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B J Beaty

Publications and source records attributed to B J Beaty.

At least 19 recordsLinked to original sources
PubMed2000

Development of a Sindbis virus expression system that efficiently expresses green fluorescent protein in midguts of Aedes aegypti following per os infection.

A double subgenomic Sindbis (dsSIN) virus, MRE/3'2 J/GFP, was constructed to efficiently express green fluorescent protein (GFP) in the midgut of Aedes aegypti following per os infection. The MRE/3'2 J/GFP RNA genome contained the nonstructural genes and cis-acting sequences of the dsSIN virus, TE/3'2 J/GFP, but had the structural genes of MRE16 SIN virus. MRE/3'2 J/GFP virus, unlike TE/3'2 J/GFP virus, efficiently infected mosquitoes orally. At 1-2 days postinfection, GFP was observed as multiple foci of expression on the lumenal side of the midgut. At 10-12 days postinfection, thirteen of fifteen mosquitoes infected with MRE/3'2 J/GFP virus had high levels of GFP expression in the mosquito midgut. The MRE3'2 J dsSIN expression system should be an important tool for efficient gene expression in Ae. aegypti midguts.

Animals↗
PubMed2000

Molecular cloning and characterization of a metal responsive Aedes aegypti intestinal mucin cDNA.

We have isolated a cDNA from Aedes aegypti that is transcribed in the larval midgut in response to metal exposure, and in the adult female midgut in response to iron or cadmium exposure, or a blood meal. The cDNA encodes a protein, designated Aedes aegypti intestinal mucin 1 (AEIMUC1), which has similarities with invertebrate intestinal mucins and peritrophins, and vertebrate mucins. Proline, serine and threonine comprise 30% of the amino acid composition of AEIMUC1, a characteristic of mucins. AEIMUC1 contains three cysteine-rich domains, two of which flank a proline/serine/threonine-rich domain, a feature shared by many mucin genes. This is the first report on the isolation of a metal-responsive gene from an aquatic insect.

Aedes↗
PubMed2000

Potentiation of vesicular stomatitis New Jersey virus infection in mice by mosquito saliva.

Saliva of arthropod vectors can modulate vertebrate host immunological functions in many ways. To investigate if vesicular stomatitis New Jersey virus (VSNJ) infection could be potentiated by arthropod saliva, mice in three different age groups (3 days, 3 weeks, or > 8 months) were exposed to VSNJ-infected mosquitoes or were needle injected with an equivalent dose of VSNJ (titre 1.5-3 logs). Previous studies have demonstrated that VS viruses do not replicate in mice older than 3 weeks of age. Infection was monitored by examining serum for the presence of VSNJ at 2 days postinfection (PI) or for neutralizing antibody on days 7 and 14 PI. All 3-day-old mice succumbed to viral infection by mosquito transmission or delivery by injection. Ninety-four percent of the 3-week-old mice bitten by infected mosquitoes developed antibody, whereas antibody was detected in only 13% of inoculated mice. Adult mice developed neutralizing antibody (73%) when fed upon by infected mosquitoes, but only 11% developed antibody when virus was injected. Day 2 serum samples from 3-week and adult age groups were negative by virus isolation. These data indicate that mosquito mediated delivery of VSNJ exacerbates virus infection in mice older than 3 weeks.

Aedes↗
PubMed2000

Genetic isolation by distance among Aedes aegypti populations along the northeastern coast of Mexico.

A population genetic analysis of gene flow was conducted among 10 Aedes aegypti collections from seven cities along the northeastern coast of Mexico. Four collections were made from Monterrey to examine local patterns of gene flow. Markers included 60 random amplified polymorphic DNA (RAPD) loci amplified by the polymerase chain reaction and single strand conformation polymorphism analysis of variation in a 387-basepair region of the NADH dehydrogenase subunit 4 from the mitochondrial DNA (mtDNA). Seven mitochondrial haplotypes were detected and phylogenetic analysis identified two well-supported clades. Regression analysis of geographic distances and pairwise FST estimated from RAPD markers indicated that populations are isolated by distance and that free gene flow occurs among collections within 90-250 km. Isolation by distance was not detected using mtDNA haplotypes. The Nuevo Laredo collection had unique RAPD and mtDNA haplotype frequencies and reduced heterozygosity suggesting that few mosquitoes established this population.

