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PubMed1993

[Yellow fever virus, dengue 2 and other arboviruses isolated from mosquitos, in Burkina Faso, from 1983 to 1986. Entomological and epidemiological considerations].

An arbovirus surveillance was carried out in Burkina Faso from 1983 to 1986. It was based on crepuscular catches of mosquitoes on human bait in some wooded areas and in one town. The total collection was 228 catches with an average of 8 men per catch. The total number of mosquitoes caught was 44,956 among which 32,010 potential vector of yellow fever; all these mosquitoes were analysed for arbovirology. In the south-western part of the country (region of Bobo-Dioulasso), surveillance was conducted each year from August to November, whilst the circulation of Aedes-borne arboviruses is well known to be favoured. In 1983, 1984 and 1986, seven strains of yellow fever virus were isolated in circumstances remarkably similar. They came from selvatic areas and never from the town. They concerned only Aedes (Stegomyia) luteocephalus which is the very predominant potential vector of yellow fever in the region. They were obtained in low figure, between 1 and 4 per year. They occurred from 27th of October to 21th of November. These observations confirm that the southern portion of the Sudan savanna zone of West Africa is the setting of a customary circulation of yellow fever virus and therefore belongs to the endemic emergence zone. In 1986, two strains of dengue 2 virus were isolated. One concerned Ae. luteocephalus from the selvatic area, the other Ae. (St.) aegypti from the heart of town. These data suggest two distinct cycles for dengue 2 virus, one urban and one selvatic, which could coexist simultaneously in the same region. In the south-eastern part of the country (region of Fada-N'Gourma) a yellow fever epidemic occurred between September and December 1983; its study has enable to precise their entomological aspects. The entomological inoculation rate of yellow fever virus has been evaluated to 22 infected bites per man during the month of october, for a man living close to forest gallery. 25 strains of yellow fever virus strains was isolated from Ae. (Diceromyia) furcifer which is the potential vector the most abundant in this region: the main role of this species in an epidemic was confirmed. An investigation in September 1984 had not permitted isolation of the virus therefore it is suspected that the large epizootic circulation of virus in 1983 has not been renewed the year after. In total 59 viral strains belonging to 10 different viruses were isolated from 9 species of mosquitoes.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1982

The double-stranded RNA genome segments of cytoplasmic polyhedrosis virus are independently transcribed.

The in vitro transcription of the genome segments of insect cytoplasmic polyhedrosis virus was examined for a possible mechanism of coordinate control. Initiation of the first transcription cycle, primed by preincubation in the absence of CTP, was synchronous for all 10 viral genome segments. The time required for the completion of each genome transcript was proportional to the chain length, and all 10 mRNA's were synthesized in molar amounts inversely proportional to their molecular weights. The rate of chain elongation for all mRNA's was approximately 6 nucleotides per s. The combined results indicate that each of the viral genome segments is transcribed independently and suggest that RNA chain elongation, not initiation, is rate limiting for cytoplasmic polyhedrosis virus mRNA synthesis in vitro.

Animals↗
PubMed1994

Characterization of Newcastle disease virus envelope glycoproteins expressed in insect cells.

Recombinant baculoviruses carrying cDNAs of hemagglutinin-neuraminidase (HN) and fusion (F) glycoprotein genes of virulent and avirulent strains of Newcastle disease virus (NDV) were constructed to examine the contribution of the individual proteins in cell fusion. F proteins of both virulent and avirulent strains expressed by the recombinant viruses were glycosylated and translocated onto the cell surfaces and only the F protein of the virulent origin was proteolytically cleaved into F1 and F2 subunits and bound intermolecularly by disulfide bonds. HN proteins of virulent and avirulent strains expressed by the recombinant viruses showed both hemadsorption and neuraminidase activities. Single infection of the recombinant baculoviruses could not induce cell fusion; however, co-infection with the recombinant viruses of the F protein of virulent strain and HN protein of both strains gave clear syncytia in insect cells. The syncytium formation was much clearer in the cells co-infected with the recombinants of F protein of virulent strain and the HN protein of avirulent strain in comparison with those co-infected with F and HN recombinant viruses of virulent origin. The cell fusion was completely blocked by monoclonal antibodies against the F protein but not by those to the HN protein.

Animals↗
PubMed1976

Determination of the mass of viruses by quantitative electron microscopy.

