ABSTRACT
In recent years interest in the family Iridoviridae has been renewed by the identification of a number of viruses, particularly from the genus Ranavirus, associated with disease in a range of poikilotherms. Ranaviruses have been isolated from amphibian, piscine and reptilian species. Here we describe an open reading frame (ORF) identified in the genome of Bohle iridovirus (BIV) which contains a nucleotide binding motif conserved within the thymidine kinase (TK) genes of iridoviruses from other genera (lymphocystis disease virus, LCDV, type species of the genus Lymphocystivirus; Chilo iridescent virus, CIV, type species of the genus Iridovirus). The ability of this putative gene to express a functional TK was confirmed by rescue of a TK negative mutant vaccinia virus in the presence of selective media, when expression was controlled by a vaccinia virus promoter. The sequence of the BIV TK was compared with the homologous sequences from epizootic haematopoietic necrosis virus (EHNV), a virus associated with disease in fish, from Wamena iridovirus (WIV) associated with systemic disease in green pythons, and from frog virus 3 (FV3) the ranavirus type species. Comparisons between these sequences and those available from other ranaviruses, other iridoviruses, other DNA viruses and cellular TKs are presented.
Subject(s)
Iridoviridae/genetics , Thymidine Kinase/genetics , Thymidine Kinase/metabolism , Amino Acid Sequence , Base Sequence , Binding Sites/genetics , Gene Expression , Genetic Vectors , Molecular Sequence Data , Open Reading Frames , Sequence Alignment , Sequence Homology, Amino Acid , Sequence Homology, Nucleic Acid , Vaccinia virus/metabolismABSTRACT
Restriction enzyme studies have been used to divide the fowl adenoviruses (FAV) into 5 groups - A, B,C,D and E. More detailed restriction enzyme studies of a series of group E FAV field isolates showed that these methods could differentiate between mildly and hypervirulent FAV belonging to this group. We have mapped the genomes of the hypervirulent (CFA 40) and two of the mildly virulent FAV (CFA 44 and CFA 3), using 11 different restriction enzymes: HindIII, BglII, XbaI, NdeI, SpeI, DraI, NotI, StuI, NheI, SfiI, and AvrII. Comparison of the three maps showed that the CFA 3 genome was approximately 3.5 kb smaller than that of CFA 44 and CFA 40. This size difference was discounted as a likely cause of the reduced pathogenicity of CFA 3 as the other mildly virulent virus, CFA 44, was the same size as the hypervirulent CFA 40. Other variations between the three viruses occurred in the region of the hexon and 100 K genes, but further studies are required to determine the significance of these variations in pathogenicity.
Subject(s)
Aviadenovirus/genetics , Chickens/virology , Animals , Aviadenovirus/classification , Aviadenovirus/pathogenicity , DNA Restriction Enzymes/analysis , Genome, Viral , Restriction Mapping , Species Specificity , Virulence/geneticsABSTRACT
Antisera were raised in chickens to six group E fowl adenoviruses (FAV) which have been divided into a highly virulent (hypervirulent) and a mildly virulent subgroup using restriction endonuclease analysis. Virus neutralisations showed that these two distinct restriction endonuclease groups were distinguishable serologically, and indicated a possible vaccine candidate for use against the hypervirulent FAV. The suitability of this candidate was established in challenge experiments where vaccination with this virus protected against challenge from another hypervirulent virus as well as one of the mildly virulent FAV.
