Development of a recombinant ELISA using yeast (Pichia pastoris)-expressed polypeptides for detection of antibodies against avian influenza A subtype H5

Antigen epitopes of animal coronaviruses: a mini-review

Coronaviruses are widespread in nature and can infect mammals and poultry, making them a public health concern. Globally, prevention and control of emerging and re-emerging animal coronaviruses is a great challenge. The mechanisms of virus-mediated immune responses have important implications for research on virus prevention and control. The antigenic epitope is a chemical group capable of stimulating the production of antibodies or sensitized lymphocytes, playing an important role in antiviral immune responses. Thus, it can shed light on the development of diagnostic methods and novel vaccines. Here, we have reviewed advances in animal coronavirus antigenic epitope research, aiming to provide a reference for the prevention and control of animal and human coronaviruses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s44149-023-00080-0.

Quantitative detection of Ganodermati lucidum immunomodulatory protein-8 by a peptide-antigen-antibody sandwich ELISA

In order to rapidly determine the concentration of recombinant Ganoderma lucidum immunomodulatory protein-8 (rLZ-8) at a lower cost, a peptide-antigen-antibody sandwich ELISA method was developed based on a dodecapeptide LTPHKHHKHLHA with higher affinity for rLZ-8, which was identified from phage display after four rounds of screening. The binding mode between rLZ-8 and the peptide ligand was further simulated and revealed by molecular docking. Standard addition and repetitive testing were carried out to evaluate the accuracy, reproducibility and feasibility of the developed ELISA detection method. The method based on this peptide ligand was then successfully applied in the quantitative determination of rLZ-8 concentrations in fermentation broth. In summary, the peptide-antigen-antibody sandwich ELISA method developed here could be conveniently applied in the detection of rLZ-8 during fermentation and might provide new insights for the detection of other specific proteins.

Sensitive antibody fluorescence immunosorbent assay (SAFIA) for rapid on-site detection on avian influenza virus H9N2 antibody

Avian influenza virus (AIV) is a serious zoonotic disease causing severe damages to both poultry industry and human health. To rapidly detect AIV on-site with high sensitivity and accuracy, we design sensitive antibody fluorescence immunosorbent assay (SAFIA) on AIV H9N2 antibody. In SAFIA, hemagglutinin (HA1) protein coated sample chamber specifically binds targets but remarkably reduces non-specific absorption; Protein L coated polystyrene microsphere captures target through secondary antibody to significantly amplify the fluorescence signal; and a portable fluorescence counter automatically measures the fluorescence spot density for AIV H9N2 antibody detection. Proved by practical applications, SAFIA could probe AIV H9N2 antibody in high sensitivity and selectivity, and distinguish positive and negative serum samples in high accuracy. Additionally, SAFIA can rapidly detect AIV H9N2 antibody at room temperature only requiring simple operations as well as cost-effective and compact devices. Therefore, SAFIA is a potential new-generation tool in rapid on-site testing for agricultures.

Immunization of turkeys with a DNA vaccine expressing the haemagglutinin gene of low pathogenic avian influenza virus subtype H9N2

Low pathogenic avian influenza H9N2 is still circulating in the Middle East causing respiratory manifestations and severe economic losses in poultry. In the present study, an H9 plasmid-based DNA vaccine targeting the HA gene of H9N2 A/CK/Egypt/SCU8/2014 was developed and evaluated in turkeys. The full length of HA was cloned into vector plasmids under the control of a cytomegalovirus promoter. The in-vitro expression of the recombinant HA was demonstrated in HeLa cells transfected with the plasmids pVAX1-H9 or pCR-H9 using western blot and Immunofluorescent assay (IFA). The efficacy of pVAX-H9 and pCR- H9, naked or saponin-adjuvanted, was evaluated in turkey poults at 3 weeks and challenged with A/CK/Egypt/SCU8/2014 (10⁶ EID₅₀/bird at 3 weeks post-vaccination. The efficacy was assesses based on virus shedding, oropharyngeal and cloacal, as well as seroconversion using haemagglutination inhibition (HI) test. All immunized birds showed high HI antibody titers (7-8 log₂) at 3 weeks post-vaccination. None of the birds vaccinated with naked or saponin-adjuvanted pVAX-H9 or pCR-H9 showed any clinical signs. The pVAX-H9 and pCR-H9 alone did not prevent cloacal and oropharyngeal virus shedding, however, saponin-adjuvanted pVAX1-H9 and pCR-H9 prevented cloacal and oropharyngeal virus shedding at 3 and 5 days post challenge, respectively. In conclusion, DNA vaccination with pVAX1-H9 and pCR-H9 could protect turkey from the H9N2 virus, but vaccination regimes need to be improved.

