Geneviève André-Fontaine

Binding of Rabbit Hemorrhagic Disease Virus to Antigens of the ABH Histo-Blood Group Family

ABSTRACT The ability of rabbit hemorrhagic disease virus to agglutinate human erythrocytes and to attach to rabbit epithelial cells of the upper respiratory and digestive tracts was shown to depend on the presence of ABH blood group antigens. Indeed, agglutination was inhibited by saliva from secretor individuals but not from nonsecretors, the latter being devoid of H antigen. In addition, erythrocytes of the rare Bombay phenotype, which completely lack ABH antigens, were not agglutinated. Native viral particles from extracts of infected rabbit liver as well as virus-like particles from the recombinant virus capsid protein specifically bound to synthetic A and H type 2 blood group oligosaccharides. Both types of particles could attach to adult rabbit epithelial cells of the upper respiratory and digestive tracts. This binding paralleled that of anti-H type 2 blood group reagents and was inhibited by the H type 2-specific lectin UEA-I and polyacrylamide-conjugated H type 2 trisaccharide. Young rabbit tissues were almost devoid of A and H type 2 antigens, and only very weak binding of virus particles could be obtained on these tissues.

Evidence of cross-protection within Leptospira interrogans in an experimental model

Killed whole-cell preparations were used as bacterins against leptospirosis. As this type of protection is considered to be serogroup-specific, several serogroups were added to the usual vaccines, and the most pathogenic serovar was chosen for each group. Different leptospire extracts were evaluated for their protective capacity against acute lethal leptospirosis in gerbils (Meriones unguiculatus). Total extracts induced complete protection against homologous challenges and partial protection against heterologous challenges. LPS fractions protected against homologous but not heterologous challenges, whereas protein extract induced significant protection against both types of challenge. Thus, cross-protection within L. interrogans was related to the protein extract.

Leptospira exposure in the human environment in France: A survey in feral rodents and in fresh water.

This paper confirms the important role of rodents to be maintenance hosts of leptospires. Their role is related to renal carriage and shedding of leptospires into urine, thus contaminating fresh water. Serological and carriage of feral rodents trapped in France were determined by MAT and hap1PCR specific for pathogenic leptospires. In same areas, fresh water samples were analyzed by hap1PCR. The overall seroprevalence was 44% in 649 rodents and was similar regardless of the species. Seroprevalence for leptospirosis is about 20-53% according to species. hap1PCR (516 kidneys) showed that renal carriage was higher in brown rats (34.7%) and muskrats (15.8%) than in coypus (3.3%). hap1PCR demonstrates a significative difference (P-value > 10(-12)) for the renal carriage between the different species: muskrats and rats are more efficient maintenance hosts than coypu but all infect water. Moreover 5/38 water samples associated with human cases were hap1PCR positive and 1/113 in controlled waters.

Identification of pathogenic Leptospira strains in tissues of a premature foal by use of polymerase chain reaction analysis

Studies were carried out to determine the cause of death in a prematurely born Thoroughbred foal that died 24 hours after birth. Necropsy revealed gross lesions suggestive of septicemia. A commercial Leptospira polymerase chain reaction (PCR) assay designed to specifically amplify the hemolysis-associated protein 1 (hap1) gene present only in pathogenic Leptospira strains detected the presence of Leptospira DNA in various tissues of the foal. Histologic examination of lung, liver, kidney, and myocardium revealed numerous spirochetes in Warthin–Starry-stained tissue sections. Results of PCR analysis and histologic examination suggested a leptospiral infection in the newborn foal. At the moment of death, the infection coexisted with a streptococcal-associated aspiration bronchopneumonia and postpartum septicemia. These findings indicate that the PCR assay based on the amplification of the hap1 gene represents a useful tool for specific detection of pathogenic leptospira in field samples taken from horses.

