and the nanoparticles that can be manufactured using their ether lipids as building blocks exhibit unique properties that are of interest in nanomedicine. Here, we present for the first time a complete overview of the pre-clinical applications of nanomedicines based on ether archaea lipids, focused on drug delivery and adjuvancy over the last 25 years, along with a discussion on their pros, cons and their future industrial implementation.

Inactivated genotype 1a, 2a and 3a HCV vaccine candidates induced broadly neutralising antibodies in mice

OBJECTIVE

A prophylactic vaccine is needed to control the HCV epidemic, with genotypes 1-3 causing >80% of worldwide infections. Vaccine development is hampered by HCV heterogeneity, viral escape including protection of conserved neutralising epitopes and suboptimal efficacy of HCV cell culture systems. We developed cell culture-based inactivated genotype 1-3 HCV vaccine candidates to present natively folded envelope proteins to elicit neutralising antibodies.

DESIGN

High-yield genotype 1a, 2a and 3a HCV were developed by serial passage of TNcc, J6cc and DBN3acc in Huh7.5 cells and engineering of acquired mutations detected by next-generation sequencing. Neutralising epitope exposure was determined in cell-based neutralisation assays using human monoclonal antibodies AR3A and AR4A, and polyclonal antibody C211. BALB/c mice were immunised with processed and inactivated genotype 1a, 2a or 3a viruses using AddaVax, a homologue of the licenced adjuvant MF-59. Purified mouse and patient serum IgG were assayed for neutralisation capacity; mouse IgG and immune-sera were assayed for E1/E2 binding.

RESULTS

Compared with the original viruses, high-yield viruses had up to ~1000 fold increased infectivity titres (peak titres: 6-7 log10 focus-forming units (FFU)/mL) and up to ~2470 fold increased exposure of conserved neutralising epitopes. Vaccine-induced IgG broadly neutralised genotype 1-6 HCV (EC50: 30-193 µg/mL; mean 71 µg/mL), compared favourably with IgG from chronically infected patients, and bound genotype 1-3 E1/E2; immune-sera endpoint titres reached up to 32 000.

CONCLUSION

High-yield genotype 1-3 HCV could be developed as basis for inactivated vaccine candidates inducing broadly neutralising antibodies in mice supporting further preclinical development.

Characterization of Systemic and Mucosal Humoral Immune Responses to an Adjuvanted Intranasal SARS-CoV-2 Protein Subunit Vaccine Candidate in Mice

Continuous viral evolution of SARS-CoV-2 has resulted in variants capable of immune evasion, vaccine breakthrough infections and increased transmissibility. New vaccines that invoke mucosal immunity may provide a solution to reducing virus transmission. Here, we evaluated the immunogenicity of intranasally administered subunit protein vaccines composed of a stabilized SARS-CoV-2 spike trimer or the receptor binding domain (RBD) adjuvanted with either cholera toxin (CT) or an archaeal lipid mucosal adjuvant (AMVAD). We show robust induction of immunoglobulin (Ig) G and IgA responses in plasma, nasal wash and bronchoalveolar lavage in mice only when adjuvant is used in the vaccine formulation. While the AMVAD adjuvant was more effective at inducing systemic antibodies against the RBD antigen than CT, CT was generally more effective at inducing overall higher IgA and IgG titers against the spike antigen in both systemic and mucosal compartments. Furthermore, vaccination with adjuvanted spike led to superior mucosal IgA responses than with the RBD antigen and produced broadly targeting neutralizing plasma antibodies against ancestral, Delta and Omicron variants in vitro; whereas adjuvanted RBD elicited a narrower antibody response with neutralizing activity only against ancestral and Delta variants. Our study demonstrates that intranasal administration of an adjuvanted protein subunit vaccine in immunologically naïve mice induced both systemic and mucosal neutralizing antibody responses that were most effective at neutralizing SARS-CoV-2 variants when the trimeric spike was used as an antigen compared to RBD.

