Comparison of the effect of various chemical stabilizers and lyophilization cycles on the thermostability of a Vero cell-adapted rinderpest vaccine

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.

A universal tool for stability predictions of biotherapeutics, vaccines and in vitro diagnostic products

It is of particular interest for biopharmaceutical companies developing and distributing fragile biomolecules to warrant the stability and activity of their products during long-term storage and shipment. In accordance with quality by design principles, advanced kinetic modeling (AKM) has been successfully used to predict long-term product shelf-life and relies on data from short-term accelerated stability studies that are used to generate Arrhenius-based kinetic models that can, in turn, be exploited for stability forecasts. The AKM methodology was evaluated through a cross-company perspective on stability modeling for key stability indicating attributes of different types of biotherapeutics, vaccines and biomolecules combined in in vitro diagnostic kits. It is demonstrated that stability predictions up to 3 years for products maintained under recommended storage conditions (2-8 °C) or for products that have experienced temperature excursions outside the cold-chain show excellent agreement with experimental real-time data, thus confirming AKM as a universal and reliable tool for stability predictions for a wide range of product types.

Use of Stability Modeling to Support Accelerated Vaccine Development and Supply

Stability assessment of pharmaceuticals in specific storage and shipment conditions is a key requirement to ensure that safe and efficacious products are administered to patients. This is particularly relevant for vaccines, with numerous vaccines strictly requiring cold storage to remain stable. When stability evaluation is exclusively based on real-time data, it may represent a bottleneck for rapid and effective vaccine access. Stability modeling for vaccines represents a key resource to predict stability based on accelerated stability studies; nevertheless, this approach is not fully exploited for these kinds of products. This is likely because of the complexity and diversity of vaccines, as well as the limited availability of dedicated guidelines or illustrative case studies. This article reports a cross-company perspective on stability modeling for vaccines. Several examples, based on the direct experience of the contributors, demonstrate that modeling approaches can be highly valuable to predict vaccines’ shelf life and behavior during shipment or manipulation. It is demonstrated that modeling methodologies need to be tailored to the nature of the vaccine, the available prior knowledge, and the monitored attributes. Considering that the well-established strategies reported in ICH or WHO guidelines are not always broadly applicable to vaccines, this article represents an important source of information for vaccine researchers and manufacturers, setting the grounds for further discussion within the vaccine industry and with regulators.

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.

Evaluation of mucoadhesive property and the effect of Boswellia carteri gum on intranasal vaccination against small ruminant morbillivirus infection (PPR)

A study was conducted to evaluate mucoadhesive property and immunomodulatory effect of phytogenic gums from Boswellia frereana, Boswellia carteri andCommiphora myrrha on intranasal Peste des petits ruminants (PPR) vaccination in goats and sheep in an ex-vivo and in-vivo situations. Plant gums were purified, dried and compressed into 500gm tablets. Modified shear stress measurement technique was used on freshly excised trachea and intestine tissues of goat to measure peak adhesion time. Forty eight animals (24 goats and 24 sheep) were divided into eight groups (of 3 goats and 3 sheep) and immunized intranasally with gum-vaccine combinations in two ratios (1:1, 1:2). Antibody against PPR virus was measured on day 14, 28, 42 and 56 post vaccination using H-based PPR bELISA. The peak adhesion time of the different gums was transient. PPR virus antibodies were detected in all immunized goats and sheep but not in unvaccinated control. The best percentage inhibition was recorded for Boswellia carteri-vaccine combination group at a ratio of 1:1. Administration of Boswellia carteri-PPR vaccine combination through intranasal or subcutaneous route, elicited similar antibody titre, implying that the intranasal route may be used as a non-invasive alternative delivery in PPR vaccination of small ruminants.

