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Background Florfenicol (FF) is a chloramphenicol analogue used in animals, and florfenicol amine (FFA) is the main metabolite of FF. However, their residues in agricultural products are harmful to human health. A highly specific and sensitive assay for FF/FFA detection needs to be developed since the traditional detection methods are low in sensitivity. Objective In this study, a new method for rapid quantification of FF/FFA in poultry eggs by helper antibody-based fluorescent immunochromatographic assay (HAFIA) was established. Methods Triple antibodies including a primary monoclonal antibody (mAb) specific to the targets FF and FFA, a secondary polyclonal antibody (pAb) labeled with europium nanoparticles (EuNPs), and a helper monoclonal antibody (hAb), reacting with pAb but not with the mAb or the target antigen, are designed, which can form structural aggregation complexes in microwells with a single step of reactions. By loading the reaction sample solution, the triple-antibodies (mAb–pAb–hAb)–EuNPs complexes migrate to the test (T) line on the nitrocellulose membrane of testing strip and are competitively captured by the immobilized FF–bovine serum album (BSA) conjugates on the membrane and the FF/FFA targets in the sample solution. Results Fluorescence on the T line is read by a portable fluorescent strip reader in 10 min, and the result is given as the ratio of fluorescent intensities on the T and control (C) lines. This new fluorescent testing strip, with amplified signal from the triple-antibody complex, has 50-fold higher sensitivity than conventional colloidal gold-lateral flow immunoassays (CG-LFIAs), and can detect as low as 0.01 ng/mL FF and 0.1 ng/mL FFA targets from egg samples. Conclusion The developed competitive fluorescent immunochromatography method based on auxiliary antibodies has the advantages of high sensitivity and specificity for the rapid and quantitative detection of FF/FFA in poultry eggs. Highlights Newly designed helper antibody and portable device were applied to quantitative detection. HAFIA tests egg samples and results can be obtained in 10 minutes. HAFIA has the advantages of being more convenient, faster and does not require professional laboratory personnel.

To control the coronavirus disease 2019 (COVID-19) pandemic, there is an urgent need for simple, rapid, and reliable detection methods to identify severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, especially in community hospitals or clinical centers. The SARS-CoV-2 nucleocapsid protein (NP) is an important index for diagnosis of COVID-19. Here, we proposed a smartphone-based high-throughput fiber-integrated immunosensing system (HFIS) for detecting the SARS-CoV-2 NP in serum samples within 45 min. For the testing of NP standards, the linear detection range was 7.8-1000 pg/mL, the limit of detection was 7.5 pg/mL, and the cut-off value was 8.923 pg/mL. Twenty-five serum samples from clinically diagnosed COVID-19 patients and 100 negative control samples from healthy blood donors were tested for SARS-CoV-2 NP by HFIS, and the obtained results were compared with those of ELISA and Simple Western analysis. The results showed that the HFIS sensitivity and specificity were 72% [95% confidence interval (CI): 52.42-85.72%] and 100% (95% CI: 96.11-100%), respectively, which significantly correlated with those from the commercial ELISA kit and Simple Western analysis. This portable high-throughput HFIS assay could be an alternative test for detecting SARS-CoV-2 NP in blood samples on site.

Adenoviral vectors have been widely used for the development of infectious disease vaccines. However, the challenge of human adenoviral vector rooted from the predominant adenovirus serotype 5 strain limiting its usefulness by the widespread pre-existing neutralizing antibodies in recipients. To circumvent this obstacle, we generated an ad-hoc adenovirus vector in human or primates. Here, a chimeric simian adenoviral vector Sad23 was constructed consisting in deleting of E1 and E3 regions of the full-length simian adenovirus serotype 23 genome (SAdV23) by Gibson assembly. To improve Sad23 virus propagating efficiency, the E4 region open reading frame 6 (orf6) was replaced by the corresponding element of human adenovirus type 5 (Ad5), designated Sad23L. The procedure for cloning this novel vector took a single week, and recombinant adenovirus was packaged with high titer in HEK293 cells. To verify the ability of this novel adenoviral vector to deliver foreign genes, Zika virus (ZIKV) prM-E genes were used as target genes for antigen expression. Recombinant adenoviruses Sad23L-prM-E, Sad23-prM-E and Ad5-prM-E were intramuscularly inoculated into Ad5-eGFP none pre-exposed or pre-exposed mice, and the immune response to ZIKV prM-E was compared between vectors. Sad23L-prM-E induced a fairly robust immune response and maintained immunogenicity in Ad5 pre-exposed mice, which suggested that Ad5 pre-existing immunity did not affect Sad23L-prM-E immunization. These preliminary results suggest that the proposed rapid strategy was effective in constructing a new adenoviral vector platform (Sad23 L) usable for the development of human vaccines.

