Liquid-based cytological and immunohistochemical study of nasopharyngeal swab from persons under investigation for SARS-CoV-2 infection

Sputum characteristics of patients with severe COVID-19: report of two cases with immunocytochemical detection of SARS-CoV-2 spike protein

Patients with SARS-CoV-2 infection and with severe COVID-19 often have multiple coinfections, and their treatment is challenging. Here, we performed cytology analysis on sputum samples from two patients with severe COVID-19. The specimens were prepared using the rubbing method and stained with Papanicolaou stain. In both cases, several cells with frosted nuclei were observed, and the cytological findings per 100 cells were evaluated. The infected cells were mononuclear to multinuclear, showing chromatin aggregation at the nuclear margins, intranuclear inclusion bodies, eosinophilic cytoplasmic inclusion bodies, and mutual pressure exclusion of the nuclei. Immunocytochemical staining revealed that the cells were positive for AE1/AE3 and negative for CD68 expression, indicating their epithelial origin. Furthermore, infected cells with frosted nuclei were positive for surfactant protein A (SP-A) in Case 2, suggesting infection of type II alveolar pneumocytes or Clara cells. Moreover, in Case 2, the infected cells were positive for herpes simplex virus (HSV) I + II and SARS-CoV-2 spike protein, confirming double infection in these cells. In conclusion, sputum cytology is an important tool for determining the diversity of viral infection, and additional immunocytochemistry can be used for definitive diagnosis.

Morphological alterations in tongue epithelial cells infected by SARS-CoV-2: A case-control study

Objective

The aim of the present case–control study was to evaluate the morphological aspects of the epithelial cells from the dorsum of the tongue and the expression of the SARS‐CoV‐2 Spike protein in these cells, in patients with and without COVID‐19 infection.

Methods

24 individuals with at least one symptom of COVID‐19 were recruited among inpatients from Hospital Universitário Pedro Ernesto (Rio de Janeiro, Brazil). 14 patients who tested positive for COVID‐19 by RT‐PCR were included in the case group, and 10 patients who tested negative were included in the control group. Cytological smears from the dorsum of the tongue were obtained from all patients and analyzed using immunohistochemistry directed against SARS‐CoV‐2‐Spike protein. Morphological changes in epithelial cells were analyzed using light microscopy.

Results

Immunohistochemistry showed that 71% of the COVID‐19 patients presented epithelial cells positive for the presence of the SARS‐CoV‐2 Spike protein, and all cells coming from patients in the control group were negative. Cytological analysis showed significant differences when comparing epithelial cells from COVID‐19‐positive and COVID‐19‐negative patients.

Conclusion

COVID‐19 may generate dimensional changes in tongue epithelial cells; however, further studies are necessary to understand how this happens.

SARS-CoV-2 pseudovirus infectivity and expression of viral entry-related factors ACE2, TMPRSS2, Kim-1, and NRP-1 in human cells from the respiratory, urinary, digestive, reproductive, and immune systems

Infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes a wide spectrum of syndromes involving multiple organ systems and is primarily mediated by viral spike (S) glycoprotein through the receptor-binding domain (RBD) and numerous cellular proteins including ACE2, transmembrane serine protease 2 (TMPRSS2), kidney injury molecule-1 (Kim-1), and neuropilin-1 (NRP-1). In this study, we examined the entry tropism of SARS-CoV-2 and SARS-CoV using S protein-based pseudoviruses to infect 22 cell lines and 3 types of primary cells isolated from respiratory, urinary, digestive, reproductive, and immune systems. At least one cell line or type of primary cell from each organ system was infected by both pseudoviruses. Infection by pseudoviruses is effectively blocked by S1, RBD, and ACE2 recombinant proteins, and more weakly by Kim-1 and NRP-1 recombinant proteins. Furthermore, cells with robust SARS-CoV-2 pseudovirus infection had strong expression of either ACE2 or Kim-1 and NRP-1 proteins. ACE2 glycosylation appeared to be critical for the infections of both viruses as there was a positive correlation between infectivity of either SARS-CoV-2 or SARS-CoV pseudovirus with the level of glycosylated ACE2 (gly-ACE2). These results reveal that SARS-CoV-2 cell entry could be mediated by either an ACE2-dependent or -independent mechanism, thus providing a likely molecular basis for its broad tropism for a wide variety of cell types.

The COVID-19 pandemic: Pathologists support the clinical infectious diseases team

The pathologist is involved in many diagnostic steps together with the clinical infectious disease team in the management of COVID-19-affected patients. In particular, cytological and histopathological procedures as well as autoptic findings may represent useful tools to better understand the pathobiology of the disease as well as to correctly define causes of death. Moreover, pathologists have been forced to reconsider the usual laboratory workflow and introduce adequate guidelines against virus diffusion in the COVID-19 pandemic, requiring high biosafety levels.