Attenuation of a Field Strain of Infectious Laryngotracheitis Virus in Primary Chicken Culture Cells and Adaptation to Secondary Chicken Embryo Fibroblasts
Bibliographic record
Abstract
The establishment of commercial infectious laryngotracheitis virus (ILTV) live-modified vaccines has relied on serial passaging in chicken embryo (CEO) and tissue culture (TCO) for attenuation. The objective of this study was to attenuate and adapt a virulent CEO-related ILTV field strain (6340) in immortalized cells (LMH), primary chicken embryo kidney cells (CEK), chicken embryo liver cells (CEL), and chicken embryo fibroblasts (CEF). CEFs were refractory to parent ILTV, LMH cells produced low virus yields (~2.5 log10 TCID50 per mL), while CEK and CEL cells produced higher viral titers (≥log10 6.0 TCID50 per mL). After 52 passages in CELs, the cytopathic effect (CPE) was observed not only in hepatocytes but also in CEL fibroblasts. Once CPE was evident in CEL fibroblasts, 20 further passages in CEFs with viral titers reaching yields of ~4.4–5.5 log10 TCID50 per mL were performed. The attenuation of CEF-adapted viruses was evaluated after intra-tracheal and conjunctival inoculation in 28-day-old broilers by assessing clinical signs at five days post-inoculation (DPI). Virus CEL cells passages 80, 90, and 100, and CEF passages 10 and 20 were significantly attenuated compared to the parental strain. This is the first report of the attenuation of a virulent field CEO-related ILTV strain (RFLP Group V) in CEF cells—a cell type from a different embryonic germ layer (mesoderm) than ILTV target cells—the respiratory epithelium (endoderm). This finding underscores the potential use of CEF adaptation for the development of a live-attenuated ILTV vaccine.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".