Gorziglia M, Hoshino Y, Buckler-White A, Blumentals I, Glass R, Flores J, Kapikian A Z, Chanock R M
Proc Natl Acad Sci U S A. 1986 Sep;83(18):7039-43. doi: 10.1073/pnas.83.18.7039.
Within the past few years, rotavirus strains were recovered from four discrete prolonged outbreaks of infection in newborn nurseries in which affected infants failed to develop significant symptoms. The virus strains recovered from each outbreak belonged to a different human rotavirus serotype and thus each of the four human rotavirus serotypes was associated with asymptomatic infection of neonates. Marked conservation of sequence was observed among the fourth genes of the nursery rotavirus strains in a previous study using RNA X RNA hybridization, while a different conserved set of fourth gene sequences was identified among virulent human rotaviruses representing the four known serotypes. In the present study, this sequence dimorphism was further evaluated by comparing the sequence of the region of the fourth gene of virulent and asymptomatic human rotaviruses that codes for the VP8 protein, downstream cleavage sites, and the NH2 terminus of VP5. The corresponding sequences of a simian rotavirus were also determined. The fourth segment (+) strand RNA has a 5' conserved nontranslated sequence of nine nucleotides and encodes a VP8 protein of 240 amino acids in human rotavirus strains and 241 amino acids in simian rotavirus strains. Human and simian rotaviruses exhibit many similarities in this region of their genome, including identical NH2-terminal amino acid sequences, conservation of arginine at the two trypsin cleavage sites, and the position of a cysteine residue. Alignment of amino acid sequences of the VP8 protein, the downstream cleavage region, and the NH2 terminus of VP5 of asymptomatic and virulent human rotavirus strains indicates a high degree of homology (96% or more) among the asymptomatic viruses (serotypes 1, 2, 3, and 4), while homology between asymptomatic strains and virulent viruses is considerably less (68-72%). A high degree of conservation of amino acid sequence (92-97%) is also observed among three of the virulent strains (serotypes 1, 3, and 4). At 48 positions in the protein sequence of VP8, the cleavage region, and the NH2 terminus of VP5, an amino acid is conserved among asymptomatic rotaviruses, while a different amino acid is conserved among virulent rotaviruses. Notably, three of these differences are located within the cleavage region between VP8 and VP5. These findings suggest that the fourth genes of virulent and asymptomatic human rotavirus strains represent two lines of divergent evolution from a common ancestor. Also, it is possible that this sequence dimorphism may be responsible in part for the difference in virulence between these two groups of human rotaviruses.
在过去几年里，从新生儿保育室四次不同的持续性感染暴发中分离出了轮状病毒毒株，受感染的婴儿未出现明显症状。从每次暴发中分离出的病毒毒株属于不同的人轮状病毒血清型，因此这四种人轮状病毒血清型均与新生儿无症状感染有关。在之前一项使用RNA X RNA杂交技术的研究中，观察到保育室轮状病毒毒株的第四基因之间存在显著的序列保守性，而在代表四种已知血清型的致病性人轮状病毒中鉴定出了另一组不同的第四基因保守序列。在本研究中，通过比较致病性和无症状性人轮状病毒第四基因区域的序列，进一步评估了这种序列二态性，该区域编码VP8蛋白、下游切割位点以及VP5的NH2末端。还测定了一种猿猴轮状病毒的相应序列。第四片段（+）链RNA有一个9个核苷酸的5'保守非翻译序列，在人轮状病毒毒株中编码一个240个氨基酸的VP8蛋白，在猿猴轮状病毒毒株中编码一个241个氨基酸的VP8蛋白。人轮状病毒和猿猴轮状病毒在其基因组的这一区域表现出许多相似性，包括相同的NH2末端氨基酸序列、两个胰蛋白酶切割位点处精氨酸的保守性以及一个半胱氨酸残基的位置。无症状性和致病性人轮状病毒毒株的VP8蛋白、下游切割区域以及VP5的NH2末端的氨基酸序列比对表明，无症状性病毒（血清型1、2、3和4）之间具有高度同源性（96%或更高），而无症状性毒株与致病性病毒之间的同源性则低得多（68 - 72%）。在三种致病性毒株（血清型1、3和4）之间也观察到高度的氨基酸序列保守性（92 - 97%）。在VP8蛋白、切割区域以及VP5的NH2末端的蛋白质序列中的48个位置，无症状性轮状病毒中保守着一种氨基酸，而致病性轮状病毒中保守着另一种不同的氨基酸。值得注意的是，其中三个差异位于VP8和VP5之间的切割区域内。这些发现表明，致病性和无症状性人轮状病毒毒株的第四基因代表了从一个共同祖先开始的两条不同进化路线。此外，这种序列二态性可能部分导致了这两组人轮状病毒在毒力上的差异。
