Browsing by Author "Heath, Livio"

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    Open Access
    The Development of Dual Vaccines against Lumpy Skin Disease (LSD) and Bovine Ephemeral Fever (BEF)
    (2021-10-20) Douglass, Nicola; Omar, Ruzaiq; Munyanduki, Henry; Suzuki, Akiko; de Moor, Warren; Mutowembwa, Paidamwoyo; Pretorius, Alri; Nefefe, Tshifhiwa; Schalkwyk, Antoinette van; Kara, Pravesh; Heath, Livio; Williamson, Anna-Lise
    Dual vaccines (n = 6) against both lumpy skin disease (LSD) and bovine ephemeral fever (BEF) were constructed, based on the BEFV glycoprotein (G) gene, with or without the BEFV matrix (M) protein gene, inserted into one of two different LSDV backbones, nLSDV∆SOD-UCT or nLSDVSODis-UCT. The inserted gene cassettes were confirmed by PCR; and BEFV protein was shown to be expressed by immunofluorescence. The candidate dual vaccines were initially tested in a rabbit model; neutralization assays using the South African BEFV vaccine (B-Phemeral) strain showed an African consensus G protein gene (Gb) to give superior neutralization compared to the Australian (Ga) gene. The two LSDV backbones expressing both Gb and M BEFV genes were tested in cattle and shown to elicit neutralizing responses to LSDV as well as BEFV after two inoculations 4 weeks apart. The vaccines were safe in cattle and all vaccinated animals were protected against virulent LSDV challenge, unlike a group of control naïve animals, which developed clinical LSD. Both neutralizing and T cell responses to LSDV were stimulated upon challenge. After two inoculations, all vaccinated animals produced BEFV neutralizing antibodies ≥ 1/20, which is considered protective for BEF.
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    Evidence of ancient papillomavirus recombination
    (Microbiology Society, 2006) Varsani, Arvind; van der Walt, Eric; Heath, Livio; Rybicki, Edward P; Williamson, Anna Lise; Martin, Darren P
    An open question amongst papillomavirus taxonomists is whether recombination has featured in the evolutionary history of these viruses. Since the onset of the global AIDS epidemic, the question is somewhat less academic, because immune-compromised human immunodeficiency virus patients are often co-infected with extraordinarily diverse mixtures of human papillomavirus (HPV) types. It is expected that these conditions may facilitate the emergence of HPV recombinants, some of which might have novel pathogenic properties. Here, a range of rigorous analyses is applied to full-genome sequences of papillomaviruses to provide convincing statistical and phylogenetic evidence that evolutionarily relevant papillomavirus recombination can occur.
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    Genetic characterisation of six novel African swine fever viruses isolated from a pig, warthog, wild boar, and ticks
    (2021) Ndlovu, Sandy Sibusiso; Williamson, Anna-Lise; Carulei, Olivia; Heath, Livio
    African swine fever (ASF) is a disease that affects domestic pigs and wild boars, resulting in up to 100% case fatality rate, and there is currently no effective treatment or vaccine. To date, there are 67 ASFV complete genome sequences available, but most of the sequences represent only genotypes I-V and VII-X of the 24 genotypes identified based on p72 sequencing, limiting inter and intra-genotype comparative studies. ASFVs encode several multigene families (MGFs) involved in virulence and host range which are found at the genomic termini and the majority of genomic differences between isolates are due to the composition of these MGFs. The comparison of the MGFs across ASFV isolates is of utmost importance in understanding genome variability and their contribution to virulence. The p72 gene has historically been used in phylogenetic analysis of ASFV. However, it lacks the capacity for higher resolution between isolates belonging to the same genotype. This study aimed to analyse and characterise six novel ASFV isolates of African origin from a domestic pig, warthog, wild boar and ticks in terms of genomic makeup, MGF composition and phylogenetic relationships, including identification of additional phylogenetic markers, specifically for use in discrimination between closely related isolates. Genomes of six novel isolates were sequenced and annotated by identifying open reading frames (ORFs) with a methionine START codon and performing BLASTx searches of each ORF against the NCBI data base. Differences between the genomes were analysed by generating dotplots and using Base-By-Base which showed them to be mostly collinear, but regions of difference were observed at the termini and the CCR. MGF analysis using sorting and clustering in Morpheus software, based on genotype, serogroup, country, host, virulence, and year, showed that genotype and serogroup play a role in the MGF arrangement patterns. Loci corresponding to regions of difference in the CCR were used for phylogenetic comparison to the previously identified marker p72. The tree topology of all of the alternative phylogenies differed from the current p72 classification. B117L and B169L provided slightly better resolution of genotypes I and II, respectively, and viruses from East Africa that are classified as belonging to genotype IX based on p72 were separated when using EP364R. This data adds to the pool of diverse ASFV isolates available for comparative genomics studies, and to the knowledge of ASFV in Africa. The sequencing of more diverse ASFV isolates of each genotype will help characterise the MGFs arrangement patterns among isolates. The novel alternative phylogenetic markers should further be investigated using more ASFV isolates representing the 24 genotypes described to date.