Biophysical virus particle specific characterization to sharpen the definition of virus stability

Vaccine thermostability is key to successful global immunization programs as it may have a significant impact on the continuous cold-chain maintenance logistics, as well as affect vaccine potency. Modern biological and biophysical techniques were combined to in-depth characterize the thermostability of a formulated rabies virus (RABV) in terms of antigenic and genomic titer, virus particle count and aggregation state. Tunable resistive pulse sensing (TRPS) and nanoparticle tracking analysis (NTA) were used to count virus particles while simultaneously determining their size distribution. RABV antigenicity was assessed by NTA using a monoclonal antibody that recognize a rabies glycoprotein (G protein) conformational epitope, enabling to specifically count antigenic rabies viruses. Agreement between antigenicity results from NTA and conventional method, as ELISA, was demonstrated. Additionally, NTA and ELISA showed mirrored loss of RABV antigenicity during forced degradation studies performed between 5 °C and 45 °C temperature exposure for one month. Concomitant with decreased antigenicity, emergence of RABV particle populations larger than those expected for rabies family viruses was observed, suggesting RABV aggregation induced by thermal stress. Finally, using a kinetic-based modeling approach to explore forced degradation antigenicity data (NTA, ELISA), a two-step model accurately describing antigenicity loss was identified. This model predicted a RABV shelf-life of more than 3 years at 5 °C; significant loss of antigenicity was predicted for samples maintained several months at ambient temperature. This thorough characterization of RABV forced degradation study originally provided a time-temperature mapping of RABV stability.

An overview of process intensification and thermo stabilization for upscaling of Peste des petits ruminants vaccines in view of global control and eradication

Peste des petits ruminants (PPR) has been recognized as a globally distributed disease affecting the small ruminant population. The disease results in severe economic losses mainly to small land holders and low input farming systems. The control of PPR is mainly achieved through vaccination with available live attenuated vaccines. The thermo labile nature of PPR virus poses a major constraint in production of quality vaccines which often results in vaccine failures. The lack of quality vaccine production jeopardize the wide vaccination coverage especially in countries with poor infrastructure due to which PPR persists endemically. The vaccine production system may require augmentation to attain consistent and quality vaccines through efforts of process intensification integrated with suitable stabilizer formulations with appropriate freeze drying cycles for improved thermo tolerance. Manufacturing of live attenuated PPR vaccines during batch cultures might introduce defective interfering particles (DIPs) as a result of high multiplicity of infection (MOI) of inoculums, which has a huge impact on virus dynamics and yield. Accumulation of DIPs adversely affects the quality of the manufactured vaccines which can be avoided through use of appropriate MOI of virus inoculums and quality control of working seed viruses. Therefore, adherence to critical manufacturing standard operating procedures in vaccine production and ongoing efforts on development of thermo tolerant vaccine will help a long way in PPR control and eradication programme globally. The present review focuses on the way forward to achieve the objectives of quality vaccine production and easy upscaling to help the global PPR control and eradication by mass vaccination as an important tool.

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.

Future research to underpin successful peste des petits ruminants virus (PPRV) eradication

Peste des petits ruminants virus (PPRV) is a significant pathogen of small ruminants and is prevalent in much of Africa, the Near and Middle East and Asia. Despite the availability of an efficacious and cheap live-attenuated vaccine, the virus has continued to spread, with its range stretching from Morocco in the west to China and Mongolia in the east. Some of the world's poorest communities rely on small ruminant farming for subsistence and the continued endemicity of PPRV is a constant threat to their livelihoods. Moreover, PPRV's effects on the world's population are felt broadly across many economic, agricultural and social situations. This far-reaching impact has prompted the Food and Agriculture Organization of the United Nations (FAO) and the World Organisation for Animal Health (OIE) to develop a global strategy for the eradication of this virus and its disease. PPRV is a morbillivirus and, given the experience of these organizations in eradicating the related rinderpest virus, the eradication of PPRV should be feasible. However, there are many critical areas where basic and applied virological research concerning PPRV is lacking. The purpose of this review is to highlight areas where new research could be performed in order to guide and facilitate the eradication programme. These areas include studies on disease transmission and epidemiology, the existence of wildlife reservoirs and the development of next-generation vaccines and diagnostics. With the support of the international virology community, the successful eradication of PPRV can be achieved.

