Cindy L. H. Kelly

Bio: Cindy L. H. Kelly is an academic researcher from Centers for Disease Control and Prevention. The author has contributed to research in topics: Stop codon & Anopheles gambiae. The author has an hindex of 3, co-authored 3 publications receiving 143 citations.

Infection patterns of o'nyong nyong virus in the malaria-transmitting mosquito, Anopheles gambiae.

Abstract: Arthropod-borne alphaviruses transmitted by mosquitoes almost exclusively use culicines; however, the alphavirus o'nyong-nyong (ONNV) has the unusual characteristic of being transmitted primarily by anopheline mosquitoes This unusual attribute makes ONNV a valuable tool in the characterization of mosquito determinants of infection as well as a useful expression system in Anopheles species We developed a series of recombinant alphaviruses, based upon the genome of ONNV, designed for the expression of heterologous genes The backbone genome is a full-length infectious cDNA clone of ONNV from which wild-type virus can be rescued Additional constructs are variants of the primary clone and contain the complete genome plus a duplicated subgenomic promoter element with a multiple cloning site for insertion of heterologous genes We inserted a green fluorescent protein (GFP) gene downstream of this promoter and used it to characterize infection and dissemination patterns of ONNV within An gambiae mosquitoes These experiments allowed us to identify atypical sites of initial infection and dissemination patterns in this mosquito species not frequently observed in comparable culicine infections The utility of these ONNVs for studies in anopheline mosquitoes includes the potential for identification of vector infection determinants and to serve as tools for antimalaria studies Viruses that can express a heterologous gene in a vector and rapidly and efficiently infect numerous tissues in An gambiae mosquitoes will be a valuable asset in parasite-mosquito interaction and interference research

Effects of an Opal Termination Codon Preceding the nsP4 Gene Sequence in the O'Nyong-Nyong Virus Genome on Anopheles gambiae Infectivity

Abstract: The genomic RNA of an alphavirus encodes four different nonstructural proteins, nsP1, nsP2, nsP3, and nsP4. The polyprotein P123 is produced when translation terminates at an opal termination codon between nsP3 and nsP4. The polyprotein P1234 is produced when translational readthrough occurs or when the opal termination codon has been replaced by a sense codon in the alphavirus genome. Evolutionary pressures appear to have maintained genomic sequences encoding both a stop codon (opal) and an open reading frame (arginine) as a general feature of the O'nyong-nyong virus (ONNV) genome, indicating that both are required at some point. Alternate replication of ONNVs in both vertebrate and invertebrate hosts may determine predominance of a particular codon at this locus in the viral quasispecies. However, no systematic study has previously tested this hypothesis in whole animals. We report here the results of the first study to investigate in a natural mosquito host the functional significance of the opal stop codon in an alphavirus genome. We used a full-length cDNA clone of ONNV to construct a series of mutants in which the arginine between nsP3 and nsP4 was replaced with an opal, ochre, or amber stop codon. The presence of an opal stop codon upstream of nsP4 nearly doubled (75.5%) the infectivity of ONNV over that of virus possessing a codon for the amino acid arginine at the corresponding position (39.8%). Although the frequency with which the opal virus disseminated from the mosquito midgut did not differ significantly from that of the arginine virus on days 8 and 10, dissemination did began earlier in mosquitoes infected with the opal virus. Although a clear fitness advantage is provided to ONNV by the presence of an opal codon between nsP3 and nsP4 in Anopheles gambiae, sequence analysis of ONNV RNA extracted from mosquito bodies and heads indicated codon usage at this position corresponded with that of the virus administered in the blood meal. These results suggest that while selection of ONNV variants is occurring, de novo mutation at the position between nsP3 and nsP4 does not readily occur in the mosquito. Taken together, these results suggest that the primary fitness advantage provided to ONNV by the presence of an opal codon between nsP3 and nsP4 is related to mosquito infectivity.

Pan-viral specificity of IFN-induced genes reveals new roles for cGAS in innate immunity

Abstract: The type I interferon (IFN) response protects cells from viral infection by inducing hundreds of interferon-stimulated genes (ISGs), some of which encode direct antiviral effectors. Recent screening studies have begun to catalogue ISGs with antiviral activity against several RNA and DNA viruses. However, antiviral ISG specificity across multiple distinct classes of viruses remains largely unexplored. Here we used an ectopic expression assay to screen a library of more than 350 human ISGs for effects on 14 viruses representing 7 families and 11 genera. We show that 47 genes inhibit one or more viruses, and 25 genes enhance virus infectivity. Comparative analysis reveals that the screened ISGs target positive-sense single-stranded RNA viruses more effectively than negative-sense single-stranded RNA viruses. Gene clustering highlights the cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS, also known as MB21D1) as a gene whose expression also broadly inhibits several RNA viruses. In vitro, lentiviral delivery of enzymatically active cGAS triggers a STING-dependent, IRF3-mediated antiviral program that functions independently of canonical IFN/STAT1 signalling. In vivo, genetic ablation of murine cGAS reveals its requirement in the antiviral response to two DNA viruses, and an unappreciated contribution to the innate control of an RNA virus. These studies uncover new paradigms for the preferential specificity of IFN-mediated antiviral pathways spanning several virus families.

