Infectious hypodermal and hematopoietic necrosis virus from Brazil: Sequencing, comparative analysis and PCR detection.

A 3739 nucleotide fragment of Infectious hypodermal and hematopoietic necrosis virus (IHHNV) from Brazil was amplified and sequenced. This fragment contains the entire coding sequences of viral proteins, the full 3' untranslated region (3'UTR) and a partial sequence of 5' untranslated region (5'UTR). The genome organization of IHHNV revealed the three typical major coding domains: a left ORF1 of 2001 bp that codes NS1, a left ORF2 (NS2) of 1091 bp that codes NS2 and a right ORF3 of 990 bp that codes VP. Nucleotide and amino acid sequences of the three viral proteins were compared with putative amino acid sequences of viruses reported from different regions. Comparisons among genomes from different geographic locations reveal 31 nucleotide regions that are 100% similar, distributed throughout the genome. An analysis of secondary structure of UTR regions, revealed regions with high probability to form hairpins, that may be involved in mechanisms of viral replication. Additionally, a maximum likelihood analysis indicates that Brazilian IHHNV belongs to lineage III, in the infectious IHHNV group, and is clustered with IHHNV isolates from Hawaii, China, Taiwan, Vietnam and South Korea. A new nested PCR targeting conserved nucleotide regions is proposed to detect IHHNV.