Modified-live Vaccine Research Articles

Differentiation of field isolates and vaccine strains of infectious laryngotracheitis virus by DNA sequencing

Avian infectious laryngotracheitis (ILT) is a severe clinical respiratory disease of chickens and causes the clinical symptoms of difficulty in breathing and bloody coughing and as if involves laying hens affect the egg production. Two different regions of the infected cell protein 4 (ICP4) gene of infectious laryngotrucheitis virus (ILTV) were amplified and sequenced for characterization of field isolates and tissue culture-origin (TCO) and chicken embryo-origin (CEO) vaccine strains. Phylogenetic analysis of the two regions showed no differences in nucleotide and amino acid sequences between Iranian field isolates with high morbidity and nearly 30% mortality and CEO attenuated vaccines. These findings suggest that modified-Live (ML) ILT vaccine viruses may increase in virulence after bird-to-bird passages. Key words: Avian infectious laryngotracheitis, infected cell protein 4, phylogenetic analysis.

Evaluation of a commercially available modified-live Streptococcus equi subsp equi vaccine in ponies

To evaluate a commercially available modified-live Streptococcus equi subsp equi vaccine for safety and persistence in vaccinated ponies and to detect recombination or reversion events in the vaccine strain. 5 ponies that were 1.5 to 8 years old (group 1) and 4 ponies that were 6 months old (group 2). Ponies were vaccinated, with a subsequent booster vaccination 2 to 3 weeks later, and monitored for 50 days. At booster vaccination, an equal amount of a tetracycline-resistant wild-type strain of S equiwas administered. Recovery of all strains was performed by use of bacteriologic culture and PCR assays. Ponies in group 1 had background antibody titers against S equi antigen before vaccination despite the lack of known exposure to S equi. Ponies in group 2 were immunologically naïve. Increases in anti-S equi antibody titers were detected in both groups. Ponies in group 1 did not have clinical signs of disease caused by S equi. In group 2, all ponies developed abscesses in retropharyngeal lymph nodes; 1 pony developed severe clinical disease and was euthanized. The vaccine strain was recovered from ponies in group 2 for up to 24 days after vaccination. Although the vaccine was successful in inducing IgG antibodies against S equi in all ponies, findings suggested that the vaccine may have caused substantial morbidity and some deaths in the young ponies. In young ponies, the vaccine strain persisted in tissues for weeks; however, no evidence of recombination was detected.

Epidemiologic and Phylogenetic Characteristics of Porcine Reproductive and Respiratory Syndrome Viruses in Conventional Swine Farms of Jeju Island as a Candidate Region for PRRSV Eradication

Jeju island is the biggest island in Korea. The imports of pigs or their relatives from mainland Korea to this island has been banned since 1998. With this unique geographical and epidemiological context, epidemiology of porcine reproductive and respiratory syndrome virus (PRRSV) was investigated on the island. While all investigated farms showed 100% of seropositive rate for PRRSV, pigs on 37.2% (16/43) of the farms had viremia with type II PRRSV. The seropositive and viremia-positive rates for PRRSV in 30- to 60-day-old pigs were significantly higher in the western area ('swine farm complex' area) than the eastern area ('Scattered swine farm' area) of Jeju island. When 21 ORF5 sequences obtained from viremic sera were phylogenetically analysed, lineage 5 and Kor (newly termed in this study) of type II PRRSV were only found in Jeju island without changes from a previous report (2002-2003). Because other lineages of type II PRRSV (lineage 1 and 3) and type I PRRSV have recently emerged in mainland Korea, the banning of pigs' movement might be effective to protect the island from the introduction of these new PRRSV genotypes. Under this epidemiological condition (no introduction of new strains except for the modified-live vaccine (MLV) strain), the positive selection sites were analysed based on ORF5 of the virus. The amino acid 58 of GP5 (located on the hypervariable region) was predicted as a strong positive selection site. Although 51.2% (22/43) of the investigated farms had applied MLV, field strains of type II PRRSV were still circulating with strong positive selection. However, the restricted population of type II PRRSV (lineage 5 and Kor) without introduction of type I PRRSV or the other lineages of type II PRRSV indicate that the island has an effective quarantine system, which would allow PRRSV eradication.