Two-component vaccine consisting of virus-like particles displaying hepatitis C virus envelope protein 2 oligomers

Development of B-cell-based hepatitis C virus (HCV) vaccines that induce broadly neutralizing antibodies (bNAbs) is hindered by extensive sequence diversity and low immunogenicity of envelope glycoprotein vaccine candidates, most notably soluble E2 (sE2). To overcome this, we employed two-component approaches using self-assembling virus-like particles (cVLPs; component 1), displaying monomeric or oligomeric forms of HCV sE2 (sE2mono or sE2oligo; component 2). Immunization studies were performed in BALB/c mice and the neutralizing capacity of vaccine-induced antibodies was tested in cultured-virus-neutralizations, using HCV of genotypes 1–6. sE2-cVLP vaccines induced significantly higher levels of NAbs (p = 0.0065) compared to corresponding sE2 vaccines. Additionally, sE2oligo-cVLP was superior to sE2mono-cVLP in inducing bNAbs. Interestingly, human monoclonal antibody AR2A had reduced binding in ELISA to sE2oligo-cVLP compared with sE2mono-cVLP and competition ELISA using mouse sera from vaccinated animals indicated that sE2oligo-cVLP induced significantly less non-bNAbs AR2A (p = 0.0043) and AR1B (p = 0.017). Thus, cVLP-displayed oligomeric sE2 shows promise as an HCV vaccine candidate.

Evaluation of Adjuvant Activity and Bio-Distribution of Archaeosomes Prepared Using Microfluidic Technology

Archaeosomes, composed of sulfated lactosyl archaeol (SLA) glycolipids, have been proven to be an effective vaccine adjuvant in multiple preclinical models of infectious disease or cancer. They have classically been prepared using a thin-film hydration method with an average particle size of 100-200 nm. In this study, we developed methods to generate SLA archaeosomes at different sizes, i.e., 30 nm and 100 nm, via microfluidic mixing technology and evaluated their physicochemical characteristics, as well as adjuvant activity and in vivo biodistribution in mice. Archaeosomes, prepared using thin-film and microfluidic mixing techniques, had similar nanostructures and physicochemical characteristics, with both appearing stable during the course of this study when stored at 4 °C or 37 °C. They also demonstrated similar adjuvant activity when admixed with ovalbumin antigen and used to immunize mice, generating equivalent antigen-specific immune responses. Archaeosomes, labeled with CellVueTM NIR815, had an equivalent biodistribution with both sizes, namely the highest signal at the injection site at 24 h post injection, followed by liver, spleen and inguinal lymph node. The presence of SLA archaeosomes of either size helped to retain OVA antigen (OVA-Cy5.5) longer at the injection site than unadjuvanted OVA. Overall, archaeosomes of two sizes (30 nm and 100 nm) prepared using microfluidic mixing maintained similar physicochemical properties, adjuvant activity and biodistribution of antigen, in comparison to those compared by the conventional thin film hydration method. This suggests that microfluidics based approaches could be applied to generate consistently sized archaeosomes for use as a vaccine adjuvant.

Inactivated whole hepatitis C virus vaccine employing a licensed adjuvant elicits cross-genotype neutralizing antibodies in mice

BACKGROUND & AIMS

A prophylactic vaccine is required to eliminate HCV as a global public health threat. We developed whole virus inactivated HCV vaccine candidates employing a licensed adjuvant. Further, we investigated the effects of HCV envelope protein modifications (to increase neutralization epitope exposure) on immunogenicity.

METHODS

Whole virus vaccine antigen was produced in Huh7.5 hepatoma cells, processed using a multistep protocol and formulated with adjuvant (MF-59 analogue AddaVax or aluminium hydroxide). We investigated the capacity of IgG purified from the serum of immunized BALB/c mice to neutralize genotype 1-6 HCV (by virus neutralization assays) and to bind homologous envelope proteins (by ELISA). Viruses used for immunizations were (i) HCV5aHi with strain SA13 envelope proteins and modification of an O-linked glycosylation site in E2 (T385P), (ii) HCV5aHi(T385) with reversion of T385P to T385, featuring the original E2 sequence determined in vivo and (iii) HCV5aHi(ΔHVR1) with deletion of HVR1. For these viruses, epitope exposure was investigated using human monoclonal (AR3A and AR4A) and polyclonal (C211 and H06) antibodies in neutralization assays.

RESULTS

Processed HCV5aHi formulated with AddaVax induced antibodies that efficiently bound homologous envelope proteins and broadly neutralized cultured genotype 1-6 HCV, with half maximal inhibitory concentrations of between 14 and 192 μg/ml (mean of 36 μg/ml against the homologous virus). Vaccination with aluminium hydroxide was less immunogenic. Compared to HCV5aHi(T385) with the original E2 sequence, HCV5aHi with a modified glycosylation site and HCV5aHi(ΔHVR1) without HVR1 showed increased neutralization epitope exposure but similar immunogenicity.

