Use of a dialyzable short-chain phospholipid for efficient solubilization and reconstitution of influenza virus envelopes

Immunological profile of mice immunized with a polyvalent virosome-based influenza vaccine

BACKGROUND

Influenza A virus (IAV) causes respiratory disease in pigs and is a major concern for public health. Vaccination of pigs is the most successful measure to mitigate the impact of the disease in the herds. Influenza-based virosome is an effective immunomodulating carrier that replicates the natural antigen presentation pathway and has tolerability profile due to their purity and biocompatibility.

METHODS

This study aimed to develop a polyvalent virosome influenza vaccine containing the hemagglutinin and neuraminidase proteins derived from the swine IAVs (swIAVs) H1N1, H1N2 and H3N2 subtypes, and to investigate its effectiveness in mice as a potential vaccine for swine. Mice were immunized with two vaccine doses (1 and 15 days), intramuscularly and intranasally. At 21 days and eight months later after the second vaccine dose, mice were euthanized. The humoral and cellular immune responses in mice vaccinated intranasally or intramuscularly with a polyvalent influenza virosomal vaccine were investigated.

RESULTS

Only intramuscular vaccination induced high hemagglutination inhibition (HI) titers. Seroconversion and seroprotection (> 4-fold rise in HI antibody titers, reaching a titer of ≥ 1:40) were achieved in 80% of mice (intramuscularly vaccinated group) at 21 days after booster immunization. Virus-neutralizing antibody titers against IAV were detected at 8 months after vaccination, indicating long-lasting immunity. Overall, mice immunized with the virosome displayed greater ability for B, effector-T and memory-T cells from the spleen to respond to H1N1, H1N2 and H3N2 antigens.

CONCLUSIONS

All findings showed an efficient immune response against IAVs in mice vaccinated with a polyvalent virosome-based influenza vaccine.

Enhanced HPV16 E6/E7+ tumor eradication via induction of tumor-specific T cells by therapeutic vaccination with virosomes presenting synthetic long peptides

Therapeutic cancer vaccines trigger CD4 + and CD8 + T cell responses capable of established tumor eradication. Current platforms include DNA, mRNA and synthetic long peptide (SLP) vaccines, all aiming at robust T cell responses. SLPs linked to the Amplivant® adjuvant (Amplivant-SLP) have shown effective delivery to dendritic cells, resulting in improved immunogenicity in mice. We have now tested virosomes as a delivery vehicle for SLPs. Virosomes are nanoparticles made from influenza virus membranes and have been used as vaccines for a variety of antigens. Amplivant-SLP virosomes induced the expansion of more antigen-specific CD8 + T memory cells in ex vivo experiments with human PBMCs than Amplivant-SLP conjugates alone. The immune response could be further improved by including the adjuvants QS-21 and 3D-PHAD in the virosomal membrane. In these experiments, the SLPs were anchored in the membrane through the hydrophobic Amplivant adjuvant. In a therapeutic mouse model of HPV16 E6/E7+ cancer, mice were vaccinated with virosomes loaded with either Amplivant-conjugated SLPs or lipid-coupled SLPs. Vaccination with both types of virosomes significantly improved the control of tumor outgrowth, leading to elimination of the tumors in about half the animals for the best combinations of adjuvants and to their survival beyond 100 days.

Comparison of Virosome vs. Liposome as drug delivery vehicle using HepG2 and CaCo2 cell lines

AIM

The present work involves encapsulation of herbal drug nanocurcumin into the virosomes and compared with a liposome in terms of their in vitro anti-proliferative, anti-inflammatory, and anti-migratory efficacy.

METHODS

The anti-proliferative, anti-inflammatory, and anti-migratory efficacy of virosome and liposome were compared in HepG2 and CaCo2 cells by using MTT, Nitric oxide scavenging, and Wound healing assay, respectively.

RESULTS

Size of the optimised NC-Virosome and NC-Liposome was 70.06 ± 1.63 and 265.80 ± 1.64 nm, respectively. The prepared NC-Virosome can be stored at -4 °C up to six months. The drug encapsulation efficiency of NC-Virosome and NC-Liposome was found to be 84.66 ± 1.67 and 62.15 ± 1.75% (w/w). The evaluated minimum inhibitory concentration (IC50 value) for NC-Virosome was 102.7 μg/ml and 108.1 μg/ml, while NC-Liposome showed 129.2 μg/ml and 160.1 μg/ml for HepG2 and CaCo2 cells, respectively. Morphological examination depicts detachment of the cells from substratum after exposure to NC-Virosome for 48 h.

