Terminal Dissemination of Rabies Virus in Selected Rat Tissues

Fifty rats were divided into 3 groups and challenged via the foot pad route with a fixed and 2 different strains of street rabies virus in order to study the dissemination of the virus and the affinity for certain tissues of the rat.

The incubation period for rats inoculated with fixed rabies is shorter than with street virus, being 5 to 7 days compared with 10 to 12 days.

Rats inoculated with the fixed strain were less aggressive and irritable than rats inoculated with street virus.

The fixed strain demonstrated a greater affinity for the tissues studied as compared to the street strains of virus.

Both the fixed and street strains revealed a low affinity for the parotid gland since no virus could be demonstrated in 14 of 20 in the fixed virus group and 27 of 30 in the street virus group.

     

Infection of Bergmann glia in the cerebellum of a skunk experimentally infected with street rabies virus.

Rabies virus is a highly neuronotropic virus and glial cell infection is not prominent in the central nervous system (CNS). Paraffin-embedded tissues from the cerebella of skunks experimentally infected with either a skunk salivary gland isolate of street rabies virus or the challenge virus standard (CVS) strain of fixed rabies virus were examined with immunoperoxidase staining for rabies virus antigen by using an anti-rabies virus nucleocapsid protein monoclonal antibody. A skunk infected with street rabies virus showed prominent infection of Bergmann glia. Although infected Purkinje cells were observed, they usually demonstrated a relatively small amount of antigen in their perikarya. A CVS-infected skunk showed many intensely labeled Purkinje cells and a relatively small number of infected Bergmann glia. These findings indicate that although rabies virus is a highly neuronotropic virus, street rabies virus strains do not always demonstrate strict neuronotropism in the central nervous system.     

三株广西狂犬病病毒NS基因和M基因的克隆与序列分析

本研究设计了一对特异性引物NSM1/NSM2,对三株广西狂犬病病毒NS和M基因同时进行了RT_PCR扩增、克隆和测序。同源性分析表明,三株广西野毒NS基因核苷酸同源性为87.2%~98.4%,M基因核苷酸同源性为90.1%~99.7%;与固定毒和狂犬病相关病毒比较,NS基因分别为79.9%~82.8%和69.7%~71.0%;M基因的分别为82.8%~87.8%和75.0%~77.8%。三株野毒NS基因氨基酸同源性为93.3%~98.7%,M基因氨基酸同源性分别为97.5%~100%。表明广西各地毒株之间亲缘关系不同,但最为相近;与狂犬病固定毒株亲缘关系较远;与狂犬病相关病毒亲缘关系最远。     

Studies of ERA/BHK-21 rabies vaccine in skunks and mice.

ERA rabies vaccine virus grown in BHK-21 13S cells (ERA/BHK-21) and street rabies virus were titrated in mice by intracerebral, intranasal and intramuscular inoculation. Mice were also given undiluted ERA/BHK-21 in baits. Skunks were given undiluted ERA/BHK-21 in baits and by intramuscular, intranasal and intestinal inoculation. Virus neutralizing antibody titers against rabies virus were measured over a three month observation period. The surviving skunks were challenged by intramuscular inoculation with rabies street virus from a skunk salivary gland suspension. When titrated in mice, ERA/BHK-21 had titers of 10(7.0), 10(5.2) and 10(3.9) median lethal doses per mL by the intracerebral, intranasal and intramuscular routes, respectively. All skunks (8/8) inoculated intranasally developed paralytic rabies by 12 days after exposure to ERA/BHK-21 virus. None of the skunks that developed vaccine-induced rabies had infectious virus in the submandibular salivary glands. Vaccine-induced rabies also occurred in 1/8 skunks in the intramuscularly inoculated group and in 1/8 in the intestinally inoculated group. The survival rates of challenged skunks in the various groups were as follows: intramuscular, 7/7; intestinal, 2/7; bait, 0/8; and control, 0/8. These results indicate that ERA/BHK-21 virus has a significant residual pathogenicity in mice and in skunks by some routes of inoculation. Skunks given vaccine intramuscularly were protected against challenge, while those skunks given the vaccine in baits were not.     

