Department of Gastroenterology, Hepatology, Pneumology and Infectious Diseases, Katharinenhospital, Klinikum Stuttgart, Stuttgart, Germany.
Department I of Internal Medicine, Division of Infectious Diseases, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany.
Infection. 2023 Feb;51(1):83-90. doi: 10.1007/s15010-022-01830-x. Epub 2022 Jun 1.
Antibody assays against SARS-CoV-2 are used in sero-epidemiological studies to estimate the proportion of a population with past infection. IgG antibodies against the spike protein (S-IgG) allow no distinction between infection and vaccination. We evaluated the role of anti-nucleocapsid-IgG (N-IgG) to identify individuals with infection more than one year past infection.
S- and N-IgG were determined using the Euroimmun enzyme-linked immunosorbent assay (ELISA) in two groups: a randomly selected sample from the population of Stuttgart, Germany, and individuals with PCR-proven SARS-CoV-2 infection. Participants were five years or older. Demographics and comorbidities were registered from participants above 17 years.
Between June 15, 2021 and July 14, 2021, 454 individuals from the random sample participated, as well as 217 individuals with past SARS-CoV-2 infection. Mean time from positive PCR test result to antibody testing was 458.7 days (standard deviation 14.6 days) in the past infection group. In unvaccinated individuals, the seroconversion rate for S-IgG was 25.5% in the random sample and 75% in the past infection group (P = < 0.001). In vaccinated individuals, the mean signal ratios for S-IgG were higher in individuals with prior infection (6.9 vs 11.2; P = < 0.001). N-IgG were only detectable in 17.1% of participants with past infection. Predictors for detectable N-IgG were older age, male sex, fever, wheezing and in-hospital treatment for COVID-19 and cardiovascular comorbidities.
N-IgG is not a reliable marker for SARS-CoV-2 infection after more than one year. In future, other diagnostic tests are needed to identify individuals with past natural infection.
针对 SARS-CoV-2 的抗体检测用于血清流行病学研究，以估计人群中既往感染的比例。针对刺突蛋白（S-IgG）的 IgG 抗体无法区分感染和接种疫苗。我们评估了抗核衣壳 IgG（N-IgG）的作用，以确定感染超过一年的个体。
使用 Euroimmun 酶联免疫吸附试验（ELISA）在两组中测定 S 和 N-IgG：德国斯图加特人群的随机样本和经 PCR 证实的 SARS-CoV-2 感染个体。参与者年龄在 5 岁以上。17 岁以上的参与者记录了人口统计学和合并症。
2021 年 6 月 15 日至 7 月 14 日，随机样本中有 454 人参加，过去有 SARS-CoV-2 感染的有 217 人。过去感染组中从阳性 PCR 检测结果到抗体检测的平均时间为 458.7 天（标准差 14.6 天）。在未接种疫苗的个体中，随机样本中 S-IgG 的血清转化率为 25.5%，而在过去感染组中为 75%（P<0.001）。在接种疫苗的个体中，先前感染个体的 S-IgG 平均信号比值更高（6.9 比 11.2；P<0.001）。N-IgG 仅在 17.1%的既往感染者中可检测到。可检测到 N-IgG 的预测因素是年龄较大、男性、发热、喘息和因 COVID-19 住院治疗以及心血管合并症。
一年多后，N-IgG 不是 SARS-CoV-2 感染的可靠标志物。在未来，需要其他诊断测试来识别过去自然感染的个体。
