Mosquitoes of Northwestern Uganda

Despite evidence of arbovirus activity in northwestern Uganda (West Nile Sub-region), there is very limited information on the mosquito fauna of this region. The only published study reported 52 mosquito species in northwestern Uganda but this study took place in 1950 and the information has not been updated for more than 60 yr. In January and June 2011, CO2 baited-light traps were used to collect 49,231 mosquitoes from four different locations, Paraa (9,487), Chobe (20,025), Sunguru (759), and Rhino Camp (18,960). Overall, 72 mosquito species representing 11 genera were collected. The largest number of distinct species was collected at Chobe (43 species), followed by Paraa (40), Sunguru (34), and Rhino Camp (25). Only eight of the 72 species (11.1%) were collected from all four sites: Aedes (Stegomyia) aegypti formosus (Walker), Anopheles (Cellia) funestus group, Culex (Culex) decens group, Cx. (Culex) neavei Theobald, Cx. (Culex) univittatus Theobald, Cx. (Culiciomyia) cinereus Theobald, Cx. (Oculeomyia) poicilipes (Theobald), and Mansonia (Mansonoides) uniformis (Theobald). Fifty-four species were detected in northwestern Uganda for the first time; however, these species have been detected elsewhere in Uganda and do not represent new introductions to the country. Thirty-three species collected during this study have previously been implicated in the transmission of arboviruses of public health importance.

Study of viremic profile in febrile specimens of chikungunya in Bandung, Indonesia

BACKGROUND

Data regarding the viremia profile of chikungunya virus (CHIKV) infected patients especially during the pre-febrile period is limited.

OBJECTIVE

To obtain virological kinetic data on CHIKV infections.

STUDY DESIGN

A two-week community observation for dengue transmission was conducted in Bandung, Indonesia, from 2005 to 2009. Acute specimens from non-dengue febrile patients were screened by pan-alphavirus conventional RT-PCR. The positives were confirmed for CHIKV RNA by a specific RT-PCR followed by sequencing. Simultaneously these specimens were also cultured in Vero cells and tested for anti-CHIK IgM MAC-ELISA. All the available serial specimens,including the pre-febrile specimens, from confirmed CHIK cases, were tested by virus isolation, RT-PCR, qRT-PCR, and CHIK IgM ELISA.

RESULTS

There were five laboratory confirmed CHIK cases identified and studied. Among these, viremia was determined to extend from as early as 6 days prior to until 13 days post fever onset. Quantitative RT-PCR showed viremia peaked at or near onset of illness.

CONCLUSION

In this study, individuals were identified with viremia prior to fever onset and extending beyond the febrile phase. This extended viremic phase has the potential to impact transmission dynamics and thus the public health response to CHIK outbreaks.

Mosquitoes of western Uganda

The mosquito fauna in many areas of western Uganda has never been studied and is currently unknown. One area, Bwamba County, has been previously studied and documented but the species lists have not been updated for >40 yr. This paucity of data makes it difficult to determine which arthropod-borne viruses pose a risk to human or animal populations. Using CO2 baited-light traps, from 2008 through 2010, 67,731 mosquitoes were captured at five locations in western Uganda including Mweya, Sempaya, Maramagambo, Bwindi (BINP), and Kibale (KNP). Overall, 88 mosquito species, 7 subspecies, and 7 species groups in 10 genera were collected. The largest number of species was collected at Sempaya (65 species), followed by Maramagambo (45), Mweya (34), BINP (33), and KNP (22). However, species diversity was highest in BINP (Simpson's Diversity Index 1-D = 0.85), followed by KNP (0.80), Maramagambo (0.79), Sempaya (0.67), and Mweya (0.56). Only six species Aedes (Aedimorphus) cumminsii (Theobald), Aedes (Neomelaniconion) circumluteolus (Theobald), Culex (Culex) antennatus (Becker), Culex (Culex) decens group, Culex (Lutzia) tigripes De Grandpre and De Charmoy, and Culex (Oculeomyia) annulioris (Theobald), were collected from all five sites suggesting large differences in species composition among sites. Four species (Aedes (Stegomyia) metallicus (Edwards), Anopheles (Cellia) rivulorum Leeson, Uranotaenia (Uranotaenia) chorleyi (Edwards), and Uranotaenia (Uranotaenia) pallidocephala (Theobald) and one subspecies (Aedes (Stegomyia) aegypti formosus (Walker)) were collected in Bwamba County for the first time. This study represents the first description of the mosquito species composition of Mweya, Maramagambo, BINP, and KNP. A number of morphological variations were noted regarding the postspiracular scales, hind tibia, and sternites that make Culex (Culex) neavei (Theobald) challenging to identify. At least 50 species collected in this study have previously been implicated in the transmission of arboviruses of public health importance suggesting a high potential for maintenance and transmission of a wide variety of arboviruses in western Uganda.

