Interplay of antibody and cytokine production reveals CXCL-13 as a potential novel biomarker of lethal SARS-CoV-2 infection

Horspool, A. M.; Kieffer, T.; Russ, B. P.; DeJong, M. A.; Wolf, M. A.; Karakiozis, J. M.; Hickey, B. J.; Fagone, P.; Tacker, D. H.; Bevere, J. R.; Martinez, I.; Barbier, M.; Perrotta, P. L.; Damron, F. H.

The SARS-CoV-2 pandemic is continuing to impact the global population. This study was designed to assess the interplay of antibodies with the systemic cytokine response in SARS-CoV-2 patients. We demonstrate that significant anti-SARS-CoV-2 antibody production to Receptor Binding Domain (RBD), Nucleocapsid (N), and Spike S1 subunit (S1) of SARS-CoV-2 develops over the first 10 to 20 days of infection. The majority of patients produced antibodies against all three antigens (219/255 SARS-CoV-2 positive patient specimens, 86%) suggesting a broad response to viral proteins. Patient mortality, sex, blood type, and age were all associated with differences in antibody production to SARS-CoV-2 antigens which may help explain variation in immunity between these populations. To better understand the systemic immune response, we analyzed the production of 20 cytokines by SARS-CoV-2 patients over the course of infection. Cytokine analysis of SARS-CoV-2 positive patients exhibited increases in proinflammatory markers (IL-6, IL-8, IL-18) and chemotactic markers (IP-10, SDF-1, MIP-1{beta}, MCP-1, and eotaxin) relative to healthy individuals. Patients who succumbed to infection produced decreased IL-2, IL-4, IL-12, IL-13, RANTES, TNF-, GRO-, and MIP-1 relative to patients who survived infection. We also observed that the chemokine CXCL13 was particularly elevated in patients that succumbed to infection. CXCL13 is involved in B cell activation, germinal center development, and antibody maturation, and we observed that CXCL13 levels in blood trended with anti-SARS-CoV-2 antibody production. Furthermore, patients that succumbed to infection produced high CXCL13 and also tended to have high ratio of nucleocapsid to RBD antibodies. This study provides insights into SARS-CoV-2 immunity implicating the magnitude and specificity of response in relation to patient outcomes.