Phylogenetic analysis of avian retroviruses with neuropathogenicity in central nervous system

禽白血病病毒（ALV）主要引起鸡的造血肿瘤，而属于ALV A亚群的禽胶质瘤诱导病毒（FGV）可引起鸡的星形细胞瘤。富山A动物园饲养的家禽被认为是日本其他动物园FGV感染的来源。然而，FGV在神经系统中获得独特致癌性的背景和过程尚不清楚。首先，为了使用巢式PCR检测FGV，设计了特定于3'非翻译区（UTR）的引物，并建立了PCR-协议。A动物园131只日本鸡的巢式PCR检测结果显示，FGV的感染率为40%，其他3个动物园共129只接受A动物园鸡蛋或雏鸡的鸡的感染率为26% ~ 56%。系统发育分析表明，14个分离的alv的3′utr（包括FGV特异性序列）具有较高的序列同一性，且与FGV密切相关。其次，对与A动物园禽类没有亲缘关系的鸡进行了流行病学调查。日本家禽的祖先被认为是在江户时代从东南亚带到日本的。沿传播路径采集印度尼西亚、菲律宾、韩国和日本264只鸡的羽浆和阴囊拭子。29只鸡（包括9只国外鸡）巢式PCR阳性，扩增产物与FGV相应区域的核苷酸序列同源性达98%。在日本从这些鸡中分离出6株FGV。另一方面，从日本家禽胶质瘤和皮下间充质瘤患者的脑组织中分离到不同的ALV菌株（Tyms_90）。另外2只日本家禽分别出现神经瘤和神经纤维瘤，并从后者身上分离到一株内源性1型（ev-1）基因座的ALV。这些结果表明，FGV突变体在日本的日本家禽中传播，与A动物园鸟类无关的少量国内外鸡感染了FGV，日本家禽感染了基因组中具有ev-1位点的其他alv，并在神经系统中表现出致癌性。综上所述，推测FGV已出现在A动物园之外，部分感染FGV的鸡被带到该动物园繁殖。少

Avian leukosis virus (ALV) mainly causes hematopoietic neoplasms in chicken, whereas fowl glioma-inducing virus (FGV), which belongs to ALV subgroup A, induces astrocytoma in chickens. Fowls kept in zoological garden A in Toyama have been considered as source for the FGV infection in other Japanese zoological gardens. However, the background and process how FGV acquired the unique oncogenicity in nervous system has not been clarified. At first, to detect FGV using nested PCR, primers were designed specific to the 3' untranslated region (UTR) and the PCR-protocol was established. The prevalence of FGV by the nested PCR in 131 Japanese fowls of zoological garden A was 40% and the prevalences in a total of 129 chickens in three other zoological gardens, which were received the eggs or chicks from the zoological garden A, were 26 to 56%. Phylogenetic analysis revealed that 3' UTRs, including the FGV-specific sequence, of the 14 isolated ALVs showed high sequence identity and a close relati … More onship with that of FGV. Secondly, the prevalence in chickens, which were not related by birth to any fowls of the zoological garden A, was examined. Ancestors of Japanese fowl are thought to be brought to Japan in the Edo era from Southeast Asia. Along the propagation path, feather pulps and cloaca swab were collected from 264 chickens in Indonesia, Philippines, South Korea and Japan. Twenty nine chickens, including 9 birds in the foreign countries, were positive for nested PCR and the amplified products of showed 98% nucleotide sequence homology to the corresponding region of FGV. Six strains of FGV were isolated from these chickens in Japan. On the other hand, different ALV strain (Tyms_90) was isolated from brains of layers affected with fowl glioma and subcutaneous mesenchymal neoplasm in Japan. Another two Japanese fowls in Japan showed perineurioma and neurofibroma, respectively and a strain of ALV having endogenous-1(ev-1) locus was isolated from the latter. These results suggest that mutants of FGV spread in Japanese fowls in Japan, that small number of domestic and foreign chickens unrelated to the birds in the zoological garden A is infected with FGV, and that Japanese fowls are infected with other ALVs having ev-1 locus in the genome and showing oncogenicity in nervous system. In conclusion, it is speculated that FGV has appeared outside of the zoological garden A and a part of FGV-infected chickens were brought to this garden and used for breeding. Less