Molecular biology of avian infectious laryngotracheitis virus

Abstract

-Infectious laryngotracheitis virus (ILTV) is an alphaherpesvirus that causes an economically important chicken disease, which results in delayed growth, reduced egg production, and also frequently in death of the animals. After acute infection of the upper respiratory tract, the virus can establish latency in the central nervous system, and subsequent reactivations can lead to infection of naive chickens. For prevention of ILT, conventionally attenuated live vaccines are available. However, these vaccine strains are genetically not characterized, and reversions to a virulent phenotype occur. Although molecular analyses of ILTV are hampered by the lack of an optimal cell culture system, the complete nucleotide sequence of the ILTV genome has recently been elucidated, and several ILTV recombinants lacking nonessential, but virulence determining genes have been constructed. Animal trials indicated that genetically engineered stable gene deletion mutants are safe alternatives to the current vaccine strains. Furthermore, since live ILTV vaccines are suitable for fast and inexpensive mass administration, they are promising as vectors for immunogenic proteins of other chicken pathogens. Thus, immunization with ILTV recombinants expressing avian influenza virus hemagglutinin was shown to protect chickens against ILT and fowl plague. Using monospecific antisera and monoclonal antibodies several virion proteins of ILTV have been identified and characterized. Since they include immunogenic envelope glycoproteins, these results can contribute to the improvement of virus diagnostics, and to the development of marker vaccines.

Attenuation and protection efficacy of ORF C gene-deleted recombinant of infectious laryngotracheitis virus

“…Subsequently these strains regain virulence and are responsible for outbreaks of the disease worldwide (Menendez et al, 2014). In order to obtain more stable attenuated strains of ILTV, deletion of genes related to virulence has been extensively pursued (Fuchs et al, 2007). Twenty individual genes have been successfully deleted from the ILTV genome resulting in recombinants with a wide range of growth defects in vitro (Fuchs et al, 2007;Mundt et al, 2011;Pavlova et al, 2010Pavlova et al, , 2013.…”

“…In order to obtain more stable attenuated strains of ILTV, deletion of genes related to virulence has been extensively pursued (Fuchs et al, 2007). Twenty individual genes have been successfully deleted from the ILTV genome resulting in recombinants with a wide range of growth defects in vitro (Fuchs et al, 2007;Mundt et al, 2011;Pavlova et al, 2010Pavlova et al, , 2013. Among the 20 gene-deleted ILTV strains generated, only seven have been evaluated in vivo for attenuation and protection efficacy.…”

Replication characteristics of infectious laryngotracheitis virus in the respiratory and conjunctival mucosa

“…After an acute phase of infection, ILTV, like other alphaherpesviruses, establishes a lifelong latency within the trigeminal ganglion of the central nervous system. During stress, reactivation of the virus may occur, leading to the spread of ILTV to susceptible contact animals (Fuchs et al, 2007). The characteristic clinical signs of infectious laryngotracheitis during a mild form are nasal discharge, conjunctivitis and drops in egg production.…”

“…The characteristic clinical signs of infectious laryngotracheitis during a mild form are nasal discharge, conjunctivitis and drops in egg production. During the severe form, additional signs are gasping, bloody mucous expectoration, dyspnoea and death due to asphyxia (Fuchs et al, 2007).…”

Molecular detection and characterization of infectious laryngotracheitis virus (Gallid herpesvirus-1) from clinical samples of commercial poultry flocks in India

“…Clinical signs include extension of the neck, gasping, gurgling, rattling, and coughing of clotted blood [11,17]. ILTV usually causes a reduction in egg production and variable mortality ranging from 0 to 70 % [9]. The existence of ILT was first reported in India in 1964 [29], and recently, based on clinical and pathological observations presence of ILT virus infection in commercial layer flocks has been reported [30].…”