Cameron-Wilson C L, Pandolfino Y A, Zhang H Y, Pozzeto B, Archard L C
Charing Cross and Westminster Medical School, London, UK.
Clin Diagn Virol. 1998 Apr;9(2-3):99-105. doi: 10.1016/s0928-0197(98)00008-7.
Coxsackievirus B3 (CVB3) causes myocarditis in the SWR (H2q) mouse model and persistence of CVB3 in myocardium disposes to the development of dilated cardiomyopathy. An attenuated strain of CVB3 has been isolated, sequenced and several candidate mutations for attenuation identified. Derivation of a revertant to cardiovirulence allows the significance of these mutations to be assessed.
To ascertain which candidate mutation(s) determine(s) the attenuated phenotype.
A revertant to cardiovirulence was isolated following passage through severe combined immunodeficient disease (SCID) mouse heart. The 5'-non-translated region (NTR) and region coding for capsid proteins were sequenced and compared to the wildtype and attenuant.
There are five candidates for attenuation: (1) A-G at base 580 in the 5'-NTR; (2) A-T at base 690 in the 5'-NTR; (3) CG-GC at bases 1401/2 (Thr to Ser at amino acid 151 in VP2); (4) AA-GT at bases 2691/2 (Lys to Ser at amino acid 80 in VP1); (5) A-G at base 2916 (Asp to Gly at amino acid 155 in VP1). It was shown previously that mutations at 580, 690 and 2691/2 are not important in attenuation. Additionally, there are three novel mutations in the coding region of the revertant and one in the 5'-NTR which are unlikely to be relevant for attenuation as they are not present in the attenuant. Of nucleotide changes seen at 1401/2 and 2916 in the attenuant, only 2916 reverts to the wildtype sequence and so is a strong candidate for a determinant of attenuation.
柯萨奇病毒B3（CVB3）在SWR（H2q）小鼠模型中可引发心肌炎，CVB3在心肌中的持续存在会导致扩张型心肌病的发展。一株减毒的CVB3毒株已被分离、测序，并确定了几个导致减毒的候选突变。构建回复到心脏毒性的毒株有助于评估这些突变的意义。
确定哪些候选突变决定了减毒表型。
通过严重联合免疫缺陷病（SCID）小鼠心脏传代后分离出回复到心脏毒性的毒株。对5'-非翻译区（NTR）和衣壳蛋白编码区进行测序，并与野生型和减毒株进行比较。
有五个减毒候选位点：（1）5'-NTR中第580位碱基由A变为G；（2）5'-NTR中第690位碱基由A变为T；（3）第1401/2位碱基由CG变为GC（VP2中第151位氨基酸由苏氨酸变为丝氨酸）；（4）第2691/2位碱基由AA变为GT（VP1中第80位氨基酸由赖氨酸变为丝氨酸）；（5）第2916位碱基由A变为G（VP1中第155位氨基酸由天冬氨酸变为甘氨酸）。先前已表明，580、690和2691/2位的突变对减毒并不重要。此外，回复毒株的编码区有三个新突变，5'-NTR中有一个新突变，由于这些突变在减毒株中不存在，因此不太可能与减毒相关。在减毒株中1401/2和2916位观察到的核苷酸变化中，只有2916位回复到野生型序列，因此是减毒决定因素的有力候选位点。
