THE ORF5 VARIATION OF VIETNAMESE PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS STRAINS

Porcine reproductive and respiratory syndrome is a devastating disease that causes heavy losses to the economy and the development of agriculture. In this study, we aimed to assess the genetic variation of the ORF5 gene from 12 Vietnamese porcine reproductive and respiratory syndrome virus (PRRSV) strains. The phylogenetic analysis of the ORF5 sequences of Vietnamese strains and other strains indicated that the Vietnamese strains belong to type II. The Vietnamese strains were also separated into two clusters. Five strains BG/12, TG1/12, TG2/12, TG3/12, and TG4/12 were grouped in cluster 1 with a 98% bootstrap value, while the other seven strains HCM/14, TG5/15, TG6/15, TG7/15, ST1/15, ST2/15, and ST3/15 belonged to cluster 2. The alignment of the deduced amino acid sequences demonstrated that the identity between Vietnamese strains with CH-1a, JXA1, and VR2332 strains were 87–93%, 91–98%, and 83–89%, respectively. The mutation of the N21 glycosylation site (N→S) of the GP5 sequence was observed in five Vietnamese strains from cluster 1. The core sequence of the neutralizing epitopes (including five positions at H25, Q27, I29, Y30, and N31) in GP5 was presented in all Vietnamese strains except strain TG1/12. The hydrophobicity plots of GP5 revealed two different positions of BG/12 strain from CH-1a strain and VR2332 strain. The first difference was the missing of a hydrophilic peak from position amino acid 85 to 95. In this region, the CH-1a and VR2332 strains have 3 hydrophilic peaks. The second difference was the loss of another hydrophilic peak at position amino acid 100. Key words: genotype; ORF5; phylogenetics; PRRSV; Vietnam RAZNOLIKOST GENA ORF5 V SEVIH VIRUSA VIETNAMSKEGA PRAŠIČJEGA RESPIRATORNEGA IN REPRODUKTIVNEGA SINDROMA Prašičji respiratorni in reproduktivni sindrom je huda bolezen, ki povzroča velike izgube v gospodarstvu in vpliva na razvoj kmetijstva. V raziskavi smo želeli oceniti gensko raznolikost gena ORF5 v 12 sevih virusa vietnamskega prašičjega respiratornega in reproduktivnega sindroma (PRRSV). Filogenetska analiza baznih zaporedij ORF5 vietnamskih in drugih sevov je pokazala, da vietnamski sevi pripadajo tipu II. Tudi vietnamski sevi so bili ločeni v dve skupini. Pet sevov (BG/12, TG /12, TG2/12, TG3/12 in TG /12) je bilo združenih v skupino 1 z 98-odstotno vrednostjo bootstrap, medtem ko je bilo ostalih sedem sevov (HCM/14, TG5/15, TG6/15, TG7/15, ST1/15, ST2/15 in ST3/15) uvrščenih v drugo skupino. Poravnava zaporedij aminokislin je pokazala, da je podobnost med vietnamskimi sevi in sevi CH-1a 87−93-odstotna, JXA1 91−98-odstotna in VR2332 83−89-odstotna. Pri petih vietnamskih sevih iz skupine 1 smo opazili mutacijo mesta z glikozilacijo N21 (N → S) zaporedja GP5. Glavno zaporedje nevtralizacijskih epitopov (vključno s petimi položaji pri H25, Q27, I29, Y30 in N31) v GP5 je bilo opaženo pri vseh vietnamskih sevih, razen v sevu TG1/12. Grafikoni hidrofobnosti GP5 so pokazali dva različna položaja BG/12 iz CH-1a in VR2332 sevov. Prva razlika je bila odsotnost hidrofilnega vrha pri položaju aminokislin 85 do 95. V tem področju so imeli sevi CH-1a in VR2332 tri hidrofilne vrhove. Druga razlika je bila izguba drugega hidrofilnega vrha na položaju aminokisline 100. Ključne besede: genotip; ORF5; filogenetika; PRRSV; Vietnam