ALBERT

Description: Given the limited availability of serological testing to date, the seroprevalence of SARS-CoV-2-specific antibodies in different populations has remained unclear. Here, we report very low SARS-CoV-2 seroprevalence in two San Francisco Bay Area populations. Seroreactivity was 0.26% in 387 hospitalized patients admitted for non-respiratory indications and 0.1% in 1,000 blood donors in early April 2020. We additionally describe the longitudinal dynamics of immunoglobulin-G (IgG), immunoglobulin-M (IgM), and in vitro neutralizing antibody titers in COVID-19 patients. The median time to seroconversion ranged from 10.3–11.0 days for these 3 assays. Neutralizing antibodies rose in tandem with immunoglobulin titers following symptom onset, and positive percent agreement between detection of IgG and neutralizing titers was 〉93%. These findings emphasize the importance of using highly accurate tests for surveillance studies in low-prevalence populations, and provide evidence that seroreactivity using SARS-CoV-2 anti-nucleocapsid protein IgG and anti-spike IgM assays are generally predictive of in vitro neutralizing capacity.

Description: Abstract 3466 Donor cell leukemia (DCL) in the setting of bone marrow/hematopoietic stem cell transplant (HCT) has not been well characterized. We analyzed 9 cases of DCL and performed a literature review (table). The indications for transplant and subtypes of DCL are shown (table). The 6 myelodysplastic syndrome (MDS) cases included 1 case of refractory cytopenia with multilineage dysplasia (RCMD), 2 cases of refractory anemia and 3 cases which were unclassifiable. Conventional cytogenetic analysis was performed on all 9 cases of DCL (table). All 9 cases had engraftment studies performed either by short tandem repeat analysis (3) or FISH analysis for donor gonosomal complement (6) when DCL was diagnosed. Seven cases had either engraftment studies or cytogenetic analysis performed periodically after HCT to test the donor cell engraftment and engraftment was confirmed in all. FISH analysis for monosomy 7, del(7q) and del(5q) was retrospectively performed on preserved donor cells in 4 cases after DCL was diagnosed. A low level of abnormalities was observed in preserved donor cells for the cases with del(7q) (2.9%) and del(5q) (8.2%). The 2 cases of AML received chemotherapy. Of the MDS cases, 2 received donor cell infusion, 1 received 6 cycles of revlimid, and 3, along with the case of CLL, received either supportive therapy or were simply observed. Six cases have clinical follow up ≥ 5 months and of these, 1 died of disease (AML) while the other 5 are alive, including 4 MDS and the 1 CLL. The disproportionate detection of DCL in sex mismatched HCT suggests a probable under-detection in the sex-matched population. In our analysis, the interval between HCT and diagnosis of DCL (table) falls within the range of currently reported cases. When stratified by type of DCL, the T-LGL group demonstrates presentation significantly earlier than other groups (Fig. A), indicating pathogenesis of T-LGL may involve a distinct pathway. When stratified by types of primary disease, the interval of the neoplastic group is shorter than that of benign group (Fig. B), implying that pre-HCT treatment may play a role in the pathogenesis of DCL. When stratified by stem cell sources, UCB group shows shorter latency than the other sources (Fig. C), suggesting a higher risk of DCL in this cell source. The low level cytogenetic abnormalities of preserved donor cells in our series and the longer latency of the benign group suggest that donor cells with an intrinsic defect may be predisposed to evolve into DCL. Total cases (%) Reported cases (%) Current cases (%) Number of cases 83 74 9 Age (years)     Median/range 37.0/3~70 36.0/4~62 53.0/3~70 Gender     Male 43 (52.4) 38 (52.0) 5 (55.6)     Female 39 (47.6) 35 (48.0) 4 (44.4) Primary disease     Neoplasms 76 (91.6) 67 (90.5) 9 (100)     Non-neoplasms 7 (8.4) 7 (9.5) 0 (0.0) Donor     Related 59 (72.0) 54 (74.0) 5 (55.6)     Unrelated 23 (28.0) 19 (26.0) 4 (44.4)     