Type Asia Research Articles

Establishment of the Foot-and-Mouth Disease Virus Type Asia1 Expressing the HiBiT Protein: A Useful Tool for a NanoBiT Split Luciferase Assay.

Foot-and-mouth disease virus (FMDV) is a highly contagious virus that affects cloven-hoofed animals and causes severe economic losses in the livestock industry. Given that this high-risk pathogen has to be handled in a biosafety level (BSL)-3 facility for safety reasons and the limited availability of BSL-3 laboratories, experiments on FMDV call for more attention. Therefore, we aimed to develop an FMDV experimental model that can be handled in BSL-2 laboratories. The NanoBiT luciferase (Nano-luc) assay is a well-known assay for studying protein-protein interactions. To apply the NanoBiT split luciferase assay to the diagnosis and evaluation of FMD, we developed an inactivated HiBiT-tagged Asia1 Shamir FMDV (AS-HiBiT), a recombinant Asia1 shamir FMDV with HiBiT attached to the VP1 region of Asia1 shamir FMDV. In addition, we established LgBiT-expressing LF-BK cell lines, termed LgBit-LF-BK cells. It was confirmed that inactivated AS-HiBiT infected LgBiT-LF-BK cells and produced a luminescence signal by binding to the intracellular LgBiT of LgBiT-LF-BK cells. In addition, the luminescence signal became stronger as the number of LgBiT-LF-BK cells increased or the concentration of inactivated AS-HiBiT increased. Moreover, we confirmed that inactivated AS-HiBiT can detect seroconversion in sera positive for FMDV-neutralizing antibodies. This NanoBiT split luciferase assay system can be used for the diagnosis and evaluation of FMD and expanded to FMD-like virus models to facilitate the evaluation of FMDV vaccines and antibodies.

Determination of Optimal Antigen Yield and Virus Inactivation Conditions for the Production of the Candidate Foot-and-Mouth Disease Recombinant Vaccine Strain Asia1 Shamir-R in a Bioreactor.

Since the foot-and-mouth disease (FMD) outbreak in South Korea in 2010-2011, vaccination policies utilizing inactivated FMD vaccines composed of types O and A have been implemented nationwide. However, because type Asia1 occurred in North Korea in 2007 and intermittently in neighboring countries, the risk of type Asia1 introduction cannot be ruled out. This study evaluated the antigen yield and viral inactivation kinetics of the recombinant Asia1 Shamir vaccine strain (Asia1 Shamir-R). When Asia1 Shamir-R was proliferated in shaking flasks (1 L), a 2 L bioreactor (1 L), and a wave bioreactor (25 L), the antigen yields were 7.5 μg/mL, 5.2 μg/mL, and 3.8 μg/mL, respectively. The optimal FMDV inactivation conditions were 2 mM BEI at 26 °C and 1.0 mM BEI at 37 °C. There was no antigen loss due to BEI treatment, and only a decrease in antigen levels was observed during storage. The sera from pigs immunized with antigen derived from a bioreactor exhibited a neutralizing antibody titer of approximately 1/1000 against Asia1 Shamir and Asia1/MOG/05 viruses; therefore, Asia1 Shamir-R is expected to provide sufficient protection against both viruses. If an FMD vaccine production facility is established, this Asia1 Shamir-R can be employed for domestic antigen banks in South Korea.

Immune responses of the foot-and-mouth disease virus type Asia1 chimeric vaccine against Asia1 Shamir and Asia1/MOG/05 strains in pigs

Immune responses of the foot-and-mouth disease virus type Asia1 chimeric vaccine against Asia1 Shamir and Asia1/MOG/05 strains in pigs

