Development of a stabilizer for lyophilization of an attenuated duck viral hepatitis vaccine

Development of Robust Freeze-Drying Process for Long-Term Stability of rVSV-SARS-CoV-2 Vaccine

The thermostability of vaccines, particularly enveloped viral vectored vaccines, remains a challenge to their delivery wherever needed. The freeze-drying of viral vectored vaccines is a promising approach but remains challenging due to the water removal process from the outer and inner parts of the virus. In the case of enveloped viruses, freeze-drying induces increased stress on the envelope, which often leads to the inactivation of the virus. In this study, we designed a method to freeze-dry a recombinant vesicular stomatitis virus (VSV) expressing the SARS-CoV-2 spike glycoprotein. Since the envelope of VSV is composed of 50% lipids and 50% protein, the formulation study focused on both the protein and lipid portions of the vector. Formulations were prepared primarily using sucrose, trehalose, and sorbitol as cryoprotectants; mannitol as a lyoprotectant; and histidine as a buffer. Initially, the infectivity of rVSV-SARS-CoV-2 and the cake stability were investigated at different final moisture content levels. High recovery of the infectious viral titer (~0.5 to 1 log loss) was found at 3-6% moisture content, with no deterioration in the freeze-dried cakes. To further minimize infectious viral titer loss, the composition and concentration of the excipients were studied. An increase from 5 to 10% in both the cryoprotectants and lyoprotectant, together with the addition of 0.5% gelatin, resulted in the improved recovery of the infectious virus titer and stable cake formation. Moreover, the secondary drying temperature of the freeze-drying process showed a significant impact on the infectivity of rVSV-SARS-CoV-2. The infectivity of the vector declined drastically when the temperature was raised above 20 °C. Throughout a long-term stability study, formulations containing 10% sugar (sucrose/trehalose), 10% mannitol, 0.5% gelatin, and 10 mM histidine showed satisfactory stability for six months at 2-8 °C. The development of this freeze-drying process and the optimized formulation minimize the need for a costly cold chain distribution system.

Protective Efficacy of Lyophilized Vesicular Stomatitis Virus-Based Vaccines in Animal Model

We evaluated the in vitro effects of lyophilization for 2 vesicular stomatitis virus-based vaccines by using 3 stabilizing formulations and demonstrated protective immunity of lyophilized/reconstituted vaccine in guinea pigs. Lyophilization increased stability of the vaccines, but specific vesicular stomatitis virus-based vaccines will each require extensive analysis to optimize stabilizing formulations.

Screening and Stability Evaluation of Freeze-Dried Protective Agents for a Live Recombinant Pseudorabies Virus Vaccine

Infection of pigs with the pseudorabies virus (PRV) causes significant economic losses in the pig industry. Immunization with live vaccines is a crucial aspect in the prevention of pseudorabies in swine. The TK/gE/gI/11k/28k deleted pseudorabies vaccine is a promising alternative for the eradication of epidemic pseudorabies mutant strains. This study optimized the lyophilization of a heat-resistant PRV vaccine to enhance the quality of a live vaccine against the recombinant PRV rHN1201TK-/gE-/gI-/11k-/28k-. The A4 freeze-dried protective formulation against PRV was developed by comparing the reduction in virus titer after lyophilization and after seven days of storage at 37 °C. The formulation contains 1% gelatin, 5% trehalose, 0.5% poly-vinylpyrimidine (PVP), 0.5% thiourea, and 1% sorbitol. The A4 freeze-dried vaccine demonstrated superior protection and thermal stability. It experienced a freeze-dried loss of 0.31 Lg post-freeze-drying and a heat loss of 0.42 Lg after being stored at a temperature of 37 °C for 7 consecutive days. The A4 freeze-dried vaccine was characterized through XRD, FTIR, and SEM analyses, which showed that it possessed an amorphous structure with a consistent porous interior. The trehalose component of the vaccine formed stable hydrogen bonds with the virus. Long-term and accelerated stability studies were also conducted. The A4 vaccine maintained viral titer losses of less than 1.0 Lg when exposed to 25 °C for 90 days, 37 °C for 28 days, and 45 °C for 7 days. The A4 vaccine had a titer loss of 0.3 Lg after storage at 2-8 °C for 24 months, and a predicted shelf life of 6.61 years at 2-8 °C using the Arrhenius equation. The A4 freeze-dried vaccine elicited no side effects when used to immunize piglets and produced specific antibodies. This study provides theoretical references and technical support to improve the thermal stability of recombinant PRV rHN1201TK-/gE-/gI-/11k-/28k- vaccines.

