Jia Q, Hogle J M, Hashikawa T, Nomoto A
Department of Microbiology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
J Virol. 2001 Dec;75(23):11766-72. doi: 10.1128/JVI.75.23.11766-11772.2001.
SA virus, a mutant of the Mahoney strain of type 1 poliovirus (PV1/Mahoney), replicates specifically in the spinal cords of mice and causes paralysis, although the PV1/Mahoney strain does not show any mouse neurovirulence (Q. Jia, S. Ohka, K. Iwasaki, K. Tohyama, and A. Nomoto, J. Virol. 73:6041-6047, 1999). The key mutation site for the mouse neurovirulence of SA was mapped to nucleotide (nt) 928 of the genome (A to G), resulting in the amino acid substitution of Met for Ile at residue 62 within the capsid protein VP4 (VP4062). A small-plaque phenotype of SA appears to be indicative of its mouse-neurovirulent phenotype. To identify additional amino acid residues involved in the host range determination of PV, a total of 14 large-plaque (LP) variants were isolated from a single point mutant, Mah/I4062M, that showed the SA phenotype. All the LP variants no longer showed any mouse neurovirulence when delivered via an intraspinal inoculation route. Of these, 11 isolates had a back mutation at nt 928 (G to A) that restored the nucleotide of the PV1/Mahoney type. The reversions of the remaining three isolates (LP8, LP9, and LP14) were mediated by a second site mutation. Molecular genetic analysis involving recombinants between Mah/I4062M and the LP variants revealed that the mere substitution of an amino acid residue at position 107 in VP1 (Val to Leu) (LP9), position 33 in VP2 (Val to Ile) (LP14), or position 231 in VP3 (Ile to Thr) (LP8) was sufficient to restore the PV1/Mahoney phenotype. These amino acid residues are located either on the surface or inside of the virus particle. Our results indicate that the mouse neurovirulence of PV is determined by the virion surface structure, which is formed by all four capsid proteins.
SA病毒是1型脊髓灰质炎病毒（PV1/Mahoney）马奥尼株的突变体，它专门在小鼠脊髓中复制并导致瘫痪，尽管PV1/Mahoney株未显示出任何小鼠神经毒性（Q. Jia、S. Ohka、K. Iwasaki、K. Tohyama和A. Nomoto，《病毒学杂志》73:6041 - 6047，1999年）。SA小鼠神经毒性的关键突变位点被定位到基因组的核苷酸（nt）928（A到G），导致衣壳蛋白VP4内第62位氨基酸由异亮氨酸替换为甲硫氨酸（VP4062）。SA的小噬菌斑表型似乎表明其小鼠神经毒性表型。为了鉴定参与脊髓灰质炎病毒宿主范围决定的其他氨基酸残基，从表现出SA表型的单点突变体Mah/I4062M中总共分离出14个大噬菌斑（LP）变体。当通过脊髓内接种途径接种时，所有LP变体均不再显示任何小鼠神经毒性。其中，11个分离株在nt 928处发生了回复突变（G到A），恢复了PV1/Mahoney型的核苷酸。其余三个分离株（LP8、LP9和LP14）的回复是由第二位点突变介导的。涉及Mah/I4062M与LP变体之间重组体的分子遗传学分析表明，仅VP1中第107位氨基酸残基（缬氨酸替换为亮氨酸）（LP9）、VP2中第33位氨基酸残基（缬氨酸替换为异亮氨酸）（LP14）或VP3中第231位氨基酸残基（异亮氨酸替换为苏氨酸）（LP8）的替换就足以恢复PV1/Mahoney表型。这些氨基酸残基位于病毒颗粒的表面或内部。我们的结果表明脊髓灰质炎病毒的小鼠神经毒性由由所有四种衣壳蛋白形成的病毒粒子表面结构决定。
