At a global level, ongoing ecological, environmental and demographic changes favor the survival and expansion of several mosquito and tick species that transmit arboviruses. Aedes mosquito species that thrive in urban environments created by humans are responsible for epidemics of several flaviviruses [dengue virus (DENV) serotypes 1, 2, 3, 4; Zika virus (ZIKV); yellow fever virus (YFV)] and alphaviruses [chikungunya virus (CHIKV) and Mayaro virus (MAYV)]. Laboratory-based diagnosis and surveillance for arboviruses is difficult because most infected individuals are asymptomatic or develop a mild undifferentiated febrile illness. Serological assays have been developed for the detection of recent or past arboviral infections, but the utility of these assays is severely limited by antibody cross reactivity between related viruses. For example, when ZIKV emerged in many regions of the Americas where greater than 80% of the population was dengue-immune, with current serological assays, it was difficult, if not impossible, to identify infected individuals or monitor the spread of ZIKV at a population level, and likewise to now detect new DENV infections in areas that experienced intense ZIKV epidemics. Our studies over the past 10 years demonstrate that people exposed to flavivirus infections reliably develop antibodies to epitopes that are unique to each flavivirus as well as cross-reactive antibodies. Using our discoveries about the location of immunodominant virus type-specific epitopes, we have produced novel recombinant antigens and demonstrated their utility for the type-specific diagnosis of arboviruses.
Under Specific Aim 1 of this proposal, we will build on these discoveries to develop a sample-sparing, microsphere bead-based multiplex assay for the type-specific and sensitive detection of recent or past arbovirus infections. Our initial studies will focus on 8 arboviruses transmitted by Aedes aegypti and Aedes albopictus mosquitos because these viruses share a similar ecology and co-circulate in the same human populations. At a second stage, we will expand the coverage of the assay to detect infections with other arboviruses transmitted by other mosquito species and ticks. Several tetravalent DENV and ZIKV vaccines are currently being evaluated in human clinical trials. While vaccine developers have relied on neutralizing antibodies as a correlate of protection, recent results from clinical trials demonstrate that neutralizing antibodies alone are a poor correlate of vaccine safety and efficacy. We have identified flavivirus type- and epitope-specific antibody responses that are better predictors than neutralizing antibodies of vaccine safety and efficacy.
Under Specific aim 2 of this proposal, we will develop a sample-sparing microsphere-based assay for the detection of epitope-specific vaccine-induced antibody responses that are correlated with protective immunity to each of the DENV serotypes and ZIKV. The technological advances and products from this proposal will enhance our ability to efficiently monitor arbovirus infections at the individual and population levels and also support the development of arbovirus vaccines.
Program Narrative Many people living in tropical regions of the world are infected by multiple viruses transmitted by mosquitos and other blood feeding arthropods. With currently available laboratory methods, it is difficult to detect specific antibodies induced by arbovirus infections or candidate vaccines. We will develop a new assay that will be able to accurately detect specific antibodies to different arboviruses and arbovirus vaccines in a single drop of blood.