Alphaviruses

Alphaviruses remain important emerging mosquito-borne, zoonotic pathogens that cause both localized human outbreaks and epizootics (e.g., Venezuelan equine encephalitis) and large human epidemics (e.g., Chikungunya). Alphaviruses are globally dispersed, and each continent has humans at risk from one or more of these arthropod-borne viruses (arboviruses). Symptoms of human alphaviral disease range from frank, severe encephalitis (e.g., eastern and western equine encephalitis) to polyarthritis (e.g., Ross River). Diagnostic techniques to identify human alphaviral infections have changed dramatically with the development and implementation of standardized nucleic acid amplification tests (NAAT). The NAAT is rapidly replacing virus isolation and typing using indirect fluorescent antibody (IFA) assay with monoclonal antibodies (MAbs) as the preferred method of virus identification. The older techniques still have value, however, since alphaviral growth in cell culture is rapid, and IFA with MAbs is inexpensive. This chapter provides detailed, standardized protocols for the identification of alphaviruses from clinical specimens and the serological characterization of human infection-immune sera. Both laboratory approaches are needed to identify and confirm human infections with these agents.

Tracking epidemic Chikungunya virus into the Indian Ocean from East Africa

The largest documented outbreak of Chikungunya virus (CHIKV) disease occurred in the Indian Ocean islands and India during 2004-2007. The magnitude of this outbreak led to speculation that a new variant of the virus had emerged that was either more virulent or more easily transmitted by mosquito vectors. To study this assertion, it is important to know the origin of the virus and how the particular strain circulating during the outbreak is related to other known strains. This study genetically characterized isolates of CHIKV obtained from Mombasa and Lamu Island, Kenya, during 2004, as well as strains from the 2005 outbreak recorded in Comoros. The results of these analyses demonstrated that the virus responsible for the epidemic that spread through the Indian Ocean originated in coastal Kenya during 2004 and that the closest known ancestors are members of the Central/East African clade. Genetic elements that may be responsible for the scope of the outbreak were also identified.

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

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.

Genetic determinants of Venezuelan equine encephalitis emergence

Following a period of inactivity from 1973-1991, Venezuelan equine encephalitis (VEE) reemerged during the past decade in South America and Mexico. Experimental studies of VEE virus (VEEV) infection of horses with virus strains isolated during these outbreaks have revealed considerable variation in the ability of equine-virulent, epizootic strains to exploit horses as efficient amplification hosts. Subtype IC strains from recent outbreaks in Venezuela and Colombia amplify efficiently in equines, with a correlation between maximum viremia titers and the extent of the outbreak from which the virus strain was isolated. Studies of enzootic VEEV strains that are believed to represent progenitors of the epizootic subtypes support the hypothesis that adaptation to efficient replication in equines is a major determinant of emergence and the ability of VEEV to spread geographically. Correlations between the ability of enzootic and epizootic VEEV strains to infect abundant, equiphilic mosquitoes, and the location and extent of these outbreaks, also suggest that specific adaptation to Ochlerotatus taeniorhynchus mosquitoes is a determinant of some but not all emergence events. Genetic studies imply that mutations in the E2 envelope glycoprotein gene are major determinants of adaptation to both equines and mosquito vectors.

Isolation of chikungunya virus from Aedes aegypti mosquitoes collected in the town of Yawat, Pune District, Maharashtra State, India

Chikungunya (CHIK) virus is prevalent throughout Southeast Asia and Africa. It has caused numerous large outbreaks in India. No active or passive surveillance has been carried out since the last epidemic occurring in 1971. During a recent outbreak of Dengue (DEN)-like illness in eastern India, Aedes aegypti mosquitoes collected from the affected area were positive for CHIK virus. Evidence of dual infection with CHIK and DEN typel virus was also obtained. A widely circulating low-virulent CHIK virus is a possible explanation for the epidemiological pattern of the CHIK virus disease in this region.

Evolutionary relationships and systematics of the alphaviruses

Partial E1 envelope glycoprotein gene sequences and complete structural polyprotein sequences were used to compare divergence and construct phylogenetic trees for the genus Alphavirus. Tree topologies indicated that the mosquito-borne alphaviruses could have arisen in either the Old or the New World, with at least two transoceanic introductions to account for their current distribution. The time frame for alphavirus diversification could not be estimated because maximum-likelihood analyses indicated that the nucleotide substitution rate varies considerably across sites within the genome. While most trees showed evolutionary relationships consistent with current antigenic complexes and species, several changes to the current classification are proposed. The recently identified fish alphaviruses salmon pancreas disease virus and sleeping disease virus appear to be variants or subtypes of a new alphavirus species. Southern elephant seal virus is also a new alphavirus distantly related to all of the others analyzed. Tonate virus and Venezuelan equine encephalitis virus strain 78V3531 also appear to be distinct alphavirus species based on genetic, antigenic, and ecological criteria. Trocara virus, isolated from mosquitoes in Brazil and Peru, also represents a new species and probably a new alphavirus complex.

