Plasma-based antigen persistence in the post-acute phase of SARS-CoV-2 infection (preprint)

BACKGROUND: Although RNA viruses like SARS-CoV-2 are generally thought to be transient, the persistence of viral components beyond the acute phase can be driven by a variety of virologic and immunologic factors. Recent studies have suggested that SARS-CoV-2 antigens may persist following COVID-19 but were limited by a lack of comparison to a large number of true negative control samples. METHODS: Using single molecule array (Simoa) assays for SARS-CoV-2 spike, S1, and nucleocapsid antigen in plasma from 171 pandemic-era individuals in the post-acute phase of SARS-CoV-2 infection and 250 pre-pandemic control samples, we compared prevalence of antigen detection. We used logistic regression models and prevalence ratios (PRs) to assess the relationship between demographic and disease factors and antigen persistence. RESULTS: Compared to the proportion of antigen positivity in the pre-pandemic controls (2%), detection of any SARS-CoV-2 antigen was more frequent across all post-acute COVID-19 time bins (3-6 months: 12.6%, p<0.001; 6-10 months, 10.7%, p=0.0002; 10-14 months, 7.5%, p=0.017). These differences were driven by spike protein for up to 14 months and nucleocapsid in the first 6 months after infection. The co-occurrence of multiple antigens at a single timepoint was uncommon. Hospitalization for acute COVID-19 (versus not hospitalized) and worse self-reported health during acute COVID-19 among those not hospitalized (versus more benign illness) were associated with higher prevalence of post-acute antigen detection (PR 1.86, p=0.03; PR 3.5, p=0.07, respectively) in the pandemic era. CONCLUSIONS: Our findings provide strong evidence that SARS-CoV-2 antigens can persist beyond the period of acute illness. The observation that more than 10% of plasma samples for over a year following initial SARS-CoV-2 infection contain detectable viral antigen, which are potentially immunogenic, has significant implications given the sheer number of people infected with SARS-CoV-2 to date. More work will be needed to determine whether these antigens have a causal role in post-acute sequelae of SARS-CoV-2 infection (PASC).

POST-ACUTE SEQUELAE AND ADAPTIVE IMMUNE RESPONSES IN PEOPLE LIVING WITH HIV RECOVERING FROM SARS-COV-2 INFECTION (preprint)

Background: Limited data are available on the long-term clinical and immunologic consequences of SARS-CoV-2 infection in people with HIV (PWH). Methods: We measured SARS-CoV-2 specific humoral and cellular immune responses in people with and without HIV recovering from COVID-19 (n=39 and n=43, respectively) using binding antibody, surrogate virus neutralization, intracellular cytokine staining, and inflammatory marker assays. We identified individuals experiencing symptomatic post-acute sequelae of SARS-CoV-2 infection (PASC) and evaluated immunologic parameters. We used linear regression and generalized linear models to examine differences by HIV status in the magnitude of inflammatory and virus-specific antibody and T cell responses, as well as differences in the prevalence of PASC. Results: Among PWH, we found broadly similar SARS-CoV-2-specific antibody and T cell immune responses as compared with a well-matched group of HIV-negative individuals. PWH had 70% lower relative levels of SARS-CoV-2 specific memory CD8+ T cells (p=0.007) and 53% higher relative levels of PD-1+ SARS-CoV-2 specific CD4+ T cells (p=0.007). Higher CD4/CD8 ratio was associated with lower PD-1 expression on SARS-CoV-2 specific CD8+ T cells (0.34-fold effect, p=0.02). HIV status was strongly associated with PASC (odds ratio 4.01, p=0.008), and the proportion of PD-1+ CD4+ T cells and levels of certain inflammatory markers (IL-6, TNF-alpha, and IP-10) were associated with persistent symptoms. Conclusions: We identified potentially important differences in SARS-CoV-2-specific CD4+ and CD8+ T cells that might have implications for long-term immunity conferred by natural infection. HIV status strongly predicted the presence of PASC. Larger and more detailed studies of PASC in PWH are urgently needed.

Plasma markers of neurologic injury and systemic inflammation in individuals with self-reported neurologic post-acute sequelae of SARS-CoV-2 infection (PASC) (preprint)

