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    A deletion within glycoprotein L of Marek's disease virus (MDV) field isolates correlates with a decrease in bivalent MDV vaccine efficacy in contact-exposed chickens (2009)

    Art
    Zeitschriftenartikel / wissenschaftlicher Beitrag
    Autoren
    Tavlarides-Hontz, Phaedra
    Kumar, Pankaj M
    Amortegui, Juliana Rojas
    Osterrieder, Nikolaus
    Parcells, Mark S
    Quelle
    Avian diseases; 53(2) — S. 287–296
    ISSN: 0005-2086
    Sprache
    Englisch
    Verweise
    Pubmed: 19630238
    Kontakt
    Institut für Virologie

    Robert-von-Ostertag-Str. 7-13
    Gebäude 35
    14163 Berlin
    +49 30 838 51833
    viro@zedat.fu-berlin.de

    Abstract / Zusammenfassung

    We examined the functional role of a naturally occurring deletion within the glycoprotein L (gL) gene of Marek's disease virus (MDV) field isolates. We previously showed that this mutation incrementally increased the virulence of an MDV in contact-exposed SPF leghorn chickens, when chickens shedding this virus were co-infected with herpesvirus of turkeys (HVT). In our present study, we examined this mutation using two stocks of the very virulent plus (vv+)MDV strain TK, one of which harbored this deletion (TK1a) while the other did not (TK2a). We report that TK1a replicating in vaccinated chickens overcame bivalent (HVT/SB1) vaccine protection in contact-exposed chickens. Treatment groups exposed to vaccinated chickens inoculated with a 1:1 mix of TK1a and TK2a showed decreased bivalent vaccine efficacy, and this decrease correlated with the prevalence of the gL deletion indicative of TK1a. These results were also found using quadruplicate treatment groups and bivalently vaccinated chickens obtained from a commercial hatchery. As this deletion was found in 25 out of 25 recent field isolates from Delaware, Maryland, North Carolina, Pennsylvania, and Virginia, we concluded that there is a strong selection for this mutation, which appears to have evolved in HVT or bivalently vaccinated chickens. This is the first report of a mutation in a vv+MDV field strain for which a putative biological phenotype has been discerned. Moreover, this mutation in gL has apparently been selected in MDV field isolates through Marek's disease vaccination.