Fetal protection against bovine viral diarrhoea type 1 virus infection after one administration of a live-attenuated vaccine

A modified-live vaccine has been shown previously to prevent fetal infection with bovine viral diarrhoea virus (BVDV)-2 and, to some extent BVDV-1, when used in association with an inactivated vaccine in a two-step vaccination protocol. In this challenge study, the modified-live vaccine used alone was able to protect 13 heifers between 49 and 96 days of gestation at challenge from leucopenia and virus replication and, for a 4-month period, to prevent fetal infection. The efficacy of the BVDV-1f 22146/Han81 challenge was demonstrated by virus isolation from the fetuses of all nine non-vaccinated, control heifers. However, the small number of heifers tested meant that the vaccination failure rate could be as high as 10% in the field.

Immunologic responses of beef calves to concurrent application of modified-live viral vaccine (intranasal and systemic administration) and systemically administered Mannheimia haemolytica bacterin-leukotoxoid.

A study was conducted to assess the immunological response to a Mannheimia haemolytica bacterin-leukotoxoid, given separately or concurrently with a multivalent intranasally administered modified-live viral vaccine to range beef calves. Initially 202 spring-born calves were screened for infectious bovine rhinotracheitis (IBR), bovine respiratory syncytial virus (BRSV), and M. haemolytica leukotoxin antibody titers on day-30. A total of 154 calves with day 0 geometric mean IBR titers of <1:6 were accepted into the study. Fifty-one calves were assigned to treatment group T1 (M. haemolytica bacterin-leukotoxoid only; One Shot®, Pfizer Animal Health, New York, NY) and 51 calves were assigned to group T2 (intranasal modified-live virus (MLV) bovine herpesvirus-1 (BHV-1) and parainfluenza-3 (PI3) vaccine; TSV-2®, Pfizer Animal Health) and M. haemolytica bacterin-leukotoxoid (One Shot®). Fifty-two calves were assigned to group T3 intranasal MLV BHV-1, PI3, and BRSV vaccine (INFORCETM 3, Pfizer Animal Health) and M. haemolytica bacterin-leukotoxoid (One Shot®). On day 0, all study calves were administered their assigned vaccine. On day 91, all calves in the study were administered a pentavalent MLV vaccine containing BHV-1, BVD types 1 and 2, BRSV, and PI3 antigens (Bovi-Shield GOLD® 5, Pfizer Animal Health) and M. haemolytica bacterin-leukotoxoid (One Shot®) at separate injection sites. On days 0, 14, 28, 91, and 112, blood samples were collected, serum separated, and held frozen until completion of the study, at which time samples were evaluated for IBR and BRSV serum neutralization antibody titers and M. haemolytica leukotoxin antibody concentrations. Results demonstrated concurrent administration of the intranasal vaccines and the M. haemolytica bacterin-leukotoxoid did not affect the bacterin-leukotoxoid serological response. Calves vaccinated with intranasal BRSV vaccine had a significant (P less than 0.05) increase in BRSV antibody response when revaccinated systemically with injectable 5-way MLV vaccine 90 days later. Vaccination with M. haemolytica bacterin-leukotoxoid at approximately eight weeks of age resulted in a statistically significant (P less than 0.05) anamnestic response following revaccination 90 days later.

Effect of trivalent modified-live virus respiratory vaccine on performance, health, and carcass traits of lightweight feeder steers

A total of 3,615 lightweight feeder steers were used to compare the effects of trivalent (infectious bovine rhinotracheitis virus and bovine viral diarrhea virus types 1 and 2) modified-live virus (MLV) vaccine products on performance, health, and carcass traits of cattle in a commercial feedlot setting. The three trivalent MLV vaccination products compared were Express? 3 (Boeh-ringer Ingelheim Vetmedica, Inc., St. Joseph MO), Bovi-Shield GOLD? IBR-BVD (Pfizer Animal Health, New York, NY), and Vista? 3 SQ (Intervet/Schering-Plough Animal Health, Summit, NJ). No differences (P?0.30) in feed conversion, final weight, or gain performance were detected among vaccination treatments. The percentage of BRD morbidity was similar (P=0.15) among treatments, averaging 12.3% overall. Furthermore, no vaccine treatment differences (P?0.36) were observed for relapse percentage, mortality or railer incidence, regardless of cause. All cattle used in the study were tested for persistent infection (PI) with BVDV, and the prevalence of cattle testing positive for PI-BVDV was similar (P=0.56) among the vaccine treatments and averaged 0.27% overall. Cattle which tested positive for PI-BVDV were not removed from the study pens, and after data were pooled, health and performance did not differ for pens with or without a PI-BVDV pen mate. When utilizing lightweight feeder steers with relatively low BRD-associated morbidity and mortality, there was no difference in performance, health, and carcass trait observations among the three trivalent MLV vaccine products evaluated.

