The isolation of Kemerovo group orbiviruses and Uukuniemi group viruses of the family bunyaviridae from Ixodes uriae ticks from the Isle of May, Scotland.

Viruses isolated from ticks (Ixodes uriae) from a seabird colony on the Isle of May, Scotland, were shown by complement fixation tests to be related to the Uukuniemi and Kemerovo serogroups. Electron microscopic studies on the Uukuniemi viruses showed them to have a morphology characteristic of the bunyaviridae, and the Kemerovo group to be characteristic of orbiviruses. Separate isolates from the two serogroups were distinguished from each other by neutralization tests.

Mixed infections with tick-borne viruses in a seabird colony in Eire.

Viruses were isolated from 2 tick species collected from the nesting areas of seabirds on Great Saltee Island, Eire. Bunyaviruses of the Uukuniemi serogroup were isolated from hard ticks (Ixodes uriae and I. rothschildi), bunyaviruses of the Hughes serogroup from soft ticks (Ornithodoros maritimus), and orbiviruses of the Kemerovo serogroup from I. uriae and O. maritimus. The results indicate that the bunyaviruses, but not the orbiviruses, show "tick specificity". Neutralising activity against members of all 3 serogroups was detected in sera from chicks in the nesting areas; neutralising antibodies were probably maternal.

Structure of the Baculovirus nucleocapsid.

A low-resolution structural model of the nucleocapsid of Spodoptera litura granulosis virus, a member of the Baculoviridae family, has been determined using contrast variation methods in both electron microscopy and low-angle X-ray solution scattering. The cylindrical portion of the characteristic capsid surface is composed of a 12 start helix system of monomer subunits, giving rise to a relatively open stacked ring structure running parallel to the cylinder axis and repeating approximately every third ring. Structural proteins which appear distinct from those constituting the cylinder comprise the stacked ring-like assemblies which form caps at both ends of the nucleocapsid. Within the nucleocapsid the double-stranded closed loop of DNA associates heterogeneously with a highly basic polypeptide to form a cylindrical core. The basic protein is thought to participate in condensation and protection of the genome both prior to and during encapsidation.

Assessment of the human and ecological hazards of microbial insecticides.

A comprehensive account is given of the evolution of registration guidelines and safety testing procedures for microbial insecticidal agents. Particular emphasis is given to the use of viruses for pest control and the various guidelines developed to assess their possible hazards. The likely gains and risks associated with using viruses are discussed. Several meetings have been held in the last 10 years to assess the hazards of virus insecticides. Some of these meetings have produced recommendations, some have developed guidelines for safety testing. These meetings are reviewed. The various guidelines developed for safety testing are critically evaluated and the UK Registration Criteria for Biological Agents used as Pesticides are reproduced in full. Examples of viruses that have been safety tested and registered for use are given and the criteria used are described. Conclusions are drawn on the merits of the guidelines presently available and the likely future development of safety testing schemes is considered.

Isolation of a coronavirus during studies on puffinosis, a disease of the Manx shearwater (Puffinus puffinus).

A virus was isolated from 2 day-old mice inoculated with homogenates of either the lungs or blood of 2 different shearwaters affected by puffinosis. Examination of infected suckling mouse brain and infected NCTC-1469 (mouse liver) cell cultures, by electron microscopy, revealed virus particles and inclusion bodies characteristic of a coronavirus. Neutralization, complement fixation and fluorescent antibody tests showed that the virus was related to mouse hepatitis virus. The virus was not isolated from 445 control, uninfected mice. Neutralising antibodies were not detected in 39 sera from diseased shearwaters and 2 sera from apparently healthy birds. Two shearwaters inoculated with the virus did not develop clinical signs of infection. The question of whether the virus was isolated from shearwaters or from laboratory mice is discussed.

Orbiviruses and bunyaviruses from a seabird colony in Scotland.

Viruses isolated from ticks (Ixodes uriae) and a kittiwake (Rissa tridactyla) from a seabird colony at St. Abb's Head, Scotland, were shown by complement fixation tests (CFT) to be antigenically related to the Uukuniemi and Kemerovo serogroups. Electron microscopic examination of cell cultures infected with the Kemerovo group viruses revealed particles characteristic of orbiviruses, 72 +/- 3 nm in diam., with an inner core 37 +/- 3 nm in diam., in association with intracytoplasmic, densely staining granular areas, and with fibrillar and tubular structures. Cell cultures infected with the Uukuniemi group viruses revealed characteristic bunyavirus particles, 94 +/- 7 nm in diam., with a closely adherent envelope. Both orbi- and bunyaviruses were isolated from two tick pools and the kittiwake. A third tick pool contained an orbivirus which cross-reacted with the other isolates in CFT and fluorescent antibody tests, but was distinguished from them by neutralization tests.

Induction of a nonoccluded baculovirus persistently infecting Heliothis zea cells by Heliothis armigera and Trichoplusia ni nuclear polyhedrosis viruses.

A nonoccluded singly enveloped baculovirus (baculovirus X) persistently infects Heliothis zea (IMC-HZ-1) cells in culture. Singly enveloped nuclear polyhedrosis viruses from H. zea and Heliothis armigera, and multiply enveloped nuclear polyhedrosis viruses from Trichoplusia ni, Spodoptera frugiperda, and Spodoptera littoralis were all found to induce baculovirus X. Experiments are reported which use metabolic inhibitors and inactivated inducing virus to show that it is probable that a structural component of the virus, most likely a protein, is responsible for inducing baculovirus X. The persistent virus is induced to replicate by uv-inactivated virus but not by heat-inactivated inducing virus. The virus is not induced to replicate by a number of metabolic inhibitors in the absence of an inducing virus. Inhibition of transcription and translation prevents the induction of the persistent virus by an inducing virus. Inhibition of DNA replication has no effect on the induction of the virus. This suggests that the persistent virus genome is present in abundance in all cells.

The replication and titration of iridescent virus type 22 in Spodoptera frugiperda cells.

A plaque assay for iridescent virus type 22 (from Simulium sp.) using Spodoptera frugiperda cells has been devised, and the kinetics of growth of the virus in this cell line have been determined. The virus particle/p.f.u. ratio was 75 +/- 8, and the p.f.u./TCID50 ratio was 0.56 +/- 0.11.

The structural polypeptides of sowthistle yellow vein virus (SYVV).

The four structural polypeptides of SYYV have molecular weights of 71,000, 60,000, 42,000 and 36,000 daltons. The virus was shown colorimetrically to contain RNA.

Replication of nuclear polyhedrosis virus in a continuous cell culture of Spodoptera frugiperda: microscopy study of the sequence of events of the virus infection.

A microscopy study of the sequence of morphogenic events of Spodoptera frugiperda nuclear polyhedrosis virus infection of S. frugiperda cells is presented which orders the sequence of replication and establishes the time scale within which the events occur. The virus entered the cell by 1 h postinfection and was uncoated. The eclipse period was 9 h and the latent period was 12 h. Polyhedron formation was detected by 18 h postinfection and continued until the deposition of the polyhedron membrane was completed by 48 h postinfection. Aberrant morphogenic characteristics of virus repeatedly passaged in the cell culture were also recorded. Adsorption, envelope morphogenesis, and release mechanisms are discussed in light of other data on in vivo and in vitro baculovirus infections.