Borrelia burgdorferi, the etiological agent of Lyme disease, comprises three genospecies, Borrelia garinii, afzelii, and burgdorferi sensu strictu, that exhibit different pathogenicity and differ in the susceptibility to C-mediated killing. We examined C-sensitive and C-resistant strains of B. burgdorferi for deposition of C3 and late C components by fluorescence microscope and flow cytometry. Despite comparable deposition of C3 on the two strains, the resistant strain exhibited reduced staining for C6 and C7, barely detectable C9, and undetectable poly C9. Based on these findings, we searched for a protein that inhibits assembly of C membrane attack complex and documented an anti-human CD59-reactive molecule on the surface of C-resistant spirochetes by flow cytometry and electron microscopy. A molecule of 80 kDa recognized by polyclonal and monoclonal anti-CD59 Abs was identified in the membrane extract of C-resistant strains by SDS-PAGE and Western blot analysis. The molecule was released from the bacterial wall using deoxycholate and trypsin, suggesting its insertion into the bacterial membrane. The CD59-like molecule acts as C inhibitor on Borrelia because incubation with F(ab′)2 anti-CD59 renders the serum-resistant strain exquisitely susceptible to C-mediated killing and guinea pig erythrocytes bearing C5b-8, unlike the RBC coated with C5b-7, are protected from reactive lysis by the bacterial extract. Western blot analysis revealed preferential binding of the C inhibitory molecule to C9 and weak interaction with C8β.
Guinea-pig macrophages exerted no bactericidal activity against either a virulent or a saprophytic strain of leptospira during a 120 min period of contact at 37 OC. However, the same macrophages exhibited weak phagocytic powers towards these two strains of leptospira over a similar period of time.
Eighteen patients involved in a localized outbreak of leptospirosis were subjected to a serological follow-up study over a 5-year period. Four distinct sets of sera from all patients and a fifth sample obtained from 10 of them were examined by the microscopic agglutination test (MAT) for demonstration of leptospiral antibodies. The test was carried out by using live leptospires from reference strains of 17 Leptospira interrogans serovars known to occur in Italy. In all cases, the highest titers of agglutinins were recorded against one or more of the three Australis group serovars tested (australis, bratislava, and lora). The highest antibody levels were reached soon after the acute phase of infection in some patients but only after some months in others. Titers then tended to recede with varying rapidity, but titers against the Australis group serovars were still detectable in some patients after 5 years. Coagglutinins against serovars of other serogroups were detected, generally at low levels, in the early sets of sera of most patients, but tended to disappear in the late-set sera. Specific immunoglobulin M (IgM) and IgG against the three Australis group serovars were determined in most serum samples from 16 patients by solid-phase enzyme immunoassay (EIA). In general, EIA titers were considerably lower than MAT titers, but there was a certain patient-to-patient variability in both the IgM/lgG ratio and the evolution and persistence of the two immunoglobulin classes. Since all the evidence indicated that the initial outbreak was from a single source, the observed patient-to-patient variability in the progress of both MAT and EIA titers appeared to be attributable to factors inherent in the individual patients. Cross agglutination absorption tests, aimed at retrospectively determining to which of the Australis group serovars the outbreak-specific infecting strain belonged, were performed with six serum samples from different patients. Most absorbed sera seemed to originate from an australis or lora infection, but it was not possible to discriminate conclusively between the two serovars.
This study was carried out using Ixodes ricinus ticks collected during 2005 and 2006 from the Friuli Venezia Giulia (FVG) region in the northeastern part of Italy and an area along the Slovenian side of the western border of Italy. The results indicate that Rickettsia spp. is widely distributed throughout these areas, with the greatest prevalence in the central part of the FVG region. The prevalence of Rickettsia spp. was 4.5% during 2005 and 6.1% during 2006. By sequencing the 16S rRNA gene, we show for the first time the presence of Rickettsia helvetica in I. ricinus ticks in the FVG region and the presence of R. monacensis in ticks in both areas. Furthermore, we detected a sequence with a high homology with that of R. limoniae in a tick obtained from the alpine zone.
This paper describes the interactions between a strain of Borrelia burgdorferi and phagocytic cells, measured in whole blood, by a two-color flow cytometric method, which allowed the simultaneous quantification of both the phagocytosis rate and the oxidative burst activation. The data obtained indicated that: a) phagocytosis and metabolic activation increased as a function of spirochete concentration; b) the number of ingesting cells peaked within 10 min but activation followed later, and did not involve all the phagocytosing cells; c) opsonization of borreliae with a patient's serum enhanced the two cellular activities, mostly phagocytosis. The intensity of such functions was lower than those found for Staphylococcus aureus. The flow cytometric assay of phagocytes interactions with Borrelia burgdorferi assessed in whole blood represents an experimental approach which simulates the physiological conditions in nature.
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