Increased generation of superoxide in erythrocytes infected with Babesia gibsoni

Evaluation of Oxidative Status, Cytokines, Acute Phase Proteins and Cardiac Damage Markers in Sheep Naturally Infected with Babesia ovis

PURPOSE

Babesiosis is a tick-borne disease caused by protozoon species in the Babesia genus of the Babesiadae family. The systemic inflammatory response induced by infection is considered to be an important feature of the pathophysiology of ovine babesiosis. In this study, it was aimed to determine serum oxidative status, levels of some cytokines, acute phase proteins and heart damage markers in babesiosis infection.

MATERIALS AND METHODS

A sample of 40 sheep was used for this purpose, of which 20 were healthy and 20 were infected with Babesia ovis. Babesia infection was diagnosed from Giemsa-stained peripheral blood smears. Infection was also confirmed by the polymerase chain reaction (PCR). Sera from blood samples was tested for oxidative stress parameters (malondialdehyde [MDA], total antioxidant status [TAS], superoxide dismutase [SOD], catalase [CAT] and glutathione peroxidase [GPx]), cytokines (interleukins IL-6, IL-1β, IL-10, tumour necrosis factor α (TNF-α) and interferon-ϒ [IFN-ϒ]), acute-phase proteins (C-reactive protein [CRP], serum amyloid A [SAA] and haptoglobin [Hp]) and specific (troponin I [cTnI], creatine kinase-MB [CK-MB]) and nonspecific (lactate dehydrogenase [LDH], aspartate transaminase [AST]) cardiac damage markers.

RESULTS

MDA, SOD, CAT, Hp, TAS, IL-6, IL-10, TNF-α, IL-1β, INF-γ, AST, LDH, CK-MB mass and troponin I values were higher in the patient group than in the healthy group (P < 0.05). However, there was not found to be a statistical difference between the healthy and patient groups in terms of GPx, SAA and CRP values (P > 0.05).

CONCLUSIONS

It can be stated that serum levels of oxidative stress, some acute phase proteins and cardiac damage markers may increase in naturally infected sheep with babesiosis.

Pathogenesis of Anemia in Canine Babesiosis: Possible Contribution of Pro-Inflammatory Cytokines and Chemokines-A Review

Canine babesiosis is a tick-borne protozoan disease caused by intraerythrocytic parasites of the genus Babesia. The infection may lead to anemia in infected dogs. However, anemia is not directly caused by the pathogen. The parasite's developmental stages only have a marginal role in contributing to a decreased red blood cell (RBC) count. The main cause of anemia in affected dogs is the immune response to the infection. This response includes antibody production, erythrophagocytosis, oxidative damage of RBCs, complement activation, and antibody-dependent cellular cytotoxicity. Moreover, both infected and uninfected erythrocytes are retained in the spleen and sequestered in micro-vessels. All these actions are driven by pro-inflammatory cytokines and chemokines, especially IFN-γ, TNF-α, IL-6, and IL-8. Additionally, imbalance between the actions of pro- and anti-inflammatory cytokines plays a role in patho-mechanisms leading to anemia in canine babesiosis. This article is a review of the studies on the pathogenesis of anemia in canine babesiosis and related diseases, such as bovine or murine babesiosis and human or murine malaria, and the role of pro-inflammatory cytokines and chemokines in the mechanisms leading to anemia in infected dogs.

Relationship between Changes in Hematological Parameters, Levels of Acute Phase Proteins and Redox Homeostasis during Acute Babesia canis Infection in Dogs

Hemolysis and systemic acute inflammation characterize canine babesiosis caused by the intraerythrocytic protozoan parasite Babesia canis. Our hypothesis was that blood redox homeostasis of patients that suffered acute B. canis infection might be disturbed even after treatment with imidocarb-dipropionate and successful clinical recovery. Eight owner dogs with acute B. canis infection were used for this study. We analyzed the complete blood count, acute phase proteins (ceruloplasmin, haptoglobin, paraoxonase-1) in the serum, antioxidant enzymes (catalase and glutathione peroxidase) in the erythrocytes, and oxidative stress markers (malondialdehyde in erythrocytes and thiol groups in serum) at presentation and 15 days after treatment. Results were evaluated by corresponding statistical tests. At presentation, anemia, low/normal leukocyte count and severe thrombocytopenia occurred together with increased ceruloplasmin, haptoglobin levels within the reference interval, decreased paraoxonase-1 and compromised antioxidant defense in the red blood cells. After treatment and successful clinical recovery, hematological values generally fitted within the reference intervals, acute phase proteins were within the physiological levels in the majority of cases and the activities of the antioxidant enzymes were increased. However, elevated malondialdehyde levels indicated increased oxidative damage of erythrocytes that remained as a deleterious sequel despite a successful clinical recovery of the dogs.

