Kinetics of Anti–SARS-CoV-2 IgG Antibodies in Hemodialysis Patients Six Months after Infection
Authors: Sakhi Hamza , Dahmane Djamal , Attias Philippe , Kofman Thomas , Bouvier Magali , Lapidus Nathanael , Fourati Slim , El Karoui Khalil ,   Mondor NephroCov Study Group
Published: February 2021

Significance Statement
The humoral response over time against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is poorly understood. The authors investigated the long-term kinetics of the antibody response to SARS-CoV-2 (specifically, IgG against nucleocapsid and spike antigens), in 83 patients on in-center hemodialysis who recovered from coronavirus disease 2019 (COVID-19). They found that 10% of patients had no initial seroconversion, which was associated with immunocompromised status; in patients with seroconversion, IgG antibodies decayed over time. Factors associated with this decline included older age, female sex, and nonsevere clinical presentation. About 25% of patients had negative IgG antinucleocapsid serology after 6 months, whereas most patients maintained antispike antibodies. By characterizing the evolution of the SARS-CoV-2 antibody response, these findings might help better define future therapeutic and preventive approaches against COVID-19 in patients on hemodialysis.

Background
The humoral response against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the hemodialysis population, including its dynamics over time, remains poorly understood.

Methods
To analyze initial and long-term humoral responses against SARS-CoV-2 in a hemodialysis population, we retrospectively evaluated findings from SARS-CoV-2 IgG serologic assays targeting the nucleocapsid antigen or spike antigen up to 6 months of follow-up in patients on hemodialysis in the Paris, France, region who had recovered from coronavirus disease 2019 (COVID-19).

Results
Our analysis included 83 patients (median age 65 years); 59 (71%) were male and 28 (34%) had presented with severe COVID-19. We observed positive initial SARS-CoV-2 IgG antinucleocapsid serology in 74 patients (89%) at a median of 67 days postdiagnosis. By multivariable analysis, immunocompromised status was the only factor significantly associated with lack of an IgG antinucleocapsid antibody response. Follow-up data were available at 6 months postdiagnosis for 60 of 74 patients (81%) with positive initial antinucleocapsid serology, and 15 (25%) of them had negative antinucleocapsid serology at month 6. In total, 14 of 15 sera were tested for antispike antibodies, 3 of 14 (21%) of which were also negative. Overall, 97% of antinucleocapsid-antibody–positive specimens were also antispike-antibody positive. Female sex, age >70 years, and nonsevere clinical presentation were independently associated with faster IgG antinucleocapsid titer decay in multivariable analysis. After adjustment for sex and age >70 years, nonsevere clinical presentation was the only factor associated with faster decay of IgG antispike antibodies.

Conclusions
This study characterizes evolution of the SARS-CoV-2 antibody response in patients on hemodialysis and identifies factors that are associated with lack of seroconversion and with IgG titer decay.