H7N9 pandemic preparedness: A large-scale production of a split inactivated vaccine

In March 2013 it was reported by the World Health Organization (WHO) the first cases of human infections with avian influenza virus A (H7N9). From 2013 to December 2019, 1568 cases have been reported with 616 deaths. H7N9 infection has been associated with high morbidity and mortality rates, and vaccination is currently the most effective way to prevent infections and consequently flu-related severe illness. Developing and producing vaccines against pandemic influenza viruses is the main strategy for a response to a possible pandemic. This study aims to present the production of three industrial lots under current Good Manufacturing Practices (cGMP) of the active antigen used to produce the pandemic influenza vaccine candidate against A(H7N9). These batches were characterized and evaluated for quality standards and tested for immunogenicity in mice. The average yield was 173.50 ± 7.88 μg/mL of hemagglutinin and all the preparations met all the required specifications. The formulated H7N9 vaccine is poorly immunogenic and needs to be adjuvanted with an oil in water emulsion adjuvant (IB160) to achieve a best immune response, in a prime and in a boost scheme. These data are important for initial production planning and preparedness in the case of a H7N9 pandemic.

Vaccination strategies against Zika virus

The epidemic emergence of Zika virus (ZIKV) in 2015-2016 has been associated with congenital malformations and neurological sequela. Current efforts to develop a ZIKV vaccine build on technologies that successfully reduced infection or disease burden against closely related flaviviruses or other RNA viruses. Subunit-based (DNA plasmid and modified mRNA), viral vectored (adeno- and measles viruses) and inactivated viral vaccines are already advancing to clinical trials in humans after successful mouse and non-human primate studies. Among the greatest challenges for the rapid implementation of immunogenic and protective ZIKV vaccines will be addressing the potential for exacerbating Dengue virus infection or causing Guillain-Barré syndrome through production of cross-reactive immunity targeting related viral or host proteins. Here, we review vaccine strategies under development for ZIKV and the issues surrounding their usage.

Achievements and challenges for the use of killed oral cholera vaccines in the global stockpile era

Cholera remains an important but neglected public health threat, affecting the health of the poorest populations and imposing substantial costs on public health systems. Cholera can be eliminated where access to clean water, sanitation, and satisfactory hygiene practices are sustained, but major improvements in infrastructure continue to be a distant goal. New developments and trends of cholera disease burden, the creation of affordable oral cholera vaccines (OCVs) for use in developing countries, as well as recent evidence of vaccination impact has created an increased demand for cholera vaccines. The global OCV stockpile was established in 2013 and with support from Gavi, has assisted in achieving rapid access to vaccine in emergencies. Recent WHO prequalification of a second affordable OCV supports the stockpile goals of increased availability and distribution to affected populations. It serves as an essential step toward an integrated cholera control and prevention strategy in emergency and endemic settings.

Recent Progress towards Novel EV71 Anti-Therapeutics and Vaccines

Enterovirus 71 (EV71) is a group of viruses that belongs to the Picornaviridae family, which also includes viruses such as polioviruses. EV71, together with coxsackieviruses, is widely known for its association with Hand Foot Mouth Disease (HFMD), which generally affects children age five and below. Besides HFMD, EV71 can also trigger more severe and life-threatening neurological conditions such as encephalitis. Considering the lack of a vaccine and antiviral drug against EV71, together with the increasing spread of these viruses, the development of such drugs and vaccines becomes the top priority in protecting our younger generations. This article, hence, reviews some of the recent progress in the formulations of anti-therapeutics and vaccine generation for EV71, covering (i) inactivated vaccines; (ii) baculovirus-expressed vaccines against EV71; (iii) human intravenous immunoglobulin (IVIg) treatment; and (iv) the use of monoclonal antibody therapy as a prevention and treatment for EV71 infections.

Progress on the research and development of inactivated EV71 whole-virus vaccines

The prevalence of diseases caused by EV71 infection has become a serious public health problem in the Western Pacific region. Due to a lack of effective treatment options, controlling EV71 epidemics has mainly focused on the research and development (R&D) of EV71 vaccines. Thus far, five organizations have completed pre-clinical studies focused on the development of inactivated EV71 whole-virus vaccines, including vaccine strain screening, process optimization, safety and immunogenicity evaluation, and are in different stages of clinical trials. Among these organizations, three companies in Mainland China [Beijing Vigoo Biological Co., Ltd. (Vigoo), Sinovac Biotech Ltd. (Sinovac) and Institute of Medical Biology, Chinese Academy of Medical Science (CAMS)] have recently completed Phase III trials for the vaccines they developed. In addition, the other two vaccines, developed by National Health Research Institutes (NHRI) of Taiwan and Inviragen Pte., Ltd (Inviragen), of Singapore, have also completed Phase I clinical trials. Published clinical trial results indicate that the inactivated EV71 vaccines have good safety and immunogenicity in the target population (infants) and confer a relatively high rate of protection against EV71 infection-related diseases. The results of clinical trials suggest a promising future for the clinical use of EV71 vaccines. Here, we review and highlight the recent progress on the R&D of inactivated EV71 whole-virus vaccines.

Effectiveness of the Viet Nam produced, mouse brain-derived, inactivated Japanese encephalitis vaccine in Northern Viet Nam

Background

Japanese encephalitis (JE) is a flaviviral disease of public health concern in many parts of Asia. JE often occurs in large epidemics, has a high case-fatality ratio and, among survivors, frequently causes persistent neurological sequelae and mental disabilities. In 1997, the Vietnamese government initiated immunization campaigns targeting all children aged 1–5 years. Three doses of a locally-produced, mouse brain-derived, inactivated JE vaccine (MBV) were given. This study aims at evaluating the effectiveness of Viet Nam's MBV.

