Corrigendum: Case report: Persistence of residual antigen and RNA of the SARS-CoV-2 virus in tissues of two patients with long COVID.

[This corrects the article DOI: 10.3389/fimmu.2022.939989.].

Case report: Persistence of residual antigen and RNA of the SARS-CoV-2 virus in tissues of two patients with long COVID.

The World Health Organization has defined long COVID-19 (LC) as a condition that occurs in individuals with a history of SARS-CoV-2 infection who exhibit persistent symptoms after its acute phase that last for at least two months and cannot be explained by an alternative diagnosis. Since we had previously reported residual viral antigens in tissues of convalescent patients, we aimed to assess the presence of such antigens in long COVID tissues. Here, we established the presence of the residual virus in the appendix, skin, and breast tissues of 2 patients who exhibited LC symptoms 163 and 426 days after symptom onset. With multiplex immunohistochemistry, we detected viral nucleocapsid protein in all three tissues. The nucleocapsid protein was further observed to colocalize with macrophage marker CD68, suggesting that immune cells were direct targets of SARS-CoV-2. Additionally, using RNAscope, the presence of viral RNA was also detected. Our positive finding in the breast tissue is corroborated by the recent reports of immunocompromised patients experiencing LC symptoms and persistent viral replication. Overall, our findings and emerging LC studies raise the possibility that the gastrointestinal tract may function as a reservoir for SARS-CoV-2.

Persistence of residual SARS-CoV-2 viral antigen and RNA in tissues of patients with long COVID-19 (preprint)

The World Health Organization has defined long COVID-19 (LC) as a condition where patients exhibit persistent symptoms over time after its acute phase, which cannot be explained by alternative diagnosis. Since we have previously reported residual viral antigens in tissues of convalescent patients, we now aim to assess the presence of such antigens in post-convalescent tissues. Here, we established the presence of residual virus within the appendix and breast tissue of 2 patients who exhibited LC symptoms, 175 to 462 days upon positive diagnosis, using immunohistological techniques. We observed positive staining for viral nucleocapsid protein (NP) in the appendix, and tumour-adjacent region of the breast, but not within the tumour via multiplex immunohistochemistry. Notably, with RNAscope, both positive-sense and negative-sense (replicative intermediate) viral RNA were detected. As a single-stranded virus, SARS-CoV-2, have to produce a replicative intermediate as a template to synthesize new genomic RNAs. Thus, the detection of negative-sense viral RNA suggests ongoing viral replication. While viral RNA and antigen from gastrointestinal and stool samples of convalescent patients has been extensively reported, we believe this is the first study to detect viable virus. Furthermore, our positive finding in the breast tissue also corroborated with recent reports that immunocompromised patients had also experienced LC symptoms and persistent viral replication. Overall, our findings, along with emerging LC studies, raises the possibility of the gastrointestinal tract functioning as a reservoir.

Analysis of cell-mediated immunity in people with long COVID (preprint)

ABSTRACT Introduction The objective of this study is to analyse the specific immune response against SARS-CoV-2 in those affected by Long Covid (LC), attributable to T cells (cell-mediated immunity) and to carry out a parallel analysis of the humoral response and lymphocyte typing. Methodology Descriptive cross-sectional study of 74 patients with LC for at least 4 months since diagnosis. The collected data were: information on the COVID-19 episode and the persistent symptoms, medical history and a specific cell-mediated immunity to SARS-CoV-2 through flow cytometry, assessing the release of interferon-gamma (IFN-Ɣ) by T4 lymphocytes, T8 lymphocytes and NK cells. Descriptive and comparative analyses were carried out. Results Patients with LC had negative serology for Covid-19 in 89% of cases but 96% showed specific cellular immunity to SARS-CoV-2 an average of 9.5 months after infection: 89% of this response corresponded to T8 lymphocytes, 58% to NK cells, and 51% to T4 lymphocyte (20% negligibly positive). Most of them had altered immune cell typing and we found that T4 lymphocyte counts were low in 34% of cases and NK cell high in 64%. Macrophage populations were detected in the peripheral blood of 7% of them. Patients displayed a higher percentage of illnesses related to &[Prime]abnormal&[Prime] immune responses, either preceding SARS-CoV-2 infection (43%) or following it in 23% of cases. Conclusion The immune system appears to have an important involvement in the development of LC and viral persistence could be the cause or consequence of it. Further analysis with a control group should be performed.