Graduation Year

2018

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Global Health

Major Professor

Thomas R. Unnasch, Ph.D.

Committee Member

Andrea Bingham, Ph.D., MSPH

Committee Member

Ricardo Izurieta, MD, MPH, DrPH

Committee Member

Michael Teng, Ph.D.

Keywords

dengue, MIA, microsphere, hemorrhagic fever, diagnostics

Abstract

Infections with dengue viruses (DENV) constitute both a global problem as well as locally in Florida. DENV comprise four distinct serotypes of single-stranded RNA viruses and belong to the family Flaviviridae. DENV are among the most medically important arboviruses in the world and cases may currently exceed 400 million per annum. Additionally, dengue established its first recorded endemic transmission cycle in the state of Florida in over a half century, first within the Florida Keys during 2009-10 followed by an unrelated outbreak in Martin County in 2013. The clinical profile of DENV infections ranges from a mild febrile illness to severe illness including hemorrhaging and/or shock, occasionally leading to death. Asymptomatic and mild cases also play a role in maintaining transmission cycles. The early diagnosis and management of patients at the clinical level have both proven to be major obstacles in the control of DENV and are important at both the individual and community levels. Individually, the proper management of patients that will progress to severe illness demands that they are identified in order to receive supportive treatment and mitigate associated morbidity and mortality. At the community level, early diagnosis may reduce transmission by limiting the possibility of vector contact with viremic individuals. Early diagnosis is dependent on the detection of viral markers, while a number of host factors may inform prognosis. The microsphere-based immunoassay (MIA) is capable of detecting up to 100 different targets in a single sample and therefore would be useful as a single assay for determining both. This study attempted to develop a diagnostic and prognostic MIA using the DENV NS1 glycoprotein and 5 host markers as targets. For the purposes of DENV NS1 detection in MIA, a set of monoclonal antibodies (mAbs) were subjected to immunoprecipitation and/or Western blot analysis in order to determine immunoreactivity. Two mAbs, 3A5.4 and 3D1.4, were chosen for use in MIA as a capture antibody and a detection antibody, respectively, and the results compared to a commercially available DENV NS1 ELISA. The 5 markers chosen for MIA trials included GM-CSF, IFN-γ, IP-10, IL-10, and MCP-1 and were selected from a panel of 27 markers screened initially in two in vitro models of DENV infection in addition to serum samples. The two cell lines investigated were HPMEC ST1.6R and u937 as both are thought to play important roles in models of DENV pathogenesis. The results of the DENV NS1 detection MIA were initially promising but were ultimately unsuccessful. When measuring host markers in the MIA, results pointed towards certain profiles that may be of future use. IL-10 was found to be elevated in a statistically significant manner in DENV qRT-PCR+ samples (p=0.035) when compared to negative sera. MCP-1 elevation was found to be of borderline significance (p=0.058). Other potential markers based on the results reported here include IP-10, IL-6, IL-8, VEGF, and RANTES. The ultimate goal of measuring host markers is to gain the ability to differentiate patients that will progress to severe illness from those that will recover. In conclusion, despite the failure of the MIA to detect DENV NS1 in human sera, our results in determining host markers and developments leading to successful DENV NS1 detection ELISAs elsewhere lead us to believe that this approach remains promising. Major drawbacks of this study included the lack of samples from patients that experienced severe DENV illness as a comparative group in addition to small sample sizes. Future goals should include determining the reasons for the failure of the MIA in detecting DENV NS1, selecting a panel of appropriate markers to differentiate non-severe from severe cases of DENV prior to progression, and optimizing the inclusion of these markers to an appropriate number.

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