SARS-CoV-2量と血清抗体の経時的プロファイル

母数が少ないコホート研究なので、断言できませんが、やはり高齢者の方がウイルス排泄が多く、若い人の方がウイルス排泄が少ないようです。

もっと大きな母数で、15歳以下でクラスターができにくいことが証明されたら、今後、小中学校の閉鎖は最小限で済むようになるのかも知れません。

（※　管理者注　2020/04/28記載）

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重症急性呼吸器症候群コロナウイルス2（SARS-CoV-2）に感染した患者からの一連の呼吸器ウイルス量と血清抗体反応の包括的なデータはまだ入手できません。

鼻咽頭と咽頭スワブは通常、呼吸器感染症のウイルス量を連続的に監視するために取得されますが、これらの標本を収集すると、患者に不快感を与え、医療従事者を危険にさらす可能性があります。

COVID-19の患者からの口腔咽頭後部（喉の深部）唾液サンプルにおけるSARS-CoV-2のウイルス量、および血清抗体反応を経時的に確認することを目的とした。

＜方法＞

香港の2つの病院でコホート研究を行いました。

実験室で確認されたCOVID-19の患者を含めました。

血液、尿、中咽頭後部唾液、直腸スワブのサンプルを入手しました。

一連のウイルス量は、逆転写酵素定量的PCR（RT-qPCR）によって確認されました。

SARS-CoV-2内部核タンパク質（NP）および表面スパイクタンパク質受容体結合ドメイン（RBD）に対する抗体レベルを、EIAを使用して測定しました。

全ゲノム配列決定は、感染中に発生する可能性のある変異を特定するために行われました。

＜調査結果＞

2020年1月22日から2020年2月12日までの間に、30人の患者が対象としてスクリーニングされ、そのうち23人が含まれていた（中央値：62歳[範囲37-75歳]）。

プレゼンテーション時の後部中咽頭唾液または他の呼吸器検体におけるウイルス量の中央値は、1mLあたり5.2log10コピーでした（IQR 4.1-7.0）。

唾液ウイルス量は症状発現後の最初の1週間で最も高く、その後時間とともに減少しました（勾配-0.15、95％CI -0.19から-0.11; R2 = 0.71）。

1人の患者では、症状の発症から25日後にウイルスRNAが検出されました。

より年齢の高さはウイルス量の多さと相関していた（スピアマンのρ= 0.48、95％CI 0.074-0.75; p= 0.020）。

症状発現から14日以上経過した血清サンプルを使用する16人の患者の血清陽性率は、抗NP IgG（n = 15）で94％、抗NP IgM（n = 14）で88％、抗NP-IgGで100％、RBD IgG（n = 16）、および抗RBD IgMで94％（n = 15）でした。

抗SARS-CoV-2-NPまたは抗SARS-CoV-2-RBD IgGレベルはウイルス中和力価と相関していた（R2>0.9）。

連続サンプルでゲノム変異は検出されませんでした。

＜解釈＞

中咽頭後部唾液サンプルは、患者や医療従事者にとってより受け入れやすい非侵襲的な標本です。

重症急性呼吸器症候群とは異なり、COVID-19の患者は、症状のピーク直前でウイルス量が最も高く、これがこの流行の急速な拡大の原因である可能性があります。

この発見は、リスクの高い個人に対して、厳格な感染管理と強力な抗ウイルス薬の単独または組み合わせの早期使用の重要性を強調しています。

血清学的アッセイは、診断のためにRT-qPCRを補完することができます。

Temporal Profiles of Viral Load in Posterior Oropharyngeal Saliva Samples and Serum Antibody Responses During Infection by SARS-CoV-2: An Observational Cohort Study

Lancet Infect Dis.