Aedes↗
PubMed1999

Inhibition of luciferase expression in transgenic Aedes aegypti mosquitoes by Sindbis virus expression of antisense luciferase RNA.

A rapid and reproducible method of inhibiting the expression of specific genes in mosquitoes should further our understanding of gene function and may lead to the identification of mosquito genes that determine vector competence or are involved in pathogen transmission. We hypothesized that the virus expression system based on the mosquito-borne Alphavirus, Sindbis (Togaviridae), may efficiently transcribe effector RNAs that inhibit expression of a targeted mosquito gene. To test this hypothesis, germ-line-transformed Aedes aegypti that express luciferase (LUC) from the mosquito Apyrase promoter were intrathoracically inoculated with a double subgenomic Sindbis (dsSIN) virus TE/3'2J/anti-luc (Anti-luc) that transcribes RNA complementary to the 5' end of the LUC mRNA. LUC activity was monitored in mosquitoes infected with either Anti-luc or control dsSIN viruses expressing unrelated antisense RNAs. Mosquitoes infected with Anti-luc virus exhibited 90% reduction in LUC compared with uninfected and control dsSIN-infected mosquitoes at 5 and 9 days postinoculation. We demonstrate that a gene expressed from the mosquito genome can be inhibited by using an antisense strategy. The dsSIN antisense RNA expression system is an important tool for studying gene function in vivo.

Aedes↗
PubMed1999

Transduction of Aedes aegypti mosquitoes with vectors derived from Aedes densovirus.

Aedes densovirus (AeDNV)-based constructs that express green fluorescent protein (GFP) from either the P7 or the P61 promoter were made. The construct in which GFP protein was expressed as a fusion protein to the C-terminus of NS1 (NS1-GFP) showed the highest level of GFP expression. This hybrid NS1-GFP protein preserved the biological functions of the parental proteins: it showed GFP fluorescence, it stimulated expression from the virus promoters, and it facilitated rescue and replication of the cloned AeDNV genome. Similar to NS1, the hybrid NS1-GFP localized in the nucleus predominantly in a punctate pattern. Transducing virus particles carrying the NS1-GFP gene infected mosquito larvae. Expression of GFP was detected as early as 48 h postinfection and in larval and pupal stages. Midgut, hindgut, and Malpighian tubule cells expressed GFP soon after transduction. However, the anal papillae were the most commonly infected organ system. The anal papillae are syncytia and regulate ion concentration in the hemolymph of mosquito larvae, and they might be a novel route of mosquito larvae infection with densoviruses.

Aedes↗
PubMed1999

Packaging of AeDNV-GFP transducing virus by expression of densovirus structural proteins from a sindbis virus expression system.

Genetic recombination resulting in the production of wild-type infectious virus is an obstacle in the current system for producing densovirus transducing particles. In order to eliminate this problem, a double subgenomic Sindbis virus (TE/3'2J/VP) was engineered that expresses the structural proteins (VPs) of Aedes densonucleosis virus (AeDNV) from the second subgenomic promoter. Expression of AeDNV VPs from TE/3'2J/VP was confirmed by Northern analysis of RNA from infected C6/36 (Aedes albopictus) cells and by indirect immunofluorescence in infected C6/36 cells and BHK-21 cells. TE/3'2J/VP was used to infect C6/36 cells transfected with p7NS1-GFP, a plasmid expressing the nonstructural genes of AeDNV and green fluorescent protein (GFP) as a reporter gene. This infection resulted in the production of AeDNV-GFP transducing virus, which is infectious to C6/36 cells and Aedes aegypti larvae, as determined by GFP expression. The TE/3'2J/VP packaging system produced titers of transducing virus comparable to those produced by the standard two-plasmid method. The possibility of recombination resulting in wild-type infectious virus in transducing densovirus stocks was eliminated by employing an RNA virus expression system to supply AeDNV structural proteins.

