Antoinette van Schalkwyk

Dr. Antoinette van Schalkwyk

Agricultural Research Council - Onderstepoort Veterinary Institute
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Research Focus & Metrics

Academic Career Length

16Years (2011-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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12 December 2018 in PLOS ONE
Verified
Journal Article
Open access
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ASAlexander Sprygin
Alexander Sprygin
YBYurii Babin
Yurii Babin
YPYana Pestova
Yana Pestova
SKSvetlana Kononova
Svetlana Kononova
DWDavid B Wallace
David B Wallace
AKAlexander Kononov
Alexander Kononov
Wide spread incidences of vaccine-like strains of lumpy skin disease virus (LSDV) have recently been reported in a Russian region with a neighboring country that actively vaccinate with a live attenuated LSD vaccine. The use of live-attenuated viruses (LAVs) as vaccines during an active outbreak, creates potential ground for coinfection of hosts and emergence of a strain combining genetic fragments of both parental vaccine and field strains. In this study, we analyse the vaccine-like strain LSDV RUSSIA/Saratov/2017 detected in Saratovskaya oblast, a region sharing border with Kazakhstan. To gain insight into possible recombination signals, a full-genome next-generation sequencing of the viral genome was performed using the Illumina platform. The genome contains the backbone of a live-attenuated vaccine with a patchwork of wild-type field virus DNA fragments located throughout. A total of 27 recombination events were identified. The average distance between the recombination sites was 3400 base pairs (bp). The impact of the recombination events on the virulence and transmission capacity of the identified virus remains to be clarified. These findings provide evidence for the first time of genetic exchanges between closely related strains of capripoxviruses in the field and a vaccine strain, and prompt a revisiting of the vaccination issue for a safe and efficacious prevention and control strategy of LSD.

9 August 2020 in Archives of Virology
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Journal Article
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ASAlexander Sprygin
Alexander Sprygin
ASAntoinette van Schalkwyk
Antoinette van Schalkwyk
ISIrina Shumilova
Irina Shumilova
ANAlexander Nesterov
Alexander Nesterov
SKSvetlana Kononova
Svetlana Kononova
AKAleksandr Kononov
Aleksandr Kononov

23 September 2021 in Transboundary and Emerging Diseases
Verified
Journal Article
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ASAntoinette van Schalkwyk
Antoinette van Schalkwyk
OBOlga Byadovskaya
Olga Byadovskaya
ISIrina Shumilova
Irina Shumilova
DWDavid B. Wallace
David B. Wallace
ASAlexander Sprygin
Alexander Sprygin

1 April 2012 in Molecular Plant-Microbe Interactions®
Verified
Journal Article
Open access
CWCharles K. Wairuri
Charles K. Wairuri
JWJacquie Van der Waals
Jacquie Van der Waals
ASAntoinette van Schalkwyk
Antoinette van Schalkwyk
JTJacques Theron
Jacques Theron
Type IV pili are virulence factors in various bacteria. Several subclasses of type IV pili have been described according to the characteristics of the structural prepilin subunit. Although type IVa pili have been implicated in the virulence of Ralstonia solanacearum, type IVb pili have not previously been described in this plant pathogen. Here, we report the characterization of two distinct tad loci in the R. solanacearum genome. The tad genes encode functions necessary for biogenesis of the Flp subfamily of type IVb pili initially described for the periodontal pathogen Aggregatibacter actinomycetemcomitans. To determine the role of the tad loci in R. solanacearum virulence, we mutated the tadA2 gene located in the megaplasmid that encodes a predicted NTPase previously reported to function as the energizer for Flp pilus biogenesis. Characterization of the tadA2 mutant revealed that it was not growth impaired in vitro or in planta, produced wild-type levels of exopolysaccharide galactosamine, and exhibited swimming and twitching motility comparable with the wild-type strain. However, the tadA2 mutant was impaired in its ability to cause wilting of potato plants. This is the first report where type IVb pili in a phytopathogenic bacterium contribute significantly to plant pathogenesis.

29 January 2013 in BMC Medical Genetics
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Journal Article
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TDTyren M Dodgen
Tyren M Dodgen
WHWarren E Hochfeld
Warren E Hochfeld
HFHeidi Fickl
Heidi Fickl
SASahle M Asfaha
Sahle M Asfaha
CDChrisna Durandt
Chrisna Durandt
Michael Sean PepperMichael Sean Pepper
Michael Sean Pepper
Adverse drug reactions and lack of therapeutic efficacy associated with currently prescribed pharmacotherapeutics may be attributed, in part, to inter-individual variability in drug metabolism. Studies on the pharmacogenetics of Cytochrome P450 (CYP) enzymes offer insight into this variability. The objective of this study was to compare the AmpliChip CYP450 Test® (AmpliChip) to alternative genotyping platforms for phenotype prediction of CYP2C19 and CYP2D6 in a representative cohort of the South African population.

7 June 2020 in Transboundary and Emerging Diseases
Verified
Journal Article
Open access
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ASAntoinette van Schalkwyk
Antoinette van Schalkwyk
PKPravesh Kara
Pravesh Kara
KEKaren Ebersohn
Karen Ebersohn
AMArshad Mather
Arshad Mather
HAHenry Annandale
Henry Annandale
DWDavid Brian Wallace
David Brian Wallace
South Africa is endemic for lumpy skin disease and is therefore reliant on various live attenuated vaccines for the control and prevention of the disease. In recent years, wide‐spread outbreaks of vaccine‐like strains of lumpy skin disease virus (LSDV) were reported internationally, leading to an increase in the generation of full genome sequences from field isolates. In this study, the complete genomes of six LSDVs submitted during active outbreaks in the 1990’s in South Africa were generated. Based on phylogenetic analysis, the six viruses clustered with vaccine strains in LSDV Subgroup 1.1 and are subsequently referred to as vaccine‐associated. The genetic differences between the phenotypically distinct vaccine and vaccine‐associated strains were 67 single nucleotides polymorphisms (SNPs). This study characterised the location and possible importance of each of these SNPs in their role during virulence and host specificity.