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Although amyloid-β42 (Aβ42) has been used as one of the core biomarkers for Alzheimer’s disease (AD) diagnosis, the dynamic changes of its different forms in the brain, blood, and even intestines and its correlation with the progression of AD disease remain obscure. Herein, we screened Aβ42-specific preferred antibody pairs 1F12/1F12 and 1F12/2C6 to accurately detect Aβ42 types using sandwich ELISA, including total Aβ42, Aβ42 oligomers (Aβ42Os), and Aβ42 monomers (Aβ42Ms). The levels of Aβ42 species in the brain, blood, and intestines of different aged APP/PS1 mice were quantified to study their correlation with AD progression. Total Aβ42 levels in the blood were not correlated with AD progression, but Aβ42Ms level in the blood of 9-month-old APP/PS1 mice was significantly reduced, and Aβ42Os level in the brain was significantly elevated compared to 3-month-old APP/PS1, demonstrating that the levels of Aβ42Ms and Aβ42Os in the blood and brain were correlated with AD progression. Interestingly, in 9-month-old APP/PS1 mice, the level of Aβ42 in the intestine was higher than that in 3-month-old APP/PS1 mice, indicating that the increased level of Aβ42 in the gastrointestinal organs may also be related to the progression of AD. Meanwhile, changes in the gut microbiota composition of APP/PS1 mice with age were also observed. Therefore, the increase in Aβ derived from intestinal tissues and changes in microbiome composition can be used as a potential early diagnosis tool for AD, and further used as an indicator of drug intervention to reduce brain amyloid.

The anti-amyloid-β (anti-Aβ) fibrils and soluble oligomers antibody aducanumab were approved to effectively slow down the progression of Alzheimer’s disease (AD) at higher doses in 2019, reaffirming the therapeutic effects of targeting the core pathology of AD. A timely and accurate diagnosis in the prodromal or pre-dementia stage of AD is essential for patient recruitment, stratification, and monitoring of treatment effects. AD core biomarkers amyloid-β (Aβ1−42), total tau (t-tau), and phosphorylated tau (p-tau) have been clinically validated to reflect AD-type pathological changes through cerebrospinal fluid (CSF) measurement or positron-emission tomography (PET) and found to have high diagnostic performance for AD identification in the stage of mild cognitive impairment. The development of ultrasensitive immunoassay technology enables AD pathological proteins such as tau and neurofilament light (NFL) to be measured in blood samples. However, combined biomarker detection or targeting multiple biomarkers in immunoassays will increase detection sensitivity and specificity and improve diagnostic accuracy. This review summarizes and analyzes the performance of current detection methods for early diagnosis of AD, and provides a concept of detection method based on multiple biomarkers instead of a single target, which may become a potential tool for early diagnosis of AD in the future.

Background: Zika Virus (ZIKV) is a new type of flaviviruses transmitted by mosquitoes to cause severe diseases including Guillain-Barre syndrome and congenital malformations during recent outbreaks. The early diagnosis of ZIKV infection and efficient vaccines would be effective in controlling epidemics and timely treatment. However, the native nonstructural protein 1 (NS1) mainly acquired from cells infected with ZIKV, which largely limits its application. Objectives: This study aimed to express and purify the recombinant NS1 protein and prepare its antibody that efficiently reacted with the native NS1 protein secreted in the supernatant of ZIKV infected host-cells. Methods: We constructed a prokaryotic expression vector containing the full length of the NS1 gene. Thus, the recombinant NS1 protein was efficiently expressed and purified. The purified NS1 protein was used to prepare an antibody. The Enzyme-linked Immunosorbent Assay (ELISA), Western blot, and Indirect Immunofluorescent Assay (IFA) were used to assess the reactivity and specificity of the antibody. Results: The recombinant NS1 protein from a prokaryotic expression vector had good immunogenicity and the prepared antibody could specifically react with the native NS1 produced in Vero, BHK-21 cells infected with ZIKV. Besides, the ELISA and Western blot showed that the native ZIKV-NS1 protein was secreted extracellularly and could play the role of an early diagnostic biomarker for ZIKV infection. Conclusions: The prepared antibody against the recombinant NS1 protein is a reliable biological tool that enables the rapid and sensitive detection of secreted NS1 from host cells infected with ZIKV. The recombinant NS1 protein and its antibody can contribute to developing vaccines and antibodies targeting the NS1 protein to prevent flavivirus disease progression.