Aedes↗
PubMed1999

Mosquito feeding modulates Th1 and Th2 cytokines in flavivirus susceptible mice: an effect mimicked by injection of sialokinins, but not demonstrated in flavivirus resistant mice.

Culex pipiens and Aedes aegypti mosquitoes were fed on C3H/HeJ mice and systemic cytokine production was quantified from stimulated lymphocytes harvested four to ten days after feeding. Mosquito feeding on C3H/HeJ mice significantly down regulated IFN gamma production seven to ten days post feeding by Cx. pipiens and seven days after Ae aegypti feeding. Th2 cytokines, IL-4 and IL-10, were significantly up regulated 4-7 days after Cx. pipiens and Ae. aegypti feeding. The immunosuppressive effect of Cx. pipiens feeding on systemic cytokine production was not evident in congenic flavivirus resistant (C3H/RV) mice, as systemic IFN gamma and IL-2 were significantly up regulated at days 7 and 10, correlating with a significant decrease in IL-4 10 days after feeding by Cx. pipiens mosquitoes. Inoculation of 5-1000 ng of sialokinin-I into C3H/HeJ mice mimicked the effect of Ae. aegypti feeding by down regulating Th1 cytokines and significantly up regulating Th2 cytokines four days post inoculation. Injections of sialokinin-II resulted in only moderate effects on IFN gamma and IL-4 production seven and ten days after injection. Thus natural feeding by two arbovirus vectors had a profound T cell modulatory effect in vivo in virus susceptible animals which was not demonstrated in the flavivirus resistant host. Moreover, sialokinin-I and sialokinin-II mimicked the effect of mosquito feeding by modulating the host T cell response. These results may lend new insight into specific aspects of the role of the mosquito vector in potentiating virus transmission in the mammalian host.

Aedes↗
PubMed1999

Selection of refractory and permissive strains of Aedes triseriatus (Diptera: Culicidae) for transovarial transmission of La Crosse virus.

The genetic basis of transovarial transmission of La Crosse virus in Aedes triseriatus (Say) was investigated through selection experiments on 2 mosquito strains. One strain was subject to selection for transovarial transmission refractoriness, the other for permissiveness to transovarial transmission. Response to selection for a low filial infection rate was rapid, decreasing from 18 to 3% in 3 generations. However, no response to selection for permissiveness was observed in the other strain; the average filial infection rates through 4 generations fluctuated between 25 and 40%. By contrast, the transovarial transmission rate in both strains showed a consistent response to selection in both directions. These patterns are consistent with a model in which transovarial transmission is controlled by a single genetic locus and permissiveness is conditioned by dominant alleles; whereas the filial infection rate is nongenetic and influenced by stochastic factors in the mosquito and virus.

Aedes↗
PubMed1999

La Crosse and other forms of California encephalitis.

The California serogroup viruses are mosquito viruses that cause human infections on five continents. They are maintained and amplified in nature by a wide variety of mosquito vectors and mammalian hosts; they thrive in a remarkably wide variety of microclimates (eg, tropical, coastal temperate marshland, lowland river valleys, alpine valleys and highlands, high boreal deserts, and arctic steppes). In 1993, California serogroup viruses caused 71% of all cases of arboviral illness in the United States, principally La Crosse encephalitis. The 30 to 180 annual cases of La Crosse encephalitis represent 8% to 30% of all cases of encephalitis, rendering this illness the most common and important endemic mosquito-borne illness in the USA. Subclinical or mild infections are much more common. Methods and results acquired from intense study of California serogroup viruses have been applied, with benefit, to the study of the ecology and pathogenesis of many more serious human arboviral illnesses. The evolutionary potential of viruses, with particular reference to the development of more virulent strains, has been studied more closely in the California serogroup viruses than in almost any other agent of human disease.

