Mosquito-borne Zika virus (ZIKV) typically causes a mild and self-limiting illness known as Zika fever, which often is accompanied by maculopapular rash, headache, and myalgia. During the current outbreak in South America, ZIKV infection during pregnancy has been hypothesized to cause microcephaly and other diseases. The detection of ZIKV in fetal brain tissue supports this hypothesis. Because human infections with ZIKV historically have remained sporadic and, until recently, have been limited to small-scale epidemics, neither the disease caused by ZIKV nor the molecular determinants of virulence and/or pathogenicity have been well characterized. Here, we describe a small animal model for wild-type ZIKV of the Asian lineage. Using mice deficient in interferon α/β and Ɣ receptors (AG129 mice), we report that these animals were highly susceptible to ZIKV infection and disease, succumbing within seven to eight days. Rapid viremic dissemination was observed in visceral organs and brain; but only was associated with severe pathologies in the brain and muscle. Finally, these results were consistent across challenge routes, age of mice, and inoculum doses. These data represent a mouse model for ZIKV that is not dependent on adapting ZIKV to intracerebral passage in mice. Foot pad injection of AG129 mice with ZIKV represents a biologically relevant model for studying ZIKV infection and disease development following wild-type virus inoculation without the requirement for adaptation of the virus or intracerebral delivery of the virus. This newly developed Zika disease model can be exploited to identify determinants of ZIKV virulence and reveal molecular mechanisms that control the virus-host interaction, providing a framework for rational design of acute phase therapeutics and for vaccine efficacy testing. Zika virus (ZIKV) is an arbovirus that belongs to the family Flaviridae. It currently is causing an explosive outbreak of febrile disease in the Americas. In humans, ZIKV infection typically causes a mild and self-limiting illness known as Zika fever, which often is accompanied by maculopapular rash, headache, and myalgia. During the current outbreak, ZIKV infection during pregnancy has been hypothesized to cause microcephaly and other diseases. The detection of ZIKV in fetal brain tissue supports this hypothesis. Our understanding of the molecular mechanisms controlling ZIKV virulence and pathogenesis is limited, with progress greatly impeded by the lack of a small animal model that does not rely on intracerebral inoculation of the virus. Here, we demonstrate that wild-type ZIKV, that is representative of the Asian lineage currently circulating in South America, causes lethal disease in mice deficient in interferon α/β and Ɣ receptors. In these animals, ZIKV causes severe brain pathology, potentially emulating hallmark features of human fetal ZIKV infection. This newly developed Zika disease model can be exploited to identify determinants of ZIKV virulence and reveal molecular mechanisms that control the virus-host interaction, providing a framework for rational design of acute phase therapeutics and for vaccine efficacy testing.

Zika virus (ZIKV) is an emerging flavivirus that can cause birth defects and neurologic complications. Molecular tests are effective for diagnosing acute ZIKV infection, although the majority of infections produce no symptoms at all or present after the narrow window in which molecular diagnostics are dependable. Serology is a reliable method for detecting infections after the viremic period; however, most serological assays have limited specificity due to cross-reactive antibodies elicited by flavivirus infections. Since ZIKV and dengue virus (DENV) widely cocirculate, distinguishing ZIKV infection from DENV infection is particularly important for diagnosing individual cases or for surveillance to coordinate public health responses. Flaviviruses also elicit type-specific antibodies directed to non-cross-reactive epitopes of the infecting virus; such epitopes are attractive targets for the design of antigens for development of serological tests with greater specificity. Guided by comparative epitope modeling of the ZIKV envelope protein, we designed two recombinant antigens displaying unique antigenic regions on domain I (Z-EDI) and domain III (Z-EDIII) of the ZIKV envelope protein. Both the Z-EDI and Z-EDIII antigens consistently detected ZIKV-specific IgG in ZIKV-immune sera but not cross-reactive IgG in DENV-immune sera in late convalescence (>12 weeks postinfection). In contrast, during early convalescence (2 to 12 weeks postinfection), secondary DENV-immune sera and some primary DENV-immune sera cross-reacted with the Z-EDI and Z-EDIII antigens. Analysis of sequential samples from DENV-immune individuals demonstrated that Z-EDIII cross-reactivity peaked in early convalescence and declined steeply over time. The Z-EDIII antigen has much potential as a diagnostic antigen for population-level surveillance and for detecting past infections in patients.

