Pierre E. Rollin

Rift Valley fever epizootic in the central highlands of Madagascar

Between February and April 1991, unusual numbers of bovine abortion around Antananarivo (central highlands, Madagascar) were reported by official veterinary services. Rift Valley fever (RVF) virus isolations were made from sixteen aborted foetuses and one dead calf in different foci. Using monoclonal antibodies, the isolated viruses were found to be different from the 1979 RVF strains isolated in Madagascar from mosquitoes and human laboratory infection, and closer to African RVF strains. In a bovine population--previously characterized by a negative or very low RVF antibody prevalence--a high prevalence of IgM antibodies (264/994: 26.5% positive) was revealed; the IgM prevalence in recently aborting females varied from 40 to 91%. Among 994 human sera tested by IgG-IFA (immunofluorescent antibody assay) and IgM ELISA, 8.2% and 4.5%, respectively, proved positive. A total of 11,371 mosquitoes (61% Culex antennatus) were collected in the epizootic areas and tested without any virus isolation. Extensive studies were conducted to determine the geographical extension and the impact of this epidemic on the highly susceptible livestock and human populations.

Rift Valley fever on the east coast of Madagascar.

In March 1990, a Rift Valley fever virus (RVFV) outbreak was suspected in the district of Fenerive on the east coast of Madagascar after an abnormally high incidence of abortions and disease in livestock. Sera from humans and cattle were tested for RVFV antibodies by immunofluorescence assay (IFA) and ELISA-IgM capture. Sera and mosquitoes collected in the same area were tested for virus isolation by tissue culture and suckling mouse intracerebral inoculation, and for antigen detection by an ELISA antigen capture assay. Among cattle from the area, RVFV antibody prevalence was 58.6% by IFA and 29.6% by ELISA-IgM. In contrast, human populations in the same area had a lower RVFV antibody prevalence, with 8.01% IFA and 5.4% IgM-positive sera. No RVFV antigen was detected and virus isolation was unsuccessful from the sera and mosquito pools tested. Different hypotheses concerning the emergence and diffusion of RVFV in this area and the occurrence of the outbreak are discussed.

Premier isolement du virus Mokola à partir d'un rongeur (Lophuromys sikapusi)

Summary An isolate of Mokola virus (AnRB3247) was obtained from the brain of a wild rodent Lophuromys sikapusi caught in the Central African Republic. This was the first isolation of Mokola virus from a rodent and the first isolation of this virus in the Central African Republic. This isolate was identified with Mokola virus by complement fixation and seroneutralization tests. The antigenic pattern of this isolate was determined with a panel of monoclonal antibodies, and was compared to those of Mokola isolates from Nigeria and Cameroun, of Lagos bat virus and of Duvenhage virus.

Correlations entre l'epreuve immunoenzymatique, la seroneutralisation et la reduction de foyers fluorescents pour le titrage des anticorps rabiques

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.

Protein kinase in human plasma analogous to that present in control and interferon-treated HeLa cells

Abstract A protein kinase activity analogous to that found in interferon-treated HeLa cells is detectable in human plasma. This kinase activity is manifested by the phosphorylation of an endogenous 72,000 molecular weight protein which is stimulated markedly by Mn2+. The protein kinase activity in human plasma can phosphorylate calf thymus histones and is independent of cyclic AMP. The phosphate is linked to the phosphorylated 72,000 molecular weight protein by its serine and threonine residues. The level of protein kinase activity in 50 different normal human plasma that we analysed varied from one individual to the other. Treatment of two patients with fibroblast (β) interferon resulted in an enhanced level of the protein kinase activity in the plasma. These results suggest that such protein kinase activity in human plasma may reflect the presence and action of circulating interferon.

Avirulent mutants of the CVS strain of rabies virus.

Two avirulent mutants of the CVS strain of rabies virus have been isolated on the basis of their loss of sensitivity to antiglycoprotein neutralizing monoclonal antibodies. With the exception of virulence, both retain general characteristics of the CVS strain of the rabies virus. After inoculation, they induce a strong and rapid immune response in adult mice. In this respect, however, they are quite different from the parental CVS strain. Surviving mice are protected against intramuscular challenge with 10(3.4 LD50 of a field isolate of rabies virus.

Variantes antigeniques du virus rabique: Souches des rues de France, d'Afrique, de Madagascar et d'Asie resultats preliminaires obtenus avec des anticorps monoclonaux antinucleocapside

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.

Étudede la réponse immunitaire humorale au «vaccin rabique purifié pasteur après traitement post-exposition: Study of the humoral immune response 023 to the «pasteur purified rabies vaccine in post-exposure treatment

Summary The purified inactivated Pasteur rabies vaccine was prepared on primary culture of foetal bovine kidney cells using the Pasteur fixed rabies virus (PV). A clinical trial in a post-exposure situation was carried out on a group of 130 volunteers. The vaccine was administered according to the WHO scheme for vaccines prepared on human diploid cells: 4 injections of 1.0 ml on days 0, 3, 7 and 14, followed by booster doses on days 30 and 90. This induced the production of neutralizing antibodies, detected from day 14. Neither local nor systemic adverse reactions of any importance were registered.

Safety and immunogenicity of combined rabies and typhoid fever immunization

The prevalence of rabies and typhoid fever in many developing countries poses a serious health hazard to travellers. The development of a combined immunization schedule would be advantageous. A study was performed on 104 adult volunteers using purified Vero cell rabies vaccine and Typhim Vi, a purified capsular polysaccharide, either separately or in combination. No significant difference was observed in immunogenicity or tolerance between the two groups. A 3-year follow-up study is planned.

Trial of economical regimens of suckling mouse brain rabies vaccine for postexposure prophylaxis in Lagos, Nigeria

The suckling mouse brain rabies vaccine, recommended for production and routine use in Nigeria from our previous study, was investigated in the present study in an effort to reduce the cost of antirabies treatment in the country. This is needed for economic reasons. Instead of seven daily doses followed by three boosters, we tried five daily doses followed by three boosters, with or without equine hyperimmune serum given on day 0 (40 IU per kg body weight). Fifty dog-bite, victims, aged 3-81 years, were placed on this regimen, 25 with serum and 25 without serum, according to the history of the case. The serum had no effect on the kinetics of antibody development and both serum and vaccine were well tolerated. The geometric mean titres (GMTs) of antirabies antibodies in the sera of recipients of vaccine alone on days 10, 28 and 90 were 3.05 equivalent units ml-1 (EU ml-1), 4.35 EU ml-1 and 2.54 EU ml-1 respectively. Among those who had received antiserum and vaccine the titres were respectively 3.19 EU ml-1, 4.35 EU ml-1 and 3.02 EU ml-1. Of the 50 subjects, 49 showed detectable antibodies by day 28, and all the 50 survived. This regimen is therefore recommended for further trial in countries where rabies is endemic but potent antirabies vaccines are scarce and expensive. Another 23 subjects, considered not to be at risk of rabies, were given a one-tenth dose, two-site intradermal inoculation of the same vaccine on days 0, 3, 7, 14, 28 and 90.(ABSTRACT TRUNCATED AT 250 WORDS)