Genomic differences of Vaccinia virus clones from Dryvax smallpox vaccine: the Dryvax-like ACAM2000 and the mouse neurovirulent Clone-3.

Conventional vaccines used for smallpox eradication were often denoted one or another strain of Vaccinia virus (VACV), even though seed virus was sub-cultured multifariously, which rendered the virion population genetically heterogeneous. ACAM2000 cell culture vaccine, recently licensed in the U.S., consists of a biologically vaccine-like VACV homogeneous-sequence clone from the conventional smallpox vaccine Dryvax, which we verified from Dryvax sequence chromatograms is genetically heterogeneous. ACAM2000 VACV and CL3, a mouse-neurovirulent clone from Dryvax, differ by 572 single nucleotide polymorphisms and 53 insertions-deletions of varied size, including a 4.5-kbp deletion in ACAM2000 and a 6.2-kbp deletion in CL3. The sequence diversity between the two clones precludes precisely defining why CL3 is more pathogenic; however, four genes appear significantly dissimilar to account for virulence differences. CL3 encodes intact immunomodulators interferon-alpha/beta and tumor necrosis factor receptors, which are truncated in ACAM2000. CL3 specifies a Cowpox and Variola virus-like ankyrin-repeat protein that might be associated with proteolysis via ubiquitination. And, CL3 shows an elongated thymidylate kinase, similar to the enzyme of the mouse-neurovirulent VACV-WR, a derivative of the New York City Board of Health vaccine, the origin vaccine of Dryvax. Although ACAM2000 encodes most proteins associated with immunization protection, the cloning probably delimited the variant epitopes and other motifs produced by Dryvax due to its VACV genetic heterogeneity. The sequence information for ACAM2000 and CL3 could be significant for resolving the dynamics of their different proteomes and thereby aid development of safer, more effective vaccines.

Comparative genetic analysis of genomic DNA sequences of two human isolates of Tanapox virus.

Members of the genus Yatapoxvirus, which include Tanapox virus (TPV) and Yaba monkey tumor virus, infect primates including humans. Two strains of TPV isolated 50 years apart from patients infected from the equatorial region of Africa have been sequenced. The original isolate from a human case in the Tana River Valley, Kenya, in 1957 (TPV-Kenya) and an isolate from an infected traveler in the Republic of Congo in 2004 (TPV-RoC). Although isolated 50 years apart the genomes were highly conserved. The genomes differed at only 35 of 144,565 nucleotide positions (99.98% identical). We predict that TPV-RoC encodes 155 ORFs, however a single transversion (at nucleotide 10241) in TPV-Kenya resulted in the coding capacity for two predicted ORFs (11.1L and 11.2L) in comparison to a single ORF (11L) in TPV-RoC. The genomes of TPV are A+T rich (73%) and 96% of the sequence encodes predicted ORFs. Comparative genomic analysis identified several features shared with other chordopoxviruses. A conserved sequence within the terminal inverted repeat region that is also present in the other members of the Yatapoxviruses as well as members of the Capripoxviruses, Swinepox virus and an unclassified Deerpox virus suggests the existence of a conserved near-terminal sequence secondary structure. Two previously unidentified gene families were annotated that are represented by ORF TPV28L, which matched homologues in certain other chordopoxviruses, and TPV42.5L, which is highly conserved among currently reported chordopoxvirus sequences.

Genome sequence diversity and clues to the evolution of variola (smallpox) virus.

Comparative genomics of 45 epidemiologically varied variola virus isolates from the past 30 years of the smallpox era indicate low sequence diversity, suggesting that there is probably little difference in the isolates' functional gene content. Phylogenetic clustering inferred three clades coincident with their geographical origin and case-fatality rate; the latter implicated putative proteins that mediate viral virulence differences. Analysis of the viral linear DNA genome suggests that its evolution involved direct descent and DNA end-region recombination events. Knowing the sequences will help understand the viral proteome and improve diagnostic test precision, therapeutics, and systems for their assessment.

A tale of two clades: monkeypox viruses.

Human monkeypox was first recognized outside Africa in 2003 during an outbreak in the USA that was traced to imported monkeypox virus (MPXV)-infected West African rodents. Unlike the smallpox-like disease described in the Democratic Republic of the Congo (DRC; a Congo Basin country), disease in the USA appeared milder. Here, analyses compared clinical, laboratory and epidemiological features of confirmed human monkeypox case-patients, using data from outbreaks in the USA and the Congo Basin, and the results suggested that human disease pathogenicity was associated with the viral strain. Genomic sequencing of USA, Western and Central African MPXV isolates confirmed the existence of two MPXV clades. A comparison of open reading frames between MPXV clades permitted prediction of viral proteins that could cause the observed differences in human pathogenicity between these two clades. Understanding the molecular pathogenesis and clinical and epidemiological properties of MPXV can improve monkeypox prevention and control.