Infection and Transformation of Bovine Lymphoid Cells in vitro by Infective Particles of Theileria parva
TL;DR: Techniques recently developed in this laboratory can be used to infect cattle reproducibly with East Coast fever with infective particles of Theileria parva collected from the tick vector, Rhipicephalus appendiculatus.
Abstract: Infection and Transformation of Bovine Lymphoid Cells in vitro by Infective Particles of Theileria parva
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TL;DR: A selection of the mechanisms serves to illustrate the challenge involved in developing strategies for immunising against parasites.
Abstract: Parasites have evolved an extraordinary variety of mechanisms for surviving in the face of the natural and acquired immune responses of their hosts. A selection of the mechanisms serves to illustrate the challenge involved in developing strategies for immunising against parasites.
207 citations
TL;DR: The presence of the parasite in the host-cell cytoplasm modulates the state of activation of a number of signal transduction pathways, including nuclear factor-kappa B, which appear to be essential for the survival of Theileria-transformed T cells.
Abstract: Theileria parva and T. annulata provide intriguing models for the study of parasite-host interactions. Both parasites possess the unique property of being able to transform the cells they infect; T. parva transforms T and B cells, whereas T. annulata affects B cells and monocytes/macrophages. Parasitized cells do not require antigenic stimulation or exogenous growth factors and acquire the ability to proliferate continuously. In vivo, parasitized cells undergo clonal expansion and infiltrate both lymphoid and non-lymphoid tissues of the infected host. Theileria-induced transformation is entirely reversible and is accompanied by the expression of a wide range of different lymphokines and cytokines, some of which may contribute to proliferation or may enhance spread and survival of the parasitized cell in the host. The presence of the parasite in the host-cell cytoplasm modulates the state of activation of a number of signal transduction pathways. This, in turn, leads to the activation of transcription factors, including nuclear factor-kappa B, which appear to be essential for the survival of Theileria-transformed T cells.
161 citations
TL;DR: Methods of integrated control are suggested and discussed in light of recent development in control methods and those still under development and encouragement is given to attempt this approach in Africa to solve what must be the largest animal health problem of livestock remaining in the world.
Abstract: The problems caused by tick and tick-borne diseases for livestock particularly cattle on the African continent are described and discussed. The control of ticks and tick-borne diseases must receive high priority in Africa with regard to both research and control application because of their widespread distribution in areas of high livestock potential and productivity. The conventional methods of tick and tick-borne disease control are discussed and are found to be inadequate in the conditions prevailing in Africa. Methods of integrated control are suggested and discussed in light of recent development in control methods and those still under development. Any one of these methods may not be adequate to control the problem on its own but when several of the methods are combined an economic and robust integrated control is likely to result. Encouragement is given to attempt this approach in Africa to solve what must be the largest animal health problem of livestock remaining in the world.
158 citations
TL;DR: Findings provide direct evidence that CD8+ T cells can control T. parva infections in immune cattle and enable adoptive transfer of this activity between immune and naive monozygotic twin calves.
Abstract: Evidence that class I major histocompatibility complex-restricted cytotoxic T lymphocytes (CTL) are involved in immunity to malaria has highlighted the potential importance of these cells in protection against intracellular parasites. Parasite-specific CTL are a prominent feature of the immune response of cattle to Theileria parva, a related apicomplexan parasite. The relationship between the appearance of these cells in the blood of immune cattle under challenge and the clearance of infection suggests that they are involved in the control of infection, but direct evidence is lacking that CTL can mediate protection. We have made a quantitative kinetic study of CTL responses in lymph originating from infected lymph nodes in a number of immune cattle under challenge with T. parva. Direct killing activity and the frequency of CTL precursors (CTLp) within responding cell populations were evaluated. A substantial increase in the proportion of CD8+ CTL was observed between days 8 and 11 after challenge. Frequencies of CTLp as high as 1:32 were observed and activity was essentially confined to the large blasting cell fraction. The analogous response in peripheral blood was of lower magnitude and delayed by 1-2 days. The high frequency of CTLp in efferent lymph permitted the adoptive transfer of this activity between immune and naive monozygotic twin calves. In separate experiments, naive calves lethally infected with T. parva were protected by inoculation of up to 10(10) responding CD8+ T cells derived from their immune twins. Elimination of CD8+ T cells within the inoculum abrogated this effect. These findings provide direct evidence that CD8+ T cells can control T. parva infections in immune cattle.