In this paper, we make an investigation on the sum-mean-square-error (Sum-MSE) performance gain in full-duplex orthogonal frequency-division multiplexing (OFDM) systems in the presence of colored interference-plus-noise (IPN). This gain is defined as the ratio of Sum-MSE of frequency-domain least-square (LS) channel estimator to that of DFT-based LS one. The closed-form formula of the gain is derived. And, its simple upper and lower bounds are given using inequalities of matrix eigenvalues. The exact value of Sum-MSE gain depends heavily on the correlation factor of the IPN covariance matrix. More importantly, we also find that the Sum-MSE performance gain grows from 1 to $N/L$ as the correlation factor gradually decreases from 1 to 0, where $N$ and $L$ denote the number of total subcarrier and the length of cyclic prefix, respectively. Also, via theoretical analysis, the exact Sum-MSE gain degenerates into 1 and $N/L$ in two extreme scenarios: fully-correlated and white, respectively. The former 1 means there is no performance gain, while the latter $N/L$ corresponds to the maximum Sum-MSE performance gain achievable. Numerical simulation further validates the above results. Additionally, the derived lower bound is shown to be closer to the exact value of Sum-MSE gain compared to the upper bound.

In this paper, the problem of content caching in 5G cellular networks relying on social-aware device-to-device communications (DTD) is investigated. Our focus is on how to efficiently select important users (IUs) and how to allocate content files to the storage of these selected IUs to form a distributed caching system. We aim at proposing a novel approach for minimizing the downloading latency and maximizing the social welfare simultaneously. In particular, we first model the problem of maximizing the social welfare as a many-to-one matching game based on the social property of mobile users. We study this game by exploiting users’ social properties to generate the utility functions of the two-side players, i.e., content providers (CPs) and IUs. Then we model the problem of minimizing the downloading latency as a many-to-many matching problem. For solving these games, we design a many-to-one IU selection (MOIS) matching algorithm and a many-to-many file allocation (MMFA) matching algorithm, respectively. Simulation and analytical results show that the proposed mechanisms are stable, and are capable of offering a better performance than other benchmarks in terms of social welfare and network downloading latency.

Background & Aims Occult HBV infection (OBI) is associated with transfusion-transmitted HBV infection and hepatocellular carcinoma. Studies on OBI genesis have concentrated on mutations in the S region and the regulatory elements. Herein, we aimed to determine the role of mutations in the core region on OBIs. Methods An OBI strain (SZA) carrying 9 amino acid (aa) substitutions in the core protein/capsid (Cp) was selected by sequence alignment and Western blot analysis from 26 genotype B OBI samples to extensively explore the impact of Cp mutations on viral antigen production in vitro and in vivo. Results A large panel of 30 Cp replicons were generated by a replication-competent pHBV1.3 carrying SZA or wild-type (WT) Cp in a 1.3-fold over-length of HBV genome, in which the various Cp mutants were individually introduced by repairing site mutations of SZA-Cp or creating site mutations of WT-Cp by site-directed mutagenesis. The expression of HBcAg, HBeAg, and HBsAg and viral RNA was quantified from individual SZA and WT Cp mutant replicons in transfected Huh7 cells or infected mice, respectively. An analysis of the effect of Cp mutants on intracellular or extracellular viral protein production indicated that the W62R mutation in Cp had a critical impact on the reduction of HBcAg and HBeAg production during HBV replication, whereas P50H and/or S74G mutations played a limited role in influencing viral protein production in vivo. Conclusions W62R and its combination mutations in HBV Cp might massively affect HBcAg and HBeAg production during viral replication, which, in turn, might contribute to the occurrence of OBI. Lay summary Occult hepatitis B virus infections (OBIs) have been found to be associated with amino acid mutations in the S region of the HBV, but the role of mutations in the core protein (Cp) remains unclear. In this study, an OBI strain (SZA) carrying 9 amino acid substitutions in Cp has been examined comprehensively in vitro and in vivo. The W62R mutation in Cp majorly reduces HBcAg and HBeAg production during HBV replication, potentially contributing to the occurrence of OBI.

