Emerging Tickborne Bacteria in Cattle from Colombia.

Ehrlichia minasensis is a new pathogenic bacterial species that infects cattle, and Borrelia theileri causes bovine borreliosis. We detected E. minasensis and B. theileri DNA in cattle from southwestern Colombia by using PCR. E. minasensis and B. theileri should be considered potential etiologies of febrile syndrome in cattle from Colombia.

Identification of a T-Cell Epitope That Is Globally Conserved among Outer Membrane Proteins (OMPs) OMP7, OMP8, and OMP9 of Anaplasma marginale Strains and with OMP7 from the A. marginale subsp. centrale Vaccine Strain.

Within the protective outer membrane (OM) fraction of Anaplasma marginale, several vaccine candidates have emerged, including a family of OM proteins (OMPs) 7 to 9, which share sequence identity with each other and with the single protein OMP7 in the vaccine strain A. marginale subsp. centrale. A. marginale OMPs 7 to 9 are logical vaccine candidates because they are surface exposed, present in the OM immunogen and protective cross-linked OM proteins, recognized by immune serum IgG2 and T cells in cattle immunized with OM, and recognized by immune serum IgG2 from cattle immunized with the A. centrale vaccine strain. We report the identification of a globally conserved 9-amino-acid T-cell epitope FLLVDDAI/VV shared between A. centrale vaccine strain OMP7 and the related A. marginale OMPs 7 to 9, where position 8 of the peptide can be isoleucine or valine. The epitope is conserved in American A. marginale strains, in the Australia Gypsy Plains strain, and in multiple field isolates from Ghana. This epitope, together with additional T-cell epitopes that are present within these proteins, should be considered for inclusion in a multivalent vaccine for A. marginale that can provide protection against disease caused by globally distributed bacterial strains.

Caso probable de fiebre manchada ( Rickettsia felis) transmitida por pulgas / Probable case of flea-borne spotted fever ( Rickettsia felis )

Rickettsia felis es el agente etiológico de la fiebre manchada transmitida por pulgas, cuyo principal vector y reservorio es Ctenocephalides felis . Típicamente, la enfermedad se presenta como fiebre aguda asociada a cefalea, astenia, exantema máculo-papular generalizado y, en algunos casos, con escara de inoculación. En los últimos años, R. felis ha venido adquiriendo un papel importante en la etiología del síndrome febril agudo, calificándola como una enfermedad emergente y subdiagnosticada. La inmunofluorescencia indirecta es actualmente el método diagnóstico de referencia. Sin embargo, esta técnica presenta limitaciones relacionadas con la reacción cruzada que existe entre las diferentes especies del género Rickettsia . En el presente reporte se describe el caso de un paciente de 16 años con síndrome febril agudo secundario a infección probable por R. felis .

Rickettsia felis is the etiologic agent of flea-borne spotted fever, with Ctenocephalides felis as its main vector and reservoir. Typically, the disease presents as acute fever associated with headache, asthenia, generalized maculo-papular rash, and in some cases, an inoculation eschar. In recent years, R. felis has acquired an important role in the etiology of the acute febrile syndrome; it is indeed an emerging infectious disease, albeit underdiagnosed. Indirect immunofluorescence assay (IFA) is currently the reference diagnostic method. However, this technique has limitations related to the cross reactivity among different species of rickettsiae. Herein, we describe a case of a 16 year-old patient with an acute febrile syndrome secondary to probable infection with R. felis.

[Probable case of flea-borne spotted fever (Rickettsia felis)]. / Caso probable de fiebre manchada (Rickettsia felis) transmitida por pulgas.

Rickettsia felis is the etiologic agent of flea-borne spotted fever, with Ctenocephalides felis as its main vector and reservoir. Typically, the disease presents as acute fever associated with headache, asthenia, generalized maculo-papular rash, and in some cases, an inoculation eschar. In recent years, R. felis has acquired an important role in the etiology of the acute febrile syndrome; it is indeed an emerging infectious disease, albeit underdiagnosed. Indirect immunofluorescence assay (IFA) is currently the reference diagnostic method. However, this technique has limitations related to the cross reactivity among different species of rickettsiae. Herein, we describe a case of a 16 year-old patient with an acute febrile syndrome secondary to probable infection with R. felis.

Ecología y epidemiología del Gusano Barrenador del Ganado, Cochliomyia hominivorax (Coquerel, 1858) / Ecology and epidemiology of screwworm, Cochliomyia Hominivorax (Coquerel, 1858)

La miasis por cochliomyia hominivorax se caracteriza por áreas manchadas con exudados sanguinolentos alrededor de las heridas de los animales. Sus efectos patológicos van desde la irritación mecánica por la alimentación de las larvas hasta la muerte del hospedero en infestaciones sucesivas. En condiciones naturales, las densidades de las poblaciones de la mosca del Gusano Barrenador del Ganado son bajas. Se distribuyen en relación con los cursos de agua, la proximidad de hospederos potenciales y la densidad de la vegetación. Los climas húmedos y calientes favorecen el incremento de las poblaciones del gusano Barrenador del ganado. Dentro de los animales domésticos, la principal especie afectada es la bovina. Los factores de riesgo en los animales están relacionados, principalmente, con prácticas de manejo. En seres humanos, los niños y los ancianos, en condiciones de abandono y desaseo, son los individuos más vulnerables.Se señalan algunos aspectos técnicos que deben ser analizados en la planeación de estudios ecológicos y epidemiológicos en Colombia...

