Effect of thimerosal concentration on the efficacy of inactivated Newcastle disease oil-emulsion vaccines

Different quantities of the preservative thimerosal in inactivated Newcastle disease oil-emulsion vaccines were tested to determine the influence on the hemagglutination-inhibition (HI) response of broilers. The effect of thimerosal was measured in vaccines that had been stored for 1, 21, and 52 weeks; HI serology was conducted at 2, 4, and 6 weeks after vaccination. Mean HI titers 4 weeks after vaccination decreased at a significant rate (P less than or equal to 0.001) with increasing concentrations of thimerosal. HI titers 4 weeks after vaccination with 1-week-old vaccine were significantly (P less than or equal to 0.05) higher than those after vaccination with 52-week-old vaccine at all thimerosal concentrations tested. Titers were also significantly higher (P less than or equal to 0.05) after vaccination with 1-week-old vaccine than after vaccination with 21-week-old vaccine at all thimerosal concentrations below about 8.25 mg/ml of antigen. Thimerosal at the levels recommended in commercial vaccines does not significantly decrease vaccine efficacy.     

The preparation and efficacy of manually emulsified Newcastle disease oil-emulsion vaccines

Experimental Newcastle disease oil-emulsion vaccines were prepared by manually shaking small quantities of antigen, surfactant, and mineral oil and compared with oil-emulsion vaccines made by the more conventional mechanical methods. Emulsion stability (prolonged emulsification of aqueous antigen) of the manually prepared vaccines was achieved by four different processes and tested for efficacy in broilers. White rock broilers were vaccinated at 3-5 weeks of age and bled at 1- to 2 week intervals thereafter for 8 weeks. Cumulative 8-week hemagglutination-inhibition (HI) mean titers (reciprocals) ranged from 15 to 250 for manually emulsified vaccines and from 18 to 240 for mechanically emulsified vaccines. Eight-week cumulative mean HI responses induced by manually emulsified vaccines were never significantly (P less than 0.05) lower than their specific mechanically emulsified comparison vaccines and were occasionally significantly higher. Highest HI titers were induced when hydrophile-lipophile balances of 7, 9, and 6 were used for the preparation of manually emulsified vaccines. In general, most of the vaccine emulsions were stable for more than 30 days. Vaccine efficacy, however, was not always diminished by poor emulsion stability. These results indicate that manual emulsification can be used for the production of oil-emulsion vaccines of high efficacy that can provide benefits over existing mechanical methods.     

两株新城疫病毒野毒株的免疫原性研究

本研究对两株新城疫病毒(NDV)野毒株制备的灭活疫苗的免疫原性进行了评估,结果表明NDV GM株和JM株制备的油乳剂灭活疫苗对鸡均具有良好的免疫原性。GM株和JM株油苗免疫组的抗体消长规律与Ulster2C、LaSota、Clone30株油苗免疫组无显著性差异,与Mukteswar株油苗免疫组具有显著差异。GM和JM、Ulster 2C株之间具有较好的免疫交叉保护性,使用这3个病毒株的油乳剂灭活苗进行免疫均能保护GM株强毒的攻击。但在相同HI滴度下,GM株油苗免疫组比其它两个病毒株的油苗免疫组更能够有效的抵抗强毒的攻击。     

Influence of formulation on the efficacy of experimental oil-emulsion Newcastle disease vaccines

Twenty-one experimental oil-emulsion vaccines with different emulsifier contents, aqueous-to-oil ratios, and antigen concentrations were compared by immunization of 4-week-old chickens. Vaccines that contained oil-phase (Arlacel 80) and aqueous-phase (Tween 80) emulsifiers induced 2-to-4-fold higher hemagglutination-inhibition titers than vaccines with only the oil-phase emulsifier. The emulsion vaccines containing both emulsifiers were also more stable at 37 C and less viscous than those containing only the oil-phase emulsifier. Vaccines that had different aqueous-to-oil ratios and contained different quantities of allantoic-fluid antigen (1.2% to 50% of the vaccine volume) induced similar protection against challenge, but hemagglutination-inhibition titers were proportional to the amount of antigen added. Vaccines that had different aqueous-to-oil ratios but contained equal amounts of antigen induced similar hemagglutination-inhibition titers and similar protection against challenge.     

