Flavivirus serology by Western blot analysis

Area of Science:

• Virology
• Immunology
• Epidemiology

Background:

• The spread of West Nile virus (WNV) complicates flavivirus surveillance and diagnosis in the US.
• Distinguishing WNV from other endemic flaviviruses like St. Louis encephalitis virus (SLEV) is crucial for accurate diagnosis.

Purpose of the Study:

• To compare the efficacy of different serologic assays for flavivirus detection.
• To evaluate the utility of a Western blot (WB) assay in differentiating WNV and SLEV infections.

Main Methods:

• Comparison of plaque reduction neutralization test (PRNT), enzyme immunoassay (EIA), and Western blot (WB) assays.
• Testing human and chicken sera against WNV and SLEV.
• Analyzing antibody binding to viral proteins (NS1, E, prM) in WB.
• Correlating WB results with nucleic acid amplification tests (TMA, RT-PCR) in human plasma samples.

Main Results:

• Western blot (WB) interpretation relied on antibody binding to non-structural protein 1 (NS1), envelope (E), and pre-membrane (prM).
• Reactivity with NS1 protein showed the most promise for differentiating WNV and SLEV infections.
• Envelope protein (E) exhibited high cross-reactivity, suggesting its use as a flavivirus group antigen.
• WB results correlated with TMA and RT-PCR in WNV seroconverting donors.

Conclusions:

• The Western blot assay, particularly using NS1, offers a valuable tool for differentiating West Nile virus and St. Louis encephalitis virus infections.
• Further development of serologic assays is needed to improve flavivirus surveillance and diagnosis in regions with co-endemic viruses.