Sindbis virus-induced ocular immunopathology

The intraocular injection of the Sindbis virus in adult BALB/c mice produces a uveoretinitis with little or no central nervous system involvement. Ocular disease starts on the third day after infection and presents as a mild to moderate iridocyclitis and retinitis, usually accompanied by typical severe dysplastic changes of the retina. The inflammatory infiltrate consists almost exclusively of lymphocytes and histiocytes. Immunosuppression of the mouse with cyclophosphamide on the day after infection markedly reduces or eliminates completely the inflammatory response, suggesting that the virus itself is not cytopathogenic. In the normal host, the virus replicates within the eye for several days but is then completely eliminated by day 8 after infection. In the immunosuppressed animal, virus titers reach greater levels than in the normal animal and then fall, in step with the developing inflammatory response. It would appear that the immunologic mechanisms responsible for clearance of the viral infection from the eye also mediate the ocular disease.

Entry of rabies virus into the peripheral nerves of mice

Young adult mice were inoculated in the hind limb with rabies virus or Sindbis virus. Rabies 1820B virus antigen was detected in leg sections by immuno-fluorescence at 1 h post-inoculation at sites comparable in form and distribution to cholinesterase-positive sites, which represent motor end-plates (MEPs). Sites which were rabies virus antigen-positive by immunofluorescence were also cholinesterase- positive on double-stained slides. Rabies CVS virus detected by autoradiography was similarly distributed at 6 h post-inoculation. Uptake of rabies virus at motor nerve endings was confirmed by the detection of rabies antigen by immunofluorescence in ventral horn cells in the spinal cord at 20 h post-inoculation before involvement of dorsal root ganglia. Rabies virus antigen could not be detected at MEPs if the virus had been inactivated by beta propiolactone or mixed with antibody prior to injection or if the sciatic nerve had been cut 7 days earlier, similarly treated groups of mice survived for the observation period of 6 weeks. Rabies virus antigen was found at MEPs in mice given antibody 24 h before virus injection, but virus antigen was not found in the spinal cord, and mice similarly treated survived. Sindbis virus strain Ar86, which like rabies virus is neurotropic in adult mice, was also found at MEPs and in peripheral nerves by autoradiography at 6 h post-inoculation. In contrast to results with rabies virus-infected mice, stimulation of the sciatic nerve for the first hour post-inoculation prevented mortality. Sindbis virus strain Ar339, which is not neurotropic in adult mice, could not be detected at MEP's by immunofluorescence or autoradiography and mice injected with virus survived. The results presented here suggest that rabies virus and perhaps other neurotropic viruses can use the motor axon terminal at the neuromuscular junction as a site of entry into the nervous system.

Japanese encephalitis virus surveillance in the Taipei area, Taiwan in 1978

Attempts were made to isolate Japanese encephalitis virus from mosquitoes collected with three light traps operated twice a week at three sentinel pigpens in the Taipei area from May to Oct. 1978. A total of 6,549 mosquitoes trapped alive were processed in 283 pools. Suspensions were inoculated into Aedes albopictus cell cultures and into suckling mice. A total of 19 JE virus isolates were made; 12 from pools of Cx. tritaeniorhynchus, 6 from Cx. annulus and one from Cx. quinquefaciatus. Sindbis virus was isolated for the first time in Taiwan from a pool of Cx. tritaeniorhynchus. More isolates were made from mosquito cell cultures (20) than by mouse inoculation (6). Positive isolations of JE virus by mouse inoculation were all from the mosquitoes obtained during an 11 day period from 20 to 30 June 1978 when all six sentinel pigs were viremic. This study shows the decided advantage of the use of mosquito-cell cultures over that of mice.

Reversible inhibition of Sindbis virus penetration in hypertonic medium

Under hypertonic conditions, the penetration of baby hamster kidney cells by Sindbis virus was inhibited. Virus became cell associated, but remained susceptible to neutralization by specific antiserum and to removal by elution. When cells were returned to isotonicity, inhibition was reversed.

