The pathogenesis of hepatitis A virus (HAV) infection was studied in owl monkeys following oral administration of the wild-type HM-175 strain of HAV. Stools were collected daily and blood and pharyngeal swabs twice weekly for viral isolation, and animals were necropsied at various intervals after inoculation. Organs were examined for the presence of virus by isolation in cell culture and for viral antigens by immunofluorescence. Monkeys excreted HAV in the stools for 1-4 days after inoculation, presumably due to the residual unabsorbed inoculum. No virus was found in stools for the next 2-3 days. HAV re-appeared on days 4-7 and then persisted through day 39. Viremia occurred on the 10th day and continued until day 35. Virus was isolated occasionally from throat swabs 1 or 2 weeks after it was detected in stools and blood, and there was no evidence that HAV replicated in the pharyngeal tissues. Animals acquired anti-HAV antibody by the 4th week, and alanine aminotransferase (ALT) was elevated 5-5.5 weeks after inoculation. HAV was isolated from liver 5 days after inoculation; however, viral antigens were first detected in Kupffer cells of the liver at 14 days and in hepatocytes at 21 days. HAV antigen was detected in epithelial cells of the intestinal crypts and in the cells of the lamina propria of the small intestine 3 days postinoculation and thereafter until the 5th week, suggesting that these cells might represent an additional site of HAV replication.

Abstract. Twelve rhesus macaques (Macaca mulatta) challenged intranasally with a wild-type Japanese encephalitis virus (JEV) developed clinical signs 11-14 days later. Tissues from the cerebral cortex, cerebellum, brainstem, thalamus, meninges, and all levels of the spinal cord were stained for JEV antigen with hyperimmune mouse ascitic fluid and streptavidin-alkaline phosphatase; immunofluorescent staining was also done on frozen sections. Viral antigen was found in all cell layers of the cerebellum, the gray matter of the thalamus and brainstem, and the ventral horn of all levels of the spinal cord. Staining was limited to neurons and their processes. Histopathologic changes were limited to the nervous system and characterized by nonsuppurative meningoencephalitis. These results were comparable with those of previous studies done with human autopsy tissues. Intranasal inoculation of rhesus monkeys with JEV was effective in producing clinical disease comparable with natural disease in humans and may serve as a model to evaluate protective efficacy of candidate JEV vaccines.Japanese encephalitis (JE), which is endemic to much of eastern and Southeast Asia, is the most common arthropodborne human encephalitis in the world, accounting for more than 35,000 cases and 10,000 deaths each year. 1 In endemic areas, the highest age-specific attack rates occur in children 3-6 years of age. Infection with JE virus (JEV) may be asymptomatic or manifest as a mild febrile illness, aseptic meningitis, or classic severe meningomyeloencephalitis. The case fatality rate is approximately 25%, with 50% having neuropsychiatric sequelae and 25% recovering fully. 2,3 Longterm sequelae in survivors include weakness, ataxia, tremors, athetoid movements, paralysis, memory loss, and abnormal emotional behavior. 4,5 The principle vector for JEV in Thailand is the mosquito Culex tritaeniorhynchus, which is difficult to control.The current highly purified BIKEN (Research Foundation of Microbial Diseases

To confirm an earlier report that laboratory rats are susceptible to infection with the hepatitis E virus (HEV), we inoculated 27 Wistar rats intravenously with a suspension of a human stool known to contain infectious HEV. Stool, sera, and various tissues were collected from three rats each on days 0 (preinoculation) and 4, 7, 11, 14, 18, 21, 25, 28, and 35 postinoculation. Stool and sera specimens were examined by reverse transcription-polymerase chain reaction for the presence of HEV genomic sequences. Tissues were examined by light microscopy for detection of histopathological changes and by direct immunofluorescence for detection of HEV antigens. We detected HEV RNA in stools on day 7 in all three animals and in serum intermittently between days 4 and 35. We found HEV antigens in liver, peripheral blood mononuclear cells, spleen, mesenteric lymph nodes, and small intestine. We detected histopathology attributable to the inoculum in liver, spleen, and lymph nodes. The results confirm that HEV can replicate in laboratory rats and suggest new tissue sites for HEV replication.

