Louisa E. Wallace


Postgraduate Research Student
M.Phil., M.Res., B.Sc.(Hons)

Academic and research departments

School of Biosciences and Medicine.

University roles and responsibilities

  • PGR Representative (Department of Microbial Sciences)
  • PGR Transitions Mentor

My qualifications

2013
B.Sc.(Hons) Biochemistry
University of St Andrews
2014
M.Res. Infection and Immunobiology (Virology) with Distinction
University of Glasgow
2019
M.Phil. Molecular Virology and Immunology
University of Surrey

My publications

Publications

Dengue virus (DENV) is the most significant arthropod-borne virus (arbovirus) of humans, primarily transmitted by Aedes aegypti mosquitoes. Currently there are no specific therapeutics and the existing vaccine exhibits limited efficacy. Therefore, vector control remains the best approach to manage disease spread.

We previously demonstrated that DENV-2 infection does not induce innate immunodeficiency (IMD) signalling in the Ae. aegypti Aag2 cell line, recapitulating in vivo data from other groups. Furthermore, prior infection with DENV-2 reduces IMD signalling activation by classical immune stimuli. This project aimed to identify DENV-2 antagonist(s) responsible for this immune inhibition using an RT-qPCR-based screening platform in which IMD signalling is stimulated in cells expressing DENV-2 proteins individually. Our results identified NS4A as a tentative antagonist, which can now be used to enhance our understanding of Ae. aegypti antiviral immunity by investigating virus-host interactions.

The study of vector immunity is hampered by the lack of tools such as antibodies and cell lines. Our group previously created CRISPR-Cas9 knockout Aag2 cell lines, which lack genes essential in the innate immune pathways. These knockout cell lines were created from clonally selected Aag2 cells derived from the heterogeneous parental cell line, and this report also describes the final characterisation of these clones. Results confirm that the cells are embryonic in origin, which confounded our sex analysis. Aag2 clones were confirmed to be persistently infected insect-specific viruses, cell fusing agent virus and Phasi Charoen-like virus. Transfection efficiencies were also determined for the clones of interest. Finally, mutations introduced by CRISPR-Cas9 were characterised in cells derived from one of the clonally selected lines, with one clone identified as the intended mutant, however the IMD pathway-deficient cell clones were determined as wild type.

Ultimately insights into vector antiviral immunity may contribute towards development of transmission-incompetent mosquitoes, thereby reducing the global burden of dengue.

Ribeiro José M. C., Fredericks Anthony C., Russell Tiffany A., Wallace Louisa E., Davidson Andrew D., Fernandez-Sesma Ana, Maringer Kevin (2019) Aedes aegypti (Aag2)-derived clonal mosquito cell lines reveal the effects of pre-existing persistent infection with the insect-specific bunyavirus Phasi Charoen-like virus on arbovirus replication, PLOS Neglected Tropical Diseases 13 (11) e0007346 pp. 1-25 Public Library of Science

Background

Aedes aegypti is a vector mosquito of major public health importance, transmitting arthropod-borne viruses (arboviruses) such as chikungunya, dengue, yellow fever and Zika viruses. Wild mosquito populations are persistently infected at high prevalence with insect-specific viruses that do not replicate in vertebrate hosts. In experimental settings, acute infections with insect-specific viruses have been shown to modulate arbovirus infection and transmission in Ae. aegypti and other vector mosquitoes. However, the impact of persistent insect-specific virus infections, which arboviruses encounter more commonly in nature, has not been investigated extensively. Cell lines are useful models for studying virus-host interactions, however the available Ae. aegypti cell lines are poorly defined and heterogenous cultures.

Methodology/Principle findings

We generated single cell-derived clonal cell lines from the commonly used Ae. aegypti cell line Aag2. Two of the fourteen Aag2-derived clonal cell lines generated harboured markedly and consistently reduced levels of the insect-specific bunyavirus Phasi Charoen-like virus (PCLV) known to persistently infect Aag2 cells. In contrast to studies with acute insect-specific virus infections in cell culture and in vivo, we found that pre-existing persistent PCLV infection had no major impact on the replication of the flaviviruses dengue virus and Zika virus, the alphavirus Sindbis virus, or the rhabdovirus vesicular stomatitis virus. We also performed a detailed characterisation of the morphology, transfection efficiency and immune status of our Aag2-derived clonal cell lines, and have made a clone that we term Aag2-AF5 available to the research community as a well-defined cell culture model for arbovirus-vector interaction studies.

Conclusions/Significance

Our findings highlight the need for further in vivo studies that more closely recapitulate natural arbovirus transmission settings in which arboviruses encounter mosquitoes harbouring persistent rather than acute insect-specific virus infections. Furthermore, we provide the well-characterised Aag2-derived clonal cell line as a valuable resource to the arbovirus research community.

Additional publications