Mosquito-borne Zika virus (ZIKV) typically causes a mild and self-limiting illness known as Zika fever. Since its recent emergence in 2014 in the American continent, ZIKV infection during pregnancy has been closely associated with a wide range of congenital abnormalities. To date, no vaccines or antivirals are publicly available. We developed Zika virus-like particles (VLPs) and evaluated their immunogenicity and protective efficacy in mouse models. ZIKV VLPs (ZIKVLPs) formulated with alum were injected into 6-8-week-old interferon deficient AG129 mice as well as wild type BALB/c mice. Control mice received PBS/alum. Animals were challenged with 200 PFU (>1000 AG129 LD50s) of ZIKV strain H/PF/2013. All vaccinated mice survived with no morbidity or weight loss while control animals either died at 9 days post challenge (AG129) or had increased viremia (BALB/c). Neutralizing antibodies were observed in all ZIKVLP vaccinated mice. The role of neutralizing antibodies in protecting mice was demonstrated by passive transfer. Our findings demonstrate the protective efficacy of the ZIKVLP vaccine and highlight the important role that neutralizing antibodies play in protection against ZIKV infection. Mosquito-borne Zika virus (ZIKV) typically causes a mild and self-limiting illness known as Zika fever. During the recent outbreak in South America, ZIKV infection during pregnancy was associated with severe congenital abnormalities. We developed a vaccine against ZIKV utilizing virus-like particles (VLPs). VLPs are structurally similar to viruses, but are not infectious. We injected mutant mice capable of succumbing to ZIKV infection with these VLPs. Mice vaccinated with VLPs survived infection, while negative control mice died. These studies are important because ZIKVLP based vaccines could be tested in humans as a prophylactic candidate with minimal safety concerns able to protect unborn babies whose mothers become infected with Zika virus during pregnancy.

Chikungunya fever, an acute and often chronic arthralgic disease caused by the mosquito-borne alphavirus, chikungunya virus (CHIKV), spread into the Americas in late 2013. Since then it has caused epidemics in nearly all New World countries, the second largest being Colombia with over 450,000 suspected cases beginning in September, 2014, and focused in Bolivar Department in the north. We examined 32 human sera from suspected cases, including diverse age groups and both genders, and sequenced the CHIKV envelope glycoprotein genes, known determinants of vector host range. As expected for Asian lineage CHIKV strains, these isolates lacked known Aedes albopictus–adaptive mutations. All the Colombian strains were closely related to those from the Virgin Islands, Saint Lucia, Mexico, Puerto Rico, and Brazil, consistent with a single, point-source introduction from the southeast Asia/Pacific region. Two substitutions in the E2 and E1 envelope glycoprotein genes were found in the Colombian strains, especially E1-K211E involving a residue shown previously to affect epistatically the penetrance of the E1-A226V A. albopictus–adaptive substitution. We also identified two amino acid substitutions unique to all American CHIKV sequences: E2-V368A and 6K-L20M. Only one codon, 6K-47, had a high nonsynonymous substitution rate suggesting positive selection.

Background: Dengue fever is a major public health problem in Colombia. A fever surveillance study was conducted for evaluation of the clinical, epidemiological, and molecular patterns of dengue, prior to Chikungunya and Zika epidemics. Methods: In November 2011–February 2014, a passive facility-based surveillance was implemented in Santa Cruz Hospital, Medellin, and enrolled eligible febrile patients between 1 and 65 years-of-age. Acute and convalescent blood samples were collected 10–21 days apart and tested for dengue using IgM/IgG ELISA. RNA was extracted for serotyping using RT-PCR on acute samples and genotyping was performed by sequencing. Results: Among 537 febrile patients enrolled during the study period, 29% (n = 155) were identified to be dengue-positive. Only 7% of dengue cases were hospitalized, but dengue-positive patients were 2.6 times more likely to be hospitalized, compared to non-dengue cases, based on a logistic regression. From those tested with RT-PCR (n = 173), 17 were dengue-confirmed based on PCR and/or virus isolation showing mostly DENV-3 (n = 9) and DENV-4 (n = 7) with 1 DENV-1. Genotyping results showed that: DENV-1 isolate belongs to the genotype V or American/African genotype; DENV-3 isolates belong to genotype III; and DENV-4 isolates belong to the II genotype and specifically to the IIb sub-genotype or linage. Conclusions: Our surveillance documented considerable dengue burden in Santa Cruz comuna during non-epidemic years, and genetic diversity of circulating DENV isolates, captured prior to Chikungunya epidemic in 2014 and Zika epidemic in 2015. Our study findings underscore the need for continued surveillance and monitoring of dengue and other arboviruses and serve as epidemiological and molecular evidence base for future studies to assess changes in DENV transmission in Medellin, given emerging and re-emerging arboviral diseases in the region.