Todaro-Luck F, White E H, Reiss E, Cherniak R
Institute of Microbiology, University of Messina, Italy.
Mol Cell Probes. 1989 Dec;3(4):345-61. doi: 10.1016/0890-8508(89)90014-5.
Three monoclonal antibodies (MAbs) (BA4, BD1, CD6) reacted with Cryptococcus neoformans capsular glucuronoxylomannan (GXM) polysaccharide showing distinctive patterns against four serotypes as revealed by enzyme immunoassay (EIA), dot EIA, and immunofluorescence. Immunoelectron microscopy (IEM) was used to characterize binding sites for the MAbs on the C. neoformans capsule. All three MAbs bound to the capsule of serotype A strains 9104 and 9759. Differences in the intensity of binding to the two serotype A strains could not be explained by capsule diameter. The MAb BA-4 IgM bound well to 9759 (large capsule) and poorly to 9104 (small capsule), whereas MAb BD-1 (IgG-1) bound well to strain 9104 and poorly to strain 9759. Spurr's embedment inactivated the BA-4-binding epitopes in the C. neoformans 9759 capsule, but did not inactivate the ones that bound to BD-1. The epitopes recognized by BA-4 were different than the BD-1-binding determinants. The MAb CD-6 bound to a cytoplasmic precursor of capsular GXM. CD-6 (IgG) stained the capsule, cell wall, and cytoplasm of both C. neoformans tester strains. Competitive binding experiments were conducted. Single immunogold labelling showed that BD-1 inhibited the binding of BA-4, but not vice versa. The interaction between CD-6 and BA-4 resulted in a reciprocal inhibition. Double-labelling experiments showed reciprocal inhibition between BA-4 and each of the IgG MAbs. These MAbs are directed against capsular polysaccharide or its intracellular precursor. None of the MAbs stained C. neoformans cap 67, an acapsular mutant that does not contain GXM.
三种单克隆抗体（MAb）（BA4、BD1、CD6）与新型隐球菌荚膜葡糖醛酸木甘露聚糖（GXM）多糖发生反应，通过酶免疫测定（EIA）、斑点EIA和免疫荧光显示出针对四种血清型的独特模式。免疫电子显微镜（IEM）用于鉴定MAb在新型隐球菌荚膜上的结合位点。所有三种MAb均与A血清型菌株9104和9759的荚膜结合。与两种A血清型菌株结合强度的差异无法用荚膜直径来解释。MAb BA - 4 IgM与9759（大荚膜）结合良好，与9104（小荚膜）结合较差，而MAb BD - 1（IgG - 1）与菌株9104结合良好，与菌株9759结合较差。Spurr包埋使新型隐球菌9759荚膜中与BA - 4结合的表位失活，但未使与BD - 1结合的表位失活。BA - 4识别的表位与BD - 1结合决定簇不同。MAb CD - 6与荚膜GXM的细胞质前体结合。CD - 6（IgG）对两种新型隐球菌测试菌株的荚膜、细胞壁和细胞质进行染色。进行了竞争性结合实验。单免疫金标记显示BD - 1抑制BA - 4的结合，但反之则不然。CD - 6与BA - 4之间的相互作用导致相互抑制。双标记实验显示BA - 4与每种IgG MAb之间存在相互抑制。这些MAb针对荚膜多糖或其细胞内前体。没有一种MAb能对新型隐球菌cap 67（一种不含GXM的无荚膜突变体）进行染色。