The photometric method of quantitative determination of dry mass by electron microscopy has been applied to the study of various types of viruses: animal, plant, insect, and bacterial. The method is applicable to all viruses having a mass of 1 x 10-18g or greater. The molecular weight of viruses can be calculated from the mass value by multiplying it by Avogadro's number. In comparison to other methods of determining the molecular weight of viruses, sedimentation and diffusion, sedimentation equilibrium, light scattering, and electron microscopy counting, the method of quantitative electron microscopy is competitive. In some ways quantitative electron microscopy is superior to other methods for the determination of molecular weight: There is no limitation to the size of the virus, no experimental time involved and no concentration and purity of virus preparations required, and finally it is independent of the geometry of the virion. In one important aspect it is unique when compared to other methods; namely, it affords one the capacity to analyse individual virus particles.

Biophysical Phenomena↗
PubMed1973

Characterization of nuclear polyhedrosis virus DNAs.

The nuclear polyhedrosis virus DNAs characterized and compared in this study consist of the singly-enveloped nucleocapsids (SNPV) of Trichoplusia ni and the bundles of nucleocapsids common to a single envelope (MNPV) from Spodoptera frugiperda and Rachiplusia ou. The SNPV and MNPV DNAs are very similar in hydrodynamic properties and molecular weights. In addition, the NPV DNAs are similar in size to those extracted from the granulosis viruses that infect T. ni and S. frugiperda. As isolated from purified virus or directly from occluded virus, the nuclear polyhedrosis virus DNAs consist of a mixture of about 20 to 30% double-stranded covalently closed molecules and approximately 60% relaxed circles, with less than 10% in linear duplex form. The molecular weights of all nuclear polyhedrosis virus DNAs as compared in this study are slightly smaller than those of T4 bacteriophage DNA and perhaps slightly smaller than those of the granulosis virus DNAs. The best estimates of these molecular weights by neutral sucrose sedimentation for the nuclear polyhedrosis viruses range from 90 to 100 x 10(6) relative to a size of 108 x 10(6) for T4 DNA. The base compositions of the nuclear polyhedrosis viruses that infect T. ni and S. frugiperda are compared with the respective insect host DNAs.

Centrifugation, Density Gradient↗
PubMedDate not supplied

Direct methods for detecting picorna-like virus from dead and alive triatomine insects.

In this work we report four different destructive and non-destructive methods for detecting picorna-like virus particles in triatomines. The methods are based on direct observation under transmission electron microscope and they consist of four ways to prepare samples of presumable infected material. The samples are prepared processing dead or alive insect parts, or even dry or fresh insect feces. The methods can be used as analytical or preparative techniques, for quantifying virus infection and checking virus integrity as well. In this work the four methods are applied in order to detect Triatoma virus (TrV) particles in T. infestans colonies.

Animals↗
PubMed1996

Purified JC virus T antigen derived from insect cells preferentially interacts with binding site II of the viral core origin under replication conditions.

The human polyomavirus JC virus (JCV) establishes persistent, asymptomatic infections in most individuals, but in severely immunocompromised hosts it may cause the fatal demyelinating brain disease progressive multifocal leukoencephalopathy. In cell culture JCV multiplies inefficiently and exhibits a narrow host range. This restricted behavior occurs, in part, at the level of DNA replication, which is regulated by JCV's multifunctional large tumor protein (TAg). To prepare purified JCV TAg (JCT) for biochemical analyses, the recombinant baculovirus B-JCT was generated by cotransfection of insect cells with wild-type baculovirus and the vector pVL-JCT(Int-) containing the JCT-coding sequence downstream of the efficient polyhedrin promoter. JCT expressed in infected cells was immunoaffinity purified using the anti-JCT monoclonal antibody PAb 2000. Characterization of the viral oncoprotein indicated that it exists in solution as a mixture of monomeric and oligomeric species. With the addition of ATP, the population of monomers decreased and that of hexamers and double hexamers increased. A DNA mobility shift assay indicated that origin binding occurred primarily with the double-hexamer form. A comparison of the specific DNA-binding activities of JCT and SV40 TAg (SVT) revealed that JCT generally exhibited greater affinity for binding site II relative to binding site I (B.S. I) of both viral origin regions, whereas SVT preferentially bound B.S. I. Furthermore, JCT bound nonviral DNA more efficiently than did SVT. These functional differences between the two TAgs may contribute to the reduced DNA replication potential of JCV in vitro, and to the virus' ability to establish persistent infections in vivo.

Animals↗