Growth experiment of Hantaan virus in A549 cells: an attempt to improve the immunofluorescent antibody technique for hemorrhagic fever with renal syndrome

An assay method for the infectivity of Hantaan virus, a causative agent of HFRS (hemorrhagic fever with renal syndrome), was developed by the use of IFA (immunofluorescent antibody technique). With the aid of this method, the growth characteristics of Hantaan virus, 76-118 strain, were followed in A549 cells. At a maximal MOI (multiplicity of infection) of 1.6 VAIU (viral antigen-inducing units) per cell, the conventionally available value, plateau level potencies of the viral antigen and virus infectivity were attained at eight and ten days postinfection, respectively, and most of the infective virus produced accumulated in the culture fluids of infected cells. When infections were defined with MOI values in terms of VAIU per cell, development of the viral antigen was highly consistent and followed a given pattern of kinetics. Based on these findings, a protocol for preparation of the viral antigen in IFA was presented, wherein spot culture and FBS treatment were emphasized as effective procedures to minimize non-specific staining.

Antigenic and genetic properties of viruses linked to hemorrhagic fever with renal syndrome

Hemorrhagic fever with renal syndrome (HFRS) comprises a variety of clinically similar diseases of viral etiology that are endemic to and sporadically epidemic throughout the Eurasian continent and Japan. Although HFRS has not been reported in North America, viruses that are antigenically similar to HFRS agents were recently isolated from rodents in the United States. Examination and comparison of eight representative isolates from endemic disease areas and from regions with no known associated HFRS indicate that these viruses represent a new and unique group that constitutes a separate genus in the Bunyaviridae family of animal viruses.

Positive serological evidence that Hantaan virus, the etiologic agent of hemorrhagic fever with renal syndrome, is endemic in Canada

Hemorrhagic fever with renal syndrome is endemic in most parts of the world. The etiological agent in known as Hantaan virus. More than 2000 Canadian sera from all age groups and provinces were tested for the presence of antibody to this virus by the indirect immunofluorescent antibody technique. The frequency of seropositivity ranged from 0.3 to 4.0%, with the national average being 1.4%. Newfoundland and New Brunswick in the Atlantic region had the highest positivity, being higher than hyperendemic areas in Korea. The inland provinces of Ontario, Manitoba, and Alberta had only 0.5% positives to Hantaan virus. In contrast, approximately 1.5% of sera from Saskatchewan, Quebec, and British Columbia were positive. No correlation in positivity was found between geography or sex, but positivity did increase with age. The highest titres were found in the group aged 65 to 93 years.

Studies on compartmentation of S-adenosyl-L-methionine in Saccharomyces cerevisiae and isolated rat hepatocytes

The existence of metabolically distinct pools of S-adenosyl-L-methionine in Saccharomyces cerevisiae and isolated rat hepatocytes was investigated. Utilizing a relatively long labeling period with [methyl-14C]methionine, a metabolically 'stable' pool was labeled. A subsequent short labeling with [methyl-3H]methionine selectively labeled a putative metabolically 'labile' pool. The existence of these distinguishable pools was ascertained by following the 3H and 14C label disappearance in S-adenosyl-L-methionine during the chase-period in label-free media containing cycloleucine to prevent further synthesis of S-adenosyl-L-methionine. In both yeast and hepatocytes, the 3H/14C ratio in S-adenosyl-L-methionine decreased sharply. The individual 3H and 14C decrease in S-adenosyl-L-methionine showed t1/2 values of 3 and 8 min for yeast and 4 and 18 min for hepatocytes. The results strongly indicate that at least two metabolically distinct S-adenosyl-L-methionine pools actually do exist in both systems. Subcellular fractionation revealed that the 'labile' pool exist in the cytosol for both yeast and hepatocytes while the 'stable' pool exists in the vacuolar and the mitochondrial fraction for the yeast and hepatocytes respectively. The S-adenosyl-L-methionine pools were also studied in normal yeast under anaerobic chase condition and petite mutant yeast. Sharply contrasting with aerobically chased normal yeast, both showed closely parallel 3H and 14C decreases in S-adenosyl-L-methionine.