Protection from persistent infection with a bovine viral diarrhea virus (BVDV) type 1b strain by a modified-live vaccine containing BVDV types 1a and 2, infectious bovine rhinotracheitis virus, parainfluenza 3 virus and bovine respiratory syncytial virus

Recent studies showed that BVDV-1b subgenotype is dominant in North and South American field BVDV isolates. However, nearly all commercially available BVDV-1 vaccines contain BVDV-1a strains. In order to study the efficacy of BVDV-1a vaccine against BVDV-1b infection, this study was designed to evaluate a modified-live vaccine (MLV) containing BVDV-1a and BVDV-2 strains for its efficacy in prevention of persistent infection of fetuses against BVDV-1b strain, when the heifers were vaccinated prior to breeding. Heifers were vaccinated subcutaneously with a single dose of the MLV and bred four weeks after vaccination. The pregnant heifers were challenged with a non-cytopathic BVDV-1b strain at approximately 80 days of gestation. Vaccinated heifers were protected from clinical disease and viremia caused by the BVDV-1b virus. At approximately 155 days of gestation, the fetuses were harvested and tissue samples of thymus, lungs, spleen, kidney and intestines were collected for virus isolation. BVDV was isolated from 100% of the fetuses in the non-vaccinated control group, and from only one fetus (4.3%) from the vaccinated group. Results demonstrated that the MLV containing BVDV-1a and BVDV-2 strains provided 96% protection from fetal persistent infection caused by the BVDV-1b strain.

Infecção experimental de bezerros com recombinantes do herpesvírus bovino tipo 5 defectivos na glicoproteína E (gE), timidina quinase (TK) e ambos, gE/TK

Este artigo descreve uma investigação da virulência/atenuação de recombinantes do herpesvírus bovino tipo 5 (BoHV-5) com deleções nos genes da glicoproteína E (BoHV-5gEΔ), timidina quinase (BoHV-5TKΔ), e ambos gE e TK (BoHV-5gEΔTKΔ). Bezerros soronegativos (80-90 dias de idade) inoculados com o vírus parental SV-507/99 (n=5) excretaram o vírus em secreções nasais por até 15 dias (média de 10,8 dias). Nos animais inoculados com os recombinantes, a duração da excreção viral foi de 11 dias (BoHV-5gEΔ), 9,6 dias (BoHV-5TKΔ) e 6,2 dias (BoHV-5gEΔTKΔ). Os maiores títulos foram observados entre os dias 1 e 6 pós-inoculação (pi), sendo de 10(6,8)TCID50/mL para o SV-507/99, 10(5,1)TCID50/mL (BoHV-5gEΔ), 10(5,9)TCID50/mL (BoHV-5TKΔ) e 10(4,7)TCIΔ50/mL (BoHV-5gEΔTKΔ). Os bezerros inoculados com o vírus parental apresentaram anorexia e apatia; três deles mostraram apatia profunda e perda da condição corporal. Dois bezerros foram eutanasiados in extremis nos dias 10 e 11 pi, respectivamente e o vírus foi isolado de várias regiões do encéfalo. Já os bezerros inoculados com os recombinantes permaneceram saudáveis; alguns apresentaram uma secreção nasal serosa transitória. Administração de dexametasona (Dx) no dia 42 pi resultou em excreção viral por todos os bezerros inoculados com o vírus parental (duração média de 3,7 dias), por 2 de 5 bezerros dos grupos BoHV-5TKΔ (dois dias) e BoHV-5gEΔ (um dia). Os bezerros inoculados com o duplo mutante BoHV-5gEΔTKΔ não excretaram o vírus após o tratamento com Dx. Pesquisa de DNA viral por PCR no dia 30 pós-Dx revelou uma ampla distribuição do DNA do vírus parental no encéfalo; poucas seções (3/30) foram positivas no encéfalo dos animais do grupo BoHV-5gEΔ, e não detectou-se DNA latente no encéfalo dos animais dos grupos BoHV-5TKΔ e BoHV-5gEΔTKΔ. Esses resultados demonstram que os mutantes simples (gE and tk-deletados) são atenuados para bezerros e estabelecem e/ou reativam infecção latente ineficientemente. Já o duplo mutante BoHV-5gEΔTKΔ é atenuado e parece não estabelecer e/ou não reativar eficientemente a infecção latente. Portanto, os vírus recombinantes, e em especial o duplo mutante BoHV-5gEΔTKΔ apresentam um fenótipo compatível com a sua inclusão em vacinas vivas modificadas.