Sex-matched 28 (34.6) 27 (37.5) 1 (11.1)     Sex-mismatched 53 (65.4) 45 (62.5) 8 (88.9) Donor cell source     BM 48 (63.2) 44 (65.7) 4 (44.4)     BHSC 16 (21.0) 13 (19.4) 3 (33.3)     UCB 12 (15.8) 10 (14.9) 2 (22.2) 2nd neoplasm (DCL)     AML 31 (37.4) 29 (39.2) 2 (22.2)     MDS/MPN* 27 (32.5) 21 (28.4) 6 (66.7)     ALL 20 (24.1) 20 (27.0) 0 (0.0)     T-LGL 4 (4.8) 4 (5.4) 0 (0.0)     CLL 1 (1.2) 0 (0.0) 1 (11.1) Interval (months)     Median/range 24.0/1~312 24.0/2~312 26.0/1~193 Cytogenetics     Normal 21 (28.0) 20 (30.3) 1 (11.1)     Abnormal 54 (72.0) 46 (69.7) 8 (88.9)     -7 or del(7q)** 15 (27.8) 10 (21.7) 5 (62.5)     +8** 2 (3.7) 2 (4.4) 0 (0.0)     Del(20)** 4 (7.4) 2 (4.4) 2 (25.0)     Del(5q)** 2 (3.7) 1 (2.2) 1 (12.5)     11q23** 3 (5.6) 3 (6.5) 0 (0.0) Other abnormalities** 28 (51.9) 28 (60.9) 0 (0.0) Follow up (months)     Median/range 8.5/1~108 9.0/1~108 6.0/1~68     Died of disease 28 (46.7) 27 (52.9) 1 (11.1) DCL, donor cell leukemia; BM, bone marrow; BHSC, blood hematopoietic stem cells; UCB, umbilical cord blood; AML, acute myeloid leukemia; MDS, myelodysplastic syndrome; ALL, acute lymphoblastic leukemia (including B-cell and T-cell ALL); T-LGL, T-cell large granular lymphocyte leukemia; CLL, chronic lymphocytic leukemia. All the numbers represent the cases with data available. * One case of myeloproliferative neoplasm is included in this category. ** The percentage is calculated using number of total cytogenetic abnormalities in each column as denominator. Disclosures: No relevant conflicts of interest to declare.

Description: Liver injury associated with veno-occlusive disease and graft-versus-host disease (GVHD) is a frequent and severe complication of hematopoietic stem cell transplantation, and remains an important cause of transplant-related mortality. Bone marrow derived mesenchymal stem cells (MSCs) have been evaluated for the prevention and treatment of refractory GVHD. However, poor cell viability has limited the therapeutic capacity of mesenchymal stromal cell therapy in vivo. In this study, we genetically engineered C57BL/6 mouse bone marrow MSCs using ex vivo retroviral transduction to overexpress Akt1, a serine threonine kinase and pro-survival signal protein, and tested the hypothesis that Akt1-expressing MSCs (Akt1-MSCs) are more resistant to apoptosis and can ameliorate acute liver injury induced by concanavalin A (ConA) in BALB/c mice. Cell proliferation and apoptosis analyses showed that, under both regular culture and high concentration IFN-γ (100 ng/mL) stimulation conditions, Akt1-GFP-MSCs had proliferation and survival (anti-apoptotic) advantages with down-regulated apoptosis pathways, compared to control GFP-MSCs. Twenty-four hours after receiving lethal dose of ConA (40 mg/kg, intravenous) (N=10 each group), no mouse survived, with or without 1x106 Akt1-MSCs or GFP-MSCs administration (intravenous); however, 3 and 1 survived in the 5×106 Akt1-MSCs group and 5×106 GFP-MSCs groups, respectively. In subsequent sub-lethal dose ConA (20 mg/kg) experiments, compared to GFP-MSCs, mice received Akt1-MSCs administration had significantly lower serum AST, ALT, TNF-α and IFN-γ levels and less histopathological abnormalities. In addition, Akt1-MSCs treated mice had significantly higher serum concentrations of IL-10, vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). In vivo imaging showed that, hepatic fluorescence signal in sub-lethal ConA+Akt1-MSCs group was significantly stronger than ConA+GFP-MSCs group on day 0, and persisted up to 14 days, whereas the signal in ConA+GFP-MSCs, Akt1-MSCs and GFP-MSCs groups was negligible on both day 7 and day 14. Thus, bone marrow derived MSCs genetically enhanced with Akt1 had survival advantage in vitro and in vivo, and have the potential to be a potent therapy for prevention and amelioration of GVHD-associated liver impairment. Further translational pre-clinical studies are ongoing to further determine the efficacy, dosage and timing of administration of Akt1-MSCs in animal models. Disclosures No relevant conflicts of interest to declare.

