A collaborative study of an experimental kit for rapid rabies enzyme immunodiagnosis (RREID)

Six laboratories took part in a study to assess an experimental kit for the diagnosis of rabies using the rapid rabies enzyme immunodiagnosis (RREID) technique. The test is based on the immunocapture of rabies antigens present in homogenized brain specimens, followed by enzyme immunoassay. A total of 1253 specimens from various geographical locations and 27 animal species were tested with the RREID technique, and also with the fluorescent antibody test (FAT), which was used as a reference method. For 1220 specimens the results in RREID and FAT were the same (651 positive and 569 negative-concordance: 97.4%). However, the RREID technique appeared to be less sensitive, since 22 (3%) of the 673 specimens that were positive with FAT were negative with RREID. The RREID test is therefore specific and convenient and is a useful tool for epidemiological studies and for laboratories not equipped with an ultraviolet microscope.

An evaluation of second generation tissue culture rabies vaccines for use in man: a four-vaccine comparative immunogenicity study using a pre-exposure vaccination schedule and an abbreviated 2-1-1 postexposure schedule

In a double-blind comparative trial the immunogenicity of three new tissue culture rabies vaccines was evaluated, using a commercial human diploid cell vaccine (HDCV) lot as the reference. Two different vaccination regimens, a pre-exposure schedule, and an abbreviated 2-1-1 postexposure schedule (two doses of the vaccine applied bilaterally on day 0, with subsequent single doses given on days 7 and 21) were employed. In both, two of the new vaccines, purified chick embryo cell vaccine and purified Vero rabies vaccine, induced an antibody response equivalent to that of HDCV, while the geometric mean titres for the fetal bovine kidney cell vaccine were somewhat lower. The 2-1-1 regimen, a candidate regimen for economical rabies postexposure treatment, evoked a rapid and high titre antibody response with all four vaccines, peaking on day 14.

A rapid rabies enzyme immuno-diagnosis (RREID): a useful and simple technique for the routine diagnosis of rabies

A Rapid Rabies Enzyme Immuno-Diagnosis (RREID) technique has been developed. This technique for the diagnosis of rabies was performed in microplates which had been previously sensitized with IgG to purified antinucleocapsids. Suspensions of homogenized material were incubated in the plate and the specific binding of rabies antigen was revealed by the use of the same IgG conjugated with peroxidase. With the RREID technique it was possible to detect rabies antigens in brain specimens with the same specificity and sensitivity as that of the direct immunofluorescence test or the neuroblastoma cell inoculation technique regardless of the species of animal from which the specimen was derived. Moreover, RREID was performed with fox salivary gland specimens with the same results as were obtained with brain specimens. RREID does not require an UV light microscope and a photometer is not essential. It is a useful and simple technique for the routine laboratory diagnosis of rabies.

The influence of the type of immunosorbent on rabies antibody EIA; advantages of purified glycoprotein over whole virus

Two types of in vitro assay (enzyme immunoassay and sero-neutralization test) for the titration of rabies antibodies were used to assay sera from mice and humans immunized with cell culture vaccines or neural tissue vaccines. Enzyme immunoassays (EIA) were performed in plates sensitized with whole virus, purified glycoprotein or purified nucleocapsid. Neutralizing antibody titres were determined by the rapid fluorescent focus inhibition test (REFIT) and by an in vitro seroneutralization test including a rapid enzyme immunotitration of intracellular antigens (REITICA). The results obtained with sera of immunized mice and humans showed that (1) cell culture vaccines mainly induced the synthesis of antiglycoprotein neutralizing antibodies; and (2) neural tissue vaccines induced a high synthesis of antinucleocapsid non-neutralizing antibodies and a more or less important synthesis of antiglycoprotein antibodies depending on the origin of the tissue used for their preparation. Consequently, it was emphasized that when using EIA, the antibody titration must be run in glycoprotein-coated plates rather than in whole virus-coated plates to appreciate correctly the immunizing potency of a rabies vaccine, especially neural tissue vaccine.

Lack of interferon induction in man by two rabies tissue culture vaccines

Both neutralising antibody and interferon play a part in protection of animals against death from rabies virus infection. Interferon induction was therefore sought in 53 volunteers within 24 hours of receiving human diploid cell strain vaccine or fetal bovine kidney cell vaccine given either intramuscularly or intradermally. Repeat observations were made in 18 subjects following a second dose of vaccine seven days later. No interferon was detected in any sample tested although no subject had any detectable rabies neutralising antibody on day 0. The sensitivity of the interferon assay, and comparison with other studies are discussed. An interferon inducer suitable for human use should be sought as an alternative to, or a replacement for, passive rabies immunization.