CONCLUSION

The prepared NC-Virosome provides remarkable in vitro efficacy in both the cell lines with site-specific drug-targeting potential as compared to the liposome, results proved its potential as a drug delivery vehicle for future therapy with reduced toxicity.

Respiratory syncytial virus subunit vaccines based on the viral envelope glycoproteins intended for pregnant women and the elderly

Introduction: Respiratory syncytial virus (RSV) causes high morbidity and mortality rates among infants, young children, and the elderly worldwide. Unfortunately, a safe and effective vaccine is still unavailable. In 1966, a formalin-inactivated RSV vaccine failed and resulted in the death of two young children. This failure shifted research toward the development of subunit-based vaccines for pregnant women (to passively vaccinate infants) and the elderly. Among these subunit-based vaccines, the viral envelope glycoproteins show great potential as antigens. Areas covered: In this review, progress in the development of safe and effective subunit RSV vaccines based on the viral envelope glycoproteins and intended for pregnant women and the elderly, are reviewed and discussed. Studies published in the period 2012-2018 were included. Expert opinion: Researchers are close to bringing safe and effective subunit-based RSV vaccines to the market using the viral envelope glycoproteins as antigens. However, it remains a major challenge to elicit protective immunity, with a formulation that has sufficient (storage) stability. These issues may be overcome by using the RSV fusion protein in its pre-fusion conformation, and by formulating this protein as a dry powder. It may further be convenient to administer this powder via the pulmonary route.

Inactivation of human and avian influenza viruses by potassium oleate of natural soap component through exothermic interaction

An influenza epidemic is still a problem despite the development of vaccines and anti-influenza drugs. Preventive measures such as handwashing are fundamental and important for counteracting influenza virus infection. In this study, we clarified the anti-influenza virus effects of surfactants, which are the main components of hand soaps for hand washing: potassium oleate (C18:1), sodium laureth sulfate (LES) and sodium lauryl sulfate (SDS). For a human influenza virus strain (H3N2), C18:1 reduced the infectivity by 4 logs or more, whereas LES and SDS reduced the infectivity by 1 log or less. Similar results were obtained when an avian influenza virus strain (H5N3) was used. The interaction between the surfactant and virus was then investigated by isothermal titration calorimetry. The LES-virus system showed a positive value of enthalpy changes (ΔH), meaning an exothermic interaction that indicated a hydrophobic interaction. In contrast, both the C18:1-virus system and the SDS-virus system showed negative values of ΔH, meaning an endothermic interaction that indicated an electrical interaction. The ΔH value of the C18:1-virus system was much higher than that of the SDS-virus system. A mixture of C18:1 and HA proteins similarly showed negative values of ΔH. These results indicate that influenza virus inactivation by a hydrophobic interaction of a surfactant with the viral envelope is insufficient to prevent infection, whereas inactivation by an electrical interaction of a surfactant with HA proteins is sufficient to prevent influenza virus infection.

Development of a Virosomal RSV Vaccine Containing 3D-PHAD® Adjuvant: Formulation, Composition, and Long-Term Stability

PURPOSE

Characterization of virosomes, in late stage preclinical development as vaccines for Respiratory Syncytial Virus (RSV), with a membrane-incorporated synthetic monophosphoryl lipid A, 3D-PHAD® adjuvant.

METHODS

Virosomes were initially formed by contacting a lipid film containing 3D-PHAD® with viral membranes solubilized with the short chain phospholipid DCPC, followed by dialysis, later by adding solubilized 3D-PHAD to viral membranes, or to preformed virosomes from DMSO.

RESULTS

Virosomes formed from lipid films contained the membrane glycoproteins G and F, at similar F to G ratios but lower concentrations than in virus, and the added lipids, but only a fraction of the 3D-PHAD®. By single particle tracking (SPT), the virosome size distribution resembled that seen by cryo-electron microscopy, but dynamic light scattering showed much larger particles. These differences were caused by small virosome aggregates. Measured by SPT, virosomes were stable for 300 days. 3DPHAD ® incorporation in virosomes could be enhanced by providing the adjuvant from DCPC solubilized stock, but also by adding DMSO dissolved adjuvant to pre-formed virosomes. Virosomes with 0.1 mg/mg of 3D-PHAD®/viral protein from DMSO induced antibody titers similar to those by virosomes containing 0.2 mg/mg of DCPC-solubilized 3D-PHAD®.

CONCLUSIONS

Stable 3D-PHAD® adjuvanted RSV virosomes can be formulated.

