Serological Response in Lung Transplant Recipients after Two Doses of SARS-CoV-2 mRNA Vaccines

The immunological effectiveness of SARS-CoV-2 mRNA vaccines in lung transplant (LT) recipients is largely unknown. Thus, we assessed the effect of Pfizer-BioNTech and Moderna mRNA vaccines two-dose (2D) regimen on humoral responses in immunocompromised lung transplant (LT) recipients. About 25% (18/73) of SARS-CoV-2 uninfected-LT patients generated positive spike-IgG response following 2D of vaccines, with 36% (9/25) in the Moderna cohort and only 19% (9/48) in the Pfizer cohort. 2D in LT patients elicited significantly lesser median IgGSP response (1.7 AU/mL, 95% CI: 0.6-7.5 AU/mL) compared to non-transplanted, uninfected naive subjects (14209 AU/mL, 95% CI: 11261-18836 AU/mL) (p<0.0001). In LT patients, Moderna-evoked seropositivity trend was higher by 23-fold than Pfizer. 2D COVID-19 vaccination elicits a dampened serological response in LT patients. Whether assessing other arms of host immunity combined with higher vaccine dose can better capture and elicit improved immunogenicity in this immunocompromised population warrants investigation.

Multiplex Fragment Analysis Identifies SARS-CoV-2 Variants

The rapid spread of SARS-CoV-2 Variants of Concern (VOC) necessitates systematic efforts for epidemiological surveillance. The current method for identifying variants is viral whole genome sequencing (WGS). Broad clinical adoption of sequencing is limited by costly equipment, bioinformatics support, technical expertise, and time for implementation. Here we describe a scalable, multiplex, non-sequencing-based capillary electrophoresis assay to affordably screen for SARS-CoV-2 VOC.

Clinical evaluation of the Abbott Alinity SARS-CoV-2 spike-specific quantitative IgG and IgM assays in infected, recovered, and vaccinated groups

The COVID-19 pandemic continues to impose a significant burden on global health infrastructure. While identification and containment of new cases remains important, laboratories must now pivot and consider assessment of SARS-CoV-2 immunity in the setting of the recent availability of multiple COVID-19 vaccines. Here we have utilized the latest Abbott Alinity semi-quantitative IgM and quantitative IgG spike protein (SP) serology assays (IgMSP and IgGSP) in combination with Abbott Alinity IgG nucleocapsid (NC) antibody test (IgGNC) to assess antibody responses in a cohort of 1236 unique participants comprised of naive, SARS-CoV-2 infected, and vaccinated (including both naive and recovered) individuals. The IgMSP and IgGSP assays were highly specific (100%) with no cross-reactivity to archived samples recovered prior to the emergence of SARS-CoV-2, including those from individuals with seasonal coronavirus infections. Clinical sensitivity was 96% after 15 days for both IgMSP and IgGSP assays individually. When considered together, the sensitivity was 100%. A combination of NC- and SP-specific serologic assays clearly differentiated naive, SARS-CoV-2-infected, and vaccine-related immune responses. Vaccination resulted in a significant increase in IgGSP and IgMSP titers, with a major rise in IgGSP following the booster (second) dose in the naive group. In contrast, SARS-CoV-2 recovered individuals had several fold higher IgGSP responses than naive following the primary dose, with a comparatively dampened response following the booster. This work illustrates the strong clinical performance of these new serological assays and their utility in evaluating and distinguishing serological responses to infection and vaccination.

Evaluation of symptomatic patient saliva as a sample type for the Abbott ID NOW COVID-19 assay

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has presented significant challenges for laboratories including supply chain limitations with restricted access to reagents and sample collection materials (i.e. swabs, viral transport media (VTM)) for patients testing. Therefore, saliva has been evaluated as an alternative specimen for COVID-19 diagnosis. comparable performance between dry nasal swabs (NS) and nasopharyngeal swabs (NPS) collected in VTM has been observed with the ID NOW for SARS-CoV-2; the majority of false-negative results occur with higher cycle number (CN) or cycle threshold (Ct) values suggesting low viral load in these specimens. We performed clinical validation of saliva specimens on the ID NOW molecular platform to detect SARS-CoV-2. Saliva was compared to nasopharyngeal swabs tested on the ID NOW and the Cepheid molecular assay. We also performed stability studies of saliva samples over 5 days. A total of 96 saliva samples and 64 paired NPS were analyzed. We observed 78% (18/23) positive percent agreement (PPA) and 100% (44/44) negative percent agreement (NPA) between matched saliva and nasopharyngeal specimens performed on ID NOW. We found 83% (19/23) PPA and 100% NPA (25/25) between saliva run on the ID NOW and Cepheid assay. Six saliva specimens positive for SARS-CoV-2 were continuously positive for five days when stored at room temperature. Therefore, we propose further investigation of saliva as an alternative sample type for testing symptomatic patients with ID NOW as a promising method to address COVID-19 testing.

SARS-CoV-2 Antibody responses do not predict COVID-19 disease severity

BackgroundInitial reports indicate adequate performance of some serological-based SARS-CoV-2 assays. However, additional studies are required to facilitate interpretation of results, including how antibody levels impact immunity and disease course. MethodsIn this study, a total of 968 subjects were tested for IgG antibodies reactive to SARS-CoV-2. We confirmed analytic specificity using 656 plasma samples from healthy donors, 49 sera from patients with rheumatic disease, and 90 specimens from individuals positive for PCR-based respiratory viral panel. One-hundred seventy-three cases of confirmed or suspected SARS-CoV-2 were tested for IgG. A subgroup of 37 SARS-CoV-2 PCR-positive cases was tested for nucleocapsid-specific IgM antibody using an in-house developed microarray method. Antibody levels were compared between disease severity groups. ResultsAll specificity specimens were negative for SARS-CoV-2 IgG antibodies (0/656, 0%). Cross reactivity was not detected in specimens with antinuclear antibodies and rheumatoid factor, or cases with previous diagnosis of viral infection including human coronavirus. Positive agreement of IgG with PCR was 83% of samples confirmed to be more than 14 days from symptom onset, with less than 100% sensitivity attributable to a case with severe immunosuppression. Virus-specific IgM was positive in a higher proportion of cases less than 3 days from symptom onset. No association was observed between mild and severe disease course with respect to IgG and IgM levels. ConclusionsThe studied SARS-CoV-2 IgG assay had 100% specificity and no adverse cross-reactivity. Index values of IgG and IgM antibodies did not predict disease severity in our patient population.