Current status and future direction of duck hepatitis A virus vaccines

Duck viral hepatitis (DVH), mainly caused by duck hepatitis A virus (DHAV), is a highly fatal and rapidly spreading infectious disease of young ducklings that seriously jeopardizes the duck industry worldwide. DHAV type 1 (DHAV-1) is the main genotype responsible for disease outbreaks since 1945, and the disease situation is complicated by the emergence and dissemination of a novel genotype (DHAV-3) in some countries in Asia and Africa. Live attenuated DHAV vaccines are widely used to induce a considerable degree of protection in ducklings. Breeder ducks are immunized with inactivated or/and live DHAV vaccines to achieve satisfactory levels of passive immunity in progeny. In addition, novel characteristics of virus transmission, pathogenicity and pathogenesis of DHAV were recently characterized, necessitating the development of new vaccines and effective vaccination programmes against DVH. Therefore, a systematic dissection of the profiles, strengths and shortcomings of the available DHAV vaccines is essential. Moreover, to further increase the efficiency of vaccine production and administration, the development of next-generation DHAV vaccines using cutting-edge technologies is also required. In this review, based on a comprehensive summary of the research advances in the epidemiology, pathogenicity, and genomic features of DHAV, we focus on reviewing and analysing the features of the commercial and experimental DHAV vaccines. We also propose perspectives for disease control based on the specific disease situations in different countries. This review provides essential information for vaccine development and disease control of DVH.

Defective Interfering Particles with Broad-Acting Antiviral Activity for Dengue, Zika, Yellow Fever, Respiratory Syncytial and SARS-CoV-2 Virus Infection

More than 100 arboviruses, almost all of which have an RNA genome, cause disease in humans. RNA viruses are causing unprecedented health system challenges worldwide, many with little or no specific therapies or vaccines available. Certain species of mosquito can carry dengue virus (DENV), Zika virus (ZIKV) and yellow fever virus (YFV), where co-infection of these viruses has occurred. Here, we found that purified synthetic defective interfering particles (DIPs) derived from DENV type 2 (DENV-2) strongly suppressed replication of the aforementioned viruses, respiratory syncytial virus (RSV) and also the novel emerging virus SARS-CoV-2 in human cells. DENV DIPs produced in bioreactors, purified by column chromatography, and concentrated are virus-like particles that are about half the diameter of a typical DENV particle, but with similar ratios of the viral structural proteins envelope and capsid. Overall, DIP-treated cells inhibited DENV, ZIKV, YFV, RSV, and SARS-CoV-2 by at least 98% by mechanisms which included interferon (IFN)-dependent cellular antiviral responses. IMPORTANCE DIPs are spontaneously derived virus mutants with deletions in genes that block viral replication. DIPs play important roles in modulation of viral disease, innate immune responses, virus persistence and virus evolution. Here, we investigated the antiviral activity of highly purified synthetic DIPs derived from DENV, which were produced in bioreactors. DENV DIPs purified by column chromatography strongly inhibited five different RNA viruses, including DENV, ZIKV, YFV, RSV, and SARS-CoV-2 in human cells. DENV DIPs inhibited virus replication via delivery of a small, noninfectious viral RNA that activated cellular innate immunity, resulting in robust type 1 interferon responses. The work here presents a pathway for DIP production which is adaptable to Good Manufacturing Practice, so that their preclinical testing should be suitable for evaluation in subjects.