Isolation of Hantaan virus, the etiologic agent of Korean hemorrhagic fever, from wild urban rats

Urban rats captured in Seoul and four nearby Korean cities were found to have immunofluorescent antibodies reactive with Hantaan virus, the etiologic agent of Korean hemorrhagic fever (KHF). Serum antibodies were detected in 13% from 477 Rattus norvegicus and 11% of 47 Rattus rattus. Hantaan viral antigen was found in pulmonary tissues of 42 animals, and Hantaan virus was recovered from 23 rats, all but two of which were R. norvegicus. Wistar rats were qualitatively much more sensitive than Apodemus agrarius rodents for isolation of virus from tissues of wild rats. Wistar rats inoculated with one of these strains had virus in lung and spleen for at least 75 days. These results document the existence of an urban cycle for Hantaan virus, which had been suspected on the basis of the occurrence of sporadic urban cases in humans of KHF, and suggest that Rattus-borne Hantaan virus may be widely distributed in urban centers.

Laboratory-acquired infections with Hantaan virus, the etiologic agent of Korean hemorrhagic fever

Clinically apparent infections with Hantaan virus, the etiologic agent of Korean hemorrhagic fever, occurred in nine persons exposed to the virus at the Korea University Virus Institute (Seoul) between 1971 and 1979. All were directly related to trapping of wild rodents or work with naturally or experimentally infected wild and laboratory rodents in a designated animal suite. All infections were acquired during the months of November-April, and none was associated with accidental parenteral inoculations. These facts suggested that aerosols produced by chronically infected rodents were the infectious vehicles and that limited air circulation and lowered humidity in the animal rooms during winter months increased the probability of viral transmission. Four persons, including two casual visitors, became ill within four months after the initiation of experimental studies of infections in Wistar rats with Hantaan virus, an occurrence suggesting that this rodent may be a highly infectious host for Hantaan virus.

Hantaan virus, aetiological agent of Korean haemorrhagic fever, has Bunyaviridae-like morphology

Spherical to oval particles with a unit membrane and subunit surface structure were demonstrated by negative-contrast staining of supernatant fluids of A-549 cell cultures infected with strain 76-118 of Hantaan virus. The particles had an average diameter of about 95 nm, with a range of 80 to 110 nm. Similar particles were isolated by buoyant density fractionation in sucrose gradients. In four separate experiments, infectivity cosedimented with 95 nm particles at buoyant densities from 1.15 to 1.18 g/ml. Immunoaggregation of the virions was specifically produced by antisera obtained after Hantaan virus infection of man and rabbit. The known physicochemical and morphological properties of these particles are compatible with those generally reported for the Bunyaviridae family of viruses.

Korean hemorrhagic fever among rural residents in Japan

Naturally occurring infection with Korean hemorrhagic fever virus among four families living in rural areas of northern and central Japan was proved by the demonstration of antibody to the virus. Furthermore, Korean hemorrhagic fever virus antigen was detected in the lung tissues of wild rodents captured in the endemic area. These findings indicate the endemic presence of Korean hemorrhagic fever virus on Honshu Island, Japan.

Intraspecific transmission of Hantaan virus, etiologic agent of Korean hemorrhagic fever, in the rodent Apodemus agrarius

Experimental parameters of infection and intraspecific transmission of Hantaan virus, the etiologic agent of Korean hemorrhagic fever, in Apodemus agrarius rodents were determined. Mice inoculated by the intramuscular route experienced viremia for about 1 week beginning on day 7. After 3 weeks, immunofluorescent and neutralizing antibodies were present and no mouse ever developed signs of acute illness. Virus was recovered from lung, kidney, salivary gland, and liver, and virus excretion in urine, saliva, and feces occurred from about day 10 through day 360 (urine) post-inoculation. Antigen, but not infectious virus, was persistent in lung tissue for as long as 1 year. Horizontal contact infection occurred among cage-mates regardless of sexual pairing up to 360 days after infection and no evidence for participation of ectoparasitic arthropods in such transmission was obtained.