Background: The biologic mechanisms underlying neurologic post-acute-sequelae of SARS-CoV-2 infection (PASC) are incompletely understood. Methods: We measured markers of neuronal injury (glial fibrillary acidic protein [GFAP], neurofilament light chain [NfL]) and soluble markers of inflammation among a cohort of people with prior confirmed SARS-CoV-2 infection at early and late recovery following the initial illness (defined as less than and greater than 90 days, respectively). The primary clinical outcome was the presence of self-reported central nervous system (CNS) PASC symptoms during the late recovery timepoint. We compared fold-changes in marker values between those with and without CNS PASC symptoms using linear mixed effects models and examined relationships between neurologic and immunologic markers using rank linear correlations. Results: Of 121 individuals, 52 reported CNS PASC symptoms. During early recovery, those who went on to report CNS PASC symptoms had elevations in GFAP (1.3-fold higher mean ratio, 95% CI 1.04-1.63, p=0.02), but not NfL (1.06-fold higher mean ratio, 95% CI 0.89-1.26, p=0.54). During late recovery, neither GFAP nor NfL levels were elevated among those with CNS PASC symptoms. Although absolute levels of NfL did not differ, those who reported CNS PASC symptoms demonstrated a stronger downward trend over time in comparison to those who did not report CNS PASC symptoms (p=0.041). Those who went on to report CNS PASC also exhibited elevations in IL-6 (48% higher during early recovery and 38% higher during late recovery), MCP-1 (19% higher during early recovery), and TNF-alpha (19% higher during early recovery and 13% higher during late recovery). GFAP and NfL correlated with levels of several immune activation markers during early recovery; these correlations were attenuated during late recovery. Conclusions: Self-reported neurologic symptoms present >90 days following SARS-CoV-2 infection are associated with elevations in markers of neurologic injury and inflammation at early recovery timepoints, suggesting that early injury can result in long-term disease. The correlation of GFAP and NfL with markers of systemic immune activation suggests one possible mechanism that might contribute to these symptoms. Additional work is needed to better characterize these processes and to identify interventions to prevent or treat this condition.

Markers of immune activation and inflammation in individuals with post-acute sequelae of SARS-CoV-2 infection (preprint)

BACKGROUND: The biological processes associated with post-acute sequelae of SARS-CoV-2 infection (PASC) are unknown. METHODS: We measured soluble markers of inflammation in a SARS-CoV-2 recovery cohort at early (<90 days) and late (>90 days) timepoints. We defined PASC as the presence of one or more COVID-19-attributed symptoms beyond 90 days. We compared fold-changes in marker values between those with and without PASC using mixed effects models with terms for PASC and early and late recovery time periods. RESULTS: During early recovery, those who went on to develop PASC generally had higher levels of cytokine biomarkers including TNF-alpha (1.14-fold higher mean ratio, 95%CI 1.01-1.28, p=0.028) and IP-10 (1.28-fold higher mean ratio, 95%CI 1.01-1.62, p=0.038). Among those with PASC, there was a trend toward higher IL-6 levels during early recovery (1.28-fold higher mean ratio, 95%CI 0.98-1.70, p=0.07) which became more pronounced in late recovery (1.44-fold higher mean ratio, 95%CI: 1.11-1.86, p<0.001). These differences were more pronounced among those with a greater number of PASC symptoms. CONCLUSIONS: Persistent immune activation may be associated with ongoing symptoms following COVID-19. Further characterization of these processes might identify therapeutic targets for those experiencing PASC.

Decrease in Hospitalizations for COVID-19 after Mask Mandates in 1083 U.S. Counties (preprint)

Importance: Population-wide facial masking decreases COVID-19 transmission but may also decrease the severity of disease by reducing the viral inoculum to which the wearer is exposed. The mortality of COVID-19 infection decreased in the U.S. in the second wave over the summer of 2020 compared to the first, but reasons for declining severity of disease have not been fully elucidated. Objective: To determine if facial mask mandates instituted in U.S. counties over the spring and summer of 2020 were associated with declining severity of infection as measured by the number of hospitalizations for COVID-19. Design: Data on hospitalizations due to COVID-19; testing access determined by number of tests performed per day per 100,000 people; new cases per day normalized by population; measures of population mobility to control for other non-pharmaceutical interventions such as lockdowns, social distancing, and business closures; age categories in each census tract; and dates of masking mandates in U.S. counties were all obtained from open-sourced epidemiologic datasets. We used a staggered difference-in-difference study design to assess the impact of the introduction of mask mandates (defined as the treatment) on the proportion of hospitalizations due to COVID-19 per week from March 10-September 16, 2020. Setting: U.S. counties with available full datasets on relevant COVID-19 metrics Exposure: Mask mandates Main outcome: Proportion of hospitalizations due to COVID-19 Results: Using data from 1083 counties (34% of U.S. counties, 82% of U.S. population) from 49 states, we found a statistically significant drop in hospitalization rates due to COVID-19 up to 12 weeks following county mask mandates of 7.13 (95% CI: -4.19, -10.1) percentage points, after controlling for age categories by county, testing access, numbers of cases, and population mobility. Conclusion and Relevance: Facial masking may decrease COVID-19 severity by decreasing the viral inoculum to which individuals are exposed. Mask mandates across 1083 counties in the U.S. in 49 states decreased hospitalization rates from COVID-19 even when controlling for other factors that could impact disease severity, including age, testing access, number of cases, and mobility (as a proxy for other non-Pharmaceutical interventions such as sheltering-in-place). This study adds to the growing evidence for the impact of masking on disease severity and on the utility of population-wide facial masking for COVID-19 pandemic control.