Animals↗
PubMed1999

Common occurrence of concurrent infections by multiple dengue virus serotypes.

The co-circulation of all 4 dengue virus serotypes in the same community, common since the 1950s in Southeast Asia, has now become a frequent occurrence in many Caribbean Islands, Mexico, and Central and South America in the past 20 years. As a consequence, the frequency of concurrent infections would be expected to increase in these areas. To assess this, using state of the art technology, we screened viremic serum samples and mosquitoes inoculated with serum samples collected during epidemics involving multiple dengue virus serotypes in Indonesia, Mexico, and Puerto Rico for virus isolation. Of 292 samples tested, 16 (5.5%) were found to contain 2 or more dengue viruses by an indirect immunofluorescence test and/or the reverse transcriptase-polymerase chain reaction.

Animals↗
PubMed1999

Relationships of deer mouse movement, vegetative structure, and prevalence of infection with Sin Nombre virus.

The effects of vegetative structure on movement of deer mice (Peromyscus maniculatus) were examined in two distinct vegetation associations, one near Hesperus and the other near Molina in western Colorado (USA) from June-October 1994 to October 1998. We monitored movement by live-trapping small mammals within Gambel's oak/mixed-grass (Hesperus) and sage brush/juniper (Molina) vegetation types. Vegetative structure differed between the sites with Molina having more cover provided by shrubs and Hesperus having more cover provided by forbs. Adult male deer mice moved greater distances at Hesperus than at Molina. Sub-adult males tended to move greater distances than did adult females. Relative abundances of deer mice tended to differ by season, but the average relative abundance of deer mice was greater at Molina. Long-term prevalence of infection with SNV was greater at Hesperus and was greatest in adult males at Hesperus (36.1%). Adult males at Molina exhibited a prevalence of infection with SNV of 25.0%. Infection with SNV was highly associated with scars or wounds for adult male, adult female, and juvenile male deer mice at Hesperus, but only for adult female deer mice at Molina. The presence of scars or wounds tended to be associated with greater age, but male deer mice at Hesperus were more likely to have wounds than female deer mice of the same age class. A similar pattern, excluding juveniles, was observed at Molina. Intraspecific interactions and environmentally elicited long-distance movements of deer mice may play a role in prevalence of infection with SNV in these animals.

Age Distribution↗
PubMed1998

Development of a chimeric sindbis virus with enhanced per Os infection of Aedes aegypti.

The TE/3'2J double subgenomic Sindbis (dsSIN) viruses have been used to stably express genes in Aedes aegypti nerve and salivary gland tissues. However, because these viruses inefficiently infect Ae. aegypti when administered by the per os route, TE/3'2J viruses must be intrathoracically inoculated into the mosquitoes to infect these tissues. A Malaysian Sindbis (SIN) virus isolate (MRE16) does efficiently infect Ae. aegypti midgut tissues after ingestion, and approximately 95% of these mosquitoes also develop disseminated infections within 14 days. We have sequenced the entire 26S RNA of MRE16 virus and have developed a chimeric SIN cDNA infectious clone, designated MRE1001, which contains sequence elements of TE/3'2J and MRE16 virus. MRE1001 virus efficiently infects midgut cells, and greater than 90% of infected mosquitoes develop disseminated infections after 14 days extrinsic incubation. The chimeric MRE1001 cDNA clone should allow identification of viral determinants of midgut infection and dissemination and lead to the development of new SIN virus expression systems.

Aedes↗
PubMed1998

Effect of heavy metals on Aedes aegypti (Diptera: Culicidae) larvae.

