Is the coagulopathy of hepatosplenic schistosomiasis immune-related?

Impact of neutrophil apoptosis on haemostatic activation in chronic liver disease patients

Recent studies suggest the impact of apoptosis on the mechanisms leading to hypercoagulability. We aimed to clarify the potential role of neutrophil apoptosis in neutropenia and hypercoagulable state encountered in chronic liver disease patients. This study was conducted on 15 normal controls and 45 patients with chronic liver disease classified according to modified Child Pugh classification into, Child A, B and C groups (15 cases each). Haemostatic parameters studied include, prothrombin time, partial thromboplastin time, tissue factor, protein C antigen, protein S antigen, and markers of haemostatic activation [prothrombin fragment 1+2 (F1+2), thrombus precursor protein (TpP) and D-dimer]. Flowcytometric study was done for quantitative assay of neutrophil apoptotic subpopulations to detect the percentage of early and late apoptotic, and necrotic neutrophils using Annexin V-FITC/propidium iodide dye. Semiquantitative assay of apoptotic neutrophils showing DNA fragmentation was performed on neutrophil culture using terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labelling test. In addition to enzyme-linked immunosorbent assay for soluble Fas (APO-1/CD95) in culture supernatant. The results revealed a rise in the neutrophil apoptotic and necrotic markers with progression of the disease, and they were inversely correlated with the absolute neutrophil count. The apoptotic neutrophil cells showed a significant positive correlation with several haemostatic parameters (tissue factor, prothrombin fragment 1+2, thrombus precursor protein and D-dimer). Regression analysis proved that apoptotic parameters are independent determinants of prothrombotic markers, which further incriminate the apoptotic mechanisms in the hypercoagulable state encountered in this clinical setting.

Sm22.6 antigen is an inhibitor to human thrombin

The physiological role of Schistosomiasis mansoni 22.6 antigen (sm22.6 Ag) and its pathogenic effect on the human host has never been reported. Recombinant sm22.6 Ag is a homogenous polymer under non-denaturing/non-reducing conditions, and an inhibitor to human thrombin. Kinetic and Western blot assays show that the recombinant protein interacts with human thrombin and inhibits proteolytic activity of the protease. Tests of whole blood revealed that coagulation time was significantly delayed (3-5 times longer) in the presence of the recombinant protein at a concentration similar to thrombin in normal blood samples. Kinetic studies revealed that the delayed coagulation time was due to the inhibition of alpha-thrombin proteolytic activity by the parasite protein in an irreversible pattern, and a reversible inhibition to gamma-thrombin. Also, Western blot analysis under non-denaturing/non-reducing conditions showed that sm22.6 Ag binds to both alpha- and gamma-thrombin. Our results strongly suggest that sm22.6 antigen plays a role in down-regulation of coagulation in humans.

Haemostatic abnormalities in hepatosplenic schistosomiasis mansoni

Hepatosplenic schistosomiasis is a complex immuno-regulatory disease and is major health problem in endemic countries. Acute bleeding is one of its most serious complications and often life-threatening. Clinical studies have demonstrated that the patients with hepatosplenic schistosomiasis are prone to develop complex haemostatic abnormalities that may be linked to the potential risk of bleeding from ruptured esophageal varices in these patients. The deficit in haemostatic parameters is more pronounced with the advancement of the disease and is maximal in the patients with experience of haematomesis. Evidences of enhanced generation of thrombin and plasmin indicate the presence of low-grade DIC in advanced hepatosplenic schistosomiasis, which is considered as a principal cause of haemostatic abnormalities in this endemic disease. Demonstration of procoagulant expression in peripheral blood monocytes of the patients and in the livers, spleens and intestines of S. mansoni-infected mice suggest their possible implication in the causation of DIC in S. mansoni infections. Moreover, because in vitro analysis indicates a participation of immune mechanisms in the localized procoagulant expression, it seems likely that the immune responses to schistosomes play a major role in the pathogenic mechanisms of haemostatic abnormalities in hepatosplenic schistosomiasis.

