CMV seropositivity in older adults changes T cell functionality, but does not prevent antibody or cellular SARS-CoV-2 vaccine responses

Chronic infection with human cytomegalovirus (CMV) may contribute to poor vaccine efficacy in older adults. We assessed effects of CMV serostatus on antibody quantity and quality, as well as cellular memory recall responses, after 2 and 3 SARS-CoV-2 mRNA vaccine doses, in older adults in assisted living facilities. CMV serostatus did not affect anti-Spike and anti-RBD IgG antibody levels, nor neutralization capacity against wildtype or beta variants of SARS-CoV-2 several months after vaccination. CMV seropositivity altered T cell expression of senescence-associated markers and increased TEMRA cell numbers, as has been previously reported; however, this did not impact Spike-specific CD4+ T cell memory recall responses. CMV seropositive individuals did not have a higher incidence of COVID-19, though prior infection influenced humoral immunity. Therefore, CMV seropositivity may alter T cell composition but does not impede the durability of humoral protection or cellular memory responses after SARS-CoV-2 mRNA vaccination in older adults. Key PointsCMV seropositive older adults have more EMRA and terminally differentiated T cells CMV seropositivity does not prevent antibody maintenance after SARS-CoV-2 vaccination CMV seropositivity does not impede SARS-CoV-2 vaccine T cell memory recall responses

Lasting changes to circulating leukocytes in people with mild SARS-CoV-2 infections

Survivors of severe SARS-CoV-2 infections frequently suffer from a range of post-infection sequelae. Whether survivors of mild or asymptomatic infections can expect any long-term health consequences is not yet known. Herein we investigated lasting changes to soluble inflammatory factors and cellular immune phenotype and function in individuals who had recovered from mild SARS-CoV-2 infections (n=22) compared to those that had recovered from other mild respiratory infections (n=11). Individuals who had mild SARS-CoV-2 infections had elevated levels of C-reactive protein 1-3 months after symptom onset, and changes in phenotype and function of circulating T cells that were not apparent in individuals 6-9 months post-symptom onset. Markers of monocyte activation and expression of adherence and chemokine receptors indicative of altered migratory capacity were also higher at 1-3 months post-infection in individuals who had mild SARS-CoV-2, but these were no longer elevated by 6-9 months post-infection. Perhaps most surprisingly, polyclonal activation of T cells was higher in individuals who had recently experienced a mild SARS-CoV-2 infection compared to individuals with other recent respiratory infections. These data are indicative of prolonged immune activation and systemic inflammation that persists for up to three months after mild or asymptomatic SARS-CoV-2 infections.

Platelet Activating Immune Complexes Identified in COVID-19 Associated Coagulopathy

Thrombosis is a prominent feature of coronavirus disease 2019 (COVID-19) and often occurs in patients who are critically ill; however, the mechanism is unclear. This COVID-19 associated coagulopathy (CAC) shares features with heparin-induced thrombocytopenia (HIT), including mild thrombocytopenia and thrombosis. We thus tested 10 CAC patients for anti-PF4/heparin antibodies and functional platelet activation. HIT was excluded in all samples based on anti-PF4/heparin antibody and serotonin release assay results. Of note, 6 CAC patients demonstrated platelet activation by the serotonin release assay that was inhibited by Fc{gamma}RIIA receptor blockade, confirming an IgG-specific immune complex (IC)-mediated reaction. Platelet activation was independent of heparin, but inhibitable by both therapeutic and high dose heparin. All 6 samples were positive for IgG-specific antibodies targeting the receptor binding domain (RBD) or the spike protein of the SARS-CoV-2 virus. These samples were additionally characterized by significant endothelial activation, shown by increased von Willebrand factor antigen and activity. ADAMTS13 activity was not severely reduced, and ADAMTS13 inhibitors were not present, ruling out thrombotic thrombocytopenic purpura. Our study thus identifies platelet-activating ICs as a mechanism that contributes to CAC thrombosis. Scientific CategoryThrombosis and Hemostasis Key PointsO_LIPatients with COVID-19 thrombosis have immune complexes that activate platelets through Fc{gamma}RIIA signalling C_LIO_LIPatients with COVID-19 thrombosis demonstrate increased VWF antigen and activity that is not related to severe ADAMTS13 reduction C_LI

Development of a serological assay to identify SARS-CoV-2 antibodies in COVID-19 patients

Coronavirus Disease 2019 (COVID-19) is a global pandemic caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While detection of SARS-CoV-2 by polymerase chain reaction with reverse transcription (RT-PCR) is currently used to diagnose acute COVID-19 infection, serological assays are needed to study the humoral immune response to SARS-CoV-2. SARS-CoV-2 IgG/A/M antibodies against SARS-CoV-2 spike (S) protein and its receptor-binding domain (RBD) were characterized using an enzyme-linked immunosorbent assay (ELISA) and assessed for their ability to neutralize live SARS-CoV-2 virus in recovered subjects who were RT-PCR-positive (n=153), RT-PCR-negative (n=55), and control samples collected pre-COVID-19 (n=520). Anti-SARS-CoV-2 antibodies were detected in 90.9% of resolved subjects up to 180 days post-symptom onset. Anti-S protein and anti-RBD IgG titers correlated (r= 0.5157 and r = 0.6010, respectively) with viral neutralization. Of the RT-PCR-positive subjects, 22 (14.3%) did not have anti-SARS-CoV-2 antibodies; and of those, 17 had RT-PCR cycle threshold (Ct) values >27, raising the possibility that these indeterminate results are from individuals who were not infected, or had mild infection that failed to elicit an antibody response. This study highlights the importance of serological surveys to determine population-level immunity based on infection numbers as determined by RT-PCR.