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At least 19 recordsLinked to original sources
PubMed1990

Isolation and characterization of a gene associated with a virulent strain of Babesia microti.

Babesia microti genomic DNA was purified from parasitized murine erythrocytes, digested with mung bean nuclease and used to construct an expression library in lambda gt11. Polyspecific antisera from mice infected with virulent B. microti organisms (ATCC30221) were used to screen the genomic library for genes encoding major immunogens. High titer antisera selected a recombinant phage, Bm13, containing 3.3 kb of B. microti DNA. Hybridization analysis confirmed the parasite origin of the clone; affinity-purified antibody revealed a native molecular weight of 54,000 for the B. microti protein encoded by the recombinant. Only genomic DNA isolated from the virulent strain of B. microti contained sequences which hybridized to Bm13. Genomic DNA prepared from the Peabody attenuated strain of B. microti or from Babesia bovis DNA did not contain any complementary sequences. These data suggest a possible role for the gene in the virulence of the organism.

Animals↗
PubMed2003

What is Babesia microti?

Babesia microti (Apicomplexa: Piroplasmida) has historically been considered a common parasite of Holarctic rodents. However, human babesiosis due to this species has generally been limited to the northeastern seaboard of the United States and Minnesota and Wisconsin. The absence of reports of B. microti babesiosis from sites where the agent is enzootic, such as in western Europe, remains unexplained. Previous work focusing on the 18S rDNA demonstrates little sequence diversity among samples from allopatric host populations across a wide geographical area. It may be that genetic diversity is underestimated due to sample size or the gene analysed. Accordingly, we collected blood or spleen samples from American or Eurasian animals with parasites that were morphologically consistent with B. microti, amplified the 18S rDNA and beta-tubulin gene, and conducted phylogenetic analysis. Surprisingly, what was considered to be 'B. microti' by microscopy appears to be a diverse species complex. We identify 3 distinct clades within this complex, including parasites from non-rodent hosts. Rodent parasites comprise 2 clades, one representing zoonotic isolates, and the other apparently maintained in microtine rodents, and therefore their morphological detection within animals from a site does not necessarily imply a risk to public health.

Animals↗
PubMed1992

Changes of splenic lymphocyte subpopulation in mice inoculated with Babesia microti and Babesia rodhaini.

Changes of splenic lymphocyte subpopulation after Babesia microti and Babesia rodhaini inoculation in mice were examined by flow cytometric analysis. The B. microti inoculated mice showed a longer period of time from inoculation to the onset of increase or decrease parasitaemia (%), packed cell volume, total spleen cell numbers and surface immunoglobulin positive splenic cell numbers than respective periods in B. rodhaini inoculated mice. The Thy-1 positive cell numbers in B. microti inoculated mice and B. rodhaini inoculated mice pre-immunized with homologous parasites were significantly higher than that of B. rodhaini inoculated mice. The ratio of L3T4 positive cell/Lyt-2 positive cell after inoculation with B. microti was quite similar to that in B. rodhaini mice pre-immunized. However, the ratio in B. rodhaini inoculated mice revealed a lack of an increasing phase. These results suggested that the T-cell dependent early immune response, especially suppressor activity, was closely related to the difference in the course of infection between the non-lethal B. microti and the lethal B. rodhaini infection in mice.

Animals↗
PubMed1998

Mitochondrial function in Babesia microti and Babesia rodhaini.

The role of mitochondria in the energy metabolism of Babesia microti and Babesia rodhaini was investigated. A variety of mitochondrial inhibitors showed greater sensitivity to B. microti than to B. rodhaini. Additionally, alpha-glycerophosphate- and succinate-cytochrome c reductase activities in the crude mitochondrial fraction from B. microti were substantially higher than those from B. rodhaini. Our results suggest that the mitochondria of these parasites possess a series of "classical" apparati for energy production and their relative functional role may be quantitatively greater in B. microti when compared with B. rodhaini.

ATP Synthetase Complexes↗
PubMed1995

Enzyme activities related to glucose metabolism in Babesia microti and Babesia rodhaini.

