Therefore, the display of native and properly configured proteins on the surfaces of the VLPs appears to exhibit to the immune system a better antigenic array, which promotes the stimulation of a more diverse neutralizing response as we have seen with these VLP vaccine formulations. SR-13668 Suboptimal neutralizing antibody levels may contribute to antibody-enhancement of disease in dengue, which by phylogenetic analysis is closer to Zika than other flaviviruses. compositions of an inactivated Zika virus (In-ZIKV) used as a reference. VLP immunizations elicited high titers of antibodies, as did the In-ZIKV controls. However, in mice the VLP vaccine stimulated significantly higher virus neutralizing antibody titers than comparable formulations of the In-ZIKV vaccine. SR-13668 The serum neutralizing activity elicited by the VLP vaccine was enhanced using a higher VLP dose and with the addition of an adjuvant, reaching neutralizing titers greater than those detected in the serum of a patient who recovered from a Zika infection in Brazil in 2015. Discrepancies in neutralization levels between the VLP vaccine and the In-ZIKV suggest that chemical inactivation has deleterious effects on neutralizing epitopes within the E protein. This along with the inability of a VLP vaccine to cause infection makes it a preferable candidate for vaccine development. Author summary Zika is an emerging mosquito-borne infection for which vaccines or specific treatments are not available SR-13668 to combat and control its rapid dissemination and deleterious effects. This work describes a novel strategy for the development of a virus-like particle (VLP) based Zika vaccine and shows its effectiveness when tested in a murine model. VLPs are non-infections mimics of the Zika virus, thus chemical inactivation is not required. A VLP vaccine is able to maintain native epitopes structures and to perform better than an inactivated Zika virus control. Our results show feasibility for the rapid development of a safe and potentially highly effective VLP based Zika vaccine for humans. Introduction Zika fever results from an infection with the Zika virus (ZIKV), which is transmitted to humans by the bite of an infected Aedes mosquito (primarily A. aegypti). Zika virus was isolated for the first time from a Rhesus monkey in the Zika Forest in Uganda in 1947 and later from humans in Africa in 1952 [1]. The ZIKV has been transmitted in Africa for many years through a sylvatic cycle between mosquito vectors and nonhuman primates, with occasional human infections [2]. In recent years, however, epidemics of Zika have resulted from cycles of transmission between vectors and humans resulting in the spread of disease beyond the African continent into French SR-13668 Polynesia and other Pacific regions [3C5]. Since 2015, a dramatic spread of ZIKV that began in Brazil has taken place in South America and the Caribbean Islands with the occurrence of sporadic cases in travelers identified in the USA and Europe [6]. Currently autochthonous infections have been reported in the continental US (Florida) [7]. Infection in most cases is asymptomatic or produces a mild illness. However, contracting the virus during pregnancy is associated with birth defects, primarily microcephaly (defective brain development) as well as eye defects and hearing deficits in the infant [8]. Furthermore, an increase in cases of Guillain-Barre syndrome has been observed following ZIKV infection [9]. The seriousness of these disorders imposes a tremendous burden on public health. In addition to vector transmission, ZIKV is transmitted via sexual contact [10, 11], and by body fluid [12C14]. These facts taken together with its often-asymptomatic nature makes disease control even more difficult. Zika virus is a member of the flavivirus genus within the Flaviviridae family. This family consists of a large group of enveloped viruses, which includes dengue, yellow fever, West Nile, Japanese encephalitis and others that SMARCA6 possess a single stranded RNA genome of positive polarity, which serves as mRNA upon the infection of susceptible cells. The ZIKV RNA genome encodes one open reading frame (ORF, ~10,272 nt) and translates into a single polyprotein that similarly to other flaviviruses is co- and post-translationally cleaved by cellular and virus-encoded proteases into three structural proteins (C, prM and E) and into seven non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5.) that enable virus replication (Fig 1A) [15, 16]. Flavivirus replication and morphogenesis occurs in close association with intracellular membranes. Nascent virions are assembled and transported through the secretory pathway and released at the cell surface. Enveloped virions are composed of a cell-derived lipid bilayer encapsulating the C-protein wrapped viral RNA genome and studded with 180 copies of the proteins E and M. During maturation within the secretory pathway the precursor prM protein is cleaved by the host cell furin protease to produce the small M protein and the fragment pr, which is released upon virus egress from the cell. The viral surface.