Expression of Foot-and-Mouth Disease Virus Non-Structural Protein, 3D in Insect Cells and its Application in Detection of Anti-FMDV Antibodies

Estimation of foot-and-mouth disease virus sero-prevalence rates using novel computational approach for the susceptible bovine population in India during the period 2008-2021

Foot-and-mouth disease (FMD) is a severe contagious viral disease of cloven-hoofed animals. In India, a vaccination-based official FMD control programme was started, which got expanded progressively to cover entire country in 2019. The serological tests are used to determine non-structural protein based sero-prevalence rates for properly implementing and assessing the control programme. Since 2008, reporting of the FMD sero-surveillance was limited to the serum sample-based serological test results without going for population-level estimation due to lack of proper statistical methodology. Thus, we present a computational approach for estimating the sero-prevalence rates at the state and national levels. Based on the reported approach, a web-application ( https://nifmd-bbf.icar.gov.in/FMDSeroSurv ) and an R software package ( https://github.com/sam-dfmd/FMDSeroSurv ) have been developed. The presented computational techniques are applied to the FMD sero-surveillance data during 2008-2021 to get the status of virus circulation in India under a strict vaccination policy. Furthermore, through various structural equation models, we attempt to establish a link between India's estimated sero-prevalence rate and field FMD outbreaks. Our results indicate that the current sero-prevalence rates are significantly associated with previous field outbreaks up to 2 years. Besides, we observe downward trends in sero-prevalence and outbreaks over the years, specifically after 2013, which indicate the effectiveness of various measures implemented under the FMD control programme. The findings of the study may help researchers and policymakers to track virus infection and identification of potential disease-free zones through vaccination.

An Adenovirus Vector Expressing FMDV RNA Polymerase Combined with a Chimeric VLP Harboring a Neutralizing Epitope as a Prime Boost Strategy to Induce FMDV-Specific Humoral and Cellular Responses

Foot and mouth disease is a highly contagious disease affecting cattle, sheep, and swine among other cloven-hoofed animals that imposes serious economic burden by its direct effects on farm productivity as well as on commerce of farmed produce. Vaccination using inactivated viral strains of the different serotypes is an effective protective measure, but has several drawbacks including a lack of cross protection and the perils associated with the large-scale growth of infectious virus. We have previously developed chimeric virus-like particles (VLPs) bearing an FMDV epitope which induced strong specific humoral responses in vaccinated pigs but conferred only partial protection against homologous challenge. While this and other FMD vaccines under development mostly rely on the induction of neutralizing responses, it is thought that induction of specific T-cell responses might improve both cross protective efficacy as well as duration of immunity. Therefore, we here describe the development of a recombinant adenovirus expressing the highly conserved nonstructural FMDV 3D protein as well as its capacity to induce specific T-cell responses in a murine model. We further describe the generation of an FMDV serotype C-specific chimeric VLP and analyze the immunogenicity of two different prime-boost strategies combining both elements in mice. This combination can effectively induce both humoral and cellular FMDV-specific responses eliciting high titers of ELISA and neutralizing antibodies anti-FMDV as well as a high frequency of IFNγ-secreting cells. These results provide the basis for further testing of this anti FMD vaccination strategy in cattle or pig, two of the most relevant natural host of this pathogen.

A Membrane-Targeting Photosensitizer with Aggregation-Induced Emission Characteristics for Highly Efficient Photodynamic Combat of Human Coronaviruses

COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2, has resulted in global social and economic disruption, putting the world economy to the largest global recession since the Great Depression. To control the spread of COVID-19, cutting off the transmission route is a critical step. In this work, the efficient inactivation of human coronavirus with photodynamic therapy (PDT) by employing photosensitizers with aggregation-induced emission characteristics (DTTPB) is reported. DTTPB is designed to bear a hydrophilic head and two hydrophobic tails, mimicking the structure of phospholipids on biological membranes. DTTPB demonstrates a broad absorption band covering the whole visible light range and high molar absorptivity, as well as excellent reactive oxygen species sensitizing ability, making it an excellent candidate for PDT. Besides, DTTPB can target membrane structure, and bind to the envelope of human coronaviruses. Upon light irradiation, DTTPB demonstrates highly effective antiviral behavior: human coronavirus treated with DTTPB and white-light irradiation can be efficiently inactivated with complete loss of infectivity, as revealed by the significant decrease of virus RNA and proteins in host cells. Thus, DTTPB sensitized PDT can efficiently prevent the infection and the spread of human coronavirus, which provides a new avenue for photodynamic combating of COVID-19.

Monoclonal antibodies against foot-and-mouth disease virus RNA polymerase for detection of virus infection

Foot-and-mouth disease (FMD) is a major viral disease in farm animals. In the present study, seven monoclonal antibodies (mAbs) were produced against the FMD virus (FMDV)-encoded RNA-dependent RNA polymerase (3D protein) and characterized. Screening of mAb reactivity against three overlapping fragments of the 3D protein expressed in Escherichia coli revealed that the binding sites of all the mAbs were confined to the N-terminal one-third of the 3D protein. A selected mAb was utilized for detecting FMDV in the infected cell culture and tissues obtained from FMDV-infected animals.

