Microbiology & Immunology - Theses

Permanent URI for this collection

http://hdl.handle.net/11343/227

Filters

2021 1
1
Reset filters

Settings
Statistics
Citations
Subject: vaccine × Author: Carrera Montoya, Julio Cesar ×

Search Results

Now showing 1 - 1 of 1
  • Item
    Thumbnail Image
    Interventions for the control of Zika virus transmission: Wolbachia and a single-dose Zika vaccine
    Carrera Montoya, Julio Cesar ( 2021)
    ABSTRACT The versatility of flaviviruses such as Zika virus (ZIKV), dengue virus (DENV) and West Nile virus (WNV) that are capable of replicating in both invertebrate and vertebrate hosts, opens opportunities in the design of interventions aimed at their control. Control at the human level can arise from the generation of vaccines and antivirals, while control at the vector level can be achieved through the regulation and manipulation of mosquito populations. The uncontrollable spread of ZIKV in the Americas during 2015 to 2017 lead the WHO to declare it as a global public health emergency for most of 2016. Now, with a very reduced, but sustained number of cases every year in the Americas, ZIKV is still a treat that can re-emerge in other parts of the world. Currently, there is no licensed vaccines or antivirals against ZIKV that can prepare us for future outbreaks, for which it is crucial to generate and validate them now. Furthermore, since the Zika pandemic, a deeper understanding of viral infections in the context of pregnancy became an obligatory area in the study of all emerging viruses. On the other hand, the success of Wolbachia and specifically the wMel strain as a biological agent to control the spread of dengue virus from mosquito populations to humans, has expanded the options for vector control. Nonetheless, as an endosymbiont highly resistant to genetic manipulation, the identification and characterization of alternative Wolbachia strains is vital due to the unlikely, but always potential, emergence of arboviruses resistant to wMel. In a translational approach and to address some these important questions in the study of control measures against ZIKV, in this doctoral thesis we: a) generated a ZIKV virus-like particle (VLP) based vaccine candidate and assessed the immunogenicity of these particles in mice. To generate our vaccine candidate, we utilised the Adenovirus-vector system, and standardized a protocol for the generation and purification of highly immunogenic and antigenic VLPs. The ZIKV-VLPs were highly morphologically similar to ZIKV by electron microscopy and were antigenic against known anti-Flavivirus neutralizing antibodies. We observed that ZIKV-VLPs alone and inactivated ZIKV in a single dose generated an immune response that lasted over 6 months, but it did not neutralize the infection of cells virus in vitro. Thus, the ZIKV-VLPs needed to be in combination with an adjuvant to generate a neutralizing immune response. From the three adjuvants that we used, Aluminum oxyhydroxide (Alhydrogel) was found as the most effective in a single dose regime, since it not only neutralized the virus, but also it generated a greater number of specific B-memory cells. We additionally observed that the generation of the neutralizing antibodies persisted for up to 6 months, induced a strong B-cell population and importantly generated subpopulations of immunoglobulins that are less related to antibody-dependent enhancement and disease severity. Our results indicate that the produced ZIKV VLPs are robust for use as a single-dose approach as a vaccine candidate; b) identified potential next generation Wolbachia strains by screening a panel of Drosophila simulans flies trans-infected with 12 different Wolbachia strains. We found that 75% of these strains (8 out of 12) significantly reduced ZIKV RNA levels and exhibited a significant negative correlation between Wolbachia levels and virus replication. This D. simulans model system can support further research in the selection of new Wolbachia strains as a pre-screening method prior to the artificial transfer into Aedes mosquitoes aimed at preventing the transmission of arboviruses; and in a more basic fashion c) evaluated the replication kinetics of ZIKV and the related encephalitic flavivirus West Nile strain Kunjin virus (WNVKUN) in early-term placental cell lines. We have observed that WNVKUN in fact replicates with a greater rate and to higher titres that ZIKV in these cell lines. These results would indicate the potential for all flaviviruses to replicate in placental tissue, but it is the ability to cross the placenta itself that is the restrictive factor in the clinical progression and presentation of congenital Zika syndrome. This additionally, provided some insights into the particular ability of ZIKV in causing microcephaly when maternal infection happens during the first trimester of pregnancy. Overall, the findings presented in this doctoral thesis have provided important insights into infection of ZIKV in the placenta and into the development of preventative strategies to protect the human population from future ZIKV outbreaks.