Methodology

A matched case-control study was conducted in Northern Viet Nam. Cases were identified through an ongoing hospital-based surveillance. Each case was matched to four healthy controls for age, gender, and neighborhood. The vaccination history was ascertained through JE immunization logbooks maintained at local health centers.

Principal Findings

Thirty cases and 120 controls were enrolled. The effectiveness of the JE vaccine was 92.9% [95% CI: 66.6–98.5]. Confounding effects of other risk variables were not observed.

Conclusions

Our results strongly suggest that the locally-produced JE-MBV given to 1–5 years old Vietnamese children was efficacious.

Japanese encephalitis (JE) is a disease caused by a flavivirus transmitted by mosquitoes. Although pigs and wild birds are main reservoirs of the disease, it is occasionally transmitted to humans. The majority of infections in humans are asymptomatic. In persons developing encephalitis, JE has a high case-fatality rate and, among survivors, JE frequently causes persistent neurological sequelae and mental disabilities. Therefore, it is a public health concern in many parts of Asia and many countries vaccinate against JE. Since 1997, children in Vietnam are vaccinated in high risk areas and receive a locally-produced vaccine. This study is aimed at evaluating the effectiveness of the Vietnamese JE vaccine through a case-control study, in which 30 cases and 120 controls were enrolled. The effectiveness of the JE vaccine was 92.9% [95% CI: 66.6–98.5], which suggests that the locally-produced JE vaccine given to 1–5 year old Vietnamese children was efficacious.

Large-scale preparation of UV-inactivated SARS coronavirus virions for vaccine antigen

In general, a whole virion serves as a simple vaccine antigen and often essential material for the analysis of immune responses against virus infection. However, to work with highly contagious pathogens, it is necessary to take precautions against laboratory-acquired infection. We have learned many lessons from the recent outbreak of severe acute respiratory syndrome (SARS). In order to develop an effective vaccine and diagnostic tools, we prepared UV-inactivated SARS coronavirus on a large scale under the strict Biosafety Level 3 (BSL3) regulation. Our protocol for large-scale preparation of UV-inactivated SARS-CoV including virus expansion, titration, inactivation, and ultracentrifugation is applicable to any newly emerging virus we might encounter in the future.

A hollow-fiber bioreactor for expanding HIV-1 in human lymphocytes used in preparing an inactivated vaccine candidate

An inactivated HIV vaccine intended to elicit broadly neutralizing antibodies is designed to use a pool of population-prevalent HIV-1 from plasma (PHIV), isolated before evolution of antibody-mediated genetic mutations. A suitable cell substrate (CS) for isolating such PHIV is peripheral blood mononuclear cells (PBMC) after stimulating with phytohemagglutinin (PHA) and interleukin-2 (IL-2). Feasibility of employing a hollow-fiber bioreactor under optimized conditions was investigated for large-scale expansion and efficient recovery of concentrated PHIV. Each CS batch was infected in vitro with a prototype PHIV, the infected cells were introduced into the bioreactor for 7-10 days in co-culture, and the cell-free supernatants were assayed for p24 antigen as an index of HIV synthesis. PBMC versus CD8-depleted (CD8D) CS, 20kDa versus 5kDa molecular weight cut-off (MWCO) bioreactor cartridges, 7- versus 10-day culture periods, and varying concentrations of IL-2, fetal bovine serum (FBS) and glucose content in the medium were functionally evaluated for p24 yield. PBMC cultures in 20kDa MWCO cartridges with 15% FBS, 80IU/mL IL-2 and 2.0g/L glucose produced the highest p24 yield; however, CD8D-CS, 20-30% FBS and 80 IU/mL IL-2 within 5kDa cartridges and 2.0 g/L glucose in the circulating medium was more cost-effective for synthesis of virion p24.

Effect of the purification process and the storage conditions on the efficacy of an inactivated vaccine against heartwater

This work evaluates the effect of purification process and storage conditions (buffer formulation and temperature) on the efficacy of Ehrlichia ruminantium (ER) elementary bodies to be used as an inactivated vaccine candidate against heartwater. In vitro assays revealed that, to avoid major losses in ER integrity and corresponding antigenic properties, a buffer with pH between 5.6 and 8 and an osmolality above 100 mOsmol/kg H(2)O is recommended. Amongst the tested formulations, both PBS and NaCl have shown to stabilize ER antigens at -20 degrees C. To assess the protective properties of the different vaccine formulations, in vivo experiments were performed using a goat model. The results obtained showed that the preparation of ER antigens using a novel membrane-based purification strategy and a simple vaccine formulation (NaCl, -20 degrees C) induced equivalent protection to the conventional vaccine based on ER antigens prepared by a multistep centrifugation methodology and stored at -20 degrees C in PBS buffer.

Lessons from the cat: development of vaccines against lentiviruses

Feline immunodeficiency virus (FIV) is a natural infection of domestic cats, which produces a disease with many similarities to human immunodeficiency virus (HIV) infection in man. The virus is an important cause of morbidity and mortality in pet cats worldwide. As such an effective vaccine is desirable both for its use in veterinary medicine and also as a model for the development of an HIV vaccine. A large number of candidate vaccines have been tested against feline immunodeficiency virus. These include inactivated virus and infected cell vaccines, DNA and viral vectored vaccines, subunit and peptide vaccines and vaccines using bacterial vectors. Ultimately, the development of inactivated virus and infected cell vaccines led to the release of the first licensed vaccine against FIV, in 2002. This review highlights some of the difficulties associated with the development of lentiviral vaccines and some of the lessons that have been learned in the FIV model that are of particular relevance to the development of HIV vaccines.

