Domanska-Blicharz Katarzyna, Sajewicz-Krukowska Joanna, Lisowska Anna, Opolska Justyna, Tarasiuk Karolina, Dziadek Kamila
Department of Virology and Viral Animal Diseases, National Veterinary Research Institute, al. Partyzantów 57, 24-100 Puławy, Poland.
Int J Mol Sci. 2025 Apr 28;26(9):4200. doi: 10.3390/ijms26094200.
Infectious bronchitis virus (IBV) of the GI-23 lineage, which first emerged in the Middle East in the late 1990s, has since spread worldwide. The factors driving its expansion, whether human involvement, wild bird migration, or the virus's biological traits, are still unclear. This study aimed to trace the genome evolution of GI-23 IBV in chickens and its adaptability to quails, which are susceptible to both gamma- and deltacoronaviruses. Thirty specific-pathogen-free (SPF) birds, aged between two and three weeks, were used. Initially, three birds were inoculated with the G052/2016 IBV via the oculo-nasal route. On the third day post-infection (dpi), oropharyngeal swabs were collected from the whole group, pooled, and subsequently used to infect three next birds. This process was repeated nine more times during consecutive IBV passages (P-I-P-X), and eventually, virus sequencing was performed using Next-Generation Sequencing (NGS). The obtained results showed that quails were not susceptible to the IBV GI-23 lineage, as the virus RNA was detected in low amounts only during the first passage (QP-I) with no further detections in later rounds of IBV passaging. In chickens, only mild diarrhea symptoms appeared in a few individuals. The NGS analysis identified sixty-two single nucleotide variants (SNVs), thirty of which caused amino acid changes, twenty-eight were synonymous, and one SNV introduced a stop codon. Three SNVs were found in untranslated regions. However, none of these SNVs lasted beyond seven passages, with forty-four being unique SNVs. The Shannon entropy values measured during passages varied for , , , , , and genes, with overall genome complexity peaking at CP-VI and CP-X. The highest complexity was observed in the (CP-X) and genes (CP-IV, CP-VI, CP-VIII, and CP-X). Along with the gene that was under positive selection, eight codons in were also positively selected. These findings suggest that even in an adapted host, IBV variability does not stabilize without immune pressure, indicating continuous molecular changes within its genome.
GI-23谱系的传染性支气管炎病毒（IBV）于20世纪90年代末首次出现在中东地区，此后已传播至全球。推动其传播的因素，无论是人类活动、野生鸟类迁徙，还是病毒的生物学特性，仍不明确。本研究旨在追踪鸡体内GI-23 IBV的基因组进化及其对鹌鹑的适应性，鹌鹑对γ冠状病毒和δ冠状病毒均易感。使用了30只2至3周龄的无特定病原体（SPF）鸟类。最初，通过眼鼻途径给3只鸟接种G052/2016 IBV。在感染后第3天（dpi），从整个群体中采集口咽拭子，混合后用于感染接下来的3只鸟。在连续的IBV传代过程（P-I-P-X）中，这个过程又重复了9次，最终使用下一代测序（NGS）进行病毒测序。获得的结果表明，鹌鹑对IBV GI-23谱系不敏感，因为仅在第一轮传代（QP-I）时检测到少量病毒RNA，在后续的IBV传代中未进一步检测到。在鸡中，只有少数个体出现轻度腹泻症状。NGS分析鉴定出62个单核苷酸变异（SNV），其中30个导致氨基酸变化，28个是同义突变，1个SNV引入了终止密码子。在非翻译区发现了3个SNV。然而，这些SNV均未持续超过7代，其中44个是独特的SNV。传代过程中测得的香农熵值在、、、、和基因中有所不同，基因组整体复杂性在CP-VI和CP-X时达到峰值。在（CP-X）和基因（CP-IV、CP-VI、CP-VIII和CP-X）中观察到最高的复杂性。除了处于正选择状态的基因外，中的8个密码子也受到正选择。这些发现表明，即使在适应的宿主中，没有免疫压力，IBV的变异性也不会稳定，这表明其基因组内存在持续的分子变化。
