Laboratório de Bacteriologia, Instituto Butantan, São Paulo, Brazil.
Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
PLoS One. 2021 Feb 12;16(2):e0247056. doi: 10.1371/journal.pone.0247056. eCollection 2021.
Older adults are at increased risk of pneumococcal disease. This work aims to evaluate whether there is any decrease in serum IgG against variants of the antigens Pneumococcal surface protein A (PspA) and Pneumococcal surface protein C (PspC) in healthy adults with increasing age. Levels of IgG against PspA and PspC variants were determined by ELISA in serum samples comparing volunteers 18-30 years of age with volunteers who were 50-70+ before and after an experimental pneumococcal colonization challenge. The serotype 6B strain used in the challenge belongs to a minor group of pneumococcal isolates expressing two PspC variants. There was a decrease in levels of IgG with increasing age for the most common PspA variants and for all PspC variants analyzed. No correlation was found between basal levels of IgG against these antigens and protection against colonization. There was an increase in levels of IgG against PspA variants that are more cross-reactive with the variant expressed by the challenge strain post challenge in younger individuals who became colonized. Since the challenge strain used in our study expresses two different PspC variants, an increase in serum IgG against all PspC variants tested was observed in younger individuals who became colonized. For some of the antigen variants tested, a decrease in serum IgG was observed in young volunteers who were challenged but did not become colonized. Serum IgG antibodies against PspA and PspC variants thus decrease with age in healthy adults, but there is no correlation between levels of IgG against these antigens and protection against human experimental colonization. Though no correlation between naturally induced serum IgG antibodies against PspA and PspC and protection against colonization was observed, these results do not rule out the protective potential of these antigens as vaccines against pneumococcal infections.
老年人患肺炎球菌病的风险增加。本研究旨在评估健康成年人血清中针对肺炎球菌表面蛋白 A（PspA）和肺炎球菌表面蛋白 C（PspC）抗原变体的 IgG 是否随年龄增长而减少。通过 ELISA 比较了 18-30 岁志愿者和 50-70 岁志愿者在实验性肺炎球菌定植挑战前后的血清样本，以确定针对 PspA 和 PspC 变体的 IgG 水平。用于挑战的 6B 血清型菌株属于少数表达两种 PspC 变体的肺炎球菌分离株。对于最常见的 PspA 变体和所有分析的 PspC 变体，随着年龄的增长，IgG 水平呈下降趋势。针对这些抗原的基础 IgG 水平与定植保护之间没有相关性。在被定植的年轻个体中，针对与挑战株表达的变体更具交叉反应性的 PspA 变体的 IgG 水平在挑战后增加。由于我们研究中使用的挑战菌株表达两种不同的 PspC 变体，因此在被定植的年轻个体中，针对所有测试的 PspC 变体的血清 IgG 水平增加。在一些测试的抗原变体中，在被挑战但未定植的年轻志愿者中观察到血清 IgG 下降。因此，在健康成年人中，血清 IgG 抗体针对 PspA 和 PspC 变体随年龄增长而下降，但针对这些抗原的 IgG 水平与人类实验定植保护之间没有相关性。虽然没有观察到针对 PspA 和 PspC 的天然诱导血清 IgG 抗体与定植保护之间存在相关性，但这些结果并不能排除这些抗原作为肺炎球菌感染疫苗的保护潜力。
