[Experimental study of rabies virus (Vnukovo-32 strain) persistence in white mice]

The duration of detection of the specific antigen in the cells of the central nervous system (CNS) of mice extraneurally infected with 450, 560 and 4380 LD50 of rabies virus, the Vnukovo-32 strain was studied. The antigen in the CNS cells was detected by the fluorescent antibody technique from the 11th until the 52nd day postinoculation, at 16-34 days being found in 50 to 100% of the experimental animals. In parallel, virus-neutralizing antibody was determined in the blood serum of the infected mice, and their brains were examined for the presence of rabies virus by bioassays. In most cases, serological results correlated with the antigen detection in the brain tissue. At 18, 29 and 34 days rabies virus was isolated from clinically normal mice inoculated subcutaneously, which by all the tests used did not differ from the other experimental animals. The results of the experiments attest to the possibility of rabies virus, the Vnukovo-32 strain, persistence in mice.

Oral rabies vaccine: evaluation of its infectivity in three species of rodents

The safety of oral rabies vaccine was evaluated in 3 species of rodents, animals which might inadvertently consume field-distributed vaccine baits intended for foxes. The potentials for infection from bait ingestion and transmission through cannibalism were evaluated. Results indicate that ingestion of the vaccine baits used in these experiments will result in infection and disease of some rodents. Of 64 rodents which ate baits, 19 (30%) died of clinical rabies; the diagnosis was confirmed in 11 (17%), and 2 (3%) had demonstrable rabies virus in their salivary glands. Only 3 of 112 (3%) rodents that ate vaccine-infected rodents contracted rabies, and none had demonstrable virus in their salivary glands.

Temperature-sensitive mutants of rabies virus in mice: a mutant (ts2) revertant mixture selectively pathogenic by the peripheral route of inoculation

Analysis of the pathogenic potential in mice of a variety of rabies and rabies serogroup viruses revealed that an apparently revertant population of virus derived from CVS mutant ts 2 had a unique capacity to selectively induce paralytic disease when given by a peripheral [intraplantar (i.pl.)] route of inoculation. Little paralytic disease was induced by high concentrations of virus administered by the intracerebral (i.c.) route, whereas paralytic disease and death were characteristically induced in mice given only a few infectious doses of virus i.c. Disease induced by i.pl. inoculation was dose dependent. Mice frequently survived paralytic disease induced by i. pl. inoculation, with clinical signs often persisting indefinitely; mice surviving i.c. inoculation of high concentrations of virus frequently exhibited chronic nonspecific signs of minor debility. Analysis of the ts 2 virus population indicated that it was composed of a mixture of ts and revertant virions, each with characteristic pathogenic (or nonpatholgnic) propensities, none of which was identical to the original composite ts 2 virus populations. Despite the heterogeneity of the ts 2 virus population, the typical pathogenic pattern of selective pathogenic capicity after i. pl. inoculation at high doses was retained during 11 ocnsecutive passages in suckling mouse brain. ts 2 virus was demonstrated to interfere with the disease-producing capacity of CVS fixed rabies virus when ts 2-CVS mixtures were inoculated i.c. However, attempts to demonstrate a particular propensity for induction in vitro of "autointerference" by ts 2 in serial passage in BHK-21 cell culture inoculated at high multiplicity were unsuccessful.

"Paramyxovirus-like" intranuclear inclusions occurring in the nervous system in diverse unrelated conditions

Filamentous intranuclear inclusions similar to the "paramyxovirus-like" intranuclear inclusions described in active multiple sclerosis (MS) were observed incidentally in four patients who had diverse disorders such as rabies, mannosidosis, metachromatic leukodystrophy, cerebral aneurysm and ischemic infarcts. The observation is in support of the mounting evidence that the "virus-like" intranuclear inclusions are not specific for MS and may occur frequently in a variety of diverse conditions. Moreover, neither virological nor immunological evidence as to the viral nature of the intranuclear inclusions has been presented to date, and the intranuclear inclusions have been observed mostly in degenerating or autolyzed cells in biopsied or autopsied tissue samples. In view of all the circumstantial evidence, it is suggested that the intranuclear "paramyxovirus-like" inclusions may represent an alternation of nuclear chromatin common to antemortem degeneration and postmortem autolysis in a variety of cells, the nature of which remains to be elucidated.