Description: Background Sensitive and high throughput molecular detection assays are essential during the coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The vast majority of the SARS-CoV-2 molecular assays use nasopharyngeal swab (NPS) or oropharyngeal swab (OPS) specimens collected from suspected individuals. However, using NPS or OPS as specimens has apparent drawbacks, e.g. the collection procedures for NPS or OPS specimens can be uncomfortable to some people and may cause sneezing and coughing which in turn generate droplets and/or aerosol particles that are of risk to healthcare workers, requiring heavy use of personal protective equipment. There have been recent studies indicating that self-collected saliva specimens can be used for molecular detection of SARS-CoV-2 and provides more comfort and ease of use for the patients. Here we report the performance of QuantiVirus™ SARS-CoV-2 test using saliva as the testing specimens with or without pooling. Methods Development and validation studies were conducted following FDA-EUA and molecular assay validation guidelines. Using SeraCare Accuplex SARS-CoV-2 reference panel, the limit of detection (LOD) and clinical performance studies were performed with the QuantiVirus™ SARS-CoV-2 test. For clinical evaluation, 85 known positive and 90 known negative clinical NPS samples were tested. Additionally, twenty paired NPS and saliva samples collected from recovering COVID-19 patients were tested and the results were further compared to that of the Abbott m2000 SARS-CoV-2 PCR assay. Results of community collected 389 saliva samples for COVID-19 screening by QuantiVirus™ SARS-CoV-2 test were also obtained and analyzed. Additionally, testing of pooled saliva samples was evaluated. Results The LOD for the QuantiVirus™ SARS-CoV-2 test was confirmed to be 100–200 copies/mL. The clinical performance studies using contrived saliva samples indicated that the positive percentage agreement (PPA) of the QuantiVirus™ SARS-CoV-2 test is 100% at 1xLOD, 1.5xLOD and 2.5xLOD. No cross-reactivity was observed for the QuantiVirus™ SARS-CoV-2 test with common respiratory pathogens. Testing of clinical samples showed a positive percentage agreement (PPA) of 100% (95% CI: 94.6% to 100%) and a negative percentage agreement (NPA) of 98.9% (95% CI: 93.1% to 99.9%). QuantiVirus™ SARS CoV-2 test had 80% concordance rate and no significant difference (p = 0.13) between paired saliva and NPS specimens by Wilcoxon matched pairs signed rank test. Positive test rate was 1.79% for 389 saliva specimens collected from local communities for COVID-19 screening. Preliminary data showed that saliva sample pooling up to 6 samples (1:6 pooling) for SARS-CoV-2 detection is feasible (sensitivity 94.8% and specificity 100%). Conclusion The studies demonstrated that the QuantiVirus™ SARS-CoV-2 test has a LOD of 200 copies/mL in contrived saliva samples. The clinical performance of saliva-based testing is comparable to that of NPS-based testing. Pooling of saliva specimens for SARS-CoV-2 detection is feasible. Saliva based and high-throughput QuantiVirus™ SARS-CoV-2 test offers a highly desirable testing platform during the ongoing COVID-19 pandemic.