United States

Chairman

Dr. James H. Strauss
(1994-1997, Member 1987-1994)
Professor
Division of Biology 156-29
California Institute of Technology
Pasadena, California 91125

Japan

Chairman

Dr. Akira Igarashi
(1992- , Member 1985-1992)
Professor
Institute of Tropical Medicine
Nagasaki University
1-12-4 Sakamoto
Nagasaki 852, Japan

Panel Members

Dr. Mary K. Estes (1991-1995)
Professor
Division of Molecular Virology
Baylor College of Medicine
One Baylor Plaza, Room 923E
Texas Medical Center
Houston, Texas 77030-3498

Dr. Diane Griffin (1994-1997)
Johns Hopkins University
School of Hygiene and Public Health
Room 4013
Baltimore, Maryland 21205

Dr. Clarence J. Peters (1993-1996)
Chief, Special Pathogens Branch
Division of Viral and Rickettsial Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention
1600 Clifton Road
Building 15, SB611, MS G-14
Atlanta, Georgia 30333

Dr. William H. Wunner
(1994-1997, 1985-1994)
Associate Professor
The Wistar Institute
3601 Spruce Street
Philadelphia, Pennsylvania 19104

Dr. Nobuo Hashimoto (1981-   )
Professor
Faculty of Veterinary Medicine
Hokkaido University
N-18, W-9, Kita-ku, Sapporo
Hokkaido 060, Japan

Dr. Akihiko Kawai (1983-   )
Professor
Faculty of Pharmaceutical Sciences
Kyoto University
Yoshida-Shimoadachi-cho, Sakyo-ku
Kyoto 606-01, Japan

Dr. Takeshi Kurata (1992-   )
Director
Department of Pathology
National Institute of Health
1-23-1 Toyama, Shinjuku-ku
Tokyo 162, Japan

Dr. Shudo Yamazaki (1989-   )
Director General
National Institute of Health
1-23-1 Toyama, Shinjuku-ku
Tokyo 162, Japan

Guidelines

Viral Diseases Panels USJCMSP

Rabies

Basic, mission-oriented, or applied studies including control measures, early and late diagnostic techniques, virus reservoirs, and prophylactic procedures

Dengue

Studies of the epidemiology, early confirmatory diagnosis, and pathogenesis of hemorrhagic fever, development of vaccines using selected viral structural components as the primary antigen, basic immunology with respect to classification, and biophysical and biochemical studies

Arboviruses

Studies on the structural elements of arboviruses including isolation and identification of antigenic components

Viral Gastroenteritis

Epidemiologic investigations of infant and adult gastroenteritis using virological techniques, diagnostic methods, antigenic characterization (including human and related animal viruses), studies on host-immune response requisite for vaccine development, epidemiologic surveillance, or control, detection, propagation, assay, and characterization of putative agents for man, and studies of pathogenetic mechanisms and predisposing factors that could lead to improved prophylaxis, therapy, or control

Five-Year Summary

Broad Goals The Viral Diseases Panels emphasize viral enteritis, rabies, hemorrhagic fevers, and arthropod-borne viruses (arboviruses), i.e., dengue and Japanese encephalitis. The broad goals of the Panels are to better understand the basic life cycle of viruses and their natural history and epidemiology, so that advancements can be made in the prevention, control, and treatment of viral diseases. In addition to the four viral syndromes covered each year at the meetings, the Panels have invited lecturers on special topics that deal with other viruses of medical interest. Most recently, topical lectures were presented on measles and poliovirus.

Progress/Accomplishments

Arboviruses

Two arbovirus groups have been included in the U.S.-Japan Program.

Flaviviruses: Flaviviruses including dengue virus, yellow fever virus, and Japanese encephalitis virus continue to be major health threats worldwide. A small number of committed laboratories in Japan and the United States are actively engaged in studying such viruses. Dengue continues to emerge as a worldwide health problem. The disease threatens ever larger areas as urbanization promotes infestation of expanding regions by mosquito vectors. Dengue generally is a debilitating, non-fatal illness. However, a proportion of infected patients (usually children) experience a more severe, sometimes fatal, form of the disease called dengue hemorrhagic fever (DHF). Treatment is mainly supportive. Within the U.S.-Japan Program, molecular epidemiology is being used to study possible changes in dengue viruses during the spread of epidemics. Polymerase chain reaction (PCR) has been transferred to field epidemiological studies, and this new tool has improved detection of dengue viral genomes in the sera of patients.

Control of dengue will occur only after an effective vaccine is developed. Because of a number of scientific problems, the development of new biotechnology-based vaccines against dengue has been slow. There has been good progress in studies on the protective role of T-cells during infection, and on the induction of this protective response by vaccines. These are the best descriptions of the T-cell response after infection with closely related viruses.

Japanese encephalitis (JE) is an arthropod-borne disease endemic in Japan and throughout southeast Asia. The geographic pattern of variation of JE virus isolates is being studied using monoclonal antibodies (mAb) to evaluate viral proteins and primer extension sequencing to evaluate genetic differences. A series of mAb has been used to classify JE virus isolates into five antigenic groups, one of which contains most of the recent epidemic strains. Genetic studies have identified four groups, each representing a distinct genotype and geographic region. These groups are being assessed to ensure that the current vaccine will efficiently protect against all new strains.