Efficacy of experimental Newcastle disease water-in-oil oil-emulsion vaccines formulated from squalane and squalene

Water-in-oil inactivated Newcastle disease oil-emulsion vaccines were formulated with the terpene oils squalane or squalene, or mixtures thereof, and injected into 4-week-old broilers. Vaccine efficacy based on hemagglutination-inhibition (HI) titers was comparable to that of control mineral oil vaccines. Tissue reaction to intramuscular injection of the terpene oil emulsion vaccines was greatly reduced 3 weeks post-vaccination compared with that of mineral oil-based vaccine. Viscosity of the terpene oil vaccines was satisfactory but increased three to four times that of mineral oil vaccine when the antigen phase volume increased from 5% to 20%.     

Vaccination of day-old broiler chicks against Newcastle disease and infectious bursal disease using commercial live and/or inactivated vaccines

Day-old broilers were administered live and/or inactivated vaccines to assess vaccine efficacy against challenge with Newcastle disease (ND) and infectious bursal disease (IBD). Chicks were from commercial breeder pullets vaccinated against ND and IBD using several live vaccine primers followed by an inactivated ND-IBD vaccine at 18 weeks. The most efficacious initial ND-IBD vaccination program was live ND virus by eye drop and live IBD vaccine injected subcutaneously (SQ) followed 2 hours later with inactivated ND-IBD vaccine SQ. The next two most efficacious programs were live vaccine alone and the inactivated vaccine only. Inactivated vaccine given SQ had no adverse effect on live IBD vaccine given 2 hours earlier in a similar site. Administration of inactivated vaccine by vent was not as efficacious as administration SQ. A booster of a second live ND-IBD vaccine drinking water at 18 days significantly increased levels of circulating antibody, regardless of the initial vaccination program.     

Efficacy of viable and inactivated Newcastle disease virus vaccines in turkeys

Market turkeys spray-vaccinated at 20 days of age with viable Newcastle disease virus (NDV) vaccine and challenged 7 weeks postvaccination failed to yield NDV by tracheal swabbing 4 days postchallenge but demonstrated serologic evidence of infection. Birds vaccinated subcutaneously with inactivated oil-emulsion (OE) NDV vaccine had virologic and serologic evidence of infection. Breeder hens vaccinated by spray with commercial La Sota vaccine at 19 weeks of age and revaccinated subcutaneously with OE vaccine at 32 weeks of age had an adequate level of resistance against a drop in egg production but demonstrated serologic evidence of infection when challenged with velogenic NDV at 38 weeks of age.     

Efficacy of oil-emulsion vaccines prepared with pigeon paramyxovirus-1, Ulster, and La Sota Newcastle disease viruses

Three strains of avian paramyxovirus-1 virus (PMV-1) were used to prepare four experimental monovalent oil-emulsion vaccines. A pigeon PMV-1 isolate (PPMV-1) and the Newcastle disease virus strains La Sota and Ulster were used to prepare four pools of beta-propiolactone-inactivated allantoic fluid for the vaccines. Groups of susceptible white rock chickens and racing homing pigeons were vaccinated subcutaneously with one of the vaccines, and their serologic responses were determined using the hemagglutination-inhibition (HI) test at frequent intervals up to 9 weeks postvaccination. Pigeons were challenged after 10 weeks with a virulent PPMV-1 isolate given intravenously, observed for signs of disease for 5 weeks, and then tested for secondary serologic HI responses. The HI responses were measured using the three strains of virus as HI test antigens. The titers were generally greater when the hemagglutination antigen used in the test was homologous with the antigen used to prepare the vaccine. All vaccines protected pigeons against morbidity and death but not against infection with the challenge virus. The shedding of PPMV-1 challenge virus from PPMV-1 vaccinates was greatly reduced 6 days after challenge.     