Antioxidant Status, and Blood Zinc and Copper Concentrations in Dogs with Uncomplicated Babesiosis due to Babesia Canis Infections

INTRODUCTION

The aim of the study was to demonstrate a link between uncomplicated Babesia canis infection in dogs and blood concentrations of zinc and copper and erythrocytic antioxidant defence - activities of glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT).

MATERIAL AND METHODS

The study was based on 15 naturally occurring cases of canine babesiosis with anorexia, pyrexia, depression, pale mucous membrane, splenomegaly and dark red urine. Microscopic examination of Giemsa-stained peripheral blood smears and the results of PCR confirmed B. canis infection. Seven apparently healthy dogs brought in for either a check-up or vaccination were used for comparison.

RESULTS

The levels of the erythrocytic antioxidant enzymes - SOD and CAT - were significantly higher in the infected dogs than in cytologically negative dogs. The levels of blood micronutrients were significantly lower in the infected dogs (0.478 μg of zinc per mL vs 1.241 μg/mL and 0.722 μg of copper per mL vs 1.392 μg/mL).

CONCLUSION

Oxidative stress can be posited as one of the mechanisms leading to anaemia in dogs with babesiosis, and therefore antioxidant biomarker and copper and zinc concentrations could be used as indicators of disease severity and prognostic markers.

Prognostic markers and their discriminant score in predicting the outcome of Babesia gibsoni infection

BACKGROUND

We aimed to identify prognostic markers and their discriminant score in predicting the lethal outcome of canine Babesia gibsoni.

METHODS

Blood samples were collected from 108 client-owned dogs with clinical signs commensurate with babesiosis to analyze haematological, biochemical, haemostatic, antioxidant profile and thiobarbituric acid reactive substance levels. Samples were screened for Babesia infection (microscopic and molecular techniques). Babesiosis-affected dogs were classified into survivors and non-survivors, and 30 healthy dogs were used in the control group.

RESULTS

Haemoglobin, thrombocytes, catalase, urea, creatinine, alanine aminotransferase (ALT), alkaline phosphatase, lactate and reticulocytes were highly correlated to survival. Receiver operating characteristics analysis revealed urea, ALT and lactate as specific prognostic markers for the disease. The formula for calculation of discriminant scores (Di) for lethal outcome of the disease was generated with cut-off score 0.141. The scoring system was 79% sensitive and 83% specific in predicting the lethal outcome of the disease.

CONCLUSIONS

A scoring system developed from the prognosticating markers may aid in predicting the outcome of Babesia gibsoni infection on the day of presentation itself enabling intensive care for those animals with a cut-off score more than 0.141.

Evaluation of inflammatory biomarkers in goats naturally infected with Babesia ovis

This study was designed to evaluate the effects of Babesia ovis infection on concentrations of some essential acute phase proteins (APPs) including albumin, fibrinogen, serum amyloid A, haptoglobin, and ceruloplasmin as well as total, protein-binding, and lipid-binding sialic acids (TSA, PBSA, and LBSA) and two crucial cytokines including interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α). Some hematological parameters also were evaluated. Furthermore, any probable correlation among the APPs, SAs, IFN-γ, and TNF-α was calculated. A total of 420 Marghoz and Raeini goats with the ages of 1-3 years old from the north and northwest of Iran were examined, and 17 goats confirmed to be infected with B. ovis by both routine microscopic examination of blood films and molecular assays. As the control, 17 healthy goats were included. The results revealed a significant decrease (P < 0.05) in erythrocyte count, hemoglobin level, and pack cell volume as well as a nonsignificant increase in white blood cell count in the diseased animals compared with the control. Additionally, all the APPs, SAs, and cytokines were remarkably higher in the infected animals than the uninfected ones, except for albumin, which was significantly lower. Moreover, a strong and positive correlation was detected among the parameters mentioned above, except for albumin, which was inversely correlated with the other parameters. In conclusion, B. ovis infection is associated with the induction of severe inflammatory reactions in goats, and both SA and APP are significantly involved in the pathophysiology of the disease.