Virulence and viremia characteristics of 1992 epizootic subtype IC Venezuelan equine encephalitis viruses and closely related enzootic subtype ID strains

Following a 19-year hiatus, Venezuelan equine encephalitis (VEE) reemerged in western Venezuela in December 1992. This outbreak is important in understanding VEE emergence because phylogenetic studies imply that sympatric, enzootic, subtype ID VEE viruses mutated to generate the epizootic/epidemic. Although the 1992-1993 strains belong to subtype IC, a serotype implicated in extensive outbreaks during the 1960s and in 1995, relatively small numbers of human and equine cases occurred in 1992-1993. We, therefore, evaluated the pathogenicity of these Venezuelan enzootic ID and epizootic IC viruses to determine 1) if they exhibit phenotypes like those described previously for more distantly related enzootic and epizootic strains, and 2) if the 1992-1993 outbreak was limited by the inability of these IC viruses to exploit equines as amplification hosts. All strains were virulent in mice and guinea pigs, but were benign for cotton rats, natural hosts of enzootic viruses. However, only the IC strains produced equine disease, with mean peak viremias of 10(5) suckling mouse 50% lethal doses per mL serum, and some titers exceeding 10(7). These viremias approximate those observed previously with VEE strains isolated during more extensive epizootics, suggesting that efficient equine amplification did not limit the scope and duration of the 1992-1993 outbreak. Enzootic ID virus infection protected all horses from challenge with epizootic strain P676, supporting the hypothesis that epizootics bypass regions of enzootic transmission due to natural immunization of equines by enzootic VEE viruses.

Potential sources of the 1995 Venezuelan equine encephalitis subtype IC epidemic

Venezuelan equine encephalitis viruses (VEEV) belonging to subtype IC have caused three (1962-1964, 1992-1993 and 1995) major equine epizootics and epidemics. Previous sequence analyses of a portion of the envelope glycoprotein gene demonstrated a high degree of conservation among isolates from the 1962-1964 and the 1995 outbreaks, as well as a 1983 interepizootic mosquito isolate from Panaquire, Venezuela. However, unlike subtype IAB VEEV that were used to prepare inactivated vaccines that probably initiated several outbreaks, subtype IC viruses have not been used for vaccine production and their conservation cannot be explained in this way. To characterize further subtype IC VEEV conservation and to evaluate potential sources of the 1995 outbreak, we sequenced the complete genomes of three isolates from the 1962-1964 outbreak, the 1983 Panaquire interepizootic isolate, and two isolates from 1995. The sequence of the Panaquire isolate, and that of virus isolated from a mouse brain antigen prepared from subtype IC strain P676 and used in the same laboratory, suggested that the Panaquire isolate represents a laboratory contaminant. Some authentic epizootic IC strains isolated 32 years apart showed a greater degree of sequence identity than did isolates from the same (1962-1964 or 1995) outbreak. If these viruses were circulating and replicating between 1964 and 1995, their rate of sequence evolution was at least 10-fold lower than that estimated during outbreaks or that of closely related enzootic VEEV strains that circulate continuously. Current understanding of alphavirus evolution is inconsistent with this conservation. This subtype IC VEEV conservation, combined with phylogenetic relationships, suggests the possibility that the 1995 outbreak was initiated by a laboratory strain.

Trocara virus: a newly recognized Alphavirus (Togaviridae) isolated from mosquitoes in the Amazon Basin

This report describes Trocara virus, a newly recognized member of the genus Alphavirus, that has been isolated from Aedes serratus mosquitoes collected at two widely separated sites in the Amazon Basin. Biological, antigenic and genetic characteristics of the new virus are given. Results of these studies indicate that Trocara virus is the first member of a newly discovered antigenic complex within the family Togaviridae genus Alphavirus. The public health and veterinary importance of Trocara virus is still unknown.

