Nonoccluded Virus Research Articles

Small nonoccluded virus

This datasheet on small nonoccluded virus covers Identity, Distribution.

RNA interference-based antiviral immune response against the salivary gland hypertrophy virus in Glossina pallidipes

BackgroundGlossina pallidipes salivary gland hypertrophy virus (GpSGHV; Hytrosaviridae) is a non-occluded dsDNA virus that specifically infects the adult stages of the hematophagous tsetse flies (Glossina species, Diptera: Glossinidae). GpSGHV infections are usually asymptomatic, but unknown factors can result to a switch to acute symptomatic infection, which is characterized by the salivary gland hypertrophy (SGH) syndrome associated with decreased fecundity that can ultimately lead to a colony collapse. It is uncertain how GpSGHV is maintained amongst Glossina spp. populations but RNA interference (RNAi) machinery, a conserved antiviral defense in insects, is hypothesized to be amongst the host’s mechanisms to maintain the GpSGHV in asymptomatic (persistent or latent) infection state. Here, we investigated the involvement of RNAi during GpSGHV infections by comparing the expression of three key RNAi machinery genes, Dicer (DCR), Argonaute (AGO) and Drosha, in artificially virus injected, asymptomatic and symptomatic infected G. pallidipes flies compared to PBS injected (controls) individuals. We further assessed the impact of AGO2 knockdown on virus infection by RT-qPCR quantification of four selected GpSGHV genes, i.e. odv-e66, dnapol, maltodextrin glycosyltransferase (a tegument gene) and SGHV091 (a capsid gene).ResultsWe show that in response to hemocoelic injections of GpSGHV into G. pallidipes flies, increased virus replication was accompanied by significant upregulation of the expression of three RNAi key genes; AGO1, AGO2 and DCR2, and a moderate increase in the expression of Drosha post injection compared to the PBS-injected controls. Furthermore, compared to asymptomatically infected individuals, symptomatic flies showed significant downregulation of AGO1, AGO2 and Drosha, but a moderate increase in the expression of DCR2. Compared to the controls, knockdown of AGO2 did not have a significant impact on virus infection in the flies as evidenced by unaltered transcript levels of the selected GpSGHV genes.ConclusionThe upregulation of the expression of the RNAi genes implicate involvement of this machinery in controlling GpSGHV infections and the establishment of symptomatic GpSGHV infections in Glossina. These findings provide a strategic foundation to understand GpSGHV infections and to control latent (asymptomatic) infections in Glossina spp. and thereby control SGHVs in insect production facilities.

Preliminary search for a νirus in Dacus oleae Gmel. populations in Northern Greece

A large number of larvae of Dacus oleae were collected from infested olives in Northern Greece, and a small proportion of these were found to be dead. Adult flies were caught in McPhail traps at the same locations. The larvae and adults were fractionated by a series of steps designed to identify occluded and nonoccluded viruses. Virus-like particles were identified in small amounts only in the dead larvae.

Cytopathology of Bombyx mori (Lepidoptera: Bombycidae) silk gland caused by multiple nucleopolyhedrovirus

A multiple nucleopolyhedrovirus previously isolated from infected Bombyx mori L. larvae (BmMNPV) in Paraná state, Brazil, was inoculated into B. mori larvae to examine susceptibility and cytopathology in silk gland cells. The anterior, middle and posterior silk glands were removed from the infected silkworm at different times post-inoculation and processed for cytopathology studies by light and transmission electron microscopy. BmMNPV infection was only detected at 72 h post-inoculation in cells of the middle and posterior silk glands. No sign of infection was found in the anterior silk gland. Cytopathological characteristics were similar to those found in other target tissues; initially, they consisted of nuclear hypertrophy and the formation of virogenic stroma (viroplasm), in which the progeny virions are produced. The virions are then enveloped and occluded in protein crystal structures, the polyhedra. After viral replication, cells undergo lysis and release a great number of BmMNPV polyhedra into the hemocoele. Histopathology showed early infection foci in regions surrounding trachea insertions, demonstrating that trachea is an infection-spreading organ in the insect body. Trachea penetrates the middle and posterior silk gland basal lamina, considered a barrier to virus, facilitating the penetration of budded virus. The anterior silk gland does not have tracheal insertions into the basal lamina, which reduces budded virus infection. Tracheal branches provide a conduit for non-occluded virions (budded virus) to pass through the basal lamina barrier and disseminate BmMNPV in the silkworm silk gland.

