May Rena J, Beenhouwer David O, Scharff Matthew D
Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
J Immunol. 2003 Nov 1;171(9):4905-12. doi: 10.4049/jimmunol.171.9.4905.
Cryptococcus neoformans causes a life-threatening meningoencephalitis in AIDS patients. Mice immunized with a glycoconjugate vaccine composed of the glucuronoxylomannan (GXM) component of the cryptococcal capsular polysaccharide conjugated to tetanus toxoid produce Abs that can be either protective or nonprotective. Because nonprotective Abs block the efficacy of protective Abs, an effective vaccine must focus the Ab response on a protective epitope. Mice immunized with peptide mimetics of GXM conjugated to keyhole limpet hemocyanin (KLH) with glutaraldehyde developed Abs to GXM. However, control peptides P315 and P24 conjugated to KLH also elicited Abs to GXM. GXM-binding Abs from mice immunized with P315-KLH were inhibited by KLH treated with glutaraldehyde (KLH-g), but not by P315. Furthermore, KLH-g inhibited binding of GXM by serum of mice immunized with GXM-TT, indicating that glutaraldehyde treatment of KLH reveals an epitope(s) that cross-reacts with GXM. Vaccination with KLH-g or unmodified KLH elicited Abs to GXM, but did not confer protection against C. neoformans, suggesting the cross-reactive epitope on KLH was not protective. This was supported by the finding that 4H3, a nonprotective mAb, cross-reacted strongly with KLH-g. Sera from mice immunized with either native KLH or KLH-g cross-reacted with several other carbohydrate Ags, many of which have been conjugated to KLH for vaccine development. This study illustrates how mAbs can be used to determine the efficacy of potential vaccines, in addition to describing the complexity of using KLH and glutaraldehyde in the development of vaccines to carbohydrate Ags.
新型隐球菌可在艾滋病患者中引发危及生命的脑膜脑炎。用由隐球菌荚膜多糖的葡糖醛酸木甘露聚糖（GXM）成分与破伤风类毒素偶联而成的糖缀合物疫苗免疫的小鼠会产生可具有保护作用或无保护作用的抗体。由于无保护作用的抗体可阻断有保护作用的抗体的功效，因此有效的疫苗必须使抗体反应集中于一个保护性表位。用戊二醛将与钥孔血蓝蛋白（KLH）偶联的GXM肽模拟物免疫的小鼠产生了针对GXM的抗体。然而，与KLH偶联的对照肽P315和P24也引发了针对GXM的抗体。用P315-KLH免疫的小鼠产生的GXM结合抗体被戊二醛处理的KLH（KLH-g）抑制，但未被P315抑制。此外，KLH-g抑制了用GXM-TT免疫的小鼠血清与GXM的结合，这表明对KLH进行戊二醛处理可暴露出与GXM发生交叉反应的表位。用KLH-g或未修饰的KLH进行疫苗接种可引发针对GXM的抗体，但不能提供针对新型隐球菌的保护作用，这表明KLH上的交叉反应性表位没有保护作用。这一发现得到了支持，即一种无保护作用的单克隆抗体4H3与KLH-g发生了强烈的交叉反应。用天然KLH或KLH-g免疫的小鼠血清与其他几种碳水化合物抗原发生交叉反应，其中许多已与KLH偶联用于疫苗开发。这项研究不仅说明了单克隆抗体如何可用于确定潜在疫苗的功效，还描述了在开发针对碳水化合物抗原的疫苗中使用KLH和戊二醛的复杂性。
