Alphaviruses are widely distributed in both hemispheres and circulate between mosquitoes and amplifying vertebrate hosts. Geographically separated alphaviruses have adapted to replication in particular organisms. The accumulating data suggest that this adaptation is determined not only by changes in their glycoproteins, but also by the amino acid sequence of the hypervariable domain (HVD) of the alphavirus nsP3 protein. We performed a detailed investigation of chikungunya virus (CHIKV) nsP3 HVD interactions with host factors and their roles in viral replication in vertebrate and mosquito cells. The results demonstrate that CHIKV HVD is intrinsically disordered and binds several distinctive cellular proteins. These host factors include two members of the G3BP family and their mosquito homolog Rin, two members of the NAP1 family and several SH3 domain-containing proteins. Interaction with G3BP proteins or Rin is an absolute requirement for CHIKV replication, although it is insufficien...

Zika virus (ZIKV) is an emergent mosquito-borne member of the Flaviviridae family that was responsible for a recent epidemic in the Americas. ZIKV has been associated with severe clinical complications, including neurological disorder such as Guillain-Barré syndrome in adults and severe fetal abnormalities and microcephaly in newborn infants. Given the significance of these clinical manifestations, the development of tools and reagents to study the pathogenesis of ZIKV and to develop new therapeutic options are urgently needed. In this respect, the implementation of reverse genetic techniques has allowed the direct manipulation of the viral genome to generate recombinant (r)ZIKVs, which have provided investigators with powerful systems to answer important questions about the biology of ZIKV, including virus-host interactions, the mechanism of transmission and pathogenesis or the function of viral proteins. In this review, we will summarize the different reverse genetic strategies th...

In addition to conventional vaccine development for infectious diseases, nucleic acidbased vaccine approaches have recently been presented as serious alternatives to previously used strategies based on live attenuated virus particles and subunit vaccines. Particularly, RNA-based vaccines have proven attractive. In this context, immunization with messenger RNA (mRNA) has provided strong immune responses and protection against challenges with lethal doses of pathogenic viruses in vaccinated animals. Alternatively, the efficient RNA replication mechanism provided by self-amplifying RNA (saRNA) viruses has been utilized. Enhanced immune responses with reduced doses required for immunization has been obtained in comparison to conventional mRNA administration. The rapid spread and destruction caused by the COVID-19 pandemic has substantially accelerated the demand for the development of robust and efficient vaccines against SARS-CoV-2. Both mRNA-and saRNA-based COVID-19 vaccine candidates are currently in human clinical trials.

Chikungunya virus (CHIKV) is a reemerging alphavirus that causes a debilitating arthritic disease and infects millions of people and for which no specific treatment is available. Like many alphaviruses, the structural targets on CHIKV that elicit a protective humoral immune response in humans are poorly defined. Here we used phage display against virus-like particles (VLPs) to isolate seven human monoclonal antibodies (MAbs) against the CHIKV envelope glycoproteins E2 and E1. One MAb, IM-CKV063, was highly neutralizing (50% inhibitory concentration, 7.4 ng/ml), demonstrated high-affinity binding (320 pM), and was capable of therapeutic and prophylactic protection in multiple animal models up to 24 h postexposure. Epitope mapping using a comprehensive shotgun mutagenesis library of 910 mutants with E2/E1 alanine mutations demonstrated that IM-CKV063 binds to an intersubunit conformational epitope on domain A, a functionally important region of E2. MAbs against the highly conserved fu...

Zika virus (ZIKV) is an emerging human mosquito-transmitted pathogen of global concern, known to cause severe complications such as congenital defects and neurological disorders in adults. ZIKV infection is associated with cell death. However, previous studies suggest that the virally-induced apoptosis occurs at a slower rate compared to the course of viral production. In this present study, we investigated the capacity of ZIKV to delay host cell apoptosis. We provide evidence that ZIKV has the ability to control programmed cell death whether it is intrinsically or extrinsically induced. In cells expressing viral replicon-type constructions, we show that this control is achieved through replication. Finally, our work highlights an important role for anti-apoptotic Bcl-2 family protein in the ability of ZIKV to control apoptotic pathways, avoiding premature cell death and thereby promoting virus replication in the host-cell.

Abstract. Successful infection by enveloped viruses relies on the capacity of these pathogens to release their genome in the cytoplasm. This process involves several successive steps including the recruitment of attachment factors by the viral particle, interaction of viral glycoproteins with specific receptors and fusion of virus and host membranes. Drugs and inhibitors capable to interrupt the infectious cycle by targeting viral or cellular components involved in the entry process have a considerable interest for the development of antiviral strategies susceptible to interrupt replication at the earliest time. The development of such molecules is underpinned by the elucidation of the host-virus interplay engaged during these steps and by the characterization of the molecular mechanism governing viral entry. In this chapter, we focus on the mechanisms used by chikungunya virus (CHIKV), a medically important mosquito-borne alphavirus propagating in many parts of the world, to penetrate into its target cells. The knowledge accumulated on the nature of receptors and endocytic routes hijacked by this pathogen to infect mammalian and mosquito cells is discussed and we summarize the most recent advances in the development of drugs and antibodies targeting CHIKV replication at the receptor binding, internalization and fusion steps.