Genetic diversity in the capsid protein gene of porcine circovirus type 3 in Vietnam from 2018 to 2019.

Porcine circovirus type 3 (PCV3) was first detected in 2016 and has been reported in many pig-producing countries around the world, including Vietnam. PCV3 has been found in complex cases with multiple clinical syndromes in swine. In this study, we investigated the genetic diversity of PCV3 strains circulating in Vietnam. A total of 249 samples were collected from swine farms located in eight provinces of Vietnam, and 11.65% (29/249) of these samples were found to contain PCV3. The ORF2 genes from the 29 PCV3-positive samples were amplified, purified, and sequenced. Phylogenetic analysis showed that 23 of these strains belonged to the PCV3b subtype, while the remaining six strains belonged to subtype c and subtype a (a-1 and a-2). Analysis of the ORF2 genes indicated that the 29 PCV3 strains had high sequence identity (96.90-100% at the genomic level and 96.19-100% at the amino acid level). Fifteen amino acid substitutions were found in predicted B-cell epitopes in the capsid proteins of the Vietnamese PCV3 strains.

Development of optimized protocol for culturing African swine fever virus field isolates in MA104 cells.

The goal of this study was to identify a candidate commercial cell line for the replication of African swine fever virus (ASFV) by comparing several available cell lines with various medium factors. In the sensitivity test of cells, MA104 and MARC-145 had strong potential for ASFV replication. Next, MA104 cells were used to compare the adaptation of ASFV obtained from tissue homogenates and blood samples in various infectious media. At the 10th passage, the ASFV obtained from the blood sample had a significantly higher viral load than that obtained from the tissue sample (P = 0.000), exhibiting a mean cycle threshold (Ct) value = 20.39 ± 1.99 compared with 25.36 ± 2.11. For blood samples, ASFV grew on infectious medium B more robustly than on infectious medium A (P = 0.006), corresponding to a Ct value = 19.58 ± 2.10 versus 21.20 ± 1.47. African swine fever virus originating from blood specimens continued to multiply gradually and peaked in the 15th passage, exhibiting a Ct value = 14.36 ± 0.22 in infectious medium B and a Ct value = 15.42 ± 0.14 in infectious medium A. When ASFV was cultured from tissue homogenates, however, there was no difference (P = 0.062) in ASFV growth between infectious media A and B. A model was developed to enhance ASFV replication through adaptation to MA104 cells. The lack of mutation at the genetic segments encoding p72, p54, p30, and the central hypervariable region (CVR) in serial culture passages is important in increasing the probability of maintaining immunogenicity when developing a vaccine candidate.

L'objectif de cette étude était d'identifier une lignée cellulaire commerciale candidate pour la réplication du virus de la peste porcine africaine (ASFV) en comparant plusieurs lignées cellulaires disponibles et différents milieux. Lors du test de sensibilité des cellules, MA104 et MARC-145 présentaient un fort potentiel pour la réplication d'AFSV. Par la suite, les cellules MA104 ont été utilisées pour comparer l'adaptation d'ASFV obtenu d'homogénats de tissus et d'échantillons de sang dans différents milieux. Au dixième passage, l'ASFV obtenu de l'échantillon de sang avait une charge virale significativement plus élevée que celle obtenue de l'échantillon de tissu (P = 0,000), avec une valeur seuil moyenne de cycles (Ct) de 20,39 ± 1,99 comparativement à 25,36 ± 2,11. Pour les échantillons sanguins, l'ASFV a poussé sur le milieu B de manière plus robuste que sur le milieu A (P = 0,006), ce qui correspond à une valeur Ct de 19,58 ± 2,10 versus 21,20 ± 1,47. L'ASFV provenant des échantillons sanguins continua de se multiplier graduellement et atteignit un pic au 15e passage, avec une valeur Ct de 14,36 ± 0,22 dans le milieu B et une valeur Ct de 15,42 ± 0,14 dans le milieu A. Toutefois, lorsque l'ASFV fut cultivé à partir des homogénats de tissus, il n'y avait pas de différence (P = 0,062) dans la croissance d'ASFV entre les milieux A et B. Un modèle a été développé pour augmenter la réplication d'ASFV par adaptation aux cellules MA104. L'absence de mutation au segment génétique codant pour p72, p54, p30, et la région hypervariable centrale (CVR) dans des passages en série en culture est importante en augmentant la probabilité de maintenir une immunogénicité lors du développement d'un vaccin candidat.(Traduit par Docteur Serge Messier).

Phylogenetics and Pathogenicity of Balantioides coli Isolates in Vietnamese Weaned Pigs.

PURPOSE: This study aimed to investigate the diversity of Balantioides coli (B. coli) based on the 18S rDNA of isolates collected from weaned pigs with diarrhea and then select a B. coli isolate to determine its pathogenicity in weaned pigs through experimental infection. METHODS: The genetic analysis of field-isolated B. coli strains was based on sequencing of the partial 18S rDNA genetic fragment and the pathogenicity of an isolate of B. coli (DN2018-2-DTD) was identified through an experimental infection. RESULTS: The fourteen B. coli isolates shared 98.47-100% nucleotide similarity and were divided into two clades in a phylogenetic tree. In an infection experiment, a slight increase in the body temperature was identified in two infected groups as compared to that in the control group (P < 0.05) from days post-infection (dpi) 12-18 and from dpi 20-27. In the group infected with 3000 CPG/TPG, 2/9 pigs started to develop diarrhea on day two. In the group infected with 500 CPG/TPG, 8/9 pigs had diarrhea on dpi 3. Trophozoites/cysts of B. coli were firstly detected in feces on dpi 3 in a group of pigs infected with a dose of 3000 CPG/TPG, and CPG/TPG reached its peak at dpi 5 in both groups of infected pigs (35,450 and 13,250 CPG/TPG). There was a significant difference in the bodyweight of the control group (noninfected) as compared to that of the groups of infected pigs on dpi 7 (P < 0.05), 14 (P < 0.001) and 28 (P < 0.01). Lesions were solely recorded in infected pigs, including white ulcerative nodules with necrosis scattered in the mucosa of the colon and cecum on dpi 7, 14, and 28. CONCLUSION: This is the first study to investigate the pathogenicity of B. coli in Vietnamese pigs to demonstrate that B. coli could induce necrotic ulcerative enteritis and diarrhea in weaned pigs.