ONE HEALTH APPROACH FOR STUDYING EMERGING AND RE-EMERGING VIRUSES IN LIBERIA
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2024
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The production and use of recombinant antigens for integrated serosurveillance for Lassa Virus (LASV) and other emerging and re-emerging epidemic-prone viruses are critical to global health efforts to effectively prevent future disease outbreaks. LASV causes millions of infections and over 10,000 deaths annually and remains endemic in West African countries, including Nigeria, Liberia, Sierra Leone, Guinea, etc. Additionally, the 2014- 2015 Ebola Virus Disease (EVD) outbreak in West Africa resulted in over 28,000 infected individuals and over 11,000 deaths, and the 2022 EVD outbreak in the Democratic Republic of Congo (DRC) led to more than 2,200 lives being lost. With the circulation of these emerging and re-emerging viruses in Africa, there are still challenges in conducting surveillance. The current surveillance system uses traditional enzyme-linked immunosorbent assay (ELISA), which is time-consuming, requires more reagents, and requires copious amounts of viral antigens. Most of these viruses that have epidemic or pandemic potential are category A pathogens. These viruses need to be handled in a Biosafety Level 4 (BSL-4) containment facility, which is lacking in most African countries. The issue of using a live virus is of major concern. Developing a serological assay using recombinant antigens for integrated surveillance is key to solving these challenges. The production of recombinant proteins eliminates the need for BSL-4 containment facilities, which are essential for handling highly infectious pathogens in traditional production platforms. The Multiplex Immuno-assay (MIA) can detect multiple analytes in the same well and is very cost-effective as compared to ELISA. This dissertation centers on the development of recombinant Dengue virus-2 (DENV-2) and West Nile Virus (WNV) NS1 antigens. The rationale for developing DENV-2 and WNV) NS1 antigens is multifaceted, such as developing improved diagnostics and supporting vaccine development and research.
We also evaluated the performance of LASV GP and NP, as well as other recombinant antigens from viruses to screen for viral exposure across various species, including humans, rodents, and dogs. We adopted the multiplex immune assay (MIA) platform to conduct population-based seroprevalence studies for several coronaviruses in Liberia using an MIA.
We used the Drosophila S2 expression platform and an immobilized metal affinity chromatography (IMAC) purification system to produce DENV and WNV NS1 proteins. Using MIA, we evaluated the performance of LASV and other viral antigens across humans, rodents, and dogs. We collected 200 serum samples from healthy human individuals living in LASV-endemic areas of Liberia. We received an additional 200 rodent and 200 dog serum samples from veterinarians from the Ministry of Agriculture (MoA) in Liberia, covering the same four regions/counties: Bong, Grand Bassa, Lofa, and Nimba. For our nationwide seroprevalence studies, we collected 3500 serum samples, a representative national sample from Bong, Grand Cape Mount, Sinoe, Maryland, and Montserrado counties.
Our results showed the successful production of DENV and WNV NS1 proteins, which were validated using immune sera as positive controls and naïve sera as negative controls. These proteins demonstrated stability and strong immunogenicity, paving the way for their successful use in developing multiplex serological assays using these antigens.
Results from our seroprevalence studies of LASV and other antigens showed a high prevalence of LASV antibodies in humans, followed by rodents and low seroprevalence in dogs. The low seroprevalence rate observed in dogs suggests that they might not be ideal sentinels for LASV infection. Among the rodent species trapped, the most abundant rodent species was R. rattus, followed by Hylomyscus pamfi, Mastomys species, Graphiurus murinus (African pygmy dormice), and Apodemus sylvaticus. While not considered a reservoir for LASV, R. rattus had the highest seroprevalence for LASV antigens at 27%.
Finally, our Coronavirus population-based survey results showed high reactivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variant antigens, followed by less reactivity to SARS-1 spike antigen and low reactivity to the other coronavirus antigens, including Human coronavirus NL63 (HCoV-NL63) spike and Middle East respiratory syndrome coronavirus (MERS-CoV) spike and NP antigens. Overall, we found that our MIA based on coronavirus antigens is an effective means to measure the seroprevalence of different coronaviruses.
This study shows the utility of recombinant antigens and MIA in conducting seroprevalence studies in humans and animals in resource-limited countries like Liberia. Findings from this study may, in the future, help public health professionals, including veterinarians, prevent future outbreaks.
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Virology, Epidemiology
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161 pages
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