Use of a tetanus toxoid marker to allow differentiation of infected from vaccinated poultry without affecting the efficacy of a H5N1 avian influenza virus vaccine

Tetanus toxoid (TT) was assessed as a positive marker for avian influenza (AI) virus vaccination in chickens, in a vaccination and challenge study. Chickens were vaccinated twice with inactivated AI H5N2 virus vaccine, and then challenged three weeks later with highly pathogenic AI H5N1 virus. Vaccinated chickens were compared with other groups that were either sham-vaccinated or vaccinated with virus with the TT marker. All sham-vaccinated chickens died by 36 hours postinfection, whereas all vaccinated chickens, with or without the TT marker, were protected from morbidity and mortality following exposure to the challenge virus. Serological testing for H5-specific antibodies identified anamnestic responses to H5 in some of the vaccinated birds, indicating active virus infection.     

Improvements to the hemagglutination inhibition test for serological assessment of recombinant fowlpox-H5-avian-influenza vaccination in chickens and its use along with an agar gel immunodiffusion test for differentiating infected from noninfected vaccinated animals

In general, avian influenza (AI) vaccines protect chickens from morbidity and mortality and reduce, but do not completely prevent, replication of wild AI viruses in the respiratory and intestinal tracts of vaccinated chickens. Therefore, surveillance programs based on serological testing must be developed to differentiate vaccinated flocks infected with wild strains of AI virus from noninfected vaccinated flocks in order to evaluate the success of vaccination in a control program and allow continuation of national and international commerce of poultry and poultry products. In this study, chickens were immunized with a commercial recombinant fowlpox virus vaccine containing an H5 hemagglutinin gene from A/turkey/Ireland/83 (H5N8) avian influenza (AI) virus (rFP-H5) and evaluated for correlation of immunological response by hemagglutination inhibition (HI) or agar gel immunodiffusion (AGID) tests and determination of protection following challenge with a high pathogenicity AI (HPAI) virus. In two different trials, chickens immunized with the rFP-H5 vaccine did not develop AGID antibodies because the vaccine lacks AI nucleoprotein and matrix genes, but 0%-100% had HI antibodies, depending on the AI virus strain used in the HI test, the HI antigen inactivation procedure, and whether the birds had been preimmunized against fowlpox virus. The most consistent and highest HI titers were observed when using A/turkey/Ireland/83 (H5N8) HPAI virus strain as the beta-propiolactone (BPL)-inactivated HI test antigen, which matched the hemagglutinin gene insert in the rFP-H5 vaccine. In addition, higher HI titers were observed if ether or a combination of ether and BPL-inactivated virus was used in place of the BPL-inactivated virus. The rFP-H5 vaccinated chickens survived HPAI challenge and antibodies were detected by both AGID and HI tests. In conclusion, we demonstrated that the rFP-H5 vaccine allowed easy serological differentiation of infected from noninfected birds in vaccinated populations of chickens when using standard AGID and HI tests.     

Avian influenza mucosal vaccination in chickens with replication-defective recombinant adenovirus vaccine

We evaluated protection conferred by mucosal vaccination with replication-competent adenovirus-free recombinant adenovirus expressing a codon-optimized avian influenza (AI) H5 gene from A/turkey/WI/68 (AdTW68.H5ck). Commercial, layer-type chicken groups were either singly vaccinated ocularly at 5 days of age, singly vaccinated via spray at 5 days of age, or ocularly primed at 5 days and ocularly boosted at 15 days of age. Only chickens primed and boosted via the ocular route developed AI systemic antibodies with maximum hemagglutination inhibition mean titers of 3.9 log2 at 32 days of age. In contrast, single vaccination via the ocular or spray routes maintained an antibody status similar to unvaccinated controls. All chickens (16/16) subjected to ocular priming and boosting with AdTW68.H5ck survived challenge with highly pathogenic AI virus A/chicken/Queretaro/14588-19/95 (H5N2). Single ocular vaccination resulted in 63% (10/16) of birds surviving the challenge followed by a 44% (7/16) survival of single-sprayed vaccinated birds. Birds vaccinated twice via the ocular route also showed significantly lower (P < 0.05) AI virus RNA concentrations in oropharyngeal swabs compared to unvaccinated-challenged controls.     