Brucellosis is a worldwide infectious zoonotic disease, posing severe threats to human health and social-economic development. By comparing with time-consuming, low sensitive and non-quantitative conventional serological methods, herein, protein G (prG) coupled with europium nanospheres (EuNPs) (detection probe) and highly purified Brucella lipopolysaccharide (LPS) (capture antigen) were used to develop a novel time-resolved fluorescence lateral flow immunoassay (TF-LFIA) for detecting anti-Brucella IgG antibody in human plasmas. The entire testing took 15 min. With a satisfactory purity, the purified LPS weakly cross-reacted with Y. enterocolitica O9 diagnostic antibody; however, none reacted with sera from patients with other Gram-negative bacterial infections. Following coefficient of determination (R2 = 0.9961), 0.3 IU/mL was reported as the limit of detection (LOD), much lower than those of Serological Agglutination Test (SAT), Rose-Bengal Plate Agglutination Test (RBPT) and colloidal gold LFIA (CG-LFIA). Intra-day and inter-day precisions (CV, coefficient variation) of TF-LFIA varied less than 8% or 12 %, while intra-day and inter-day accuracies were 94–106 % or 93–107 %, respectively. The correlation coefficient (R2) of TF-LFIA measurement to the different concentrations of spiked Brucella antibody was 0.9967, suggesting TF-LFIA had high reliability and reproducibility. TF-LFIA was demonstrated for 100 % specificity, 98.57 % sensitivity and 99.63 % accuracy in detection of Brucella antibody from clinical samples, respectively, significantly higher compared to SAT and RBPT. In conclusion, the established TF-LFIA is a simple, rapid and quantitative immunoassay for early diagnosis or epidemiological surveillance of Brucella infection in humans.

BackgroundSince December 2019, the outbreak of coronavirus disease (COVID-19) has been occurred by novel coronavirus (SARS-CoV-2). The rapid and sensitive immunoassays are urgently demanded for detecting specific antibodies as assistant diagnosis for primary screening of asymptomatic individuals, close contacts, suspected or recovered patients of COIVD-19 during the pandemic period.MethodsThe recombinant receptor binding domain of SARS-CoV-2 spike protein (S-RBD) was used as the antigen to detect specific IgM and the mixture of recombinant nucleocapsid phosphoprotein (NP) and S-RBD were used to detect specific IgG by the newly designed quantum-dot lateral flow immunoassay strip (QD-LFIA), respectively.ResultsA rapid and sensitive QD-LFIA based portable fluorescence smart-phone system was developed for detecting specific IgM/IgG to SARS-CoV-2 from 100 serum samples of COVID-19 patients and 450 plasma samples from healthy blood donors. Among 100 COVID-19 patients diagnosed with NAT previously, 3 were severe, 35 mild and 62 recovered cases. By using QD-LFIA, 78 (78%) and 99 (99%) samples from 100 COVID-19 patients’ serum were detected positive for anti-SARS-CoV-2 IgM or IgG, respectively, but only one sample (0.22%) was cross-reactive with S-RBD from 450 healthy blood donor plasmas that were collected from different areas of China.ConclusionAn ultrasensitive and specific QD-LFIA based portable fluorescence smart-phone system was developed fo r detection of specific IgM and IgG to SARS-CoV-2 infection, which could be used for investigating the prevalence or assistant diagnosis of COVID-19 in humans.