CONCLUSION

Using an adjuvant suitable for human use, we developed inactivated whole HCV vaccine candidates that induced broadly neutralizing antibodies, which warrant investigation in further pre-clinical studies.

LAY SUMMARY

A vaccine against hepatitis C virus (HCV) is needed to prevent the estimated 2 million new infections and 400,000 deaths caused by this virus each year. We developed inactivated whole HCV vaccine candidates using adjuvants licensed for human use, which, following immunization of mice, induced antibodies that efficiently neutralized all HCV genotypes with recognized epidemiological importance. HCV variants with modified envelope proteins exhibited similar immunogenicity as the virus with the original envelope proteins.

Adjuvants: Engineering Protective Immune Responses in Human and Veterinary Vaccines

Adjuvants are key components of many vaccines, used to enhance the level and breadth of the immune response to a target antigen, thereby enhancing protection from the associated disease. In recent years, advances in our understanding of the innate and adaptive immune systems have allowed for the development of a number of novel adjuvants with differing mechanisms of action. Herein, we review adjuvants currently approved for human and veterinary use, describing their use and proposed mechanisms of action. In addition, we will discuss additional promising adjuvants currently undergoing preclinical and/or clinical testing.

Immunogenic and efficacious SARS-CoV-2 vaccine based on resistin-trimerized spike antigen SmT1 and SLA archaeosome adjuvant

The huge worldwide demand for vaccines targeting SARS-CoV-2 has necessitated the continued development of novel improved formulations capable of reducing the burden of the COVID-19 pandemic. Herein, we evaluated novel protein subunit vaccine formulations containing a resistin-trimerized spike antigen, SmT1. When combined with sulfated lactosyl archaeol (SLA) archaeosome adjuvant, formulations induced robust antigen-specific humoral and cellular immune responses in mice. Antibodies had strong neutralizing activity, preventing viral spike binding and viral infection. In addition, the formulations were highly efficacious in a hamster challenge model reducing viral load and body weight loss even after a single vaccination. The antigen-specific antibodies generated by our vaccine formulations had stronger neutralizing activity than human convalescent plasma, neutralizing the spike proteins of the B.1.1.7 and B.1.351 variants of concern. As such, our SmT1 antigen along with SLA archaeosome adjuvant comprise a promising platform for the development of efficacious protein subunit vaccine formulations for SARS-CoV-2.

Archaeosomes and Gas Vesicles as Tools for Vaccine Development

Archaea are prokaryotic organisms that were classified as a new domain in 1990. Archaeal cellular components and metabolites have found various applications in the pharmaceutical industry. Some archaeal lipids can be used to produce archaeosomes, a new family of liposomes that exhibit high stability to temperatures, pH and oxidative conditions. Additionally, archaeosomes can be efficient antigen carriers and adjuvants promoting humoral and cellular immune responses. Some archaea produce gas vesicles, which are nanoparticles released by the archaea that increase the buoyancy of the cells and facilitate an upward flotation in water columns. Purified gas vesicles display a great potential for bioengineering, due to their high stability, immunostimulatory properties and uptake across cell membranes. Both archaeosomes and archaeal gas vesicles are attractive tools for the development of novel drug and vaccine carriers to control various diseases. In this review we discuss the current knowledge on production, preparation methods and potential applications of archaeosomes and gas vesicles as carriers for vaccines. We give an overview of the traditional structures of these carriers and their modifications. A comparative analysis of both vaccine delivery systems, including their advantages and limitations of their use, is provided. Gas vesicle- and archaeosome-based vaccines may be powerful next-generation tools for the prevention and treatment of a wide variety of infectious and non-infectious diseases.

The next generation of HCV vaccines: a focus on novel adjuvant development

INTRODUCTION

Considerable efforts have been made to treat and prevent acute and chronic infections caused by the hepatitis C virus (HCV). Current treatments are unable to protect people from reinfection. Hence, there is a need for development of both preventive and therapeutic HCV vaccines. Many vaccine candidates are in development to fight against HCV, but their efficacy has so far proven limited partly due to low immunogenicity.

AREAS COVERED

We explore development of novel and powerful adjuvants to achieve an effective HCV vaccine. The basis for developing strong adjuvants is to understand the innate immunity pathway, which subsequently stimulates humoral and cellular immune responses. We have also investigated immunogenicity of developed adjuvants that have been used in recent studies available in online databases such as PubMed, PMC, ScienceDirect, Google Scholar, etc.