Malaria poses a threat across several continents: Eurasia (Asia and parts of Eastern Europe), Africa, Central and South America. Bradley (1991) estimates human exposure at 2,073,000,000 with infection rates at 270,000,000, illnesses at 110,000,000, and deaths at 1,000,000. Significant mortality rates are attributed to infection by the parasite Plasmodium falciparum, with an estimated 90% among African children. A worldwide effort is ongoing to chemically and pharmacologically characterize a class of artemisinin compounds that might be promising antimalarial drugs. The U.S. Army is studying the efficacy and toxicity of several artemisinin semi-synthetic compounds: arteether, artemether, artelinic acid, and artesunate. The World Health Organization and the U.S. Army selected arteether for drug development and possible use in the emergency therapy of acute, severe malaria. Male Rhesus monkeys (Macaca mulatta) were administered different daily doses of arteether, or the vehicle alone (sesame oil), for a period of either 14 days, or 7 days. Neuropathological lesions were found in 14-day arteether treated monkeys in the precerebellar nuclei of the medulla oblongata, namely: (1) the lateral reticular nuclei (subnuclei magnocellularis, parvicellularis, and subtrigeminalis), (2) the paramedian reticular nuclei (subnuclei accessorius, dorsalis, and ventralis), and the perihypoglossal nuclei (n. intercalatus of Staderini, n. of Roller, n. prepositus hypoglossi). The data demonstrate that the simina meduallry precerebellar nuclei have a high degree of vulnerability when arteether is given for 14 days at dose levels between 8mg/kg per day and 24 mg/kg per day. The neurological consequences of this treatment regimen could profoundly impair posture, gait, and autonomic regulation, while eye movement disorders might also be anticipated.

Abstract. Placebo-controlled field efficacy trials of new Japanese encephalitis (JE) vaccines may be impractical. Therefore, an animal model to evaluate efficacy of candidate JE vaccines is sought. Previous work has shown that exposure of monkeys to JE virus (JEV) via the intranasal route results in encephalitis. Here we report the further development of this model and the availability of titered virus stocks to assess the protective efficacy of JE vaccines. To determine the effective dose of our JE challenge virus, dilutions of a stock JEV (KE-93 isolate) were inoculated into four groups of three rhesus monkeys. A dose-dependent response was observed and the 50% effective dose (ED 50 ) was determined to be 6.0 ϫ 10 7 plaque forming units (pfu). Among animals that developed encephalitis, clinical signs occurred 9-14 days postinoculation. Infection with JEV was confirmed by detection of JEV in nervous tissues and IgM to JEV in the cerebrospinal fluid. Viremia with JEV was also detected intermittently throughout infection. Validation of the model was performed using a known effective JE vaccine and saline control. One ED 90 of virus (2.0 ϫ 10 9 pfu) was used as a challenge dose. Four of four animals that received saline control developed encephalitis while one of four monkeys administered the JE vaccine did so. This study demonstrates that the virus strain, route of inoculation, dose, and the outcome measure (encephalitis) are suitable for assessment of protective efficacy of candidate JE vaccines.Japanese encephalitis (JE) is the leading cause of mosquito-borne viral encephalitis in the world, accounting for approximately 35,000 cases and 10,000 deaths each year in Asia. The JE virus (JEV) is transmitted by culicine mosquitoes through an epizootic cycle involving primarily pigs and birds. Most infections in humans are asymptomatic. It is estimated that only one in 20 to one in 1,000 infections result in encephalitis. However, once encephalitis occurs, it is fatal in 25% of the cases with 50% of the survivors experiencing neurologic sequelae. [1][2][3] Several JE vaccines are in use. Live attenuated vaccines have been developed and licensed for use only in China. [4][5][6] A more widely used vaccine is a highly purified formalininactivated virus preparation derived from infected mouse brain. In 1984In -1985, an efficacy trial was conducted in 65,224 Thai children using monovalent (Nakayama strain) and bivalent (Nakayama and Beijing strain) mouse brain vaccines manufactured by BIKEN (Research Foundation of