Studies have reported that SARS-CoV-2 remains in the tissues of patients with long COVIDs.

In a recent study posted on Research Square*, Researchers investigated whether the residual severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen Ribonucleic acid (RNA) is present in tissue samples of patients with long-term coronavirus disease (COVID-19) (LC) in 2019 beyond the recovery phase of COVID-19.

Background

SARS-CoV-2 is a single-stranded RNA virus containing four structural proteins such as nucleocapsid (NP), membrane (M), spike (S), and envelope (E), as well as several nonstructural and accessory proteins. am. Which NP is the most diagnostically important?

A nucleocapsid morphological complex with viral genomic RNA that interacts with viral membrane proteins in virion assembly and plays an important role in increasing the efficiency of viral transcription. Nucleocapsid contains NP antigens that can be detected by various serological diagnostic techniques based on host anti-NP antibodies such as immunohistochemistry, viral NP antigens that bind to (IHC). Immunostaining techniques such as IHC include the use of color-developing enzymes and special staining with or without fluorescence to detect the presence of specific antigens in tissue samples.

The presence of single-stranded, positive-sense genomic RNA in the -2 molecular structure of SARS-CoV requires the presence of negative-sense or replicating RNA. This RNA is used as a template for synthesizing new RNA copies that are essential for viral replication. If the virus count is high enough, the clinical manifestations of COVID-19 initiation occur in the human body.

According to the World Health Organization (WHO), LC is a medical condition, COVID19 Symptoms Like fever, brain fog, malaise, myalgia, and shortness of breath persist in the patient beyond the acute phase of the illness and cannot be attributed to other diagnoses.

Residual genomic viral RNA copies contribute to continued viral replication in the host nucleus and can cause immune system reactivation and reinfection in the presence of increased viral numbers. Asymptomatic COVID-19 patients with residual viral cells are also at risk of transmitting the virus to other individuals. The presence of residual viral antigens can lead to false positive results and reduce the accuracy of existing diagnostic procedures. Accurate and rapid diagnosis of these residual viral cells and antigens can reduce the risk of reinfection and the likelihood of false positive results, respectively.

Previous studies have established that residual SARS-CoV -2 RNA and antigens are present in fecal and convalescent LC patients’ gastrointestinal (GI) samples. However, information on detecting live viral cells in human organ tissues is sparse.

About research

In this study, are residual viral antigens and RNA present in the converged tissues obtained from the skin, breast, and appendix of two LC patients approximately 6 and 18 months after COVID-19 diagnosis? I evaluated it. IHC analysis was used to detect SARS-CoV-2NP, while RNAscope was used to detect the presence of residual positive and negative sense RNA.

Anti-SARS-CoV-2 labeled against GI tissue NP antigen obtained from another set in 2019 to validate the study results and eliminate the possibility of positive tissue staining due to infections other than COVID-19. -Tested for NP antibody. LC patient. GI tissue is the main site Viral shedding High expression of virus spike (S) protein binding host angiotensin converting enzyme 2 (hACE2) receptor.

result

Residual virus was detected by IHC in the appendix of breast tissue and in the area adjacent to the tumor. However, no viral antigen was identified in the tumor. The skin did not absorb the ICH stain, probably due to the high cell turnover rate of the skin cells.

Negative sense (template or intermediate replication) RNA and positive sense (viral genome) RNA are detected in breast and appendix tissues using an RNAscope and show constant viral replication.

Conclusion

The study results demonstrated that SARS-CoV-2 antigens and particles survive in human tissues for more than a year after COVID-19 diagnosis. These residual cells must be diagnosed and eradicated at the earliest to accelerate the recovery of a complete host, reduce the likelihood of reinfection, and improve the accuracy of the diagnostic procedure.

Verification and standardization of study results requires future studies with larger sample sizes incorporating different populations around the world. Further research is also needed to determine why there is no residual SARS-CoV-2 antigen and RNA in breast tumors and skin cells, and to investigate whether the gastrointestinal tract is a true reservoir of SARS-CoV-2. It will help.

*Important Notices

The Study Square publishes a preliminary scientific report that has not been peer-reviewed and should therefore not be considered definitive or treated as definitive information that guides clinical practice / health-related behaviors...