Anti-SARS-CoV-2 IgG Antibodies Seen Weeks Before Clearance in Hemodialysis Patients

By David Douglas

June 29, 2020

NEW YORK (Reuters Health) - Patients on maintenance hemodialysis can mount an antibody response against SARS-CoV-2 comparable to that in patients not on hemodialysis, but this is not synonymous with immunity, according to researchers in Belgium.

"Hemodialysis patients are known to have impaired humoral immune responses to vaccination and infection, and it is uncertain whether hemodialysis patients mount an effective antibody response against SARS-CoV- 2," Drs. An S. De Vriese and Marijke Reynders of AZ Sint-Jan Brugge-Oostende AV, in Brugge, write in the American Journal of Kidney Diseases.

In an investigation of 282 maintenance hemodialysis patients, they report that seven developed SARS-CoV-2 infection between March 14 and April 7. All showed COVID-19 symptoms and tested positive for SARS-CoV-2 RNA on a nasopharyngeal swab on the day of symptom onset.

Three patients died, one is still ventilated, and three patients recovered clinically. Longitudinal serum sampling and nasopharyngeal swabs were performed in six of seven patients.

The IgG seroconversion rate was 100% and occurred in the second week after symptom onset. Antibody titer plateaued during the third week and virus persisted in respiratory samples of non-survivors until death.

In survivors, nucleic acid conversion time, defined as the interval from symptom onset to first negative RT-PCR, ranged from 34 to 44 days. Cycle threshold values, an inverse measure of nucleic acid concentration, were lowest in the first week of infection and remained relatively stable thereafter.

Thus, Dr. De Vriese told Reuters Health by email, "the presence of anti-SARS-CoV-2 IgG, as measured by N-protein based ELISA . . . overlaps by several weeks with detectable viral RNA in the upper airways."

Dr. De Vriese cautioned that "this antibody response, while proof of recent exposure to SARS-CoV-2, should not be interpreted as prima facie evidence of immunity to the virus in this population. Viral load was highest during the first week of illness, suggesting that patients are most infectious during this period."

"It remains unclear whether the lower viral loads during the following weeks associate with a clinically relevant transmissibility of SARS-CoV-2 requiring further quarantining," Dr. De Vriese concluded. "Until more evidence is available, the prudent approach is to await negative RT-PCR testing before lifting quarantine."

SOURCE: American Journal of Kidney Diseases, online May 29, 2020.