Analysis of Asia-1 foot-and-mouth disease global spread in 1999–2019

In spite of current foot-and-mouth disease (FMD) preventive measures, the disease outbreaks are annually reported in different countries of the world. FMD tends to extensive spread and growing into epidemics. While being a transboundary infection according to the OIE/FAO classification, FMD severely affects the economy and international trade. The paper describes the analysis of the data on global spread of Type Asia-1 virus-induced FMD in 1999–2019. The virus of this type is most often reported in such Asian countries as Afghanistan, Pakistan, China, Nepal, Iran, Myanmar, from where it can spread to FMD free countries. In China, Asia-1 FMD outbreaks were reported from 2001 to 2009. Previously exotic for our country, the virus of this type was first reported in the Primorsky, Khabarovsk, Zabaikalsky Krais and Amur Oblast in 2005–2006. The results of the phylogenetic analysis of the recovered isolates demonstrated that FMD emergence in the Subjects of the Russian Federation was attributed to the virus introduction from the neighboring territories. Possible virus introduction from China resulted in significant economic expenditures on FMD containment and eradication. In view of the close trade and economic relations between the Russian Federation and such Asia-Pacific countries as China, India, Japan and Republic of Korea, one should place greater focus on the risk of FMDV introduction into the Russian Federation from these countries. Of key importance is intensification of the international cooperation with the Asian countries in the area of joint activities aimed at FMD freedom maintenance.

Efficient protection against Asia1 type foot-and-mouth disease using a chimeric vaccine strain suitable for East Asia

The type Asia1 genetic group(G)-V lineage foot-and-mouth disease (FMD) virus was identified in the East-Asian region in 2009. To date, only Shamir has been used as a standard vaccine strain worldwide for type Asia1. To prevent type Asia1 FMD in eastern Asia, two vaccine strains (ASM-R: G–V and ASM-SM: G–V/Shamir fusion) were developed and tested against type Asia1 virus strains. After immunization with the two experimental vaccines, the ASM-SM strain showed a higher level of protection against Shamir virus in mice. Additional immunogenicity tests were carried out in cattle and pigs, revealing sufficient antibody production capable of protecting the animals against the viral challenge. In cattle, the immune response started just 2 weeks after vaccination. Immunogenicity was lower in pigs, but antibody production was greatly increased to a high level after a second vaccination round. In particular, herein, 60 % and 100 % of the vaccinated pigs challenged with the Asia1 Shamir virus were determined to be clinically protected after one and two vaccination rounds with ASM-R, respectively. Pigs vaccinated twice produced sufficient antibody titers with low virus shedding for short time. Moreover, ASM-SM single-vaccinated pigs showed 100 % protection when challenged with the Asia1 Shamir virus. In summary, the vaccine strain ASM-SM designed for the defense of the Asian region efficiently granted protection to pigs against the typical Asia1 virus, Shamir.

Antigenic properties of a novel vaccine strain for type Asia1 foot-and-mouth disease in pigs

Newly developed vaccine strains to prevent foot-and-mouth disease caused by the emerging serotype Asia1 virus were evaluated. To protect against the group (G)-VIII strain, which occurred recently, we produced an infectious cDNA clone of Asia1 Shamir cDNA (Asia1 Shamir-R). In addition, by adding a site 1 epitope of VP1 of the G-VIII lineage virus to this virus, we produced a new virus (Sham GVIII- EPI), and another virus(Sham GVIII-VP1) was replaced with that of G-VIII lineage in the VP1 region of Shamir. Test vaccines were produced using these three types of vaccine virus, and their immunogenicity and protection capabilities were evaluated in mice. Immunized mice were challenged with the Asia1 Shamir or G-VIII virus, and the results show that all the vaccines have similar protective effects. As they showed similar antigenicity, we chose the Shamir-R vaccine. Pigs maintained relatively high neutralizing antibody levels against homologous viruses of the Shamir and G-VII or G-VIII lineage three to four weeks after immunization. However, they formed relatively low levels of antibodies to G-IV and G-V viruses. In conclusion, we produced a vaccine candidate capable of protection against the G-VIII virus in the vaccine experiment for the type Asia1 serotype vaccine. This Shamir-R vaccine virus was found to protect against the viruses of the Asia1 genotype G-VII and G-VIII lineages, which occurred recently in Asia.