Effects of Autoclaving and Freeze-Drying on Physicochemical Properties of Plectranthus esculentus Starch Derivatives

The goal of this research was to assess the effects of autoclaving followed by freeze-drying on acetylated xerogel (AXS) and carboxymethylated (CMS) derivatives of Plectranthus esculentus starch as potential vaccine stabilizers. Starch extracted from tubers of P. esculentus were modified by single (carboxymethylation) and dual (acetylation followed by xerogel formation) methods. The derivatives were formulated into vaccine stabilizer suspensions, autoclaved, and freeze-dried without additives or antigen. The derivatives and freeze-dried products were assessed by physical appearance, titration, moisture content (MC), TGA, DSC, XRD, SEM, and FTIR analyses. The degrees of substitution (DS) of the CMS and AXS derivatives were 0.345 and 0.033, respectively. Modification significantly reduced the MC of the derivatives. Freeze-dried AXS (FAXS) had lower MC than freeze-dried CMS (FCMS). The lower degree of hydrophilicity/MC of AXS and FAXS was confirmed by TGA and FTIR band intensities and shifts. Reduction in DSC water desorption/evaporation enthalpies (ΔH) from - 1168.8 mJ (NaS) to - 407.48 mJ (AXS) confirmed the influence of modification on moisture. FTIR confirmed acetylation and carboxymethylation of the derivatives by the presence of 1702.9 cm^-1 and 1593 cm^-1 bands, respectively (FTIR). Increasing concentrations of the derivatives yielded uncollapsed/unshrunken lyophilisates. SEM and XRD showed that modification, autoclaving, and freeze-drying yielded beehive-like microstructures of FCMS and FAXS that were completely amorphous. Processing (autoclaving and freeze-drying), therefore, enhanced the amorphousness of the starch derivatives which is required in vaccine stability during processing and storage. These findings indicate that these starch derivatives have potential as novel vaccine stabilizers.

Evaluation of formulations to improve SARS-CoV-2 viability and thermostability after lyophilisation

In the context of the COVID-19 pandemic, virus collections such as EVA-GLOBAL play a key role in the supply of viruses and related products for research. Freeze-drying techniques for viruses represent a method of choice for the preservation of strains and their distribution without the need for a demanding cold chain. Here, we describe an optimised lyophilisation protocol usable for SARS-CoV-2 strains that improves preservation and thermostability. We show that sucrose used as an adjuvant represents a simple and efficient stabilizer providing increased protection for long-term preservation and shipment of the virus under different climatic conditions.

Carboxymethylated and acetylated xerogel derivatives of Plectranthus esculentus starch protect Newcastle disease vaccines against cold chain failure

Developing vaccine stabilizers from local natural sources is desirable especially if the stabilizer would enhance the ability of the antigen to withstand frequent failures in cold chains. The study was undertaken to formulate immunogenic live Newcastle Disease (ND) LaSota vaccines stabilized with modified native starches for use at cold and ambient temperatures and to assess the immunogenicity of the starch stabilized vaccines in vaccinated chickens. Native starch extracted from the tubers of Plectranthus esculentus (Family, Lamiaceae) was modified by carboxymethylation and acetylation/xerogel formation and used as vaccine stabilizers of ND LaSota virus with/without buffers/bulking excipients. Cold Chain Failure (CCF) was simulated by storing the vaccines at 5 ± 2 °C for one month then at 37 ± 1 °C for 96 h. The stability of the samples were evaluated in comparison with peptone stabilized ND vaccines using pH, residual moisture, XRD, reconstitution time, mean embryo infective dose (EID50) and haemagglutination (HA) tests. Haemagglutination inhibition was used to evaluate the efficacy of the vaccines in conferring positive serum antibody titers (≥2³ log₂) in vaccine-naïve 2-week old broilers that were orally administered a single dose of the vaccines kept at 37 ± 1 °C for 96 h and bled weekly over four weeks. Temperature, pH, moisture content and amorphousness impacted vaccine stability. Peptone stabilized vaccines were significantly less stable and most affected by temperature changes with 1.2log₁₀EID50 loss while buffered/bulked trehalose, carboxymethylated and acetylated/xerogelized starch stabilized vaccines were most stable (0.2-0.5log₁₀EID50 loss in titer) after 96 h in CCF. Buffered trehalose stabilized vaccine (TVB) had lower HA titres than peptone and starch stabilized vaccines containing D-mannitol and Na₂HPO₄. Antibody titres of vaccinated broilers were between 3.3 ± 1.398 and 8.35 ± 2.678. All the vaccines were immunogenic (HI ≥ 2³) and developed HI titres (≥2⁴) considered to be protective. Carboxymethylated and acetylated/xerogel derivatives of P. esculentus starch have a great potential as vaccine stabilizers especially in areas prone to CCF.