Salmonella, a common foodborne pathogen, causes many cases of foodborne illness and poses a threat to public health worldwide. Immunological detection systems can be combined with nanoparticles to develop sensitive and portable detection technologies for timely screening of Salmonella infections. Here, we developed an antibody-probe-based immuno-N-hydroxysuccinimide (NHS) bead (AIB) system to detect Salmonella. After adding the antibody probe, Salmonella accumulated in the samples on the surfaces of the immuno-NHS beads (INBs), forming a sandwich structure (INB&ndash, Salmonella&ndash, probes). We demonstrated the utility of our AIB diagnostic system for detecting Salmonella in water, milk, and eggs, with a sensitivity of 9 CFU mL&minus, 1 in less than 50 min. The AIB diagnostic system exhibits highly specific detection and no cross-reaction with other similar microbial strains. With no specialized equipment or technical requirements, the AIB diagnostic method can be used for visual, rapid, and point-of-care detection of Salmonella.

Background: Klebsiella pneumoniae is an important human pathogen that causes severe diseases including urinary tract infection, pneumonia, and bacteremia. However, a rapid and sensitive detection method remains to be developed. Objectives: This study aimed to develop a rapid, real-time, and visual detection method for K. pneumoniae. This is a primary screening method to improve the diagnosis of K. pneumoniae infection and save much precious time for clinical practice. Methods: Klebsiella pneumoniae was used as an antigen to produce a monoclonal antibodies (mAb). The mAb 1E6 recognizing outer membrane protein C on the surface of K. pneumoniae was screened by an indirect enzyme-linked immunosorbent assay (ELISA), Western Blot, and mass spectrometry assay, and then conjugated with the protein A/G coated magnetic beads to generate the immune magnetic beads (IMBs). Thereafter, the IMBs were used to capture K. pneumoniae, and the complex (beads-mAb-K. pneumoniae) was used for loop-mediated isothermal amplification (LAMP) assay. Results: We developed a rapid, real-time, and visual detection method employing an immunocapture loop-mediated isothermal amplification (IC-LAMP). The sensitivity of the IC-LAMP was 4 CFU mL-1. The process of K. pneumoniae detection lasted ~ 60 minutes and had no cross-reaction to other microbial strains. Besides, the accuracy of IC-LAMP was further verified by examining 39 clinical isolates. Conclusions: Without the need for enrichment of bacteria and extraction of its genome, the IC-LAMP developed here could be used as a primary screening method supplementary to traditional detection methods to improve the diagnosis of K. pneumoniae infection for clinical practice.

Background: The outbreak of Zika virus (ZIKV) in many countries caused alarming numbers of babies born with microcephalus and severe neurologic disorders, however, the methods for the detection of the ZIKV are limited at present. Objectives: The aim of this study was to produce polyclonal antibody against full length envelop protein of ZIKV (ZIKV-E protein) in prokaryotic system and to evaluate its efficacy to capture ZIKV virion. Methods: The recombinant full length ZIKV-E protein was purified and then used as an immunogen to vaccinate BALB/c mice to produce polyclonal antibody. Protein A/G coated magnetic beads were coated with the polyclonal antibody to capture the ZIKV virion in the culture medium of Vero cells infected with ZIKV. The products of immunoprecipitation were further used for Western Blot, Loop-mediated isothermal amplification (LAMP), and PCR assay. Results: Western Blot and indirect immunofluorescence analysis showed that the mouse polyclonal antibody could react specifically with the native E protein in Vero cells infected with ZIKV. The results of Western Blot, Immunocaptured-LAMP (IC-LAMP), and Immunocaptured-PCR (IC-PCR) showed that polyclonal antibody of ZIKV-E recombinant protein can capture ZIKV virion specifically, however, the polyclonal antibody against the ZIKV-NS1, Shigella, and Salmonella without such a function. Conclusions: These findings may provide the basis for the development of the rapid diagnostic kits such as, IC-PCR, IC-LAMP, and sandwich ELISA. The serum virion capture activity elicited by prokaryotic expressed recombinant ZIKV-E protein may also provide a basis for further preparation of neutralizing antibody and protein subunit vaccine candidate against ZIKV.

Zika virus (ZIKV) is an emerging mosquito-transmitted flavivirus that can cause severe disease, including congenital birth defect and Guillain&minus, Barr&eacute, syndrome during pregnancy. Although, several molecular diagnostic methods have been developed to detect the ZIKV, these methods pose challenges as they cannot detect early viral infection. Furthermore, these methods require the extraction of RNA, which is easy to contaminate. Nonstructural protein 1 (NS1) is an important biomarker for early diagnosis of the virus, and the detection methods associated with the NS1 protein have recently been reported. The aim of this study was to develop a rapid and sensitive detection method for the detection of the ZIKV based on the NS1 protein. The sensitivity of this method is 120 ng mL&minus, 1 and it detected the ZIKV in the supernatant and lysates of Vero and BHK cells, as well as the sera of tree shrews infected with the ZIKV. Without the isolation of the virus and the extraction of the RNA, our method can be used as a primary screening test as opposed to other diagnosis methods that detect the ZIKV.