Efficacy of a non-adjuvanted, modified-live virus vaccine in calves with maternal antibodies against a virulent bovine viral diarrhea virus type 2a challenge seven months following vaccination

In the presence of maternal antibodies, 26 calves three days of age were either vaccinated (n=15) with a single dose of a non-adjuvanted, pentavalent, modified-live vaccine containing bovine herpes virus-1, bovine respiratory syncytial virus, bovine viral diarrhea virus 1a (BVDV1a), bovine viral diarrhea virus 2a (BVDV2a), and bovine parainfluenza-3, or sham vaccinated with sterile saline (n=11). At approximately seven months post-vaccination, when vaccinates and non-vaccinates were seronegative to BVDV1a and BVDV2a antibodies, all calves were intranasally challenged with a virulent BVDV2a (strain 1373). Clinical signs of BVDV infection were monitored beginning three days prior to challenge and concluded on day 21 after challenge. Calves vaccinated in the face of maternal antibodies (IFOMA) were less impacted by the challenge. Based on clinical parameters, vaccinates had reduced clinical scores, rectal temperature, weight loss, and mortality compared to sham-vaccinated animals. Vaccinated animals had higher levels of circulating white blood cells and fewer animals were viremic than sham-vaccinated animals. This study demonstrated that a calf as young as three days of age when vaccinated IFOMA can be protected against a virulent BVDV2a challenge with a non-adjuvanted, pentavalent vaccine.

A Multiphasic Typing Approach to Subtype Streptococcus Equi Subspecies Equi

The objective of the present investigation was to differentiate between strains of Streptococcus equi subspecies equi implicated in abscess formation in vaccinated horses. Streptococcus equi isolates recovered from clinical specimens associated with equine strangles cases submitted to the University of Illinois Veterinary Diagnostic Laboratory were compared with S. equi isolates representing at least 12 lots of a commercial modified live vaccine (MLV) to determine whether the isolates obtained from the abscesses were vaccine or wild type. Genotyping techniques evaluated included enterobacterial repetitive intergenic consensus polymerase chain reaction (PCR), repetitive extragenic palindrome PCR, BOX element PCR, ribotyping, and pulsed-field gel electrophoresis (PFGE). Phenotypic evaluations were performed using the Biolog GP2 Microplate (hereafter, Biolog). In cases where Biolog and PFGE results did not coincide, a single nucleotide polymorphism located in the upstream regulatory region of szp gene was used to identify the S. equi strains. PFGE and Biolog successfully differentiated wild-type S. equi strains isolated from clinical submissions from isolates of the MLV. PFGE genotyping enabled further subtyping of the wild-type strains, whereas Biolog combined with szp sequencing was useful in differentiating the MLV strain from its wild-type progenitor. Deletion of a single guanine residue located in the upstream regulatory region of the szp gene appears to be conserved among vaccine isolates, and shows a 98.5% correlation to Biolog identification. This multiphasic approach can be used to answer specific diagnostic questions pertaining to the source of infection and/or outbreak, or to address quarantine concerns.

