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This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Viruses are able to evolve in vitro by mutations after serial passages in cell cultures, which can lead to either a loss, or an increase, of virulence. Cyprinid herpesvirus 3 (CyHV-3), a 295-kb double-stranded DNA virus, is the etiological agent of the koi herpesvirus disease (KHVD). To assess the influence of serial passages, an isolate of CyHV-3 (KHV-T) was passaged 99 times onto common carp brain (CCB) cells, and virus virulence was evaluated during passages through the experimental infections of common carp. After 78 CCB passages, the isolate was much less virulent than the original form. A comparative genomic analysis of these three forms of KHV-T (P0, P78 and P99) revealed a limited number of variations. The largest one was a deletion of 1363 bp in the predicted ORF150, which was detected in P78, but not in P99. This unexpected finding was confirmed by conventional PCR and digital PCR. The results presented here primarily suggest that, CyHV-3 evolves, at least in vitro, through an assemblage of haplotypes that alternatively become dominant or under-represented.

Penelitian dengan tujuan untuk mengetahui efikasi berbagai sediaan (biakan cair, sel utuh, supernatan dengan dan tanpa penyaringan) vaksin Streptococcus agalactiae-N14G untuk pencegahan penyakit Streptococcosis pada ikan nila telah dilakukan pada skala laboratorium. Isolat bakteri Streptococcus agalactiae-N14G digunakan sebagai sumber antigen dalam pembuatan vaksin. Ikan nila dengan rata-rata ukuran 10-15 g/ekor dan diasumsikan bebas penyakit infeksi Streptococcus agalactiae (specific pathogen free, SPF) terhadap patogen target digunakan sebagai ikan uji. Pada hari ke-14 pasca vaksinasi, dilakukan uji tantang dengan bakteri homolog aktif pada dosis lethal (LD50), dan pengamatan dilakukan selama 21 hari. Hasil penelitian menunjukkan efikasi sediaan vaksin tertinggi diperoleh pada sediaan vaksin sel utuh (B) (76,0%), selanjutnya diikuti oleh sediaan vaksin biakan cair (A) (65,0%), sediaan vaksin supernatan tanpa penyaringan (C) (49,0%), dan sediaan vaksin dengan penyaringan (D) (36,0%); sedangkan pada kelompok kontrol positif dan negatif, masingmasing sebesar 25,0% dan 34,0%. Dua jenis sediaan vaksin masuk kategori efektif dengan nilai relative percentage survival (RPS) 8 50%, yaitu jenis vaksin sel utuh(68,00%) dan jenis sediaan vaksin biakan cair (53,37%).