Detecting Biothreat Agents: From Current Diagnostics to Developing Sensor Technologies

Although a fundamental understanding of the pathogenicity of most biothreat agents has been elucidated and available treatments have increased substantially over the past decades, they still represent a significant public health threat in this age of (bio)terrorism, indiscriminate warfare, pollution, climate change, unchecked population growth, and globalization. The key step to almost all prevention, protection, prophylaxis, post-exposure treatment, and mitigation of any bioagent is early detection. Here, we review available methods for detecting bioagents including pathogenic bacteria and viruses along with their toxins. An introduction placing this subject in the historical context of previous naturally occurring outbreaks and efforts to weaponize selected agents is first provided along with definitions and relevant considerations. An overview of the detection technologies that find use in this endeavor along with how they provide data or transduce signal within a sensing configuration follows. Current "gold" standards for biothreat detection/diagnostics along with a listing of relevant FDA approved in vitro diagnostic devices is then discussed to provide an overview of the current state of the art. Given the 2014 outbreak of Ebola virus in Western Africa and the recent 2016 spread of Zika virus in the Americas, discussion of what constitutes a public health emergency and how new in vitro diagnostic devices are authorized for emergency use in the U.S. are also included. The majority of the Review is then subdivided around the sensing of bacterial, viral, and toxin biothreats with each including an overview of the major agents in that class, a detailed cross-section of different sensing methods in development based on assay format or analytical technique, and some discussion of related microfluidic lab-on-a-chip/point-of-care devices. Finally, an outlook is given on how this field will develop from the perspective of the biosensing technology itself and the new emerging threats they may face.

Production of a truncated recombinant HA1 for influenza A H9 subtype screening

Hemagglutinin is the major component of membrane protein and plays a major role in virus entry into host cells through their receptors and it is predicted to elicit the production neutralizing antibodies. Our aim is to assess the potential of a truncated rHA1 domain, encoding residues 157-260 to detect influenza A H9 specific antibodies. The predicted characteristics of this protein revealed that it is a hydrophobic protein possessing predominant antigenicity and composed of random coils (48%) and extended strand (28%) but few α-helix (6.33%) and β-sheet (7%). A 312 pb HA1 gene was amplified and cloned in pET23b(+) vector including an C-terminal polyHis as a fusion partner, transformed and expressed in Escherichia coli cells as inclusion bodies. The truncated protein was solubilized with 8 M urea, purified by immobilized metal affinity chromatography and then detected by western blot with anti-His and H9-specific polyclonal antibodies. The test demonstrated high specificity (100%) and sensibility (98%). The immunoreactivity of the truncated rHA1 assessed revealed that only antisera against H9 yielded a specific and strong reactivity, with no cross-reactivity against negative sera. This study demonstrates that the truncated rHA1 may serve as a useful tool for rapid and easy surveillance of H9 infection.

Production of Influenza Virus HA1 Harboring Native-Like Epitopes by Pichia pastoris

The outbreak of the H5N1 highly pathogenic avian influenza which exhibits high variation had brought a serious threat to the safety of humanity. To overcome this high variation, hemagglutinin-based recombinant subunit vaccine with rational design has been considered as a substitute for traditional virion-based vaccine development. Here, we expressed HA1 part of the hemagglutinin protein using the Pichia pastoris expression system and attained a high yield of about 120 mg/L through the use of fed-batch scalable fermentation. HA1 protein in the culture supernatant was purified using two-step ion-exchange chromatography. The resultant HA1 protein was homogeneous in solution in a glycosylated form, as confirmed by endoglycosidase H treatment. Sedimentation velocity tests, silver staining of protein gels, and immunoblotting were used for verification. The native HA1 reacted well with conformational, cross-genotype, neutralizing monoclonal antibodies, whereas a loss of binding activity was noted with the denatured HA1 form. Moreover, the murine anti-HA1 serum exhibited a virus-capture capability in the hemagglutination inhibition assay, which suggests that HA1 harbors native-like epitopes. In conclusion, soluble HA1 was efficiently expressed and purified in this study. The functional glycosylated protein will be an alternative for the development of recombinant protein-based influenza vaccine.