狂犬病病毒CTN株糖蛋白基因的克隆与序列分析

克隆分离自我国狂犬病病毒固定毒CTN株糖蛋白基因,分析它的主要功能位点表明它具有319位的糖基化位点和完整的抗原位点,说明其具有用作疫苗株的潜力。并与国内外疫苗株、我国的3株街毒株、CVS株和Mokola毒株进行了同源性分析,表明我国疫苗株和CVS株与我国的街毒株相距最远,而CTN株与我国的3株街毒株相距最近,同属一个分支。     

Evaluation of an inactivated rabies virus vaccine in domestic ferrets

Efficacy of an SC-administered commercial inactivated vaccine for prevention of rabies was evaluated in domestic ferrets. Ferret immunity was challenged by the IM inoculation of street rabies virus. All ferrets developed titers of rabies virus-neutralizing antibodies within 30 days of vaccination (geometric mean titer [GMT] = 154, n = 41) that were maintained for at least one year (GMT = 106, n = 36), compared with no seroconversion in controls (GMT less than 5, n = 39). Following rabies virus challenge inoculation, 89% (32/36) of vaccinated ferrets survived vs less than 6% (2/38) survival in control ferrets. These results demonstrate the protective efficacy of a commercial, inactivated rabies vaccine of at least one year's duration for domestic ferrets.     

Sylvatic Rabies Studies in the Silver Fox (Vulpes vulpes). Susceptibility and Immune Response

The trials reported here show that the fox is highly susceptible to rabies virus. Vaccination with ERA rabies vaccine was capable of protecting foxes against challenge with naturally occurring strains of sylvatic rabies.

Oral immunization against rabies using ERA rabies vaccine was possible.

     

Immunofluorescence Study of Wild Rabies Virus and Antibody

A concentrate of wild rabies antibody was prepared from hyperimmune serums of three dogs refractory to wild rabies. The animals resisted repeated intramuscular injections of large doses of wild rabies virus in emulsions of whole brain, in emulsions of submaxillary salivary glands, and in emulsified mixtures of brain and submaxillary glands taken from naturally rabid dogs.

The antibody was conjugated with fluorochrome and then absorbed by a procedure that gave “cell-free” working solutions of fluorescent antibody. The procedure entailed parallel absorption steps with minced pathological canine submaxillary glands from (1) naturally rabid dogs (these glands contained specific, undegraded, natural antigens of live wild rabies virus plus nonspecific substances and antigens) and (2) nonrabid dogs from a rabies endemic region (these glands contained nonspecific substances and antigens).

Extracts from submaxillary glands of the three naturally rabid dogs and one nonrabid dog were stained with a cell-free solution of the fluorescent antibody. The glands of the rabid dogs contained fluorescent aggregates of intense green spherical and filamentous particles. When nonfluorescent canine hyperimmune serum was incubated with rabies-containing submaxillary extract, the rabies antigens were quenched. When nonfluorescent equine fixed virus antiserum was incubated with such extracts, the aggregates still retained bright fluorescence.

     

The demonstration of rabies antigen in paraffin-embedded tissues using the peroxidase-antiperoxidase method: a comparative study.

Mice experimentally infected with challenge virus standard rabies virus as well as skunks and foxes experimentally infected with street rabies virus were used to demonstrate rabies viral antigen in paraffin-embedded tissue by the peroxidase-antiperoxidase method. Tissues fixed with different fixatives (10% formalin, Bouin's, acetone, ethanol) for various times and fresh frozen tissues were stained by the fluorescent antibody and the peroxidase-antiperoxidase method. Formalin- and Bouin's-fixed tissues were tested with and without use of digestive enzyme (pepsin). The results demonstrated that a procedure using formalin-fixed paraffin-embedded tissue treated with pepsin and stained by peroxidase-antiperoxidase was the best method for both preservation of morphological details and demonstration of antigen.     

Nested PCR检测狂犬病病毒方法的建立及病毒在小鼠体内的移行动态

应用建立的Nested PCR特异地检出狂犬病病毒株CVC、HEP-Flury、ERA、RC-HL、1008、Komatsug-awa的RNA,但对类狂犬病病毒Lagos bat、Duvenhage、Mokola及水泡性口膜炎病毒、轮状病毒、犬瘟热病毒均为阴性。该法敏感性很高,能检出3 TCID50或0.8pg的狂犬病病毒RNA。用该法测定了小鼠脑内感染CVS株后的病毒增殖和移行动态,对感染小鼠的主要内脏器官进行了病毒RNA检测,结果发现小鼠脑内感染CVS 5 d以后在其心、肝、脾、肺等内脏器官均检出了病毒RNA。     

两株狂犬病病毒强毒株糖蛋白基因的克隆及潜在抗原表位分析

通过RT-PCR分别获得了狂犬病病毒强毒CVS株、DRV82株糖蛋白基因,进行克隆及测序,并推导出氨基酸序列,与犬用疫苗弱毒株ERA、SRV9、犬源性街毒株CGX及人用疫苗株PG的糖蛋白序列进行比较。结果表明,以上狂犬病病毒毒株间的核苷酸同源性为83.1%～99.2%,氨基酸序列同源性为87.0%～98.5%。经Jameson-Wolf抗原表位优势图分析,CVS株与其他各株相比发现在304位、372位抗原表位优势升高;而DRV82株与其它各株差异不明显。抗原优势变化可能导致狂犬病病毒糖蛋白出现新的潜在抗原位点,为下一步构建不同毒株的狂犬病病毒糖蛋白重组疫苗奠定了基础。     