Freeze-drying of nanoparticles: How to overcome colloidal instability by formulation and process optimization

Lyophilization of nanoparticle (NP) suspensions is a promising technology to improve stability, especially during long-term storage, and offers new routes of administration in solid state. Although considered as a gentle drying process, freeze-drying is also known to cause several stresses leading to physical instability, e.g. aggregation, fusion, or content leakage. NPs are heterogeneous regarding their physico-chemical properties which renders them different in their sensitivity to lyophilization stress and upon storage. But still basic concepts can be deducted. We summarize basic colloidal stabilization mechanisms of NPs in the liquid and the dried state. Furthermore, we give information about stresses occurring during the freezing and the drying step of lyophilization. Subsequently, we review the most commonly investigated NP types including lipophilic, polymeric, or vesicular NPs regarding their particle properties, stabilization mechanisms in the liquid state, and important freeze-drying process, formulation and storage strategies. Finally, practical advice is provided to facilitate purposeful formulation and process development to achieve NP lyophilizates with high colloidal stability.

The Science is There: Key Considerations for Stabilizing Viral Vector-Based Covid-19 Vaccines

Once Covid-19 vaccines become available, 5–10 billion vaccine doses should be globally distributed, stored and administered. In this commentary, we discuss how this enormous challenge could be addressed for viral vector-based Covid-19 vaccines by learning from the wealth of formulation development experience gained over the years on stability issues related to live attenuated virus vaccines and viral vector vaccines for other diseases. This experience has led –over time– to major improvements on storage temperature, shelf-life and in-use stability requirements. First, we will cover work on ‘classical’ live attenuated virus vaccines as well as replication competent viral vector vaccines. Subsequently, we address replication deficient viral vector vaccines. Freeze drying and storage at 2–8 °C with a shelf life of years has become the norm. In the case of pandemics with incredibly high and urgent product demands, however, the desire for rapid and convenient distribution chains combined with short end-user storage times require that liquid formulations with shelf lives of months stored at 2–8 °C be considered. In confronting this “perfect storm” of Covid-19 vaccine stability challenges, understanding the many lessons learned from decades of development and manufacturing of live virus-based vaccines is the shortest path for finding promising and rapid solutions.

Combination of Adsorption and Cellulose Derivative Membrane Coating for Efficient Immobilization of Laccase

Immobilization of enzyme based on combination of adsorption and cellulose derivative membrane coating was established in this work for the first time. Laccase, a commonly used enzyme in varied fields, was chosen as the model enzyme to demonstrate this method. After investigating operational conditions, the optimal process was obtained as follows: diatomite or HPD-417 as the adsorption carrier, 0.5% (w/v) methylcellulose (40,000~50,000) acetone solution as the coating solution, 0.75% (w/v) polyethylene glycol or maltose as the protective agent, and drying at 4 °C for 9 h. Under the optimal conditions, the residual activities of diatomite and HPD-417 immobilized laccase reached 99.33% and 94.15%, respectively. The study on properties showed that the immobilized laccases held high pH tolerance and thermal stability. The immobilized laccases were further applied to the indigo decolorization and 2, 4-dichlorophenol degradation. They showed high catalytic efficiency and could be reused for several batches. On the whole, the immobilization method developed in this work can effectively avoid the inactivation of laccase during immobilization and improve the stability of immobilized laccase. The laccase immobilized by this method shows obvious potential for environmental governance.