Cooperation of ie1 and p35 genes in the activation of baculovirus AcMNPV and HzNV-1 promoters

HzNV-1 is a non-occluded virus belongs to the family of the baculovirus. One of the first detectable transcripts expressed by HzNV-1 virus infection is a 6.2kb gene, hhi1, located in the HindIII-I fragment of the viral genome. Here we show that infection of baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) could activate the expression of the hhi1 promoter. By using constructs containing progressive deletions of the upstream regulatory regions of the hhi1 gene, we demonstrated that the most highly activated area was located between nucleotides −62 to +277 of the hhi1 promoter. We subsequently searched the entire 130kb AcMNPV genome and identified two baculovirus genes, ie1 and p35, that their cooperation is required for the activation of the hhi1 promoter. Further, by taking advantages of a baculovirus DNA chip and low background baculovirus gene expressions in the mammalian cells, we went on to identify a specific set of baculoviral genes, including orf21 and orf25, that could be specifically activated by the combination of ie1 and p35 genes. We conclude that a unique cooperative mechanism of ie1 and p35 exists in the genome of AcMNPV, which can activate the expression of a specific set of AcMNPV and HzNV-1 promoters.

In vitro host range of the Hz-1 nonoccluded virus in insect cell lines

A total of 13 insect cell lines spanning 4 orders (Lepidoptera, Coleoptera, Diptera, and Homoptera) were tested for their ability to replicate the nonoccluded virus Hz-1. Only the Lepidopteran cell lines supported replication of the virus with TN-CL1 and BCIRL-HZ-AM1 producing the highest titers of 2.4 x 10(8) tissue culture infective dose (TCID)50/ml and 2.0 x 10(8) TCID50/ml, respectively. A codling moth cell line (CP-169) was the only Lepidopteran cell line that did not replicate the virus and transfection of this cell line with Hz-1 DNA failed to replicate the virus. Also, transfection with DNA from a recombinant baculovirus carrying the red fluorescent protein gene (AcMNPVhsp70 Red) was not expressed in CP-169 cells. The replication cycle of Hz-1 in BCIRL-HZ-AM1 cells showed that this virus replicated rapidly starting at 16 h postinoculation (p.i.) and reaching a peak titer of 1.0 x 10(8) TCID50/ml 56 h postinoculation. Hz-1 when compared with several other baculoviruses has the widest in vitro host spectrum.

Microbial control of arthropod pests of tropical tree fruits

A multitude of insects and mites attack fruit crops throughout the tropics. The traditional method for controlling most of these pests is the application of chemical pesticides. Growing concern on the negative environmental effects has encouraged the development of alternatives. Inundatively and inoculatively applied microbial control agents (virus, bacteria, fungi, and entomopathogenic nematodes) have been developed as alternative control methods of a wide variety of arthropods including tropical fruit pests. The majority of the research and applications in tropical fruit agroecosystems has been conducted in citrus, banana, coconut, and mango. Successful microbial control initiatives of citrus pests and mites have been reported. Microbial control of arthropod pests of banana includes banana weevil, Cosmopolites sordidus Germar (Coleoptera: Curculionidae) (with EPNs and fungi) among others Oryctes rhinoceros (L.) is one of the most important pests of coconut and one of the most successful uses of non-occluded virus for classical biological control. Key pests of mango that have been controlled with microbial control agents include fruit flies (Diptera: Tephritidae) (with EPNs and fungi), and other pests. Also successful is the microbial control of arthropod pests of guava, papaya and pineapple. The challenge towards a broader application of entomopathogens is the development of successful combinations of entomopathogens, predators, and parasitoids along with other interventions to produce effective and sustainable pest management.

Differential adsorption of occluded and nonoccluded insect-pathogenic viruses to soil-forming minerals.

