Lo Passo C, Zippilli L, Angiolillo A, Costa I, Pernice I, Galbo R, Felici F, Beernink P T
Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Italy.
Department of Biosciences and Territory, University of Molise, Pesche (CB), Italy.
Heliyon. 2018 Apr 3;4(4):e00591. doi: 10.1016/j.heliyon.2018.e00591. eCollection 2018 Apr.
Factor H binding protein (FHbp) is a component of two licensed vaccines for prevention of sepsis and meningitis caused by serogroup B meningococci. FHbp binds human Factor H (FH), which contributes to evasion of host immunity and FHbp sequence variants can be classified into two sub-families. Antibodies against FHbp elicit complement-mediated killing and can inhibit recruitment of FH to the bacterial surface. We report epitope mapping studies of two murine IgG mAbs, designated JAR 31 and JAR 36, isolated from a mouse immunized with FHbp in sub-family A, which is present in ∼30-40% of invasive isolates. In the present study, we tested the reactivity of mAbs JAR 31 and JAR 36 with seven natural FHbp sequence variants from different phylogenic groups. We screened bacteriophage-displayed peptide libraries to identify amino acid residues contributing to the JAR 36 epitope. Based on the reactivities of mAbs JAR 31 and JAR 36 with the seven FHbp variants, and the frequent occurrences of aspartate (D) and lysine (K) residues in the JAR 36-bound phage peptides, we selected six residues in the carboxyl-terminal region of FHbp for replacement with alanine (A). The D201A and K203A substitutions respectively eliminated and decreased binding of mAbs JAR 31 and JAR 36 to FHbp. These substitutions did not affect binding of the control mAb JAR 33 or of human FH. JAR 31 or JAR 36 mediated cooperative complement-mediated bactericidal activity with other anti-FHbp mAbs. The identification of two amino acid residues involved in the epitopes recognized by these anti-FHbp mAbs may contribute to a more complete understanding of the spatial requirements for cooperative anti-FHbp mAb bactericidal activity.
因子H结合蛋白（FHbp）是两种已获许可的疫苗的成分，用于预防由B群脑膜炎奈瑟菌引起的败血症和脑膜炎。FHbp与人因子H（FH）结合，这有助于逃避宿主免疫，并且FHbp序列变体可分为两个亚家族。针对FHbp的抗体引发补体介导的杀伤作用，并可抑制FH向细菌表面的募集。我们报告了两种鼠源IgG单克隆抗体（分别命名为JAR 31和JAR 36）的表位作图研究，这两种抗体是从用A亚家族的FHbp免疫的小鼠中分离得到的，A亚家族存在于约30%-40%的侵袭性分离株中。在本研究中，我们测试了单克隆抗体JAR 31和JAR 36与来自不同系统发育组的七个天然FHbp序列变体的反应性。我们筛选了噬菌体展示肽库，以鉴定构成JAR 36表位的氨基酸残基。基于单克隆抗体JAR 31和JAR 36与七个FHbp变体的反应性，以及在与JAR 36结合的噬菌体肽中频繁出现的天冬氨酸（D）和赖氨酸（K）残基，我们选择了FHbp羧基末端区域的六个残基用丙氨酸（A）进行替换。D201A和K203A替换分别消除和降低了单克隆抗体JAR 31和JAR 36与FHbp的结合。这些替换不影响对照单克隆抗体JAR 33或人FH的结合。JAR 31或JAR 36与其他抗FHbp单克隆抗体介导协同补体介导的杀菌活性。鉴定这些抗FHbp单克隆抗体识别的表位中涉及的两个氨基酸残基，可能有助于更全面地了解抗FHbp单克隆抗体协同杀菌活性的空间要求。