[Persistence of Sindbis virus in cultures either non-producing or irregularly producing oncornavirus]

Persistence of Sindbis virus (SV) was studied for 9 months in two lines of mouse cell cultures (BALB/C) in one of which the genome of endogenous ecotropic oncornaviruses was repressed. The other lines was exogenously infected at the level of plimary culture with Rauscher leukemia virus (RLV) and SV and showed gradual inhibition of oncornavirus functions. The presence of oncornavirus type C was not the necessary condition for the development of persistent SV infection, however it influenced the character of persistence. In both systems, sequential loss of the hemagglutinating and interferon-inducing activities, then infectivity of SV (61--82 days), and persistence of the noninfectious antigen of the arbovirus for 9 months were observed. The differences consisted in the time of appearance of homologous interference to SV: in the presence of oncornavirus earlier (40 days), under conditions of repressed oncornavirus genome later (179 days). Electron microscopic examinations showed that in the system infected with RLV and SV there occurred in the course of persistence a sharp activation of phagosome-lysosome complex accompanied by incorporation into phagocytolysomes of numerous intact and partially destroyed virions of SV and RLV and their release from cell with cytoplasmic fragments. Possible mechanisms of inhibition of functions of the oncogenic and infectious viruses in the reported model of mixed chronic infection are discussed.

Role of extracellular virus on the maintenance of the persistent infection induced in Aedes albopictus (mosquito) cells by Sindbis virus

Sindbis virus infection of cultured mosquito cells was found to have no effect on the growth of these cells; instead, a persistent infection of the culture followed an initial acute phase of rapid virus synthesis. Nearly all of the cells in the acute stage of infection were found to actively release virus in an infectious-center assay and to contain significant amounts of virus antigen as determined by immunofluorescence. Cells in the persistent phase of infection released few virions into the media, and only a small percentage of the cultured cells could be demonstrated to contain detectable amounts of virus antigen by immunofluorescence assay. In spite of the fact that nearly 100% of the cells in the persistent phase of infection were found to be virus negative by the two assays described above, the culture as a whole totally excluded the expression of superinfecting virus, as did cells in the acute phase, suggesting that most of the persistently infected cells did, indeed, contain virus information. Prevention of reinfection of the cells in the persistent phase by eliminating extracellular virus resulted in a curing of the culture such that it responded to infection by added virus much as would an uninfected culture.

Isolation of Sindbis (alphavirus) and Leanyer viruses from mosquitoes collected in the Northern Territory of Australia, 1974

Mosquitoes collected near Darwin, Northern Territory, in 1974 yielded two virus strains. One was identified as Sindbis virus, not previously isolated from the Northern Territory. The other is antigenically distinct from viruses previously isolated from arthropods in Australia, and the name "Leanyer" is proposed for it. Its properties suggest that it may be a togavirus serologically unrelated to available alphaviruses and flaviviruses.

Variables affecting viral plaque formation in microculture plaque assays using homologous antibody in a liquid overlay

A liquid antibody microculture plaque assay and the variables that govern its effectiveness are described. The assay is based on the principle that low concentrations of homologous antibody can inhibit secondary plaque formation without inhibiting formation of primary plaques. Thus, clear plaques that followed a linear dose response were produced. The assay was found to be more rapid, less cumbersome, and less expensive than assays using agar overlays and larger tissue culture plates. It was reproducible, quantitative, and had about the same sensitivity as the agar overlay technique in measuring infectious coxsackievirus type B-3. It was more sensitive in assaying adenovirus type 3 and Western equine encephalomyelitis, vesicular stomatitis, Semliki forest, Sendai, Sindbis, and Newcastle disease viruses than were liquid, carboxymethylcellulose, and methylcellulose microculture plaque assays. The variables influencing sensitivity and accuracy, as determined by using coxsackievirus type B-3, were: (i) the inoculum volume of virus; (ii) the incubation period of virus; and (iii) the incubation temperature.

[Stability in drinking and surface water of nine virus species from different genera (author's transl)]

The stability of nine viruses, Aujeszky, Sindbis, Vesicular Stomatitis, Newcastle Disease, Vaccinia, FMD, HCC, Reo and Teschen virus in drinking and surface water was investigated comparatively at temperatures of 9 and 15 degrees C as well as the influence of water factors like seasonal difference in temperature, pH value, hardness and sort of water. The results can be summarized as follows: 1. At temperatures of 9 to 15 degrees C the majority of the viruses remained stabil in natural water for an astonishing long time. 2. Starting with virus concentration of about 10(4) infectious units per ml Teschen, Vaccinia, Reo, HCC and ND virus could mostly be demonstrated in water longer than 200 days and FMD, Aujeszky, Vesicular Stomatitis and Sindbis virus for 20 to 50 days on average at 9 degrees C. The stability of the viruses investigated decreased in water in the named turn. 3. Based on these results it can be assumed that under natural conditions with very low virus content of some particles the labile viruses such as Toga, Herpes, Rhabdo and pH labile Picorna remain infectious in water for some days. They should not have any importance as water contaminants. More resistant viruses like Paramyxo may keep infectious for weeks and very stabile viruses such as Entero, Reo, Adeno and Pox viruses several weeks to months. 4. As to factors temperature, pH, hardness and sort of water-within the naturally differing range-only the temperature and only in the case of less resistant viruses showed significant influence on the virus stability in water.