Use of a monoclonal antibody for quantitation of rabies vaccine glycoprotein by enzyme immunoassay

The use of a monoclonal antibody specific for the envelope glycoprotein of rabies virus has been used in a direct enzyme immunoassay to quantify the glycoprotein content of rabies vaccines produced in two kinds of cell culture. The results of this direct enzyme immunoassay are well correlated with the in vivo NIH potency test. This test may be a useful tool to rapidly and accurately control the antigenic value of a vaccine. It could also be used for the "in process' control of vaccine production before deciding whether a vaccine batch may reasonably be subjected to the NIH potency test.

Rabies immunosome (subunit vaccine) structure and immunogenicity. Pre- and post-exposure protection studies

Rabies immunosomes (glycoprotein anchored on pre-formed liposomes) have been prepared in order to study their structural, biological and immunological properties. The glycoprotein molecules appear to have the same orientation on the immunosome as on the viral particle: (1) electron microscopy analysis shows particles of 40 to 70 nm with spikes protruding outward, (2) one particular epitope shows the same accessibility to a neutralizing monoclonal antibody as on the viral particle. When injected into animals, rabies immunosomes are cleared from the organism by a process different from that for the liposomes used to anchor the glycoprotein: a higher rate of transition through the spleen is observed with immunosomes than with purified glycoprotein or liposomes. Immunosomes induce high levels of neutralizing antibodies and protect animals against challenge with virulent strains. This protective activity is not altered after several months of storage at 4 degrees C. Furthermore, rabies immunosomes were shown to be efficient in post-exposure treatment of laboratory animals that had been experimentally infected with a lethal dose of a rabies wild strain.

[Hemorrhagic fever with renal syndrome due to Hantaan virus or a serologically related virus]

Seven cases of acute renal failure consecutive to haemorrhagic fever with renal syndrome (HFRS) due to the Hantaan virus or to a serologically related virus are reported. These cases were observed in north-eastern France between March, 1983 and January, 1984. All patients were of rural origin and had been in contact with field mice. The predominant initial clinical symptoms were signs of infection and diffuse muscle pain, without evidence of haemorrhage. However, massive proteinuria was noted, and acute anuric renal failure unaccompanied by oedema or arterial hypertension developed. Renal biopsy performed in 2 patients showed tubular and interstitial nephritis but no glomerular or vascular lesions. Two patients only required haemodialysis. All patients recovered within 2 to 8 weeks without sequelae. Antibodies directed against the Hantaan virus were detected by indirect immunofluorescence tests, and seroconversion could be demonstrated in 2 patients seen at a sufficiently early stage. The risk of epidemics suggested by this small outbreak of HFRS can only be evaluated after an exhaustive epidemiological study.

Monoclonal antibodies as a tool for rabies epidemiological studies

Hybridoma-produced monoclonal antibodies specific of antigenic determinants of the nucleocapsid and the glycoprotein of rabies virus showed differences between fixed and street strains of rabies virus. Standard panels of monoclonal antibodies allowed us to determine the geographic origin of imported cases of rabies in animals and humans.

Epidemiologic analysis of antigenic variations of street rabies virus: detection by monoclonal antibodies

The nucleocapsid antigen of 204 strains of street rabies virus, which originated in Europe, Africa and Asia, was analyzed by fluorescent antibody staining technique with a panel of 20 monoclonal antibodies specific for nucleocapsid of rabies and rabies-related viruses. A definite pattern of reactivity was observed with strains of the same geographic origin with the exception of strains originating from Madagascar, Thailand and Iran which were more diversified. Mice immunized with a vaccine prepared from a Pasteur PV-11 strain of virus were well protected against challenge with representative strains from Europe and Africa, and a partial protection was observed following challenge with strains from Madagascar and Thailand.

[Antigenic variants among street rabies virus isolates from France, Africa, Madagascar and Asia. Preliminary results with antinucleocapsid monoclonal antibodies]

A panel of monoclonal antibodies directed against the nucleocapsid antigens of rabies virus allowed a rapid characterization of isolates by an indirect immunofluorescence test on brain smears of infected animals. Analysis of 77 isolates (71 from animals and 6 from humans) showed a great diversity. Isolates from different areas showed different patterns of reactivity. No relation was found between animal species and antigenic patterns specificity.

[Correlations between immunoenzymatic test, neutralization test and fluorescent focus reduction test in rabies antibody titration]

Three methods have been used and compared for the detection and titration of antibodies in the serum of humans receiving post-exposure treatment with tissue culture inactivated rabies vaccines: mouse seroneutralization test, fluorescent focus reduction test and immunoenzymatic test. Results have shown that the fluorescent focus reduction test has a sensitivity and specificity which are equivalent to the mouse seroneutralization test with the advantage of giving results in 30 hr instead of 21 days, and that the immunoenzymatic test which avoids the use of laboratory animals and/or cell cultures, and which gives results in 5 hr, may advantageously replace the neutralization methods, particularly for the testing of large numbers of sera.