Determination of hemagglutination activity recovered from oil-emulsion Newcastle disease vaccines as a prediction of efficacy

Hemagglutination (HA) activity was recovered from the aqueous phases of commercially and experimentally prepared oil-emulsion (OE) Newcastle disease virus (NDV) vaccines using two methods: aqueous partition and freeze-thaw. Quantitation of the HA activity retrieved by the aqueous partition technique was directly related to the degree of protection conferred to chickens against a strain of velogenic viscerotropic (VV) NDV in nine of the ten vaccines analyzed. One of the ten vaccines yielded high levels of retrieved HA activity but induced low hemagglutination-inhibition (HI) antibody levels and low levels of protection. Therefore, the retrieval and quantitation of HA activity from OE NDV vaccines using the partition technique provides a useful adjunct to vaccine testing methods that doesn't require vaccination and challenge trials. The freeze-thaw method did not yield measurable HA titers for all vaccines with high efficacy, so its use should be restricted to only those vaccines for which it has been demonstrated to be suitable.     

Optimization of hydrophile-lipophile balance for improved efficacy of Newcastle disease and avian influenza oil-emulsion vaccines

Preparations of inactivated Newcastle disease (ND) and avian influenza (AI) oil-emulsion vaccines with surfactant hydrophile-lipophile-balance (HLB) values between 4.3 and 9.5 were evaluated for their efficacy in broiler-type white rock chickens. Chickens were vaccinated at 3-4 weeks of age and bled at 2-week intervals over 8 weeks. Post-vaccinal hemagglutination-inhibition (HI) geometric mean titers (reciprocals) ranged from 197 to 485 for ND vaccines and from 184 to 1040 for AI vaccines. Based on the HI response, an HLB value of 7.0 induced the greatest stimulation of antibody titers. Ten percent surfactant in the oil phase of the vaccines induced maximum titers at this HLB. The oil:aqueous ratios of the vaccines did not greatly influence the overall serologic response when the vaccines had an HLB of 7.0. These results indicate that manipulating surfactant HLB values of OE vaccine may maximize the HI response in broilers.     

Comparison of flagellin and an oil-emulsion adjuvant in inactivated Newcastle disease vaccine in stimulation of immunogenic parameters

The present study was designed to investigate the potential application of native (N) and recombinant (truncated modified [tmFliC] and full-length [flFliC]) flagellin proteins along with inactivated Newcastle disease virus (NDV). Fifty six SPF chickens were immunized twice with PBS (control), inactivated NDV (Ag), inactivated NDV/flFliC (AgF), inactivated NDV/tmFliC (AgT), inactivated NDV/N (AgN), commercial vaccine containing Montanide (Vac) and Vac/N (VacN), with a two-week interval. Blood was collected weekly and spleens were harvested after chickens were sacrificed. Interleukin-6 (IL-6) and tumor necrotic factor-α (TNF-α) gene expression in peripheral blood mononuclear cells were analyzed by Real-Time PCR. Antibody response was assessed by haemagglutination inhibition (HI). Cellular activity was quantified by MTT assay. Results showed that the most IL-6 and TNF-α gene expression was observed in AgF group (P < 0.01). The lowest gene expression among vaccinated groups was observed in Ag group for IL-6 and Ag and Vac group for TNF-α. The highest HI titer was observed in Vac, VacN, AgF and AgT groups. The AgF group showed the highest cellular activity (P < 0.01). In conclusion, flagellin-adjuvanted groups showed a pro-inflammatory effect and acted similarly to or better than the Vac group. Hence, flagellin can be proposed as a potential adjuvant for ND vaccine.     

Antibody response of kori bustards (Ardeotis kori) and houbara bustards (Chlamydotis undulata) to live and inactivated Newcastle disease vaccines.