From lethal virus to life-saving vaccine: developing inactivated vaccines for pandemic influenza

Over the past eight years, cases of human infection with highly pathogenic avian influenza viruses have raised international concern that we could be on the brink of a global influenza pandemic. Many of these human infections have proved fatal and if the viruses had been able to transmit efficiently from person to person, the effects would have been devastating. How can we arm ourselves against this pandemic threat when these viruses are too dangerous to use in conventional vaccine production? Recent technological developments (reverse genetics) have allowed us to manipulate the influenza virus genome so that we can construct safe, high-yielding vaccine strains. However, the transition of reverse-genetic technologies from the research laboratory to the manufacturing environment has presented new challenges for vaccine manufacturers as well as veterinary and public health authorities.

Formalin-inactivated whole virus and recombinant subunit flavivirus vaccines

The Flaviviridae is a family of arthropod-borne, enveloped, RNA viruses that contain important human pathogens such as yellow fever (YF), Japanese encephalitis (JE), tick-borne encephalitis (TBE), West Nile (WN), and the dengue (DEN) viruses. Vaccination is the most effective means of disease prevention for these viral infections. A live-attenuated vaccine for YF, and inactivated vaccines for JE and TBE have significantly reduced the incidence of disease for these viruses, while licensed vaccines for DEN and WN are still lacking despite a significant disease burden associated with these infections. This review focuses on inactivated and recombinant subunit vaccines (non-replicating protein vaccines) in various stages of laboratory development and human testing. A purified, inactivated vaccine (PIV) candidate for DEN will soon be evaluated in a phase 1 clinical trial, and a second-generation JE PIV produced using similar technology has advanced to phase 2/3 trials. The inactivated TBE vaccine used successfully in Europe for almost 30 years continues to be improved by additional purification, new stabilizers, an adjuvant, and better immunization schedules. The recent development of an inactivated WN vaccine for domestic animals demonstrates the possibility of producing a similar vaccine for human use. Advances in flavivirus gene expression technology have led to the production of several recombinant subunit antigen vaccine candidates in a variety of expression systems. Some of these vaccines have shown sufficient promise in animal models to be considered as candidates for evaluation in clinical trials. Feasibility of non-replicating flavivirus vaccines has been clearly demonstrated and further development is now warranted.

Inactivated Hantaan virus vaccine derived from suspension culture of Vero cells

We have developed a cell culture-derived, inactivated vaccine against Hantaan virus for prevention of the hemorrhagic fever with renal syndrome (HFRS). Hantaan virus was purified from a microcarrier culture of Vero E6 cells by ultrafiltration and density gradient centrifugation. Viral infection was inactivated by treatment of the viral stock with formaldehyde. Immunogenic properties of the vaccine were characterized in comparison with Hantavax, a mouse brain-derived, formalin-inactivated vaccine that has been in human use for a decade in Korea. Compared to the Hantavax, immunization of Balb/c mice with the cell culture-based vaccine resulted in a moderate difference in antibody response to the viral nucleocapsid protein but more than five-fold increase in neutralizing activity. Moreover, all six mice immunized with 5 microg of the cell culture-based vaccine were fully protected from challenge with infectious virus, whereas virus was detected in lung and spleen of all animals immunized with the same dose of Hantavax. Four times higher dose of the latter vaccine was needed for complete protection. In the analysis of the humoral immune response to the vaccines, we found that all three viral structural proteins, N, G1 and G2 were immunoprecipitated by sera from animals immunized with the cell culture-based vaccine. In contrast, N and some G1 but no G2 were precipitated by the sera from animals immunized with Hantavax. These results suggest that the cell culture-based vaccine can provide more effective immunity than the Hantavax.

Trials for preparation of inactivated sheep pox vaccine using binary ethyleneimine

Binary ethyleneimine (BEI) was used to inactivate the local Egyptian strain of sheep pox virus. The inactivation process was applied using final concentrations of BEI at 0.5, 1, 2 and 3% for different incubation periods at 37 degrees C. The virus was completely inactivated after 7 hours incubation with by 2% BEI final concentration; the inactivated virus was adsorbed on aluminium hydroxide gel when incubated for 6 hours in a concentration 1:1. The antibody levels were estimated by virus neutralization test and ELISA. Specific antibodies appeared from the 1st week post vaccination and remained until the 4th week post challenge. The prepared vaccine was evaluated for safety, sterility and potency. The vaccine proved to be safe, sterile and inducing protection for the vaccinated lambs when challenged by the virulent sheep pox virus up to 6 months post vaccination.

Development of Vero cell-derived inactivated Japanese encephalitis vaccine

We have established a manufacturing system for a Vero cell-derived inactivated Japanese encephalitis vaccine at a 500l scale. The production system involves expansion of Vero cells using microcarrier, followed by virus infection. Except for an additional purification step, the downstream purification processes are similar to those used for the current mouse brain-derived vaccine; cell removal, concentration and removal of low-molecular weight impurities by membrane filtration, formalin-inactivation, sucrose density gradient ultracentrifugation, and Sulfate-Cellulofine column chromatography are conducted. The antigen obtained from the manufacturing system was highly purified and its physico-chemical and immunological properties were comparable with those of antigen derived from mouse brains. Our system is very simple and could be easily scaled-up to allow vaccine production at a several thousand litre scale.

