Chuang Yu-Chen, Tseng Jen-Chih, Yang Jing-Xing, Liu Yi-Ling, Yeh Da-Wei, Lai Chao-Yang, Yu Guann-Yi, Hsu Li-Chung, Huang Chun-Ming, Chuang Tsung-Hsien
Immunology Research Center, National Health Research Institutes, Zhunan, Miaoli 35053, Taiwan.
Department of Medical Laboratory Science and Biotechnology, Asia University, Taichung 41354, Taiwan.
Vaccines (Basel). 2020 Nov 2;8(4):639. doi: 10.3390/vaccines8040639.
CpG-oligodeoxynucleotides (CpG-ODNs) mimicking the function of microbial CpG-dideoxynucleotides containing DNA (CpG-DNA) are potent immune stimuli. The immunostimulatory activity and the species-specific activities of a CpG-ODN depend on its nucleotide sequence properties, including CpG-hexamer motif types, spacing between motifs, nucleotide sequence, and length. Toll-like receptor (TLR) 9 is the cellular receptor for CpG-ODNs in mammalian species, while TLR21 is the receptor in avian species. Mammalian cells lack TLR21, and avian cells lack TLR9; however, both TLRs are expressed in fish cells. While nucleotide sequence properties required for a CpG-ODN to strongly activate mammalian TLR9 and its species-specific activities to different mammalian TLR9s are better studied, CpG-ODN activation of TLR21 is not yet well investigated. Here we characterized chicken and duck TLR21s and investigated their activation by CpG-ODNs. Chicken and duck TLR21s contain 972 and 976 amino acid residues, respectively, and differ from TLR9s as they do not have an undefined region in their ectodomain. Cell-based TLR21 activation assays were established to investigate TLR21 activation by different CpG-ODNs. Unlike grouper TLR21, which was preferentially activated by CpG-ODN with a GTCGTT hexamer motif, chicken and duck TLR21s do not distinguish among different CpG-hexamer motifs. Additionally, these two poultry TLR21s were activated by CpG-ODNs with lengths ranging from 15 to 31 nucleotides and with different spacing between CpG-hexamer motifs. These suggested that compared to mammalian TLR9 and grouper TLR21, chicken and duck TLR21s have a broad CpG-ODN sequence recognition profile. Thus, they could also recognize a wide array of DNA-associated molecular patterns from microbes. Moreover, CpG-ODNs are being investigated as antimicrobial agents and as vaccine adjuvants for different species. This study revealed that there are more optimized CpG-ODNs that can be used in poultry farming as anti-infection agents compared to CpG-ODN choices available for other species.
模仿含微生物CpG-二脱氧核苷酸DNA（CpG-DNA）功能的CpG-寡脱氧核苷酸（CpG-ODN）是强大的免疫刺激剂。CpG-ODN的免疫刺激活性和物种特异性活性取决于其核苷酸序列特性，包括CpG六聚体基序类型、基序之间的间隔、核苷酸序列和长度。Toll样受体（TLR）9是哺乳动物物种中CpG-ODN的细胞受体，而TLR21是禽类物种中的受体。哺乳动物细胞缺乏TLR21，禽类细胞缺乏TLR9；然而，这两种TLR都在鱼类细胞中表达。虽然对CpG-ODN强烈激活哺乳动物TLR9所需的核苷酸序列特性及其对不同哺乳动物TLR9的物种特异性活性已有较好研究，但对TLR21的CpG-ODN激活尚未充分研究。在此，我们对鸡和鸭的TLR21进行了表征，并研究了它们被CpG-ODN激活的情况。鸡和鸭的TLR21分别含有972和976个氨基酸残基，与TLR9不同，它们的胞外结构域没有未定义区域。建立了基于细胞的TLR21激活试验，以研究不同CpG-ODN对TLR21的激活作用。与优先被具有GTCGTT六聚体基序的CpG-ODN激活的石斑鱼TLR21不同，鸡和鸭的TLR21不能区分不同的CpG六聚体基序。此外，这两种禽类TLR21被长度为15至31个核苷酸且CpG六聚体基序之间间隔不同的CpG-ODN激活。这些表明，与哺乳动物TLR9和石斑鱼TLR21相比，鸡和鸭的TLR21具有广泛的CpG-ODN序列识别谱。因此，它们也能识别来自微生物的多种与DNA相关的分子模式。此外，CpG-ODN正在作为抗菌剂和不同物种的疫苗佐剂进行研究。这项研究表明，与可用于其他物种的CpG-ODN选择相比，有更多优化的CpG-ODN可用于家禽养殖作为抗感染剂。
