Pham Quynh N, Biacchesi Stéphane, Skiadopoulos Mario H, Murphy Brian R, Collins Peter L, Buchholz Ursula J
Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892-8007, USA.
J Virol. 2005 Dec;79(24):15114-22. doi: 10.1128/JVI.79.24.15114-15122.2005.
Chimeric versions of recombinant human metapneumovirus (HMPV) were generated by replacing the nucleoprotein (N) or phosphoprotein (P) open reading frame with its counterpart from the closely related avian metapneumovirus (AMPV) subgroup C. In Vero cells, AMPV replicated to an approximately 100-fold-higher titer than HMPV. Surprisingly, the N and P chimeric viruses replicated to a peak titer that was 11- and 25-fold higher, respectively, than that of parental HMPV. The basis for this effect is not known but was not due to obvious changes in the efficiency of gene expression. AMPV and the N and P chimeras were evaluated for replication, immunogenicity, and protective efficacy in hamsters. AMPV was attenuated compared to HMPV in this mammalian host on day 5 postinfection, but not on day 3, and only in the nasal turbinates. In contrast, the N and P chimeras were reduced approximately 100-fold in both the upper and lower respiratory tract on day 3 postinfection, although there was little difference by day 5. The N and P chimeras induced a high level of neutralizing serum antibodies and protective efficacy against HMPV; AMPV was only weakly immunogenic and protective against HMPV challenge, reflecting antigenic differences. In African green monkeys immunized intranasally and intratracheally, the mean peak titer of the P chimera was reduced 100- and 1,000-fold in the upper and lower respiratory tracts, whereas the N chimera was reduced only 10-fold in the lower respiratory tract. Both chimeras were comparable to wild-type HMPV in immunogenicity and protective efficacy. Thus, the P chimera is a promising live HMPV vaccine candidate that paradoxically combines improved growth in vitro with attenuation in vivo.
通过用密切相关的禽偏肺病毒(AMPV)C亚组的核蛋白(N)或磷蛋白(P)开放阅读框替换重组人偏肺病毒(HMPV)的相应开放阅读框,构建了嵌合型HMPV。在Vero细胞中,AMPV的复制滴度比HMPV高约100倍。令人惊讶的是,N和P嵌合病毒的复制峰值滴度分别比亲本HMPV高11倍和25倍。这种效应的基础尚不清楚,但并非由于基因表达效率的明显变化。对AMPV以及N和P嵌合体在仓鼠中的复制、免疫原性和保护效力进行了评估。在感染后第5天,与HMPV相比,AMPV在这种哺乳动物宿主中减毒,但在第3天未减毒,且仅在鼻甲中减毒。相比之下,在感染后第3天,N和P嵌合体在上呼吸道和下呼吸道中的滴度均降低了约100倍,尽管到第5天时差异不大。N和P嵌合体诱导产生高水平的中和血清抗体,并对HMPV具有保护效力;AMPV的免疫原性和对HMPV攻击的保护作用较弱,这反映了抗原差异。在经鼻内和气管内免疫的非洲绿猴中,P嵌合体在上呼吸道和下呼吸道中的平均峰值滴度分别降低了100倍和1000倍,而N嵌合体在下呼吸道中的滴度仅降低了10倍。两种嵌合体在免疫原性和保护效力方面与野生型HMPV相当。因此,P嵌合体是一种有前景的HMPV活疫苗候选物,矛盾的是,它在体外生长改善的同时在体内减毒。