Genotyping and pathogenic characterization of canine distemper virus based on mutations in the hemagglutinin gene in Chinese domestic dogs.

Canine distemper virus (CDV) infects wild and domestic Canidae worldwide. The hemag- glutinin (H) gene has the highest genetic variation in the genome of this virus. Thus, the H gene is commonly used for lineage identification and genetic analyses. In order to study the genetic characteristics and pathogenicity of CDV strains prevalent in China, 132 samples were collected from domestic dogs with suspected CDV infection, 58 samples were confirmed to be positive, and the H gene was successfully amplified from 15 samples. The epidemic strain was identified as type Asia-1 and the novel mutations, A51T, V58I, R179K and D262N, were detected in this strain. Isolated strains, BJ16B53, BJ16B14, and BJ17B8, were used for an animal infection experiment in raccoon dogs. BJ16B53 and BJ16B14 were found to cause clinical symptoms, death, and exten- sive lesions in various organs. These results are expected to facilitate the development of effective strategies to monitor and control CDV infection in China.

Foot-and-mouth disease virus type O specific mutations determine RNA-dependent RNA polymerase fidelity and virus attenuation

Previous studies have shown that the FMDV Asia1/YS/CHA/05 high-fidelity mutagen-resistant variants are attenuated (Zeng et al., 2014). Here, we introduced the same single or multiple-amino-acid substitutions responsible for increased 3Dpol fidelity of type Asia1 FMDV into the type O FMDV O/YS/CHA/05 infectious clone. The rescued viruses O-DA and O-DAMM are lower replication fidelity mutants and showed an attenuated phenotype. These results demonstrated that the same amino acid substitution of 3Dpol in different serotypes of FMDV strains had different effects on viral fidelity. In addition, nucleoside analogues were used to select high-fidelity mutagen-resistant type O FMDV variants. The rescued mutagen-resistant type O FMDV high-fidelity variants exhibited significantly attenuated fitness and a reduced virulence phenotype. These results have important implications for understanding the molecular mechanism of FMDV evolution and pathogenicity, especially in developing a safer modified live-attenuated vaccine against FMDV.

The VP1 S154D mutation of type Asia1 foot-and-mouth disease virus enhances viral replication and pathogenicity

One of the proteins encoded by the foot-and-mouth disease virus (FMDV), the VP1 protein, a capsid protein, plays an important role in integrin receptor attachment and humoral immunity-mediated host responses. The integrin receptor recognition motif and an important antigenic epitope exist within the G–H loop, which is comprised of amino acids 134–160 of the VP1 protein. FMDV strain, Asia1/HN/CHA/06, isolated from a pig, was passaged four times in suckling mice and sequenced. Sequencing analyses showed that there was a mutation of the integrin receptor recognition motif Arg-Gly-Asp/Arg-Asp-Asp (RGD/RDD, VP1 143–145) and a VP1 154 serine/Asp (VP1 S154D) mutation in the G–H loop of the VP1 protein. The influence of the RGD/RDD mutation on Asia1 FMDV disease phenotype has been previously studied. In this study, to determine the influence of the VP1 S154D mutation on FMDV Asia1 replication and pathogenicity, two recombinant FMDVs with different residues only at the VP1 154 site were rescued by reverse genetics techniques and their infectious potential in host cells and pathogenicity in pigs were compared. Our data indicates that the VP1 S154D mutation increases the replication level of FMDV Asia1/HN/CHA/06 in BHK-21, IB-RS-2, and PK-15 cells and enhances pathogenicity in pigs. Through the transient transfection-infection assay to compare integrin receptor usage of two recombinant viruses, the result shows that the VP1 S154D mutation markedly increases the ability of type Asia1 FMDV to use the integrin receptors αυβ6 and αυβ8 from pig. This study identifies a key research target for illuminating the role of residues located at G–H loop in FMDV pathogenicity.