A comparative study was carried out on the glucose metabolism in Babesia microti (BM) and Babesia rodhaini (BR) by analyzing the enzyme activities. The lactate dehydrogenase (LDH) activity in BM showed significantly lower values than that in BR, whereas citrate synthase (CS) and malate dehydrogenase (MDH) activities were remarkably higher in BM. In addition, pyruvate dehydrogenase (PDH), isocitrate dehydrogenase (ICDH), alpha-ketoglutarate dehydrogenase (KGDH), and succinate dehydrogenase (SDH) activities also tended to be higher in BM. Then, the change of enzyme activities related to the proliferation of parasites was examined. In BM infected mice, the parasitemia increased from day 15 to day 19 after inoculation (a.i.). While BM showed decrease of G6PD and LDH activities at day 19 a.i., it showed remarkably increased activities in CS and MDH (368 and 8,842 nmol/min.mg protein, respectively). In addition, PDH, ICDH, KGDH, and SDH activities also tended to increase from day 15 to 19 a.i. In BR infected mice, parasitemia increased from day 9 to day 12 a.i. LDH activity showed a considerable increase at day 12 a.i. (12,920 IU/mg.protein). Although CS and MDH activities also showed a slight increase at day 12 a.i., the activities of PDH, ICDH, KGDH and SDH didn't change from day 9 to 12 a.i. Since these changes observed in the enzyme activities of BM and BR seemed to be correlated with their proliferation, it was suggested that BM and BR depended on aerobic and anaerobic pathways, respectively, for their glucose metabolism.

Animals↗
PubMed1992

Babesia bovis, Babesia bigemina, Babesia canis, Babesia microti and Babesia rodhaini: comparison of ribosomal RNA gene organization.

The three ribosomal DNA (rDNA) units have been cloned from an Australian isolate of Babesia bigemina. The organization of the units is very similar to that reported for a Mexican isolate of B. bigemina. In Babesia canis four rDNA units have been identified. Both Babesia rodhaini and Babesia microti contain two different rDNA units. A small number of different rDNA units appears to be a common feature of this group of Protozoa. Restriction enzyme analysis of the rDNA units form these species and B. bovis suggests that the genus Babesia as currently defined does indeed include two distinct groups of organisms namely, B. bovis, B. bigemina and B. canis and B. rodhaini and B. microti.

Animals↗
PubMed2001

Isolation and amplification by polymerase chain reaction DNA of Babesia microti and Babesia divergens in ticks in Poland.

Babesia microti and B. divergens, the etiological agents of human babesiosis, are transmitted by the bite of Ixodes ricinus. The purpose of this study was differentiation of those two species in ticks collected in urban woods in the city Szczecin (north-western Poland). The prevalence of the DNA of Babesia were investigated by PCR amplification with primers to the fragment from a gene encoding the nuclear small-subunit ribosomal RNA (SS-rDNA). We examined a total of 533 specimens of Ixodes ricinus. The mean infection rate was 16.3%. Our results indicate that a B. microti and B. divergens--specific PCR test may provide a sensitive tool also for the laboratory diagnosis of human babesiosis.

Animals↗
PubMed1996

Effects of depletion of T cell subpopulations on the course of infection and anti-parasite delayed type hypersensitivity response in mice infected with Babesia microti and Babesia rodhaini.

To elucidate the role of T cell subpopulations in the protective cell-mediated immune response at the initial phase of infection with Babesia microti (BM) and B. rodhaini (BR), the changes in the course of infection and anti-parasite delayed type hypersensitivity (DTH) response after BM or BR inoculation were investigated in Lyt-2+ T cell or L3T4+ T cell-depleted mice. Depletion of Lyt-2+ T cells strongly enhanced the resistance to BM infection, whereas it increased the susceptibility to BR infection. In contrast, depletion of L3T4+ T cells increased susceptibility to BM infection, while it enhanced resistance to BR infection. The anti-parasite DTH response in BM-infected mice was significantly enhanced by depletion of Lyt-2+ T cells, while significantly reduced by depletion of L3T4+ T cells. No effects of depletion of either Lyt-2+ or L3T4+ cells on DTH response was observed in BR-infected mice. From these results, it was suggested that the roles of Lyt-2+ and L3T4+ T cells in the protective cell-mediated immune response at the initial phase of infection were different between BM- and BR-infected mice, resulting in the difference in their course of infection.

Animals↗
PubMed2004

Glucose uptake activity in murine red blood cells infected with Babesia microti and Babesia rodhaini.

The glucose uptake activity in Babesia rodhaini and B. microti - infected red blood cell (IRBC) was investigated in mice using 2-deoxy-D-glucose (2DOG) and L-glucose (L-Glc), a non-metabolizable analogue of D-glucose and non-incorporative glucose to non-infected RBC (NRBC), respectively. The uptake activities of both DOG and L-Glc were higher in IRBCs than those in NRBC. The concentration dependent uptake of 2DOG and L-Glc in both IRBC revealed a linear curve, indicating non-transporter mediated uptake. In addition, B. microti IRBC showed higher 2DOG uptake than B. rodhaini IRBC, whereas no difference was observed in L-Glc uptake. These results indicated that some new glucose uptake system, at least two systems, developed in both IRBC. The new systems were sodium independent, non-competitive to L-Glc, and sensitive to temperature. One of two systems had no kinetical difference between B. rodhaini and B. microti IRBC, however another one might have higher uptake activity in B. microti IRBC compared to that in B. rodhaini IRBC.