133 citations
TL;DR: The Barham Arctic Structure Soil and the associated Barham Loess were formed during the early Anglian Glacial as discussed by the authors, which is the basis of a revised Middle Pleistocene stratigraphy which comprises a rubified sol lessive formed in warm temperate conditions, which was altered to an arctic structure soil by periglacial processes.
Abstract: A conspicuous horizon of rubification, clay and iron enrichment, involutions and ice-wedge casts is attributed to two stages of soil formation. It comprises a rubified sol lessive formed in warm temperate conditions, which was altered to an arctic structure soil by periglacial processes. These palaeosols indicate that the sand and gravel deposits beneath the Lowestoft Till comprise two units, and provide the basis of a revised Middle Pleistocene stratigraphy. The Kesgrave Sands and Gravels were formed during the Beestonian in a periglacial environment by a major river which drained towards the north-east. Subsequently the Valley Farm Rubified Sol Lessive was formed during the Cromerian Interglacial, and the Barham Arctic Structure Soil and the associated Barham Loess were formed during the early Anglian Glacial. Both soils and the wind-blown sediments were formed on low relief terrace topography and are the remnants of a formerly extensive land surface. This feature was subsequently trimmed by meltwater rivers, then overlain by the Barham (outwash) Sands and Gravels and the Lowestoft Till which were deposited during the Anglian Glaciation.
108 citations
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TL;DR: There was a resurgence of infected lymphoblasts in 5 to 6 weeks after an apparent disappearance of parasitized cells from the cultures and no evidence was obtained by the methods employed which might indicate the existence of an extracellular form of the parasite capable of reinfecting new cells in vitro.
Abstract: Three spleen cell lines derived from 3 calves experimentally infected withTheileria parva have been established. After an apparent disappearance of parasitized cells from the cultures there was a resurgence of infected lymphoblasts in 5 to 6 weeks. The infected lymphoblasts can be readily subcultured without feeder layers in a medium consisting of Eagle’s Minimal Essential Medium and 20 per cent foetal calf serum. The plating of infected cells was greatly enhanced by implanting the cells on preformed monolayers. No evidence was obtained by the methods employed which might indicate the existence of an extracellular form of the parasite capable of reinfecting new cellsin vitro.
113 citations
Journal Article•
14 citations
TL;DR: Sedimentation after clumping at the interphase of aqueous solutions of polymers, dextran and methylcellulose, in combination with metrizoic acid was tried without success because the vast majority of the leukocytes sedimented together with the erythrocytes.
Abstract: The leukocyte migration test for in vitro studies of delayed type hypersensitivity has recently been reviewed (Soborg & Ben-dixen 1967; Bendixen & Soborg 1969). Soborg & Bendixen applied the test to circulating leukocytes in man and thereby widely increased the potentialities of this test. They obtained high leukocyte yields with only moderate erythrocyte admixture by harvesting the supernatant plasma after sedimentation of the erythrocytes for 60 min. at 37°C in the normal gravitational field (1 × g)- Their procedure was unsuitable for the present investigation because bovine erythrocytes sediment so slowly. Sedimentation after clumping at the interphase of aqueous solutions of polymers, dextran and methylcellulose, in combination with metrizoic acid (Boyum 1968) was tried without success because the vast majority of the leukocytes sedimented together with the erythrocytes. Separation of leukocytes from erythrocytes could not be achieved by differential centrifugation.
13 citations