Respiratory syncytial virus: an overview of infection biology and vaccination strategies

Respiratory syncytial virus (RSV) is the foremost cause of lower respiratory tract infections, especially in infants and young children. To date, there is no licensed vaccine available for RSV. Only option to restrain RSV is a prophylactic treatment in the form of monoclonal antibody (palivizumab). However, it is quite expensive and used in few patients with co-morbidities. In ongoing research, virologists contemplate about various vaccine candidates to control RSV infection. This review will help in understating the RSV pathobiology and encompass the advancement on various vaccine candidates that would lead to reduce the incidence, mortality and morbidity. Furthermore, it will lighten up the different avenues which might be useful for the development of novel vaccination approaches.

Enzymatic methods for choline-containing water soluble phospholipids based on fluorescence of choline oxidase: Application to lyso-PAF

In this paper we present methods to determine water soluble phospholipids containing choline (wCh-PL). The analytes were hydrolyzed by the enzyme phospholipase D and the choline formed was oxidized by the enzyme Choline Oxidase (ChOx); the fluorescence changes of the ChOx are followed during the enzymatic reaction, avoiding the necessity of an indicating step. Both reactions (hydrolysis and oxidation) can be combined in two different ways: 1) a two-step process (TSP) in which the hydrolysis reaction takes place during an incubation time and then the oxidation reaction is carried out, the analytical signal being provided by the intrinsic fluorescence of ChOx due to tryptophan; 2) a one-step process (OSP) in which both enzymatic reactions are carried out simultaneously in the same test; in this case the analytical signal is provided by the ChOx extrinsic fluorescence due to a fluorescent probe (Ru (II) chelate) linked to the enzyme (ChOx-RuC). The analytical capabilities of these methods were studied using 1,2-dioctanoyl-sn-glycero-3-phosphocholine (C₈PC), a water soluble short alkyl chain Ch-PL as a substrate, and 1-O-hexadecyl-sn-glyceryl-3-phosphorylcholine (lyso-PAF). The analytical features of merit for both analytes using both methods were obtained. The TSP gave a 10-fold sensitivity and lower quantification limit (1.0*10^-5 M for lyso-PAF), but OSP reduced the determination time and permitted to use the same enzyme aliquot for several measurements. Both methods gave similar precision (RSD 7%, n = 5). The TSP was applied to the determination of C₈PC and lyso-PAF in spiked synthetic serum matrix using the standard addition method. The application of this methodology to PLD activity determination is also discussed.

A novel chimeric influenza virosome containing Vesicular stomatitis G protein as a more efficient gene delivery system

OBJECTIVES

To enhance the efficiency of influenza virosome-mediated gene delivery by engineering this virosome.

RESULTS

A novel chimeric influenza virosome was constructed containing the glycoprotein of Vesicular stomatitis virus (VSV-G), along with its own hemagglutinin protein. To optimize the transfection efficiency of both chimeric and influenza cationic virosomes, HEK cells were transfected with plasmid DNA and virosomes and the transfection efficiency was assessed by FACS analysis. The chimeric virosome was significantly more efficient in mediating transfection for all amounts of DNA and virosomes compared to the influenza virosome.

CONCLUSIONS

Chimeric influenza virosome, including VSV-G, is superior to the conventional influenza virosome for gene delivery.

Introduction of cationic virosome derived from vesicular stomatitis virus as a novel gene delivery system for sf9 cells

Insect-derived cell lines are used extensively to produce recombinant proteins because they are capable of performing a range of post-translational modifications. Due to their significance in biotechnological applications, various methods have been developed to transfect them. In this study, we introduce a virosome constructed from vesicular stomatitis virus (VSV) as a new delivery system for sf9 cells. We labeled these VSV virosomes by fluorescent probe Rhodamine B chloride (R18). By fluorescence microscope observation and conducting a fusion assay, we confirmed the uptake of VSV virosomes via endocytosis by sf9 cells and their fusion with the endosomal membrane. Moreover, we incubated cationic VSV virosomes with a GFP-expressing bacmid and transfected sf9 cells, after 24 h some cells expressed GFP indicating the ability of VSV virosomes to deliver heterologous DNA to these cells. This is the first report of a virosome-based delivery system introduced for an insect cell line.

