Lyme disease is caused by genetically divergent spirochetes, including 3 pathogenic genospecies: ... more Lyme disease is caused by genetically divergent spirochetes, including 3 pathogenic genospecies: Borrelia burgdorferi sensu stricto, B. garinii, and B. afzelii. Serodiagnosis is complicated by this genetic diversity. A synthetic peptide (C 6 ), based on the 26-mer invariable region (IR 6 ) of the variable surface antigen of B. burgdorferi (VlsE), was used as ELISA antigen, to test serum samples collected from mice experimentally infected with the 3 genospecies and from European patients with Lyme disease. Regardless of the infecting strains, mice produced a strong antibody response to C 6 , which indicates that IR 6 is antigenically conserved among the pathogenic genospecies. Twenty of 23 patients with culture-confirmed erythema migrans had a detectable antibody response to C 6 . A sensitivity of 95.2% was achieved, with serum samples collected from patients with well-defined acrodermatitis chronica atrophicans. Fourteen of 20 patients with symptoms of late Lyme disease also had a positive anti-IR 6 ELISA.
The alternative pathway of complement is an important innate defence against pathogens including ... more The alternative pathway of complement is an important innate defence against pathogens including ticks. This component of the immune system has selected for pathogens that have evolved countermeasures. Recently, a salivary protein able to inhibit the alternative pathway was cloned from the American tick Ixodes scapularis (Valenzuela et al ., 2000; J. Biol. Chem. 275, 18717-18723). Here, we isolated two different sequences, similar to Isac, from the transcriptome of I. ricinus salivary glands. Expression of these sequences revealed that they both encode secreted proteins able to inhibit the complement alternative pathway. These proteins, called I. ricinus antic omplement (IRAC) protein I and II, are coexpressed constitutively in I. ricinus salivary glands and are upregulated during blood feeding. Also, we demonstrated that they are the products of different genes and not of alleles of the same locus. Finally, phylogenetic analyses demonstrate that ticks belonging to the Ixodes ricinus complex encode a family of relatively small anticomplement molecules undergoing diversification by positive Darwinian selection.
Detection of the Borrelia burgdorferi sensu lato complex in biological samples is currently done ... more Detection of the Borrelia burgdorferi sensu lato complex in biological samples is currently done by conventional immunological and molecular biological methods. To improve on the accuracy of these methods and to simplify the procedure for testing large numbers of samples, a solid-phase sandwich hybridization system readily applicable to the detection of PCR products has been designed. This colorimetric detection system relies on the use of polybiotinylated detection probes and of specific capture oligonucleotides covalently linked at allocated positions on nylon membrane strips. From a phylogenetic analysis on a great number of ospA gene sequences, we have designed and synthesized a set of PCR primers specific to the five Borrelia burgdorferi sensu lato genospecies present in Europe and a subset of probes (capture and detection probes) specific to these five genospecies . This combined PCR hybridization system was evaluated with a large number of various B. burgdorferi isolates and clinical specimens. These analyses clearly showed that the system could be used as a typing method to distinguish five genospecies belonging to the B. burgdorferi sensu lato complex. In addition, the study showed that B. valaisiana strains might be more heterologous than suspected up to now and clustered into three genomic groups.
Eight ixodid tick species, associated with 59 free-ranging mammals belonging to 10 species, were ... more Eight ixodid tick species, associated with 59 free-ranging mammals belonging to 10 species, were collected at five different localities in the Free State Province, South Africa. Four of the study areas were nature reserves (Willem Pretorius, Sandveld, Tussen-die-Riviere, and Soetdoring), and one site was a private farm located in Senekal district. The collection was performed from March 2006 until June 2006. Ticks (n5569) and tissues from animals (n552) were analyzed by polymerase chain reaction, reverse line blot, and sequencing for various tickborne pathogens belonging to the genera Babesia, Theileria, Anaplasma, and Ehrlichia. Rhipicephalus (Boophilus) microplus, the known vector of Babesia bovis responsible for Asiatic redwater in South Africa, was found for the first time in the Free State Province. Rhipicephalus appendiculatus also was collected in areas in the Free State where it has not been previously described. Anaplasma marginale was detected for the first time in a gemsbok (Oryx gazella gazella). Gene sequences recovered in this study were 98-100% homologous with GenBank sequences for Anaplasma bovis, Theileria separata, and Theileria sp. Malelane sable antelope.
The vector-to-host and host-to-vector transmission steps are the two critical events that define ... more The vector-to-host and host-to-vector transmission steps are the two critical events that define the life cycle of any vector-borne pathogen. We expect negative genetic correlations between these two transmission phenotypes, if parasite genotypes specialized at invading the vector are less effective at infecting the vertebrate host and vice versa. We used the tick-borne bacterium Borrelia afzelii, a causative agent of Lyme borreliosis in Europe, to test whether genetic trade-offs exist between tick-to-host, systemic (host-to-tick), and a third mode of co-feeding (tick-to-tick) transmission. We worked with six strains of B. afzelii that were differentiated according to their ospC gene. We compared the three components of transmission among the B. afzelii strains using laboratory rodents as the vertebrate host and a laboratory colony of Ixodes ricinus as the tick vector. We used next generation matrix models to combine these transmission components into a single estimate of the reprod...