Enhanced monocyte tissue factor expression in hepatosplenic schistosomiasis

Monocyte tissue factor expression was evaluated in 67 patients with hepatosplenic Schistosomiasis. They were classified as Child A (n = 15), Child B (n = 15), Child C (n = 12) and Bleeders (n = 10), in addition to 15 healthy controls. Mononuclear cells were cultured in vitro with and without lipopolysaccharide (LPS) to assess monocyte tissue factor (TF) antigen (Ag) and activity (Act) in cell lysate, in addition to measurement of prothrombin fragment 1 + 2 (F1 + 2) as a marker of in vivo thrombin generation. A significant increase in monocyte TF Ag and TF Act was noted in all stages of the disease compared with the control group, with marked accentuation during an acute attack of variceal bleeding. This enhanced monocyte expression was noted before the addition of LPS and became more obvious with addition of LPS. An increasing level of F1 + 2 was similarly noted. These findings constitute further evidence for an existing prothrombotic state in hepatosplenic Schistosomiasis, and also that monocytes are closely implicated in the haemostatic diathesis characterizing the disease.

Hepatitis B and C virus markers among patients with hepatosplenic mansonic schistosomiasis

PURPOSE

To evaluate the frequency and the consequences of the co-infection of hepatitis B and C viruses in patients with hepatosplenic schistosomiasis (HSS).

METHODS

B and C serologic markers, exposure to risk factors, biochemical assays, upper gastrointestinal endoscopies, and abdominal ultrasonograms were evaluated in 101 patients with HSS from 1994 to 1997. Whenever possible, PCR was tested and histopathological studies were reviewed.

RESULTS

At least one HBV virus marker was found in 15.8%, and anti-HCV was detected in 12.9% of the subjects. The seropositive subjects tended to be older than the seronegative ones. A history of blood transfusion was significantly related to the presence of anti-HCV. Three (18.75%) out of 16 subjects exposed to B virus were HBsAg positive. Eleven (84.6%) out of thirteen patients who were anti-HCV positive demonstrated viral activity. Patients with ongoing viral infection presented a higher average level of liver aminotransferases, a higher frequency of cell decompensation and a higher rate of chronic hepatitis. Portal hypertension parameters were not influenced by viral exposure.

CONCLUSIONS

The rate of hepatitis B and C viruses serologic markers observed in the patients with HSS was higher than the control group. The co-infection was responsible for a higher frequency of cell decompensation.

Hyperfibrinolysis in hepatosplenic schistosomiasis

AIM

To evaluate the nature of accelerated fibrinolysis in hepatosplenic schistosomiasis.

METHODS

The biological activity of plasminogen (Plg), plasminogen activators (PA), alpha 2-antiplasmin (alpha 2-AP) and plasminogen activator inhibitor-1 (PAI-1) was determined by photometric analysis in 15 compensated and 35 decompensated patients with endemic Egyptian hepatosplenomegaly. Quantitative measurement of plasma concentrations of tissue t-PA, t-PA-PAI-1 complex, alpha 2-antiplasmin-plasmin complex (alpha 2-APP), fibrinogen degradation products (FbDP), D-dimers (D-D), thrombin-antithrombin complex (TAT) and prothrombin fragment (F 1 + 2) complexes, using double antibody sandwich enzyme linked immunosorbent assays and grading of the degree of hepatic insufficiency according to the Child-Pugh classification, were also carried out.

RESULTS

The progressive deterioration of liver function in schistosomal patients, which matched the severity of the disease, led to simultaneous defects in profibrinolytic (decreased Plg and increased PA and t-PA) and antifibrinolytic (decreased alpha 2-AP and PAI-1) factors-the latter defects being the most prominent-resulting in significant generation of plasmin (increased APP complexes) and therefore enhanced fibrinolysis (increased FbDP and D-dimer). The raised concentrations of FbDP, D-D, TAT and F 1 + 2 established its secondary nature.

CONCLUSION

These findings suggest that the amount of PAI-1 available to bind and neutralise circulating t-PA may be a critical factor in the progress of hyperfibrinolysis observed in hepatosplenic schistosomiasis, and that the pronounced reduction in its plasma concentration may be regarded as a potential warning indicator of haemostatic imbalance in decompensated schistosomal patients at high risk of variceal bleeding.