Antigenic characterization of street rabies virus isolates from Nigeria using monoclonal antibodies

Twenty isolates of street rabies virus were recovered in mouse neutroblastoma cells from 84 rabies suspect brain specimens from Nigeria dogs and a cat. They were characterized with the Tübingen monoclonal antibody panels directed against nucleocapsid and glycoprotein antigens. Antigenic variations were detected both with antinucleocapsid (anti-NC) and antiglycoprotein (anti-GP) monoclonal antibodies (mabs). One isolate reacted positively with anti-NC mab P41 which hitherto has been known to react positively with polar rabies. Another isolate did not react with anti-NC mab 187.5; a reaction normally seen with ERA/SAD strains of rabies virus. With anti-GP mabs it was possible to group the isolates by their area of origin. Isolates from Plateau State were not neutralized by anti-GP mabs ERA 543 and P44.7.2. The isolates studied had glycoprotein antigenic patterns different from the pattern for low egg passage (LEP) Flury strain vaccine virus used in Nigeria for immunization of dogs.     

The ERA Strain of Rabies Vaccine

An antigenic extinction trial in cats showed that the ERA rabies vaccine had superior antigenic properties over Flury H.E.P. C.E.O. and killed tissue culture rabies vaccine.

Dogs and cats on a duration of immunity study of ERA rabies vaccine were challenged with fox salivary gland “street” rabies virus. The results of this challenge show a duration of immunity of five years in dogs and four years in cats.

Vaccination of dams in late pregnancy with ERA rabies vaccine resulted in transference of maternal antibody to the newborn, in both cattle and dogs. This maternally derived antibody interfered with the successful active immunization of the young calf. Calves free of antibodies for rabies could be successfully vaccinated as early as 17 days of age and were able to withstand a challenge with virulent “street” rabies virus two years later.

     

Experimental rabies in skunks: persistence of virus in denervated muscle at the inoculation site.

Striped skunks (Mephitis mephitis) were inoculated into the denervated abductor digiti quinti muscle with street rabies virus. They were killed at various times after inoculation and several tissues were examined by immunofluorescence and light microscopy. Muscle at the inoculation site was examined electron microscopically. Rabies antigen was detected in muscle fibers first on day 7 and persisted until day 28. Light and electron microscopic lesions at the inoculation site included atrophic and degenerating muscle fibers and a few focal and regional endomysial accumulations of macrophages, lymphocytes and plasma cells. Scattered myocytes contained bodies of matrix, virions and anomalous tubular structures on electron microscopic examination. The results indicate that replication of rabies virus may occur in infected muscle fibers at the inoculation site until 28 days after exposure. This could contribute to variations in the incubation period for the first two to three months after exposure. However, the results do not support the contention that virus is contained in striated muscle cells throughout the long incubation periods.     

梅花鹿狂犬病的病原学研究

应用鼠脑传代,从具有神经症状和后躯麻痹的鹿尸脑组织分离获得5株弹状病毒。对其中一株——8202株,从形态学、生物学和理化学等方面进行了鉴定。应用弹状病毒料中狂犬病海和狂犬相关病毒等的抗血清或免疫腹水,在小鼠体内进行交叉中和试验,证明鹿毒8202株同狂犬病毒固定毒(北京株)有密切的抗原联系。经WHO狂犬病咨询和研究协作中心应用42个单克隆抗体,以间接荧光抗体试验检测鼠脑压印片,证明该株病毒的核衣壳抗原结构与大多数陆栖哺乳动物狂犬病毒相同,但有别于欧洲狐狸的狂犬病毒;用40个抗糖蛋白单克隆抗体,通过血清中和试验,证明8202株同欧洲狐狸毒株很相似。将该毒复旧鹿体,并接种犬及其他动物,发现其对鹿的毒力很强,而对犬及其他家畜毒力较弱,甚至没有毒力。结论认为,鹿毒8202株是狂犬病毒适应于鹿体的变异株。     

Distribution of rabies virus in infected mice,vaccinated and submitted to P. acnes as immunomodulator

The lethality and distribution of rabies virus were evaluated in swiss mice experimentally infected with street rabies virus, vaccinated and submitted to immunomodulation by P .acnes (formerly Corynebacterium parvum). The animals were sacrificed at different times,when the different tissues were collected and submitted to fluorescent antibody test (FAT) and mouse inoculation test (MIT). The group submitted to vaccination and P. acnes treatment presented a percentage of survival superior to that observed in infected mice only treated with P. acnes. Control infected animals had the lowest survival rates.The distribution of rabies virus in spleen of infected mice, vaccinated and submitted to P. acnes was superior to that verified in infected mice not treated with P.acnes. The increased survival correlated with the distribution of rabies virus in lymphoid tissues, could be interpreted as the consequence of P. acnes activity on macrophages. The results suggest the role of macrophages against rabies virus infection in mice and the importance of vaccination in the post expositive treatment of rabies.     