Vaccination with a modified-live bovine viral diarrhea virus (BVDV) type 1a vaccine completely protected calves against challenge with BVDV type 1b strains

Vaccination plays a significant role in the control of bovine viral diarrhea virus (BVDV) infection and spread. Recent studies revealed that type 1b is the predominant BVDV type 1 subgenotype, representing more than 75% of field isolates of BVDV-1. However, nearly all current, commercially available BVDV type 1 vaccines contain BVDV-1a strains. Previous studies have indicated that anti-BVDV sera, induced by BVDV-1a viruses, show less neutralization activity to BVDV-1b isolates than type 1a. Therefore, it is critically important to evaluate BVDV-1a vaccines in their ability to prevent BVDV-1b infection in calves. In current studies, calves were vaccinated subcutaneously, intradermally or intranasally with a single dose of a multivalent, modified-live viral vaccine containing a BVDV-1a strain, and were challenged with differing BVDV-1b strains to determine the efficacy and duration of immunity of the vaccine against these heterologous virus strains. Vaccinated calves, in all administration routes, were protected from respiratory disease caused by the BVDV-1b viruses, as indicated by significantly fewer clinical signs, lower rectal temperatures, reduced viral shedding and greater white blood cell counts than non-vaccinated control animals. The BVDV-1a vaccine elicited efficacious protection in calves against each BVDV-1b challenge strain, with a duration of immunity of at least 6 months.

Genetic modification of Bluetongue virus by uptake of "synthetic" genome segments

Since 1998, several serotypes of Bluetongue virus (BTV) have invaded several southern European countries. In 2006, the unknown BTV serotype 8 (BTV8/net06) unexpectedly invaded North-West Europe and has resulted in the largest BT-outbreak ever recorded. More recently, in 2008 BTV serotype 6 was reported in the Netherlands and Germany. This virus, BTV6/net08, is closely related to modified-live vaccine virus serotype 6, except for genome segment S10. This genome segment is closer related to that of vaccine virus serotype 2, and therefore BTV6/net08 is considered as a result of reassortment. Research on orbiviruses has been hampered by the lack of a genetic modification method. Recently, reverse genetics has been developed for BTV based on ten in vitro synthesized genomic RNAs. Here, we describe a targeted single-gene modification system for BTV based on the uptake of a single in vitro synthesized viral positive-stranded RNA. cDNAs corresponding to BTV8/net06 genome segments S7 and S10 were obtained by gene synthesis and cloned downstream of the T7 RNA-polymerase promoter and upstream of a unique site for a restriction enzyme at the 3'-terminus for run-off transcription. Monolayers of BSR cells were infected by BTV6/net08, and subsequently transfected with purified in vitro synthesized, capped positive-stranded S7 or S10 RNA from BTV8/net06 origin. "Synthetic" reassortants were rescued by endpoint dilutions, and identified by serotype-specific PCR-assays for segment 2, and serogroup-specific PCRs followed by restriction enzyme analysis or sequencing for S7 and S10 segments. The targeted single-gene modification system can also be used to study functions of viral proteins by uptake of mutated genome segments. This method is also useful to generate mutant orbiviruses for other serogroups of the genus Orbivirus for which reverse genetics has not been developed yet.

Evaluation of a Commercial Vaccine to Protect Developing Fetuses from Natural Challenges with Bovine Viral Diarrhea Virus and Bovine Herpesvirus 1

Fetal protection in heifers vaccinated with a modified-live vaccine (Express® FPS, Boehringer Ingelheim Vetmedica) was evaluated following sequential, prolonged field exposures to animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) and animals acutely infected with bovine herpesvirus 1 (BoHV-1).

Risk factors associated with the occurrence of undesired effects in sheep and goats after field vaccination with modified-live vaccine against bluetongue virus serotypes 2, 4 and 16

In the 2004, the Sardinian bluetongue (BT) vaccination campaign used the combination of monovalent BTV-2, BTV-4 and BTV-16 modified-live vaccines manufactured by the Onderstepoort Biological Products in South Africa. Following vaccination, some herds showed temperature, oedema, lameness, hyperaemia and decrease in milk production, and some others remained perfectly healthy. This study aimed to evaluate whether important factors present in the herd at the time of vaccination could be associated to the occurrence of undesired effects observed after immunisation with BTV modified-live vaccines. A sample of 17 sheep and 4 goat flocks, for a total of 670 animals, were included in the study and risk factors such as presence of most important parasitic, bacterial and viral diseases as well as anomalies of biochemical and haematological parameters were associated to the presence or absence of side effects. For each factor the relative risk and 95% confidence interval were calculated. Following vaccination, bluetongue-like symptoms were observed in 13 flocks. In these flocks, a higher (P<0.05) proportion of animals had viraemia and showed higher titers to BTV-16 after immunisation. Positive association (RR=2.50, 1.17–5.04) was also found between flocks in which undesired effect were observed and positive serology against Maedi–Visna virus. On the contrary, presence of BTV genome fractions in the blood of animals at the time of vaccination was found to be protective (RR=0.7, 0.58–0.84) to the occurrence of undesired effect subsequent to BTV vaccination.