[Comparative studies of two alphavirus by macroplaque assays and by a fluorescent focus method in Vero cell lines (author's transl)]

Immune anti-Sindbis and anti-Chikungunya ascitic fluids have been titrated by the classic way of plaque reduction and by a quick fluorescent focus method using an indirect staining. The results are comparable, allowing to consider the use of this quick and inexpensive technic for counting-assays by neutralization.

Role of the immune response in age-dependent resistance of mice to encephalitis due to Sindbis virus

One- to eight-week-old mice were studied after subcutaneous inoculation of Sindbis virus. Local replication at the site of inoculation, transient viremia, and invasion of the brain were found in mice of all ages, although the quantities of virus were greater in younger mice. Death occurred in 100% of one-week-old mice, 28% of two-week-old mice, and none of the mice four weeks old or older. Pathologic examination of the brains on day 7 after infection revealed a mononuclear inflammatory infiltrate in all mice, with evidence of necrosis in the youngest. Neutralizing antibody was present by day 3 and reached high titers by day 6 in all age groups. Specific stimulation of cells from the draining lymph node by Sindbis virus antigen was also demonstrable by day 6 in all groups. There was no evidence for a primary role of humoral or cellular immune responses in the age-dependent resistance of mice to infection with Sindbis virus.

In vivo behavior of a Sindbis virus mutant isolated from persistently infected Aedes aegypti cell cultures

A mutant of the Sindbis virus SV-S was found to interfere with the regular course of infection by the wild strain of the virus SV-W in A. aegypti mosquitoes and in suckling mice. In mosquitoes, this result was manifested by a reduced titer of SV-W in the presence of SV-S and by a failure of the mosquitoes to transmit SV-W. In the brains of suckling mice, in the presence of SV-S, the growth of sc inoculated SV-W was suppressed, and as a result, the usually lethal course of infection by this virus was converted into a nonlethal one.

[The absence of Sindbis virus from French Polynesia]

The authors report, in French Polynesia that Sindbis antigen is a good control for rubella serodiagnosis. Data are presented on Hemagglutination Inhibition from 2,032 sera, showing no evidence of any Sindbis antigen circulation.

Isolation of a Sindbis virus variant by passage on mouse plasmacytoma cells

A variant of Sindbis virus has been isolated by growing a stock of virus, previously passaged on chicken embryo cells, in mouse plasmacytoma (MOPC 315) cells in suspension culture. An indirect immunofluorescence test and infective center assay showed that only a small fraction of cells could be infected by the stock wild-type virus, but that the population of virus accumulating after a few passages on the mouse cells had host-range properties distinct from the stock virus. The mouse-passaged virus retained its virulence for the original host and back-passaging of this virus on chicken cells did not change its newly acquired properties. Thus, this variant appears to be a genetically distinct form of Sindbis that adsorbs to and grows much better than the stock virus on several types of mouse cells including cultures of mouse macrophages.

Arbovirus infections in Sarawak, October 1968--February 1970 Tembusu and Sindbis virus isolations from mosquitoes

Thirty isolations of Tembusu virus and four of Sindbis virus were obtained from approximately 280 000 mosquitoes collected between October 1968 and February 1970 in Sarawak, particularly from K. Tijirak, a Land Dyak village 19 miles South of Kuching. Twenty-two isolations of Tembusu virus and two of Sindbis virus were from Culex tritaeniorhynchus; two of Tembusu virus and two of Sindbis virus came from Culex gelidus. Tembusu virus was active throughout the year at K. Tijirak, the highest infection rates in C. tritaeniorhynchus being in January-March and May-August, when the C. tritaeniorhynchus population was declining and ageing. These results confirm that C. tritaeniorhynchus is the principal arthopod host of Tembusu virus in Sarawak. Antibody studies suggest that birds, particularly domestic fowl, are probably vertebrate maintenance hosts of Tembusu and Sindbis viruses in Sarawak.

Hemagglutination-inhibition: rapid assay for neuraminic acid-containing viruses

Influenza virus particles bind rapidly to vesicular stomatitis, Sindbis, or Rauscher murine leukemia virus particles, forming mixed aggregates demonstrable by electron microscopy. The normal hemagglutinating property of influenza virus is inhibited by these viruses, providing a rapid quantitative assay. Prior treatment with neuraminidase blocks the ability of other viruses to inhibit influenza virus hemagglutination.