Recovery of infectious type Asia1 foot-and-mouth disease virus from suckling mice directly inoculated with an RNA polymerase I/II-driven unidirectional transcription plasmid

We developed an RNA polymerase (pol) I- and II-driven plasmid-based reverse genetics system to rescue infectious foot-and-mouth disease virus (FMDV) from cloned cDNA. In this plasmid-based transfection, the full-length viral cDNA was flanked by hammerhead ribozyme (HamRz) and hepatitis delta ribozyme (HdvRz) sequences, which were arranged downstream of the two promoters (cytomegalovirus (CMV) and pol I promoter) and upstream of the terminators and polyadenylation signal, respectively. The utility of this method was demonstrated by the recovery of FMDV Asia1 HN/CHA/06 in BHK-21 cells transfected with cDNA plasmids. Furthermore, infectious FMDV Asia1 HN/CHA/06 could be rescued from suckling mice directly inoculated with cDNA plasmids. Thus, this reverse genetics system can be applied to fundamental research and vaccine studies, most notably to rescue those viruses for which there is currently an absence of a suitable cell culture system.

Re-emergence of circulatory foot-and-mouth disease virus serotypes Asia1 in Bangladesh and VP1 protein heterogeneity with vaccine strain IND 63/72.

Foot-and-mouth disease virus (FMDV) serotypes O, A and Asia1 are responsible for significant number of disease outbreaks in Bangladesh; however serotype Asia1 has not been reported in circulation since 1996. The present investigation reports the detection of serotype FMDV Asia1 from local farms in 2012 and 2013 outbreaks. The farms were located in Jessore and Gazipur districts, and one of these farms was under vaccine control programme. Phylogenetic analysis of the complete VP1 gene revealed that FMDV Asia1 is under genetic lineage C having close similarity to the Asia1 sequences of Indian origin. The circulatory genotype Asia1 showed VP1 protein sequence heterogeneity of eight amino acid substitutions within the G-H loop with the vaccine strain [IND 63/72 (AY304994)] used in vaccination programme. ELISA assay revealed that, of seven, only one local field serum sample (cattle vaccinated 38 days earlier) was positive at a titre level of >2.4 (log10) but failed to protect the cattle from infection occurred by the virus. This investigation focused that the eight amino acid substitution in VP1 protein at G-H loop of the locally circulated FMDV serotype Asia1 strain may be a reason for current vaccination failure.

Single amino acid substitution of VP1 N17D or VP2 H145Y confers acid-resistant phenotype of type Asia1 foot-and-mouth disease virus.

Infection by foot-and-mouth disease virus (FMDV) is triggered by the acidic pH in endosomes after virus uptake by receptor-mediated endocytosis. However, dissociation of the FMDV 146S particle in mildly acidic conditions renders inactivated foot-and-mouth disease (FMD) vaccines much less effective. Type Asia1 FMDV mutants with increased resistance to acid inactivation were selected to study the molecular basis of viral resistance to acid-induced disassembly and improve the acid stability of FMDV. Sequencing of capsid-coding regions revealed four amino acid replacements (VP1 N17D, VP2 H145Y, VP2 G192D, and VP3 K153E) in the viral population of the acid-selected 10th passage. We performed single or combined mutagenesis using a reverse genetic system, and our results provide direct experimental evidence that VP2 H145Y or VP1 N17D substitution confers an acid-resistant phenotype to type Asia1 FMDV.