EXPERT OPINION

Adjuvants are used as a part of vaccine formulation to boost vaccine immunogenicity and antigen delivery. Several FDA-approved adjuvants are used in licensed human vaccines. Unfortunately, no adjuvant has yet been proven to boost HCV immune responses to the extent needed for an effective vaccine. One of the promising approaches for developing an effective adjuvant is the combination of various adjuvants to trigger several innate immune responses, leading to activation of adaptive immunity.[Figure: see text].

Natural killer cells contribute to enhanced respiratory disease after oil-in-water emulsion adjuvanted vaccination against respiratory syncytial virus and infection

Respiratory syncytial virus (RSV) infection caused severe acute respiratory disease in children and the elderly. There is no licensed vaccine. It has been a challenging problem to avoid vaccine enhanced respiratory disease in developing a safe and effective RSV vaccine. Here, we investigated the impact of MF59-like oil-in-water emulsion adjuvant Addavax on the vaccine efficacy of inactivated split RSV (sRSV) and the roles of natural killer (NK) cells in enhanced respiratory disease in sRSV vaccinated mice after RSV infection. Addavax-adjuvanted sRSV vaccination induced higher levels of IgG1 isotype antibodies and more effective lung viral clearance upon RSV infection but promoted enhanced respiratory disease of weight loss, pulmonary inflammation, and NK and NK T (NKT) cell infiltrations in the lungs. Antibody treatment depleting NK cells prior to RSV infection resulted in preventing severe weight loss and histopathology, as well as attenuating infiltration of dendritic cell subsets and TNF-α⁺ T cells in the lungs. This study demonstrated the impacts of oil-in-water emulsion adjuvant on sRSV vaccination and the potential roles of NK and NKT cells in protection and respiratory disease after adjuvanted RSV vaccination and infection in a mouse model.

Immuno-Informatics Analysis of Pakistan-Based HCV Subtype-3a for Chimeric Polypeptide Vaccine Design

Hepatitis C virus (HCV) causes chronic and acute hepatitis infections. As there is extreme variability in the HCV genome, no approved HCV vaccine has been available so far. An effective polypeptide vaccine based on the functionally conserved epitopes will be greatly helpful in curing disease. For this purpose, an immuno-informatics study is performed based on the published HCV subtype-3a from Pakistan. First, the virus genome was translated to a polyprotein followed by a subsequent prediction of T-cell epitopes. Non-allergenic, IFN-γ producer, and antigenic epitopes were shortlisted, including 5 HTL epitopes and 4 CTL, which were linked to the final vaccine by GPGPG and AAY linkers, respectively. Beta defensin was included as an adjuvant through the EAAAK linker to improve the immunogenicity of the polypeptide. To ensure its safety and immunogenicity profile, antigenicity, allergenicity, and various physiochemical attributes of the polypeptide were evaluated. Molecular docking was conducted between TLR4 and vaccine to evaluate the binding affinity and molecular interactions. For stability assessment and binding of the vaccine-TLR4 docked complex, molecular dynamics (MD) simulation and MMGBSA binding free-energy analyses were conducted. Finally, the candidate vaccine was cloned in silico to ensure its effectiveness. The current vaccine requires future experimental confirmation to validate its effectiveness. The vaccine construct produced might be useful in providing immune protection against HCV-related infections.

Sulfated Lactosyl Archaeol Archaeosomes Synergize with Poly(I:C) to Enhance the Immunogenicity and Efficacy of a Synthetic Long Peptide-Based Vaccine in a Melanoma Tumor Model

