Low SARS-CoV-2 RNA Levels in Corneas of Viremic COVID-19 Patients

By Reuters Staff

January 29, 2021

NEW YORK (Reuters Health) - Autopsy results suggest that corneal transplant from donors with COVID-19 may not necessarily lead to transmission of the disease, although more research is required, according to German researchers.

The cornea is the most frequently transplanted tissue worldwide and demand is high, Dr. Maria Casagrande and colleagues at University Medical Center Hamburg-Eppendorf, in Hamburg, note in JAMA Ophthalmology.

However, they add, the current recommendation from the Global Alliance of Eye Bank Associations is to avoid tissue from donors infected with SARS-CoV-2 or recently been exposed to it.

The only previous study of the corneas of five such subjects found the virus absent, the team notes. To gain further information, they prospectively analyzed corneal tissue from 11 deceased patients with COVID-19. Six were women, their mean age was 69 years and one corneal disc was harvested from each subject. Postmortem SARS-CoV-2 viremia was detected in five of nine patients.

Virus isolation failed in all corneal-disc samples and infectivity or presence of viral structural proteins could not be confirmed in any eye. However, SARS-CoV-2 genomic RNA was detected in the cornea of six eyes and subgenomic RNA was present in four of them.

The latter group also had positive results for SARS-CoV-2 RNA in four of six conjunctival swab samples, one of three aqueous humor samples, three of five vitreous humor samples, and four of five blood samples.

In addition, the "rather high" 46% rate of positive PCR results seen in conjunctival swab samples contrasted with previous studies showing positive PCR results ranging from 1.4% to 4.5%, the researchers say. This "might be explained by the severity of disease and high viral loads induced by patient selection, especially because patients with a high viral load in throat swab samples were selected."

The current findings, the team points out, do not necessarily contradict those seen in the earlier negative corneal-disc study because in that study, "viral load in the blood was not examined and no patient selection was performed. In our study, two-thirds of the PCR positive corneal discs were obtained from patients with viremia, which is uncommon in patients with COVID-19."

The researchers conclude, "The low RNA loads in corneal samples suggest a low risk of infection through a corneal transplant, even in a high-risk cohort of patients with viremia. Nevertheless, infection via a contaminated corneal graft cannot be fully excluded."

Dr. Casagrande did not respond to requests for comments.

SOURCE: https://bit.ly/2YjotF7 JAMA Ophthalmology, online January 21, 2021.