The use of chimeric Venezuelan equine encephalitis viruses as an approach for the molecular identification of natural virulence determinants

Venezuelan equine encephalitis (VEE) virus antigenic subtypes and varieties are considered either epidemic/epizootic or enzootic. In addition to epidemiological differences between the epidemic and enzootic viruses, several in vitro and in vivo laboratory markers distinguishing the viruses have been identified, including differential plaque size, sensitivity to interferon (IFN), and virulence for guinea pigs. These observations have been shown to be useful predictors of natural, equine virulence and epizootic potential. Chimeric viruses containing variety IAB (epizootic) nonstructural genes with variety IE (enzootic) structural genes (VE/IAB-IE) or IE nonstructural genes and IAB structural genes (IE/IAB) were constructed to systematically analyze and map viral phenotype and virulence determinants. Plaque size analysis showed that both chimeric viruses produced a mean plaque diameter that was intermediate between those of the parental strains. Additionally, both chimeric viruses showed intermediate levels of virus replication and virulence for guinea pigs compared to the parental strains. However, IE/IAB produced a slightly higher viremia and an average survival time 2 days shorter than the VE/IAB-IE virus. Finally, IFN sensitivity assays revealed that only one chimera, VE/IAB-IE, was intermediate between the two parental types. The second chimera, containing the IE nonstructural genes, was at least five times more sensitive to IFN than the IE parental virus and greater than 50 times more sensitive than the IAB parent. These results implicate viral components in both the structural and nonstructural portions of the genome in contributing to the epizootic phenotype and indicate the potential for epidemic emergence from the IE enzootic VEE viruses.

Re-emergence of Chikungunya and O'nyong-nyong viruses: evidence for distinct geographical lineages and distant evolutionary relationships

Chikungunya (CHIK) virus is a member of the genus Alphavirus in the family TOGAVIRIDAE: Serologically, it is most closely related to o'nyong-nyong (ONN) virus and is a member of the Semliki Forest antigenic complex. CHIK virus is believed to be enzootic throughout much of Africa and historical evidence indicates that it spread to other parts of the world from this origin. Strains from Africa and Asia are reported to differ biologically, indicating that distinct lineages may exist. To examine the relatedness of CHIK and ONN viruses using genetic data, we conducted phylogenetic studies on isolates obtained throughout Africa and Southeast Asia. Analyses revealed that ONN virus is indeed distinct from CHIK viruses, and these viruses probably diverged thousands of years ago. Two distinct CHIK virus lineages were delineated, one containing all isolates from western Africa and the second comprising all southern and East African strains, as well as isolates from Asia. Phylogenetic trees corroborated historical evidence that CHIK virus originated in Africa and subsequently was introduced into Asia. Within the eastern Africa and southern Africa/Asia lineage, Asian strains grouped together in a genotype distinct from the African groups. These different geographical genotypes exhibit differences in their transmission cycles: in Asia, the virus appears to be maintained in an urban cycle with Aedes aegypti mosquito vectors, while CHIK virus transmission in Africa involves a sylvatic cycle, primarily with AE: furcifer and AE: africanus mosquitoes.

Motivations for condom use: do pregnancy prevention goals undermine disease prevention among heterosexual young adults?

Differences in motives for condom use and their implications for understanding frequency of use were investigated in a random, biracial (Black, White) sample of heterosexuals, aged 17 to 25 years (n = 902). Results indicated that sexually active young adults-regardless of race, age, gender, or relationship status-were more likely to use condoms to prevent pregnancy than to prevent disease. Reasons for use mediated the effects of relationship status on condom use per se and moderated the effects of attitudinal and perceptual variables on condom use. Finally, comparisons among condom users motivated by different prevention goals and nonusers (n = 388) revealed that differences among user subgroups were nearly as numerous and, in some cases, more robust than differences between users and nonusers. These findings indicate that condom users comprise distinct subgroups, defined in part by their underlying motives for use, and highlight important conceptual and empirical reasons to distinguish among them.

Genetic and antigenic diversity among eastern equine encephalitis viruses from North, Central, and South America

Eastern equine encephalitis virus (EEEV), the sole species in the EEE antigenic complex, is divided into North and South American antigenic varieties based on hemagglutination inhibition tests. Here we describe serologic and phylogenetic analyses of representatives of these varieties, spanning the entire temporal and geographic range available. Nucleotide sequencing and phylogenetic analyses revealed additional genetic diversity within the South American variety; 3 major South/Central American lineages were identified including one represented by a single isolate from eastern Brazil, and 2 lineages with more widespread distributions in Central and South America. All North American isolates comprised a single, highly conserved lineage with strains grouped by the time of isolation and to some extent by location. An EEEV strain isolated during a 1996 equine outbreak in Tamaulipas State, Mexico was closely related to recent Texas isolates, suggesting southward EEEV transportation beyond the presumed enzootic range. Plaque reduction neutralization tests with representatives from the 4 major lineages indicated that each represents a distinct antigenic subtype. A taxonomic revision of the EEE complex is proposed.

Motivations for condom use: do pregnancy prevention goals undermine disease prevention among heterosexual young adults?