Serological responses after vaccination of growing pigs with foot-and-mouth disease trivalent (type O, A and Asia1) vaccine

Korea experienced its fifth Foot-and-Mouth Disease (FMD) outbreak (type O) since 1934 from November 2010 to April 2011. The Korean government initiated emergency vaccination for all FMD-susceptible domestic animals in December 2010 using type O FMD vaccines. Starting in September 2011, trivalent FMD vaccines (types O, A, and Asia1) were used for the vaccination of all animals. This study was performed to identify the appropriate time for FMD vaccination in growing pigs when vaccination is applied only once (at either 8 weeks or 12 weeks of age). Seroprevalences from growing pigs under different vaccination regimens (once or twice) were also studied. A total of 526 growing pigs on 7 farms were used in this study. This study showed that the vaccination of growing pigs at both 8 and 12 weeks of age resulted in higher seroprevalences (97.5% in type O, 92.3% in type A and 99.4% in type Asia1) than did a single vaccination at 8 weeks of age (86.7% in type O, 88.0% in type A and 93.0% in type Asia1) (P<0.05). Pigs vaccinated once at 8 weeks of age showed much higher seroprevalences than pigs vaccinated once at 12 weeks of age (60.9% in type O, 62.8% in type A and 77.6% in Asia1, respectively) (P<0.05).

Recombinant adenovirus expressing type Asia1 foot-and-mouth disease virus capsid proteins induces protective immunity against homologous virus challenge in mice

Foot-and-mouth disease (FMD) is a highly contagious disease worldwide affecting cloven-hoofed animals that is caused by foot-and-mouth disease virus (FMDV). The FMDV capsid polyprotein and 3C proteinase are required for capsid precursor processing and assembly. The FMDV capsid protein, which contains the entire repertoire of immunogenic sites, can stimulate both humoral immunity and T-cell-mediated immune responses. In this study, we constructed a recombinant adenovirus, rAdV-Asi-05, that expresses the P1–2A and 3C genes of the type Asia1 FMDV strain Asia1/YS/CHA/05. The humoral immune responses elicited by the Ad5-vectored capsid protein of type Asia1 FMDV in BALB/c mice and the ability of rAdV-Asi-05 to rapidly induce protection against challenge with FMDV Asia1/YS/CHA/05 in C57BL/6 mice were evaluated. The processing of polyprotein P1 into the structural proteins VP0, VP3, and VP1 in rAdV-Asi-05-infected HEK 293 cells was detected by Western blotting. BALB/c mice immunised with rAdV-Asi-05 produced type Asia1 FMDV-specific neutralising antibodies, and the neutralisation titres increased significantly after the boost. Importantly, C57BL/6 mice immunised with a single 107 PFU dose of rAdV-Asi-05 exhibited protective immunity against challenge with 100 times the lethal dose of FMDV Asia1/YS/CHA/05. In summary, rAdV-Asi-05 elicited a high titre of neutralising antibodies against type Asia1 FMDV in BALB/c mice. Moreover, rAdV-Asi-05 provided complete protection against FMDV Asia1/YS/CHA/05 challenge in C57BL/6 mice. This study highlights the potential of rAdV-Asi-05 to serve as a type Asia1 FMDV vaccine.

Adenovirus-vectored type Asia1 foot-and-mouth disease virus (FMDV) capsid proteins as a vehicle to display a conserved, neutralising epitope of type O FMDV

The objective of this study was to explore the immunogenicity of an adenovirus construction expressing a type O foot and mouth disease virus neutralising epitope (8E8) in the context of heterologous capsid proteins. Adenoviruses expressing four chimeric type Asia1 FMDV capsid proteins were constructed by inserting the type O FMDV 8E8 epitope into the G-H loop from the type Asia1 VP1 at amino acid residues 139/140, 150/151, 134/140 or at both 139/140 and 150/151. These recombinant proteins were recognised by antibodies against the type O 8E8 epitope and type Asia1 FMDV. When inoculated in mice, all of the recombinant chimeric capsid proteins for each single epitope insertion induced the production of anti-type O FMDV neutralising antibodies. The recombinant chimeric capsid proteins with a foreign insertion at position 139/140 or 150/151 induced high levels of anti-type Asia1 FMDV neutralising antibodies as the recombinant type Asia1 capsid proteins without any foreign epitope, suggesting that the foreign insertion did not affect the immunogenicity of the type Asia1 FMDV capsid proteins. This study suggests that a foreign epitope displayed on the surface of the FMDV capsid proteins could induce an epitope-specific response. Therefore, the adenovirus-vectored FMDV capsid proteins could be used as a vehicle for the development of an epitope-based vaccine.