Adult houbara bustards (Chlamydotis undulata) and juvenile kori bustards (Ardeotis kori) were given four regimens of commercially available inactivated and live poultry paramyxovirus type 1 (PMV-1) vaccines. Immunologic response to vaccination was assessed by hemagglutination inhibition assay of serum. Kori bustards, to which a dose of 0.5 ml of a commercially available inactivated vaccine for poultry had been administered intramuscularly (0.15 ml/kg body weight), failed to develop hemagglutinating antibodies, but antibody titers of low intensity and duration were detected following administration of a second and third subcutaneous dose of 2.0 ml vaccine per bird (0.40-0.45 ml/kg). In subsequent trials, when inactivated vaccine was administered subcutaneously at 1.0 ml/kg body weight following two or four live vaccinations administered by the ocular route, juvenile kori bustards developed higher, more persistent titers of antibodies. Kori bustards given four live vaccinations followed by inactivated vaccine developed higher titers of longer duration compared with kori bustards given two live vaccines followed by inactivated vaccine. Antibody titers of kori bustards given inactivated vaccine were higher and more persistent than the antibody response to live vaccination. Houbara bustards, previously vaccinated with inactivated vaccine, that were given a booster dose of inactivated vaccine maintained high mean antibody titers (> or = log, 5) for 52 wk. The authors recommend that inactivated PMV-1 vaccine should be administered by subcutaneous injection of 1.0 ml/kg vaccine to bustards. Adult bustards, previously vaccinated with inactivated vaccine, should be vaccinated annually with inactivated vaccine. Juvenile bustards should receive a second dose of inactivated vaccine 4-6 mo after the first dose of inactivated vaccine. Even though inactivated PMV-1 vaccines induced hemagglutination inhibition antibodies and produced no adverse reactions, further studies will be required to determine the protective efficacy of the antibody.     

Vaccination of pigs against Aujeszky's disease by the intradermal route using live attenuated and inactivated virus vaccines.

Inactivated and live Aujeszky's disease virus vaccines were administered intradermally using a special device without a needle. The 88 pigs were vaccinated at the beginning of the fattening period, both under experimental conditions and in commercial herds. All the pigs were challenged at the end of the fattening period in isolation units. The same vaccines were also injected intramuscularly. Vaccination by the intradermal route induced good protection, similar to that conferred with live virus vaccine injected intramuscularly. The inactivated virus vaccine was not as effective when it was injected by the intradermal route. In animals vaccinated intradermally, there were no local lesions in the meat, but very small nodules were found in the dermis; these do not affect carcass quality. The effects of challenge exposure depended on the initial health of the animals, and a synthetic value (delta G) was used to interpret the data. In fattening pigs, intradermal vaccination required less animal constraint than intramuscular injection; administration could be verified by the presence of a papule at the site of inoculation, and pigs could be vaccinated while they were feeding. Injection without a needle also helps avoid bacterial contamination under farm conditions.     

Vaccination of pigs against Aujeszky's disease by the intradermal route using live attenuated and inactivated virus vaccines

A study was undertaken of the protection induced by inactivated and live Aujeszky's disease virus vaccines. The vaccines were administered using a special device which, without the use of a needle, delivered the preparation intradermally. The trials were performed on 88 pigs which were vaccinated at the beginning of the fattening period both in experimental conditions and in pig herds. All the pigs were challenged at the end of the fattening period in isolation units. The results obtained were compared with those obtained using the same vaccines injected intramuscularly. It was shown that vaccination via the intradermal route induced good protection in the vaccinated animals and was similar to that conferred by live virus vaccine injected intramuscularly. The results, with the inactivated virus vaccine, were not so good when it was injected via the intradermal route. Studies with intradermal vaccination showed no local lesion or very small nodules strictly localized to the dermis. The results also confirmed that the effects of challenge exposure depended on the health status of animals prior to infection and show the necessity to use a synthetic value (delta G) to interpret the data and mainly to compare the results objectively. In fattening pigs this vaccination procedure is attractive because (i) less animal constraint is needed than would be for intramuscular injections, (ii) injection can be checked by the presence of a visible papula at the site of inoculation and, (iii) pigs can be vaccinated in the ham while they are feeding. Injection without a needle also contributes to avoiding bacterial contamination under practical farm conditions of vaccination.     

Thermostable Newcastle disease vaccines in Tanzania.

The V4 thermostable Newcastle disease vaccine was tested under village conditions in Central Tanzania. The vaccination regimes were four vaccinations by eye drop (eye drop group), one vaccination by eye drop followed by three vaccinations by drinking water (drinking water group), one vaccination by eye drop followed by three vaccinations with vaccine supplied on boiled sorghum (food vaccine group) and no vaccine (control group). Antibody responses in the eye drop and drinking water groups suggested that at least 70% of the chickens would be protected against challenge with virulent virus. In both groups, eight of the 11 chickens survived laboratory challenge. Only three of the 11 chickens in the food vaccine group resisted challenge, and none of the 10 control chickens.