Differences in motives for condom use and their implications for understanding frequency of use were investigated in a random, biracial (Black, White) sample of heterosexuals, aged 17 to 25 years (n = 902). Results indicated that sexually active young adults-regardless of race, age, gender, or relationship status-were more likely to use condoms to prevent pregnancy than to prevent disease. Reasons for use mediated the effects of relationship status on condom use per se and moderated the effects of attitudinal and perceptual variables on condom use. Finally, comparisons among condom users motivated by different prevention goals and nonusers (n = 388) revealed that differences among user subgroups were nearly as numerous and, in some cases, more robust than differences between users and nonusers. These findings indicate that condom users comprise distinct subgroups, defined in part by their underlying motives for use, and highlight important conceptual and empirical reasons to distinguish among them.

Isolation and genetic characterization of a hantavirus (Bunyaviridae: Hantavirus) from a rodent, Oligoryzomys microtis (Muridae), collected in northeastern Peru

This paper describes the isolation and partial genetic characterization of a hantavirus from a pygmy rice rat, Oligoryzomys microtis, collected within the urban area of Iquitos, Loreto Department, Peru. The virus, designated HTN-007, exhibited the highest degree of genetic similarity to Rio Mamore virus, which was originally described from the same rodent species in eastern Bolivia. Comparison of small and medium segment nucleotide sequence data from HTN-007 and Rio Mamore virus revealed 87% and 85% sequence identity, respectively. Based on these analyses, HTN-007 appears to be a variant of Rio Mamore virus. As such, it represents the first successful isolation of Rio Mamore virus and the first evidence for the existence of a hantavirus in Peru. Serologic studies done by immunofluorescence on blood samples of 56 O. microtis trapped at the collection site indicated that 21.4% had antibodies to hantavirus. In view of the proximity of this rodent species to humans and the close phylogenetic relationship of Rio Mamore virus to hantaviruses that have been associated with human disease, Rio Mamore virus may be a hantavirus of some public health importance in tropical South America.

Motivations for sex and risky sexual behavior among adolescents and young adults: a functional perspective

The implications of a functionalist perspective for understanding sexual risk taking are explored. Key motivational dimensions thought to underlie human behavior (viz., approach vs. avoidance, autonomy vs. relatedness) were used to identify 4 broad domains of sexual motivations and to develop a measure of specific motives within each of these domains. Data from both college student and community samples are used to demonstrate the psychometric adequacy of these scales and to show that having sex for different reasons predicts distinctive patterns of sexual risk taking both cross-sectionally and longitudinally: that selection into specific types of sexual relationships partially mediates these effects; and that these needs may be differentially expressed, or even suppressed, depending on relationship context. Results provide strong support for the functionalist perspective on behavior and indicate that an adequate understanding of sexual risk-taking behavior must take into account the various needs and goals that such behavior can serve.

Molecular epidemiological studies of veterinary arboviral encephalitides

Recent studies using molecular genetic approaches have made important contributions to our understanding of the epidemiology of veterinary arboviral encephalitides. Viruses utilizing avian enzootic hosts, such as Western equine encephalitis virus (WEEV) and North American Eastern equine encephalitis virus (EEEV), evolve as relatively few, highly conserved genotypes that extend over wide geographic regions; viruses utilizing mammalian hosts with more limited dispersal evolve within multiple genotypes, each geographically restricted. Similar findings have been reported for Australian alphaviruses. This difference may be related to vertebrate host relationships and the relative mobility of mammals and avians. Whereas EEEV and Venezualan equine encephalitis virus (VEEV) utilize small mammalian hosts in the tropics, most WEEV genotypes probably utilize avian hosts in both North and South America. The ability of mobile, infected avian hosts to disperse alphaviruses may result in continual mixing of virus populations, and thus limit diversification. This high degree of genetic conservation is also exhibited by EEE and Highlands J viruses in North America, where passerine birds serve as amplifying hosts in enzootic transmission foci. Most equine arboviral pathogens, including EEEV, WEEV and Japanese encephalitis virus (JEV), occur in a naturally virulent enzootic state and require only appropriate ecological conditions to cause epizootics and epidemics. However, VEE epizootics apparently require genetic changes to convert avirulent enzootic strains into distinct epizootic serotypes. All of these arboviruses have the potential to cause severe disease of veterinary and human health importance, and further molecular epidemiological studies will undoubtedly improve our ability to understand and control future emergence.

Mayaro virus disease: an emerging mosquito-borne zoonosis in tropical South America

This report describes the clinical, laboratory, and epidemiological findings on 27 cases of Mayaro virus (MV) disease, an emerging mosquito-borne viral illness that is endemic in rural areas of tropical South America. MV disease is a nonfatal, dengue-like illness characterized by fever, chills, headache, eye pain, generalized myalgia, arthralgia, diarrhea, vomiting, and rash of 3-5 days' duration. Severe joint pain is a prominent feature of this illness; the arthralgia sometimes persists for months and can be quite incapacitating. Cases of two visitors from the United States, who developed MV disease during visits to eastern Peru, are reported. MV disease and dengue are difficult to differentiate clinically.

