COVID-19 packs a stronger punch than the common cold, so antibodies capable of fending off this new coronavirus may have a shot at lingering longer. Broadly speaking, the more severe the disease, the more resources the body will dedicate to memorizing that pathogen’s features, and the stronger and longer lasting the immune response will be, says Allison Roder, a virologist at New York University. Previous studies have shown that people who survived SARS, another coronavirus disease that resulted in a 2003 epidemic, still have antibodies against the pathogen in their blood years after recovery. But this trend is not a sure thing, and scientists don’t know yet whether SARS-CoV-2 will fall in line.
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Sinai Immunol Review Project • a month ago

Main findings
The authors characterized the immune response in peripheral blood of a 47-year old COVID-19 patient.
SARS-CoV2 was detected in nasopharyngeal swab, sputum and faeces samples, but not in urine, rectal swab, whole blood or throat swab. 7 days after symptom onset, the nasopharyngeal swab test turned negative, at day 10 the radiography infiltrates were cleared and at day 13 the patient became asymptomatic.

Immunofluorescence staining shows from day 7 the presence of COVID-19-binding IgG and IgM antibodies in plasma, that increase until day 20.
Flow cytometry on whole blood reveals a plasmablast peak at day 8, a gradual increase in T follicular helper cells, stable HLA-DR+ NK frequencies and decreased monocyte frequencies compared to healthy counterparts. The expression of CD38 and HLA-DR peaked on T cells at D9 and was associated with higher production of cytotoxic mediators by CD8+ T cells.
IL-6 and IL-8 were undetectable in plasma.
The authors further highlight the presence of the IFITM3 SNP-rs12252-C/C variant in this patient, which is associated with higher susceptibility to influenza virus.

Limitations of the study
These results need to be confirmed in additional patients.
COVID-19 patients have increased infiltration of macrophages in their lungs{1}. Monitoring monocyte proportions in blood earlier in the disease might help to evaluate their eventual migration to the lungs.
The stable concentration of HLA-DR+ NK cells in blood from day 7 is not sufficient to rule out NK cell activation upon SARS-CoV2 infection. In response to influenza A virus, NK cells express higher levels of activation markers CD69 and CD38, proliferate better and display higher cytotoxicity{2}. Assessing these parameters in COVID-19 patients is required to better understand NK cell role in clearing this infection.
Neutralization potential of the COVID-19-binding IgG and IgM antibodies should be assessed in future studies.
This patient was able to clear the virus, while presenting a SNP associated with severe outcome following influenza infection. The association between this SNP and outcome
upon SARS-CoV2 infection should be further investigated.

Relevance
This study is among the first to describe the appearance of COVID-19-binding IgG and IgM antibodies upon infection. The emergence of new serological assays might contribute to monitor more precisely the seroconversion kinetics of COVID-19 patients{3}. Further association studies between IFITM3 SNP-rs12252-C/C variant and clinical data might help to refine the COVID-19 outcome prediction tools.

References
1. Liao, M. et al. The landscape of lung bronchoalveolar immune cells in COVID-19 revealed by single-cell RNA sequencing. http://medrxiv.org/lookup/d... (2020) doi:10.1101/2020.02.23.20026690.
2. Scharenberg, M. et al. Influenza A Virus Infection Induces Hyperresponsiveness in Human Lung Tissue-Resident and Peripheral Blood NK Cells. Front. Immunol. 10, 1116 (2019).
3. Amanat, F. et al. A serological assay to detect SARS-CoV-2 seroconversion in humans. http://medrxiv.org/lookup/d... (2020) doi:10.1101/2020.03.17.20037713.

Review by Bérengère Salomé as part of a project by students, postdocs and faculty at the Immunology Institute of the Icahn school of medicine, Mount Sinai