Insertion of type O-conserved neutralizing epitope into the foot-and-mouth disease virus type Asia1 VP1 G-H loop: effect on viral replication and neutralization phenotype

Previously, we finely mapped the neutralizing epitopes recognized by foot-and-mouth disease virus (FMDV) type Asia1-specific mAb 3E11 and FMDV type O-specific mAb 8E8. In this study, we engineered recombinant FMDVs of the serotype Asia1 (rFMDVs) displaying the type O-neutralizing epitope recognized by the mAb 8E8. These epitope-inserted viruses were genetically stable and exhibited growth properties that were similar to those of their parental virus. Importantly, the recombinant virus rFMDV-C showed neutralization sensitivity to both FMDV type Asia1 and type O mAbs, as well as to polyclonal antibodies. These results indicated that this epitope-inserted virus has the potential to induce neutralizing antibodies against both FMDV type Asia1 and type O. Our results demonstrated that the G-H loop of FMDV type Asia1 effectively displays the protective neutralizing epitopes of other FMDV serotypes, making this an attractive approach for the design of novel FMDV vaccines.

Molecular characterization of serotype Asia-1 foot-and-mouth disease viruses in Pakistan and Afghanistan; emergence of a new genetic Group and evidence for a novel recombinant virus

Foot-and-mouth disease (FMD) is endemic in Pakistan and Afghanistan. The FMD virus serotypes O, A and Asia-1 are responsible for the outbreaks in these countries. Diverse strains of FMDV, even within the same serotype, co-circulate. Characterization of the viruses in circulation can facilitate appropriate vaccine selection and tracing of outbreaks.The present study characterized foot-and-mouth disease serotype Asia-1 viruses circulating in Pakistan and Afghanistan during the period 1998–2009. Phylogenetic analysis of FMDV type Asia-1 revealed that three different genetic Groups of serotype Asia-1 have circulated in Pakistan during this time. These are Group-II, -VI and, recently, a novel Group (designated here as Group-VII). This new Group has not been detected in neighbouring Afghanistan during the study period but viruses from Groups I and -II are in circulation there. Using near complete genome sequences, from FMD viruses of serotypes Asia-1 and A that are currently circulating in Pakistan, we have identified an interserotypic recombinant virus, which has the VP2-VP3-VP1-2A coding sequences derived from a Group-VII Asia-1 virus and the remainder of the genome from a serotype A virus of the A-Iran05AFG-07 sub-lineage. The Asia-1 FMDVs currently circulating in Pakistan and Afghanistan are not efficiently neutralized by antisera raised against the Asia-1/Shamir vaccine strain. Thus, new Asia-1 vaccine strains may be required to block the spread of the current Asia-1 viruses.

Development of a serotype colloidal gold strip using monoclonal antibody for rapid detection type Asia1 foot-and-mouth disease

BackgroundIn this study, we developed a rapid, one step colloid gold strip (CGS) capable of specifically detecting type Asia1 foot-and-mouth disease virus (FMDV). We have produced two monoclonal antibodies (mAb) to type Asia1 FMD (named 1B8 and 5E2). On the test strip, the purified 1B8 labelled with the colloidal gold was used as the detector, and the purified 5E2 and goat anti-mouse antibodies were wrapped onto nitrocellulose (NC) membranes as the test and the control line, respectively. The rapid colloidal gold stereotype diagnostic strip was housed in a plastic case.ResultsIn specificity and sensitivity assay, there was no cross-reaction of the antigen with the other type of FMD and SVDV. The detection sensitivity was found to be as high as 10-5 dilution of Asia1/JSL/05 (1 × 107.2TCID50/50 μL). There was excellent agreement between the results obtained by CGS and reverse indirect hemagglutination assay (RIHA), and the agreement can reach to 98.75%.ConclusionWe developed colloidal gold strips that have good qualities and does not require specialized equipment or technicians. This method provided a feasible, convenient, rapid, and effective for detecting type Asia1 FMDV in the fields.

