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Astroviruses (AstVs) are among the most important viruses causing diarrhea in human infants and many animals, posing a threat to public health safety and a burden on the economy. Five porcine AstV (PAstV) genotypes have been identified in various countries, including China. However, the epidemiology of PAstV in Yunnan province, China, remains unknown. In this study, 489 fecal samples from pigs in all 16 prefectures/cities of Yunnan were collected between April and August of 2020 for epidemiological investigation. The total infection rate of PAstV-2 or PAstV-5 was 39.9%, with suckling piglets having the highest infection rate (62.3%). The ORF2 genes of seven PAstV-2 and 10 PAstV-5 isolates were sequenced and phylogenetically analyzed. In addition to coinfections with PAstV-2 and PAstV-5, coinfections of PAstV with other diarrhea-inducing viruses (e.g., porcine bocavirus) were also discovered. A comparison of ORF2-encoded capsid protein sequences revealed that there were multiple insertions and deletions in the seven Yunnan PAstV-2 sequences, while point mutations, but no deletions or insertions, were found in the 10 Yunnan PAstV-5 sequences, which were very similar to the reference sequences. This is the first epidemiological investigation and genetic characterization of PAstV-2 and PAstV-5 in Yunnan province, China, demonstrating the current PAstV infection situation in Yunnan. [ABSTRACT FROM AUTHOR]

The intron-based stabilization approach is a very useful strategy for construction of stable flavivirus infectious clones. SA14-14-2 is a highly attenuated Japanese encephalitis (JE) live vaccine strain that has been widely used in China since 1989. To develop safe and effective recombinant vaccines with SA14-14-2 as a backbone vector, we constructed the DNA-based infectious clone pCMW-JEV of SA14-14-2 using the intron-based stabilization approach and acquired the rescued virus rDJEV, which retained the biological properties of the parental virus. Unexpectedly, a rescued virus strain with altered virulence, designated rHV-DJEV, was accidentally acquired in one of the transfection experiments. rHV-DJEV showed up to 105-fold increased neurovirulence compared with the SA14-14-2 parental strain. Genome sequencing showed that the inserted introns were still present in the genome of rHV-DJEV. Therefore, we think that the intron-based stabilization approach should be used with caution in vaccine development and direct iDNA immunization. [ABSTRACT FROM AUTHOR]