Immunogenicity, safety and lot consistency in adults of a chromatographically purified Vero-cell rabies vaccine: a randomized, double-blind trial with human diploid cell rabies vaccine

The immunogenicity and safety of a chromatographically purified rabies vaccine (CPRV) was evaluated using US veterinary medical students. In the first study, 242 healthy adults were enrolled in a randomized, modified double-blind, multicenter trial and received five doses of either CPRV or human diploid cell vaccine (HDCV) by intramuscular injection on days 0, 3, 7, 14, and 28 concurrently with human rabies immunoglobulin in a simulated post-exposure prophylaxis regimen. Post-immunization titers in the CPRV and HDCV groups reached 0.5 IU/ml (the WHO-recommended minimally acceptable titer) or greater in all subjects in both vaccine groups by day 14 and remained above that level through day 90. In the second study, 438 healthy adults were enrolled in a randomized, double-blind, multicenter trial and assigned to receive five doses from one of three lots of CPRV by intramuscular injection on days 0, 3, 7, 14, and 28 in a simulated post-exposure prophylaxis regimen to evaluate lot consistency. Post-immunization titers rapidly increased to over 0.5 IU/ml by day 14 for all subjects and remained above that level through day 42 when the study was terminated. The three lots were considered equivalent. The percentage of subjects with at least one local reaction during the five-dose regimen was slightly lower in the CPRV group than in the HDCV group (P=0.06). The most frequently reported local reaction for all doses of vaccine was pain at the injection site. Headache, myalgia, and malaise were the most frequently reported systemic events. The percentage of subjects with at least one systemic event was significantly lower for CPRV (P=0.0084). No vaccine-related serious adverse reaction was reported in these studies. The results of these studies indicate that CPRV administered intramuscularly to healthy adults is immunogenic and is associated with fewer local and systemic reactions than HDCV.

Successful vaccination against Leishmania donovani infection in Indian langur using alum-precipitated autoclaved Leishmania major with BCG

Autoclaved Leishmania major (ALM) along with BCG, presently undergoing phase II clinical trial by WHO for its vaccine potential against cutaneous leishmaniasis, has been successfully evaluated in single and triple dose schedules against L. donovani in Indian langurs (Presbytis entellus). Encouraged with the results, another formulation alum-precipitated ALM (provided by WHO) along with BCG has been evaluated in this system. Eight monkeys were vaccinated with alum-precipitated ALM + BCG (1 mg of each per animal) while four were kept as unvaccinated controls. All were challenged with 100 x 10(6) amastigotes i.v. on day 60 post vaccination. Parasitic assessment in splenic tissue was performed on day 45, 90 and 180 p.c. Initially, seven of the eight vaccinated monkeys developed infection (two to six amastigotes per 1000 cell nuclei), which resolved by day 180 p.c., while the eighth monkey had a parasite burden of 14 amastigotes per 1000 cell nuclei on day 45 p.c. and died on day 130 p.c. On the other hand, there was progressive infection in unvaccinated control animals and three out of four died between days 110 and 120 p.c., and one monkey, which had low parasite burden, died on day 178 p.c. Prior to challenge, there was an initial rise in antileishmanaial antibodies in the vaccinated group compared to the unvaccinated control group, which later came down to normal level, while it remained higher in the unvaccinated control group. An increasing pattern of antigen-specific proliferative responses and interferon-gamma level to the two antigens--autoclaved L. donovani (ALD) and ALM--was observed in vaccinated monkeys throughout the experiment. There was a good correlation between parasite burden and IFN-gamma level on days 90 and 180 p.c., indicating IFN-gamma response as a sensitive parameter of immune status. The findings suggest alum-precipitated ALM+BCG as a potential vaccine against visceral leishmaniasis and warrants clinical trials.

A purified inactivated Japanese encephalitis virus vaccine made in Vero cells

A second generation, purified, inactivated vaccine (PIV) against Japanese encephalitis (JE) virus was produced and tested in mice where it was found to be highly immunogenic and protective. The JE-PIV was made from an attenuated strain of JE virus propagated in certified Vero cells, purified, and inactivated with formalin. Its manufacture followed current GMP guidelines for the production of biologicals. The manufacturing process was efficient in generating a high yield of virus, essentially free of contaminating host cell proteins and nucleic acids. The PIV was formulated with aluminum hydroxide and administered to mice by subcutaneous inoculation. Vaccinated animals developed high-titered JE virus neutralizing antibodies in a dose dependent fashion after two injections. The vaccine protected mice against morbidity and mortality after challenge with live, virulent, JE virus. Compared with the existing licensed mouse brain-derived vaccine, JE-Vax, the Vero cell-derived JE-PIV was more immunogenic and as effective as preventing encephalitis in mice. The JE-PIV is currently being tested for safety and immunogenicity in volunteers.

