Weaver S C, Pfeffer M, Marriott K, Kang W, Kinney R M
Center for Tropical Diseases and Department of Pathology, University of Texas Medical Branch, Galveston 77555-0609, USA.
Am J Trop Med Hyg. 1999 Mar;60(3):441-8. doi: 10.4269/ajtmh.1999.60.441.
Epizootics of Venezuelan equine encephalitis (VEE) involving subtype IAB viruses occurred sporadically in South, Central and North America from 1938 to 1973. Incompletely inactivated vaccines have long been suspected as a source of the later epizootics. We tested this hypothesis by sequencing the PE2 glycoprotein precursor (1,677 nucleotides) or 26S/nonstructural protein 4 (nsP4) genome regions (4,490 nucleotides) for isolates representing most major outbreaks. Two distinct IAB genotypes were identified: 1) 1940s Peruvian strains and 2) 1938-1973 isolates from South, Central, and North America. Nucleotide sequences of these two genotypes differed by 1.1%, while the latter group showed only 0.6% sequence diversity. Early VEE virus IAB strains that were used for inactivated vaccine preparation had sequences identical to those predicted by phylogenetic analyses to be ancestors of the 1960s-1970s outbreaks. These data support the hypothesis of a vaccine origin for many VEE outbreaks. However, continuous, cryptic circulation of IAB viruses cannot be ruled out as a source of epizootic emergence.
1938年至1973年期间，涉及IAB亚型病毒的委内瑞拉马脑炎（VEE） epizootics在南美洲、中美洲和北美洲零星发生。长期以来，人们一直怀疑不完全灭活疫苗是后来epizootics的一个来源。我们通过对代表大多数主要疫情的分离株的PE2糖蛋白前体（1677个核苷酸）或26S/非结构蛋白4（nsP4）基因组区域（4490个核苷酸）进行测序来检验这一假设。鉴定出两种不同的IAB基因型：1）20世纪40年代的秘鲁毒株和2）1938年至1973年来自南美洲、中美洲和北美洲的分离株。这两种基因型的核苷酸序列相差1.1%，而后一组仅显示0.6%的序列多样性。用于制备灭活疫苗的早期VEE病毒IAB毒株的序列与系统发育分析预测的20世纪60年代至70年代疫情的祖先序列相同。这些数据支持许多VEE疫情起源于疫苗的假设。然而，不能排除IAB病毒的持续、隐匿性传播是epizootic出现的一个来源。 （注：“epizootics”可能是“ epizootic”的复数形式，意为“动物流行病”，但结合语境这里翻译为“epizootics”不太准确，推测原文可能有误，正常应该是“epizootic”，你可根据实际情况进一步确认。）