Development of a process for upscaling and production of thermotolerant Peste-des-petits ruminants vaccine

Vaccination is the most effective means of preventing Peste-des-petits-ruminants (PPR), an important disease of small ruminant population. The thermolabile nature of PPR vaccine poses a major constraint in shipping, storage and its successful application. In view of limited thermotolerance of PPR virus and ongoing global PPR control and eradication program, development of a thermotolerant PPR vaccine was tried using a novel lyophilization protocol and improved thermostabilization. A lyophilization cycle of 16 h (h) using 200 µl of PPR vaccine virus (stock titre 5.8 log₁₀ TCID₅₀/vial in 200 µl) was developed. For this, five stabilizer formulations were selected out of ten formulations based on the stability of liquid vaccine at 37 °C and three freeze-thaw cycles. Improved thermostabilization of PPR vaccines was obtained by inclusion of 5% trehalose and 0.5% gelatine to Lactalbumin hydrolysate-sucrose (LS) formulations which significantly improved the stability of lyophilized vaccines with a shelf-life of at least 1305.3 days at 2-8 °C, 23.68 days at 25 °C, 20.88 days at 37 °C, 5.01 days at 40 °C and 3.22 days at 45 °C which qualifies the standards of a thermotolerant PPR vaccine as defined by the FAO and OIE. In reconstituted vaccines, the combination of LS, trehalose and gelatin (LSTG) provided a shelf-life of 1.77 days at 37 °C, 22.41 h at 40 °C and 10.05 h at 45 °C. The study suggested that use of the short lyophilization protocol standardized with 200 µl of lyophilized PPR vaccine stabilized with LSTG formulation, can be used to develop and upscale thermotolerant PPR vaccines during national and global PPR control and eradication as targeted by the FAO and OIE by 2030.

The Stabilizing Excipients in Dry State Therapeutic Phage Formulations

Phage therapy has gained prominence due to the increasing pathogenicity of "super bugs" and the rise of their multidrug resistance to conventional antibiotics. Dry state formulation of therapeutic phage is attractive to improve their "druggability" by increasing their shelf life, improving their ease of handling, and ultimately retaining their long-term potency. The use and selection of excipients are critical to stabilize phage in solid formulations and protect their viability from stresses encountered during the solidification process and long-term storage prior to use. Here, this review focuses on the current classes of excipients used to manufacture dry state phage formulations and their ability to stabilize and protect phage throughout the process, as discussed in the literature. We provide perspective of outstanding challenges involved in the formulation of dry state phage. We suggest strategies to improve excipient identification and selection, optimize the potential excipient combinations to improve phage viability during formulation, and evaluate new methodologies that can provide greater insight into phage-excipient interactions to improve design criteria to improve formulation of dry state phage therapeutics. Addressing these challenges opens up new opportunities to re-design and re-imagine phage formulations for improved efficacy as a pharmaceutical product.

Three-percent sucrose acts as a thermostabilizer for cell-adapted foot-and-mouth disease virus without any negative effect on viral growth

AIMS

As cell-adapted foot-and-mouth disease virus (FMDV) with H56R mutation in VP3 has reduced thermostability, this study aimed to investigate the effect of thermostabilizers on cell-adapted FMDV for vaccine production.

METHODS AND RESULTS

We examined the effect of 3% sucrose, 10% (or 25%) glycerol or 10% FBS on cell-adapted FMDV O/SKR/JC/2014, containing H56R mutation in VP3, as vaccine seed virus at -80, 4, 25 or 37°C for 2, 4 or 7 days. The stabilizing effect of 3% sucrose on O/SKR/JC/2014 was observed at 25, 37°C, and after repeated freeze-thaw cycles. Additionally, we tested the effect of 3% sucrose on the growth of FMDV or cells and did not observe any decrease in either viral growth or cell viability.