Potency analysis of inactivated vaccines for Aujeszky's disease virus (ADV), strain RC/79: lymphocyte stimulation in immunized pigs

Mitogenic and antigenic lymphocyte stimulation was examined in pigs that had been immunized with 2 inactivated vaccines which had been prepared with Aujesky's disease virus (ADV), strain RC/79. One vaccine was partially purified by ultra-centrifugation (Vaccine A) the other one was not (Vaccine B). A second dose of vaccine had no influence over the blastogenic response when the lymphocytes were stimulated with phytohemoagglutinin (PHA). Lymphocyte response to the ADV antigen in the immunized pigs was significantly higher at day 30 post inoculation than at day 0 indicating that it was highly specific. Cellular antigens contained in the viral cultures produced a slight non-specific response as shown by a low increase in the levels of lymphocyte blastic transformation (LBT) in the control group at day 30 p.i., this group only received a non infected Vero cell suspension. This was the case in pigs that received vaccine A as well as in those that were vaccinated with vaccine B. Vaccine B contains a greater quantity of contaminating cellular antigens, since it is an impure vaccine. Such antigens could act as non-specific immunomodulators, potentiating cell-mediated immunity (CMI). This assay demonstrated that inactivated vaccines produced with VPR-RC/79, partially purified and unpurified are capable of inducing a humoral immune response. The blastogenic reaction of the peripheral blood lymphocytes to antigens of ADV strain RC/79, indicated that the employed immunogens also induced the CMI. Results indicate that the analyzed immunogens could be considered for the possible implementation of epidemiological measures, which imply the use of vaccines to prevent pseudo-rabies in Argentina.

Technologies for the design, discovery, formulation and administration of vaccines

This paper summarizes major technologies, with emphasis on applications to preventive vaccines for infectious diseases. A limited number of examples of each technology are provided.

Effects of hydrostatic pressure on the Leptospira interrogans: high immunogenicity of the pressure-inactivated serovar hardjo

The Hardjoprajitno strain of Leptospira interrogans serovar hardjo was subjected to different hydrostatic pressures. Complete inactivation occurred when the leptospires were treated with 2 kbar for 60 min. Electron microscopy showed dislocation of the outer membrane, partial loss of the helical shape and extrusion of the axial filament from the cytoplasmic cylinder of the pressurized leptospires. When the pressure-treated leptospires were inoculated into rabbits they were highly immunogenic. The sera of these animals presented a titer of 2048 in the microscopic serum agglutination reaction. Fluorescence measurements indicated that the action of pressure on the leptospires might have resulted from perturbation on membrane protein components, permitting the binding of the fluorescent probe bis (8-anilinonaphthalene-1-sulfonate) (Bis-ANS). This is the first report of the use of hydrostatic pressure to inactivate pathogenic bacteria with the potential to lead to a vaccine.

Structural differences between foot-and-mouth disease and poliomyelitis viruses influence their inactivation by aziridines

Inactivation of foot-and-mouth disease virus (FMDV) and poliovirus by ethyleneimine (EI) and N-acetylethyleneimine (AEI) has been studied at 25 degrees and at 37 degrees C and in different ionic conditions. FMDV is inactivated rapidly in 100 mM Tris pH 7.6 by each reagent at both temperatures. Poliovirus is also inactivated rapidly in 100 mM Tris by EI at both temperatures and by AEI at 37 degrees C. However, it is inactivated much more slowly by AEI at 25 degrees C; but if the virus is first incubated overnight at 2 degrees C with AEI before transferring to 25 degrees C inactivation then proceeds rapidly. Moreover, the rate of inactivation at 25 degrees C is markedly increased if the virus is suspended in 1 mM Tris. We had interpreted these differences as being due to the greater penetrability of poliovirus (i) in 100 mM Tris at 37 degrees C compared with 25 degrees C and (ii) at lower ionic strength. This interpretation has been confirmed by electron microscopy of FMDV and poliovirus particles stained with phosphotungstic acid. At the elevated temperature, poliovirus had an average diameter of 34+/-0. 21 nm and the stain outlined the nucleic acid core and the individual subunits, whereas at 25 degrees C it averaged 28+/-0.13 nm and the stain did not penetrate the particle. This study also showed that the particle diameter alters with changes in buffer concentration, being 28+/-0.13 nm in 100 mM Tris, 31+/-0.16 nm in 10 mM Tris and 34+/-0.21 nm in 1 mM Tris. The changes in poliovirus are reversible as addition of 1/10 volume of 1 M Tris to the virus in 1 mM Tris resulted in the return of the diameter to 28+/-0.13 nm. FMDV, on the other hand, was less sensitive to osmotic differences as its particle diameter only varied by 7% over the 100-fold change in buffer concentration compared with the 22% change observed for poliovirus.

Evaluation of the purity of a purified, inactivated hepatitis A vaccine (VAQTA)

Manufacture of VAQTA, an inactivated hepatitis A virus vaccine, includes extensive purification of the intact virus particle to remove endogenous components from the host cell culture lysate as well as compounds introduced in the upstream purification process. Analysis of the final purified hepatitis A virus product by SDS-PAGE prior to inactivation shows that greater than 95% of the protein in the preparation is found in four protein bands, which have been confirmed to be hepatitis A virus capsid proteins VP0, VP1, VP2 and VP3 based on Western blot and mass spectrometry analyses. Validation of the manufacturing process and direct analysis of the final product were used to demonstrate that no other specific host cell-derived components are detected and that process residuals are all below the limits of detection of the assays used. Establishment of a rigorous standard of high purity for this product was pursued to minimize the impact of impurities during clinical development of this product and will facilitate the incorporation of this product into combination vaccines.

