Kinetics of Immune Response in a Mild COVID-19 Patient


image_pdfimage_print
a, Timeline of COVID-19, showing detection of SARS-CoV-2 in sputum, nasopharyngeal aspirates and feces but not urine, rectal swab or whole blood. SARS-CoV-2 was quantified by rRT-PCR; cycle threshold (Ct) is shown. A higher Ct value means lower viral load. Dashed horizontal line indicates limit of detection (LOD) threshold (Ct = 45). Open circles, undetectable SARS-CoV-2. b, Anteroposterior chest radiographs on days 5 and 10 following symptom onset, showing radiological improvement from hospital admission to discharge. c, Immunofluorescence antibody staining, repeated twice in duplicate, for detection of IgG and IgM bound to SARS-CoV-2-infected Vero cells, assessed with plasma (diluted 1:20) obtained at days 7–9 and 20 following symptom onset. (Source: Thevarajan et al., 2020. Breadth of concomitant immune responses prior to patient recovery: a case report of non-severe COVID-19. Nature Medicine.)

a, Timeline of COVID-19, showing detection of SARS-CoV-2 in sputum, nasopharyngeal aspirates and feces but not urine, rectal swab or whole blood. SARS-CoV-2 was quantified by rRT-PCR; cycle threshold (Ct) is shown. A higher Ct value means lower viral load. Dashed horizontal line indicates limit
of detection (LOD) threshold (Ct = 45). Open circles, undetectable SARS-CoV-2. b, Anteroposterior chest radiographs on days 5 and 10 following symptom onset, showing radiological improvement
from hospital admission to discharge. c, Immunofluorescence antibody staining, repeated twice in duplicate, for detection of IgG and IgM bound to SARS-CoV-2-infected Vero cells, assessed with
plasma (diluted 1:20) obtained at days 7–9 and 20 following symptom onset. (Source: Thevarajan et al., 2020. Breadth of concomitant immune responses prior to patient recovery: a case report of non-severe COVID-19. Nature Medicine.)

As of 23 March 2020, SARS-CoV2 is responsible for almost 350,000 cases and over 15000 deaths globally. We report findings of an Australian COVID-19 Case study of a 47 year woman*.

Thevarajan et al., aimed to determine the “kinetics and breadth of immune responses associated with clinical resolution of COVID-19.” Specifically, the conducted immune-profiling of blood samples at day 7-9 post symptoms, and day 20 (recovered). They observed “Increased antibody-secreting cells (ASCs), follicular helper T cells (TFH cells) and SARS-CoV-2-specific IgM and IgG in blood before symptomatic recovery”. Mild-COVID-19 was also associated with peak CD4 and CD8 T cells (HLA-DR+CD38+) activation, which decreased by day 20. Further researchers showed that COVID-19 was associated with decreased levels of CD16+CD14+ monocytes compared to controls. Lower proportions of these cells could be related to immunopathology and recruitment of cells to the site of infection. Researchers detected lower levels of CD16+CD14+ monocytes in the COVID-19 patient compared to controls. This observation could be related to immunopathology and recruitment to the site of infection. Further, quantification of pro-inflammatory cytokines and chemokines provided no evidence of cytokine storm in this patient.

Findings reported by Thevarajan et al., demonstrate induction of robust multi-factorial immune responses, including adaptive immunity during early stages of SARS-CoV-2 infection. However, more studies are required to determine if similar immune-profiles are detected in other mild/moderate cases and if they are associated with better clinical outcomes. 

Thevarajan et al., 2020. Breadth of concomitant immune responses prior to patient recovery: a case report of non-severe COVID-19. Nature Medicine.

*History: Woman presented to emergency department (ED) 11 days after travelling from Wuhan, China to Australia. She exhibited symptoms: lethargy, sore throat, dry cough, pleuritic chest pain, mild dyspnea and subjective fevers which started 4 days before presenting to the ED. Upon detection of SAR-CoV2 in patients nasopharyngeal swabs, patient was admitted. SARS-Cov2 remained detected 5-6 days post symptoms, but was undetectable in urine, whole, nasopharyngeal  and rectal swabs from day 7 till discharge (Day 11 ). By Day 13 her symptoms had resolved and remained well at day 20.

Article by Cheleka Mpande

 
 
 
 
 
 
International Union of Immunological SocietiesUniversity of South AfricaInstitute of Infectious Disease and Molecular MedicineScience Education PrizesElizabeth Glazer Pediatric Aids Foundation