Role of the coypu (Myocastor coypus) in the epidemiology of leptospirosis in domestic animals and humans in France

The coypu (Myocastor coypus), a rodent whose natural habitat is stagnant freshwater, has become a widespread pest in France within the last decade. This study investigated the prevalence of seropositivity and the renal carriage of leptospires in coypus in order to evaluate their role in terms of the risk of infection by Leptospira interrogans in domestic animals and humans. The study involved the application of serological and bacteriological methods to identify leptospires infection and/or carriage in 738 coypus trapped from 1996 to 1999 in six areas of France. Seroprevalence in samples ranged from 16.5 to 66%, and three field strains were isolated (two L. interrogans Icterohaemorrhagiae and one L. interrogans Sejroe). This first report on the isolation of leptospires from coypus in France emphasises the role of this animal in the epidemiology of leptospirosis.

New topics on leptospirosis

In the United States, leptospirosis takes the second place in human diseases transmitted by animals. The clinical features of leptospirosis are very various in man and domestic animals by the nature of the serovar involved and the animal species infected. There are many epidemiological cycles of leptospirosis but environmental conditions are always important.

Multilocus Sequence Analysis for Typing Leptospira interrogans and Leptospira kirschneri

ABSTRACT Fifty-three strains belonging to the pathogenic species Leptospira interrogans and Leptospira kirschneri were analyzed by multilocus sequence analysis. The species formed two distinct branches. In the L. interrogans branch, the phylogenetic tree clustered the strains into three subgroups. Genogroups and serogroups were superimposed but not strictly.

Synthetic peptide issued from Hap1/LipL32 for new early serodiagnosis of human leptospirosis

Leptospirosis is a worldwide zoonosis. Today, serological diagnosis is generally assessed by MAT. We performed ELISA with a synthetic peptide derived from Hap1/lipL32 which is a protein expressed only by pathogenic Leptospira. Repeatability and thresholds were defined with 85 controls sera and 119 hospitalized leptospirosis. The PP-ELISA repeatability and IgM/IgG cut-off values were based on control sera. For these cut-off values, we observed the IgM-PP-ELISA specificity of 89%, whereas it was 100% for the IgG. Then, we compared PP-ELISA and standard MAT results for leptospirosis patients. The concordance rate for IgM-PP-ELISA and MAT was low (43%), whereas it was 85% for IgG-PP-ELISA and MAT. During the first 5 days after hospitalization, PP-ELISA gave positive results in 13 out of 16 patients (81%) whereas 8 out of 14 patients (57%) were positive to MAT. ELISA using Hap1/lipL 32-derived synthetic peptide PP is an earlier serological diagnosis of human leptospirosis than MAT.

Recognition of Leptospira interrogans antigens by vaccinated or infected dogs.

Antigenic recognition of leptospiral antigens by vaccinated or infected dogs was studied by microagglutination test (MAT) and by western blots. In western blots, serovar specific antigens detected by MAT migrated in the 18-31 kDa zone. The 25-31 zone seemed to be linked to antigens indicating virulence of the strain. These antigens are LPS. The first antibodies made after infection are produced against LPS migrating in the 14 kDa zone. Many protein antigens are common in leptospires belonging to different serogroups. Virulent strains exhibited specific antigens in the 45 and 32-34 kDa zones.

Immunoblotting study of the antigenic relationships among eight serogroups of Leptospira

Seven strains of Leptospira interrogans belonging to seven different serogroups, and one strain of Leptospira biflexa were analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with gradient gels and immunoblotting with hyperimmune rabbit sera raised against each strain. The molecular masses of the proteins were calculated with a polynomial regression model. The SDS-PAGE patterns of the L. interrogans strains were similar and characterized by 24 common bands. This profile was not found for L. biflexa. The immunoblots obtained either with the seven anti-L. interrogans sera or the anti-L. biflexa serum allowed a clear distinction between the two species. Taken as a whole, the L. interrogans strain patterns revealed by the seven anti-L. interrogans sera were similar, sharing eight common major bands. A serovar- or serogroup-specific antigenic zone, ranging from 21 to 26 kDa, was also identified.