An H1-H3 chimeric influenza virosome confers complete protection against lethal challenge with PR8 (H1N1) and X47 (H3N2) viruses in mice

Annual health threats and economic damages caused by influenza virus are still a main concern of the World Health Organization and other health departments all over the world. An influenza virosome is a highly efficient immunomodulating carrier mimicking the natural antigen presentation pathway and has shown an excellent tolerability profile due to its biocompatibility and purity. The major purpose of this study was to construct a new chimeric virosome influenza vaccine containing hemagglutinin (HA) and neuraminidase (NA) proteins derived from the A/PR/8/1934 (H1N1) (PR8) and A/X/47 (H3N2) (X47) viruses, and to evaluate its efficacy as a vaccine candidate in mice. A single intramuscular vaccination with the chimeric virosomes provided complete protection against lethal challenge with the PR8 and X47 viruses. The chimeric virosomes induced high IgG antibody responses as well as hemagglutination inhibition (HAI) titers. HAI titers following the chimeric virosome vaccination were at the same level as the whole inactivated influenza vaccine. Mice immunized with the chimeric virosomes displayed considerably less weight loss and exhibited significantly reduced viral load in their lungs compared with the controls. The chimeric virosomes can be used as an innovative vaccine formulation to confer protection against a broad range of influenza viruses.

Solid bioneedle-delivered influenza vaccines are highly thermostable and induce both humoral and cellular immune responses

The potential of bioneedles to deliver influenza vaccines was investigated. Four influenza vaccine formulations were screened to determine the optimal formulation for use with bioneedles. The stability of the formulations after freeze-drying was checked to predict the stability of the influenza vaccines in the bioneedles. Subunit, split, virosomal and whole inactivated influenza (WIV) vaccine were formulated and lyophilized in bioneedles, and subsequently administered to C57BL/6 mice. Humoral and cellular immune responses were assessed after vaccination. The thermostability of lyophilized vaccines was determined after one-month storage at elevated temperatures. Bioneedle influenza vaccines induced HI titers that are comparable to those induced by intramuscular WIV vaccination. Delivery by bioneedles did not alter the type of immune response induced by the influenza vaccines. Stability studies showed that lyophilized influenza vaccines have superior thermostability compared to conventional liquid vaccines, and remained stable after one-month storage at 60°C. Influenza vaccines delivered by bioneedles are a viable alternative to conventional liquid influenza vaccines. WIV was determined to be the most potent vaccine formulation for administration by bioneedles. Lyophilized influenza vaccines in bioneedles are independent of a cold-chain, due to their increased thermostability, which makes distribution and stockpiling easier.

Properties and prospects of adjuvants in influenza vaccination - messy precipitates or blessed opportunities?

Influenza is a major challenge to healthcare systems world-wide. While prophylactic vaccination is largely efficient, long-lasting immunity has not been achieved in immunized populations, at least in part due to the challenges arising from the antigen variation between strains of influenza A virus as a consequence of genetic drift and shift. From progress in our understanding of the immune system, the mode-of-action of vaccines can be divided into the stimulation of the adaptive system through inclusion of appropriate vaccine antigens and of the innate immune system by the addition of adjuvant to the vaccine formulation. A shared property of many vaccine adjuvants is found in their nature of water-insoluble precipitates, for instance the particulate material made from aluminum salts. Previously, it was thought that embedding of vaccine antigens in these materials provided a "depot" of antigens enabling a long exposure of the immune system to the antigen. However, more recent work points to a role of particulate adjuvants in stimulating cellular parts of the innate immune system. Here, we briefly outline the infectious medicine and immune biology of influenza virus infection and procedures to provide sufficient and stably available amounts of vaccine antigen. This is followed by presentation of the many roles of adjuvants, which involve humoral factors of innate immunity, notably complement. In a perspective of the ultrastructural properties of these humoral factors, it becomes possible to rationalize why these insoluble precipitates or emulsions are such a provocation of the immune system. We propose that the biophysics of particulate material may hold opportunities that could aid the development of more efficient influenza vaccines.

Cellular Delivery of siRNA Mediated by Fusion-Active Virosomes

RNA interference is expected to have considerable potential for the development of novel specific therapeutic strategies. However, successful application of RNA interference in vivo will depend on the availability of efficient delivery systems for the introduction of small-interfering RNA (siRNA) into the appropriate target cells. This paper focuses on the use of reconstituted viral envelopes ("virosomes"), derived from influenza virus, as a carrier system for cellular delivery of siRNA. Complexed to cationic lipid, siRNA molecules could be efficiently encapsulated in influenza virosomes. Delivery to cultured cells was assessed on the basis of flow cytometry analysis using fluorescently labeled siRNA. Virosome-encapsulated siRNA directed against Green Fluorescent Protein (GFP) inhibited GFP fluorescence in cells transfected with a plasmid encoding GFP or in cells constitutively expressing GFP. Delivery of siRNA was dependent on the low-pH-induced membrane fusion activity of the virosomal hemagglutinin, supporting the notion that virosomes introduce their encapsulated siRNA into the cell cytosol through fusion of the virosomal membrane with the limiting membrane of cellular endosomes, after internalization of the virosomes by receptor-mediated endocytosis. It is concluded that virosomes represent a promising carrier system for cellular delivery of siRNA in vitro as well as in vivo.