Cancer remains a leading cause of morbidity and mortality worldwide. While novel treatments have improved survival outcomes for some patients, new treatment modalities/platforms are needed to combat a wider variety of tumor types. Cancer vaccines harness the power of the immune system to generate targeted tumor-specific immune responses. Liposomes composed of glycolipids derived from archaea (i.e., archaeosomes) have been shown to be potent adjuvants, inducing robust, long-lasting humoral and cell-mediated immune responses to a variety of antigens. Herein, we evaluated the ability of archaeosomes composed of sulfated lactosyl archaeol (SLA), a semi-synthetic archaeal glycolipid, to enhance the immunogenicity of a synthetic long peptide-based vaccine formulation containing the dominant CD8⁺ T cell epitope, SIINFEKL, from the weakly immunogenic model antigen ovalbumin. One advantage of immunizing with long peptides is the ability to include multiple epitopes, for example, the long peptide antigen was also designed to include the immediately adjacent CD4⁺ epitope, TEWTSSNVMEER. SLA archaeosomes were tested alone or in combination with the toll-like receptor 3 (TLR3) agonist Poly(I:C). Overall, SLA archaeosomes synergized strongly with Poly(I:C) to induce robust antigen-specific CD8⁺ T cell responses, which were highly functional in an in vivo cytolytic assay. Furthermore, immunization with this vaccine formulation suppressed tumor growth and extended mouse survival in a mouse melanoma tumor model. Overall, the combination of SLA archaeosomes and Poly(I:C) appears to be a promising adjuvant system when used along with long peptide-based antigens targeting cancer.

The Synergistic Effects of Sulfated Lactosyl Archaeol Archaeosomes When Combined with Different Adjuvants in a Murine Model

Archaeosomes, composed of sulfated lactosyl archaeol (SLA) glycolipids, have been proven to be an effective vaccine adjuvant in multiple preclinical models of infectious disease or cancer. SLA archaeosomes are a promising adjuvant candidate due to their ability to strongly stimulate both humoral and cytotoxic immune responses when simply admixed with an antigen. In the present study, we evaluated whether the adjuvant effects of SLA archaeosomes could be further enhanced when combined with other adjuvants. SLA archaeosomes were co-administered with five different Toll-like Receptor (TLR) agonists or the saponin QS-21 using ovalbumin as a model antigen in mice. Both humoral and cellular immune responses were greatly enhanced compared to either adjuvant alone when SLA archaeosomes were combined with either the TLR3 agonist poly(I:C) or the TLR9 agonist CpG. These results were also confirmed in a separate study using Hepatitis B surface antigen (HBsAg) and support the further evaluation of these adjuvant combinations.

Archaea Biotechnology

Archaea are a domain of prokaryotic organisms with intriguing physiological characteristics and ecological importance. In Microbial Biotechnology, archaea are historically overshadowed by bacteria and eukaryotes in terms of public awareness, industrial application, and scientific studies, although their biochemical and physiological properties show a vast potential for a wide range of biotechnological applications. Today, the majority of microbial cell factories utilized for the production of value-added and high value compounds on an industrial scale are bacterial, fungal or algae based. Nevertheless, archaea are becoming ever more relevant for biotechnology as their cultivation and genetic systems improve. Some of the main advantages of archaeal cell factories are the ability to cultivate many of these often extremophilic organisms under non-sterile conditions, and to utilize inexpensive feedstocks often toxic to other microorganisms, thus drastically reducing cultivation costs. Currently, the only commercially available products of archaeal cell factories are bacterioruberin, squalene, bacteriorhodopsin and diether-/tetraether-lipids, all of which are produced utilizing halophiles. Other archaeal products, such as carotenoids and biohydrogen, as well as polyhydroxyalkanoates and methane are in early to advanced development stages, respectively. The aim of this review is to provide an overview of the current state of Archaea Biotechnology by describing the actual state of research and development as well as the industrial utilization of archaeal cell factories, their role and their potential in the future of sustainable bioprocessing, and to illustrate their physiological and biotechnological potential.

Adjuvanted Schistosoma mansoni-Cathepsin B With Sulfated Lactosyl Archaeol Archaeosomes or AddaVax™ Provides Protection in a Pre-Clinical Schistosomiasis Model

Schistosomiasis threatens 800 million people worldwide. Chronic pathology manifests as hepatosplenomegaly, and intestinal schistosomiasis caused by Schistosoma mansoni can lead to liver fibrosis, cirrhosis, and blood in the stool. To assist the only FDA-approved drug, praziquantel, in parasite elimination, the development of a vaccine would be of high value. S. mansoni Cathepsin B (SmCB) is a well-documented vaccine target for intestinal schistosomiasis. Herein, we test the increased efficacy and immunogenicity of SmCB when combined with sulfated lactosyl archaeol (SLA) archaeosomes or AddaVax™ (a squalene based oil-in-water emulsion). Both vaccine formulations resulted in robust humoral and cell mediated immune responses. Impressively, both formulations were able to reduce parasite burden greater than 40% (WHO standard), with AddaVax™ reaching 86.8%. Additionally, SmCB with both adjuvants were able to reduce granuloma size and the amount of larval parasite hatched from feces, which would reduce transmission. Our data support SmCB as a target for S. mansoni vaccination; especially when used in an adjuvanted formulation.

