A cold precipitable fibrinogen complex in the plasma of cattle dying from infection with Babesia argentina

A study of autoantibodies to phosphatidyl-serine in Babesia bovis and Babesia bigemina infections in cattle

Sera from cattle infected with Babesia bovis were found to contain antibodies to phosphatidyl-serine (PS), a negatively charged phospholipid normally found on the internal membrane of erythrocytes. In contrast, no autoantibodies were detected following Babesia bigemina infection indicating that the autoimmunity is not genus specific. During infection with Babesia bovis, PS translocates to the external membrane and it is suggested that this may result in PS behaving as an autoantigen owing to a transitional change. These autoantibodies may also play some role in the pathology of infection, especially the disturbed coagulation system associated with acute Babesia bovis infection.

In vitro adherence of bovine erythrocytes infected with Babesia bovis to thrombospondin and laminin

This study was undertaken to examine how eight putative adhesive agents bound to plastic surfaces affected the capacity of bovine erythrocytes, infected with either virulent or avirulent strains of Babesia bovis, to adhere in vitro. Thrombospondin (TSP) induced B. bovis-infected bovine erythrocytes to adhere and adherence was augmented when the infected blood was cultured for 24 h before the assay. Moreover, TSP also caused erythrocytes infected with avirulent strains of B. bovis to adhere to plastic in vitro. Laminin promoted the adherence of infected, and to a lesser extent, of uninfected erythrocytes.

The use of pathophysiological reactions to assess the efficacy of the immune response to Babesia bovis in cattle

A group of five splenectomised calves was immunised with a soluble extract prepared from erythrocytes infected with Babesia bovis and then challenged by the intravenous inoculation of virulent B. bovis along with appropriate control animals. All controls died but four of the five immunised animals survived. All survivors showed significantly lower activation of the coagulation and kinin systems and did not develop the hypotensive shock syndrome characteristic of acute B. bovis infection. It was concluded that the concentrations of fibrinogen, kininogen, and bradykinin, and the production of soluble fibrin, cryofibrinogen, and high molecular weight fibrinogen complexes were useful criteria on which to assess the efficacy of the immune response.

The irradiation of Babesia bovis. 1. The difference in pathogenicity between irradiated and non-irradiated populations

Babesia bovis parasites attenuated by 35 krads gamma irradiation and parasites not exposed to irradiation, were injected into intact 2-year-old Hereford steers. All five animals receiving non-irradiated blood died but the five animals which received irradiated blood were only mildly affected. Highly significant differences were observed in changes to plasma fibrinogen, serum fibrinogen-like proteins, packed cell volume, partial thromboplastin time, prothrombin time, blood kinins, and plasma kininogen levels in the control animals but non-significant changes in these parameters occurred in the group receiving iradiated blood. Significant changes in the antiplasmin alpha 2M, and the antithrombin levels occurred in control cattle but not in the group receiving irradiated blood. Parasite multiplications rates and maximum parasitaemias were similar in both groups. Irradiation reduced the dose of living parasites from 1 x 10(8) to 2.5 x 10(3), but this was not the reason for the mild reactions. It was concluded that irradiation had selected an avirulent parasite population.

The plasma cryofibrinogen of calves infected with Oesophagostomum radiatum

A cryofibrinogen complex was detected in the plasma of cattle infected with Oesophagostomum radiatum. Its formation coincided with the development of hypofibrinogenaemia and it consisted basically of fibrinogen and soluble noncross-linked fibrin in both monomer and high molecular forms. Also present in the complex, albeit in trace amounts, were cold insoluble globulin, TgG, and plasminogen. It is suggested that the complex results from thrombin activation in vivo and its role is to maintain fibrin in solution thus preventing its deposition in the vascular system.