Rodent-borne diseases and their risks for public health

Abstract: Rodents are the most abundant and diversified order of living mammals in the world. Already since the Middle Ages we know that they can contribute to human disease, as black rats were associated with distribution of plague. However, also in modern times rodents form a threat for public health. In this review article a large number of pathogens that are directly or indirectly transmitted by rodents are described. Moreover, a simplified rodent disease model is discussed.

Tissue Barriers to Arbovirus Infection in Mosquitoes.

Abstract: Arthropod-borne viruses (arboviruses) circulate in nature between arthropod vectors and vertebrate hosts. Arboviruses often cause devastating diseases in vertebrate hosts, but they typically do not cause significant pathology in their arthropod vectors. Following oral acquisition of a viremic bloodmeal from a vertebrate host, the arbovirus disease cycle requires replication in the cellular environment of the arthropod vector. Once the vector has become systemically and persistently infected, the vector is able to transmit the virus to an uninfected vertebrate host. In order to systemically infect the vector, the virus must cope with innate immune responses and overcome several tissue barriers associated with the midgut and the salivary glands. In this review we describe, in detail, the typical arbovirus infection route in competent mosquito vectors. Based on what is known from the literature, we explain the nature of the tissue barriers that arboviruses are confronted with in a mosquito vector and how arboviruses might surmount these barriers. We also point out controversial findings to highlight particular areas that are not well understood and require further research efforts.

Aedes aegypti uses RNA interference in defense against Sindbis virus infection

Abstract: RNA interference (RNAi) is an important anti-viral defense mechanism. The Aedes aegypti genome encodes RNAi component orthologs, however, most populations of this mosquito are readily infected by, and subsequently transmit flaviviruses and alphaviruses. The goal of this study was to use Ae. aegypti as a model system to determine how the mosquito's anti-viral RNAi pathway interacts with recombinant Sindbis virus (SINV; family Togaviridae, genus Alphavirus). SINV (TR339-eGFP) (+) strand RNA, infectious virus titers and infection rates transiently increased in mosquitoes following dsRNA injection to cognate Ago2, Dcr2, or TSN mRNAs. Detection of SINV RNA-derived small RNAs at 2 and 7 days post-infection in non-silenced mosquitoes provided important confirmation of RNAi pathway activity. Two different recombinant SINV viruses (MRE16-eGFP and TR339-eGFP) with significant differences in infection kinetics were used to delineate vector/virus interactions in the midgut. We show virus-dependent effects on RNAi component transcript and protein levels during infection. Monitoring midgut Ago2, Dcr2, and TSN transcript levels during infection revealed that only TSN transcripts were significantly increased in midguts over blood-fed controls. Ago2 protein levels were depleted immediately following a non-infectious bloodmeal and varied during SINV infection in a virus-dependent manner. We show that silencing RNAi components in Ae. aegypti results in transient increases in SINV replication. Furthermore, Ae. aegypti RNAi is active during SINV infection as indicated by production of virus-specific siRNAs. Lastly, the RNAi response varies in a virus-dependent manner. These data define important features of RNAi anti-viral defense in Ae. aegypti.

Alphavirus-derived small RNAs modulate pathogenesis in disease vector mosquitoes

Abstract: Mosquito-borne viruses cause significant levels of morbidity and mortality in humans and domesticated animals. Maintenance of mosquito-borne viruses in nature requires a biological transmission cycle that involves alternating virus replication in a susceptible vertebrate and mosquito host. Although the vertebrate infection is acute and often associated with disease, continual transmission of these viruses in nature depends on the establishment of a persistent, nonpathogenic infection in the mosquito vector. An antiviral RNAi response has been shown to limit the replication of RNA viruses in flies. However, the importance of the RNAi pathway as an antiviral defense in mammals is unclear. Differences in the immune responses of mammals and mosquitoes may explain why these viruses are not generally associated with pathology in the invertebrate host. We identified virus-derived small interfering RNAs (viRNAs), 21 nt in length, in Aedes aegypti infected with the mosquito-borne virus, Sindbis (SINV). viRNAs had an asymmetric distribution that spanned the length of the SINV genome. To determine the role of viRNAs in controlling pathogenic potential, mosquitoes were infected with recombinant alphaviruses expressing suppressors of RNA silencing. Decreased survival was observed in mosquitoes in which the accumulation of viRNAs was suppressed. These results suggest that an exogenous siRNA pathway is essential to the survival of mosquitoes infected with alphaviruses and, thus, the maintenance of these viruses in nature.