Protective efficacy of H5 inactivated vaccines in meat turkey poults after challenge with Egyptian variant highly pathogenic avian influenza H5N1 virus

In contrast to chickens, there is a paucity of information on the potency of H5 vaccines to protect turkeys against the highly pathogenic avian influenza (HPAI) H5N1 virus infections. In this study, 4 groups, 10 turkey poults each, were vaccinated at seven days old with one of H5N2 or H5N1 commercial vaccines or one of two prepared H5N1 vaccines from a local Egyptian variant HPAI H5N1 (EGYvar/H5N1) strain. At 35 days age, all vaccinated and 10 non vaccinated birds were challenged intranasal with 10(6) EID(50)/0.1 ml of EGYvar/H5N1. All vaccines used in this study were immunogenic in turkeys. There was no cross reaction between the commercial vaccines and the Egyptian variant H5N1 antigen as obtained by the hemagglutination inhibition test. Birds vaccinated with H5N2 vaccine were died, while other H5N1 vaccinated groups have had 20-40% mortality. The highest virus excretion was found in non-vaccinated infected and H5N2 vaccinated birds. Eleven peculiar amino acid substitutions in H5 protein of the variant strain were existed neither in the vaccine strains nor in the earliest H5N1 virus introduced into Egypt in 2006. In conclusion, single vaccination at seven days old is inadequate for protection of meat turkeys against variant HPAI H5N1 challenge and multi-dose vaccination at older age is recommended. For the foreseeable future, continuous evaluation of the current vaccines in H5N1 endemic countries in the face of virus evolution is a paramount challenge to mitigate the socio-economic impact of the virus.     

Avian influenza in ovo vaccination with replication defective recombinant adenovirus in chickens: vaccine potency, antibody persistence, and maternal antibody transfer

Protective immunity against avian influenza (AI) can be elicited in chickens in a single-dose regimen by in ovo vaccination with a replication-competent adenovirus (RCA)-free human adenovirus serotype 5 (Ad)-vector encoding the AI virus (AIV) hemagglutinin (HA). We evaluated vaccine potency, antibody persistence, transfer of maternal antibodies (MtAb), and interference between MtAb and active in ovo or mucosal immunization with RCA-free recombinant Ad expressing a codon-optimized AIV H5 HA gene from A/turkey/WI/68 (AdTW68.H5(ck)). Vaccine coverage and intrapotency test repeatability were based on anti-H5 hemagglutination inhibition (HI) antibody levels detected in in ovo vaccinated chickens. Even though egg inoculation of each replicate was performed by individuals with varying expertise and with different vaccine batches, the average vaccine coverage of three replicates was 85%. The intrapotency test repeatability, which considers both positive as well as negative values, varied between 0.69 and 0.71, indicating effective vaccination. Highly pathogenic (HP) AIV challenge of chicken groups vaccinated with increasing vaccine doses showed 90% protection in chickens receiving > or = 10(8) ifu (infectious units)/bird. The protective dose 50% (PD50) was determined to be 10(6.5) ifu. Even vaccinated chickens that did not develop detectable antibody levels were effectively protected against HP AIV challenge. This result is consistent with previous findings ofAd-vector eliciting T lymphocyte responses. Higher vaccine doses significantly reduced viral shedding as determined by AIV RNA concentration in oropharyngeal swabs. Assessment of antibody persistence showed that antibody levels of in ovo immunized chickens continued to increase until 12 wk and started to decline after 18 wk of age. Intramuscular (IM) booster vaccination with the same vaccine at 16 wk of age significantly increased the antibody responses in breeder hens, and these responses were maintained at high levels throughout the experimental period (34 wk of age). AdTW68.H5(ch)-immunized breeder hens effectively transferred MtAb to progeny chickens. The level of MtAb in the progenies was consistent with the levels detected in the breeders, i.e., intramuscularly boosted breeders transferred higher concentrations of antibodies to the offspring. Maternal antibodies declined with time in the progenies and achieved marginal levels by 34 days of age. Chickens with high maternal antibody levels that were vaccinated either in ovo or via mucosal routes (ocular or spray) did not seroconvert. In contrast, chickens without MtAb successfully developed specific antibody levels after either in ovo or mucosal vaccination. These results indicate that high levels of MtAb interfered with active Ad-vectored vaccination.     