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 bovine model for elucidating the role of γδ T cells in controlling infectious diseases of importance to cattle and humans

There are several instances of co-investigation and related discoveries and achievements in bovine and human immunology; perhaps most interesting is the development of the BCG vaccine, the tuberculin skin test and the more recent interferon-gamma test that were developed first in cattle to prevent and diagnosis bovine tuberculosis and then applied to humans. There are also a number of immune-physiological traits that ruminant share with humans including the development of their immune systems in utero which increases the utility of cattle as a model for human immunology. These are reviewed here with a particular focus on the use of cattle to unravel γδ T cell biology. Based on the sheer number of γδ T cells in this γδ T cell high species, it is reasonable to expect γδ T cells to play an important role in protective immune responses. For that reason alone cattle may provide good models for elucidating at least some of the roles γδ T cells play in protective immunity in all species. This includes fundamental research on γδ T cells as well as the responses of ruminant γδ T cells to a variety of infectious disease situations including to protozoan and bacterial pathogens. The role that pattern recognition receptors (PRR) play in the activation of γδ T cells may be unique relative to αβ T cells. Here we focus on that of the γδ T cell specific family of molecules known as WC1 or T19 in ruminants, which are part of the CD163 scavenger receptor cysteine rich (SRCR) family that includes SCART1 and SCART2 expressed on murine γδ T cells. We review the evidence for WC1 being a PRR as well as an activating co-receptor and the role that γδ T cells bearing these receptors play in immunity to leptospirosis and tuberculosis. This includes the generation of memory responses to vaccines, thereby continuing the tradition of co-discovery between cattle and humans.

Recombinant DNA technology for producing new rinderpest virus vaccines

With few exceptions, vaccination aims to control rather than eliminate or eradicate disease. The eradication of smallpox in the 1970s led to two other human diseases, polio and measles, being targeted for eradication by the World Health Organization. In general, animal diseases are ignored by the public, however, recent targeting of the rinderpest virus, the agent of cattle plague, has put this virus on the verge of global extinction. For centuries, this virus was responsible for major cattle plagues in Europe, Asia and Africa. The success of the Global Rinderpest Eradication Program is an illustration of the power of vaccines to alter people's lives economically and socially when used in an internationally coordinated way. In this review, the history of the development of rinderpest vaccines and the new research being undertaken to produce marker vaccines, using recombinant DNA technology and reverse genetics, are described. In addition, the valuable contribution that marker vaccines can make in the final stages of the rinderpest eradication program is outlined.

Diagnosis and control of peste des petits ruminants: a comprehensive review

Peste des petits ruminants (PPR) is an acute, highly contagious, world organization for animal health (OIE) notifiable and economically important transboundary viral disease of sheep and goats associated with high morbidity and mortality and caused by PPR virus. PPR is considered as one of the main constraints in augmenting the productivity of small ruminants in developing countries and particularly severely affects poor farmer's economy. The disease is clinically manifested by pyrexia, oculo-nasal discharges, necrotizing and erosive stomatitis, gastroenteritis, diarrhoea and bronchopneumonia. The disease can be diagnosed from its clinical signs, pathological lesions, and specific detection of virus antigen/antibodies/genome in the clinical samples by various serological tests and molecular assays. PPR is the one of the priority animal diseases whose control is considered important for poverty alleviation in enzootic countries. Availability of effective and safe live attenuated cell culture PPR vaccines and diagnostics have boosted the recently launched centrally sponsored control programme in India and also in other countries. This review article primarily focus on the current scenario of PPR diagnosis and its control programme with advancement of research areas that have taken place in the recent years with future perspectives.

Rinderpest: the veterinary perspective on eradication

Rinderpest was a devastating disease of livestock responsible for continent-wide famine and poverty. Centuries of veterinary advances culminated in 2011 with the UN Food and Agriculture Organization and the World Organization for Animal Health declaring global eradication of rinderpest; only the second disease to be eradicated and the greatest veterinary achievement of our time. Conventional control measures, principally mass vaccination combined with zoosanitary procedures, led to substantial declines in the incidence of rinderpest. However, during the past decades, innovative strategies were deployed for the last mile to overcome diagnostic and surveillance challenges, unanticipated variations in virus pathogenicity, circulation of disease in wildlife populations and to service remote and nomadic communities in often-unstable states. This review provides an overview of these challenges, describes how they were overcome and identifies key factors for this success.

