New sensitive competitive enzyme-linked immunosorbent assay using a monoclonal antibody against nonstructural protein 1 of West Nile virus NY99

Structural elucidation of Tsukamurella pulmonis neutral polysaccharide and its visualization in infected mouse tissues by specific monoclonal antibodies

Tsukamurella pulmonis is an opportunistic actinomycetal pathogen associated with a variety of rarely diagnosed human infections. In clinical cases of infection, T. pulmonis usually accompanies other bacterial pathogens. Because of these mixed infections, a robust diagnostic assay is important. The bacteria cell surface polysaccharides are considered not only useful targets for diagnostics but also intriguing subjects for analysis of the interactions that regulate the host response in general. Here, the structure of the polysaccharide component of the T. pulmonis cell wall was established. Sugar and methylation analysis and 2D-NMR techniques revealed that its polysaccharide belongs to the class of arabinomannan composed of branched tetrasaccharide repeating units, with addition of linear →6)-α-D-Manp-(1→ mannan. Rabbit polyclonal sera against T. pulmonis and T. paurometabola bacterial cells revealed cross reactivity between their antigens. Tissue samples from mice infected with T. pulmonis revealed liver abscesses and pathologic granules located intracellularly when immunohistochemically stained with monoclonal antibodies raised against T. pulmonis polysaccharide. Ultrastructural studies revealed that these granules contain T. pulmonis cells. These observations indicate that T. pulmonis is a pathogenic species capable of spreading within the organism, presumably through the blood.

Non-neutralizing Antibody Responses against VP1 in Enterovirus A, B, C and Rhinovirus A species among Infants and Children in Shanghai

The overall non-neutralizing antibody responses against EV infections among infants and children remain unknown. The non-neutralizing antibody responses against VP1 of EV-A species (Enterovirus 71 (EV71), Coxsackievirus A16 (CA16)), EV-B species (Coxsackievirus B3 (CB3)), EV-C species (Poliovirus 1 (PV1)) and RV-A species (Rhinovirus A N13 (RV13)) were detected and analyzed using a novel evolved immunoglobulin-binding molecule (NEIBM)-based ELISA among infants and children aged 1 day to 6 years in Shanghai. The anti-VP1 reactivity against these EVs changed similarly in an age-related dynamic: being high level in the 1-28-day age group, declining to the lowest level in the 1-12-month age group, gradually increasing to the peak level in the 13-60-month age group, and remarkably declining in the 61-72-month age group, which reflects the conversion from maternally-derived to primary antibody responses. The anti-RV13 VP1 antibodies were demonstrated at the highest level, with anti-CB3 and PV1 VP1 antibodies at the second highest level and anti-CA16 and EV71 VP1 antibodies at the lowest level. These findings are the first to describe the overall non-neutralizing antibody responses against VP1 of the EV-A, B, C and RV-A viruses among the infants and children and could be helpful for further understanding the ubiquitous EV infections among children.

Characterization of novel monoclonal antibodies against the MERS-coronavirus spike protein and their application in species-independent antibody detection by competitive ELISA

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Novel monoclonal antibodies against MERS-CoV were produced and characterized.

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Anti-MERS-CoV antibody detection system by competitive ELISA was developed.

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The competitive ELISA was validated using sera taken from dromedary camels.

Since discovering the Middle East respiratory syndrome coronavirus (MERS-CoV) as a causative agent of severe respiratory illness in the Middle East in 2012, serological testing has been conducted to assess antibody responses in patients and to investigate the zoonotic reservoir of the virus. Although the virus neutralization test is the gold standard assay for MERS diagnosis and for investigating the zoonotic reservoir, it uses live virus and so must be performed in high containment laboratories. Competitive ELISA (cELISA), in which a labeled monoclonal antibody (MAb) competes with test serum antibodies for target epitopes, may be a suitable alternative because it detects antibodies in a species-independent manner. In this study, novel MAbs against the spike protein of MERS-CoV were produced and characterized. One of these MAbs was used to develop a cELISA. The cELISA detected MERS-CoV-specific antibodies in sera from MERS-CoV-infected rats and rabbits immunized with the spike protein of MERS-CoV. The MAb-based cELISA was validated using sera from Ethiopian dromedary camels. Relative to the neutralization test, the cELISA detected MERS-CoV-specific antibodies in 66 Ethiopian dromedary camels with a sensitivity and specificity of 98% and 100%, respectively. The cELISA and neutralization test results correlated well (Pearson’s correlation coefficients = 0.71–0.76, depending on the cELISA serum dilution). This cELISA may be useful for MERS epidemiological investigations on MERS-CoV infection.

Different Antibody Response against the Coxsackievirus A16 VP1 Capsid Protein: Specific or Non-Specific

Coxsackievirus A16 (CA16) is one of the major causative agents of hand, foot, and mouth disease worldwide. The non-neutralizing antibody response that targets CA16 VP1 remains poorly elucidated. In the present study, antibody responses against CA16 VP1 in Shanghai blood donors and Shanxi individuals were analyzed by ELISA and inhibitory ELISA using five CA16 VP1 antigens: VP1_1-297, VP1_41-297, VP1_1-60, VP1_45-58 and VP1_61-297. The correlation coefficients for most of the reactions against each of the five antigens and the inhibition of the anti-CA16 VP1 antibody response produced by the various antigens were higher in Shanghai blood donors compared to those in Shanxi individuals. VP1_1-297 and VP1_41-297 strongly inhibited the anti-CA16 VP1 response in serum samples from both populations, while VP1_45-58 and VP1_61-297 intermediately and weakly inhibited the anti-CA16 VP1 response, respectively, in only Shanghai group. A specific type of inhibition (anti-CA16 VP1 was completely inhibited by both VP1_1-60 and VP1_41-297) characterized by high neutralizing antibody titers was identified and accounted for 71.4% of the strongly reactive samples from the Shanghai group. These results indicate that the Shanghai blood donors exhibited a consistent and specific antibody response, while the Shanxi individuals showed an inconsistent and non-specific antibody response. These findings may improve the understanding of host humoral immunity against CA16 and help to identify an effective approach for seroepidemiological surveillance and specific diagnosis of CA16 infection based on normal and competitive ELISA.