Motivations for sex and risky sexual behavior among adolescents and young adults: a functional perspective

The implications of a functionalist perspective for understanding sexual risk taking are explored. Key motivational dimensions thought to underlie human behavior (viz., approach vs. avoidance, autonomy vs. relatedness) were used to identify 4 broad domains of sexual motivations and to develop a measure of specific motives within each of these domains. Data from both college student and community samples are used to demonstrate the psychometric adequacy of these scales and to show that having sex for different reasons predicts distinctive patterns of sexual risk taking both cross-sectionally and longitudinally: that selection into specific types of sexual relationships partially mediates these effects; and that these needs may be differentially expressed, or even suppressed, depending on relationship context. Results provide strong support for the functionalist perspective on behavior and indicate that an adequate understanding of sexual risk-taking behavior must take into account the various needs and goals that such behavior can serve.

Motivations for sex and risky sexual behavior among adolescents and young adults: a functional perspective

The implications of a functionalist perspective for understanding sexual risk taking are explored. Key motivational dimensions thought to underlie human behavior (viz., approach vs. avoidance, autonomy vs. relatedness) were used to identify 4 broad domains of sexual motivations and to develop a measure of specific motives within each of these domains. Data from both college student and community samples are used to demonstrate the psychometric adequacy of these scales and to show that having sex for different reasons predicts distinctive patterns of sexual risk taking both cross-sectionally and longitudinally: that selection into specific types of sexual relationships partially mediates these effects; and that these needs may be differentially expressed, or even suppressed, depending on relationship context. Results provide strong support for the functionalist perspective on behavior and indicate that an adequate understanding of sexual risk-taking behavior must take into account the various needs and goals that such behavior can serve.

Repeated emergence of epidemic/epizootic Venezuelan equine encephalitis from a single genotype of enzootic subtype ID virus

Venezuelan equine encephalitis (VEE) epidemics and equine epizootics occurred periodically in the Americas from the 1920s until the early 1970s, when the causative viruses, subtypes IAB and IC, were postulated to have become extinct. Recent outbreaks in Columbia and Venezuela have renewed interest in the source of epidemic/epizootic viruses and their mechanism of interepizootic maintenance. We performed phylogenetic analyses of VEE virus isolates spanning the entire temporal and geographic range of strains available, using 857-nucleotide reverse transcription-PCR products including the E3 and E2 genes. Analyses indicated that epidemic/epizootic viruses are closely related to four distinct, enzootic subtype ID-like lineages. One of these lineages, which occurs in Columbia, Peru, and Venezuela, also included all of the epidemic/epizootic isolates; the remaining three ID-like lineages, which occur in Panama, Peru, Florida, coastal Ecuador, and southwestern Columbia, were apparently not associated with epizootic VEE emergence. Within the Columbia/Peru/Venezuela lineage, three distinct monophyletic groups of epidemic/epizootic viruses were delineated, indicating that VEE emergence has occurred independently at least three times (convergent evolution). Representative, complete E2 amino acid sequences were compared to identify potential determinants of equine virulence and epizootic emergence. Amino acids implicated previously in laboratory mouse attenuation generally did not vary among the natural isolates that we examined, indicating that they probably are not involved in equine virulence changes associated with VEE emergence. Most informative amino acids correlated with phylogenetic relationships rather than phenotypic characteristics, suggesting that VEE emergence has resulted from several distinct combinations of mutations that generate viruses with similar antigenic and equine virulence phenotypes.

Detection of expressed chloramphenicol acetyltransferase in the saliva of Culex pipiens mosquitoes

Mosquito salivary glands play an important role in the transmission of arthropod-borne pathogens. The ability to express genes in mosquitoes would be a powerful approach to characterize salivary gland genes, and to reveal important vector determinants of pathogen transmission. Here we report the use of a double subgenomic Sindbis (dsSIN) virus, designated TE/3'2J/CAT, and a packaged Sindbis replicon virus, designated rep5/CAT/26S, to express chloramphenicol acetyltransferase (CAT) protein in the salivary glands and saliva of transduced female Culex pipiens pipiens. Indirect immunofluorescence analysis revealed that salivary glands of these mosquitoes infected with either TE/3'2J/CAT or rep5/CAT/26S virus (4 or 6 days post-infection (p.i.)) were positive for both SIN E1 antigen and CAT protein. Saliva collected from mosquitoes transduced with TE/3'2J/CAT virus contained a unique 25 kDa protein that corresponded to the size of CAT protein. Additionally, CAT activity assays revealed that saliva collected from mosquitoes transduced with either TE/3'2J/CAT or rep5/CAT/26S virus could contain greater than 5.0 x 10(-5) units of CAT enzyme (3.0 x 10(6) CAT trimers).