Needle-free delivery of an inactivated avian influenza H5N3 virus vaccine elicits potent antibody responses in chickens

A needle-free delivery system was assessed as a route for providing quick, safe, and effective vaccination against avian influenza (AI). Two groups of chickens were vaccinated with a commercially available inactivated H5N3 virus vaccine delivered either with a needle-free device or with the conventional syringe-and-needle method recommended by the vaccine manufacturer. The kinetic aspects of seroconversion, peak antibody levels, and antibody titers were measured by a combination of an indirect enzyme-linked immunosorbent assay and the hemagglutination-inhibition test and were all found to be similar in the 2 groups of chickens. We conclude that the needle-free delivery system could result in effective immunization against H5N1 AI epidemics and pandemics in chickens.     

In vivo evaluation of vaccine efficacy against challenge with a contemporary field isolate from the α cluster of H1N1 swine influenza virus

Influenza A virus vaccines currently contain a mixture of isolates that reflect the genetic and antigenic characteristics of the currently circulating strains. This study was conducted to evaluate the efficacy of a trivalent inactivated swine influenza virus vaccine (Flusure XP) in pigs challenged with a contemporary α-cluster H1N1 field isolate of Canadian swine origin. Pigs were allocated to vaccinated, placebo, and negative-control groups and monitored for respiratory disease for 5 d after challenge. On the challenge day and 5 d after challenge the serum of the vaccinated pigs had reciprocal hemagglutination inhibition antibody titers 40 for all the vaccine viruses but ≤ 20 for the challenge virus. Gross lesions were present in the lungs of all pigs that had been inoculated with the challenge virus, but the proportion of lung tissue consolidated did not differ significantly between the placebo and vaccinated pigs. However, the amount of virus was significantly reduced in the nasal secretions, lungs, and bronchoalveolar lavage fluid in the vaccinated pigs compared with the placebo pigs. These results indicate that swine vaccinated with Flusure XP were partially protected against experimental challenge with a swine α-cluster H1N1 virus that is genetically similar to viruses currently circulating in Canadian swine.     

Experimental study to determine if low-pathogenicity and high-pathogenicity avian influenza viruses can be present in chicken breast and thigh meat following intranasal virus inoculation

Two low-pathogenicity (LP) and two high-pathogenicity (HP) avian influenza (AI) viruses were inoculated into chickens by the intranasal route to determine the presence of the AI virus in breast and thigh meat as well as any potential role that meat could fill as a transmission vehicle. The LPAI viruses caused localized virus infections in respiratory and gastrointestinal (GI) tracts. Virus was not detected in blood, bone marrow, or breast and thigh meat, and feeding breast and thigh meat from virus-infected birds did not transmit the virus. In contrast to the two LPAI viruses, A/chicken/Pennsylvania/1370/1983 (H5N2) HPAI virus caused respiratory and GI tract infections with systemic spread, and virus was detected in blood, bone marrow, and breast and thigh meat. Feeding breast or thigh meat from HPAI (H5N2) virus-infected chickens to other chickens did not transmit the infection. However, A/lchicken/Korea/ES/2003 (H5N1) HPAI virus produced high titers of virus in the breast meat, and feeding breast meat from these infected chickens to other chickens resulted in Al virus infection and death. Usage of either recombinant fowlpox vaccine with H5 AI gene insert or inactivated Al whole-virus vaccines prevented HPAI virus in breast meat. These data indicate that the potential for LPAI virus appearing in meat of infected chickens is negligible, while the potential for having HPAI virus in meat from infected chickens is high, but proper usage of vaccines can prevent HPAI virus from being present in meat.     