Relation of antioxidant status at admission and disease severity and outcome in dogs naturally infected with Babesia canis canis

BACKGROUND

Canine babesiosis is caused by species of the Babesia genus and has become an emerging disease worldwide. To the authors' knowledge there are no reports in which antioxidants have been analyzed in different presentations of canine babesiosis or in which the prognostic value of antioxidants has been studied. The aim of this study was to evaluate whether oxidative stress could be related to the severity and outcome of canine babesiosis. For this purpose a profile consisting of four antioxidant biomarkers (superoxide dismutase - SOD, glutathione peroxidase - GPx, catalase, total antioxidant status - TAS) and malondialdehyde - MDA as an oxidant biomarker (previously evaluated, here studied for comparative purposes) were evaluated in dogs with canine babesiosis of different clinical severity and outcomes.

RESULTS

The study was conducted with a sample of 40 dogs suffering from babesiosis (further divided into uncomplicated, one complication and multiple organ dysfunction syndrome - MODS group) and 30 healthy dogs (control group). Additionally, the babesiosis group was divided according to the anaemia into non-anaemic, mildly anaemic, moderately anaemic and severely anaemic dogs. The results of our study showed significantly decreased SOD, catalase and TAS values in diseased dogs compared to controls, while there were no significant differences in GPx between these groups. Dogs that developed MODS showed lower activities of SOD and GPx and higher MDA values compared to dogs with uncomplicated babesiosis as well as with dogs that developed one complication. Superoxide dismutase, catalase and GPx were negatively correlated whereas MDA was positively correlated with the lethal outcome of the disease. Furthermore, this study detected more pronounced decrease in antioxidant biomarkers (SOD, GPx and catalase) in dogs with moderate anaemia compared to those with mild anaemia.

CONCLUSIONS

The results of this study showed changes in biomarkers related to the antioxidant status of dogs naturally infected with B. canis canis. These biomarkers could be used as indicators of disease severity and outcome in dogs suffering from babesiosis.

Hematologic manifestations of babesiosis

BACKGROUND

Babesiosis, a zoonotic parasitic infection transmitted by the Ixodes tick, has become an emerging health problem in humans that is attracting attention worldwide. Most cases of human babesiosis are reported in the United States and Europe. The disease is caused by the protozoa of the genus Babesia, which invade human erythrocytes and lyse them causing a febrile hemolytic anemia. The infection is usually asymptomatic or self-limited in the immunocompetent host, or follows a persistent, relapsing, and/or life threatening course with multi-organ failure, mainly in the splenectomized or immunosuppressed patients. Hematologic manifestations of the disease are common. They can range from mild anemia, to severe pancytopenia, splenic rupture, disseminated intravascular coagulopathy (DIC), or even hemophagocytic lymphohistiocytosis (HLH).

CASE PRESENTATION

A 70 year old immunocompetent female patient living in New York City presented with a persistent fever, night sweats, and fatigue of 5 days duration. Full evaluation showed a febrile hemolytic anemia along with neutropenia and thrombocytopenia. Blood smear revealed intraerythrocytic Babesia, which was confirmed by PCR. Bone marrow biopsy was remarkable for dyserythropoiesis, suggesting possible HLH, supported by other blood workup meeting HLH-2004 trial criteria.

CONCLUSION

Human babesiosis is an increasing healthcare problem in the United States that is being diagnosed more often nowadays. We presented a case of HLH triggered by Babesia microti that was treated successfully. Also, we presented the hematologic manifestations of this disease along with their pathophysiologies.

Parasitic liver disease in travelers

Liver disease is an important source of morbidity among ill returning travelers. Jaundice is one of the most common and obvious symptoms of liver disease, the differential diagnosis of which is extensive, especially in travelers. Jaundice in travelers can arise from both infectious and noninfectious causes. We herein summarize the most common parasitic etiologies that may lead to jaundice in the returned traveler, visitors of friends and relatives, or new immigrants, and describe the etiology, epidemiology, and pathogenesis of clinical features of each.

Serum of Babesia rodhaini infected mice down regulates catalase activity of healthy erythrocytes

Hemolytic activity for animals infected with various Babesia species is well reported. In this study, we confirmed that serum of Babesia rodhaini-infected mice also showed hemolytic activity. Erythrocytes from non-infected mice were lysed by co-incubation with B. rodhaini-infected serum. Catalase activity of the non-infected target erythrocytes was suppressed after this co-incubation with the hemolytic serum of B. rodhaini-infected mice. Furthermore, serum hemolytic activity was inhibited when target erythrocytes were incubated with hemolytic serum in the presence of exogenous catalase. Our study indicated that hemolytic serum can down-regulate the antioxidant capacity of non-infected healthy erythrocytes, possibly as a result of catalase activity, thereby leading to hemolysis.