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    Influence of the Viral Superoxide Dismutase (SOD) Homologue on Lumpy Skin Disease Virus (LSDV) Growth, Histopathology and Pathogenicity
    (2020-11-07) Douglass, Nicola; Munyanduki, Henry; Omar, Ruzaiq; Gers, Sophette; Mutowembwa, Paidamwoyo; Heath, Livio; Williamson, Anna-Lise
    Lumpy skin disease is an important economic disease of cattle that is controlled by vaccination. This paper presents an investigation into the role of the lumpy skin disease virus (LSDV) superoxide dismutase (SOD) homologue on growth and histopathology of the virus both in vitro and in vivo. SOD homologue knock-out and knock-in recombinants (nLSDV∆SOD-UCT and nLSDVSODis-UCT, respectively) were constructed and compared to the Neethling vaccine (nLSDV) for growth in a permissive bovine cell line as well as on fertilized chick chorioallantoic membranes (CAMs). The infected CAMs were scored for histological changes. Deletion of the SOD homologue from LSDV reduced virus growth both in Madin-Darby bovine kidney (MDBK) cells as well as on CAMs. Furthermore, the knockout virus showed reduced inflammation in CAMs and more ballooning degeneration. A pilot experiment was performed in cattle to compare the lesions produced by the different LSDV constructs in the same animal. One animal developed a larger lesion to nLSDV∆SOD-UCT compared to both nLSDVSODis-UCT and nLSDV. Histological analysis of biopsies of these lesions shows less inflammation and necrosis associated with nLSDVSODis-UCT compared to nLSDV and nLSDV∆SOD-UCT. None of the vaccinated animals showed disseminated LSDV disease, indicating that the candidate vaccines are safe for further testing. Our results suggest that the SOD homologue may improve immunogenicity and reduce virulence.
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    Recombination patterns in aphthoviruses mirror those found in other picornaviruses
    (American Society for Microbiology, 2006) Heath, Livio; van der Walt, Eric; Varsani, Arvind; Martin, Darren P
    Foot-and-mouth disease virus (FMDV) is thought to evolve largely through genetic drift driven by the inherently error-prone nature of its RNA polymerase. There is, however, increasing evidence that recombination is an important mechanism in the evolution of these and other related picornoviruses. Here, we use an extensive set of recombination detection methods to identify 86 unique potential recombination events among 125 publicly available FMDV complete genome sequences. The large number of events detected between members of different serotypes suggests that horizontal flow of sequences among the serotypes is relatively common and does not incur severe fitness costs. Interestingly, the distribution of recombination breakpoints was found to be largely nonrandom. Whereas there are clear breakpoint cold spots within the structural genes, two statistically significant hot spots precisely separate these from the nonstructural genes. Very similar breakpoint distributions were found for other picornovirus species in the genera Enterovirus and Teschovirus. Our results suggest that genome regions encoding the structural proteins of both FMDV and other picornaviruses are functionally interchangeable modules, supporting recent proposals that the structural and nonstructural coding regions of the picornaviruses are evolving largely independently of one another.