Genetically engineered resistance to dengue-2 virus transmission in mosquitoes

The control of arthropod-borne virus diseases such as dengue may ultimately require the genetic manipulation of mosquito vectors to disrupt virus transmission to human populations. To reduce the ability of mosquitoes to transmit dengue viruses, a recombinant Sindbis virus was used to transduce female Aedes aegypti with a 567-base antisense RNA targeted to the premembrane coding region of dengue type 2 (DEN-2) virus. The transduced mosquitoes were unable to support replication of DEN-2 virus in their salivary glands and therefore were not able to transmit the virus.

Molecularly engineered resistance to California serogroup virus replication in mosquito cells and mosquitoes

Introduction of genetic elements derived from a viral pathogen's genome may be used to reduce the vectorial capacity of mosquitoes for that virus. A double subgenomic Sindbis virus expression system was utilized to transcribe sequences of LaCrosse (LAC) virus small (S) or medium (M) segment RNA in sense or antisense orientation; wild-type Sindbis and LaCrosse viruses have single-stranded RNA genomes, the former being positive sense and the latter being negative sense. Recombinant viruses were generated and used to infect Aedes albopictus (C6/36) mosquito cells, which were challenged with wild-type LAC virus and then assayed for LAC virus replication. Several recombinant viruses containing portions of the LAC S segment were capable of inducing varying degrees of interference to the challenge virus. Cells infected with TE/3'2J/ANTI-S virus, expressing full-length negative-sense S RNA of LAC virus, yielded 3-6 log10TCID50 (tissue culture 50% infective dose) less LAC virus per ml than did cells infected with a double subgenomic sindbis virus containing no LAC insert. When C6/36 cells infected with TE/3'2J/ANTI-S were challenged with closely related heterologous bunyaviruses, a similar inhibitory effect was seen. Adult Ae. triseriatus mosquitoes infected with TE/3'2J/ANTI-S were also resistant to challenge by LAC virus. Organs that were productively infected by the double subgenomic Sindbis virus expressing the LAC anti-S sequences demonstrated little LAC virus or antigen. These studies indicate that expression of carefully selected antiviral sequences derived from the pathogen's genome may result in efficacious molecular viral interference in mosquito cells and, more importantly, in mosquitoes.

Pathogen-derived resistance to dengue type 2 virus in mosquito cells by expression of the premembrane coding region of the viral genome

The full-length premembrane (prM) coding region of the dengue virus type 2 (DEN-2; Jamaica) genome was expressed in C6/36 (Aedes albopictus) cells in either the sense or the antisense orientation from a double subgenomic Sindbis (dsSIN) virus. Northern (RNA) blot analysis confirmed the expression of sense or antisense DEN-2 prM RNA in infected C6/36 cells. PrM protein was demonstrated in cells infected with dsSIN virus expressing DEN-2 sense RNAs by an immunofluorescence assay. C6/36 cells were infected with each dsSIN virus at a multiplicity of infection (MOI) of 50 and challenged 48 h later with DEN-2 virus at an MOI of 0.1. Whereas C6/36 cells infected with a control of dsSIN virus supported high levels of DEN-2 replication, C6/36 cells infected with the dsSIN virus expressing prM antisense RNA were completely resistant to DEN-2 challenge. Cells expressing prM protein or untranslatable prM sense RNA also were resistant to DEN-2 challenge. Cells expressing prM protein demonstrated some breakthrough of DEN-2 virus when challenged at an MOI of 10. However, expressed untranslatable sense prM RNA conferred complete protection to challenge at the high MOI.

Replication and expression of a recombinant Sindbis virus in mosquitoes

A recombinant Sindbis virus, TE/3'2J/ANTI-S, containing LaCrosse virus small segment cDNA in antisense orientation, was inoculated into Aedes triseriatus mosquitoes. Virus replication and LAC-ANTI-S RNA expression were analysed temporally and spatially. TE/3'2J/ANTI-S virus titre peaked at 5.0 log10 TCID50 in heads 6-9 days post infection (p.i.) and decreased to 3.4 log10 TCID50 by 37 days p.i. Salivary glands contained 4.4 log10 TCID50 of virus 6 days p.i.; titres were lower in other organs. LAC-ANTI-S RNA levels paralleled virus titre. SIN E1 antigen was detected in many mosquito organ systems, but in specific cells and tissues of some organs. TE/3'2J/ANTI-S virus exhibited different cellular tropisms in salivary glands of Aedes and Culex mosquitoes.