Babesia bovis (argentina): analysis of fibrinogen-like proteins during infection

Fibrinogen and fibrinogen-like proteins (FLP) were isolated from plasma and serum of cattle acutely infected with Babesia bovis. The sizes and chain structures of these proteins were examined and clotting assays performed. The results indicated that the blood was in a hypercoagulable state due mainly to enhanced production of hydrogen bonded fibrin and offset partly by slight inhibition of chain cross-linking. The latter appeared due to a Factor XIII inhibitor. Reduction of A alpha chains of plasma FLP was not evident, nor could lower molecular weight remnants be regularly detected strongly suggesting that fibrin(ogen) lysis rarely occurred. Similarly the size and chain structure of the majority of noncoagulable FLP of serum was consistent with their being the product of coagulation and not fibrinolysis. Only in heavily infected splenectomized cattle were products from lysed cross-linked fibrin detected and these constituted only about 3% of total serum FLP.

Babesia bovis (argentina): components of the cryofibrinogen complex and their contribution to pathophysiology of infection in splenectomized calves

A cryofibrinogen complex, found in the plasma of cattle acutely infected with Babesia bovis (argentina), was characterized. The fibrinogen-like proteins of the complex were isolated and the structure of their polypeptide chains analysed. In general, the chain structure was similar to that of soluble non-crosslinked fibrin (fibrinogen) although chains indicating some degree of fibrin crosslinking were often detected. Only rarely did the chain structure suggest that fibrinolysis occurred. It was concluded that the complex was produced by activation of the coagulation system but that fibrinolysis did not occur to any marked degree. The complex was implicated in assistance to the sludging of erythrocytes in the internal organs which is a feature of the pathogenesis of the disease.

Babesia bovis (= argentina): changes in erythrophylic and associated proteins during acute infection of splenectomized and intact calves

Saline eluates were prepared from sucrose-washed erythrocytes of cattle infected with B. bovis (= argentina). Fibrinogen, plasminogen and IgG2 were constituent proteins of the eluates and all three proteins increased in concentration during infection. The significance of the protein changes and their contribution to coagulation and fibrinolysis during infection are discussed.

Babesia bovis (argentina): observations of coagulation parameters, fibrinogen catabolism and fibrinolysis in intact and splenectomized cattle

The results of this paper indicate that cattle infected with B. bovis (argentina) have a markedly altered and activated coagulation system. A degree of thrombin activation occurs due partly to release of thromboplastin-like substances from lysed erythrocytes but due primarily to activation of kallikrein by babesial proteases. This produces a hyperfibrinogenaemia, particularly in intact cattle, with soluble fibrin complexes constituting up to one-third of the total fibrinogen concentration. High molecular weight non-coagulable fibrinogen-like proteins are detected terminally but more so in splenectomized cattle. Plasminogen concentration decreases in splenectomized but not intact cattle while low molecular weight fibrinogen degradation products are not easily detected. It is suggested that a hypercoagulable intermediate state with little or no fibrin deposition occurs rather than terminal disseminated intravascular coagulation.

Acute Babesia bigemina infection: changes in coagulation and kallikrein parameters

Plasma from splenectomized calves infected with B. bigemina were assayed for disturbances in the coagulation system. Changes were observed in the WBCT, PTT, PT, TT and RT as well as in fibrinogen, calcium and thrombocyte levels. These changes were most marked during days 6--7 when parasite numbers were greatest. Massive intramuscular haemolysis coincided with these changes. The plasma kallikrein level fell progressively from days 6--11 and the level of activated kallikrein rose slightly. Parasite doubling time was calculated at 8.13 h. The similarities and differences between this disease and B. argentina infections of cattle are discussed.

Acute Babesia bigemina infection: changes in fibrinogen catabolism

Plasma from cattle infected with Babesia bigemina contained soluble fibrin in monomer and high molecular weight complex forms. Fibrin(ogen) degradation products were not constantly detected and there appeared to be little or no evidence to suggest fibrinolysis or fibrin deposition. It is suggested that classical disseminated intravascular coagulation does not occur during B. bigemina infection.

Babesia argentina: observations on the immunogenicity of the cryofibrinogen complex

Rabbit antisera were prepared against the soluble and insoluble fractions of a cryofibrinogen complex that formed in plasma of cattle acutely infected with Babesia argentina. Analyses of the rabbit antisera indicated that the cryofibrinogen complex contained proteins from erythrocytes and parasites as well as fibrinogen and related proteins.