Are Epitopic Sites of 3AB and 3D Nonstructural Proteins Sufficient for Detection of Foot and Mouth Disease?

An efficient method for detection of foot and mouth disease (FMD) and, particularly, differentiation of vaccinated from infected animals is the use of nonstructural (NS) proteins as antigens in Enzyme-Linked Immunosorbent Assay (ELISA) Kits. In this study, only epitopic regions of 3AB and 3D NS proteins were used for recombinant protein production, as a cost-effective method instead of peptide synthesis, for application in in-house ELISA diagnostic kits. Specific primers were designed according to the antigenic regions of 3AB (C-terminus of 3A and the whole 3B) and 3D (N-terminus) proteins, and the polymerase chain reaction (PCR) amplification was performed. Purified amplicons were cloned into pET21a (+) vectors and then transformed into Escherichia coli (BL21). Thereafter, bacteria were induced with 1 mM isopropyl β-d-1-thiogalactopyranoside (IPTG) for expression of antigenic proteins. Antigenic 3AB protein was expressed in soluble form, but 3D protein was extracted from the bacterial lysate. Protein expression was confirmed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analyses. An indirect ELISA was developed for each protein, and the diagnostic sensitivity and specificity were determined. The 3AB-ELISA showed higher sensitivity and specificity than 3D-ELISA (95.24% and 100%, compared with 90.48% and 88.71%, respectively). The epitopic 3AB-ELISA developed here can be used for detection and differentiation of FMD infected from vaccinated animals, but the epitopic 3D-ELISA showed lower efficiency in screening for FMD status.

Caracterización de la proteína no capsidal 3D, del virus de la fiebre aftosa y producción de anticuerpos policlonales

Las proteínas no capsidales del virus de la fiebre aftosa se utilizan como marcadoras en la evaluación de animales que han estado en contacto con el virus, a diferencia de los inmunizados, ya que la vacuna no debe tener estas proteínas, por lo tanto los animales no deben presentar anticuerpos contra ellas. El objetivo de esta investigación fue la caracterización de la proteína no capsidal 3D y la producción de anticuerpos policlonales in vivo. La proteína se purificó del cultivo de virus inactivo, por cromatografía de intercambio iónico. La elución de los picos fue sometida a electroforesis uni-bidimensional; demostrándose un alto grado de pureza (>90%) en el pico tres, donde se identifico la proteína 3D, por la técnica de MALDI-TOF y electroespray de trampa iónica. La proteína purificada, se inoculó en cabras y el suero hiperinmune fue precipitado y sometido a cromatografía de afinidad para la obtención de inmunoglobulinas; la reacción inmunitaria se con­firmó por medio de inmunodifusión y Western blot. El proceso de purificación demostró ser eficiente y útil para la obtención de anticuerpos específicos, los cuales tendrán utilidad en la elaboración de un ensayo inmunoenzimático que mida la pureza de la vacuna frente al contenido de estas proteínas. 

Multi-resistance strategy for viral diseases and in vitro short hairpin RNA verification method in pigs

Objective

Foot and mouth disease (FMD) and porcine reproductive and respiratory syndrome (PRRS) are major diseases that interrupt porcine production. Because they are viral diseases, vaccinations are of only limited effectiveness in preventing outbreaks. To establish an alternative multi-resistant strategy against FMD virus (FMDV) and PRRS virus (PRRSV), the present study introduced two genetic modification techniques to porcine cells.

Methods

First, cluster of differentiation 163 (CD163), the PRRSV viral receptor, was edited with the clustered regularly interspaced short palindromic repeats-CRISPR-associated protein 9 technique. The CD163 gene sequences of edited cells and control cells differed. Second, short hairpin RNA (shRNAs) were integrated into the cells. The shRNAs, targeting the 3D gene of FMDV and the open reading frame 7 (ORF7) gene of PRRSV, were transferred into fibroblasts. We also developed an in vitro shRNA verification method with a target gene expression vector.

Results

shRNA activity was confirmed in vitro with vectors that expressed the 3D and ORF7 genes in the cells. Cells containing shRNAs showed lower transcript levels than cells with only the expression vectors. The shRNAs were integrated into CD163-edited cells to combine the two techniques, and the viral genes were suppressed in these cells.

Conclusion

We established a multi-resistant strategy against viral diseases and an in vitro shRNA verification method.

The 3D protein of duck hepatitis A virus type 1 binds to a viral genomic 3' UTR and shows RNA-dependent RNA polymerase activity

To explore the RNA-dependent RNA polymerase (RdRP) function of the 3D protein of duck hepatitis A virus type 1 (DHAV-1), the gene was cloned into the pET-32a(+) vector for prokaryotic expression. The 3' untranslated region (3' UTR) of DHAV-1 together with a T7 promoter was cloned into the pMD19-T vector for in vitro transcription of 3' UTR RNA, which was further used as a template in RNA-dependent RNA polymerization. In this study, three methods were applied to analyze the RdRP function of the 3D protein: (1) ammonium molybdate spectrophotometry to detect pyrophosphate produced during polymerization; (2) quantitative reverse transcription PCR (RT-qPCR) to investigate the changes in RNA quantity during polymerization; and (3) electrophoresis mobility shift assay to examine the interaction between the 3D protein and 3' UTR. The results showed the 3D protein was successfully expressed in bacteria culture supernatant in a soluble form, which could be purified by affinity chromatography. In 3D enzymatic activity assays, pyrophosphate and RNA were produced, the amounts of which increased based on approximative kinetics, and binding of the 3D protein to the 3' UTR was observed. These results indicate that prokaryotically expressed soluble DHAV-13D protein can bind to a viral genomic 3' UTR and exhibit RdRP activity.