CONCLUSIONS

Our study showed the protective effect of 3% sucrose on FMDV infectivity at various temperatures; this virus stock in 3% sucrose could be used for infecting cells without the removal of sucrose.

SIGNIFICANCE AND IMPACT OF THE STUDY

We suggest that 3% sucrose-containing medium could be beneficial for the stable storage and transport of cell-adapted FMDV.

Production of trehalose with trehalose synthase expressed and displayed on the surface of Bacillus subtilis spores

BACKGROUND

Bacillus subtilis spores have been commonly used for the surface display of various food-related or human antigens or enzymes. For successful display, the target protein needs to be fused with an anchor protein. The preferred anchored proteins are the outer-coat proteins of spores; outer-coat proteins G (CotG) and C (CotC) are commonly used. In this study, mutant trehalose synthase (V407M/K490L/R680E TreS) was displayed on the surface of B. subtilis WB800n spores using CotG and CotC individually or in combination as an anchoring protein.

RESULTS

Western blotting, immunofluorescence, dot blot, and enzymatic-activity assays detected TreS on the spore surface. The TreS activity with CotC and CotG together as the anchor protein was greater than the sum of the enzymatic activities with CotC or CotG alone. The TreS displayed on the spore surface with CotC and CotG together as the anchoring protein showed elevated and stable specific activity. To ensure spore stability and prevent spore germination in the trehalose preparation system, two germination-specific lytic genes, sleB and cwlJ, were deleted from the B. subtilis WB800n genome. It was demonstrated that this deletion did not affect the growth and spore formation of B. subtilis WB800n but strongly inhibited germination of the spores during transformation. The conversion rate of trehalose from 300 g/L maltose by B. subtilis strain WB800n(ΔsleB, ΔcwlJ)/cotC-treS-cotG-treS was 74.1% at 12 h (350 U/[g maltose]), and its enzymatic activity was largely retained, with a conversion rate of 73% after four cycles.

CONCLUSIONS

The spore surface display system based on food-grade B. subtilis with CotC and CotG as a combined carrier appears to be a powerful technology for TreS expression, which may be used for the biotransformation of D-maltose into D-trehalose.

Saturation mutagenesis and self-inducible expression of trehalose synthase in Bacillus subtilis

Trehalose is a nonreducing disaccharide synthesized by trehalose synthase (TreS), which catalyzes the reversible interconversion of maltose and trehalose. We aimed to enhance the catalytic conversion of maltose to trehalose by saturation mutagenesis, and constructed a self-inducible TreS expression system by generating a robust Bacillus subtilis recombinant. We found that the conversion yield and enzymatic activity of TreS was enhanced by saturation mutations, especially by the combination of V407M and K490L mutations. At the same time, these saturation mutations were contributing to reducing by-products in the reaction. Compared to WT TreS, the conversion yield of maltose to trehalose was increased by 11.9%, and the k_cat /K_m toward trehalose was 1.33 times higher in the reaction catalyzed by treS^V407M-K490L . treS^V407M-K490L expression was further observed in the recombinant B. subtilis W800N(Δσ^F ) under the influence of P_srfA , P_cry3Aa , and P_srfA-cry3Aa promoters without an inducer. It was shown that P_srfA-cry3Aa was evidently a stronger promoter for treS^V407M-K490L expression, with the intracellular enzymatic activity of recombinant treS^V407M-K490L being over 5,800 U/g at 35 hr in TB medium. These results suggested the combination of two mutations, V407M and K490L, was conducive for the production of trehalose. In addition, the self-inducible TreS^V407M/K490L mutant in the B. subtilis host provides a low-cost choice for the industrial production of endotoxin-free trehalose with high yields.