As with dengue, studies are underway on the development of a new JE vaccine using biotechnology-based approaches. Extensive basic studies on JE virus have concentrated on virus adsorption to host cells, viral RNA replication, and an antiviral factor found in the culture supernatant of infected cells. These basic studies led to expression of the viral E protein by recombinant vaccinia virus in a way that it was secreted into cell culture supernatant fluids as particles. These particles may be a promising candidate for a second generation of vaccines and a source of inactivated diagnostic reagent. These latter vaccine studies were the results of a collaborative U.S.-Japan research effort. Also, basic studies have led to a new ELISA for JE using nonstructural proteins. This new tool revealed significant inapparent infections among healthy inhabitants in an endemic area.

Alphaviruses: The alphaviruses cause encephalitis, arthralgia, fever, polyarthritis, and headache. Sindbis virus has been extensively used as a model system to study the molecular genetics and molecular biology of alphaviruses. Studies of Sindbis by Panel members have produced numerous advances in our basic knowledge of the events involved in the replication of the virus and its evolution in nature. One interesting outgrowth of this research is a study of interference in the molecular genetic control of the capacity of a mosquito to transmit a virus. Here, the goal is to produce mosquitoes that are unable to serve as virus vectors. Using a Sindbis-based system, mosquitoes have been made transgenic for the expression of foreign genes that interfere with its ability to transmit viruses. Although this work is still preliminary, it holds great promise.

Hemorrhagic Fever Viruses

Research in the area of hemorrhagic fevers has focused on the viruses of the genus Hantavirus (of the family Bunyaviridae) that are associated with hemorrhagic fever with renal syndrome (also known as Korean Hemorrhagic fever and epidemic hemorrhagic fever). In recent years, much progress has been made in unraveling the complex geographic and antigenic patterns of distribution of these viruses. Dr. Joel Dalrymple, a member of the Panel who died in 1993, did pioneering work on the molecular biology of Hantaan virus (Korean hemorrhagic fever virus). His studies led to the discovery that these viruses are worldwide in distribution. Viruses isolated from different countries have different properties, and the occurrence, or lack of occurrence, of severe disease in a country might be because the native virus is either highly virulent or attenuated. Basic molecular studies within this program have helped to identify possible candidate vaccines. Epidemiological surveillance has shown the circulation of hantaviruses (Seoul serotype) among Japanese rodents. A model study system was produced by infection of the rodent species Clethryonomys rufocanus. A long-term Japanese project has contributed vitally important monoclonal antibodies (mAb) that have been used throughout the world for hantavirus studies.

Because of the ongoing epidemic of hantavirus infections in the southwestern United States, it is urgent that studies on hantavirus be expanded. This virus first came to the attention of authorities when a cluster of cases, now referred to as hantavirus pulmonary syndrome (HPS), occurred in the south-western United States. It was shown that this disease, which has a mortality rate greater than 50 percent, was caused by a hantavirus that is rodent associated and found in wild populations of Peromyscus maniculatus.

While studying human cases of hemorrhagic fever thought to be due to dengue in Venezuela, a new arenavirus was identified as the cause of a disease now called Venezuelan hemorrhagic fever. This virus (now called Guanarito virus) is carried by native rodents, and is related to Junin and Machupo, the causative agents of Argentine and Bolivian hemorrhagic fevers, respectively.

Rotaviruses

Viruses that cause enteritis are a major problem worldwide and are the leading cause of infant mortality in the developing world. They include the rotaviruses, of which there are many serotypes, the small round spherical viruses (SRSV) that include Norwalk virus, the astroviruses, and other viruses that to date are not completely characterized. Studies on these viruses have involved a number of collaborative projects between Japanese and American scientists.

Over the years, the epidemiology of many rotaviruses has been presented. They have been classified into a large number of serogroups. Their molecular biology has been intensively studied, and a significant number of vaccine trials have ensued. Rotavirus studies continue as the primary focus of research in the general area of viral enteritis. However, they are complemented by a growing effort on Norwalk and related viruses. Recent studies have focused on the determinants of protective immunity to rotavirus infection. This has aided in the selection of epitopes for use in vaccines. Indeed, polyvalent rotavirus vaccines are being comprehensively assessed. Multivalent vaccines containing the viral surface antigens of the major serologic types of rotaviruses are being tested. It is hoped that the narrow specificity of earlier vaccines can be overcome, and vaccines appropriate to the breadth of viral antigenic variation in nature can be developed. Researchers now have perfected the rotavirus adult mouse model, and this system is yielding particularly important basic data.

Research on rotavirus also includes studies of trends in the distribution of human rotavirus serotypes. It has been found that the viruses change from year to year, and from place to place, but not in any predictable pattern that can be correlated with estimations of morbidity, hospitalization, or deaths. On a molecular level, both G and P serotype studies and nucleotide sequence analysis of VP7 and VP4 genes of rotavirus isolates from humans and animals indicated interspecies transmission of rotavirus. Intragenotypic gene reassortment appears to take place more frequently than intergenotypic combination. Prevalent combinations of G and P serotypes were not uniform throughout the epidemic areas and years. A major success of the program was the Japanese discovery of a new group of human rotavirus (group C) and its successful cultivation in cells.