Comparison of three commercial vaccines for preventing persistent infection with bovine viral diarrhea virus

Eighty crossbred beef heifers were randomly allocated to four groups to evaluate the efficacy of vaccination in preventing development of calves persistently infected with bovine viral diarrhea virus (BVDV). Group 1 ( n = 11) was non-vaccinated controls, whereas three groups were vaccinated with commercially available multivalent BVDV vaccines at weaning (∼7 mo of age), 28 d post-weaning, ∼1 y of age, and 28 d later. Groups 2 ( n = 23) and 3 ( n = 23) were given a modified-live BVDV vaccine, whereas Group 4 was given an inactivated BVDV vaccine. Heifers were bred by AI and subsequently exposed to two bulls. At 61 d after AI, 70 heifers were pregnant ( n = 10 for Group 1 and n = 20/group for Groups 2, 3, and 4). Three cattle persistently infected with BVDV were commingled with the pregnant heifers (in an isolated pasture) from 68 to 126 d after AI. Thereafter, viremias were detected in pregnant heifers from Groups 1, 3, and 4 (10/10, 1/20, and 10/20, respectively), but not in pregnant heifers from Group 2 (0/20). Resulting calves were assessed for persistent infection using serum PCR, ear notch antigen capture-ELISA, and immunohistochemistry. Persistently infected calves were only produced in Group 1 (10/10) and Group 4 (2/18). In conclusion, commercial vaccines provided effective fetal protection despite prolonged natural exposure to BVDV. Given that viremias were detected in 11 vaccinated heifers after BVDV exposure, and two vaccinated heifers gave birth to persistently infected calves, there is continued need for biosecurity and diagnostic surveillance, in addition to vaccination, to ensure effective BVDV control.

Perspectivas para el control del Virus de la Diarrea Viral Bovina (BVDV)

Summary Bovine Viral Diarrhea Virus (BVDV) is one of the most important infectious agents in cattle population. BVDV is widespread throughout the world and it is endemic disease in most of the cattle population where 40 to 80% are seropositive. It causes economic losses mainly in breeding cattle. BVDV genetic and antigenic diversity is due to the virus high mutation and recombination frequency, which is reflected in many clinical manifestations and the difficult control of the disease. Control and prevention measures implemented by some countries are based on the elimination of the main source of infection: the persistently infected animals (PI animals), as well as the improvement of the immune response through the use of vaccines. Immunization with inactivated and modified-live vaccines has been used for decades without any significant improvement. New experimental strategies are being developed: recombinant vaccines where BVDV specific genes are selected in order to immunize cattle and thus overcome the shortcomings of conventional vaccines.

Comparison of different prime-boost regimes with DNA and recombinant Orf virus based vaccines expressing glycoprotein D of pseudorabies virus in pigs

Both DNA and Orf virus (ORFV; Parapox virus) based vaccines have shown promise as alternatives for conventional vaccines in pigs against pseudorabies virus (PRV) infection causing Aujeszky's disease. In the present study we evaluated the efficacy of different prime-boost regimes in pigs in terms of immunogenicity and protection against challenge infection with PRV. The different prime-boost regimes consisted of the homologous prime-boost regimes (DNA followed by DNA or ORFV followed by ORFV) and the heterologous prime-boost regimes (DNA followed by ORFV and ORFV followed by DNA), all based on glycoprotein D (gD) of PRV. Moreover, we compared the efficacy of the different prime-boost regimes with the efficacy of a conventional modified live vaccine (MLV). The different prime-boost regimes resulted in different levels of immunity and protection against challenge infection. Most effective was the regime of priming with DNA vaccine followed by boosting with the ORFV based vaccine. This regime resulted in strong antibody responses, comparable to the antibody responses obtained after prime-boost vaccination with a conventional MLV vaccine. Also with regard to protection, the prime DNA-boost ORFV regime performed better than the other prime-boost regimes. This study demonstrates the potential of a heterologous prime-boost vaccination strategy against PRV based on a single antigen, and that in the natural host, the pig.

