Cell Biology of Viral Infection Lab, Instituto Gulbenkian de Ciência, Oeiras, Portugal.
Pediatric Infectious Disease Unit, Hospital Dona Estefânia, Centro Hospitalar Universitário Lisboa Central, Lisboa, Portugal.
PLoS One. 2022 Jun 15;17(6):e0268388. doi: 10.1371/journal.pone.0268388. eCollection 2022.
Adults are being vaccinated against SARS-CoV-2 worldwide, but the longitudinal protection of these vaccines is uncertain, given the ongoing appearance of SARS-CoV-2 variants. Children remain largely unvaccinated and are susceptible to infection, with studies reporting that they actively transmit the virus even when asymptomatic, thus affecting the community.
We investigated if saliva is an effective sample for detecting SARS-CoV-2 RNA and antibodies in children, and associated viral RNA levels to infectivity. For that, we used a saliva-based SARS-CoV-2 RT-qPCR test, preceded or not by RNA extraction, in 85 children aged 10 years and under, admitted to the hospital regardless of COVID-19 symptomatology. Amongst these, 29 (63.0%) presented at least one COVID-19 symptom, 46 (54.1%) were positive for SARS-CoV-2 infection, 28 (32.9%) were under the age of 1, and the mean (SD) age was 3.8 (3.4) years. Saliva samples were collected up to 48 h after a nasopharyngeal swab-RT-qPCR test.
In children aged 10 years and under, the sensitivity, specificity, and accuracy of saliva-RT-qPCR tests compared to NP swab-RT-qPCR were, respectively, 84.8% (71.8%-92.4%), 100% (91.0%-100%), and 91.8% (84.0%-96.6%) with RNA extraction, and 81.8% (68.0%-90.5%), 100% (91.0%-100%), and 90.4% (82.1%-95.0%) without RNA extraction. Rescue of infectious particles from saliva was limited to CT values below 26. In addition, we found significant IgM positive responses to SARS-CoV-2 in children positive for SARS-CoV-2 by NP swab and negative by saliva compared to other groups, indicating late infection onset (>7-10 days).
Saliva is a suitable sample type for diagnosing children aged 10 years and under, including infants aged <1 year, even bypassing RNA extraction methods. Importantly, the detected viral RNA levels were significantly above the infectivity threshold in several samples. Further investigation is required to correlate SARS-CoV-2 RNA levels to viral transmission.
全球范围内，成年人正在接种针对 SARS-CoV-2 的疫苗，但鉴于 SARS-CoV-2 变体的持续出现，这些疫苗的长期保护效果尚不确定。儿童仍未大量接种疫苗，容易感染，有研究报告称，即使无症状，他们也会积极传播病毒，从而影响社区。
我们研究了唾液是否可作为检测儿童体内 SARS-CoV-2 RNA 和抗体的有效样本，并将病毒 RNA 水平与感染性相关联。为此，我们使用了一种基于唾液的 SARS-CoV-2 RT-qPCR 检测方法，在 85 名 10 岁及以下的儿童中进行了检测，这些儿童无论 COVID-19 症状如何，均入院治疗。其中，29 名（63.0%）至少出现了一种 COVID-19 症状，46 名（54.1%） SARS-CoV-2 感染检测呈阳性，28 名（32.9%）年龄在 1 岁以下，平均（SD）年龄为 3.8（3.4）岁。唾液样本是在鼻咽拭子-RT-qPCR 检测后 48 小时内采集的。
在 10 岁及以下儿童中，与 NP 拭子-RT-qPCR 相比，经 RNA 提取后唾液-RT-qPCR 检测的灵敏度、特异性和准确性分别为 84.8%（71.8%-92.4%）、100%（91.0%-100%）和 91.8%（84.0%-96.6%），未经 RNA 提取则分别为 81.8%（68.0%-90.5%）、100%（91.0%-100%）和 90.4%（82.1%-95.0%）。从唾液中回收有感染性的病毒颗粒仅限于 CT 值低于 26 的样本。此外，我们发现与其他组相比，在通过 NP 拭子检测 SARS-CoV-2 呈阳性而通过唾液检测呈阴性的儿童中，针对 SARS-CoV-2 的 IgM 阳性反应显著增加，表明感染发病较晚（>7-10 天）。
唾液是诊断 10 岁及以下儿童（包括<1 岁的婴儿）的合适样本类型，甚至可绕过 RNA 提取方法。重要的是，在多个样本中，检测到的病毒 RNA 水平明显高于感染性阈值。需要进一步研究以将 SARS-CoV-2 RNA 水平与病毒传播相关联。
