Rapid, Point-of-Care scFv-SERS Assay for Femtogram Level Detection of SARS-CoV-2.

Rapid, sensitive, on-site identification of SARS-CoV-2 infections is an important tool in the control and management of COVID-19. We have developed a surface-enhanced Raman scattering (SERS) immunoassay for highly sensitive detection of SARS-CoV-2. Single-chain Fv (scFv) recombinant antibody fragments that bind the SARS-CoV-2 spike protein were isolated by biopanning a human scFv library. ScFvs were conjugated to magnetic nanoparticles and SERS nanotags, followed by immunocomplex formation and detection of the SARS-CoV-2 spike protein with a limit of detection of 257 fg/mL in 30 min in viral transport medium. The assay also detected B.1.1.7 ("alpha"), B.1.351 ("beta"), and B.1.617.2 ("delta") spike proteins, while no cross-reactivity was observed with the common human coronavirus HKU1 spike protein. Inactivated whole SARS-CoV-2 virus was detected at 4.1 × 104 genomes/mL, which was 10-100-fold lower than virus loads typical of infectious individuals. The assay exhibited higher sensitivity for SARS-CoV-2 than commercial lateral flow assays, was compatible with viral transport media and saliva, enabled rapid pivoting to detect new virus variants, and facilitated highly sensitive, point-of-care diagnosis of COVID-19 in clinical and public health settings.

Prevalence of NPHS2 gene R229Q polymorphism in Bangladeshi children with nephrotic syndrome.

BACKGROUND: Limited and contradictory pharmacogenetic studies of NPHS2 gene R229Q polymorphism in nephrotic syndrome (NS) children of different ethnicities steered us to investigate the genotype frequency and associated risk of this polymorphism in Bangladeshi NS children. METHODS: A prospective case-control study was conducted which comprised a total of 142 children having nephrotic syndrome (NS), divided into 2 groups: case group consisted of 40 children with steroid-resistant nephrotic syndrome (SRNS), and control group involved 102 children with steroid-sensitive nephrotic syndrome (SSNS). Both were genotyped by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method for R229Q polymorphism. RESULTS: The results indicate the presence of R229Q polymorphism in 27.50% of SRNS and 12.75% of SSNS children. SRNS children possess 2.94-fold greater risk (p = 0.025) of carrying Arg/Gln genotype compared to SSNS children. Moreover, R229Q variant in SRNS children was observed as in a compound heterozygous form with p.Ala297Val located in exon 8. Age of onset (4-6 years) presents as a significant contributing factor (adjusted OR = 1.06; 95% CI = 1.023-1.094; p = 0.001) for SRNS susceptibility in Bangladeshi children. Contrarily, though the incidence of SRNS was higher in male children than female (80% vs 20%), gender remains to be a neutral factor (p = 0.257) in relation to SRNS susceptibility. CONCLUSION: Compound heterozygosity of NPHS2 p.R229Q gene variant with p.Ala297Val may cause pathogenic SRNS in Bangladeshi children. Large scale studies are warranted to establish the genotype-phenotype correlation. It is recommended to screen for p.R229Q first and, if positive, for p.Ala297Val in Bangladeshi SRNS children.