Animals↗
PubMed1993

Protective immune response of Isospora felis-infected mice against Babesia microti infection.

Protective response against Babesia microti was studied in Isospora felis-infected mice. Isospora felis-infected mice which were exposed to B. microti on the 28th day post-infection showed absolute resistance against Babesia microti. Interestingly, these mice showed no anti-B. microti antibodies. Mice that received spleen cells from I. felis-infected donors that were subsequently exposed to B. microti showed lower peak parasitemia (10.3% +/- 2.6) compared to those mice that received normal spleen cells (60.9% +/- 15.0), and no spleen cells at all (47.3% +/- 8.5). Treatment of I. felis-infected mice with monoclonal antibodies against L3T4+ cells resulted to a depression of their resistance to B. microti, as clearly manifested by high levels of parasitemia. Findings of the present study demonstrate the role of cell mediated immunity, specifically by L3T4+ T-cells induced by I. felis infection, in providing mice protection against B. microti.

Animals↗
PubMed2003

Roles of the Maltese cross form in the development of parasitemia and protection against Babesia microti infection in mice.

Babesia microti, a hemoprotozoan parasite of rodents, is also important as a zoonotic agent of human babesiosis. The Maltese cross form, which consists of four masses in an erythrocyte, is characteristic of the developmental stage of B. microti. Monoclonal antibody (MAb) 2-1E, which specifically recognizes the Maltese cross form of B. microti, has been described previously. In the present study, we examined the roles of the Maltese cross form during the infectious course of B. microti in mice. The number of the Maltese cross form increased in the peripheral blood of infected mice prior to the peak of parasitemia. With confocal laser scanning microscopy, MAb 2-1E was found to be reactive with the ring form, with the parasites undergoing transformation to the Maltese cross form and subsequent division, and also with extracellular merozoites. Furthermore, the Maltese cross form-related antigen (MRA) gene was isolated from a B. microti cDNA library by immunoscreening with MAb 2-1E, and the nucleotide sequence was determined. Genomic analyses indicated that the MRA gene exists as a single-copy gene in B. microti. Immunization of mice with recombinant MRA induced significant protective immunity against B. microti infection. These findings indicate that the Maltese cross form plays important roles in both the development of parasitemia and the protective response against the infection.

Amino Acid Sequence↗
PubMed2003

Evidence of Babesia microti infection in multi-infected Ixodes persulcatus ticks in Russia.

To detect Babesia-infected Ixodes persulcatus Shulze in a suburb of St. Petersburg, Russia, 738 adult ticks were studied using Babesia specific primers and PCR techniques. The entire sample (more than 1,200 individuals) was screened for the presence of Borrelia spp., Ehrlichia spp. and tick-borne encephalitis virus (TBEV). All 7 ticks infected with Babesia microti, were also infected with other pathogens (all 7 among 417 infected ticks, zero amongst the remaining 321 naive ones (chi2 = 5.25, p<0.05). Babesia microti occurred twice with Borrelia afzelii, 3 times with Borrelia garinii, once with both, and once with both B. garinii and TBEV. The prevalence of infection with Borrelia spp. was 34.0%, with Ehrlichia spp. 6.2%, with TBEV 1.5%, and with Ba. microti 0.9%. Babesia microti infection was not found in combination with Ehrlichia sp. or Borrelia burgdorferi sensu stricto. The latter pathogen (prevalence 2.6%), just like Ba. microti, was not encountered as a monoinfection. The data suggest that Ba. microti infection can only survive in I. persulcatus in combination with Borrelia spp. (7 of 7 infections). The disease in humans is more severe and longer-lasting when more than one pathogen is involved. Our observations show that the well known St. Petersburg focus of tick-borne encephalitis and Lyme disease is also a focus of ehrlichiosis and babesiosis.

Animals↗
PubMed1996

Acute fulminating babesiosis in hamsters infected with Babesia microti.

In this study, Babesia microti (ATCC30222) from mice was adapted to golden hamsters. The parasite was passaged to immunosuppressed and then adapted to normal hamsters. When 30 normal hamsters were inoculated with this strain, parasitaemia increased to 74% of erythrocytes by day 7 and 70% of the hamsters died. By day 12, parasitaemia extended to 90%, with 97% mortality. Hearts and kidneys from infected animals were enlarged. Histopathology revealed acute myocarditis, hepatitis, pneumonitis, glomerulonephritis and splenomegaly. Giemsa, Acridine Orange and Rhodamine staining of the parasite were compared. Scanning electron microscopy of blood from infected hamsters revealed from 1 to 5 intra-erythrocytic parasites.

Acute Disease↗