Rinderpest eradication: appropriate technology and social innovations

Rinderpest is only the second infectious disease to have been globally eradicated. In the final stages of eradication, the virus was entrenched in pastoral areas of the Greater Horn of Africa, a region with weak governance, poor security, and little infrastructure that presented profound challenges to conventional control methods. Although the eradication process was a development activity rather than scientific research, its success owed much to several seminal research efforts in vaccine development and epidemiology and showed what scientific decision-making and management could accomplish with limited resources. The keys to success were the development of a thermostable vaccine and the application of participatory epidemiological techniques that allowed veterinary personnel to interact at a grassroots level with cattle herders to more effectively target control measures.

Evaluation of efficacy of stabilizers on the thermostability of live attenuated thermo-adapted Peste des petits ruminants vaccines

In this study, thermo-adapted (Ta) PPR vaccines were assessed for their stability at 25, 37, 40, 42 and 45°C in lyophilized form using two extrinsic stabilizers {lactalbumin hydrolysate-sucrose (LS) and stabilizer E} and in reconstituted form with the diluents (1 mol/L MgSO(4) or 0.85% NaCl). The lyophilized vaccines showed an expiry period of 24-26 days at 25°C, 7-8 days at 37°C and 3-4 days at 40°C. LS stabilizer was superior at 42°C with a shelf-life of 44 h, whereas in stabilizer E, a 40 h shelf-life with a comparable half-life was observed. At 45°C, the half-life in stabilizer E was better than LS and lasted for 1 day. Furthermore, the reconstituted vaccine maintained the titre for 48 h both at 4°C and 25°C and for 24-30 h at 37°C. As both the stabilizers performed equally well with regard to shelf-life and half-life, the present study suggests LS as stabilizer as a choice for lyophilization with 0.85% NaCl diluent, because it has better performance at higher temperature. These Ta vaccines can be used as alternatives to existing vaccines for the control of the disease in tropical countries as they are effective in avoiding vaccination failure due to the breakdown in cold-chain maintenance, as this vaccine is considerably more stable at ambient temperatures.

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

The live attenuated vaccine against duck viral hepatitis currently available in Korea requires special freezers for storage and transportation with extra costs involved. The development of a lyophilization stabilizer for live attenuated duck viral hepatitis virus (DHV) vaccines, therefore, has been highly recommended for the wider application of the vaccines. Four conventional vaccine stabilizer formulations containing a disaccharide, such as lactose, trehalose, or sucrose, and new formulations containing sorbitol were tested for their efficacy in stabilizing a new attenuated DHV type 3 vaccine candidate under different storage temperatures, 4 and 37 degrees C. The vaccine virus and each stabilizer formulation were combined and submitted to lyophilization and the viability of the virus was measured in 7-d-old specific-pathogen-free chicken embryos by determining the 50% egg lethal dose. Stabilizer formulations containing 2, 4, or 8% sorbitol preserved the viability of the vaccine virus much better than the other stabilizer formulations and 2% sorbitol was the optimal concentration in a standard stabilizing buffer, phosphate glutamate gelatin (0.0038 M KH2PO4, 0.0071 M K2HPO4, 0.0049 M monosodium L-glutamate, and 0.5% gelatin). The results demonstrate that the stabilizer formulation containing 2% sorbitol and 0.5% gelatin can be used for convenient storage and transportation of live DHV vaccines.

Immune protection in animals: the examples of rinderpest and foot-and-mouth disease

Fading immune protection in farmed animals may present a problem, particularly in free-ranging animals in nomadic and transhumant pastoral systems, where animals are not readily available for large-scale blanket vaccination programmes. Two veterinary examples of fading immune protection are discussed: rinderpest and foot-and-mouth disease (FMD). Both are devastating viral diseases of cattle that have a huge impact on the farming economy. Both diseases can be controlled by vaccination, although the post-vaccination immunity afforded by the rinderpest vaccine is markedly different from that induced by FMD vaccines. These differences may in part explain the respective advancement of international eradication campaigns: while global eradication of rinderpest is imminent, FMD viruses are still actively circulating in many parts of the world.