湖南湘西地区外观健康犬携带狂犬病病毒的调查研究

为了解湖南湘西地区外观健康犬携带狂犬病病毒的情况,我们于2005年9月从湘西狂犬病疫点采集38份扑杀的外观健康的犬脑组织,并于2006年1月在湘西农贸市场采集了168份外观健康的犬脑组织。RT-PCR和直接荧光抗体试验(FAT)检测表明共有5份犬脑标本为阳性,并用乳鼠脑内接种的方法分离得到了5株狂犬病病毒毒株,分子流行病学分析表明这5株病毒均为野毒。在这5份阳性标本,疫点有4份,检出率为10.5%,市场1份,检出率为0.59%。我们的调查结果表明疫点的外观健康犬携带狂犬病病毒的检出率与国内的其它报道接近,而从市场采集的标本的检出率却要低很多。     

Simultaneous Growth of Rabies and Canine Distemper Viruses in Chick Embryos

Rabies virus and canine distemper virus were grown simultaneously, and possibly symbiotically, in the same chick embryos. There seemed to be no adverse effect on either virus when cultured in such manner.

Bivalent vaccines for rabies and canine distemper were produced. The potencies and the virus titers of such vaccines were comparable to those of rabies vaccine and canine distemper vaccine produced separately.

     

Spill‐over of European Bat Lyssavirus Type 1 into a Stone Marten (Martes foina) in Germany

European bat lyssavirus type 1 (EBLV‐1, genotype 5) is known to endemically circulate in insectivorous bat populations in Germany. In August 2001, a rabies suspect stone marten (Martes foina) was found in the city of Burg (Saxony‐Anhalt, Germany) and was sent to the regional veterinary laboratory for routine rabies diagnosis. Whereas brain samples repeatedly tested negative in the fluorescent antibody test for classical rabies virus (genotype 1), the mouse inoculation test and the rabies tissue culture inoculation test yielded positive results. Rabies viral RNA was also detected in the stone marten brain sample both by nested and heminested RT‐PCR specific for the nucleoprotein gene and for the nucleoprotein phosphoprotein junction of rabies virus. The amplification products were sequenced to genotype the isolate. Sequence data obtained from the first‐round RT‐PCR products were analysed and the suspect stone marten isolate was confirmed as a rabies related virus (EBLV‐1a). Phylogenetic comparison with sequences from recent genotype five isolates from Germany and Denmark showed that it was closely related to a previous isolate of EBLV‐1 from a serotine bat in Saxony‐Anhalt obtained in the same year in an area adjacent to the place where the EBLV‐1 infected stone marten was found. Both EBLV‐1 isolates share a 99.5% identity. This is the first report of an EBLV‐1a spill‐over from an insectivorous bat into wildlife in Europe.     

Cell-mediated immune response to rabies virus in dogs following vaccination and challenge

Peripheral blood lymphocytes (PBL) from non-vaccinated dogs and from dogs either vaccinated intramuscularly (IM) or subcutaneously (SC) with an inactivated rabies virus vaccine (Rabguard-TC, Norden Laboratories, Lincoln, NE) or intramuscularly with an attenuated rabies virus vaccine (Endurall-R, Norden Laboratories, Lincoln, NE) were exposed in vitro to rabies virus. Blastogenesis of PBL was measured by incorporation of 3H-thymidine into the DNA of proliferating cells in the presence of a suboptimal concentration of phytohemagglutinin (PHA). Following the first vaccination, there was no difference in the blastogenic response of lymphocytes from dogs vaccinated IM with either the inactivated or attenuated rabies virus vaccines. The inactivated rabies vaccine stimulated as great or greater blastogenic response when it was given SC. The PBL from non-vaccinated control dogs were not stimulated by rabies virus. Dogs vaccinated with the inactivated vaccine developed a lymphocyte blastogenic response to rabies virus following challenge with virulent street rabies virus. Nonvaccinated control dogs did not develop a lymphocyte blastogenic response to rabies virus following challenge with virulent street rabies virus.