Towards an HIV-1 vaccine: lessons from studies in macaque models

The development of a safe and effective vaccine for the prevention of AIDS has thus far proven to be extremely difficult, at least in part due to complexities associated with HIV-1 and its pathogenesis. The recent description of individuals transiently infected with HIV-1, as well as persons who survived HIV-1 infection for more than 15 years, indicates the ability of the immune response of certain individuals to control HIV-1 infection. Moreover, vaccination-challenge experiments in macaques infected with simian immunodeficiency virus have shown that protection against infection or development of disease may be achieved in the absence of sterilizing immunity, suggesting that the goals for AIDS vaccine development may have to be redefined. In addition, evaluation of new lentivirus vaccine strategies may largely benefit from the use of the newly developed chimeric simian-human immunodeficiency viruses, allowing the testing of HIV-1 antigen based vaccines in macaques.

Development of a mammalian cell (Vero) derived candidate influenza virus vaccine

Influenza vaccine production is dependent on the availability of embryonated hen eggs for virus growth. This is an extremely cumbersome system with many disadvantages with respect to selection of virus variants and presence of adventitious viruses. We have developed an alternative cell culture system which allows rapid production of large volumes of vaccine. The World Health Organisation (WHO) approved Vero cell line was used in serum-free culture to grow a multitude of influenza strains to high titre. This system could be scaled-up to allow vaccine production with a 1200 litre fermenter volume. A purification scheme was developed which resulted in a high purity whole virus vaccine. This was demonstrated to be at least as immunogenic as a conventional egg-derived preparation in a mouse model.

Use of nuclease enzyme in the purification of VAQTA, a hepatitis A vaccine

The development of the purification process for VAQTA, which results in a highly purified inactivated hepatitis A vaccine, was driven by modifications in the cell-culture and harvest methods which permit hepatitis A virus propagation to support large-scale manufacture. The starting material for the purification was initially a concentrated cell pellet scraped from roller bottles. However, when the cell-culture method was scaled up to use high-surface-area Nunc cell factories or Costar cubes, the early steps in the process had to be modified to handle large volumes of dilute lysate. Membrane concentration was used at first, and a highly purified vaccine was prepared, but virus-poly(nucleic acid) complexes were formed, which reduced the yields in later processing steps. The introduction of a nuclease digestion immediately after harvest followed by capture chromatography on an anion-exchange column eliminated the formation of these complexes and resulted in more consistent performance and higher yields of downstream operations.

Optimization of poly(ethylene glycol) precipitation of hepatitis A virus used to prepare VAQTA, a highly purified inactivated vaccine

Poly(ethylene glycol) precipitation has been successfully used to concentrate and purify hepatitis A virus from crude lysate preparations for production of VAQTA, a highly purified, formalin-inactivated hepatitis A vaccine. Initial results showed that nucleic acids present in the starting material were problematic for the performance of the poly(ethylene glycol) precipitation step. Extensive experiments were carried out to identify processing conditions suitable for vaccine manufacture which would enhance product yield and improve purity. Results of these studies indicated that the earlier practice of concentrating crude virus-containing lysate using semipermeable membranes led to aggregation of high molecular weight nucleic acids. This aggregated material coprecipitated with the virus during the subsequent poly(ethylene glycol) precipitation step; variable amounts of nucleic acids led to inconsistent virus recovery and product purity. Nuclease treatment of the crude lysate preparations decreased the molecular size of the nucleic acids and significantly reduced their coprecipitation with the virus. Further experiments demonstrated that optimal placement of the nuclease treatment was at the lysate stage followed by a capture step using anion exchange chromatography. These steps combined with optimization of the virus concentration, ionic strength, and pH of the poly(ethylene glycol) precipitation led to effective and selective concentration of the virus which significantly enhanced process reproducibility and control.

Vaccination today and tomorrow

The vaccines against infectious diseases in use today are, with few exceptions, prepared from the causal agents themselves, either by inactivating them with a chemical such as formaldehyde or by attenuating them so that they grow and thus evoke an immune response in the natural host but cause no disease. These empirical approaches have produced many highly successful vaccines. Increasing knowledge at the molecular level of the agents and of the immune response to protein antigent is now providing us with the opportunity to design vaccines that will elicit protective responses without the need to use the agents themselves. The critical issue is to identify the immune responses that correlate with protection.

Vaccine manufacture at the time of a pandemic influenza

In the event of a major influenza epidemic, the availability of a potent and safe vaccine would be a major concern. The following presentation describes the main features of a flu vaccine manufacturing campaign: beginning with the supply of embryonated eggs, in which the flu viruses are cultivated, through the different steps of vaccine production - egg harvest, purification, inactivation, splitting - down to the final vaccine formulation and aseptic filling in the appropriate containers. In usual times, such a production cycle takes over 70 weeks. In an emergency situation, the manufacturers and the authorities would have to take innovative approaches to minimize such delays. This will inevitably translate into an enormous strain on all the players in such a project, from the egg suppliers to the organisers of the vaccine dispatching and administration. It will result in suboptimal yields and costs. However, facing a massive and urgent need of vaccine, both the authorities and the vaccine manufacturers must work together to supply the necessary doses in time.

[A trial to produce an inactivated Lassa fever vaccine]

A single and double immunization of Papio hamadryas monkeys with an inactivated concentrated purified adsorbed preparation of Lassa virus in doses of 0.5-1.0 and 1.1-2.1 mg by protein, respectively, protected the animals against the development of the disease and occurrence of viremia after an intramuscular challenge with 0.4 PFU dose. Upon aerogenic infection of monkeys protection of 50% of the animals was achieved by a single immunization with the inactivated preparation in a dose 1.1 mg by protein.

