Major alterations to monocyte and dendritic cell subsets lasting more than 6 months after hospitalization for COVID-19.

Introduction: After more than two years the Coronavirus disease-19 (COVID-19) pandemic continues to burden healthcare systems and economies worldwide, and it is evident that the effects on the immune system can persist for months post-infection. The activity of myeloid cells such as monocytes and dendritic cells (DC) is essential for correct mobilization of the innate and adaptive responses to a pathogen. Impaired levels and responses of monocytes and DC to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is likely to be a driving force behind the immune dysregulation that characterizes severe COVID-19. Methods: Here, we followed a cohort of COVID-19 patients hospitalized during the early waves of the pandemic for 6-7 months. The levels and phenotypes of circulating monocyte and DC subsets were assessed to determine both the early and long-term effects of the SARS-CoV-2 infection. Results: We found increased monocyte levels that persisted for 6-7 months, mostly attributed to elevated levels of classical monocytes. Myeloid derived suppressor cells were also elevated over this period. While most DC subsets recovered from an initial decrease, we found elevated levels of cDC2/cDC3 at the 6-7 month timepoint. Analysis of functional markers on monocytes and DC revealed sustained reduction in program death ligand 1 (PD-L1) expression but increased CD86 expression across almost all cell types examined. Finally, C-reactive protein (CRP) correlated positively to the levels of intermediate monocytes and negatively to the recovery of DC subsets. Conclusion: By exploring the myeloid compartments, we show here that alterations in the immune landscape remain more than 6 months after severe COVID-19, which could be indicative of ongoing healing and/or persistence of viral antigens.

Corrigendum to "Presymptomatic viral shedding and infective ability of SARS-CoV-2; a case report" [Heliyon 7, (2), (February 2021), Article e06328].

[This corrects the article DOI: 10.1016/j.heliyon.2021.e06328.].

Evaluation of SARS-CoV-2 rapid antigen diagnostic tests for saliva samples.

Using saliva samples would facilitate sample collection, diagnostic feasibility, and mass screening of SARS-CoV-2. We tested two rapid antigen (RAD) immunochromatographic tests designed for detection of SARS-CoV-2 in saliva: Rapid Response™ COVID-19 Antigen Rapid Test Cassette for oral fluids and DIAGNOS™ COVID-19 Antigen Saliva Test. Evaluation of detection limit was performed with purified SARS-CoV-2 nucleocapsid protein and live SARS-CoV-2 virus. Sensitivity and specificity were further evaluated with reverse transcription quantitative PCR (RT-qPCR) positive and negative saliva samples from hospitalized individuals with COVID-19 (n = 39) and healthcare workers (n = 20). DIAGNOS showed higher sensitivity than Rapid Response for both nucleocapsid protein and live virus. The limit of detection of the saliva test from DIAGNOS was further comparable with the Abbott Panbio™ COVID-19 Ag Rapid Test designed for nasopharyngeal samples. DIAGNOS and Rapid Response detected nine (50.0%) and seven (38.9%), respectively, of the 18 RT-qPCR positive saliva samples. All RT-qPCR negative saliva (n = 41) were negative with both tests. Only one of the RT-qPCR positive saliva samples contained infectious virus as determined by cell culture and was also positive using the saliva RADs. The results show that the DIAGNOS may be an important and easy-to-use saliva RAD complement to detect SARS-CoV-2 positive individuals, but validation with a larger sample set is warranted.

SARS-CoV-2 in hospital indoor environments is predominantly non-infectious.

BACKGROUND: The ongoing SARS-CoV-2 pandemic has spread rapidly worldwide and disease prevention is more important than ever. In the absence of a vaccine, knowledge of the transmission routes and risk areas of infection remain the most important existing tools to prevent further spread. METHODS: Here we investigated the presence of the SARS-CoV-2 virus in the hospital environment at the Uppsala University Hospital Infectious Disease ward by RT-qPCR and determined the infectivity of the detected virus in vitro on Vero E6 cells. RESULTS: SARS-CoV-2 RNA was detected in several areas, although attempts to infect Vero E6 cells with positive samples were unsuccessful. However, RNase A treatment of positive samples prior to RNA extraction did not degrade viral RNA, indicating the presence of SARS-CoV-2 nucleocapsids or complete virus particles protecting the RNA as opposed to free viral RNA. CONCLUSION: Our results show that even in places where a moderate concentration (Ct values between 30 and 38) of SARS-CoV-2 RNA was found; no infectious virus could be detected. This suggests that the SARS-CoV-2 virus in the hospital environment subsides in two states; as infectious and as non-infectious. Future work should investigate the reasons for the non-infectivity of SARS-CoV-2 virions.

SARS-CoV-2 rapid antigen test: High sensitivity to detect infectious virus.

BACKGROUND: The COVID-19 pandemic has highlighted the need for rapid, cost effective and easy-to-use diagnostic tools for SARS-CoV-2 infections that can be used in point of care settings to limit disease transmission. OBJECTIVE: We evaluated two rapid antigen immunochromatographic tests, Abbott Panbio™ COVID-19 Ag Rapid Test (Panbio) and Zhejiang Orient Gene/Healgen Biotech Coronavirus Ag rapid test cassette (Orient gene) for detection of infectious SARS-CoV-2. RESULTS: The tests were evaluated on nasopharyngeal samples taken from individuals having respiratory and/or COVID-19 related symptoms, which had been analyzed for SARS-CoV-2 RNA using real-time PCR. In total 156 PCR-positive, and 130 (Panbio) and 176 (Orient Gene) PCR-negative samples were analyzed. Overall sensitivity and specificity were 71.8% and 100% for Panbio and 79.5% and 74.4% for the Orient Gene test respectively. The false positives by the Orient Gene test were verified as SARS-CoV-2 negative by in-house real-time PCR assay and were negative for the four seasonal coronaviruses. Subgroup analysis revealed that the antigen tests had high sensitivity for samples with Ct-values <25 (>88%) and for samples containing infectious viruses as determined by cultivation on Vero cells, 94.1% and 97.1% for the Panbio and Orient gene tests, respectively. Furthermore, both tests had a sensitivity of <50 picogram for nucleocapsid protein. No sample with a Ct-value >27 was shown to contain infectious virus. CONCLUSION: The results indicate that the rapid antigen tests, especially the Panbio tests may be a valuable tool to detect contagious persons during the ongoing pandemic.

Presymptomatic viral shedding and infective ability of SARS-CoV-2; a case report.

Possible pre- or asymptomatic transmission has been reported, both from SARS-CoV and from MERS-CoV outbreaks, although this appears to be uncommon. In contrast, during the COVID-19 pandemic, an increasing number of studies and case reports indicate that pre- or asymptomatic transmission of SARS-CoV-2 is not only possible but also occurs frequently. We report repeated rRT-PCR detection of SARS-CoV-2 in a health care worker and demonstrate infective ability up to three days prior to mild COVID-19 symptoms. rRT-PCR indicated high viral levels approximately three days after exposure. Viral samples collected one and three days prior to symptoms exhibited infectivity on Vero E6 cells, confirmed by detection of double-stranded RNA by immunofluorescence, assessment of cytopathic effect (CPE) and rRT-PCR. SARS-CoV-2 specific IgM and IgG antibodies were detected by day 9 and 15, respectively, after symptom onset. We propose that this provides evidence for potential early presymptomatic transmission of SARS-CoV-2 and that infectivity may be manifest shortly after exposure.