Senecavirus A (SVA) is a major viral pathogen causing disease in pigs, and effective monitoring of SVA infection is critical for disease control. In this study, we aimed to develop a reliable ELISA method for rapidly detecting neutralizing antibodies against SVA. We used HEK293F cells to express an SVA-specific porcine Fab antibody and verified the biological activity of the Fab antibody by indirect ELISA, immunofluorescence assay, virus neutralization test, and Western blotting. The Fab antibody was biotinylated and used as a competitive antibody to establish a competitive ELISA (C-ELISA) for detecting neutralizing antibodies against SVA. We then evaluated the C-ELISA in terms of sensitivity, specificity, repeatability, and result agreement rate with the VNT. The results showed that we successfully prepared an SVA-specific porcine Fab antibody, which showed high affinity for SVA. We named this antibody 1M33Fab and designated it as Bio-1M33Fab after biotin labeling. The assay conditions were optimized as follows: the coating concentration of SVA particles being 1 μg/mL, the working concentration of Bio-1M33Fab being 0.5 μg/mL, the optimal serum dilution of 1:10, and the optimal dilution of enzyme-labeled avidin being 1:30 000. At a percent inhibition (PI) of 47%, the assay demonstrated the highest sensitivity (96.88%) and specificity (100%), with no cross-reactivity observed with the positive sera of major porcine viral diseases. The intra-assay coefficient of variation ranged from 1.12% to 7.34%, while the inter-assay coefficient of variation ranged from 1.10% to 8.97%, indicating good repeatability. In the detection of 224 clinical pig serum samples, C-ELISA and VNT showed a result agreement rate of 93.75%. In conclusion, we successfully develop a C-ELISA method for detecting neutralizing antibodies against SVA by using a porcine-derived Fab antibody, which lays a foundation for the development of detection kits.
Animals ; Swine ; Antibodies, Neutralizing/immunology* ; Enzyme-Linked Immunosorbent Assay/methods* ; Immunoglobulin Fab Fragments/immunology* ; Antibodies, Viral/immunology* ; Picornaviridae/immunology* ; Humans ; HEK293 Cells ; Swine Diseases/diagnosis* ; Picornaviridae Infections/diagnosis*

Antibodies, Viral ; analysis ; Cerebrospinal Fluid ; virology ; Child ; Child, Preschool ; Feces ; virology ; Genotype ; Humans ; Infant ; Meningoencephalitis ; diagnosis ; virology ; Parechovirus ; classification ; genetics ; isolation & purification ; Picornaviridae Infections ; diagnosis ; epidemiology ; virology ; RNA, Viral ; genetics ; Respiratory Tract Infections ; diagnosis ; virology ; Sepsis ; diagnosis ; virology ; Sequence Analysis, DNA

OBJECTIVEHuman rhinovirus (HRV) is the most common respiratory pathogen, which causes not only acute respiratory infection and community acquired pneumonitis in children, but also asthma episode and deterioration. However, the detection of respiratory pathogen, which mainly focuses on respiratory syncytial virus, influenzaviruses A and B, parainfluenza viruses 1-3 and adenoviruses, does not include HRV yet by now in China. The absence of detection method limits the clinical understanding of HRV pathogenicity, and causes unreasonable use of antibiotics. This study aimed to establish a one-step reverse transcription (RT) PCR system for detecting specific fragment of HRV RNA, and to analyze the sequences of amplicons.

METHODSA pair of degenerate primers based on the HRV highly conserved 5'' noncoding region (NCR) were used to develop a one-step RT-PCR system for detecting HRV RNA in nasopharyngeal aspirates from 78 children with acute respiratory tract infections in the spring of 2004. All the positive PCR products were sequenced, and the sequences of the nucleotides were analyzed by using biological software and compared with those in the GeneBank.

RESULTSEleven (14.1%) of 78 samples were positive on RT-PCR, these patients were clinically diagnozed as upper respiratory tract infection (n = 7), bronchitis (n = 3) and bronchopneumonia (n = 1), respectively. Compared with the sequences of clinical and standard HRV viruses in the GeneBank, the nucleotide sequences of these 11 amplicons shared high homology of 89%-95.5%. Within the 11 amplicons, nucleotide identity varied from 75.2% to 91.8%, and the ratio of genetic variation was from 8.8% to 31.0%, which occurred in highly conserved regions and usually showed single nucleotide mutation in some special locations. These 11 amplicons attribute to the two branches of HRV cladogram, respectively. Most of mutations in highly conservative domain occurred on single ribonucleotide, mainly as transversion (C/G, A/G) and transition (T/C, A/G), some were mutations among 3 bases (A/C/G, A/T/G, A/C/T). And a few mutations involved two nearby ribonucleotide which were also found in highly conservative domain. However, ribonucleotide deletion and insertion were usually found in highly variable domain.

CONCLUSIONThe findings showed that this one-step RT-PCR system was highly specific, rapid and convenient for the detection of HRV RNA in nasopharyngeal secretions of patients with acute respiratory tract infections and that the genome of HRV viruses was highly variable.

Base Sequence ; Child ; Child, Preschool ; Female ; Genes, Viral ; Humans ; Male ; Molecular Sequence Data ; Picornaviridae Infections ; diagnosis ; virology ; RNA, Viral ; analysis ; Respiratory Tract Infections ; virology ; Reverse Transcriptase Polymerase Chain Reaction ; methods ; Rhinovirus ; genetics ; isolation & purification ; Sensitivity and Specificity ; Sequence Analysis, DNA

Child ; Herpesviridae ; classification ; Herpesviridae Infections ; diagnosis ; Humans ; Paramyxoviridae ; classification ; Paramyxoviridae Infections ; diagnosis ; Parechovirus ; classification ; Pediatrics ; Picornaviridae ; classification ; Picornaviridae Infections ; diagnosis ; SARS Virus ; classification ; Severe Acute Respiratory Syndrome ; diagnosis ; Virus Diseases ; diagnosis ; Viruses ; classification