Inhibition of Mycoplasma gallisepticum growth and attachment to chick tracheal rings by antibodies to a 64-kilodalton membrane protein of M. gallisepticum

A Mycoplasma gallisepticum (MG) strain R protein of 64 kilodaltons (p64) was partially digested from the surface of the bacterium by trypsin. Monospecific polyclonal anti-p64 IgG inhibited attachment of MG to chick tracheal rings by as much as 69%. However, trypsin treatment of viable MG cells did not reduce attachment to tracheal rings or hemagglutination titer. Anti-p64 IgG inhibited growth of MG strain R in broth and on solid media, inhibited the uptake of radiolabeled thymidine, but did not inhibit hemagglutination. Anti-p64 IgG inhibited growth of eight MG strains on solid medium. The degree of growth inhibition varied widely depending on the strain and correlated positively with the reported virulence of the MG strains with one exception (A5969). An IgG monoclonal antibody to p64 (MyG 001) inhibited growth of MG strain R on solid and in broth media. The strong attachment-inhibition activity of anti-p64 IgG may result from its growth-inhibiting activity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of MG strains suggested that p64 is expressed in higher amounts in vitro in virulent strains (R, S6) than in strains of low virulence (F, M876, K503, K703, K730). P64 should be used to immunize chickens to determine if it can stimulate a growth and attachment-inhibiting response in the respiratory tract.

Immunization of Macaca fascicularis with inactivated SIV preparations: challenge with human- or monkey-derived SIV and the effects of a longer immunization schedule

In cynomolgus monkeys, we compared two human-derived SIVmac251 whole virus vaccines, a long vs short immunization schedule, and two different challenge viruses. Both vaccines induced protection after challenge with human-derived SIVmac251/32H. There was no difference between the two schedules of immunization. Seven monkeys, five of which were protected following the first challenge, were reboosted and rechallenged with monkey-derived SIVmac251, but no protection was observed. The titers of anti-human cell or -SIV neutralizing antibodies were not related to protection.

Whole inactivated SIV vaccine grown on human cells fails to protect against homologous SIV grown on simian cells

Several groups have reported protection against experimental SIV infection in macaques immunized with a whole inactivated virus vaccine. The aim of the current study was to investigate whether five macaques vaccinated with whole inactivated SIV and previously shown to be protected against challenge with two divergent strains of SIV grown on human cells could resist challenge with a subsequent homologous SIV grown on macaque cells. We show here that this same vaccine did not protect when the challenge virus was grown on primary cells of monkey origin.

Preparation and immunogenicity of an inactivated hepatitis A vaccine

A hepatitis A vaccine was prepared by formaldehyde inactivation of purified hepatitis A virus (HAV) LSH/S strain grown on human diploid MRC-5 cells. The vaccine was devoid of residual infectivity in vitro and failed to induce in marmoset monkeys any pathological features or variations of haematological and clinical chemistry values. Infectious HAV particles were not detected in faeces and sera of the vaccinated primates by ELISA or after passages in MRC-5 cells. The immunogenicity of the vaccine was evaluated by injecting guinea-pigs with 0.8, 0.2 or 0.05 micrograms of HAV antigen adsorbed onto 0.5 and 1 mg of Al (OH)3 or 0.3 mg of AlPO4. The antibody response, measured by a competitive radioimmunoassay, was dose- and adjuvant-dependent. One injection of 0.2 micrograms of AlPO4-adsorbed HAV antigen induced seroconversion in 100% of animals and high levels of specific and neutralizing serum antibodies. A further increase of antibody titres was observed after the second and third inoculations. These results show that this vaccine formulation is safe and immunogenic in animal models, and suggest that it should be evaluated further by human clinical studies.

Principles of selective inactivation of viral genome. VIII. The influence of beta-propiolactone on immunogenic and protective activities of influenza virus

The influence of beta-propiolactone action on the immunogenic and protective activity of the influenza virus A/WSN/33 (H1N1) has been studied. The production of antibodies against virion surface antigens in mice immunized intramuscularly by the modified virus was enhanced with the increase of inoculating dose from 6 x 10(7) to 1.5 x 10(8) viral particles per animal. The immunizing dose of 6 x 10(7) produced complete protection of immunized animals against a lethal challenge of A/WSN/33 virus. The inhibition of virus reproduction in animal lungs was increased with the increase of the virus immunizing dose up to 6 x 10(8). At a constant dose the inhibition of virus reproduction decreases with the increase of the virus modification extent.

Beta-propiolactone treatment impairs the biological activity of residual DNA from BHK-21 cells infected with rabies virus

The effects of beta-propiolactone (BPL), an alkylating and virus inactivating agent, on the structural and in vitro biological properties of different DNA preparations from BHK-21 cells were investigated. Both uninfected and rabies virus-infected cells were used. Purified cellular DNA (celDNA) was used as the reference, and supernatants from infected cells were treated with BPL. For structural and biological studies three types of DNA preparation were tested: celDNA; purified DNA from cell (infected or uninfected) supernatant (pcsDNA) with or without BPL treatment; and residual cell DNA present in purified rabies virus (inactivated or not) preparations. Rabies infection and BPL (diluted 1:4000) treatment induced modifications in the structure of the three DNA types, including strand breaks and nicks. The damage to the DNA structure by BPL modifies the biological properties of the pcsDNA appraised by its ability to serve as the template in vitro for different polymerases. When rabies virus was inactivated with BPL diluted 1:1000 the DNA damage increased dramatically: small double-stranded DNA fragments (50-200 base pairs) were generated which could not function as templates for polymerases.

