Route of challenge is critical in determining the clinical outcome of infection with a very virulent oncogenic herpesvirus, Marek's disease virus

Abstract

The majority of experimental studies examining Marek's disease virus infection have used parenteral injection of cell-associated virus. The aim of this study was to examine whether the route of entry of virus was critical in determining the outcome of infection. Susceptible (L7) and resistant (L6) White Leghorn chickens were infected with a very virulent Marek's disease virus, RB1B, by either the intra-abdominal or intra-tracheal route. Birds infected by the intra-tracheal route had earlier, higher or more sustained blood, spleen and lung viral concentrations than those infected by the intra-abdominal route. L7 birds had higher viral loads than L6 birds infected by the same route. Clinical outcomes reflected these data. Resistant birds infected by the intra-tracheal route had an increased prevalence of tumours and shorter survival times compared with those infected by the intra-abdominal route. Susceptible birds infected by the intra-tracheal route became paralysed 10 days after infection. L7 birds had shorter survival times and increased prevalences of tumours than L6 birds. The pathology and viraemia seen with intra-tracheal infection could not be fully replicated by increasing the dose in intra-abdominal infections. We conclude that instillation of infective dust produces a more aggressive infection that depends on the route of entry and form of virus, and not just on the challenge dose. © 2007 Houghton Trust Ltd

Early Replication in Pulmonary B Cells After Infection with Marek's Disease Herpesvirus by the Respiratory Route

“…Meq reaction mixtures included primers and probe to an avian housekeeping gene, ovotransferrin (Ovo), labeled with a second fluorescent dye (VIC TM ; Applied Biosystems). Raw data were normalized to a positive control included in every run to exclude plate-to-plate variation (14).…”

“…RNA was analyzed using primer and probe for cytokine transcripts (24) and viral transcripts (14). All cytokine=MDV reactions w e r e corrected f o r the amount of cellular RNA by using 28S RNA (housekeeping gene) as described for quantitative PCR reactions.…”

“…The microaerosolizer provides a simple and effective tool to introduce a standard dose of MDV in its native form into the trachea in a timed manner. We previously demonstrated the importance of the route and the form of the virus when parenteral infection with cell-associated virus was compared to intratracheal infection with native MDV for resistant and susceptible strains (14). Although 2.5 mg of dander contained 16 times more viral DNA com-pared to 1000 pfu of cell-associated virus (the doses used in the experiments), even increasing the infective dose of cell-associated virus 100 times could not replicate the timing of the clinical signs seen after intratracheal infection (14).…”

Virus de la Enfermedad de Marek: aproximación molecular al virus y respuesta inmune del hospedero

“…La respuesta de CD8+ (CTL) contra varias glicoproteínas de envoltura tiene un papel importante en el control de la infección del VEM, el fenotipo CTL expresado en aves es determinado por la expresión de CD3+ CD4-CD8+ TCRαβ1 igual al fenotipo expresado por células citotóxicas cuando hay inducción por cepas vacunales no oncogénicas de VEM; este tipo de respuesta CTL también tiene un papel importante en la resistencia genética a EM ya que puede ser expresada fenotípicamente en aves resistentes a la enfermedad debido a la reasociación genética al momento de formar las células específicas en la inmunidad adquirida 24,33 .…”

Chicken CD14, unlike mammalian CD14, is trans-membrane rather than GPI-anchored

“…Different cell populations (splenocytes, splenocytes stimulated with Concanavalin A [ConA] (1 mg/ml), bursal cells, bursal cells stimulated with phorbol myristate acetate [PMA] (500 ng/ml), thymocytes, thymocytes stimulated with phytohaemagglutinin [PHA] (25 mg/ml), peripheral blood monocytes and peripheral blood monocyte-derived macrophages) were obtained as described before [19]. In order to isolate different lymphocyte subsets, splenocytes were isolated as described [20]. Briefly, spleens were digested in Hank's buffered salt solution (HBSS) containing 556 mg/ml DNase I (Roche Diagnostics Ltd., Burgess Hill, West Sussex, UK) and 2.2 mg/ml collagenase D (Roche Diagnostics Ltd.) for 1 h. Cells were then collected into HBSS containing 10 mM EDTA and passed through a cell strainer.…”