2020 Mar 23;S1473-3099(20)30196-1. doi: 10.1016/S1473-3099(20)30196-1. Online ahead of print.

Kelvin Kai-Wang To 1 , Owen Tak-Yin Tsang 2 , Wai-Shing Leung 2 , Anthony Raymond Tam 3 , Tak-Chiu Wu 4 , David Christopher Lung 5 , Cyril Chik-Yan Yip 6 , Jian-Piao Cai 6 , Jacky Man-Chun Chan 2 , Thomas Shiu-Hong Chik 2 , Daphne Pui-Ling Lau 2 , Chris Yau-Chung Choi 2 , Lin-Lei Chen 6 , Wan-Mui Chan 6 , Kwok-Hung Chan 6 , Jonathan Daniel Ip 6 , Anthony Chin-Ki Ng 6 , Rosana Wing-Shan Poon 6 , Cui-Ting Luo 6 , Vincent Chi-Chung Cheng 6 , Jasper Fuk-Woo Chan 1 , Ivan Fan-Ngai Hung 7 , Zhiwei Chen 6 , Honglin Chen 6 , Kwok-Yung Yuen 8

• PMID: 32213337 PMCID: PMC7158907 DOI: 10.1016/S1473-3099(20)30196-1

https://pubmed.ncbi.nlm.nih.gov/32213337/

Abstract

Background:

Coronavirus disease 2019 (COVID-19) causes severe community and nosocomial outbreaks. Comprehensive data for serial respiratory viral load and serum antibody responses from patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are not yet available. Nasopharyngeal and throat swabs are usually obtained for serial viral load monitoring of respiratory infections but gathering these specimens can cause discomfort for patients and put health-care workers at risk. We aimed to ascertain the serial respiratory viral load of SARS-CoV-2 in posterior oropharyngeal (deep throat) saliva samples from patients with COVID-19, and serum antibody responses.

Methods:

We did a cohort study at two hospitals in Hong Kong. We included patients with laboratory-confirmed COVID-19. We obtained samples of blood, urine, posterior oropharyngeal saliva, and rectal swabs. Serial viral load was ascertained by reverse transcriptase quantitative PCR (RT-qPCR). Antibody levels against the SARS-CoV-2 internal nucleoprotein (NP) and surface spike protein receptor binding domain (RBD) were measured using EIA. Whole-genome sequencing was done to identify possible mutations arising during infection.

Findings:

Between Jan 22, 2020, and Feb 12, 2020, 30 patients were screened for inclusion, of whom 23 were included (median age 62 years [range 37-75]). The median viral load in posterior oropharyngeal saliva or other respiratory specimens at presentation was 5·2 log10 copies per mL (IQR 4·1-7·0). Salivary viral load was highest during the first week after symptom onset and subsequently declined with time (slope -0·15, 95% CI -0·19 to -0·11; R2=0·71). In one patient, viral RNA was detected 25 days after symptom onset. Older age was correlated with higher viral load (Spearman's ρ=0·48, 95% CI 0·074-0·75; p=0·020). For 16 patients with serum samples available 14 days or longer after symptom onset, rates of seropositivity were 94% for anti-NP IgG (n=15), 88% for anti-NP IgM (n=14), 100% for anti-RBD IgG (n=16), and 94% for anti-RBD IgM (n=15). Anti-SARS-CoV-2-NP or anti-SARS-CoV-2-RBD IgG levels correlated with virus neutralisation titre (R2>0·9). No genome mutations were detected on serial samples.

Interpretation:

Posterior oropharyngeal saliva samples are a non-invasive specimen more acceptable to patients and health-care workers. Unlike severe acute respiratory syndrome, patients with COVID-19 had the highest viral load near presentation, which could account for the fast-spreading nature of this epidemic. This finding emphasises the importance of stringent infection control and early use of potent antiviral agents, alone or in combination, for high-risk individuals. Serological assay can complement RT-qPCR for diagnosis.

Funding:

Richard and Carol Yu, May Tam Mak Mei Yin, The Shaw Foundation Hong Kong, Michael Tong, Marina Lee, Government Consultancy Service, and Sanming Project of Medicine.

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