In-vitro and in-vivo phenotype of type Asia 1 foot-and-mouth disease viruses utilizing two non-RGD receptor recognition sites

BackgroundFoot-and-mouth disease virus (FMDV) uses a highly conserved Arg-Gly-Asp (RGD) triplet for attachment to host cells and this motif is believed to be essential for virus viability. Previous sequence analyses of the 1D-encoding region of an FMDV field isolate (Asia1/JS/CHA/05) and its two derivatives indicated that two viruses, which contained an Arg-Asp-Asp (RDD) or an Arg-Ser-Asp (RSD) triplet instead of the RGD integrin recognition motif, were generated serendipitously upon short-term evolution of field isolate in different biological environments. To examine the influence of single amino acid substitutions in the receptor binding site of the RDD-containing FMD viral genome on virus viability and the ability of non-RGD FMDVs to cause disease in susceptible animals, we constructed an RDD-containing FMDV full-length cDNA clone and derived mutant molecules with RGD or RSD receptor recognition motifs. Following transfection of BSR cells with the full-length genome plasmids, the genetically engineered viruses were examined for their infectious potential in cell culture and susceptible animals.ResultsAmino acid sequence analysis of the 1D-coding region of different derivatives derived from the Asia1/JS/CHA/05 field isolate revealed that the RDD mutants became dominant or achieved population equilibrium with coexistence of the RGD and RSD subpopulations at an early phase of type Asia1 FMDV quasispecies evolution. Furthermore, the RDD and RSD sequences remained genetically stable for at least 20 passages. Using reverse genetics, the RDD-, RSD-, and RGD-containing FMD viruses were rescued from full-length cDNA clones, and single amino acid substitution in RDD-containing FMD viral genome did not affect virus viability. The genetically engineered viruses replicated stably in BHK-21 cells and had similar growth properties to the parental virus. The RDD parental virus and two non-RGD recombinant viruses were virulent to pigs and bovines that developed typical clinical disease and viremia.ConclusionsFMDV quasispecies evolving in a different biological environment gained the capability of selecting different receptor recognition site. The RDD-containing FMD viral genome can accommodate substitutions in the receptor binding site without additional changes in the capsid. The viruses expressing non-RGD receptor binding sites can replicate stably in vitro and produce typical FMD clinical disease in susceptible animals.

Isolation, identification and complete genome sequence analysis of a strain of foot-and-mouth disease virus serotype Asia1 from pigs in southwest of China

BackgroudFoot-and-mouth disease virus (FMDV) serotype Asia1 generally infects cattle and sheep, while its infection of pigs is rarely reported. In 2005-2007, FMD outbreaks caused by Asia1 type occurred in many regions of China, as well as some parts of East Asia countries. During the outbreaks, there was not any report that pigs were found to be clinically infected.ResultsIn this study, a strain of FMDV that isolated from pigs was identified as serotype Asia1, and designated as "Asia1/WHN/CHA/06". To investigate the genomic feature of the strain, complete genome of Asia1/WHN/CHA/06 was sequenced and compared with sequences of other FMDVs by phylogenetic and recombination analysis. The complete genome of Asia1/WHN/CHA/06 was 8161 nucleotides (nt) in length, and was closer to JS/CHA/05 than to all other strains. Potential recombination events associated with Asia1/WHN/CHA/06 were found between JS/CHA/05 and HNK/CHA/05 strains with partial 3B and 3C fragments.ConclusionThis is the first report of the isolation and identification of a strain of FMDV type Asia1 from naturally infected pigs. The Asia1/WHN/CHA/06 strain may evolve from the recombination of JS/CHA/05 and HNK/CHA/05 strains.