Smith C A, Barnett B C, Thomas D B, Temoltzin-Palacios F
National Institute for Medical Research, London, UK.
J Exp Med. 1991 Apr 1;173(4):953-9. doi: 10.1084/jem.173.4.953.
Information on the antigenic structure of influenza hemagglutinin (HA) has been deduced previously from sequence analyses of laboratory mutant viruses selected, in vitro, with neutralizing monoclonal antibody (mAb) established exclusively from BALB/c (H-2d) mice; and there has been no attempt to investigate the influence of host genetic background, or natural route of infection, on the protective antibody repertoire. CBA/Ca mice are extremely sensitive to X31 virus infection, and in the present study a structural analysis was made of the antibody repertoire, by direct sequencing of the HA genes of laboratory mutant viruses selected, in ovo with mAb from CBA/Ca mice primed by natural infection with X31 virus at two different infectious doses. Single nucleotide substitutions in the HA genes of mutant viruses identified both novel and immunodominant antigenic sites on the HA1 subunit: a majority of mAbs, from different donors, were of the IgG2a isotype and were specific for HA1 158 Gly. In addition, novel laboratory mutants were obtained containing substitutions in the HA1 subunit that had not been reported previously for H3 subtype viruses, either natural variants or laboratory mutants, at residues: HA1 62 Ile----Arg; HA1 165 Asn----Ser (resulting in the loss of a N-glycosylation site); and HA1 273 Pro----Leu. Our findings suggest that host genetic background and/or a natural route of infection may be significant factors in the selection of different and distinct neutralizing antibody responses to influenza HA and therefore be of some relevance in our further understanding of the immune pressure for antigenic drift, and the immunogenic features of a protective antigen.
关于流感血凝素（HA）抗原结构的信息此前已从对在体外通过仅由BALB/c（H-2d）小鼠制备的中和单克隆抗体（mAb）筛选出的实验室突变病毒的序列分析中推导得出；且尚未有人尝试研究宿主遗传背景或自然感染途径对保护性抗体库的影响。CBA/Ca小鼠对X31病毒感染极为敏感，在本研究中，通过对在卵内用来自经两种不同感染剂量的X31病毒自然感染致敏的CBA/Ca小鼠的mAb筛选出的实验室突变病毒的HA基因进行直接测序，对抗体库进行了结构分析。突变病毒HA基因中的单核苷酸替换确定了HA1亚基上新的和免疫显性的抗原位点：来自不同供体的大多数mAb为IgG2a同种型，且对HA1 158 Gly具有特异性。此外，还获得了新的实验室突变体，其HA1亚基中的替换在H3亚型病毒（天然变体或实验室突变体）中此前尚未报道过，这些替换发生在以下残基处：HA1 62 Ile----Arg；HA1 165 Asn----Ser（导致一个N-糖基化位点丢失）；以及HA1 273 Pro----Leu。我们的研究结果表明，宿主遗传背景和/或自然感染途径可能是选择针对流感HA的不同且独特的中和抗体反应的重要因素，因此对于我们进一步理解抗原漂移的免疫压力以及保护性抗原的免疫原性特征具有一定相关性。
