Neuropathology of S. Paulo south coast epidemic encephalitis (Rocio flavivurus)

The neuropathology of 8 cases of S. Paulo south coast epidemic encephalitis (Rocio flavivirus), a new arbo B virus encephalitis, is described. The topographic pattern of the lesions appears to be almost specific. The gray matter is predominantly affected. Interstitial mononuclear infiltration, microglial proliferation and perivascular lymphocytic cuffing were seen. Neuronophagia was seldom seen except during the acute phases of the disease. Throughout the neuraxis, the gray matter was affected to a greater degree than white matter. The more damaged structures, in descending order, were as follows: thalamus, dentate nucleus, substantia inominata, brain stem, spinal cord and basal nuclei. Most of the cases exhibited thalamic inflammatory necrosis. Electron microscopy disclosed in one case virus-like particles, resembling those described in other arbo B viruses in the cytoplasm of thalamic neurons. In this case, virus was isolated from the brain and an immunofluorescence test also showed antigenic material in the thalamic neurons.

A hamster-attenuated, temperature-sensitive mutant of Venezuelan encephalitis virus

Pathogenicities of 10 temperature-sensitive mutants of Venezuelan encephalitis virus were studied using the hamster model of human virulence. The parental strain and nine of the temperature-sensitive mutants produced lethal infections in hamsters. Strain ts 126 showed reduced hamster virulence. Deaths with the lethal mutants usually occurred 1 to 3 days later than with parental virus. Nine mutants produced lower levels of viremia than parental virus. Attenuation of ts 126 was related to restriction of viral growth in spleen and probably bone marrow and to absence of the usual pathological lesions in hemopoietic tissues and brain, but was functionally unrelated to temperature sensitivity since temperatures of both normal and infected hamsters remained within the permissive range of the mutant. Deaths did not correlate with titers of the 10 mutants in blood at permissive temperatures or with reversions of four temperature-sensitive mutants to non-temperature-sensitive virus in hamsters.

[Cellular fusion induced in vitro by the mouse scrapie agent]

A method is described to demonstrate and measure the cell-fusion in vitro induced by viruses. This technique has been established using Sendai virus. It has been used to study the fusing ability of the Scrapie agent which is responsible of a slowly progressing spongiform encephalopathy in Mice. In Vero cells, the Scrapie agent induces a fusion which appears slowly and remains moderate. This test can help to detect the human spongiform encephalopathies.

Herpes simplex retinitis

Fatal encephalitis with accompanying retinitis developed in a previously healthy 18-month-old infant. Clinically the disease appeared as whitish-yellow punctate lesions, perivascular cuffing, and hemorrhage. The antibody titer to herpes simplex rose from 1:8 on the day of admission to 1:256 on the day of death. Postmortem, intranuclear inclusion bodies that were typical of those found with herpesvirus were seen in the brain and retina. Viral particles consistent with those of herpesvirus were found by electron microscopy in the brain and in the inner-nuclear and ganglion-nerve fiber layers of the retina. This demonstrates the direct infectious nature of herpetic retinitis. Hematogenous spread of the virus to the retina is presumed.

Vascular and neuroglial changes in experimental herpes simplex encephalitis enzyme histochemical study

An enzyme histochemical study of experimental herpes simplex encephalitis of the mouse has revealed a decrease in the number of capillaries displaying alkaline phosphatase activity. Glial cells showed increased Inosine 5 diphosphatase and ATPase activity. These enzyme histochemical changes were distributed throughout the nervous parenchyma while the lesions, seen by light microscopy, are localized to well defined areas. Mice inoculated with a pure culture of irradiated HSV failed to show the above mentioned modifications.

[Sulphated glycosaminoglycans as virus inhibitors. 3rd communication: therapy of viral diseases by means of glycoasaminoglycanpolysulphates. Establishment of fundamentals in experiments with laboratory animals (author's transl)]

Following the in vitro and in vivo demonstration of their inhibitory effect upon 17 D yellow fever virus (Comm. I and II) it has been tried to demonstrate the therapeutic effect of three GAGPS (L1, L5, L8)1 in experimental animals. It had been found that L1 possessed the strongest inhibitory action and L5 the lowest toxicity. L8 served as control substance with different chemical structure. Mice that had been intracerebrally infected with 50 to 100 LD50 yellow fever virus were subsequently treated with L1, L5 and L8 by i.v., i.p., i.m., and oral routes. At first it was found by cytophotometric measurements that the i.c. applicated substances accumulated in the nerve cells of the hippocampus major, the cerebellum (Purkinje cells) and the cortex; the uptake was nearly doubled if a mixture with virus was used (Table 1). Following preliminary experiments to determine the adequate quantity of virus, five experiments were performed in the order mentioned. In the first series were treated groups of 30 animals after intracerebral infection with 100 mug/0.02 ml L1 by the i.m. and i.p. routes respectively, beginning from the first day p.i. for a period of seven days (Table 2). A certain difference of the rate of deaths and surfivals was seen between the treated and untreated groups. Among the treated mice delayed death was a prominent occurrence (Fig. 1). A second experiment involving a double dose of L1a (200 mug/0.02 ml) from another batch of GAGPS showed no better effect (Table 3). An explanation was given by the fact that L1a demonstrated a moderate toxicity with high doses about 5000 mug/ml in the i.c. control (Table 4 and 5). A graphic representation of both experiments can be found in Figs. 2a and 2b. The relative low virus input in the third series as shown in the virus control impedes additionly clearcut results. In the fourth experiment the infected mice were treated with GAGPS doses between 250 and 2500 mug/ml; L1 was administered by the oral, L5 and L8 by the intraveneous route. The death rate of the animals treated with low doses of L1 (250-1000 mug/ml) is diminished clearly and there was a significant difference between treated and untreated mice when L5 and L8 were applied (Table 6). Fig. 3 shows the graphic representation of experiment four. The good results of treatment were confirmed by histopathological findings (Table 7). There was a clear difference in the kind and quantal distribution of cerebral lesions in treated and untreated mice. In the last series L1 was administered by the i.v., L5 and L8 by the oral route (Table 8). Although the virus dose given in this series was rather low a protective effect was seen with low doses of L1 (312 mug/ml) and L5 )500 and 1000 mug/ml). Also these results were confirmed by histopathological examination. In summary, the GAGPS L1, L5 and L8 were found to have a clear therapeutic effect upon the experimental encephalitis of mice caused by infection with 17 D yellow fever virus, in the case of experiment four with statistical significance.