Planning for the progressive control of foot-and-mouth disease worldwide

In the wake of on-going successful programmes for global eradication of rinderpest and the current effort to contain the spread of avian influenza, the progressive world-wide control of FMD must be regarded as a major contribution to the international public good. FMD is the single most animal disease constraint to international trade in animal products. Its control is relevant, on the one hand, to protecting the livestock industries of industrialised countries and, on the other, to the livelihoods and income generation of developing countries, where, as a general rule, FMD continues to be endemic. The strategy that is advocated in this paper is one that is based on progressive risk reduction of FMD in the context of progressive market access of livestock commodities from developing countries. It is suggested that FMD control should be linked to improvement in livelihoods of livestock dependent communities in the FMD endemic settings. It is expected that this in turn will lead to increasing demand for effective national veterinary services and disease surveillance. This strategy has also taken lessons from the global rinderpest eradication programme and regional FMD control programmes in Europe and South America. The strategy that is advocated for the progressive control of FMD in the endemic settings is based on a seven stage process within a horizon of about 30 years, namely: (1) Assessing and defining national FMD status; (2) instituting vaccination and movement control; (3) suppressing virus transmission to achieve absence of clinical disease; (4) achieving freedom from FMD with vaccination in accordance with the OIE standards; (5) achieving freedom from FMD without vaccination in accordance with the OIE standards; (6) extending FMD free zones; and (7) maintaining FMD Freedom. Concomitant with progressive FMD control, there needs be the encouragement of such risk reduction measures as in-country commodity processing in order to encourage regulated trade in livestock commodities without unduly increasing the risk of disease spread. Finally, the progressive control of FMD should also be seen as part of reducing the overall, world-wide threat of infectious diseases to human health and economic development.

Rapid quality control of a live attenuated Peste des petits ruminants (PPR) vaccine by monoclonal antibody based sandwich ELISA

Peste des petits ruminants (PPR) is a highly contagious and economically important viral disease of goats and sheep. A homologous Vero cell-based attenuated PPR vaccine developed in our laboratory and used extensively throughout the country, is available for control of PPR. The presently used quality control test, titration in Vero cells for PPR virus titre in vaccine batches, takes at least 6-8days to determine the quality and dose of vaccine. In this study, 74 freeze-dried PPR vaccine batches were tested simultaneously by both virus titration and PPR sandwich ELISA (S-ELISA) to correlate the titre of the vaccine virus with reactivity in S-ELISA. It was found that the vaccine batches with titre more than 10(3)TCID(50)/ml gave positive results in S-ELISA and correlated well with the virus titre of the freeze-dried vaccines. The correlation coefficient between the virus titration and S-ELISA reactivity was estimated as 0.96, indicating a high correlation between the two parameters based on 74 batches of freeze-dried PPR vaccine. The vaccine batches with titres of 3.0, 4.3, 4.5, 5.0, 6.5 and 7.0 had shown a positive reaction when tested in two-fold dilutions in S-ELISA at 1, 5, 6, 7, 8 and 9log2 titres, respectively. The test vaccine batches were found to be negative in S-ELISA when the titre of the vaccine was less than 10(3)TCID50/ml, suggesting that the vaccine could not be passed for field use. It is concluded that S-ELISA could be a preliminary tool useful for the quality control of PPR vaccine as it is rapid and easy to perform when compared to virus titration.

Evaluation of the xerovac process for the preparation of heat tolerant contagious bovine pleuropneumonia (CBPP) vaccine

The study was conducted with the aim of evaluating the xerovac process as a method for preparing contagious bovine pleuropneumonia (CBPP) vaccine with increased heat resistance. The thermo-protective effects of various concentrations of trehalose in mycoplasma growth medium, various concentrations of trehalose in the dehydration stabilizer and the importance of some divalent cations were assessed. The results obtained indicate that a rapid dehydration of CBPP vaccine following the xerovac method and in an excipient composed of a high concentration of trehalose, renders the product more heat tolerant than a similar vaccine prepared using a regular or an extended freeze drying regime. It was also demonstrated that the addition of chitosan as a mycoplasma precipitating agent conferred additional heat resistance to the vaccine. It is suggested that the application of the xerovac process in the dehydration of CBPP vaccine offers the advantages of a faster, cheaper and easier process over the conventional dehydration methods like freeze drying.