Soil represents the principal environmental reservoir of many insect-pathogenic viruses. We compared the adsorption and infectivity of one occluded and two nonoccluded viruses, Helicoverpa armigera single nucleopolyhedrovirus (HaSNPV) (Baculoviridae), Cricket paralysis virus (CrPV) (Dicistroviridae), and Invertebrate iridescent virus 6 (IIV-6) (Iridoviridae), respectively, in mixtures with a selection of soil-forming minerals. The relative infective titers of HaSNPV and CrPV were unchanged or slightly reduced in the presence of different minerals compared to their titers in the absence of the mineral. In contrast, the infective titer of IIV-6 varied according to the mineral being tested. In adsorption studies, over 98% of HaSNPV occlusion bodies were adsorbed by all the minerals, and a particularly high affinity was observed with ferric oxide, attapulgite, and kaolinite. In contrast, the adsorption of CrPV and IIV-6 differed markedly with mineral type, with low affinity to bentonites and high affinity to ferric oxide and kaolinite. We conclude that interactions between soil-forming minerals and insect viruses appear to be most important in nucleopolyhedroviruses, followed by invertebrate iridescent viruses, and least important in CrPV, which may reflect the ecology of these pathogens. Moreover, soils with a high content of iron oxides or kaolinite would likely represent highly effective reservoirs for insect-pathogenic viruses.

Transmission of viruses to mosquito larvae mediated by divalent cations

The two major groups of pathogenic viruses in mosquitoes are the occluded viruses, represented by baculoviruses and cypoviruses, and the non-occluded viruses, represented by the densoviruses and the iridoviruses. Baculoviruses, densoviruses, and iridoviruses are DNA viruses, while cypoviruses are the major group of RNA viruses reported from mosquitoes. Research on mosquito pathogenic viruses has been limited, in part, due to the inability to effectively transmit them to the larval mosquito host. Recently, there have been tremendous advancements in the ability to transmit mosquito baculoviruses and cypoviruses with the finding that transmission is mediated by divalent cations. Oral transmission of both baculoviruses and cypoviruses to mosquito larvae is enhanced by magnesium and inhibited by calcium ions. The current status of transmission for each of the major groups is reviewed with emphasis on the common role of divalent cations in transmission of the distantly related baculoviruses and cypoviruses.

Nucleopolyhedrovirus infected central nervous system cells of Bombyx mori (L.) (Lepidoptera: Bombycidae)

BmMNPV, a Nucleopolyhedrovirus isolated from infected Bombyx mori (L.) larvae in Paraná State--Brazil, was used to inoculate healthy 5th-instar B. mori larvae and examine the infection on central nervous system (CNS) cells. Samples of nervous tissue were removed from the infected insects, at different sampling times, and processed for cytopathology studies by light and transmission electron microscopy using routine techniques. The experiment included both inoculated and non-inoculated larvae (control). BmMNPV infection was detected on the 5th day after inoculation in CNS cells. Initially, infection was characterized by nuclear hypertrophy and the presence of virogenic stroma, in which the progeny virions were produced. Virions are enveloped and occluded into protein crystal, the polyhedra. Lyses of infected CNS cells were undetected; however, free mature polyhedra were seen in spaces inside the CNS. These polyhedra possibly came from trachea that penetrate the CNS and its cells, which are susceptible to BmMNPV and lyses after infection. We conclude that the tracheal system is responsible for disseminating BmMNPV infection in B. mori CNS and that the tracheal branches allow non-occluded virions to pass through the blood-brain barrier.

Insect cells–Baculovirus system: Factors affecting growth and low MOI infection

The use of low multiplicity of infection (MOI) for the production of baculovirus in insect cell sytems is an attractive alternative for large-scale production processes. Such processes may be focused on the production of biological insecticides or on the expression of medically useful foreign genes. In the present study, the effect of MOI, cell inoculum age and inoculation procedure (carry-over of spent medium from the pre-culture) was studied. While some influences of inoculum age and medium were found, the overhelming effect is related to MOI. The data obtained describe the dynamics of the changes of non-occluded virus (NOV) in time, giving a useful insight into the mechanism of the cell–virus system.

Characterization of pif, a gene required for the per os infectivity of Spodoptera littoralis nucleopolyhedrovirus.

During plaque purification of Spodoptera littoralis nucleopolyhedrovirus in S. littoralis Sl52 cell culture, a deletion mutant virus was isolated. Analysis of the biological properties of this mutant virus revealed an absence of per os infectivity of the occluded virus. Infectivity by injection of the non-occluded (budded) virus is not different between the wild-type and the deleted virus. Restriction analysis of the mutant virus genome revealed a 4.5 kb deletion within the NotI D fragment. The observed phenotype was mapped to the deleted region by rescue experiments. The deletion was characterized and the equivalent DNA fragment on the wild-type virus was sequenced. By co-transfecting the DNA of the deleted virus with plasmids derived from the wild-type virus, it was possible to determine that ORF 7 in this fragment is responsible for the observed phenotype. ORF 7, called pif (per os infectivity factor), is homologous to ORF 119 of Autographa californica nucleopolyhedrovirus. Similar ORFs are present in all sequenced baculoviruses. The product of this gene is an occlusion body-derived virion structural protein required only for the first steps of larva infection, as viruses being produced in cells expressing the gene but not containing it in their genomes are able to produce successful infections.