Development of an Indirect ELISA for Serological Diagnosis of Bovine herpesvirus 5

Bovine herpesviruses 1 and 5 (BoHV-1 and BoHV-5) are economically important pathogens, associated with a variety of clinical syndromes, including respiratory and genital disease, reproductive failure and meningoencephalitis. The standard serological assay to diagnose BoHV-1 and BoHV-5 infections is the virus neutralization test (VNT), a time consuming procedure that requires manipulation of infectious virus. In the present study a highly sensitive and specific single dilution indirect ELISA was developed using recombinant glycoprotein D from BoHV-5 as antigen (rgD5ELISA). Bovine serum samples (n = 450) were screened by VNT against BoHV-5a and by rgD5ELISA. Compared with the VNT, the rgD5ELISA demonstrated accuracy of 99.8%, with 100% sensitivity, 96.7% specificity and coefficient of agreement between the tests of 0.954. The rgD5ELISA described here shows excellent agreement with the VNT and is shown to be a simple, convenient, specific and highly sensitive virus-free assay for detection of serum antibodies to BoHV-5.

Expression and purification of recombinant H5HA1 protein of H5N1 avian influenza virus in E. coli and its application in indirect ELISA

The PCR amplified HA1 fragment of H5N1 (H5HA1) avian influenza virus (AIV) hemagglutinin gene was cloned into pET28a (+) expression vector and expressed in Rosetta Blue (DE3) pLysS cells. The recombinant H5HA1 (rH5HA1) protein purified by passive gel elution after SDS-PAGE of the inclusion bodies reacted specifically with H5N1 serum in Western blot analysis. A subtype specific indirect enzyme linked immunosorbent assay (iELISA) using the rH5HA1 protein as the coating antigen was developed for detecting antibodies to H5 subtype of AIV. The assay had 89.04% sensitivity and 95.95% specificity when compared with haemagglutination inhibition test. The Kappa value of 0.842 indicated a perfect agreement between the tests. The iELISA developed can be used for serosurveillance of avian influenza in chickens.

Development of a multi-epitope antigen of S protein-based ELISA for antibodies detection against infectious bronchitis virus

An indirect enzyme-linked immunosorbent assay (ELISA) method based on a novel multi-epitope antigen of S protein (SE) was developed for antibodies detection against infectious bronchitis virus (IBV). The multi-epitope antigen SE protein was designed by arranging three S gene fragments (166–247 aa, S1 gene; 501–515 aa, S1 gene; 8–30 aa, S2 gene) in tandem. It was identified to be approximately 32 kDa as a His-tagged fusion protein and can bind IBV positive serum by western blot analysis. The conditions of the SE-ELISA method were optimized. The optimal concentration of the coating antigen SE was 3.689 μg/mL and the dilution of the primary antibodies was identified as 1:1000 using a checkerboard titration. The cut-off OD450 value was established at 0.332. The relative sensitivity and specificity between the SE-ELISA and IDEXX ELISA kit were 92.38 and 89.83%, respectively, with an accuracy of 91.46%. This assay is sensitive and specific for detection of antibodies against IBV.

A potential protein-based vaccine for influenza H5N1 from the recombinant HA1 domain of avian influenza A/H5N1 expressed in Pichia pastoris

ABSTRACT 

The HA1 genes from influenza A strains A/Puerto Rico/8/1934 H1N1 (A/PR/8/34) and A/Hatay/2004 H5N1 were each cloned in Pichia pastoris vectors in the correct reading frame with the yeast α-factor secretion signal and the C-terminus His-tag, resulting in simple, fast purification of expressed H1HA1 and H5HA1 protein from the culture medium. Mice vaccinated with the purified proteins showed robust T cell, anti-HA1 IgG responses and developed a high antibody response for hemagglutination inhibition (HI) at titer 7.6 log2. Chickens vaccinated with a dose of 200 µg of H5HA1 mixed with either Montanide or Freund's adjuvants gave HI values of up to 7 log2 at the third week comparable with a licensed inactivated H5N1 vaccine.

Development of an indirect ELISA for detection of E. Coli antibodies in cow serum using a recombinant OmpT as antigen

The aim of this article was to develop an indirect enzyme-linked immunosorbent assay (ELISA) for efficient detection of the infection of E. coli in cattle. OmpT, a highly conserved protease in all E. coli strains, was successfully expressed in E. coli XL-1-Blue strain with PET32a vector. Molecular weight of recombinant protein was identified by analyzing SDS-PAGE and the immunogenicity of OmpT was confirmed by Western Blotting. The recombinant OmpT was then employed as capture antigen in the ELISA. The antigen concentration and serum dilution were determined using a checkerboard titration. Results showed that the optimal concentration of coated antigen was 1 μg/ml at a serum dilution of 1:640 and the cut-off value of the assay was 0.335. In addition, the cross-reactivity assay showed that the OmpT was E. coli specific and the reproducibility experiments displayed good repeatability of the assay. Three hundred and forty cattle serum samples were tested by rOmpT-ELISA and sera coagulation tests. The ELISA has showed relative sensitivity of 100% and specificity of 96.47%. Results of these experiments indicated that the rOmpT-ELISA is a simple, rapid, and convenient method for detection the infection of E. coli with different serotype strains.