Lyme disease is caused by genetically divergent spirochetes, including 3 pathogenic genospecies: ... more Lyme disease is caused by genetically divergent spirochetes, including 3 pathogenic genospecies: Borrelia burgdorferi sensu stricto, B. garinii, and B. afzelii. Serodiagnosis is complicated by this genetic diversity. A synthetic peptide (C 6 ), based on the 26-mer invariable region (IR 6 ) of the variable surface antigen of B. burgdorferi (VlsE), was used as ELISA antigen, to test serum samples collected from mice experimentally infected with the 3 genospecies and from European patients with Lyme disease. Regardless of the infecting strains, mice produced a strong antibody response to C 6 , which indicates that IR 6 is antigenically conserved among the pathogenic genospecies. Twenty of 23 patients with culture-confirmed erythema migrans had a detectable antibody response to C 6 . A sensitivity of 95.2% was achieved, with serum samples collected from patients with well-defined acrodermatitis chronica atrophicans. Fourteen of 20 patients with symptoms of late Lyme disease also had a positive anti-IR 6 ELISA.
The alternative pathway of complement is an important innate defence against pathogens including ... more The alternative pathway of complement is an important innate defence against pathogens including ticks. This component of the immune system has selected for pathogens that have evolved countermeasures. Recently, a salivary protein able to inhibit the alternative pathway was cloned from the American tick Ixodes scapularis (Valenzuela et al ., 2000; J. Biol. Chem. 275, 18717-18723). Here, we isolated two different sequences, similar to Isac, from the transcriptome of I. ricinus salivary glands. Expression of these sequences revealed that they both encode secreted proteins able to inhibit the complement alternative pathway. These proteins, called I. ricinus antic omplement (IRAC) protein I and II, are coexpressed constitutively in I. ricinus salivary glands and are upregulated during blood feeding. Also, we demonstrated that they are the products of different genes and not of alleles of the same locus. Finally, phylogenetic analyses demonstrate that ticks belonging to the Ixodes ricinus complex encode a family of relatively small anticomplement molecules undergoing diversification by positive Darwinian selection.
Detection of the Borrelia burgdorferi sensu lato complex in biological samples is currently done ... more Detection of the Borrelia burgdorferi sensu lato complex in biological samples is currently done by conventional immunological and molecular biological methods. To improve on the accuracy of these methods and to simplify the procedure for testing large numbers of samples, a solid-phase sandwich hybridization system readily applicable to the detection of PCR products has been designed. This colorimetric detection system relies on the use of polybiotinylated detection probes and of specific capture oligonucleotides covalently linked at allocated positions on nylon membrane strips. From a phylogenetic analysis on a great number of ospA gene sequences, we have designed and synthesized a set of PCR primers specific to the five Borrelia burgdorferi sensu lato genospecies present in Europe and a subset of probes (capture and detection probes) specific to these five genospecies . This combined PCR hybridization system was evaluated with a large number of various B. burgdorferi isolates and clinical specimens. These analyses clearly showed that the system could be used as a typing method to distinguish five genospecies belonging to the B. burgdorferi sensu lato complex. In addition, the study showed that B. valaisiana strains might be more heterologous than suspected up to now and clustered into three genomic groups.
Eight ixodid tick species, associated with 59 free-ranging mammals belonging to 10 species, were ... more Eight ixodid tick species, associated with 59 free-ranging mammals belonging to 10 species, were collected at five different localities in the Free State Province, South Africa. Four of the study areas were nature reserves (Willem Pretorius, Sandveld, Tussen-die-Riviere, and Soetdoring), and one site was a private farm located in Senekal district. The collection was performed from March 2006 until June 2006. Ticks (n5569) and tissues from animals (n552) were analyzed by polymerase chain reaction, reverse line blot, and sequencing for various tickborne pathogens belonging to the genera Babesia, Theileria, Anaplasma, and Ehrlichia. Rhipicephalus (Boophilus) microplus, the known vector of Babesia bovis responsible for Asiatic redwater in South Africa, was found for the first time in the Free State Province. Rhipicephalus appendiculatus also was collected in areas in the Free State where it has not been previously described. Anaplasma marginale was detected for the first time in a gemsbok (Oryx gazella gazella). Gene sequences recovered in this study were 98-100% homologous with GenBank sequences for Anaplasma bovis, Theileria separata, and Theileria sp. Malelane sable antelope.
The vector-to-host and host-to-vector transmission steps are the two critical events that define ... more The vector-to-host and host-to-vector transmission steps are the two critical events that define the life cycle of any vector-borne pathogen. We expect negative genetic correlations between these two transmission phenotypes, if parasite genotypes specialized at invading the vector are less effective at infecting the vertebrate host and vice versa. We used the tick-borne bacterium Borrelia afzelii, a causative agent of Lyme borreliosis in Europe, to test whether genetic trade-offs exist between tick-to-host, systemic (host-to-tick), and a third mode of co-feeding (tick-to-tick) transmission. We worked with six strains of B. afzelii that were differentiated according to their ospC gene. We compared the three components of transmission among the B. afzelii strains using laboratory rodents as the vertebrate host and a laboratory colony of Ixodes ricinus as the tick vector. We used next generation matrix models to combine these transmission components into a single estimate of the reprod...
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