Deletion of donor-reactive cells as a new conditioning regimen for allogeneic bone marrow transplantation.

Progress in the development of less toxic conditioning for bone marrow transplantation (BMT) came with the understanding that acceptance of mismatched BM does not require myeloablation of recipients. Lymphocyte deletion by a cocktail of immunosuppressive drugs is generally sufficient to ensure engraftment of compatible BM cells. However, reduced intensity conditioning (RIC) protocols available today do not provide robust tolerance to mismatched allogeneic BM. Herein we discuss 2 new experimental approaches to RIC protocols with the aim of facilitating allogeneic BM engraftment. Both conditioning regimens are based on selective deletion/inactivation of donor-reactive cells before BMT. Our data show that the first conditioning protocol, comprising priming of recipients by a donor-specific lymphocyte transfusion (DST) on day -2 and a single injection of cyclophosphamide, a drug that is predominantly toxic for proliferating cells, on day -1, consistently improves engraftment of allogeneic BM (day 0) in all experimental models tested. The second engraftment enhancing approach is based on the blockade by antagonistic reagents of the signaling pathways that govern the antigen-induced immune response. Combining the signaling blockade with the deletion of activated donor-reactive cells by cytoreductive agents provides additional benefits for transplantation across major histocompatibility barriers.

Repression of MHC class II gene transcription in trophoblast cells by novel single-stranded DNA binding proteins.

The maintenance of the fetus during pregnancy has been attributed to the absence of major histocompatibility complex (MHC) class II antigens on fetal trophoblastic cells that make contact with the maternal immune system. However, the mechanism(s) by which class II genes are regulated in trophoblast cells is unclear. We have identified a negative regulatory element (IA alpha NRE) in the promoter of the mouse class II gene IA alpha that represses IA alpha transcription in trophoblast cells. IA alpha NRE, located from-839 to -828, binds transacting factors from rat, mouse and human trophoblast cells, but not from 18 other cell lines tested. These results indicate that IA alpha NRE binding proteins (IA alpha NRE BPs) are conserved in species with hemochordial placentas, and suggest that IA alpha NRE binding activity is restricted primarily to trophoblast cells. Interestingly, the IA alpha NRE BPs bind to the IA alpha NRE antisense strand in a sequence-specific manner. IA alpha NRE represses transcription from the IA alpha promoter in a position-dependent manner, and has a minor down-regulatory effect on the activity of the SV40 promoter/enhancer. Our results demonstrate that MHC class II gene transcription is repressed in fetal trophoblast cells by sequence-specific, single-stranded DNA binding proteins, and suggest a possible mechanism by which the conceptus is protected from immune rejection during pregnancy.

Effects of mechanical trauma and free-radical exposure on the membrane-integrity of Ehrlich ascites tumor cells.

During hematogenous metastasis, the majority of cancer cells entering the microcirculation are rapidly killed as a consequence of loss of membrane integrity. This is partially due to mechanical trauma associated with intramicrovascular cancer cell deformation, and possibly to the action of free radicals released by endothelial and other cells. In an in vitro analysis of these two modalities, we have studied the effects of mechanical (filtration) trauma and exposure to hydrogen peroxide on the surface membrane integrity of Ehrlich ascites tumor cells. It was shown that final concentrations of H2O2 down to 0.001%, and filtration through 10 microns Nuclepore each produced significant loss in surface membrane integrity. An additive effect was demonstrated between exposure to 0.001% H2O2 and filtration, but the additive effect was not detectable at 0.01%. Overall, the results indicate the feasibility of trauma due to mechanical deformation and exposure to free radicals, contributing to the inefficiency of the metastatic process.

The differential resistance of B16 wild-type and F10 cells to mechanical trauma in vitro.

Following intravenous injection of B16 melanoma cells into mice, more than 99.9% of the cells are killed by a combination of rapid and slow processes: however, the F10 line of B16 mouse melanoma cells produces approximately 10 times as many pulmonary colonies as wild-type cells. We have attempted to determine the role of one rapid cancer cell-killing process, namely deformation-driven, loss of surface membrane integrity of the type occurring in capillaries, by the use of an in vitro model in which cells are filtered through 8-microns pores in polycarbonate membranes. In accord with in vivo observations, more wild-type than F10 cells were killed by filtration in vitro. The hypothesis that resistance to mechanical trauma of this type is enhanced by a small cell diameter and a high degree of surface rugosity is supported by measurements of these parameters on viable cells and electron micrographs. Differential resistance in these cells is associated to a major extent with a high degree of utilizable surface membrane excess, and to a minor extent with the smaller mean diameter of the F10 cells. Calculations, which are in accord with previous in vivo observations, indicate that most of the cells delivered to the capillary beds of target organs during hematogenous metastasis can be destroyed by rapid mechanical trauma, which is therefore implicated as one of a number of major contributors to metastatic inefficiency.