Insect Pathogens as Biological Control Agents: Do They Have a Future?

Naturally occurring entomopathogens are important regulatory factors in insect populations. Many species are employed as biological control agents of insect pests in row and glasshouse crops, orchards, ornamentals, range, turf and lawn, stored products, and forestry and for abatement of pest and vector insects of veterinary and medical importance. The comparison of entomopathogens with conventional chemical pesticides is usually solely from the perspective of their efficacy and cost. In addition to efficacy, the advantages of use of microbial control agents are numerous. These include safety for humans and other nontarget organisms, reduction of pesticide residues in food, preservation of other natural enemies, and increased biodiversity in managed ecosystems. As with predators and parasitoids, there are three basic approaches for use of entomopathogens as microbial control agents: classical biological control, augmentation, and conservation. The use of a virus (Oryctes nonoccluded virus), a fungus (Entomophaga maimaiga), and a nematode (Deladenus siricidicola )a s innoculatively applied biological control agents for the long-term suppression of palm rhinoceros beetle (Oryctes rhinoceros), gypsy moth (Lymantria dispar), and woodwasp (Sirex noctilio), respectively, has been successful. Most examples of microbial control involve inundative application of entomopathogens. The most widely used microbial control agent is the bacterium Bacillus thuringiensis. The discovery of new varieties with activity against Lepidoptera, Coleoptera, and Diptera and their genetic improvement has enhanced the utility of this species. Recent developments in its molecular biology, mode of action, and resistance management are reviewed. Examples of the use, benefits, and limitations of entomopathogenic viruses, bacteria, fungi, nematodes, and protozoa as inundatively applied microbial control agents are presented. Microbial control agents can be effective and serve as alternatives to broad-spectrum chemical insecticides. However, their increased utilization will require (1) increased pathogen virulence and speed of kill; (2) improved pathogen performance under challenging environmental conditions (cool weather, dry conditions, etc.); (3) greater efficiency in their production; (4) improvements in formulation that enable ease of application, increased environmental persistence, and longer shelf life; (5) better understanding of how they will fit into integrated systems and their interaction with the environment and other integrated pest management (IPM) components; (6) greater appreciation of their environmental advantages; and (7) acceptance by growers and the general public. We envision a broader appreciation for the attributes of entomopathogens in the near to distant future and expect to see synergistic combinations of microbial control agents with other technologies. However, if future development is only market driven, there will be considerable delays in the implementation of several microbial control agents that have excellent potential for use in IPM programs.

Control of the coconut pest Oryctes rhinoceros L. using the Oryctes virus

The coconut palm is an important plantation crop in India, where it is cultivated on 1.796 million hectares. The rhinoceros beetle, Oryctes rhinoceros L. (Coleoptera: Scarabaeidae) is a serious pest of coconut throughout India and southeast Asia, causing an estimated 10% yield loss in the crop. Successful biological control of this pest could be achieved using the non-occluded Oryctes virus (syn. Baculovirus oryctes or Oryctes baculovirus). This review provides an account of this microbial agent, its biology, effects and impact, production and maintenance and alternative hosts, particularly in the context of the Indian situation. It also proposes future areas for investigation on the virus, in order to achieve its commercial viability and more widespread use.

Peroral infectivity of non-occluded viruses of Bombyx mori nucleopolyhedrovirus and polyhedrin-negative recombinant baculoviruses to silkworm larvae is drastically enhanced when administered with Anomala cuprea entomopoxvirus spindles.