Development of stable influenza vaccine powder formulations: challenges and possibilities

Influenza vaccination represents the cornerstone of influenza prevention. However, today all influenza vaccines are formulated as liquids that are unstable at ambient temperatures and have to be stored and distributed under refrigeration. In order to stabilize influenza vaccines, they can be brought into the dry state using suitable excipients, stabilizers and drying processes. The resulting stable influenza vaccine powder is independent of cold-chain facilities. This can be attractive for the integration of the vaccine logistics with general drug distribution in Western as well as developing countries. In addition, a stockpile of stable vaccine formulations of potential vaccines against pandemic viruses can provide an immediate availability and simple distribution of vaccine in a pandemic outbreak. Finally, in the development of new needle-free dosage forms, dry and stable influenza vaccine powder formulations can facilitate new or improved targeting strategies for the vaccine compound. This review represents the current status of dry stable inactivated influenza vaccine development. Attention is given to the different influenza vaccine types (i.e. whole inactivated virus, split, subunit or virosomal vaccine), the rationale and need for stabilized influenza vaccines, drying methods by which influenza vaccines can be stabilized (i.e. lyophilization, spray drying, spray-freeze drying, vacuum drying or supercritical fluid drying), the current status of dry influenza vaccine development and the challenges for ultimate market introduction of a stable and effective dry-powder influenza vaccine.

Inulin sugar glasses preserve the structural integrity and biological activity of influenza virosomes during freeze-drying and storage

Influenza virosomes are reconstituted influenza virus envelopes that may be used as vaccines or as carrier systems for cellular delivery of therapeutic molecules. Here we present a procedure to generate influenza virosomes as a stable dry-powder formulation by freeze-drying (lyophilization) using an amorphous inulin matrix as a stabilizer. In the presence of inulin the structural integrity and fusogenic activity of virosomes were fully preserved during freeze-drying. For example, the immunological properties of the virosomes, i.e. the HA potency in vitro and the immunogenic potential in vivo, were maintained during lyophilization in the presence of inulin. In addition, compared to virosomes dispersed in buffer, inulin-formulated virosomes showed substantially prolonged preservation of the HA potency upon storage. Also the capacity of virosomes to mediate cellular delivery of macromolecules was maintained during lyophilization in the presence of inulin and upon subsequent storage. Specifically, when dispersed in buffer, virosomes with encapsulated plasmid DNA lost their transfection activity completely within 6 weeks, whereas their transfection activity was fully preserved for at least 12 weeks after incorporation in an inulin matrix. Thus, in the presence of inulin as a stabilizing agent, the shelf-life of influenza virosomes with and without encapsulated macromolecules was considerably prolonged. Formulation of influenza virosomes as a dry-powder is advantageous for storage and transport and offers the possibility to develop needle-free dosage forms, e.g. for oral, nasal, pulmonal, or dermal delivery.

Cellular gene transfer mediated by influenza virosomes with encapsulated plasmid DNA

Reconstituted influenza virosomes (virus membrane envelopes) have been used previously to deliver pDNA (plasmid DNA) bound to their external surface to a variety of target cells. Although high transfection efficiencies can be obtained with these complexes in vitro, the virosome-associated DNA is readily accessible to nucleases and could therefore be prone to rapid degradation under in vivo conditions. In the present study, we show a new method for the production of DNA-virosomes resulting in complete protection of the DNA from nucleases. This method relies on the use of the short-chain phospholipid DCPC (dicaproylphosphatidylcholine) for solubilization of the viral membrane. The solubilized viral membrane components are mixed with pDNA and cationic lipid. Reconstitution of the viral envelopes and simultaneous encapsulation of pDNA is achieved by removal of the DCPC from the mixture through dialysis. Analysis by linear sucrose density-gradient centrifugation revealed that protein, phospholipid and pDNA physically associated to particles, which appeared as vesicles with spike proteins inserted in their membranes when analysed by electron microscopy. The DNA-virosomes retained the membrane fusion properties of the native influenza virus. The virosome-associated pDNA was completely protected from degradation by nucleases, providing evidence for the DNA being highly condensed and encapsulated in the lumen of the virosomes. DNA-virosomes, containing reporter gene constructs, transfected a variety of cell lines, with efficiencies approaching 90%. Transfection was completely dependent on the fusogenic properties of the viral spike protein haemagglutinin. Thus, DNA-virosomes prepared by the new procedure are highly efficient vehicles for DNA delivery, offering the advantage of complete DNA protection, which is especially important for future in vivo applications.