Protective efficacy of a bivalent live attenuated vaccine against duck hepatitis A virus types 1 and 3 in ducklings

Duck hepatitis A virus (DHAV) infection is characterized by an acute, rapidly spreading that affects young ducklings. DHAV-1 or DHAV-3 infection is prevalent, and simultaneous co-infection with both viruses has recently become increasingly frequent in the domestic duck farms. In this study, we developed a bivalent live attenuated vaccine (DHV-HSBP100 and AP-04203P100) for DHAV-1 and DHAV-3 and reported the protective efficacy and safety of the vaccine. At 1-day-old, the ducklings received a bivalent vaccine via intramuscular injection. The immunized ducklings showed effective and rapid protection against virulent DHAV-1 and DHAV-3 at 2 or 3 days post vaccination. Moreover, the ducklings showed a potent humoral immune response that peaked at 3 weeks and were maintained at 6 weeks after vaccination. The bivalent vaccine was safe; ducklings administered 10 doses of bivalent vaccines showed no clinical signs, mortality, gross lesions, and body weight changes compared with those observed in the negative controls. Ducklings vaccinated with a bivalent vaccine were evaluated for tissue tropism and viral replication of vaccine strains. Both bivalent vaccine strains were detected in various organs, and the highest virus replication was detected in the kidneys, among the tested organs. No interference occurred during the replication of both vaccine strains. Thus, these experiments suggest that bivalent vaccines would be useful as a promising and practical strategy for control DHAV outbreaks caused by DHAV-1 and DHAV-3 in duck farms.

A genetically modified rabies vaccine (ERAGS) induces protective immunity in dogs and cattle

PURPOSE

The current live attenuated rabies vaccine must be replaced with a safer vaccine based on the ERAGS strain to prevent rabies in South Korea. We evaluated the safety and immunogenicity of a new strain in dogs and cattle.

MATERIALS AND METHODS

The ERAGS strain, featuring two mutations altering two amino acids in a glycoprotein of rabies virus, was propagated in NG108-15 cells. We lyophilized the virus in the presence of two different stabilizers to evaluate the utilities of such preparations as novel rabies vaccines for animals. To explore safety and immunogenicity, dogs and cattle were inoculated with the vaccine at various doses via different routes and observed daily for 8 weeks post-inoculation (WPI). Immunogenicity was evaluated using a fluorescent antibody virus neutralization test or enzyme-linked immunosorbent assay.

RESULTS

The two different stabilizers did not differ greatly in terms of maintenance of virus viability in accelerated stability testing. No clinical signs of rabies developed in dogs or cattle inoculated with the vaccines (10^7.0 FAID₅₀/mL). Dogs and cattle inoculated intramuscularly with 10^5.0 FAID₅₀/mL exhibited virus neutralization assay titers of 4.6 IU/mL and 1.5 to 0.87 IU/mL at 4 WPI, respectively. All control animals remained rabies virus-seronegative throughout, confirming that no contact transmission occurred between vaccinated and control animals.

CONCLUSION

Our findings indicate that the new rabies vaccine is safe and immunogenic in dogs and cattle.

Effect of chemical stabilizers on the thermostability and infectivity of a representative panel of freeze dried viruses

As a partner of the European Virus Archive (EVA) FP7 project, our laboratory maintains a large collection of freeze-dried viruses. The distribution of these viruses to academic researchers, public health organizations and industry is one major aim of the EVA consortium. It is known that lyophilization requires appropriate stabilizers to prevent inactivation of the virus. However, few studies have investigated the influence of different stabilizers and lyophilization protocols on the thermostability of different viruses. In order to identify optimal lyophilization conditions that will deliver maximum retention of viral infectivity titre, different stabilizer formulations containing trehalose, sorbitol, sucrose or foetal bovine serum were evaluated for their efficacy in stabilizing a representative panel of freeze dried viruses at different storage temperatures (-20°C, +4°C and +20°C) for one week, the two latter mimicking suboptimal shipping conditions. The Tissue Culture Infectious Dose 50% (TCID50) assay was used to compare the titres of infectious virus. The results obtained using four relevant and model viruses (enveloped/non enveloped RNA/DNA viruses) still serve to improve the freeze drying conditions needed for the development and the distribution of a large virus collection.