Non-occluded viruses (NOVs) of Bombyx mori nucleopolyhedrovirus (BmNPV) are poorly infectious to silkworm larvae when administered by peroral inoculation, although they are highly infectious when injected into the insect haemocoel. In the present study, it is demonstrated that NOVs of BmNPV became highly infectious even through peroral inoculation when administered with spindles (proteinaceous structures) of Anomala cuprea entomopoxvirus (AcEPV). Marked enhancement of peroral infectivity of NOVs by AcEPV spindles (nearly 1000-fold higher in the strongest case) was observed in all growth stages of silkworm larvae tested (2nd to 5th instar). Similarly, peroral infectivity of polyhedrin-negative recombinants of BmNPV, which do not produce polyhedra, was also enhanced remarkably by AcEPV spindles. In contrast, spheroids (proteinaceous structures containing AcEPV virions) did not enhance the peroral infectivity of either NOVs or the recombinant BmNPV in silkworm larvae.

Effect of Light Energy on Alkali-Released Virions from Anagrapha falcifera Nucleopolyhedrovirus

We compared the insecticidal activities of occluded and nonoccluded AfMNPV baculovirus obtained by dissolving the occlusion bodies (OB) with sodium carbonate. Droplet feeding and cotton leaf feeding bioassay techniques were used to determine the dose response against neonate Trichoplusia ni (Hübner) and loss of insecticidal activity when the virus was exposed to simulated sunlight from a xenon light source. Using droplet bioassays to determine a dose response, nonoccluded virus (NOV) was 20 times more active (LC50 = 4.8 × 103 OB/ml, dissolved) than occluded virus (LC50 = 9.6 × 104 OB/ml) when the samples remained wet. However, NOV lost activity when air dried before being tested by droplet (LC50 > 1.0 × 106 OB/ml) or leaf feeding (LC50 > 3.0 × 106 OB/ml) bioassays. Adding sucrose to NOV prevented the loss of insecticidal activity when samples were dried. The activity of NOV with 2% sucrose was similar to that of occluded virus samples, with or without sucrose, in both droplet feeding and leaf feeding assays. These results indicate that the OB protected the insecticidal activity of virions from the detrimental effects of drying. The OB also provided some protection from the detrimental effects of simulated sunlight (xenon) exposure. NOV samples exposed to xenon light had significantly greater loss of insecticidal activity than did similar samples of occluded virus. Without advancement in technologies, such as formulations, possible benefits of increased insecticidal activity from the use of nonoccluded virus is probably not sufficient to offset the rapid loss of activity due to drying or light exposure.

Ultrastructure and pathogenesis of Monodon baculovirus (Pm SNPV) in cultured larvae and natural brooders of Peneaus monodon

Monodon baculovirus (MBV) occurred in the hepatopancreas of cultured larvae, zoea, mysis and post-larvae and in wild caught juveniles, sub-adults and brood stocks of Penaeus monodon. Infected larvae exhibited lethargy and reduced feeding and preening activities while infected juveniles, sub-adults and brooders exhibited normal behaviour. MBV-infected hepatopancreatic cells exhibited a 300% volume increase in the hypertrophied nuclei, which contained eosinophilic, spherical, intranuclear occlusion bodies. At the apical cell surface, the number of microvilli were greatly reduced by cytolysis. The cytoplasm contained numerous vacuoles and few mitochondria. Two types of occlusion bodies were observed. Type 1 comprised a paracrystalline array of polyhedrin sub-units with a lattice spacing of 5–7 nm, with numerous occluded virions and a few non-occluded virions in the periphery within a double envelope measuring 267±2 nm long and 78±3 nm wide. Type 2 occlusion bodies consisted of non-crystalline, granulin-like sub-units each measuring 12 nm in diameter and contained mostly non-occluded virions measuring 326±4 nm long and 73±1 nm wide. In the zoea, mysis and post-larvae, the average infection rates for MBV were 28%±2%, 57%±3% and 91%±1%, respectively. Mortality rates were greater in the infected than in the uninfected post-larvae, at 81%±0% and 11%±0%, respectively. The mortality rate in MBV infected zoea and mysis was 23%±3% and 49%±2%, respectively, while in the uninfected larvae, it was 5%±0% and 8%±0%, respectively. The mortality rate for the infected and uninfected nauplii was similar at 3%±0%. In the brood stocks, the infection rate was 21%±1%, while in the juveniles and sub-adults, it was lower at 4%±0% and 5%±1%. MBV infected larvae harboured 10 times more bacteria than uninfected larvae.

Diseases of mites.