Mechanistic insight into the induction of cellular immune responses by encapsulated and admixed archaeosome-based vaccine formulations

Archaeosomes are liposomes formulated using total polar lipids (TPLs) or semi-synthetic glycolipids derived from archaea. Conventional archaeosomes with entrapped antigen exhibit robust adjuvant activity as demonstrated by increased antigen-specific humoral and cell-mediated responses and enhanced protective immunity in various murine infection and cancer models. However, antigen entrapment efficiency can vary greatly resulting in antigen loss during formulation and variable antigen:lipid ratios. In order to circumvent this, we recently developed an admixed archaeosome formulation composed of a single semi-synthetic archaeal lipid (SLA, sulfated lactosylarchaeol) which can induce similarly robust adjuvant activity as an encapsulated formulation. Herein, we evaluate and compare the mechanisms involved in the induction of early innate and antigen-specific responses by both admixed (Adm) and encapsulated (Enc) SLA archaeosomes. We demonstrate that both archaeosome formulations result in increased immune cell infiltration, enhanced antigen retention at injection site and increased antigen uptake by antigen-presenting cells and other immune cell types, including neutrophils and monocytes following intramuscular injection to mice using ovalbumin as a model antigen. In vitro studies demonstrate SLA in either formulation is preferentially taken up by macrophages. Although the encapsulated formulation was better able to induce antigen-specific CD8⁺ T cell activation by dendritic cells in vitro, both encapsulated and admixed formulations gave equivalently enhanced protection from tumor challenge when tested in vivo using a B16-OVA melanoma model. Despite some differences in the immunostimulatory profile relative to the SLA (Enc) formulation, SLA (Adm) induces strong in vivo immunogenicity and efficacy, while offering an ease of formulation.

Hepatitis C virus vaccine design: focus on the humoral immune response

Despite the recent development of safe and highly effective direct-acting antivirals, hepatitis C virus (HCV) infection remains a significant health problem. In 2016, the World Health Organization set out to reduce the rate of new HCV infections by 90% by 2030. Still, global control of the virus does not seem to be achievable in the absence of an effective vaccine. Current approaches to the development of a vaccine against HCV include the production of recombinant proteins, synthetic peptides, DNA vaccines, virus-like particles, and viral vectors expressing various antigens. In this review, we focus on the development of vaccines targeting the humoral immune response against HCV based on the cumulative evidence supporting the important role of neutralizing antibodies in protection against HCV infection. The main targets of HCV-specific neutralizing antibodies are the glycoproteins E1 and E2. Recent advances in the knowledge of HCV glycoprotein structure and their epitopes, as well as the possibility of getting detailed information on the human antibody repertoire generated by the infection, will allow rational structure-based antigen design to target specific germline antibodies. Although obtaining a vaccine capable of inducing sterilizing immunity will be a difficult task, a vaccine that prevents chronic hepatitis C infections, a more realistic goal in the short term, would have a considerable health impact.

Innate Immune Response against Hepatitis C Virus: Targets for Vaccine Adjuvants

Despite successful treatments, hepatitis C virus (HCV) infections continue to be a significant world health problem. High treatment costs, the high number of undiagnosed individuals, and the difficulty to access to treatment, particularly in marginalized susceptible populations, make it improbable to achieve the global control of the virus in the absence of an effective preventive vaccine. Current vaccine development is mostly focused on weakly immunogenic subunits, such as surface glycoproteins or non-structural proteins, in the case of HCV. Adjuvants are critical components of vaccine formulations that increase immunogenic performance. As we learn more information about how adjuvants work, it is becoming clear that proper stimulation of innate immunity is crucial to achieving a successful immunization. Several hepatic cell types participate in the early innate immune response and the subsequent inflammation and activation of the adaptive response, principally hepatocytes, and antigen-presenting cells (Kupffer cells, and dendritic cells). Innate pattern recognition receptors on these cells, mainly toll-like receptors, are targets for new promising adjuvants. Moreover, complex adjuvants that stimulate different components of the innate immunity are showing encouraging results and are being incorporated in current vaccines. Recent studies on HCV-vaccine adjuvants have shown that the induction of a strong T- and B-cell immune response might be enhanced by choosing the right adjuvant.