Studies were conducted to determine the biological effects of heavy metals on the development of Aedes aegypti. Embryos immersed in 32 ppm Cu or 5 ppm Cd did not hatch. The arrest of hatching was in part reversible by removal of the heavy metals. The mortality rate of third-instar larvae exposed to heavy metals for 24 h was metal and dose dependent; the 50% lethal concentration (LC50) endpoints were 3.1, 16.5, and 33 ppm for Hg, Cd, and Cu, respectively. Interestingly, a proportion of Aedes aegypti third-instar larvae exposed to either Cu or Cd for 24 h failed to produce a dissectable peritrophic matrix. This failure to produce a dissectable peritrophic matrix also was metal and dose dependent. These results are discussed in the context of Aedes aegypti as a model system for investigating the molecular biological effects of heavy metals in aquatic insects.

Aedes↗
PubMed1998

Use of the Sindbis replicon system for expression of LaCrosse virus envelope proteins in mosquito cells.

The Sindbis replicon expression system was used to express La Crosse (LAC) virus envelope glycoprotein genes in both mammalian and mosquito cell culture. Replicon expressed LAC proteins had correct molecular mass (Mr) and were antigenically similar to wild type LAC envelope proteins. In addition, LAC G1 and G2 proteins colocalized when expressed from separate constructs in both mammalian and mosquito cells suggesting that they were trafficked through the cell similarly to wild type LAC proteins. A truncated form of the G1 protein was secreted from mosquito cells when expressed alone. The truncated G1 protein was also secreted from mosquito cells when expressed with the G2 protein, but to a lesser extent than when expressed alone, suggesting that the G2 protein sequestered G1 protein intracellularly. The Sindbis replicon system is a powerful tool for the study of LAC virus protein maturation within mosquito cells and mosquitoes.

Aedes↗
PubMed1998

Mosquito feeding-induced enhancement of Cache Valley Virus (Bunyaviridae) infection in mice.

Cache-Valley (CV) virus, an arthropod-borne bunyavirus, recently has emerged as a significant veterinary pathogen causing infertility and congenital malformations in North American ruminants. To investigate the role of vector feeding on CV infection, adult mice were injected subcutaneously with CV, CV and vector thorax extract (a source of vector saliva), or CV into the site of intense, noninfected-mosquito feeding. Mice did not become infected after injection of CV or CV and vector saliva, nor did they produce antibodies to CV. However, injection of CV into sites of mosquito feeding resulted in viremia and production of anti-CV antibody by 2 wk after infection. This enhancement of CV infection resulted after feeding by Aedes triseriatus (Say), Ae. aegypti (L.), or Culex pipiens (L.). Enhancement occurred when injection was delayed up to 4 h after mosquito feeding, but it was not observed when virus injection was performed at a site distant from mosquito feeding. These results indicate that arbovirus infection may be enhanced by mosquito-vertebrate host interactions and that replication of arboviruses in arthropod vectors may not be responsible for increased virulence of infections mediated by infected arthropods. Enhanced CV infection in pregnant mice did not result in infertility or malformed pups, indicating that the mouse is not a suitable model to study CV-induced malformations.

Aedes↗
PubMed1998

La Crosse virus infection of Aedes triseriatus (Diptera: Culicidae) ovaries before dissemination of virus from the midgut.

La Crosse (LAC) virus is efficiently transmitted transovarially by the mosquito Aedes triseriatus (Say). To determine the time course and tropisms of LAC virus infection of ovaries, immunofluorescent antibody staining, in situ hybridization, and reverse transcription-polymerase chain reaction techniques were used to detect viral antigen and RNA in the ovaries. LAC virus was detected in the ovaries (presumably in calyx tissues) by all 3 assays at day 2 after infection and before dissemination from the midgut on day 6. Apparently, ovaries can become infected by mechanisms other than by dissemination of virus from a midgut infection. By days 8-14 after infection, virus analytes became detectable in many tissues within the ovary including follicular epithelium, oocytes, nurse cells, and calyx, reflecting the remarkable host parasite relationship between LAC virus and its mosquito vector.

Aedes↗