重组禽流感灭活苗和禽流感灭活苗对鸡免疫效果的观察

用重组禽流感灭活苗接种10日龄、14日龄和21日龄的SPF鸡,接种后HI抗体效价无显著差异。将H5N1和H5N2疫苗分别接种21日龄SPF鸡,结果表明,H5N1和H5N2均能刺激SPF鸡产生较高的HI抗体;分别接种三黄鸡,接种后21 d,H5N1能刺激三黄鸡产生较高的HI抗体;而H5N2不能刺激三黄鸡产生合格的HI抗体,与SPF鸡免疫组相比差异显著。经过二次接种,HI抗体平均为8.9 log2,与SPF鸡组接种后42 d的各组相比差异不显著,而与一免后21 d的各组HI抗体效价相比差异显著。表明应用禽流感灭活苗对三黄鸡免疫接种,必须进行二免方可达到理想免疫效果,而应用重组禽流感灭活苗对三黄鸡进行免疫接种,一次免疫即可获得较高的HI抗体效价。     

免疫剂量和母源抗体对禽流感重组鸡痘病毒活载体疫苗免疫效力的影响

利用表达 H 5亚型禽流感病毒 (AIV)血凝素基因的重组鸡痘病毒 (r FPV- HA)以不同剂量免疫 1日龄 SPF鸡、有或无母源抗体 (FPV、AIV H5)的商品鸡 ,并于免疫后 2 1d利用同亚型 AIV通过肌肉注射进行致死性攻击 ,通过检测免疫后 HI抗体应答、比较攻毒后发病率和死亡率评价免疫剂量和母源抗体对 r FPV- HA免疫效力的影响。结果发现 ,免疫后 2 1d,15 %～ 2 0 %的 SPF鸡和无母源抗体商品鸡可检出 HI抗体 ,而含母源抗体商品鸡检测不到 HI抗体。利用H5亚型 AIV致死性攻击后 ,10 3～ 10 6 PFU的 r FPV- HA可保护 95 %～ 10 0 %的 SPF鸡和无母源抗体商品鸡抵御强毒攻击 ,使之免于发病和死亡 ;而不同剂量 r FPV- HA接种的含母源抗体商品鸡有 80 %～ 90 %发病和死亡。结果表明 ,在较宽的免疫剂量范围内 ,r FPV- HA对 SPF鸡和无母源抗体商品鸡可提供良好的保护 ,显示出一定的应用前景 ;母源抗体影响 r FPV- HA诱导的免疫应答 ,且提高免疫剂量亦不能克服其干扰作用 ,这提示在实际应用中需优化免疫程序 ,避免母源抗体干扰。     

Effects of DNA dose,route of vaccination,and coadministration of porcine interleukin-6 DNA on results of DNA vaccination against influenza virus infection in pigs

OBJECTIVE: To examine the effects of DNA dose, site of vaccination, and coadministration of a cytokine DNA adjuvant on efficacy of H1-subtype swine influenza virus hemagglutinin (HA) DNA vaccination of pigs. ANIMALS: 24 eight-week-old mixed-breed pigs. PROCEDURE: 2 doses of DNA were administered 27 days apart by use of a particle-mediated delivery system (gene gun). Different doses of HA DNA and different sites of DNA administration (skin, tongue) were studied, as was coadministration of porcine interleukin-6 (pIL-6) DNA as an adjuvant. Concentrations of virus-specific serum and nasal mucosal antibodies were measured throughout the experiment, and protective immunity was assessed after intranasal challenge with homologous H1N1 swine influenza virus. RESULTS: Increasing the dose of HA DNA, but not coadministration of pIL6 DNA, significantly enhanced virus-specific serum antibody responses. Pigs that received DNA on the ventral surface of the tongue stopped shedding virus 1 day sooner than pigs vaccinated in the skin of the ventral portion of the abdomen, but none of the vaccinated pigs developed detectable virus-specific antibodies in nasal secretions prior to challenge, nor were they protected from challenge exposure. Vaccinated pigs developed high virus-specific antibody concentrations after exposure to the challenge virus. CONCLUSIONS AND CLINICAL RELEVANCE: Co-administration of pIL-6 DNA did not significantly enhance immune responses to HA DNA vaccination or protection from challenge exposure. However, HA DNA vaccination of pigs, with or without coadministration of pIL-6 DNA, induced strong priming of the humoral immune system.     

