Zhirnov O P, Manykin A A
D. I. Ivanovsky Research Institute of Virology, Russian Academy of Medical Sciences, Moscow, Russia,
Bull Exp Biol Med. 2015 Apr;158(6):776-80. doi: 10.1007/s10517-015-2860-6. Epub 2015 Apr 22.
Vesicles on the virion surface, which continued the lipoprotein membrane but had no spikes of virus glycoproteins hemagglutinin (HA) and neuraminidase (NA), were detected. These vesicles and virus particles were 18±7 and 103±12 nm in diameter, respectively, and, as a rule, one vesicle was found per virion. The locus of the external protrusion in the virion presumably corresponded to the site of virus budding during assembly in infected cell free from HA and NA spikes outside and M1 matrix protein inside, but enriched with ionic channel protein M2. Particles with vesicles constituted ~3-10% of the virus population produced in MDCK-H culture and containing uncleaved HA0 hemagglutinin. The content of vesicular virions increased slightly after trypsin cleavage HA0→HA1+HA2 and reached 10-15%. Exposure of the virus in acid medium (pH 4.3) led to a drastic increase of vesicular virions - to 60-80% for HA0 and HA1+HA2 virus. This was paralleled by changes in contrast permeability (for phosphotungstic acid). HA0 virions remained contrast-impermeable, while HA1+HA2 particles let the contrast in through the vesicles detected on the surface and were rapidly destroyed after incubation in acid medium. Hence, cleavage of the surface glycoprotein HA0 into HA1 and HA2 stimulated the acid-dependent permeability of the lipid membrane and led to attenuation of the ribonucleoprotein and protein matrix M1 contacts inside the virion.
在病毒粒子表面检测到了囊泡，这些囊泡延续了脂蛋白膜，但没有病毒糖蛋白血凝素（HA）和神经氨酸酶（NA）的刺突。这些囊泡和病毒粒子的直径分别为18±7纳米和103±12纳米，通常每个病毒粒子有一个囊泡。病毒粒子外部突出的位点大概对应于在感染细胞中组装期间病毒出芽的部位，外部没有HA和NA刺突，内部有M1基质蛋白，但富含离子通道蛋白M2。带有囊泡的粒子占在MDCK-H培养物中产生的、含有未切割的HA0血凝素的病毒群体的约3-10%。胰蛋白酶将HA0切割为HA1+HA2后，囊泡状病毒粒子的含量略有增加，达到10-15%。病毒在酸性介质（pH 4.3）中暴露导致囊泡状病毒粒子急剧增加——HA0和HA1+HA2病毒分别增加到60-80%。这与对比通透性（对于磷钨酸）的变化平行。HA0病毒粒子仍不具有对比通透性，而HA1+HA2粒子使对比剂通过在表面检测到的囊泡进入，并在酸性介质中孵育后迅速被破坏。因此，表面糖蛋白HA0切割为HA1和HA2刺激了脂膜的酸依赖性通透性，并导致病毒粒子内部核糖核蛋白与蛋白质基质M1的接触减弱。