Studies on Norwalk agent have been difficult because of problems in growing the virus. However, research has resulted in sequencing the genome of the prototype Norwalk virus and determining its structure. This has led to the conclusion that this important group of viruses belongs to the family Caliciviridae. Work has progressed on the baculovirus expression of viral proteins, and the use of these proteins to develop reagents for serological assays. These studies now provide the basis for diagnostics and vaccine development that would not have been possible otherwise as these viruses grow poorly in culture. Additional studies have focused on the diarrhea caused by small round spherical viruses (SRSV). The causative agent of several acute gastroenteritis outbreaks in Japan was identified as astrovirus type 6. A new SRSV, Aichi virus, was isolated from oyster-associated outbreaks of acute gastroenteritis and was shown to be prevalent in many Asian countries.

Rabies

Rabies virus is endemic in many areas of the world, including the United States. There is an effective vaccine for the virus; however, it is expensive, which limits its use in developing countries. There is also a need to control the virus in wildlife populations. Research efforts within the Panels are centered on development of a vaccine for use in humans in developing countries and in wildlife in developed countries. This work has involved live-virus vectoring systems and various expression systems including the baculovirus expression system. Pathogenesis and immunity studies continue in support of vaccine development and assessment. Molecular biologic research on rabies virus also supports the field testing of a vaccinia-vectored rabies vaccine. This vaccine is being assessed in regard to its efficacy for protecting raccoons, the species involved in the most important current epizootic in the United States.

Future Goals

Efforts should be made to extend and apply scientific results from basic studies to solve problems in the prevention and control of the viral diseases in relevant countries or areas. Particular emphasis should be placed on molecular epidemiological surveillance of prevalent viral agents in conjunction with disease outbreaks, application of molecular techniques in the laboratory diagnosis, such as mAb-ELISA and recombinant virusexpressed assay antigen, and development of the genetically engineered vaccines.

Additionally, infections caused by many of the viruses in this program are emerging. The elements that cause emergence should be carefully studied. These could include:

1. Expansion of basic and applied research on viral changes and adaptations influencing emergence. Studies might address issues of viral evolution leading to new or altered viruses with enhanced virulence, or modified transmissibility or infectivity.
2. Extension of basic and applied research on ecologic and environmental factors influencing disease emergence and distribution.
3. Establishment of basic and applied research programs focusing on susceptible hosts and vectors, and their roles during maintenance and emergence of viruses. Studies might include research on mechanisms of pathogenesis or viral/vector/host interactions. This research could include initial development of vaccines and antivirals for the protection of the individual from a specific virus.

Selected References

United States

1. Schmaljohn CS, Hasty SE, Dalrymple JM. Preparation of candidate vaccinia-vectored vaccines for haemorrhagic fever with renal syndrome. Vaccine 1992; 10 (1):10-3.

2. Conner ME, Matson DO, Estes MK. Rotavirus vaccines and vaccination potential. Curr Top Microbiol Immunol 1994; 185:285-337.
3. Strauss JH, Strauss EG. The alphaviruses: Gene expression, replication, and evolution. Microbiol Rev 1994 Sep; 58 (3):491-562.
4. Duchin JS, Koster FT, Peters CJ, Simpson GL, Tempest B, Zaki SR, Ksiazek TG, Rollin PE, Nichol S, Umland ET, et al. Hantavirus pulmonary syndrome: A clinical description of 17 patients with a newly recognized disease. The Hantavirus Study Group, N Engl J Med 1994 Apr 7; 330 (14):949-55.
5. Murphy FA. New, emerging, and reemerging infectious diseases. Adv Virus Res 1994; 43:1-52.

Japan

1. Morita K, Tanaka M, Igarashi A. Rapid identification of dengue virus serotypes by using polymerase chain reaction. J Clin Microbiol 1991; 29:2107-10.

2. Ogata A, Nagashima K, Hall W, Ichikawa M, Kimura-Kuroda J, Yasui K. Japanese encephalitis virus neurotropism is dependent on the degree of neuronal maturity. J Virol 1991; 65:880-6.
3. Morimoto K, Ni Y, Kawai A. Syncytium formation is induced in the murine neuroblastoma cell cultures that produce pathogenic type G proteins of the rabies virus. Virology 1992; 189:203-16.
4. Numaa K, Nakata S, Jiang X, Estes MK, Chiba S. Epidemiological study of Norwalk virus infections in Japan and Southeast Asia by enzyme-linked immunosorbent assays with Norwalk virus capsid protein produced by the baculovirus expression system. J Clin Microbiol 1994; 32:121-6.
5. Isegawa Y, Nakagomi O, Bruessow H, Minamoto N, Nakagomi T, Ueda S. A unique VP4 gene allele carried by an unusual bovine rotavirus strain 993/83. Virology 1994; 98:366-9.