Results of the studies on the morphologic and molecular biologic characteristics of Hantaan virus (HTNV), one of the etiologic agents of Hemorrhagic fever with renal syndrome (HFRS), revealed that HTNV was a member of Family Bunyaviridae and its RNA divided into three segments. And the nucleotide sequences of these segments also were known and the differences in nucleotide sequences of HTNV from other members of genus Hantavirus were clearly evaluated. But the morphorgenesis, pathogenesis of HFRS and the replication time had not been clearly determined. In this study, to estimate the replication time of HTNV in Vero E-6 cells, Vero cells were infected with HTNV 76/118 strain, and cells were harvested from two hours post-infection up to 24 hours at two hours-intervals. Harvested cells were treated with ordinary techniques for electron microscopy and immune-electron microscopy. And then thin sections were observed under transmission electron microscope. HTNV particles were not found in the cytoplasm and in the extracellular space between $2{\sim}8$ hours after inoculation of virus, but virus particles were observed in extracellular space near the cell membrane of Vero-E6 cells 10 hours after infection. In immune electron microscopy, mature HTNV particles in extracellular spaces and immature virus labelled with gold particles in the cytoplasm of Vero E-6 cell 10 hours after infection of HTNV could be seen. This results suggest that the replication time of HTNV might be about 10 hours.

Most of the currently licensed viral and bacterial vaccines produced in the world are in state of antigen suspension and the immunogenicity of vaccines could be maintained for one or two years only by keeping in the refrigerator, but without refrigeration vaccines would easily lose their immunogenicites. In this study, as a step to develope the method of increasing the stability of vaccines and maintaining the immunogenicity of vaccines for a long time at room temperature or higher temperature, trehalose, glucose and lactose at different concentration were added into the Hantaan virus vaccines and then kept at $37^{\circ}C$ for 12, 24, 48 hours and at room temperature for seven days respectively. Treated vaccines were then inoculated respectively into ICR mice and the titers of antibody against the antigen of Hantaan virus from the mice sera were evaluated. Vaccine without sugar lost immunogenicity completely in 24 hour at $37^{\circ}C$, but the vaccines containing trehalose could maintain some of the immunogenicity even after exposure at $37^{\circ}C$ for 48 hours and the best concentration of trehalose for maintaining the immunogenicities of vaccines was $7.5{\sim}10$ percent. The results suggest that addition of trehalose could increase the stability of Hantaan virus vaccine.

Prospect Hill Virus (PHV) is the well known serotype of hantavirus, a newly established genus in family Bunyaviridae. Extensive studies have upheld the original view of PHV genetics with three genes such as nucleocapsid (N) protein, envelope proteins (G1, G2) and RNA dependent RNA polymerase. In this study, we report the existence of additional gene that is encoded in an overlapping reading frame of the N protein gene within S genome segment of PHV. This gene is expected to encode a nonstructural small (NSs) protein and it seems to be only found in PHV infected cell. The presence and synthesis of NSs protein could be demonstrated in the cell infected with PHV using anti-peptide sera specific to the predicted amino acid sequence deduced from the second open reading frame. Ribosomal synthesis of this protein appears to occur at AUG codon at the 83rd base of S genome segment, downstream of N protein initiation codon. This protein is small in size (10.4 KDa) and highly basic in nature. The expression strategy of NSs protein appears that a signal mRNA is used to translate both N and NSs protein in PHV infected cell. 10 KDa protein in virus infected cell lysates can bind to mimic dsRNA. This fact strongly suggests that NSs protein may be involved in virus replication on late phase of viral life cycle.

HIV-1 Tat, a strong transactivator, is essential for the HIV-1 replication and AIDS progression. The Tat function is markedly inhibited by human p53 anti-oncogene. However, the detail mechanism has not yet been clearly revealed. In our previous report, we have addressed that p53 is unlikely to interact directly with HIV-1 Tat. In the consecutive experiments, Tat-phosphorylation was found to increase in proportional to the amounts of transfected p53. This work was initiated to identify the signaling factor that is involved in the p53-mediated Tat suppression. Several protein kinases were tested for the phosphorylation of Tat, and we found that PKR is likely to be involved in the p53-mediated Tat suppression. PKR was co-immunoprecipitated by anti-Tat antibody in the Tat-expressing Jurkat cell lysates only when the cells were transfected by p53, indicating that PKR-Tat interaction depends on the p53 activity. The interaction seems to result in PKR-mediated Tat-phosphorylation. Tat function was not blocked by p53 when co-transfected trasiently with antisense-PKR. We have generated PKR-knock out Jurkat cell clone. The PKR defective Jurkat cells didn't show the p53-mediated Tat suppression. These data indicate that p53-mediated Tat suppression is strongly associated with PKR. PKR-mediated Tat phosphorylation experiments are now under investigation by kinase assay and co-immunoprecipitation in the presence or absence of p53.