A model of lineage-1 and lineage-2 rinderpest virus transmission in pastoral areas of East Africa

The development of a stochastic, state-transition model of rinderpest transmission dynamics is described using parameter estimates obtained from both laboratory and participatory research. Using serological data, the basic reproduction numbers for lineage-1 rinderpest virus in southern Sudan and for lineage-2 rinderpest virus in Somali livestock were estimated as 4.4 and between 1.2 and 1.9, respectively. The model predictions for the inter-epidemic period in Sudan and Somalia (1.2 and 4.2 years, respectively) were in agreement with analysis of livestock-owner reports (1-2 years and 5 years, respectively).

Comparative efficacy of various chemical stabilizers on the thermostability of a live-attenuated peste des petits ruminants (PPR) vaccine

Thermostability of a live-attenuated peste des petits ruminants (PPR) vaccine recently developed at Indian Veterinary Research Institute was studied using conventional lyophilization conditions. A total of four stabilizers viz., lactalbumin hydrolysate-sucrose (LS), Weybridge medium (WBM), buffered gelatin-sorbitol (BUGS) and trehalose dihydrate (TD) were used to prepare the lyophilized vaccine. The study revealed that the PPR vaccine lyophilized with either LS or TD is more stable than rest of the stabilizers having an expiry period of at least 45 days (so far studied) at 4 degrees C, 15-19 days at 25 degrees C and 1-2 days at 37 degrees C. However, at a temperature of 45 degrees C, BUGS had a marginal superiority, although lasted for few hours, followed by TD and LS with respect to shelf-life, LS and TD with respect to half-life. On the basis of half-life also LS followed by TD appeared superior at a temperature of 4, 25 and 37 degrees C. Reconstitution of vaccine with distilled water or 1M MgSO(4) or 0.85% NaCl maintained the required virus titre (2.5log(10)TCID(50) per dose) up to 8h at 37 degrees C and 7h at 45 degrees C. Among the three diluents, 1M MgSO(4) appeared to be the better diluent for reconstitution of lyophilized PPR vaccine, as the loss on dilution was lowest and maintain the required virus titre for a longer period. Investigation suggests for using LS as stabilizer for lyophilization and 1M MgSO(4) as vaccine diluent for the newly developed PPR vaccine.

Oral immunization of cattle with hemagglutinin protein of rinderpest virus expressed in transgenic peanut induces specific immune responses

Rinderpest is an acute, highly contagious often fatal disease of large and small ruminants, both domestic and wild. Global eradication of rinderpest needs a robust, safe and cost-effective vaccine. The causative agent, rinderpest virus (RPV) is an important member of the genus Morbillivirus in the Paramyxoviridae family. We have generated transgenic peanut (Arachis hypogea L.) plants expressing hemagglutinin protein of RPV and report here, the induction of immune responses in cattle following oral feeding with transgenic leaves expressing hemagglutinin protein without oral adjuvant. Hemagglutinin-specific antibody was detected in the serum as confirmed by immunohistochemical staining of virus-infected cells, and in vitro neutralization of virus infectivity. Oral delivery also resulted in cell-mediated immune responses.

Long-term sterilizing immunity to rinderpest in cattle vaccinated with a recombinant vaccinia virus expressing high levels of the fusion and hemagglutinin glycoproteins

Rinderpest is an acute and highly contagious viral disease of ruminants, often resulting in greater than 90% mortality. We have constructed a recombinant vaccinia virus vaccine (v2RVFH) that expresses both the fusion (F) and hemagglutinin (H) genes of rinderpest virus (RPV) under strong synthetic vaccinia virus promoters. v2RVFH-infected cells express high levels of the F and H glycoproteins and show extensive syncytium formation. Cattle vaccinated intramuscularly with as little as 10(3) PFU of v2RVFH and challenged 1 month later with a lethal dose of RPV were completely protected from clinical disease; the 50% protective dose was determined to be 10(2) PFU. Animals vaccinated with v2RVFH did not develop pock lesions and did not transmit the recombinant vaccinia virus to contact animals. Intramuscular vaccination of cattle with 10(8) PFU of v2RVFH provided long-term sterilizing immunity against rinderpest. In addition to being highly safe and efficacious, v2RVFH is a heat-stable, inexpensive, and easily administered vaccine that allows the serological differentiation between vaccinated and naturally infected animals. Consequently, mass vaccination of cattle with v2RVFH could eradicate rinderpest.

