Subhkij Angsubhakorn

DENGUE-3 (16562) PGMK 33 VACCINE : NEUROVIRULENCE, VIREMIA AND IMMUNE RESPONSES IN MACACA FASCICULARIS

Investigation of monkey neurovirulence of dengue-3 viruses (DEN-3, 16562) was undertaken to provide an evaluation of the relative safety of virus strain attenuated for potential use of live virus vaccine. Ten flavivirus-negative, cynomolgus monkeys (Macacafascicularis) were used in the test. The animals were inoculated intrathalamically, intraspinally and intramuscularly with DEN-3 PGMK 33 attenuated live virus vaccine (6 monkeys): parent virus (2) and control cell culture fluid (2). Blood samples were collected on days 0, 1, 2, 4, 6, 8, 10, 12 and 21 for virus isolation and days 0 and 21 or 22 for serologic testing. One monkey with DEN-3 (16562) PGMK 33 candidate vaccine had detectable viremia on day 10. By day 21, all recipients of PGMK 33 and both monkeys with DEN-3 parent virus developed serum neutralizing antibodies to DEN-3 titers ranged from 56-320. The monkeys showed no evidence of illness and none died of dengue infection. Histopathological examination of tissue collected on day 21 or 22 revealed only minimal neurovirulence lesions as scored by the routine grading system. No differences were observed between the DEN-3 parent and vaccine viruses and it is concluded that neither virus is neurovirulent for cynomolgus monkeys.

Langerhans cell density and serological changes following intradermal immunisation of mice with dengue 2 virus

After the introduction of the dengue-2 (16681) virus by intradermal (i.d.) injection into the footpads of mice, Langerhans cells (LCs) increased in numbers within 24 h at the site of injection and neutralising antibody developed. On comparing the i.d. and intramuscular (i.m.) routes, antibody was produced more rapidly and at higher levels when the virus was injected by the i.d. route. Subsequent re-challenge by the i.d. route produced an even more rapid serological response with all mice producing significant neutralising titres within 12 h. Numbers of ATPase-positive LCs varied with time. A significant sharp drop in LC densities in the early post-injection phase directly correlated with the increased numbers of dendritic cells in the superficial dermis and interfollicular sinuses of draining lymph nodes (LN). Immunofluorescence showed the presence of viral antigen in the footpad epidermis and draining LN within minutes or within 2 h of challenge, respectively.

Dengue-4 vaccine: Neurovirulence, viraemia and immune responses in rhesus and cynomolgus monkeys

A dengue 4 (DEN-4, strain 1036-PDK 48) vaccine attenuated by passage in primary dog kidney cells was tested using rhesus (Macaca mulatta) and cynomolgus (M. fascicularis) monkeys to determine its safety, potency, and immunogenicity. 14 rhesus monkeys were divided into 3 groups: group 1, 2 animals given control culture fluid; group 2, 2 animals given DEN-4 parental virus; group 3, 10 animals given DEN-4 vaccine virus. 10 cynomolgus were similarly grouped, but group 3 contained 6 monkeys. No significant neurovirulence was observed with parental or with DEN-4 virus passaged in primary dog kidney (PDK) cells. Both cynomolgus monkeys inoculated with DEN-4 vaccine virus developed minimal (V-1) and mild (V-2) neurovirulence-type lesions in the central nervous system, which were nondestructive in both species. All parental and vaccine viruses produced moderate to high neutralizing antibody titres. Only parental virus produced viraemia, in 2 cynomolgus monkeys. Because of its safety and avirulence in monkeys, PDK 48 is recommended for human trial.

Neurovirulence detection of dengue virus using rhesus and cynomolgus monkeys

The results of a comparative study of neurovirulence of dengue type 1 virus in two species of Old World monkeys, viz. rhesus monkeys (Macaca mulatta) and cynomolgus monkeys (Macaca fascicularis) are reported. In the present study, parental dengue type 1 (16007) and its vaccine viruses were tested by intrathalamic, intramuscular and intraspinal injections in these two species of monkey. Both species of monkeys inoculated with parental dengue type 1 virus developed neurovirulence-type lesions which were graded as minimal (V-1) and occasionally mild (V-2, in cynomolgus monkeys) in severity. The antibody response to either parental or vaccine virus was slightly less in rhesus monkeys than in cynomolgus inoculated with these strains. This comparative study possibly establishes the cynomolgus monkey as a suitable test model to replace the rhesus monkey for neurovirulence testing of dengue-1 vaccine intended for use in humans.

Enhancing effects of rodent malaria on aflatoxin B1-induced hepatic neoplasia.

SummaryThe interaction between aflatoxin and malaria was tested for its usefulness as a model for hepatic tumor induction in rats. Male Buffalo rats which received aflatoxin B1 (AFB1) followed by Plasmodium berghei infection developed more preneoplastic lesions in the liver compared to those given AFB1 alone. No preneoplastic lesions were found in the liver of control and malarial-treated animals. These findings suggest that the malarial parasite facilitates liver tumor development initiated by AFB1 in rats.

Alpha benzene hexachloride inhibition of aflatoxin B1-induced hepatocellular carcinoma. A preliminary report

Alpha benzene hexachloride protected against the development of liver carcinoma in male albino Fisher rats ingesting aflatoxin B1.

MORPHOLOGY OF EXPERIMENTAL CHORIONIC TUMORS IN RATS

Four additional chorionic tumors have been obtained by the same method as previously reported1 using 4‐NQO and 7,12‐DMBA as carcinogens. It was observed that high dosage of DMBA was quite effective in inducing chorionic tumors in rats. Gross and histological appearance of the tumor resembled that of normal placenta in rats. Part of the tumor has been transplanted and is now under observation.

Production of aflatoxins and other fluorescent metabolites by strains of aspergillus flavus isolated from staple foods and their toxicity to rats

Abstract Forty strains of Aspergillus flavus isolated from food marketed in Thailand between 1967 and 1969 were re-isolated for toxicological characterization. Approximately 92% produced aflatoxin B 1 or aflatoxins B 1 and B 2 . In acute toxicity tests in weanling male Wistar rats, 87·5% of the orally intubated chloroform extracts (CEX) of the isolates caused at least one death in test groups of five rats, compared with 38% of the ip-administered petroleum ether-insoluble (PEI) fractions. Twenty-four unidentified compounds were produced in varying amounts by eighteen strains of A. flavus . These compounds, detected as blue and green fluorescent spots on thin-layer chromatograms, may have modified the toxic effect of the aflatoxins. The histopathological changes caused by the CEX and PEI fractions were similar, the main ones being haemorrhagic necrosis of the liver and kidney, congestion of pulmonary vessels and hypercellularity of the alveolar septa of the lung, hydropic degeneration of the cardiac muscle and lymphocytic depletion of the spleen.