Failure of a recombinant fowl poxvirus vaccine containing an avian influenza hemagglutinin gene to provide consistent protection against influenza in chickens preimmunized with a fowl pox vaccine

Vaccines against mildly pathogenic avian influenza (AI) have been used in turkeys within the United States as part of a comprehensive control strategy. Recently, AI vaccines have been used in control programs against highly pathogenic (HP) AI of chickens in Pakistan and Mexico. A recombinant fowl pox-AI hemagglutinin subtype (H) 5 gene insert vaccine has been shown to protect specific-pathogen-free chickens from HP H5 AI virus (AIV) challenge and has been licensed by the USDA for emergency use. The ability of the recombinant fowl pox vaccine to protect chickens preimmunized against fowl pox is unknown. In the current study, broiler breeders (BB) and white leghorn (WL) pullets vaccinated with a control fowl poxvirus vaccine (FP-C) and/or a recombinant fowl poxvirus vaccine containing an H5 hemagglutinin gene insert (FP-HA) were challenged with a HP H5N2 AIV isolated from chickens in Mexico. When used alone, the FP-HA vaccine protected BB and WL chickens from lethal challenge, but when given as a secondary vaccine after a primary FP-C immunization, protection against a HP AIV challenge was inconsistent. Both vaccines protected against virulent fowl pox challenge. This lack of consistent protection against HPAI may limit use to chickens without previous fowl pox vaccinations. In addition, prior exposure to field fowl poxvirus could be expected to limit protection induced by this vaccine.     

Efficacy of swine influenza A virus vaccines against an H3N2 virus variant

We compared the efficacy of 3 commercial vaccines against swine influenza A virus (SIV) and an experimental homologous vaccine in young pigs that were subsequently challenged with a variant H3N2 SIV, A/Swine/Colorado/00294/2004, selected from a repository of serologically and genetically characterized H3N2 SIV isolates obtained from recent cases of swine respiratory disease. The experimental vaccine was prepared from the challenge virus. Four groups of 8 pigs each were vaccinated intramuscularly at both 4 and 6 wk of age with commercial or homologous vaccine. Two weeks after the 2nd vaccination, those 32 pigs and 8 nonvaccinated pigs were inoculated with the challenge virus by the deep intranasal route. Another 4 pigs served as nonvaccinated, nonchallenged controls. The serum antibody responses differed markedly between groups. After the 1st vaccination, the recipients of the homologous vaccine had hemagglutination inhibition (HI) titers of 1:640 to 1:2560 against the challenge (homologous) virus. In contrast, even after 2nd vaccination, the commercial-vaccine recipients had low titers or no detectable antibody against the challenge (heterologous) virus. After the 2nd vaccination, all the groups had high titers of antibody to the reference H3N2 virus A/Swine/Texas/4199-2/98. Vaccination reduced clinical signs and lung lesion scores; however, virus was isolated 1 to 5 d after challenge from the nasal swabs of most of the pigs vaccinated with a commercial product but from none of the pigs vaccinated with the experimental product. The efficacy of the commercial vaccines may need to be improved to provide sufficient protection against emerging H3N2 variants.     

Influence of maternal immunity on vaccine efficacy and susceptibility of one day old chicks against Egyptian highly pathogenic avian influenza H5N1