Small round structured viruses (SRSV) are the major ethological agents which can cause outbreaks of non-bacterial gastroenteritis or food poisoning both in children and adults. The classification of family Caliciviridae to which SRSV belong, is based on the genome encoding three open reading frames. The rotavirus is another major pathogen which causes diarrhea in young children. We examined stool specimens obtained from diarrheal patients in Wonju from which bacterial pathogens were not found. To detect causative viruses from stool specimens of patients, reverse transcription (RT)-polymerase chain reaction (PCR) or nested PCR using rotavirus or SRSV specific primers was performed. In this study, RT-nested PCR procedure which can amplify a 330 bp fragment derived from RNA dependent RNA polymerase (RDRP) region within ORF1 was applied for the detection of SRSV. For the detection of rotaviruses, a 877 bp fragment from the VP4 region of rotavirus genome was amplified. As a result, rotavirus was not detected while SRSV sequences were detected from one out of five specimens. The nucleotide and amino acid sequences of the Wonju isolate were compared with other 6 Korean isolates which have been isolated and sequenced in our laboratory. Sequence analysis revealed that the Wonju isolate was rather distinct from other Korean isolates: the Wonju isolate was closer to genogroup I of SRSV while other 6 Korean isolates belonged to genogroup II.

The relationship between second messenger cGMP and human cytomegalovirus (HCMV) replication was investigated. First, the intracellular level of cGMP ([cGMP]i) in HCMV-infected cells was measured. The [cGMP]i increased at early times after HCMV infection, reached maximum level at 12 hr and returned to basal level at 24 hr after virus infection, while [cGMP]i in mock-infected cells remained relatively unchanged. Increasing [cGMP]i resulted in enhanced transcription of HCMV major immediate early gene. For early gene expression, cGMP had varying effect. Expression of 1.2 kb RNA decreased and 2.2 kb RNA increased with increasing cGMP, while 2.7 kb RNA gene expression was not affected. HCMV early genes are regulated by immediate early gene, and the effect of cGMP on the regulatory effect of major immediate early gene on early genes was investigated. In the absence of cGMP, major immediate early gene repressed 2.7 kb RNA gene expression, while 1.2 kb RNA and 2.2 kb RNA early genes were not significantly affected. In the presence of $1\;{\mu}M$ cGMP, however, major immediate early gene stimulated the expression of three early genes.

The nested polymerase chain reaction (PCR) assay was used to determine the sequences of reverse transcriptase (RT) codons 41, 67, 70, 210, 215 and 219 of human immunodeficiency virus-1 (HIV-1) pol gene. Template DNA was obtained from uncultured peripheral blood mononuclear cells from 27 Korean HIV-1 infected patients treated with ZDV and Korean red ginseng. The second PCRs were done for 2 separated regions (RT codons $13{\sim}98$ and $152{\sim}259$) with $5\;{\mu}l$ of the first PCR productNucleotide sequences were determined by direct sequencing. In the 27 patients, CD4+ cell count decreased from $230{\pm}117/{\mu}l$ to $152{\pm}162/{\mu}l$ for $46{\pm}26$ months (Mo), and actual duration of ZDV intake was $72{\pm}16$ Mo. In the 16 patients who had been treated with ZDV therapy ${\ge}25$ Mo, the incidences of 70R, 215F/Y, and 41L were 61%, 28% and 22%, respectively and those of 67N, 210W and 219Q were 17%. The incidences of 215F/Y were 6.7% for group ${\le}12$ Mo treatment, 22.7% for group with 13 to 24 Mo, and 27.8% for group ${\ge}25$ Mo. There was no mutation in 9 patients. It might be associated with the interruption of ZDV therapy for more than 6 months in 6 patients. This study shows that the detection of mutation could be useful prognostic marker with other clinical and virological data, and very low mutation rate is dectected compared to overseas reports.

Zosteriform lesions, occurring after left flank and intravaginal inoculations of Balb/c mice with the Herpes simplex virus type 1 strain McKrae, developed in clinically normal skin via nerve endings. The developments of zosteriforms were standardized in 5 phases with the following references; formation of small vesicles (phase 1); occurrence of erosion and ulceration of local lesions (phase 2); occurrence of ulcerations (phase 3); occurrence of severe ulcerations (phase 4); and death (phase 5). These results provide two valuable zosteriform models to further investigate and analyze the pathological symptoms in susceptible animals infected with HSV-1 or HSV-2 and DNA vaccines.