[Detection of Babes-Negri bodies in blood erythrocytes of rabid white mice]

Large numbers of polymorphous dense Babes-Negri bodies were found in brain neurons of mice sick with street rabies and dying of it. Among blood cells filling the cerebral vessels of mice dead from rabies, erythrocytes containing small dense inclusions, Babes-Negri bodies, could be seen clearly.

Cell to cell transmission of virus in the central nervous system. II. Experimental rabies in mouse

Rabies virus replication in suckling and adult mouse brains inoculated with either fixed or street virus was studied by light and electron microscopy. Chronologic study of fixed virus-infected suckling mice showed that virus budded from the plasma membrane of neuronal cell processes and perikarya prior to the development of intracytoplasmic virus particles. Nucleocapsids and virions were observed exclusively in perikarya and cellular processes of neuronal cells and, on rare exception in an astrocyte indicating high neurotropism of rabies virus regardless of the strain of virus and the age of host animal. Virus transit between contiguous neuronal cell processes and perikarya was observed in suckling and adult mouse brain after both street virus and fixed virus infection. Nucleocapsids and virions were also found in myelinated axons in addition to the unmyelinated neuronal cell processes. The implication of cell to cell spread of virus within the central nervous system in rabies virus infection is discussed.

A local outbreak of paralytic rabies in Surinam children

A rapidly fatal encephalomyelitis, which was in most cases characterized by ascending paralysis, developed in seven children of the age of 3 to 10 years in a bushnegro village in the interior of Surinam. Rabies virus was recovered from the central nervous system of three autopsied children. Although the source of infection has not been detected, there is an indication that, at least in some cases, the disease has been transmitted by rat-bite rather than by vampire bats. During the same period a few cases of minor febrile illness occurred in the same community. Since virological and serological evidence of a wide-spread distribution of Coxsackie A virus type 4 was obtained, the latter illness may presumably be attributed to this virus.

Immunogenicity and acceptability of a human diploid-cell culture rabies vaccine in volunteers

A rabies vaccine, prepared in human diploid-cell culture, was given intradermally (i.d.) or intramuscularly (i.m.) to 35 volumteers who had not previously received prophylactic immunisation. Rabies neutralising antibody titres rose sharply after the first dose, and 4 weeks after the second dose all titres were above 1/80 (1-7 i.u. per ml.). Immunisation via the i.d. and i.m. routes was equally successful in terms of likely immune status, but the i.d. rate was associated with many more local sideeffects.

The diagnosis of rabies in a horse by brain neutralization test

A horse showing clinical signs of a neurological disorder was killed and various diagnostic tests for rabies were carried out. Histopathlogy revealed a nonsuppurative encephalitis. Fluorescent antibody test and mouse inoculation test were negative. A positive diagnosis of rabies was based on a high antibody titer (1:10,000) to rabies virus in brain tissue.

Antibody production in milk serum after virus instillation of goat mammary gland VI. "Sham infection" with special reference to rabies

The ERA strain of rabies vaccine virus failed to propagate or cause clinical manifestations when instilled into the mammary gland of lactating goats. However, the virus did produce neutralizing antibodies in this gland as a result of repetitive viral stimulation, a "sham infection". The protective property of the concentrated and partly purified milk serum antibody was assessed in mice. In the first trial, protective activity was observed when a single dose of milk serum antibody was administered at intervals up to three days after exposure to virulent rabies virus. In the second trial, using a more concentrated milk serum antibody, about half of the mice were protected when the milk serum was administered up to ten days after exposure to virulent virus.

Rabies virus in nasal mucosa of naturally infected bats

Rabies virus was demonstrated in the olfactory mucosa of naturally infected bats by staining with fluorescent antibody and by isolation of the virus from the nasal tissues. The olfactory mucosa is a potential portal of entry and exit for airborne rabies virus in bat caves.