In Egypt, continuous circulation of highly pathogenic avian influenza (HPAI) H5N1 viruses of clade 2.2.1 in vaccinated commercial poultry challenges strenuous control efforts. Here, vaccine-derived maternal AIV H5 specific immunity in one-day old chicks was investigated as a factor of vaccine failure in long-term blanket vaccination campaigns in broiler chickens. H5 seropositive one-day old chicks were derived from breeders repeatedly immunized with a commercial inactivated vaccine based on the Potsdam/H5N2 strain. When challenged using the antigenically related HPAIV strain Italy/98 (H5N2) clinical protection was achieved until at least 10 days post-hatch although virus replication was not fully suppressed. No protection at all was observed against the Egyptian HPAIV strain EGYvar/H5N1 representing a vaccine escape lineage. Other groups of chicks with maternal immunity were vaccinated once at 3 or 14 days of age using either the Potsdam/H5N2 vaccine or a vaccine based on EGYvar/H5N1. At day 35 of age these chicks were challenged with the Egyptian HPAIV strain EGYcls/H5N1 which co-circulates with EGYvar/H5N1 but does not represent an antigenic drift variant. The Potsdam/H5N2 vaccinated groups were not protected against EGYcls/H5N1 infection while, in contrast, the EGYvar/H5N1 vaccinated chicks withstand challenge with EGYvar/H5N1 infection. In addition, the results showed that maternal antibodies could interfere with the immune response when a homologous vaccine strain was used.     

重组禽流感病毒灭活疫苗(H5N1亚型,Re-1株)免疫鸡抗体消长规律及免疫程序的初步研究

研究新型重组H5N1亚型禽流感灭活疫苗对种鸡和肉鸡的免疫原性,并对雏鸡母源抗体和免疫后的抗体进行动态观察,根据试验结果推荐该疫苗对鸡的免疫程序。用HI方法检测种鸡、肉鸡的母源抗体和免疫抗体,根据母源抗体的衰减和免疫抗体的消长规律确定首免和再免日龄。结果表明种鸡的母源抗体约能维持10 d多;0.3 mL/羽首免后10 d HI抗体就可达到6.40 log2,3-5周达到高峰期,至免疫17周后(19周龄)HI抗体水平仍然维持在4.88 log2;19周龄时0.5 mL/羽进行二免,有效抗体能维持约20周;280日龄0.5 mL/羽三免后抗体水平均一,下降缓慢,至种鸡淘汰时(三免后29周)抗体水平仍能维持在5.32 log2。肉鸡母源抗体约能维持7d,10日龄时0.3 mL/羽免疫,有效抗体能维持到上市。新型重组H5N1亚型禽流感灭活疫苗对鸡的免疫原性确实。     

Mucosal vaccination with formalin-inactivated avian metapneumovirus subtype C does not protect turkeys following intranasal challenge

Studies were performed to determine if mucosal vaccination with inactivated avian metapneumovirus (aMPV) subtype C protected turkey poults from clinical disease and virus replication following mucosal challenge. Decreases in clinical disease were not observed in vaccinated groups, and the vaccine failed to inhibit virus replication in the tracheas of 96% of vaccinated birds. Histopathologically, enhancement of pulmonary lesions following virus challenge was associated with birds receiving the inactivated aMPV vaccine compared to unvaccinated birds. As determined by an enzyme-linked immunosorbent assay (ELISA), all virus-challenged groups increased serum immunoglobulin (Ig) G and IgA antibody production against the virus following challenge; however, the unvaccinated aMPV-challenged group displayed the highest increases in virus-neutralizing antibody. On the basis of these results it is concluded that intranasal vaccination with inactivated aMPV does not induce protective immunity, reduce virus shedding, or result in decreased histopathologic lesions.     

Protective efficacy of stockpiled vaccine against H5N8 highly pathogenic avian influenza virus isolated from a chicken in Kumamoto prefecture,Japan, in 2014

H5 highly pathogenic avian influenza (HPAI) viruses have spread worldwide, and antigenic variants of different clades have been selected. In this study, the national stockpiled vaccine prepared from A/duck/Hokkaido/Vac-1/2004 (H5N1) strain was evaluated for the protective efficacy against H5N8 HPAI virus isolated in Kumamoto prefecture, Japan, in April 2014. In the challenge test, all of the vaccinated chickens survived without showing any clinical signs and reduced virus shedding. It was concluded that the present stockpiled vaccine was effective against the H5N8 HPAI virus.     

