Molecular characterization of porcine circovirus 2 circulating in Assam and Arunachal Pradesh of India

Development of recombinant capsid protein-based single serum dilution ELISA for sero-detection of porcine circovirus type 2 infection in pigs

Porcine Circovirus 2 (PCV2) is the major causative agent of postweaning multisystemic wasting syndrome (PMWS) of swine and is one of the reasons for severe economic loss in swine industry. In India, there is a considerable prevalence rate of PCV2 infection in pig population, PCV2d being the most prominent genotype. Proper sero-diagnosis and sero-surveillance of the disease is formulated as an effective control measure. In this study, a recombinant capsid protein-based single serum dilution indirect ELISA was developed for determination of antibody titre of the infected pigs. The capsid protein (Cap) of PCV2d was produced in Saccharomyces cerevisiae cells and the capsid protein was purified by affinity chromatography. This recombinant protein was used as a coating antigen to develop a cost effective, highly sensitive and specific single serum dilution ELISA. The in-house developed ELISA was optimized to be used in a 1:200 single serum dilution. The developed ELISA along with a commercial ELISA kit were compared with a sensitive immuno-peroxidase assay (IPMA) by receiver-operating characteristics (ROC) test. Our results showed that the developed single serum dilution ELISA had a higher sensitivity and specificity in comparison to the commercial ELISA. The area under the ROC curve (AUC) also confirmed that the developed ELISA had a better overall diagnostic performance in comparison to the commercial ELISA kit.

Co-circulation and genetic characteristics of porcine circoviruses in postweaning multisystemic wasting syndrome cases in commercial swine farms

This study aimed to investigate the co-infection and genetic characteristics of Porcine circoviruses in PMWS-affected pigs in five commercial farrow-to-finish swine farms in Vietnam. By the end of 2022, the percentage of PMWS-affected pigs in these farms has increased significantly compared to previous years. The lymph node samples from ten PMWS typical cases were randomly collected to test for the presence of PRRSV, PCV2, PCV3 and PCV4. While PRRSV and PCV4 were not found in these cases, 10 and 3 out of 10 samples were positive for PCV2 and PCV3, respectively. Three farms in the study showed the co-infection of PCV2 and PCV3 in affected pigs. Besides, all PCV-positive samples were sequenced to evaluate genetic characterization of PCVs in PMWS-affected cases. Phylogenetic analysis showed that all PCV3 strains in the study were clustered into PCV3b genotype. 8 out of 10 PCV2 strains belonged to PCV2d genotype while the remaining two strains belonged to PCV2b genotypes. Two farms had co-circulation of PCV2b and PCV2d genotypes in two different age groups of pigs, which is reported for the first time in Vietnam. Several amino acid substitutions were identified in important antigenic regions in the capsid protein of the PCV2 field strains compared to vaccine strains. Taken together, the results showed the high co-prevalence of PCV3 and PCV2, and the wide genetic diversity of PCV2 field and vaccine strains may be the cause of the increased PMWS situation in these pig farms.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-023-00849-4.

Isolation and genetic analysis of Porcine circovirus 2 in southern India evidences high circulation of Porcine circovirus 2d genotype

BACKGROUND

Porcine circovirus 2 is globally noted swine pathogen with multiple genotypes associated with vast clinical and subclinical outcomes. This study aimed to isolate and characterize PCV2 genotypes circulating in southern states of India.

METHODS AND RESULTS

A total of 434 field samples comprising of serum (n = 273), tissues (n = 109) and swabs (n = 52) collected from swine during 2019 to 2021 from southern states of India were screened for PCV2 by specific polymerase chain reaction (PCR) assay. Molecular prevalence of PCV2 in southern India was found to be 12.21% (n = 53). All the 53 PCV2 positive samples were further subjected to the PCR assay with designed primers targeting full length amplification of ORF2 gene of PCV2 for molecular characterization. Randomly 32 positive samples by full length PCV2-ORF2 gene PCR were sequenced for genotyping. Signature motif and phylogenetic analysis of 32 PCV2 sequences revealed 62.5% (n = 20) prevalence of PCV2d genotype followed by 21.8% (n = 7) of PCV2h or PCV2-IM1 and 15.6% (n = 5) of PCV2b genotypes. Twenty five PCR positive field samples were subjected for virus isolation in PK15 cells and characterized. Out of 25 samples processed 5 (20%) PCV2 isolates obtained in this study were confirmed by PCR and immune fluorescence assay. Molecular characterization of PK15 adapted five PCV2 isolates confirmed circulation of PCV2d, PCV2h and PCV2b genotypes in pigs under field conditions in southern India.

CONCLUSIONS

Isolation and molecular epidemiological study of PCV2 in southern states of India evidences high circulation of PCV2d genotypes in field conditions in comparison to other genotypes.

Whole-Genome Sequence of a Porcine Circovirus Type 2 Strain Detected in Assam, India

Porcine circovirus-associated disease caused by porcine circovirus type 2 (PCV2) is a vital threat to the global pig industry. In this study, we have characterized the complete genome sequence of a PCV2 isolate, namely, Assam-01, belonging to the genotype PCV2d.