Evaluation of a commercial bovine viral diarrhea virus vaccine in nonpregnant female alpacas ( Vicugna pacos)

Bovine viral diarrhea virus (BVDV) is an emerging pathogen in alpacas and many questions still persist regarding disease mechanisms and control strategies. The purpose of this study was to evaluate a commercial BVDV vaccine for safety and efficacy in alpacas. Five nonpregnant alpacas were vaccinated with a modified-live BVDV vaccine and challenged 25 days post-immunization by nasal and ocular inoculation with a BVDV Type 1b strain isolated from a confirmed BVDV persistently infected alpaca. Two nonpregnant alpacas served as non-vaccinated controls and were similarly challenged. Results indicated that BVDV virus could not be detected from the vaccinated alpacas but was detected in the unvaccinated alpacas. Results suggest that administration of modified-live BVDV vaccine protected the alpacas in this study from experimental challenge and no adverse effects from the vaccine were observed.

Novel BVDV-2 mutants as new candidates for modified-live vaccines

Protection against Bovine viral diarrhea virus (BVDV) type 2 infection of commercially available vaccines is often limited due to marked genetic and antigenic differences between BVDV types 1 (BVDV-1) and 2 (BVDV-2). Therefore, the immunogenicity of selected BVDV-1 and BVDV-2 mutants derived from infectious full-length cDNA clones and their use as modified-live vaccine candidates against challenge infection with a virulent heterologous BVDV-2 field isolate were investigated. Deletion mutants of BVDV-1 and BVDV-2 lacking a part of the Npro gene (BVDV-1ΔNpro/BVDV-2ΔNpro) were used as well as a packaged replicon with a deletion in the structural core protein encoding region (BVDV-2ΔC-pseudovirions). The 25 calves used in this vaccination/challenge trial were allocated in five groups (n=5/group). One group received BVDV-1ΔNpro (1 shot), one group BVDV-2ΔNpro (1 shot), one group received both, BVDV-1ΔNpro and BVDV-2ΔNpro (1 shot), and one group was immunised with the BVDV-2ΔC-pseudovirions (2 shots). The fifth group served as non-vaccinated control group. All groups were challenged intranasally with the BVDV-2 strain HI916 and monitored for signs of clinical disease, virus shedding and viremia. All tested BVDV vaccine candidates markedly reduced the outcome of the heterologous virulent BVDV-2 challenge infection showing graduated protective effects. The BVDV-2ΔNpro mutant was able to induce complete protection and a “sterile immunity” upon challenge. Thus it represents a promising candidate for an efficacious future live vaccine.

Efficacy of a combination viral vaccine for protection of cattle against experimental infection with field isolates of bovine herpesvirus-1

To determine whether a combination viral vaccine containing a modified-live bovine herpesvirus-1 (BHV-1) would protect calves from infection with virulent field strains of BHV-1 for weeks or months after vaccination. Randomized controlled trial, performed in 2 replicates. 63 weaned 4- to 6-month-old crossbred beef calves seronegative for antibody against BHV-1. Calves were randomly allocated to 1 of 2 treatment groups. Control calves (n = 10/replicate) received a combination modified-live mixed viral vaccine without BHV-1, and treatment calves (20 and 23/replicate) received a combination modified-live mixed viral vaccine containing BHV-1. Each group was challenged via aerosol with 1 of 2 field strains of BHV-1, 30 days after vaccination in replicate 1 and 97 days after vaccination in replicate 2. After challenge, calves were commingled in 1 drylot pen. Clinical signs, immune responses, and nasal shedding of virus were monitored for 10 days after challenge, after which the calves were euthanatized and tracheal lesions were assessed. Vaccination stimulated production of BHV-1-specific IgG antibody that cross-neutralized several field and laboratory strains of BHV-1. Challenge with both field strains of BHV-1 resulted in moderate to severe respiratory tract disease in control calves. Treatment calves had significantly fewer signs of clinical disease, shed less BHV-1, had less or no weight loss after challenge, and had fewer tracheal lesions than control calves for at least 97 days after vaccination. Administration of the combination modified-live BHV-1 vaccine yielded significant disease-sparing effects in calves experimentally infected with virulent field strains of BHV-1.