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Group A Streptococcus (GAS), a major pathogen, causes various respiratory diseases with substantial morbidity and mortality worldwide. In this study, we develop an immunoassay for the early screening and diagnosis of GAS infections. A latex beads-based lateral flow immunoassay (LBs-LFIA) and a fluorescent beads-based LFIA (FBs-LFIA) using an antibody cocktail that was coated on the test line (T line), the limit of detection (LoD) of LBs-LFIA was 105 CFU mL−1 and FBs-LFIA was 103 CFU mL−1. Furthermore, the use of the antibody cocktail led to the detection of the various epidemic clinical types of GAS with high sensitivity (100%) and specificity (＞95%). To devise a point-of-care testing (POCT) platform for mass screening in low-resource areas, a mobile phone-based portable strip reader capable of visually interpreting the results was developed and the LoD of LBs-LFIA and FBs-LFIA were calculated as 104 CFU mL−1 and 102 CFU mL−1, respectively. Taken together, we suggest that the developed LBs-LFIA and FBs-LFIA using the antibody cocktail can be used for the clinical emergency detection of GAS infections. [Display omitted] • The strategy of antibody cocktail was firstly used to immunodetection of GAS. • A mobile phone-based portable device was designed for reading GAS LFIA. • The two LFIAs can be used to detect different subtypes of GAS. • The two LFIAs were able to detect the presence of GAS in throat swab samples. [ABSTRACT FROM AUTHOR]

The number of CD8+ T lymphocytes (CD8 cells) in peripheral blood can directly reflect the immune status of the body and is widely used for auxiliary diagnosis and prognostic evaluation of diseases. There is an urgent need to develop a simple CD8 cell-counting platform to meet clinical needs. Our group designed a paper-based cell-counting method based on a blocking competition strategy. In addition, we developed a time-resolved fluorescence-blocking competitive lateral flow immunoassay (TRF-BCLFIA) for point-of-care CD8 cell counting that functions by measuring europium nanoparticle (EuNP)-labeled CD8 antibody probes that are not captured by CD8 cells, and we indirectly calculated the concentration of CD8 cells in samples. Within 30 min, four operation steps can provide an accurate CD8 cell count for a 75-μL whole-blood sample, and this approach can be implemented on a handheld device. The TRF-BCLFIA reliably quantified CD8 cells in whole-blood samples, in which the assay exhibited a linear correlation (R2 = 0.989) readout for CD8 cell concentrations ranging from 137 to 821 cells/μL. To validate this approach, our newly developed CD8 cell-counting tool was used to assess 33 tumor patient blood samples. The results showed a high consistency with a flow cytometry-based absolute count. This analysis approach is a promising alternative for the costly standard flow cytometry-based tools for CD8 cell counting in tumor patients in community clinics, small hospitals, and low medical resource regions. This technology would deliver simple diagnostics to patients anywhere in the world, regardless of geography or socioeconomic status. [Display omitted] • We developed a CD8 cell-counting tool that called time-resolved fluorescence-blocking competitive lateral flow immunoassay. • The probes labeled CD8 antibody was europium nanoparticle (EuNP). • Within 30 min, the TRF-BCLFIA reliably quantified CD8 cells in whole-blood samples with a good a linear correlation. • The TRF-BCLFIA showed a high consistency with a flow cytometry-based absolute count. [ABSTRACT FROM AUTHOR]

Vaccination is an effective strategy to fight COVID-19. However, the effectiveness of the vaccine varies among different populations in varying immune effects. Neutralizing antibody (NAb) level is an important indicator to evaluate the protective effect of immune response after vaccination. Lateral flow immunoassay (LFIA) is a rapid, safe and sensitivity detection method, which has great potential in the detection of SARS-CoV-2 NAb. In this study, a fluorescent beads-based lateral flow immunoassay (FBs-LFIA) and a latex beads-based LFIA (LBs-LFIA) using double antigen sandwich (DAS) strategy were established to detect NAbs in the serum of vaccinated people. The limit of detection (LoD) of the FBs-LFIA was 1.13 ng mL− 1 and the LBs-LFIA was 7.11 ng mL− 1. The two LFIAs were no cross-reactive with sera infected by other pathogenic bacteria. Furthermore, the two LFIAs showed a good performance in testing clinical samples. The sensitivity of FBs-LFIA and LBs-LFIA were 97.44% (95%CI: 93.15%–99.18%) and 98.29% (95%CI: 95.84%–99.37%), and the specificity were 98.28% (95%CI: 95.37%–99.45%) and 97.70% (95%CI: 94.82%–99.06%) compared with the conventional virus neutralization test (cVNT), respectively. Notably, the LBs-LFIA was also suitable for whole blood sample, requiring only 3 μL of whole blood, which provided the possibility to detect NAbs at home. To sum up, the two LFIAs based on double antigen sandwich established by us can rapidly, safely, sensitively and accurately detect SARS-CoV-2 NAb in human serum. [Display omitted] • LFIAs based on double antigen sandwich (DAS) have high sensitivity and specificity compared with cVNT. • The FBs-LFIA achieves a sensitivity of 97.44% and specificity of 98.28% in testing clinical serum samples (n = 389). • The LBs-LFIA achieves a sensitivity of 98.29% and a specificity of 97.70% in testing clinical serum samples (n = 554). • The LBs-LFIA can be used to plasma, serum and whole blood samples so it's suitable for home self-test and community hospital. [ABSTRACT FROM AUTHOR]

A novel time-resolved fluorescence blocking lateral flow immunoassay (TRF-BLFIA) was developed for on-site differential diagnosis of pseudorabies virus (PRV)-infected and vaccinated pigs using europium nanoparticles (EuNPs)-labeled virion antigens and high titer PRV gE monoclonal antibodies (PRV gE-mAb). Upon application of a positive serum sample, the specific epitopes of gE protein on the EuNPs-PRV probe were blocked, inhibiting binding to the PRV gE-mAb on the T line, resulting in low or negligible fluorescence signal, whereas when a negative sample was applied, EuNPs-PRV probes would be able to bind the antibody at the T line, leading to high fluorescence signal. Under optimized conditions, TRF-BLFIA provided excellent sensitivity and selectivity. When testing swine clinical samples (n = 356), there was 96.1% agreement between this method and a most widely used commercial gE-ELISA kit. Moreover, our method was rapid (15 min), cost-efficient and easy to operate with simple training, allowing for on-site detection. Thus, TRF-BLFIA could be a practical tool to differentially diagnose PRV-infected and vaccinated pigs. • A time-resolved fluorescence blocking lateral flow immunoassay based on EuNPs-virus antigen probe was first developed. • TRF-BLFIA has excellent clinical applicability in the on-site differential diagnosis of PRV-infected and vaccinated pigs. • The TRF-BLFIA has advantages of simplicity, sensitivity, specificity and rapidity. [ABSTRACT FROM AUTHOR]