Dissecting the Role of E2 Protein Domains in Alphavirus Pathogenicity

Abstract

Alphaviruses represent a diverse set of arboviruses, many of which are important pathogens. Chikungunya virus (CHIKV), an arthritis-inducing alphavirus, is the cause of a massive ongoing outbreak in the Caribbean and South America. In contrast to CHIKV, other related alphaviruses, such as Venezuelan equine encephalitis virus (VEEV) and Semliki Forest virus (SFV), can cause encephalitic disease. E2, the receptor binding protein, has been implicated as a determinant in cell tropism, host range, pathogenicity, and immunogenicity. Previous reports also have demonstrated that E2 contains residues important for host range expansions and monoclonal antibody binding; however, little is known about what role each protein domain (e.g., A, B, and C) of E2 plays on these factors. Therefore, we constructed chimeric cDNA clones between CHIKV and VEEV or SFV to probe the effect of each domain on pathogenicity in vitro and in vivo. CHIKV chimeras containing each of the domains of the E2 (⌬DomA, ⌬DomB, and ⌬DomC) from SFV, but not VEEV, were successfully rescued. Interestingly, while all chimeric viruses were attenuated compared to CHIKV in mice, ⌬DomB virus showed similar rates of infection and dissemination in Aedes aegypti mosquitoes, suggesting differing roles for the E2 protein in different hosts. In contrast to CHIKV; ⌬DomB, and to a lesser extent ⌬DomA, caused neuron degeneration and demyelination in mice infected intracranially, suggesting a shift toward a phenotype similar to SFV. Thus, chimeric CHIKV/SFV provide insights on the role the alphavirus E2 protein plays on pathogenesis. T he alphaviruses represent a diverse family of arthropod-borne viruses (arboviruses), many of which are important veterinary or human pathogens. Their transmission cycles involve both an arthropod vector and vertebrate host, resulting in unique evolutionary restrictions. The genus Alphavirus (family Togaviridae) currently includes 29 species that are grouped into 10 complexes based on antigenic, genetic, and/or geographic similarities (1). The aquatic alphaviruses infect marine mammals and have been isolated in lice, although their role as a vector remains unknown (2). The New World alphaviruses include important veterinary and human pathogens, such as the equine encephalitis viruses, Venezuelan (VEEV), eastern (EEEV), and western (WEEV), all of which cause fatal encephalitic disease in both humans and animals such as horses and birds (3). The Old World alphaviruses, present mostly in Africa and Southeast Asia, are commonly associated with arthritic disease, fever, and rash. IMPORTANCE Chikungunya virus (CHIKV) has caused large outbreaks of acute and chronic arthritis throughout Africa and SoutheastChikungunya virus (CHIKV) is the most medically relevant Old World alphavirus and is the current cause of an outbreak of arthritic disease in the Americas, with more than 1 million cases in at least 44 countries, including the United States (4). CHIKV, which reemerged in 2004, has previously caused explosive epidemics of acute and chronic ...

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Suramin Inhibits Chikungunya Virus Replication by Interacting with Virions and Blocking the Early Steps of Infection

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