Recombinant hemagglutinin protein of rinderpest virus expressed in insect cells induces humoral and cell mediated immune responses in cattle

Rinderpest virus causes a highly contagious and often fatal disease in domestic and wild ruminants. The surface glycoproteins, hemagglutinin (H) and fusion (F) proteins of this enveloped virus are known to confer protective immunity in cattle. We have reported the generation of a recombinant baculovirus expressing H protein and studied its protective properties in cattle. In this report, we demonstrate that the recombinant baculovirus encoded H protein expressed in insect cells gets incorporated into extracellular baculovirus. Single administration of low doses of purified recombinant extracellular virus with or without adjuvant induces virus neutralizing antibody responses and bovine leukocyte antigen (BoLA) class II restricted helper T cell responses in cattle.

Xerovac: an ultra rapid method for the dehydration and preservation of live attenuated Rinderpest and Peste des Petits ruminants vaccines

The accepted procedure for the long-term preservation of live viruses and bacteria in vaccines has been lyophilisation. We show that thermolabile viruses can be dehydrated in vitro, within 18 h, in an excipient containing trehalose. We further demonstrate that in the resulting dehydrated state, where the viruses are captive in a metastable glass composed of trehalose, they are capable of resisting 45 degrees C for a period of 14 days with minimal loss of potency. The degree of thermotolerance achieved matches that of current 'thermostable' lyophilised vaccines, but with the distinct advantage of a shorter, cheaper and simpler process. The development and utilisation of this process can make significant improvements in current live virus vaccine production. It presents a further step away from dependence on mandatory low temperature refrigerated storage and could lead to greater confidence in vaccine stability, potency and efficacy.

Protection of cattle against rinderpest by intranasal immunisation with a dry powder tissue culture vaccine

Dry powder tissue culture rinderpest vaccine containing 10(2.5) TCID(50) of virus per dose administered intranasally to cattle induced high titre circulating antibody responses and protection against challenge with a virulent strain of rinderpest virus. A reduction in the dose of virus to 10(1.1) TCID(50) resulted in a failure to elicit detectable antibody responses and a lack of protection. Intranasal powder vaccine offers several advantages over conventional needle-administered aqueous rinderpest vaccine, including greater stability in the absence of a cold chain, reduced risk of 'needle transfer' of other microbial agents present in the vaccinated herd and lower cost.

Rinderpest: the disease and its impact on humans and animals

Rinderpest is an ancient plague of cattle and other large ruminants, with descriptions of its effects dating back to Roman times. It is caused by a morbillivirus closely related to human measles virus. Although a very effective vaccine is available, it is heat labile, and logistical and financial problems hamper its delivery to the remote areas of Africa and Asia where enzootic foci remain. Periodic epizootics emerge from these foci and spread into neighboring areas, mainly as a result of uncontrolled livestock movement and trading. This is particularly true during wars or civil disturbances when normal veterinary controls do not operate. The disease continues to cause devastating economic losses in domestic livestock in areas of the world where it remains endemic.

Comparative ethnoveterinary and serological evaluation of the Karimojong Community Animal Health Worker Program in Uganda

The Karimojong CAHW program, in which members of the pastoral Karimojong community were trained as basic veterinary care providers, was evaluated using ethnoveterinary techniques. A serological study of rinderpest antibody titers was also completed to compare serological results with ethnoveterinary results in the case of one disease, rinderpest. An outbreak of rinderpest-like disease that occurred during the field phase of the study was also investigated. The results show that rinderpest does exist in Karamoja in an apparently endemic form. Given the significant value placed by Karimojong herders on vaccinated animals, it can be concluded that they would adequately vaccinate their herds if they could trust the vaccine and the vaccinator. Discrepancies between ethnoveterinary and serological results show that ethnoveterinary techniques do not provide numerically accurate data concerning protection from disease, but that they can, nonetheless, provide basic, cost effective indications of disease patterns.