The expression of chloramphenicol acetyltransferase in mosquitoes and mosquito cells using a packaged Sindbis replicon system

Sindbis (SIN) replicon virus was used to express chloramphenicol acetyltransferase (CAT) in Aedes albopictus (C6/36) cells and Aedes triseriatus mosquitoes. RNA transcribed in vitro from a SIN replicon plasmid (pSINrep5/CAT) and from SIN virus helper constructs (pDH-EB or pDH(26S)5'SIN) was coelectroporated into BHK-21 cells to generate replicon viruses, designated rep5/CAT/EB and rep5/CAT/26S. C6/36 cells infected with rep5/CAT/EB or rep5/CAT/26S virus at a multiplicity of infection of 3, expressed 3.8 x 10(6) and 6.0 x 10(6) CAT trimers per cell, respectively, at 2 days postinfection (pi). Both viruses attained peak titers by Day 2 pi. Adult female A. triseriatus mosquitoes were intrathoracically inoculated with 7 x 10(4) IFU rep5/CAT/EB or 1 x 10(5) IFU rep5/CAT/26S virus. Virus titers remained at approximately 10(5) IFU/ml through Day 2 pi and decreased roughly 1 log by Day 10 pi. CAT enzyme activity was detected 2 days pi (rep5/CAT/EB, 1.49 x 10(-4) units CAT/10 micrograms protein; rep5/CAT/26S, 2.03 x 10(-5) units CAT/10 micrograms protein) and remained near these levels through Day 10 pi. CAT was detected in the head, salivary glands, midgut, and ovaries of inoculated mosquitoes by indirect immunofluorescence or CAT activity assays. These results suggest that packaged replicon viruses can be useful for expression of heterologous genes in mosquito cells and whole mosquitoes.

Mosquito sensitivity to a scorpion neurotoxin expressed using an infectious Sindbis virus vector

The scorpion, Androctonus australis Hector, produces an insect-specific toxin (AaHIT) encoded by the Scotox gene. To assess the toxicity of AaHIT for mosquitoes, we have taken a novel approach to express the Scotox gene in vivo. We have engineered a double subgenomic Sindbis (dsSIN) virus that contains the Scotox gene in the viral genome and intrathoracically inoculated the virus (TE/3'2J/Scotox) into mosquitoes (Aedes aegypti, Ae. triseriatus and Culex pipiens), houseflies (Musca domestica) and ticks (Dermacentor andersoni). Mosquitoes, which normally show no pathologic effects from Sindbis (SIN) virus infections, died 1-5 days after infection with TE/3'2J/Scotox virus. Neither flies nor ticks were killed. The mosquitocidal action of AaHIT in mosquitoes makes AaHIT a potential candidate for inclusion in molecular-based methods of mosquito control. The expression of an arthropod gene in vivo demonstrates the utility of dsSIN expression vectors for future use to examine and potentially disrupt endogenous gene functions in mosquitoes.

Intracellular immunization of mosquito cells to LaCrosse virus using a recombinant Sindbis virus vector

A cDNA of the small RNA genome segment of La Crosse (LAC) virus was inserted, in an antisense orientation, into a double subgenomic Sindbis (dsSIN) virus expression vector generating pTE/3'2J/ANTI-S (15,000bp). In vitro transcription of the pTE/3'2J/ANTI-S template generated genomic RNA that was electrotransfected into BHK-21 cells to produce virus. Northern blot analysis of RNA isolated from infected Aedes albopictus (C6/36) cells showed that the TE/3'2J/ANTI-S virus produced a subgenomic mRNA of the appropriate size, indicating transcription of the LAC cDNA segment. C6/36 cells were infected with either TE/3'2J/ANTI-S, TE/3'2J (a dsSIN virus with no LAC insert), or wild type Sindbis (SIN, strain AR339) viruses and subsequently challenged with LAC virus. LAC virus titers were determined using a capture antibody ELISA. Mosquito cells infected with TE/3'2J/ANTI-S virus yielded at least 4 log10 TCID50/ml less LAC virus than cells infected with either TE/3'2J or AR339 SIN viruses. The use of the infectious SIN virus expression vectors provides a novel approach for high level cytoplasmic expression of genes or sequences of interest in arthropod cells, and for evaluating strategies for intracellular immunization against arboviruses.

Alphavirus expression systems: Applications to mosquito vector studies

In this review, Steve Higgs, Ann Powers and Ken Olson describe how alphavirus expression systems, based on infectious cDNA clones of Sindbis virus, constitute a novel RNA virus delivery system suitable for the efficient expression of heterologous gene products or RNA sequences in mosquito cells or adult mosquitoes. The technique permits ready assessment of molecular genetic-based methods of intracellular interference to infection and provides a powerful new tool for molecular biological studies in arthropods.

DRGs: optional in Maryland's GIR system

Maryland hospitals prefer the guaranteed inpatient revenue system to the DRG method of case mix reimbursement for its flexibility of administration and ease of use in refining case groups.