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With the aim of deriving a definitive phylogenetic tree for as many mammalian and avian herpesvirus species as possible, alignments were made of amino acid sequences from eight conserved and ubiquitously present genes of herpesviruses, with 48 virus species each represented by at least one gene. Phylogenetic trees for both single-gene and concatenated alignments were evaluated thoroughly by maximum-likelihood methods, with each of the three herpesvirus subfamilies (the Alpha-, Beta-, and Gammaherpesvirinae) examined independently. Composite trees were constructed starting with the top-scoring tree based on the broadest set of genes and supplemented by addition of virus species from trees based on narrower gene sets, to give finally a 46-species tree; branching order for three regions within the tree remained unresolved. Sublineages of the Alpha-and Betaherpesvirinae showed extensive cospeciation with host lineages by criteria of congruence in branching patterns and consistency in extent of divergence. The Gammaherpesvirinae presented a more complex picture, with both higher and lower substitution rates in different sublineages. The final tree obtained represents the most detailed view to date of phylogenetic relationships in any family of large-genome viruses.The Herpesviridae are a numerous family of large DNA viruses which have as their natural hosts humans, other mammals and vertebrates, and in one described case, an invertebrate (11, 16). The genomes of herpesviruses of mammals and birds clearly evince descent from a common ancestor, but with a great range of variation in terms of nucleotide substitution, gene content, and genomic arrangement (15). The Herpesviridae have been divided into three subfamilies, the Alpha-, Beta-, and Gammaherpesvirinae, initially from their distinct biological properties and latterly more precisely on the basis of their genomic attributes (16). Over the last two decades an extensive body of herpesvirus DNA sequence data has been built up, from single-gene analyses to studies of whole genomes (in the range 120 to 240 kbp). Phylogenetic studies using herpesvirus sequences have been undertaken, demonstrating clear division into the three subfamilies and, in some sublineages, patterns of divergence consistent with cospeciation of virus and host (7,9,13,14). Herpesviruses of fish (2, 3), amphibians (4), and invertebrates (A. J. Davison, personal communication) are only remotely related to the mammalian and avian viruses, while certain turtle viruses (the only reptile herpesviruses for which some sequence is known) probably group with the mammalian and avian viruses (18).We describe in this report a major update of herpesvirus phylogenetic analysis, using the greatly increased number of gene sequences now available from a wide range of mammalian and avian herpesviruses, and enabled by advances both in processing power of modern computers and in methods for analysis of relationships among gene sequences. We aimed to produce by good current practice a single phylogenetic tree that would...

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Nucleocapsid (N) proteins from representative viruses of three genera within the Paramyxoviridae were expressed in insect cells using recombinant baculoviruses. RNA-containing structures, which appear morphologically identical to viral nucleocapsids, were isolated and subsequently imaged under a transmission electron microscope. Analysis of these images revealed marked differences in nucleocapsid morphology among the genera investigated, most notably between viruses of the Paramyxovirinae and the Pneumovirinae subfamilies. Helical pitch measurements were made, revealing that measles virus (MV, a Morbillivirus within the subfamily Paramyxovirinae) N protein produces helices that adopt multiple conformations with varying degrees of flexibility, while that of the Rubulavirus simian virus type 5 (SV5, subfamily Paramyxovirinae) produces more rigid structures with a less heterogeneous pitch distribution. Nucleocapsids produced by respiratory syncytial virus (RSV, subfamily Pneumovirinae) appear significantly narrower than those of MV and SV5 and have a longer pitch than the most extended form of MV. In addition to helical nucleocapsids, ring structures were also produced, image analysis of which has demonstrated that rings assembled from MV N protein consist of 13 subunits. This is consistent with previous reports that Sendai virus nucleocapsids have 13n07 subunits per turn. It was determined, however, that SV5 subnucleocapsid rings have 14 subunits, while rings derived from the radically different RSV nucleocapsid have been found to contain predominantly 10 subunits.