Effects of doxorubicin on the sensitivity of L1210 leukemia cells to deformation-associated trauma.

Most of the cancer cells arrested in the microcirculation during hematogenous metastasis are rapidly killed; one major mechanism is surface-membrane rupture, associated with the mechanical deformation of cancer cells in capillaries. The feasibility of increasing the susceptibility of cancer cells to lethal, deformation-associated trauma by doxorubicin, was tested in an in vitro mechanical model system, by filtering suspensions of L1210 leukemia cells through 8-microns pore-size Nuclepore membranes, with or without prior incubation with 10(-7)M doxorubicin. The results showed that mechanically-induced loss of cancer cells immediately after filtration was increased from 18 to 55% in cells previously exposed to doxorubicin for 48 h. The results indicate the feasibility of chemotherapeutic enhancement of the mechanical killing-action of the microvasculature as a potential rate-regulator of hematogenous metastasis.

Effects of cytoskeletal perturbation on the sensitivity of Ehrlich ascites tumor cell surface membranes to mechanical trauma.

Evidence presented previously indicated that shape changes in circulating cancer cells within the microvasculature may lead to rapid, lethal rupture of the cell surface membranes, thereby contributing to the inefficiency of this phase of hematogenous metastasis. As the cytoskeleton is known to regulate cell shape and, in at least some cases, to be attached to the surface membrane, we have determined whether or not it plays a role in inhibiting lethal, deformation-associated, mechanically induced surface membrane trauma. Thus, Ehrlich ascites tumor (EAT) cells were treated with different cytoskeleton-perturbing agents, and their susceptibility to filtration trauma on passage through Nuclepore membranes was determined. In contrast to the involvement of the cytoskeleton in nonlethal cell deformation, agents which disrupt intracellular networks of microtubules, microfilaments and intermediate filaments had little or no direct effect on EAT cell susceptibility to rapid, mechanically induced, lethal trauma.

Measurements of compression of Ehrlich ascites tumor cells and their relevance to hematogenous metastasis.

Ehrlich ascites cancer cells were compressed between glass microscope slides by the addition of weights. The projected areas of the cells were measured, and their surface membrane integrity determined by means of trypan-blue exclusion tests under different compression loads of 0 to 800g. The results are compatible with a two-step mechanism for surface rupture; first the cell membrane is unfolded and then stretched, with modest degrees of stretching associated with membrane rupture. It is calculated that lethal surface membrane rupture of the type produced here by compression, could also be produced when cancer cells are deformed by entry and passage along relatively non-deformable capillaries. This would at least partially account for the rapid destruction of cancer cells in the microcirculation. The observation that isolated nuclei are less deformable than whole cells, may indicate that their nuclei may protect cancer cells from biomechanical trauma.

Mechanisms for the biomechanical destruction of L1210 leukemia cells: a rate regulator for metastasis.

Mechanical trauma appears to be one significant cause of the rapid intravascular death of cancer cells and, as such, could act as an important rate regulator for the metastatic process. Intravascular mechanical trauma to cancer cells is thought to be a consequence of shape transitions, occurring when they are deformed from spherical shape by entry into, and passage along, capillaries having smaller diameters than themselves. These transitions from spherical shape require increases in surface area; first, an apparent increase in surface area is accomplished by a reversible, nonlethal surface membrane unfolding. If this is insufficient to meet geometric demands, it is followed by a true increase in surface area, resulting in increased tension in the cancer cell surface membrane, leading to its lethal rupture.

Mechanism of mechanical trauma to Ehrlich ascites tumor cells in vitro and its relationship to rapid intravascular death during metastasis.

Many, if not most, of the cancer cells arrested in the microvasculature during metastasis appear to be rapidly killed by mechanical trauma, associated with shape-transitions, which require increases in cell surface area. The hypothesis has been advanced that such increases in surface area occur in 2 phases: First, there is an apparent increase due to surface unfolding, which is reversible and non-lethal. Second, there is a true increase, during which cell surface membranes are stretched, with an increase in membrane tension. When tension exceeds a critical level, the surface membranes rupture and this irreversible change is lethal. In the present study, cell surface area has been incrementally increased by a hypotonic environment. Down to approximately 70 mM/kg, a reversible, non-lethal increase in cell volume was observed, associated with electron microscopic evidence of unfolding. At and below 70 mM/kg, irreversible, lethal changes occurred, associated with increased susceptibility to the mechanical trauma associated with membrane-filtration. These observations are consistent with the hypothesis in question.