A CRISPR-based ultrasensitive assay redefines “undetectable” SARS-CoV-2 antibodies in kidney transplant recipients after COVID-19 vaccination (preprint)

An ultrasensitive assay for the detection of antibodies to SARS-CoV-2 is critically needed for evaluating the adaptive humoral immune response and infection rates in immunocompromised subpopulations. Here, we report an Ultrasensitive CRISPR-based Antibody Detection (UCAD) assay that translates the detection of serum antibodies against the receptor binding domain (RBD) of SARS-CoV-2 spike protein into CRISPR-based nucleic acid testing in a homogeneous solution and is thus 10,000 times more sensitive than the commercial immunoassay. The UCAD assay, which has been validated with 65 clinical anti-RBD-positive and 72 anti-RBD-negative sera collected from the general population, achieves 100% sensitivity and 97.2% specificity. We finally deployed UCAD to evaluate the levels of serum anti-RBD IgG and IgM in a cohort of 85 vaccinated kidney transplant recipients (KTRs), an especially vulnerable patient population with reported seroconversion rates of only 4-48%. Among the 85 vaccinated KTRs, UCAD successfully identified 68 seroconversion positive sera that were previously determined to contain “undetectable” levels of anti-SARS-CoV-2 using a clinical chemiluminescent immunoassay (CLIA) and has revealed significant differences in the levels of plasmablasts, type-2 T helper (Th2) cells, and type-17 T helper (Th17) cells between the UCAD-identified seroconversion positive and negative groups. As UCAD is a solution-based ultrasensitive assay that does not require specialized equipment or tedious operational and washing steps, we anticipate that it will find wide applications for clinical uses in both centralized laboratories and point-of-care settings.

A novel, anatomy-similar in vitro model of 3D airway epithelial for anti-coronavirus drug discovery (preprint)

SARS-CoV-2 and its induced COVID-19 remains as a global health calamity. Severe symptoms and high mortality, caused by cytokine storm and acute respiratory distress syndrome in the lower respiratory airway, are always associated with elderly individuals and those with comorbidities; whereas mild or moderate COVID-19 patients have limited upper respiratory flu-like symptoms. There is an urgent need to investigate SARS-CoV-2 and other coronaviruses replication and immune responses in human respiratory systems. The human reconstituted airway epithelial air-liquid interface (ALI) models are the most physiologically relevant model for the investigation of coronavirus infection and virus-triggered innate immune signatures. We established ALI models representing both the upper and the lower respiratory airway to characterize the coronavirus infection kinetics, tissue pathophysiology, and innate immune signatures from upper and lower respiratory tract perspective. Our data suggested these in vitro ALI models maintain high physiological relevance with human airway tissues. The coronavirus induced immune response observed in these upper and lower respiratory airway models are similar to what has been reported in COVID-19 patients. The antiviral efficacy results of a few promising anti-coronavirus drugs in these models were consistent with previous reports and could be valuable for the human dose prediction. Taken together, our study demonstrates the importance of 3D airway epithelial ALI model for the understanding of coronavirus pathogenesis and the discovery and development of anti-coronavirus drugs.

Investigation and analysis on characteristics of a cluster of COVID-19 associated with exposure in a department store in Tianjin / 中华流行病学杂志

Objective@#To describe the epidemiological characteristics of a cluster of COVID-19 cases reported in Baodi district of Tianjin as of 18 February, 2020, which might be associated with the exposure in a local department store, and provide suggestions for prevention and control strategy development.@* Methods@#The basic characteristics, time and area distributions, clinical manifestations, epidemiological history and transmission mode of the COVID-19 cases associated with the department store exposure were analyzed.@* Results@#A total of 40 COVID-19 cases were associated with the department store exposure, accounting for 75.47% of the total confirmed cases (53 cases) reported in Baodi district. The cases were mainly at the age of 60 years or older (35.00%) and farmers (40.00%). The main clinical manifestations included fever (95.00%), cough (35.00%), and diarrhea (15.00%). The proportion of confirmed severe cases was 32.50%. The incidence curve showed that the incidence peak occurred on 31 January, 2020. Among the 40 cases, 6(15.00%) were department store employees, 19(47.50%) were customers and 15(37.50%) were close contacts (secondary cases). The first case occurred on 21 January, 2020, this case was a department store employee who had a purchasing history at whole sale markets in other provinces and cities before the onset, and 3 employees were still on duty after symptom onsets. The median of the incubation period of customer cases was 6 days, and the median of the interval between onset and medical treatment of customer cases was 7 days.@* Conclusion@#This was a cluster epidemic of COVID-19, which might be associated with the exposure in the department store. By now, the current prevention and control measures have achieved satisfied effects.