The influence of stabilizers and rates of freezing on preserving of structurally different animal viruses during lyophilization and subsequent storage

Aims

To make a comparative evaluation of the effects of different stabilizers and freezing rates on structurally different viruses during lyophilization and storage.

Methods and Results

Two virus strains from each of six animal virus families, including both enveloped and nonenveloped viruses, were lyophilized in (i) culture medium, (ii) with the addition of gelatine–sucrose and (iii) skim milk–sodium glutamate. All the virus suspensions were frozen (i) at −80°C or (ii) in liquid nitrogen before lyophilization. Virus titre assay after lyophilization and after 8 months storage at 4°C revealed that the efficacy of stabilizers depended on virus structure. Generally, the best protective quality for enveloped viruses was achieved with gelatine–sucrose, which best maintained their infectivity and envelope morphology. Even additive‐free culture medium proved adequate for nonenveloped viruses. Differences in stabilizer efficacy were also found between virus families and were expressed immediately after lyophilization; the activity of stabilizers in the course of storage was very similar. Freezing in liquid nitrogen proved beneficial for picornaviruses.

Conclusions

The choice of an appropriate stabilizer with respect to virus type is crucial for effective lyophilization.

Significance and Impact of the Study

This study contributes to the establishment of general guidelines for animal virus lyophilization, with particular respect to differences in virus structure.

Stability of infectious human coronavirus NL63

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Optimal protocol for freeze-drying that allows safe and effective preservation of HCoV-NL63 infectious material was developed.

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Lyophilized virus preparations can be stored either at ambient temperature or at +4 °C. In the latter case samples may be stored for at least two months.

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HCoV-NL63 virions are exquisitely stable in liquid media and can be stored also without preservatives at ambient temperature for up to 14 days.

The human coronavirus NL63 was identified in 2004 and subsequent studies showed its worldwide distribution. Infection with this pathogen is associated with upper and lower respiratory tract diseases of mild to moderate severity. Furthermore, HCoV-NL63 is the main cause of croup in children. Within this study an optimal protocol for freeze-drying that allows safe and effective preservation of HCoV-NL63 infectious material was developed. Lyophilized virus preparations can be stored either at ambient temperature or at +4 °C. In the latter case samples may be stored for at least two months. Surprisingly, conducted analysis showed that HCoV-NL63 virions are exquisitely stable in liquid media and can be stored also without preservatives at ambient temperature for up to 14 days.

Measles vaccination using a microneedle patch

Measles vaccination programs would benefit from delivery methods that decrease cost, simplify logistics, and increase safety. Conventional subcutaneous injection is limited by the need for skilled healthcare professionals to reconstitute and administer injections, and by the need for safe needle handling and disposal to reduce the risk of disease transmission through needle re-use and needlestick injury. Microneedles are micron-scale, solid needles coated with a dry formulation of vaccine that dissolves in the skin within minutes after patch application. By avoiding the use of hypodermic needles, vaccination using a microneedle patch could be carried out by minimally trained personnel with reduced risk of blood-borne disease transmission. The goal of this study was to evaluate measles vaccination using a microneedle patch to address some of the limitations of subcutaneous injection. Viability of vaccine virus dried onto a microneedle patch was stabilized by incorporation of the sugar, trehalose, and loss of viral titer was less than 1 log10(TCID50) after storage for at least 30 days at room temperature. Microneedle patches were then used to immunize cotton rats with the Edmonston-Zagreb measles vaccine strain. Vaccination using microneedles at doses equaling the standard human dose or one-fifth the human dose generated neutralizing antibody levels equivalent to those of a subcutaneous immunization at the same dose. These results show that measles vaccine can be stabilized on microneedles and that vaccine efficiently reconstitutes in vivo to generate a neutralizing antibody response equivalent to that generated by subcutaneous injection.