Hartshorn Kevan L, White Mitchell R, Tecle Tesfaldet, Tornoe Ida, Sorensen Grith L, Crouch Erika C, Holmskov Uffe
Boston University School of Medicine, Department of Medicine, Boston, MA, USA.
Respir Res. 2007 Feb 5;8(1):9. doi: 10.1186/1465-9921-8-9.
Surfactant protein D (SP-D) plays important roles in innate host defense against influenza A virus (IAV) infection. Common human polymorphisms of SP-D have been found in many human populations and associated with increased risk of certain infections. We recently reported that the Thr/Thr 11 form of SP-D is associated with low serum levels and assembles predominantly as trimers as opposed to the more common multimeric forms of SP-D.
Preliminary experiments were done to establish the effects of different monoclonal antibodies against SP-D on ability of SP-D to bind to or neutralize the virus. We then purified natural human trimeric and multimeric forms of SP-D from amniotic fluid and tested ability of these preparations to bind to IAV, to inhibit infectivity and hemagglutination activity of IAV in vitro.
In initial experiments mAbs directed against different areas on the CRD of SP-D were found to have differing effects on antiviral activity. Using an mAb that did not interfere with antiviral activity of SP-D, we confirm that natural SP-D trimers had reduced ability to bind to IAV. In addition, the trimers had reduced ability to neutralize IAV as compared to natural human SP-D multimers as well as reduced hemagglutination inhibiting activity against several strains of IAV. Natural SP-D trimers also had different interactions with human neutrophil peptide defensins (HNPs) in viral neutralization assays as compared to multimeric SP-D.
These studies indicate that a common human polymorphic form of SP-D may modulate host defense against IAV and give impetus to clinical studies correlating this genotype with risk for IAV infection in susceptible groups. We also show that mAbs directed against different areas on the carbohydrate recognition domain of SP-D can be useful for dissecting out different functional properties of the protein.
表面活性蛋白D（SP-D）在机体抵御甲型流感病毒（IAV）感染的天然免疫防御中发挥重要作用。在许多人群中已发现SP-D存在常见的人类多态性，且与某些感染风险增加相关。我们最近报道，SP-D的苏氨酸/苏氨酸11形式与低血清水平相关，并且主要组装为三聚体，而不是更常见的多聚体形式的SP-D。
进行初步实验以确定不同抗SP-D单克隆抗体对SP-D结合或中和病毒能力的影响。然后我们从羊水纯化天然人三聚体和多聚体形式的SP-D，并测试这些制剂结合IAV、在体外抑制IAV感染性和血凝活性的能力。
在初步实验中，发现针对SP-D CRD不同区域的单克隆抗体对抗病毒活性有不同影响。使用一种不干扰SP-D抗病毒活性的单克隆抗体，我们证实天然SP-D三聚体与IAV的结合能力降低。此外，与天然人SP-D多聚体相比，三聚体中和IAV的能力降低，并且对几种IAV毒株的血凝抑制活性也降低。在病毒中和试验中，与多聚体SP-D相比，天然SP-D三聚体与人类中性粒细胞肽防御素（HNP）也有不同的相互作用。
这些研究表明，SP-D常见的人类多态性形式可能调节机体对IAV的防御，并推动将该基因型与易感人群中IAV感染风险相关联的临床研究。我们还表明，针对SP-D碳水化合物识别域不同区域的单克隆抗体可用于剖析该蛋白的不同功能特性。
