key: cord-0917428-13fk2ko4
authors: He, Gang; Chuai, Xia; Liang, Dan; Chen, Chunyu; Hu, Changzheng; Ke, Changwen; Ke, Bixia; Zhen, Peilin; Zhang, Huajun
title: Case report: Long-term asymptomatic SARS-CoV-2 infection associated with deficiency on multiple immune cells
date: 2022-04-12
journal: Biosaf Health
DOI: 10.1016/j.bsheal.2022.04.001
sha: 294776fa09977912adc13d67afc709dc23c14a85
doc_id: 917428
cord_uid: 13fk2ko4

The immune responses and the function of immune cells among asymptomatic SARS-CoV-2 infection cases, especially in immuno-compromised individuals, remain largely unknown. Here we present a case of asymptomatic SARS-CoV-2 infection that lasted for at least 67 days. The patient has administrated Thymalfasin as 1.6 mg per dose every other day from Day 45 to 70, plus 200 mg per dose Arbidol antiviral therapy three doses per day from Day 48 to 57. Throughout the infection, no anti-SARS-CoV-2 specific IgM or IgG antibodies were detected. Instead, the patient showed either a low percentage or an absolute number of non-classical monocytes, dendritic cells (DCs), CD4(+) T cells, and regulatory T cells (Tregs), which may account for the clinical feature and absence of antibody response. This case may shed new light on the outbreak management related to control/prevention, treatment, and vaccination of SARS-CoV-2 and other virus infections in immunocompromised individuals.

The coronavirus disease 2019 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and the clinical manifestations were widely varied, ranging from asymptomatic to mild, moderate, and severe pneumonia, which frequently leads to death [1] . The variability of disease severity was closely related to the individual immune responses to SARS-CoV-2 after the first infection [2] . For example, Wong et al. reported that total lymphocytes, CD4 + T cells, CD8 + T cells, B cells, and natural killer (NK) cells decreased in COVID-19 patients, and severe cases had a lower level than mild cases [3] . And Zhou et al. found that acute SARS-CoV-2 infection resulted in broad immune cell reduction, including T, natural killer, monocyte, and DCs [4] . But most SARS-CoV-2 infected people, including asymptomatic individuals, developed virus-specific antibodies for up to months [5, 6] .

Immuno-compromised patients are prone to progress into severe or critical types underpinned by impaired immune function. However, in this case study, we present an asymptomatic COVID-19 patient who was initially diagnosed positive in Nigeria but negative in the following three tests before traveling to Guangzhou, China, where she was tested positive again. The patient was administrated Thymalfasin plus Arbidol antiviral therapy. The patient had been positive with real-time RT-PCR for 67 days, but no SARS-CoV-2 specific IgM or IgG antibodies were detected in the sera.

The blood samples were subjected to flow cytometry and found that the patient had dysfunctions in immune response with a low percentage or an absolute number of nonclassical monocytes, DCs, CD4 + T cells, and Tregs.

A 33-year-old female overseas worker was diagnosed as SARS-CoV-2 nucleic acid positive during quarantine when entering Guangzhou, China. The patient was initially diagnosed with RNA but without any symptoms in early January of 2021 (Day -17) in Nigeria, where she had worked since 2019. But the tests performed on Day -13, -12, and -8 showed negative, and she took an airplane on Day -6 back to Guangzhou. But DCs were reversed for both days, increasing from 0.15% to 0.27%, though the total number was significantly low. Among DCs, myeloid DCs (mDCs) showed a similar trend as DCs; however, type 1 and type 2 mDCs were relatively high in percentage. A low rate was also found for CD4 + T cells but didn't vary much on both days. Like nonclassical monocytes, Tregs were deficient and significantly decreased from Day 77 to Day 98, while Naïve Tregs had some increase but were still low on both days. CD8 + T cells and NK cells were normal in percentages and absolute numbers. The patient had slightly low B cells on Day 77 in total number, but not in rate. Table 1 . Summary of flow cytometry analysis of immune cells in the whole blood. * ↑ and ↓ indicate increase and decrease compared to the reference value, respectively.

In severe and critical cases, acute SARS-CoV-2 infection could reduce broad immune cells, including CD4+ T cells, CD8+ T cells, NK cells, and DCs in severe and critical cases [3, 4] . Benjamin et al. found high proportions of SARS-CoV-2-reactive cytotoxic CD4 + T cells and a reduced proportion of SARS-CoV-2-reactive Tregs in hospitalized patients [7] . But SARS-CoV-2 infection led to diverse effects on monocytes, with reduction of non-classical monocytes and accumulation of classical monocytes in severe patients [8] ; Gatti et al. also reported an increase of non-classical and intermediate monocytes in patients with moderate symptoms [9] . In addition, nonclassical monocytes increased in patients with infectious diseases, and in vitro cultured non-classical monocytes exhibit phenotypic and functional dendritic cell-like characteristics [10, 11] , indicating they play essential roles in the immune response against pathogens. Long et al. reported that 81% and 62% of asymptomatic patients tested positive for IgG and IgM, respectively, 3-4 weeks after exposure [6] . Although the low percentage or an absolute number of multiple immune cells of the case might result from SARS-CoV-2 infection, the absence of SARS-CoV-2 specific antibody indicated that the patient might have dysfunctions of the immune system response. Supporting, the patient complained of frequent cough and cold, and no IgG antibody was detected against YFV when the patient was vaccinated before she went to Nigeria in 2019 (data not shown). 

This study has been approved by Ethic Committee of the Jiangmen Hospital (approval serial number 2020139). The patient has signed informed consent to participate in this study.

The study was funded by Natural Science Foundation of Hebei Province granted to XC (no. H2020206352) and Novel Coronavirus Project to GH by Jiangmen Science and Technology Bureau (2020020500410003915) and Guangzhou Emergency Response Plan to D.L (EKPG21-27). The funders had no role in the study's design or the decision to publish this work. Table 1 . Summary of flow cytometry analysis of immune cells in the whole blood.

The immune responses and the function of immune cells among asymptomatic SARS-CoV-2 infection cases, especially in immuno-compromised individuals remain largely unknown. Here we report a case of asymptomatic, persistent SARS-CoV-2 infection with no antibody production which may be due to the deficiency of multiple immune cells. 

Clinical features of patients infected with 2019 novel coronavirus in

COVID-19: Unanswered questions on immune response and pathogenesis

Characteristics of Peripheral Lymphocyte Subset Alteration in COVID-19 Pneumonia

Acute SARS-CoV-2 Infection Impairs Dendritic Cell and T Cell Responses

Antibody dynamics to SARS-CoV-2 in asymptomatic COVID-19 infections

Clinical and immunological assessment of asymptomatic SARS-CoV-2 infections

Imbalance of Regulatory and Cytotoxic SARS-CoV-2-Reactive CD4(+) T Cells in COVID-19

Elevated Calprotectin and Abnormal Myeloid Cell Subsets Discriminate Severe from Mild COVID-19

Intermediate Monocyte Subsets in Severe Acute SARS-CoV-2 Infection

The authors declare that there are no conflicts of interest. 

blood monocytes exhibit phenotypic and functional dendritic cell-like characteristics, Eur J Immunol 30 (7) (