Reversion to Virulence of Chicken-Passaged Infectious Bronchitis Vaccine Virus

Hopkins,; Hw, Yoder

doi:10.2307/1590639

Cited by 33 publications

(25 citation statements)

References 7 publications

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“…Finally, our results corroborate the observations of Hopkins and Yoder [8] showing that infectious bronchitis vaccine virus increases the M. synoviae capacity to induce airsacculitis in chickens.…”

Section: Discussionsupporting

confidence: 91%

Experimental evidence of indirect transmission of Mycoplasma synoviae

et al. 2005

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-The aim of the study was to analyse experimental transmission of Mycoplasma synoviae, an avian pathogen. Three experiments using specific pathogen-free day-old chicks placed in isolators were conducted. In the first experiment, the birds were introduced in an isolator previously contaminated with a M. synoviae broth culture. After 34 days, these birds were eliminated and, for the second trial, the chicks were introduced in the same isolator without disinfecting. In the third assay, the chicks were placed in an isolator containing a mixture of food, feathers and dust collected less than an hour earlier from a M. synoviae infected laying hen flock. In the second and third experiments in order to exacerbate the M. synoviae infection, the birds were inoculated with infectious bronchitis (IB) virus. The presence of M. synoviae in the environment and in tracheal swabs was monitored by culture, a multiplex PCR (mPCR) detecting M. synoviae and Mycoplasma 16S rDNA and a multiplex RT-PCR (mRT-PCR) detecting the M. synoviae mRNA coding for a membrane protein and Mycoplasma 16S rRNA. In in vitro experimental conditions, M. synoviae mRNA and 16S rRNA were detected up to 20 min and 23 h respectively after mycoplasma death. In the first assay, the first infected bird was detected on the 13th day. In the second trial, culturable M. synoviae or viable M. synoviae were detected in the isolator for 3 or 4 to 5 days respectively after depopulation of the birds of the first assay whereas the first culture positive tracheal swabs were detected on the 33rd day, after IB inoculation. In the third experiment, the first infected birds were detected on the 54th day. Thus, the different assays showed that M. synoviae contaminated material (dust, feathers and food) can infect chicks, sometimes after remarkably long silent periods. Mycoplasma synoviae / chicken / environment / transmission

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Section: Discussionsupporting

confidence: 91%

Experimental evidence of indirect transmission of Mycoplasma synoviae

et al. 2005

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“…Therefore, viruses attenuated by passage in embryonated eggs are tested for both safety and efficacy. Another factor to consider is vaccine ''stability'', whether vaccines can ''revert'' to virulence when backpassaged in chickens (Hopkins & Yoder, 1984, 1986, which could occur in commercial flocks.…”

Section: Introductionmentioning

confidence: 99%

Rapid selection in chickens of subpopulations within ArkDPI-derived infectious bronchitis virus vaccines

Santen

Toro

2008

Avian Pathology

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We examined spike (S) gene sequences of the virus populations of four different commercial ArkDPI-derived infectious bronchitis coronavirus vaccines before and during a single passage in specific pathogen free chickens. We found different degrees of genetic heterogeneity among the four vaccines before passage in chickens, ranging from no apparent heterogeneity to heterogeneity in 20 positions in the S gene. In all except one position, nucleotide differences were non-synonymous. The majority of amino acid differences were in the S1 subunit of the protein. For three of the four ArkDPI-derived vaccines, a single subpopulation with an S gene sequence distinct from the vaccine majority consensus at 5 to 11 codons was selected in chickens within 3 days after ocular vaccination. In contrast, we obtained no evidence for selection of specific subpopulations of the fourth ArkDPI-derived vaccine or Massachusetts or DE072 serotype vaccines. The virus subpopulations within each vaccine selected by chickens are similar in their S1 gene sequences, but distinct in the 3? portion of the S2 subunit gene for each of the three vaccines. In the S1 gene, the selected subpopulations are more similar to the virulent parental ArkDPI isolate than to the predominant vaccine population. The different proportions of distinct subpopulations in Ark vaccines apparently more fit for replication in the respiratory tract of chickens might cause different degrees of damage to respiratory epithelium and/or immune responses in vaccinated chickens. Sequence comparisons provided no evidence to support that ArkDPI-like field isolates were derived directly from host-selected vaccine virus subpopulations.

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“…However, the origin of the Japanese isolates of the 4/91 genotype, especially in relation to the vaccine strain, has been uncertain. Recombination with field isolates and reversion to virulence has been reported for the IBV vaccine [7,10]. Therefore, it is important to verify the relationship between field isolates and the vaccine strain of showed that the S1 sequence simirality to the 4/91 vaccine strain was high.…”

Section: Discussionmentioning

confidence: 99%

“…Vaccines have generally been effective in controlling clinical disease associated with IBV infections, but new variants may continue to emerge and cause clinical disease and production problems in vaccinated flocks [8,18]. Some studies [7,10] have reported frequent isolation of isolates related to vaccine strains from diseased flocks in the field, and reversion of the virulence of vaccine strains and recombination has been suspected.…”

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confidence: 99%