We have now constructed a novel recombinant baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV) producing polyhedra with Bacillus thuringiensis (Bt) CryIAc crystal protein. The recombinant polyhedra produced by the recombinant baculovirus, Btrus, in insect cells was characterized. The recombinant baculovirus has two independent transcription units in opposite orientations with two promoters, p10 or polyhedrin gene promoter each initiating transcription of either native polyhedrin or fusion protein with polyhedrin and Bt Cry1Ac crystal protein. Surprisingly, this recombinant baculovirus stably produced recombinant polyhedra which were nearly similar to those of wild-type AcNPV. The immunogold staining experiment showed that the recombinant polyhedra were assembled with polyhedrin and Bt Cry1Ac crystal protein, and contained virus particles. Insecticidal toxicity of recombinant polyhedra of Btrus to the fall webworm, Hyphantria cunea, was strikingly improved in comparison with the wild-type AcNPV.

Hantaan virus (HTNV), the etiologic agent of hemorrhagic fever with renal syndrome (HFRS), belongs to the genus Hantavirus, and has three single negative stranded RNA genome segments. HTNV strain Howang isolated from the blood of severe case of Korean HFRS is more virulent than HTNV 76/118 and the M and S genome segments' nucleotide sequence of Howang strain showed 93.5% and 94% homology to each segment of HTNV 76/118. We have obtained 6533 nucleotides long sequence of the L genome segment of Howang strain using reverse transcriptase in conjunction with PCR amplification and compared to other hantaviruses. The messenger sense of the L segment contains one long single long open reading frame of 2151 amino acids, which encodes a deduced RNA dependent RNA polymerase of 246.4 kDa caculated molecular weight protein. The nucleotide sequence of the L segment of Howang strain shows 93%, 74%, 66%, 65% homology to HTNV 76/118, Seoul virus 80/39, Puumala virus $H{\ddot{a}}lln{\ddot{a}}s$ B1 and Sin Nombre virus, respectively. The amino acid sequence of the L segment of Howang strain shows 99%, 85%, 68%, 68% homology to HTNV 76/118, Seoul virus 80/39, Puumala virus $H{\ddot{a}}lln{\ddot{a}}s$ B1 and Sin Nombre virus, respectively.

To investigate viral pathogenesis and in vivo efficacy of acyclovir (ACV) in mouse HSV-1 encephalitis models, female BALB/c mice aged 5 weeks were inoculated with strain F either intranasally (IN) or intracerebrally (IC). ACV-treatment by intraperitomeal injection with 0, 5, 10 and 25 mg/kg b.i.d. for 6 days was commenced 1 h after infection. Body weight and signs of clinical disease were noted daily up to 2 weeks. $ED_{50}$ of ACV in IN infection was <5 mg/kg and 14.1 mg/kg in IC infection. Tissues of central nervous system were collected from 2 mice per group everyday up to 5 day p.i. and the virus titers were measured. In IN infection model, high titers in eyes and trigeminal nerves were observed. ACV-treatment showed significant reduction of the titers in all the isolated. In IC infection model, cerebrum, cerebellum and brain stem showed high virus titers. ACV-treatment showed less significant reduction of virus titers than that in IN infection model. Reactivation of explanted trigeminal nerves from mice 30 day p.i. was monitored. In all of ACV treated mice reactivation was observed, i.e. even the highest dose of ACV did not inhibit the establishment of viral latency.

An attractive target for anti-herpes chemotherapy is the herpes simplex virus 1 (HSV-1) protease encoded by the UL26 gene. HSV-1 protease is essential for DNA packaging and virus maturation. To perform high throughput for potent inhibitors, the efficient production of larger amounts of highly purified enzyme and protease activity assay method must be established. In this report, expression in E. coli and purification of the protease gene of HSV-1 strain F was investigated. The protease gene was cloned pET28, and the nucleotide sequence of protease catalytic domain of HSV-1 compared strain F with other strains (KOS and CL101). In these results the F strain was different in base sequence. However, the amino acid sequence was identifical. The HSV-1 protease was purified with His-tagged affinity column. The analysis of HSV-1 protease activity was performed by high performance liquid chromatography.

Human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein is synthesized as a 160 KDa precursor, gp160, that is cleaved by a cellular protease to form the gp120 and gp41 subunits. Mammalian expression vectors were designed that are capable of efficient expression of various mutant envelope glycoproteins derived from a molecular clone of HIV-1. To construct these vectors, one type of mutation was made at the gp120-gp41 cleavage site by oligonucleotide-directed mutagenesis. And another mutation was made to change amino acids in the membrane spanning region of HIV-1 gp41 important for membrane anchorage. Next, these two mutations were combined to generate a vector to have double mutations in cleavage site and membrane-spanning region. These mutants were transiently expressed in mammalian cells. The effect of these mutations on envelope glycoprotein synthesis, proteolytic processing and secretion was determined. In addition, cell surface expression and ability of the glycoprotein to induce syncytium formation were examined. This study provides a mammalian expression system that is capable of efficient expression and secretion of soluble gp160.