G.R. Carner

Simian Rotaviruses Possess Divergent Gene Constellations That Originated from Interspecies Transmission and Reassortment

ABSTRACT Although few simian rotaviruses (RVs) have been isolated, such strains have been important for basic research and vaccine development. To explore the origins of simian RVs, the complete genome sequences of strains PTRV (G8P[1]), RRV (G3P[3]), and TUCH (G3P[24]) were determined. These data allowed the genotype constellations of each virus to be determined and the phylogenetic relationships of the simian strains with each other and with nonsimian RVs to be elucidated. The results indicate that PTRV was likely transmitted from a bovine or other ruminant into pig-tailed macaques (its host of origin), since its genes have genotypes and encode outer-capsid proteins similar to those of bovine RVs. In contrast, most of the genes of rhesus-macaque strains, RRV and TUCH, have genotypes more typical of canine-feline RVs. However, the sequences of the canine and/or feline (canine/feline)-like genes of RRV and TUCH are only distantly related to those of modern canine/feline RVs, indicating that any potential transmission of a progenitor of these viruses from a canine/feline host to a simian host was not recent. The remaining genes of RRV and TUCH appear to have originated through reassortment with bovine, human, or other RV strains. Finally, comparison of PTRV, RRV, and TUCH genes with those of the vervet-monkey RV SA11-H96 (G3P[2]) indicates that SA11-H96 shares little genetic similarity to other simian strains and likely has evolved independently. Collectively, our data indicate that simian RVs are of diverse ancestry with genome constellations that originated largely by interspecies transmission and reassortment with nonhuman animal RVs.

A description of the life cycle of Entomophthora sp. in the two-spotted spider mite☆

Abstract Entomophthora sp. killed its host, Tetranychus urticae , in 3.38 days at 25°C and in 11.02 days at 15°C. Development of hyphal bodies within the mite was studied with a light microscope, and a scanning electron microscope was used to examine spore development and structure. A comparison of this fungus with other mite-infecting fungi revealed that it is more closely related to E. floridana than to E. tetranychi , and should be called Entomophthora sp. near floridana until a more detailed study of E. floridana can be made.

Histopathology of virus-like particles in Heliothis spp☆

Abstract Larvae of Heliothis spp. collected from cotton, soybean, and peanut fields in South Carolina were found to be infected with virus-like particles (VLPs). Infected larvae became pale and swollen, stopped feeding, and remained alive for 2–3 weeks. Hemolymph from these larvae was milky and contained numerous spherical bodies ranging in diameter from 2 to 10 μm. The hemolymph also contained VLPs which were oval and measured 375 × 125 nm. Infectivity tests with crude saline extracts of infected larvae demonstrated that the pathogen could be transmitted by injection but not per os. The spherical bodies contained VLPs (387 × 149 nm) surrounded by two envelopes and packed together in clusters. These VLPs were also found in fat body cells, cuticular epithelial cells, tracheal cells, and connective tissue associated with the body wall and the gut. They were not found in muscle tissue or in midgut epithelial cells. Similar VLPs have been found in Heliothis zea from Mississippi and Trichoplusia ni from California, but a positive identification of the VLPs has not been made in any of these studies. Morphologically they appear to be distinct from any other previously described insect viruses.

The infectivity of a nuclear polyhedrosis virus of the velvetbean caterpillar for eight noctuid hosts

Abstract Eight species of noctuid larvae were tested for susceptibility to a nuclear polyhedrosis virus of the velvetbean caterpillar, Anticarsia gemmatalis. Velvetbean caterpillar larvae were highly susceptible to crude preparations of polyhedral inclusion bodies (PIBs; LD50 = 4.7 PIBs/larva), but preparations of purified polyhedra were much less effective against these larvae (LD50 = 319.7 PIBs/larva). Of seven other noctuid species tested, only Heliothis virescens was as susceptible to the virus as A. gemmatalis. High dosages were required to kill Heliothis zea, Trichoplusia ni, Pseudoplusia includens, and Spodoptera ornithogalli. Plathypena scabra and Spodoptera frugiperda were not susceptible.

Factors affecting the spore form of Entomophthora gammae

Factors suspected of influencing the type of spores (conidia or resting spores) formed by Entomophthora gammae in its host Pseudoplusia includens were investigated. As epizootics of E. gammae progressed in field populations, high numbers of the conidial form gave way to high numbers of the resting spore form. Ratios of conidia to resting spores were not significantly altered when infected larvae were exposed to shortened photoperiods or to cooler temperatures. Age or size of infected larvae appeared to influence spore development; conidia were the predominant spore form in small larvae ( 2.5 cm).

Infectivity of an iridescent virus for larvae of Anticarsia gemmatalis (Lepidoptera: Noctuidae)

Abstract Laboratory tests were conducted with an iridescent virus (IV) of Anticarsia gemmatalis from Argentina to determine its infectivity for all six larval instars. For first, second, and third instars, the LC50 values were 5.93, 6.14, and 11.30 mg/ml, respectively. The LD50 values for fourth, fifth, and sixth instars were 1.21, 3.12, and 1.31μg/mg, respectively. The time until death was greater for early instars than for late instars; first instars averaged 23.1 days, second instars 19.6 days, third instars 19.5 days, fourth instars 14.3 days, fifth instars 8.2 days and sixth instars 6.5 days until death. High levels of iridescent virus inoculum appeared to activate a latent nuclear polyhedrosis virus in an average of less than 10% of larvae succumbing to a viral infection. Variable mortality rates were caused with low levels of IV inoculum; high dosages produced a high percentage of mortality, but it was virtually impossible to raise levels of inoculum to concentrations sufficient to produce 100% mortality.

Entomophthora lampyridarum, a fungal pathogen of the soldier beetle, Chauliognathus pennsylvanicus

Abstract In 1974 and 1979 in Clemson, South Carolina, adults of the common soldier beetle, Chauliognathus pennsylvanicus , were found to be infected by the fungal pathogen, Entomophthora lampyridarum . After infected beetles died they remained attached by their mandibles to foliage and flowers. The wings of infected beetles remained open, allowing conidiophores to develop on the upper surface of the abdomen. Primary conidia were elongate and measured 36.5 × 17.1 μm. Two types of secondary spores were formed: Type I spores were similar in form to primary conidia, but were somewhat smaller; Type II spores were formed at the apex of slender stalks and measured 37.7 × 15.3 μm. Resting spores were spherical, hyaline, and 22.3 μm in diameter.

Ultrastructure of fat body cells of the velvetbean caterpillar infected with a nuclear polyhedrosis virus

Abstract During a study of the ultrastructure of a nuclear polyhedrosis virus of the velvetbean caterpillar, Anticarsia gemmatalis, various types of nuclear and cytoplasmic inclusions were found in fat body tissue heavily infected with the virus. Virogenic stroma was present in the nuclei of most infected cells. Bundles of fibrous material were observed in the nuclei and cytoplasm of cells containing polyhedral bodies. Other nuclear inclusions included concentric multilayered material, vacuoles, and membrane structures.