Outbreak of foot and mouth disease and peste des petits ruminants in sheep flock imported for immediate slaughter in Riyadh

Aim:

To detect and identify the causative agent or agents of the following clinical symptoms which were fever, lack of appetite, salivation, vesiculation, erosions of the buccal mucosa, nose, and feet. The signs vary from mild to severe. The mortality rate of the disease is high. The morbidity rate reaches up to 100%. Sheep also show bloody diarrhea and rapid respiration. Sheep flock resident in El-Kharje Governorate.

Materials and Methods:

A total of 50 serum samples and 50 buffy coat samples were collected from Marino sheep flock suffered from high mortalities, fever, lameness, diarrhea, stomatitis, and respiratory distress. PrioCHECK^® foot and mouth disease virus (FMDV) nonstructural (NS) (marketable enzyme-linked immunosorbent assay [ELISA] kit) was used for revealing of the NS antibodies and liquid phase blocking enzyme immunoassay (LPBE) for identifying the FMD serotype and examined by competitive ELISA (cELISA) for detection of peste des petits ruminants (PPR) antibodies. The buffy coat samples were examined by immunocapture ELISA (Ic ELISA) for detection of PPR antigen.

Results:

Using PrioCHECK^® FMDV NS: Commercial ELISA kit: 38/50 (76%) of the serum samples were positive for the presence of FMD NS viral proteins. In addition, using LPBE the positive samples were identified as FMD serotype O. Examination of the serum sample by cELISA for detection of PPR antibodies gave positive results in 32/50 (64%). While the Ic ELISA identified 32 (64%) positive reactors for PPR antigen.

Conclusion:

This study reflected high susceptibility of the imported sheep flocks to the infection with FMD and PPR viruses, which are endemic in the Kingdom of Saudi Arabia (KSA). Hence, the imported flocks that prepared for slaughter must be vaccinated with the used vaccine in KSA in the quarantine for the control of FMD especially when importation occurs from counters that are free from these diseases.

Biological function of Foot-and-mouth disease virus non-structural proteins and non-coding elements

Foot-and-mouth disease virus (FMDV) represses host translation machinery, blocks protein secretion, and cleaves cellular proteins associated with signal transduction and the innate immune response to infection. Non-structural proteins (NSPs) and non-coding elements (NCEs) of FMDV play a critical role in these biological processes. The FMDV virion consists of capsid and nucleic acid. The virus genome is a positive single stranded RNA and encodes a single long open reading frame (ORF) flanked by a long structured 5ʹ-untranslated region (5ʹ-UTR) and a short 3ʹ-UTR. The ORF is translated into a polypeptide chain and processed into four structural proteins (VP1, VP2, VP3, and VP4), 10 NSPs (L^pro, 2A, 2B, 2C, 3A, 3B_1–3, 3C^pro, and 3D^pol), and some cleavage intermediates. In the past decade, an increasing number of studies have begun to focus on the molecular pathogenesis of FMDV NSPs and NCEs. This review collected recent research progress on the biological functions of these NSPs and NCEs on the replication and host cellular regulation of FMDV to understand the molecular mechanism of host–FMDV interactions and provide perspectives for antiviral strategy and development of novel vaccines.

A multi-species indirect ELISA for detection of non-structural protein 3ABC specific antibodies to foot-and-mouth disease virus

Reliable diagnostic tests that are able to distinguish infected from vaccinated animals are a critical component of regional control programs for foot-and-mouth disease (FMD) in the affected countries. Non-structural protein (NSP) serology based on the 3ABC protein has been widely used for this purpose, and several kits are commercially available worldwide. This report presents the development of a 3ABC-antigen-based indirect ELISA, employing a peroxidase-conjugated protein G secondary antibody that can detect antibodies from multiple species. Recombinant 3ABC protein was expressed in insect cells and purified using affinity column chromatography. Using this protein, an indirect ELISA was developed and validated for the detection of NSP antibodies in serum samples collected from animals with different status of FMD. Diagnostic sensitivity and specificity were found to be 95.8 (95 % CI: 92.8-97.8) and 97.45 % (95 % CI: 94.8-99.0), respectively. The in-house ELISA compared well with the commercially available prioCHECK FMDV NS-FMD kit, with a high agreement between the tests, as determined by the kappa coefficient, which was 0.87. The in-house ELISA showed higher sensitivity for detecting vaccinated and subsequently infected animals, when compared to the reference test. Both of the tests were able to detect NSP antibodies as early as 7-8 days after experimental infection.