Luke N R, Russo T A, Luther N, Campagnari A A
Department of Microbiology, State University of New York at Buffalo, Buffalo, New York 14214, USA.
Infect Immun. 1999 Feb;67(2):681-7. doi: 10.1128/IAI.67.2.681-687.1999.
Moraxella catarrhalis-induced otitis media continues to be a significant cause of infection in young children, prompting increased efforts at identifying effective vaccine antigens. We have previously demonstrated that M. catarrhalis expresses specific outer membrane proteins (OMPs) in response to iron limitation and that this organism can utilize transferrin and lactoferrin for in vitro growth. One of these proteins, which binds human transferrin, is OMP B1. As the human host presents a naturally iron-limited environment, proteins, like OMP B1, which are expressed in response to this nutritional stress are potential vaccine antigens. In this study, we have developed monoclonal antibody (MAb) 11C6, which reacts to a surface-exposed epitope of OMP B1 expressed by M. catarrhalis 7169. This antibody was used to clone ompB1, and sequence analysis suggested that OMP B1 is the M. catarrhalis homologue to the transferrin binding protein B described for pathogenic Neisseriaceae, Haemophilus influenzae, Actinobacillus pleuropneumoniae, and M. catarrhalis. Expression of recombinant OMP B1 on the surface of Escherichia coli confers transferrin binding activity, confirming that this protein is likely involved in iron acquisition. In addition, ompB1 was used to construct an isogenic mutant in M. catarrhalis 7169. This mutant, termed 7169b12, was used as the control in bactericidal assays designed to determine if OMP B1 elicits protective antibodies. In the presence of MAb 11C6 and human complement, wild-type 7169 demonstrated a 99% decline in viability, whereas the ompB1 isogenic mutant was resistant to this bactericidal activity. Further analysis with MAb 11C6 revealed the presence of this OMP B1 epitope on 31% of the clinical isolates tested. These data suggest that OMP B1 is a potential vaccine antigen against M. catarrhalis infections.
卡他莫拉菌引起的中耳炎仍然是幼儿感染的一个重要原因，这促使人们加大力度寻找有效的疫苗抗原。我们之前已经证明，卡他莫拉菌在铁限制条件下会表达特定的外膜蛋白（OMPs），并且这种细菌可以利用转铁蛋白和乳铁蛋白进行体外生长。其中一种与人转铁蛋白结合的蛋白是OMP B1。由于人类宿主呈现出天然的铁限制环境，像OMP B1这样在这种营养应激下表达的蛋白是潜在的疫苗抗原。在本研究中，我们开发了单克隆抗体（MAb）11C6，它能与卡他莫拉菌7169表达的OMP B1的表面暴露表位发生反应。该抗体被用于克隆ompB1，序列分析表明OMP B1是卡他莫拉菌中与致病性奈瑟菌科、流感嗜血杆菌、胸膜肺炎放线杆菌和卡他莫拉菌中描述的转铁蛋白结合蛋白B同源的蛋白。重组OMP B1在大肠杆菌表面的表达赋予了转铁蛋白结合活性，证实该蛋白可能参与铁的获取。此外，ompB1被用于构建卡他莫拉菌7169的同基因突变体。这个突变体，称为7169b12，在旨在确定OMP B1是否能引发保护性抗体的杀菌试验中用作对照。在MAb 11C6和人补体存在的情况下，野生型7169的活力下降了99%，而ompB1同基因突变体对这种杀菌活性具有抗性。用MAb 11C6进行的进一步分析显示，在所测试的31%的临床分离株中存在这种OMP B1表位。这些数据表明OMP B1是一种针对卡他莫拉菌感染的潜在疫苗抗原。