Overcoming maternal antibody interference by vaccination with human adenovirus 5 recombinant viruses expressing the hemagglutinin and the nucleoprotein of swine influenza virus

Sows and gilts lack immunity to human adenovirus 5 (Ad-5) vectored vaccines so immunogens of swine pathogens can be expressed with these vaccines in order to immunize suckling piglets that have interfering, maternally derived antibodies. In this study 7-day-old piglets, that had suckled H3N2 infected gilts, were sham-inoculated with a non-expressing Ad-5 vector or given a primary vaccination with replication-defective Ad-5 viruses expressed the H3 hemagglutinin and the nucleoprotein of swine influenza virus (SIV) subtype H3N2. The hemagglutination inhibition (HI) titer of the sham-inoculated group (n = 12) showed continued antibody decay whereas piglets vaccinated with Ad-5 SIV (n = 23) developed an active immune response by the second week post-vaccination. At 4 weeks-of-age when the HI titer of the sham-inoculated group had decayed to 45, the sham-inoculated group and half of the Ad-5 SIV vaccinated pigs were boosted with a commercial inactivated SIV vaccine. The boosted pigs that had been primed in the presence of maternal interfering antibodies had a strong anamnestic response while sham-inoculated pigs did not respond to the commercial vaccine. Two weeks after the booster vaccination the pigs were challenged with a non-homologous H3N2 virulent SIV. The efficacy of the vaccination protocol was demonstrated by abrogation of clinical signs, by clearance of challenge virus from pulmonary lavage fluids, by markedly reduced virus shedding in nasal secretions, and by the absence of moderate or severe SIV-induced lung lesions. These recombinant Ad-5 SIV vaccines are useful for priming the immune system to override the effects of maternally derived antibodies which interfere with conventional SIV vaccines.     

Avian infectious bronchitis: cross-protection studies using different Australian subtypes

The cross-immunity of vaccinated chickens after challenge with some Australian infectious bronchitis viruses was assessed by humoral antibody responses and by ciliary activity in tracheal rings of vaccinated chickens following challenge. Four viruses were used for vaccination: Vac 3, Vac 4, both current infectious bronchitis vaccine viruses, and Q1/76 and N2/62. IBV N1/62 (synonym T0 and infectious bronchitis virus N9/74 (synonym Appin) were used to challenge the vaccinated chickens. Results showed a lack of correlation between humoral antibody levels and protection. Cross-immunity was found after vaccination with each subtype, but was lower for Vac 3 and Vac 4 than for Q1/76 and N2/62.     

Safety, efficacy, and immunogenicity of a modified-live equine influenza virus vaccine in ponies after induction of exercise-induced immunosuppression

OBJECTIVE: To determine safety, efficacy, and immunogenicity of an intranasal cold-adapted modified-live equine influenza virus vaccine administered to ponies following induction of exercise-induced immunosuppression. DESIGN: Prospective study. ANIMALS: Fifteen 9- to 15-month old ponies that had not had influenza. PROCEDURE: Five ponies were vaccinated after 5 days of strenuous exercise on a high-speed treadmill, 5 were vaccinated without undergoing exercise, and 5 were not vaccinated or exercised and served as controls. Three months later, all ponies were challenged by nebulization of homologous equine influenza virus. Clinical and hematologic responses and viral shedding were monitored, and serum and nasal secretions were collected for determination of influenza-virus-specific antibody isotype responses. RESULTS: Exercise caused immunosuppression, as indicated by depression of lymphocyte proliferation in response to pokeweed mitogen. Vaccination did not result in adverse clinical effects, and none of the vaccinated ponies developed clinical signs of infection following challenge exposure. In contrast, challenge exposure caused marked clinical signs of respiratory tract disease in 4 control ponies. Vaccinated and control ponies shed virus after challenge exposure. Antibody responses to vaccination were restricted to serum IgGa and IgGb responses in both vaccination groups. After challenge exposure, ponies in all groups generated serum IgGa and IgGb and nasal IgA responses. Patterns of serum hemagglutination inhibition titers were similar to patterns of IgGa and IgGb responses. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that administration of this MLV vaccine to ponies with exercise-induced immunosuppression was safe and that administration of a single dose to ponies provided clinical protection 3 months later.