Characterizing a visual lateral flow device for rapid SARS-CoV-2 virus protein detection: pre-clinical and system assessment.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infections have affected more than 769 million individuals worldwide over the last few years. Although the pandemic is transitioning into an endemic, the COVID-19 outbreak is still a global concern. A rapid screening platform is needed for effective preventive and control measures. Herein, a visual rapid lateral flow platform for SARS-CoV-2 nucleocapsid protein detection is developed. Under optimal conditions, the system demonstrated good detection sensitivity and selectivity against tested respiratory viruses. The system provides direct visual detection with a limit of 0.7 ng of the nucleocapsid protein per mL of a sample (0.7 ng mL-1) within 15 minutes. Further, a correlation between direct visual detection and semi-quantitative analysis using a reader showed a similar detection limit (R2 = 0.9571). The repeatability and reproducibility studies highlighted the potential of the system for the rapid screening of SARS-CoV-2 infection, with variations within 5% and 10% at high and low protein concentrations, respectively. Subsequent pre-clinical validation to correlate the performance with the standard molecular approach (RT-PCR) using 170 nasopharyngeal swabs demonstrated 98% estimated sensitivity (95% CI, 89.35-99.95%) and 100% specificity (95% CI, 96.38-100%). The positive and negative predictive values were reported to be 100% and 99%, respectively, with an accuracy of 99.3%. With high viral load samples (Ct value ≤25, n = 47), the system demonstrated 100% detection sensitivity and specificity. The proposed technique provides a valuable platform for potential use in rapid screening, particularly during pandemics, where diagnostic capacity and mass screening are crucial.

Seroprevalence of hepatitis E virus after pediatric liver transplantation.

BACKGROUND: Southeast Asia is the endemic area of hepatitis E virus (HEV) infection. We aimed to determine the seroprevalence of the virus, its association, and the prevalence of chronic infection after pediatric liver transplantation (LT). METHODS: A cross-sectional study was performed in Bangkok, Thailand. Patients aged <18 years who had LT for >2 years underwent serologic and real-time polymerase chain reaction (rt-PCR) tests. Acute HEV infection was defined by the presence of positive anti-HEV immunoglobulin (Ig)M and HEV viremia from the rt-PCR. If the viremia persisted for >6 months, chronic HEV infection was diagnosed. RESULTS: A total of 101 patients had a median age of 8.4 years [interqartile range (IQR): 5.8-11.7]. The seroprevalence of anti-HEV IgG and IgM was 15% and 4%, respectively. Positive IgM and/or IgG were associated with a history of elevated transaminases with an unknown cause after LT (p = 0.04 and p = 0.01, respectively). The presence of HEV IgM was associated with a history of elevated transaminases with an unknown cause within 6 months (p = 0.01). The two patients (2%) diagnosed with chronic HEV infection did not fully respond to the reduction of immunosuppression but responded well to ribavirin treatment. CONCLUSIONS: Seroprevalence of HEV among pediatric LT recipients was not rare in Southeast Asia. Since HEV seropositivity was associated with elevated transaminases of an unknown cause, investigation for the virus should be offered in LT children with hepatitis after excluding other etiologies. Pediatric LT recipients with chronic HEV infection may receive a benefit from a specific antiviral treatment.

Pre-clinically evaluated visual lateral flow platform using influenza A and B nucleoprotein as a model and its potential applications.

A visual colorimetric rapid screening system based on a lateral flow device for simultaneous detection and differentiation between influenza A and B nucleoprotein as a model was developed. Monoclonal antibodies, specific for either influenza A or B nucleoproteins, were evaluated for their reactivities and were used as targeting ligands. With the best antibody pairs selected, the system exhibited good specificity to both viruses without cross reactivity to other closely related respiratory viruses. Further semi-quantitative analysis using a strip reader revealed that the system is capable of detecting influenza A and B protein content as low as 0.04 and 1 ng per test, respectively, using a sample volume as low as 100 µL, within 10 minutes (R 2 = 0.9652 and 0.9718). With a performance comparison to the commercial tests, the system demonstrated a four-to-eight-fold higher sensitivity. Pre-clinical evaluation with 101 nasopharyngeal swabs reveals correlated results with a standard molecular approach, with 89% and 83% sensitivity towards influenza A and B viruses, and 100% specificity for both viruses.

Listeria monocytogenes MerR-Like Regulator NmlRlm: Its Transcriptome and Role in Stress Response.

NmlR, a negative transcription regulator in the MerR family, is involved in oxidative and nitrosative stress response in Neisseria gonorrhoeae and Haemophilus influenzae. In this study, the objective was to characterize the role and the regulon of NmlR in the foodborne Listeria monocytogenes. An L. monocytogenes nmlR null mutant strain was constructed. Transcriptomes of strain 10403S wild type (WT) and ΔnmlRlm strains grown to the stationary phase were determined by mRNA sequencing. Differential expression analyses revealed 74 genes with altered expression levels (>9-fold difference), comprising 46 negatively and 28 positively regulated genes. Twenty-four NmlRlm-dependent genes overlap with the members of previously identified regulons of HrcA, a negative regulator of heat response in L. monocytogenes, and of alternative sigma factor σ(H). Phenotypic characterization revealed that the ΔnmlRlm strain survived significantly less than the WT under acid stress (pH 2.5 for 1 h) and oxidative stress (3% hydrogen peroxide for 1 h). In addition, nmlRlm deletion also resulted in a significant decrease (p < 0.0005) of cell length and enhanced intracellular growth in a differentiated macrophage-like U937 cell line during entry into stationary phase. These findings indicate that NmlRlm is not only involved in oxidative stress response but also contributes to other characteristics such as acid tolerance and intracellular growth, either through direct regulation or co-regulation with other regulators such as HrcA and σ(H).