An overview is given of studies on diseases of mites. Knowledge of diseases of mites is still fragmentary but in recent years more attention has been paid to acaropathogens, often because of the economic importance of many mite species. Most research on mite pathogens concerns studies on fungal pathogens of eriophyoids and spider mites especially. These fungi often play an important role in the regulation of natural mite populations and are sometimes able to decimate populations of phytophagous mites. Studies are being conducted to develop some of these fungi as commercial acaricides. Virus diseases are known in only a few mites, namely, the citrus red mite and the European red mite. In both cases, non-occluded viruses play an important role in the regulation of mite populations in citrus and peach orchards, respectively, but application of these viruses as biological control agents does not seem feasible. A putative iridovirus has been observed in association with Varroa mites in moribund honeybee colonies. The virus is probably also pathogenic for honeybees and may be transmitted to them through this parasitic mite. Few bacteria have been reported as pathogens of the Acari but in recent years research has been concentrated on intracellular organisms such as Wolbachia that may cause distorted sex ratios in offspring and incompatibility between populations. The role of these organisms in natural populations of spider mites is in particular discussed. The effect of Bacillus thuringiensis on mites is also treated in this review, although its mode of action in arthropods is mainly due to the presence of toxins and it is, therefore, not considered to be a pathogen in the true sense of the word. Microsporidia have been observed in several mite species especially in oribatid mites, although other groups of mites may also be affected. In recent years, Microsporidia infections in Phytoseiidae have received considerable attention, as they are often found in mass rearings of beneficial arthropods. They affect the efficacy of these predators as biological control agent of insect and mite pests. Microsporidia do not seem to have potential for biological control of mites.

Comparison of in vivo activity of virus from a deleted polyhedrin-gene strain of a single-nucleocapsid baculovirus and a multiple-nucleocapsid baculovirus

Larvae of Trichoplusia ni, Helicoverpa zea and Heliothis virescens were assayed for their relative suscepti-bility to in vitro produced, nonoccluded virus (P-NOV) from a deleted polyhedrin-gene strain of the nucleopolyhedroviruses of Autographa californica (P-AcMNPV) and Helicoverpa zea (P-HzSNPV). There was a 90-fold difference in P- NOV activity (LC50 values based upon TCID50/mm2) between P-AcMNPV (vs. T. ni) and P-HzSNPV (vs. H. zea) when each virus was assayed against its respective permissive host. These differences in P-NOV activity were within the same range one would expect based upon their reported LC50 values and the estimated numbers of virions embedded in occlusion bodies (OB) of the wild-type (Wt) isolate of these viruses. Differences in LC50 values (TCID50/mm2) between P-NOV of P-AcMNPV and P-NOV of P-HzSNPV using H. virescens larvae (a permissive host susceptible to both viruses) however, were much greater ( > 300-fold) than expected if based upon the number of virions/WtOB. Closer agreements in LC50 values between P-NOV and occluded viruses of WtOB were obtained for H. zea or H. virescens larvae exposed to P-HzSNPV (ca. 1.3-fold difference) or H, zea and H. virescens larvae exposed to P-AcMNPV (ca. a 15-fold difference). Results using a non-susceptible host (P-NOV of P-HzSNPV vs. T. ni) or a semi-permissive host (P-NOV of P-AcMNPV vs. H, zea) generally agreed with previous citations using occluded virions of WtOB.

Coinfection of Spodoptera exigua and Spodoptera frugiperda Cell Lines with the Nuclear Polyhedrosis Viruses of Autographa californica andSpodoptera exigua

The Autographa californica multinucleocapsid nuclear polyhedrosis virus (AcMNPV) has a broad host range among Lepidoptera. In contrast, the Spodoptera exigua MNPV (SeMNPV) can replicate efficiently only in S. exigua larvae or S. exigua-derived cell lines. In this study, we examined the coinfection of S. exigua Se301 and Spodoptera frugiperda IPLB-SF21AEII (Sf21) cell lines with SeMNPV and AcMNPV recombinant (Ac360-501β-gal) which was constructed for expression of β-galactosidase under control of the polyhedrin promoter. Coinfection led to the restriction as the level of late gene expression, nonoccluded virus production, and DNA replication of Ac360-501β-gal in both Se301 and Sf21 cell lines. In contrast, Ac360-501β-gal supported the SeMNPV replication in Sf21 cells. Occurrence of recombinants, between Ac360-501β-gal and SeMNPV, with expanded host range was not observed in coinfected Sf21 cells. This suggests that Ac360-501β-gal supports the SeMNPV replication through trans-activation.