Electron microscope appearance of Hantaan virus, the causative agent of Korean haemorrhagic fever

The morphology and morphogenesis of three strains of Hantaan virus, which causes Korean haemorrhagic fever (KHF), were examined by thin-section and negative-contrast electron microscopy of infected A549 cell-culture specimens. In thin sections, virus was detected within cytoplasmic granular matrices (viroplasms) of the infected cells. Virus particles were spherical (diameter 73 +/- 5 nm), and had an extremely electron-dense core (diameter 47 +/- 6.5 nm). Replication and maturation of the virus seemed to occur in the viroplasm. As infection progressed, viral particles increased in number and were packed into the granular matrices as cytoplasmic crystalline arrays. Viruses seemed to be released from infected cells by cell dissolution. Negative-contrast staining showed that the virus had an icosahedral structure (diameter 80 +/- 2 nm) and annular surface capsomeres. Viruses clumped when exposed to anti-Hantaan virus serum from a convalescent patient. The morphology and morphogenesis of the virus were compatible with those of orbiviruses.

Korean hemorrhagic fever: propagation of the etiologic agent in a cell line of human origin

The etiologic agent of Korean hemorrhagic fever has been propagated in a human cultured cell line derived from a carcinoma of the lung. The cells, described as type II, alveolar epithelial, support replication of the agent and successive passages. Antigen of the Korean hemorrhagic fever agent is readily detected in infected cells by means of direct or indirect fluorescent antibody techniques. Previous attempts to propagate this agent in vitro had been unsuccessful.

Observations on natural and laboratory infection of rodents with the etiologic agent of Korean hemorrhagic fever

Studies were conducted to define the natural host range of the Korean hemorrhagic fever (KHF) agent in South Korea, and to identify colonized rodents susceptible to this infection. Eight species of field rodents were captured in areas of Korea endemic for KHF and their tissues were examined by immunofluorescence for the presence of KHF antigen. One hundred and fourteen of 817 Apodemus agrarius coreae captured between 1974 and 1978 had one or more positive organs. No positive organ was found in 239 rodents of the other seven species examined. Two hundred and thirty-eight specimens of Apodemus agrarius jejuensis captured on Jeju Island, an area thought to be free of disease, were also negative. Attempted laboratory infection of nine species of rodents captured in the field but maintained in the laboratory was successful only in the two subspecies of Apodemus. The 46 specimens of A. a. jejunesis tested in this manner were all uniformly susceptible to infection as determined by immunofluorescence. Serial sacrifice of experimentally infected A. a. jejuensis revealed viremia of short duration terminating on day 10 postinfection. In contrast, other tissues of this animal, including lung, kidney, liver and parotid gland were positive on day 10 and remained so through the 100-day observation period. When 12 species of colonized laboratory rodents were inoculated with KHF agent five were found to develop KHF antibody by indirect immunofluorescence and two, Calomys callosus and Apodemus agrarious ningpoensis, developed detectable KHF antigen in their tissues.

Propagation of Korean hemorrhagic fever virus in laboratory rats

Korean hemorrhagic fever virus (KHFV) has been adapted to the Wistar and Fisher strains of rats. Infection was detected by the appearance of specific antigen in the lung tissue of the infected rats at 14 to 64 days after inoculation and by the appearance of circulating antibodies in ther serum which reacted specifically with KHFV antigen in the lungs of infected Apodemus agrarius subsp. coreae 3 weeks after inoculation. Distribution of antigen in rat tissues as determined by immunofluorescent staining was the same as that in Apodemus mice except that antigen was present in the spleens of rats. Adaptation of KHFV to the laboratory rat provides an animal model that is free of wild rodent viruses and is readily available for use in studies on the characterization of KHFV.