Immunogenic and protective properties of haemagglutinin protein (H) of rinderpest virus expressed by a recombinant baculovirus

The hemagglutinin (H) protein of Rinderpest virus expressed by a recombinant baculovirus used as a vaccine produced high titres of neutralizing antibody to Rinderpest virus in the vaccinated cattle, comparable to the levels produced by live attenuated vaccine. The immunized cattle were protected against a vaccine-virus challenge, as demonstrated by the failure of development of antibodies to N protein of the vaccine virus. The lack of replication of vaccine virus in the immunized cattle indicated that they are capable of showing a protective response if challenged with a virulent virus.

Potency testing of tissue culture rinderpest vaccine in rabbits

Rinderpest (RP) vaccine potency testing requires virulent bovine rinderpest virus (RPV). Use of virulent RPV is a biosafety hazard. In this study we had vaccinated rabbits with tissue culture RP vaccine at different doses and thereafter challenged with lapinized virus. No thermal reaction in vaccinated rabbits was observed. Serum neutralizing antibody response to vaccine was dose dependent until the second week post-vaccination but by the fourth week post-vaccination all the rabbits had similar neutralizing antibody titres. Vaccinated rabbits exhibited mild clinical signs as compared to unvaccinated controls after challenge. All the vaccinated rabbits survived challenge while only 40% unvaccinated rabbits survived challenge with virulent lapinized RPV. A strong anamnestic response in all the vaccinated rabbits was observed after challenge with lapinized virus. This study shows that rabbits could be used for potency testing of RP vaccine virus.

Rinderpest and other animal morbillivirus infections: comparative aspects and recent developments

The genus morbillivirus presently comprises measles virus of man, rinderpest virus (RPV), peste des petits ruminants virus (PPRV), and canine distemper virus (CDV). 'Emerging' morbilliviruses, such as phocid distemper virus (PDV) of seals, dolphin (DMV) and porpoise morbillivirus (PMV) have probably been present for a long period of time and outbreaks are possibly related to introduction into a highly susceptible population and/or be the result of interspecies transmission. In this review some comparative aspects of morbillivirus infections, particularly with respect to rinderpest and canine distemper viruses, are presented. Topics include pathogenesis, epidemiology, molecular phylogeny, diagnosis and prophylaxis. Recent developments in molecular biology have created tools which have enabled us to achieve a better understanding of morbillivirus infections at the nucleic acid level ('molecular epidemiology') while recombinant DNA technology has allowed new bivalent recombinant vaccines with improved heat stability to be produced.

The use of thermostable Vero cell-adapted rinderpest vaccine as a heterologous vaccine against peste des petits ruminants

The thermostable Vero cell-adapted rinderpest vaccine was evaluated in terms of immunogenicity as a heterologous vaccine against peste des petits ruminants. A titration to establish the minimum immunising dose was performed in American mixed breed goats by vaccinating test subjects with dilutions of Vero cell-adapted rinderpest vaccine and then challenging 26 days later with virulent peste des petits ruminants virus. All animals were followed for virus neutralising antibodies against both rinderpest and peste des petits ruminants virus after vaccination and challenge. The antibody response to vaccination was primarily against rinderpest virus with very low levels of cross-reactivity to peste des petits ruminants virus. Following challenge, animals which possessed anti-rinderpest neutralising antibodies remained clinically normal but mounted strong anti-peste des petits ruminants virus neutralising antibody responses indicating that replication of challenge virus took place without the induction of illness. The 50 per cent minimum goat immunising dose was 3 tissue culture infectious doses 50 per cent (TCID50) as established by serological response and protection against challenge. The thermostable Vero cell-adapted rinderpest vaccine is a suitable immunogen for the protection of goats against peste des petits ruminants.

The serological response to a thermostable Vero cell-adapted rinderpest vaccine under field conditions in Niger

A lyophilized thermostable Vero cell-adapted ringerpest vaccine, stabilized with lactalbumin hydrolysate and sucrose, was tested for safety, serological response and suitability for use with an abbreviated cold chain under field conditions in Niger. A total of 480 cattle, 90 goats and 55 sheep of unknown serological status were vaccinated on government ranches and observed for at least 22 days. No untoward effects of the vaccine were detected. The serological response to the vaccine stored at environmental temperatures for 30 to 34 days was determined in 144 previously unvaccinated yearling calves. Seroconversion was demonstrated in 98% of the yearling calves using seroneutralization. The un-refrigerated vaccine retained a titer of 3.69 log10 TCID50 per dose through day 34.