Evaluation of a commercial ELISA for H5 low pathogenic avian influenza virus antibody detection in duck sera using Bayesian methods

Following the emergence of highly pathogenic avian influenza (AI), active surveillance of infections due to the H5 and H7 subtypes in poultry has increased and been made compulsory in Europe since 2002, by means of annual serological surveys using the haemagglutination inhibition (HI) test. Domestic anseriforms, particularly ducks and geese, are more frequently infected by H5 low pathogenic AI virus, often subclinically, and represent a threat for other terrestrial poultry. 1783 sera, mainly from ducks, have been used to evaluate and compare a commercial ELISA kit detecting H5 antibodies with the currently recommended HI test. Different approaches to calculating specificity and sensitivity have been used, including the original Bayesian method. Results were similar when data were analyzed at the individual and batch levels, and when using different methods of calculation. However, results showed that H5 ELISA had both a higher sensitivity and a lower specificity than the HI test. Given that sensitivity is the most important factor for a screening test, H5 ELISA could therefore be recommended for AI surveillance, followed in cases of positivity by molecular tests aimed at detecting the virus gene.

Biological properties of H5 hemagglutinin expressed by vaccinia virus vector and its immunological reactivity with human sera

A recombinant vaccinia virus harboring the full length hemagglutinin (HA) gene derived from a highly pathogenic avian influenza A/Thailand/1(KAN-1)/2004 (H5N1) virus (rVac-H5 HA virus) was constructed. The immunogenicity of the expressed HA protein was characterized using goat antiserum, mouse monoclonal antibody, and human sera. The expressed HA protein localized both in the cytoplasm and on the cytoplasmic membrane of the thymidine kinase negative cells infected with the rVac-H5 HA virus, as determined by immunofluorescence assay. Western blot analysis demonstrated that the rVac-H5 HA protein was post-translationally processed by proteolytic cleavage of the HA0 precursor into HA1 and HA2 domains; and all of these HA forms were immunogenic in BALB/c mice. The molecular weight (MW) of each HA domain was the same as the wild-type H5 HA produced in Madin-Darby canine kidney cells infected with the H5N1 virus, but was higher than that expressed by a baculovirus-insect cell system. Sera from all H5N1 survivors reacted to HA0, HA1, and HA2 domains; whereas sera from H5N1-uninfected subjects reacted to the HA2 domain only, but not to HA0 or HA1, indicating that some cross-subtypic immunity exists in the general population. There was a lot-to-lot variation of the recombinant HA produced in the baculovirus-insect cell system that might affect the detection rate of antibody directed against certain HA domains.

A simple Pichia pastoris fermentation and downstream processing strategy for making recombinant pandemic Swine Origin Influenza a virus Hemagglutinin protein

The present Influenza vaccine manufacturing process has posed a clear impediment to initiation of rapid mass vaccination against spreading pandemic influenza. New vaccine strategies are therefore needed that can accelerate the vaccine production. Pichia offers several advantages for rapid and economical bulk production of recombinant proteins and, hence, can be attractive alternative for producing an effective influenza HA based subunit vaccine. The recombinant Pichia harboring the transgene was subjected to fed-batch fermentation at 10 L scale. A simple fermentation and downstream processing strategy is developed for high-yield secretory expression of the recombinant Hemagglutinin protein of pandemic Swine Origin Influenza A virus using Pichia pastoris via fed-batch fermentation. Expression and purification were optimized and the expressed recombinant Hemagglutinin protein was verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis, Western blot and MALDI-TOF analysis. In this paper, we describe a fed-batch fermentation protocol for the secreted production of Swine Influenza A Hemagglutinin protein in the P. pastoris GS115 strain. We have shown that there is a clear relationship between product yield and specific growth rate. The fed-batch fermentation and downstream processing methods optimized in the present study have immense practical application for high-level production of the recombinant H1N1 HA protein in a cost effective way using P. pastoris.