[Prevention of inter-human rabies transmission after corneal graft]

Transplantation, to a normal recipient, of a cornea taken from a donor who died of rabies encephalitis constitutes an extremely serious exposure. Four cases, up to now are known of human to human transmission of rabies virus. In these four cases, the diagnosis of rabies in the donor has been made afterwards when to the recipient developed fatal rabies. We report here the first case of this type of exposure where the diagnosis of rabies in the donor could be made on the day following the transplantation thus allowing application, without delay, the recipient of a prophylactic therapy for inactivated rabies vaccine administered. No signs or symptoms of rabies appeared and, more than three months after the transplantation, the recipient is well and alive.

[Arboviruses in Iran (author's transl)]

During an entomological survey conducted in april-june 1978 in the province of Khorassan in the eastern part of Iran, ixodid and argasid ticks were collected for arbovirus research. Five serotypes of arboviruses were obtained: Quaranfil, Thogoto, Wad Medani, Wanowrie and Crimean Haemorrhagic Fever-Congo. The isolation of all these arboviruses is reported for the first time in Iran.

[Sero-epidemiological survey of arbovirus diseases in the Bi-Aka pygmies of Lobaye, Central African Republic]

Sero-epidemiological survey for Arboviruses among Bi-Aka Pigmies of the Lobaye, Central African Empire. A sero-epidemiological survey has been conducted, in 1975-1976, among 349 nomadic Pygmies of the Lobaye area in the Central African Empire, to investigate the prevalence of arbovirus infections. The percentages of individuals with detectable antibodies were 9,5 % for Chikungunya, 13,5 % for Semliki Forest, 5,2 % for Sindbis; 11,7 % for Bunyamwera; 2,3 % for West Nile, 6,3 % for Uganda S, and 8,9 % for Yellow Fever. These results are similar to those found in 1964 by CHIPPAUX in a comparable group of Pigmies of the same area and confirm that the prevalence of arbovirus infections is lower in the nomadic pygmies of the same area and confirm that the prevalence of arbovirus infections is lower in the nomadic Pygmies than in the sedentary Pygmies as well as in the settled bantus of the Lobaye valley villages. Yellow fever specific antibodies detected in this non vaccinated population indicate that latent infections occur in human beings living in the depth of the tropical forest, from the natural sylvatic focus of yellow fever, which remains active as recently proven in the Central African Empire by virus isolations obtained from wild caught mosquitoes.

[Isolation of Thogoto virus from Amblyomma and Boophilus ticks in Central Africa]

A survey has been carried out in the Cameroons and the Central African Republic about the role of the ticks in the ecology of arboviruses in Central Africa. Attempts for virus isolation were made for 12,678 Amblyomma variegatum, 3,276 Boophilus decoloratus and 1,769 Boophilus annulatus, by inoculation into suckling mice. From 968 pools which were inoculated, 20 yielded isolates which were identified to Thogoto virus. Considering previously published results concerning tick-borne virus isolations in the Central African Republic, it appears now that five arboviruses are present in the ticks in central Africa : Dugbe, Jos and Thogoto (in A. variegatum, B. decoloratus and B. annulatus), Bhanja (in A. variegatum) and Chf. Congo (in Hyalomma nitidum).

[Surgey of tick-borne arboviruses in the Central African Republic (1973-1974). Isolation of Dugbe, CHF/Congo, Jos and Bhanja viruses]

As a complement of the study of the epidemiology of the arboviruses in Central Africa a survey of tick borne viruses has been done, in the Central African Republic, from December 1972 to June 1974; 15.103 ticks were collected, mainly from cattle at the slaughterhouses. They include: 10.085 Ambylomma variegatum, 4.113 Boophilus, 542 Rhipicephalus and 363 Hyalomma. From 892 monospecific pools inoculated into baby mice, 98 isolates of virus were obtained. Among the 57 isolates which have been fully identified (the identification of 41 other isolates is still in progress), 4 different serotypes of arbovirus have been found: Dugbe virus has been the most frequently found with 45 isolates from A. variegatum and I from B. decoloratus; this virus, previously isolated from human cases in Central African Republic in 1967 and 1970 has been isolated from a new human case in 1973. One isolate of CHF/Congo virus has been obtained from Hyalomma nitidum, but this virus has not yet been isolated from human beeings in C.A.R. The two other tick borne viruses isolated during this survey are Jos virus (9 isolates) and Bhanja virus (I isolate), all of them from A variegatum.