Assessment of inactivation of hepatitis A vaccine by compound PCR

Assuring the complete inactivation of hepatitis A virus (HAV) vaccine commonly requires prolonged tissue culture amplification, followed by detection of virus antigen in cell lysates. A reliable, but faster, alternative procedure is highly desirable since it will permit the prescreening of experimental batches of killed HAV, prior to tissue-culture amplification. We established experimental conditions for simultaneous, polymerase chain reaction (PCR)-based amplification of viral and cellular mRNA sequences from infected cell RNA (compound PCR). Under these conditions, the presence of virus-specific amplified sequences, as detected by Southern blot, allows the identification of incompletely inactivated vaccine batches with a threshold practically identical to that of the more time-consuming subculture and ELISA. Compound PCR is, by its nature flexible enough for adaption to different requirements and it should prove useful for rapid prescreening of vaccine batches and pilot studies for improvement of inactivation protocols.

Phase 1 clinical tests of influenza MDP-virosome vaccine (KD-5382)

MDP-virosome vaccine, which contains haemagglutinin (HA) and neuraminidase (NA) antigens isolated from influenza virus combined with 6-O-(2-tetradecylhexadecanoyl)-N-acetylmuramoyl-L-alanyl-D-isoglutamine) (B30-MDP) and cholesterol was tested, in comparison with a currently used HA vaccine, for immunogenicity and adverse reactions on 77 adult male volunteers. The volunteers were divided into eight groups, and each individual was injected subcutaneously once, or twice at a 4 week interval, in their upper arm with one of seven different MDP-virosome vaccine preparations or with HA vaccine as control. Of the three virus strains used as vaccine antigens, MDP-virosome vaccines induced higher haemagglutination inhibiting (HI) antibody to A/Yamagata/120/86 (H1N1) and A/Fukuoka/C29/86 (H3N2) than did HA vaccine, whereas it induced lower HI antibody to B/Nagasaki/1/87, comparable with that induced by HA vaccine. Regarding local adverse reactions, MDP-virosome vaccinees frequently developed mild local pain, reddening and swelling, which disappeared within 5 days; as regards systemic no adverse reactions, leucocytosis developed among the MDP-virosome vaccines, but no other reactions were observed. The leucocytosis may have been caused by the pharmacoimmunological activity of B30-MDP derivatives.

[The protective activity of preparations made from the tick-borne encephalitis virus grown using different cell cultures]

The preparations of tick-borne encephalitis (TBE) virus grown in swine embryo kidney cell culture have been shown to possess pronounced protective activity per unit of virion protein E in comparison with TBE virus preparations derived from cell culture 4647 and chick embryo cell culture. The antigenic activity of all virus preparations under study has proved to be practically the same. The role of post-translation modifications of TBE virus protein E in the manifestation of some of its biological properties is discussed.

[A comparison of the protective properties of preparations of the virion and nonvirion ("soluble") antigens of the tick-borne encephalitis virus]

A comparative assessment of the protective properties of virion (VA) and nonvirion ("soluble") (NA) antigens of tick-borne encephalitis virus prepared as inactivated samples close in their parameters to vaccine preparations was carried out. The NA in the preparations free from VA or containing only trace, nonprotective amounts of it, was shown to have significantly lower protective properties than VA and exerted no booster effect on the protective activity when added to VA preparations.

Principles of selective inactivation of viral genome. VI. Inactivation of the infectivity of the influenza virus by the action of beta-propiolactone

The kinetics of inactivation of the infectivity of the influenza virus by beta-propiolactone have been studied. Rate constants have been determined for inactivation of the A/Leningrad/385 (H3N2) and B/Leningrad/489/80 influenza virus under the action of beta-propiolactone on a virus-containing allantoic fluid and on a purified viral suspension. The data obtained allow calculation of the time required for inactivation of the influenza virus infectivity to a given extent in virus-containing solutions at any initial concentration of beta-propiolactone.

Programmed antigenic stimulation: kinetics of the immune response to challenge infections of mice primed with influenza inactivated whole virus or neuraminidase vaccine

Mice were immunized with either inactivated whole virus influenza A (H3N2) virus (WV) vaccine or with purified N2 neuraminidase (NA) vaccine then challenged with mouse-adapted homologous infective virus at intervals of 1-141 days later in order to ascertain the optimal vaccine-infection interval for induction of resistance to subsequent infection. Measured by serological or infection suppressing response, this interval was 15 days for both vaccines. Maximal reduction in pulmonary virus replication during initial (postvaccination) infection was achieved with WV vaccine, but in second infection by NA vaccine. This study provides further support for the concept of infection-permissive immunization with NA vaccines and suggests the promise of programmed antigenic stimulation by coupling of non-replicating and replicating antigens in the induction of solid immunity.

Principles of selective inactivation of viral genome. V. Rational selection of conditions for inactivation of the viral suspension infectivity to a given extent by the action of beta-propiolactone

The influence of the initial concentration of beta-propiolactone, the composition of the solution, temperature, and pH on the bacteriophage MS2 infectivity inactivation kinetics has been studied. Rate constants have been determined for the infectivity inactivation and for the change in the concentration (the consumption) of the reactant under inactivation conditions. These constants have been shown to permit a sufficiently precise description of the phage MS2 survival curves under the action of beta-propiolactone. These data have been used to put forward a kinetic approach for the rational determination of conditions for inactivation of the viral infectivity to a required extent with agents whose concentration decreases during inactivation as a result of hydrolysis and reactions involving the medium components.