Species specificity and interspecies relatedness of NSP4 genetic groups by comparative NSP4 sequence analyses of animal rotaviruses

Abstract

Previous sequence analyses of the rotavirus nonstructural NSP4 from human and some animal rotavirus strains revealed the presence of three distinct NSP4 alleles or genetic groups. To examine the species of origin relatedness and diversity of NSP4, the nucleotide and deduced amino acid sequences of the gene encoding the NSP4 from 15 animal rotavirus strains of porcine, equine, bovine, lapine and canine origin were determined and compared to human and other animal strains sequenced previously. Lapine and equine strains were shown to belong to the NSP4 genotype A. Murine NSP4 sequences formed a previously unrecognized fourth distinct NSP4 genotype (genotype D) that was more divergent compared to NSP4 genotype A, B, and C than the latter three are among each other. Within NSP4 genotypes, strains isolated from rabbits, horses, cows (genotype A) and pigs (genotype B) clustered according to species of origin, suggesting a conserved pattern of evolution within species. NSP4 sequence comparison among one wildtype and two tissue culture-adapted lapine strains, known to cause disease in neonatal rabbits, failed to identify amino acid changes within the variable region spanning amino acids 130 to 141, suggesting that disease in rabbits is the result of the lapine virus infection and replication, including production of the NSP4 enterotoxin.

Genomic characterization of a novel group A lamb rotavirus isolated in Zaragoza, Spain

“…Newly established NSP4 genotype [5] and previously known NSP4 [6][7][8][9] genotype shown in parenthesis e NSP5 genotypes as recently described by Matthijnssens et al [5] of the NSP5/NSP6 of OVR762 with those of representative rotavirus strains ranged from 98% (buffalo rotavirus strain 10733, belonging to genotype H3) to 50% (avian strain PO-13, belonging to genotype H4). A high aa identity (94-96%) was also found to some HRV strains belonging to the genotype H3, and to genotype H3 BRV strains RF and APA12 and UK (97 and 94%, respectively).…”

“…3). The deduced aa sequence of the NSP4 of OVR762 exhibited 93-99% aa identity with ovine, bovine, simian, equine, and human rotavirus strains in the NSP4 genotype E2, previously knows as genotype A (Table 1, and data not shown) [5,7,10]. The NSP4 of OVR762 exhibited the greatest aa identity (99%) with the genotype E2 HRV strain PA589, isolated in Italy, while the range of aa identities to other HRV strain belonging to the same genotype E2 was 94-97%.…”

“…The non-structural glycoprotein NSP4, the viral enterotoxin, and recent sequence analyses have revealed that the NSP4 gene of group A rotaviruses may be genetically classified into 11 genotypes, E1 to E11 [5], which correspond to the five genotypes, KUN (A)-, Wa (B)-, Au-1 (C)-, EW (D)-, or avian (E)-like, described previously [6][7][8][9]. Within NSP4 genotypes E1 and E2, previously genotypes B and A, respectively, rotavirus strains generally cluster according to species of origin, suggesting a constant pattern of evolution within species [7].…”

“…The deduced aa sequence contained two potential N-linked glycosylation sites located at aa 8 and 18, two cysteine residues at aa 63 and 71, and histidine-131 (a key residue for enterotoxigenic activity) which are conserved in NSP4 proteins [7,10,21] (Fig. 3).…”

“…Within NSP4 genotypes E1 and E2, previously genotypes B and A, respectively, rotavirus strains generally cluster according to species of origin, suggesting a constant pattern of evolution within species [7]. Genome segment 11 encodes NSP5, a phosphoprotein with kinase activity, and, via an out-of-phase open reading frame (ORF), a smaller, likely dispensable protein, NSP6 [1].…”