Serological detection and analysis of anti-VP1 responses against various enteroviruses (EV) (EV-A, EV-B and EV-C) in Chinese individuals

The overall serological prevalence of EV infections based on ELISA remains unknown. In the present study, the antibody responses against VP1 of the EV-A species (enterovirus 71 (EV71), Coxsackievirus A16 (CA16), Coxsackievirus A5 (CA5) and Coxsackievirus A6 (CA6)), of the EV-B species (Coxsackievirus B3 (CB3)), and of the EV-C species (Poliovirus 1 (PV1)) were detected and analyzed by a NEIBM (novel evolved immunoglobulin-binding molecule)-based ELISA in Shanghai blood donors. The serological prevalence of anti-CB3 VP1 antibodies was demonstrated to show the highest level, with anti-PV1 VP1 antibodies at the second highest level, and anti-CA5, CA6, CA16 and EV71 VP1 antibodies at a comparatively low level. All reactions were significantly correlated at different levels, which were approximately proportional to their sequence similarities. Antibody responses against EV71 VP1 showed obvious differences with responses against other EV-A viruses. Obvious differences in antibody responses between August 2013 and May 2014 were revealed. These findings are the first to describe the detailed information of the serological prevalence of human antibody responses against the VP1 of EV-A, B and C viruses, and could be helpful for understanding of the ubiquity of EV infections and for identifying an effective approach for seroepidemiological surveillance based on ELISA.

Characterization of the antibody response against EV71 capsid proteins in Chinese individuals by NEIBM-ELISA

Human enterovirus 71 (EV71) has become the major pathogen of hand, foot, and mouth disease (HFMD) worldwide, while the anti-EV71 antibody responses other than neutralizing epitopes have not been characterized. In this study, EV71 capsid proteins VP1, VP3, VP0 and various VP1 antigens were constructed to analyze anti-EV71 response in severe HFMD cases, non-HFMD outpatient children and normal adults using a novel evolved immunoglobulin-binding molecule (NEIBM)-based ELISA. The high prevalence of antibody responses against all three capsid proteins was demonstrated, and anti-EV71 VP1 showed the main antibody response. Anti-EV71 VP1 antibody response was found to predominantly target to epitopes based on the common enterovirus cross-reactive sequence. Moreover, inhibition pattern against anti-EV71 VP1 reactions in three groups was obviously different. Taken together, these results firstly characterized the anti-EV71 antibody responses which are predominantly against VP1 epitopes based on common enterovirus cross-reactive sequence. This finding could be helpful for the better understanding of anti-EV71 humoral immunity and useful for seroepidemiological surveillance.

Application of West Nile virus diagnostic techniques

West Nile virus (WNV) is an enveloped RNA virus in the family Flaviviridae and belongs to Japanese encephalitis virus serocomplex group. The WNV has a wide geographic distribution that includes Africa, Europe, Asia, America and Australia. Recently, it has re-emerged as an important pathogenic organism, illustrated by the series of WNV outbreaks in North America and in Europe. Several hundred people are sacrificed by WNV infection every year. WNV can infect many mammals, birds, reptiles and amphibians. A variety of diagnoses for WNV infection have been developed, such as virus isolation, nucleotide amplification, antigen detection and serology. Flaviviruses, including WNV, share common nucleotide sequences and antigenic epitopes. Understanding these properties that can influence cross-reactivity is important for accurate diagnosis, especially because areas with multiple flaviviruses are currently expanding. Herein, the authors outline the different diagnostic methods for detecting WNV infection as well as important considerations in using these methods.

Development of monoclonal antibodies to West Nile virus and their application in immunohistochemistry

West Nile virus (WNV) is endemic throughout Africa, Eurasia, America, and Australia and has important implications for avian, horse, and human health. In these regions, dead birds are monitored for the presence of WNV through immunohistochemistry (IHC) and PCR. However, a number of the tools for IHC are inadequate owing to their cross-reactivity to other Japanese encephalitis serogroup viruses. Here we have established eight monoclonal antibodies (MAbs) to WNV. Four of them bound to the envelope protein, three of them bound to nonstructural protein 1 (NS1), and one bound to precursor membrane protein (prM), as shown by Western blot analysis. The anti-NS1 MAbs and the anti-prM MAb did not cross-react with Japanese encephalitis virus (JEV), Murray valley encephalitis virus, or St. Louis encephalitis virus in an indirect enzyme-linked immunosorbent assay. One NS1-specific MAb, SHW-32B1, and the previously reported NS1-specific MAb, SHW-7A11, were shown by IHC to specifically detect the cytoplasm of degenerated cells in the heart and brain of a WNV-infected goose. Neither of these MAbs were shown by IHC to cross-react with degenerated cells in the brain of a JEV-infected pig. These MAbs are the first reported anti-NS1 MAbs that can be used for WNV-specific IHC using formalin-fixed, paraffin-embedded sections. They may be useful for WNV research and surveillance.