Babesiosis in dogs and cats--expanding parasitological and clinical spectra

Canine babesiosis caused by different Babesia species is a protozoal tick-borne disease with worldwide distribution and global significance. Historically, Babesia infection in dogs was identified based on the morphologic appearance of the parasite in the erythrocyte. All large forms of Babesia were designated Babesia canis, whereas all small forms of Babesia were considered to be Babesia gibsoni. However, the development of molecular methods has demonstrated that other Babesia species such as Babesia conradae, Babesia microti like piroplasm, Theileria spp. and a yet unnamed large form Babesia spp. infect dogs and cause distinct diseases. Babesia rossi, B. canis and Babesia vogeli previously considered as subspecies are identical morphologically but differ in the severity of clinical manifestations which they induce, their tick vectors, genetic characteristics, and geographic distributions, and are therefore currently considered separate species. The geographic distribution of the causative agent and thus the occurrence of babesiosis are largely dependent on the habitat of relevant tick vector species, with the exception of B. gibsoni where evidence for dog to dog transmission indicates that infection can be transmitted among fighting dog breeds independently of the limitations of vector tick infestation. Knowledge of the prevalence and clinicopathological aspects of Babesia species infecting dogs around the world is of epidemiologic and medical interest. Babesiosis in domestic cats is less common and has mostly been reported from South Africa where infection is mainly due to Babesia felis, a small Babesia that causes anemia and icterus. In addition, Babesia cati was reported from India and sporadic cases of B. canis infection in domestic cats have been reported in Europe, B. canis presentii in Israel and B. vogeli in Thailand. Babesiosis caused by large Babesia spp. is commonly treated with imidocarb dipropionate with good clinical response while small Babesia spp. are more resistant to anti-babesial therapy. Clinical and parasitological cure are often not achieved in the treatment of small Babesia species infections and clinical relapses are frequent. The spectrum of Babesia pathogens that infect dogs and cats is gradually being elucidated with the aid of molecular techniques and meticulous clinical investigation. Accurate detection and species recognition are important for the selection of the correct therapy and prediction of the course of disease.

Clinical management of canine babesiosis

OBJECTIVE

To review and summarize current information regarding epidemiology, pathogenesis, and pathophysiology leading to the various clinical syndromes associated with canine babesiosis. Diagnosis, treatment, preventative strategies, and zoonotic implications are discussed.

ETIOLOGY

Babesiosis is caused by hemoprotozoa of the genus Babesia. Numerous species of Babesia exist worldwide. An increased incidence of babesiosis is described, especially in North America. The babesial organism spends the majority of its life cycle within the erythrocyte of the definitive host, resulting in hemolysis, with or without systemic complications.

DIAGNOSIS

Definitive diagnosis depends on direct visualization of the organism on blood smear or polymerase chain reaction. A positive serologic antibody test indicates exposure with or without active infection.

THERAPY

Antiprotozoal drugs, antimicrobials, and supportive care are the mainstays of babesiosis therapy.

PROGNOSIS

Prognosis depends on the severity of disease, which in turn depends on both organism and host factors. Clinical syndromes associated with a poorer prognosis include red biliary syndrome, acute renal failure, acute respiratory distress syndrome, neurologic dysfunction, acute pancreatitis, cardiac dysfunction, and hypoglycemia.

Detection of erythrocyte binding IgM and IgG by flow cytometry in sick dogs with Babesia canis canis or Babesia canis vogeli infection

The aim of this study was to examine by means of flow cytometry immunophenotyping (FCI) if sick dogs infected with Babesia canis canis (B. c. canis) or Babesia canis vogeli (B. c. vogeli) had anti-erythrocyte membrane binding IgG and/or IgM at the time of diagnosis. Diagnosis of Babesia infection was assessed by blood smear and by PCR-restriction fragment length polymorphism analysis in 30 sick dogs. Signalment, clinical history, physical examination and laboratory tests of B. c. canis (n=24) and of B. c. vogeli (n=6) infected dogs were studied. The majority of B. c. canis infected dogs showed anemia (92%) predominantly non-regenerative (94%), while the B. c. vogeli infected dogs had a regenerative anemia (67%). Eccentrocytosis was present in 33% of the B. c. canis infections. Four of six B. c. vogeli infected dogs had erythrocytes membrane antibodies. One dog resulted uncertain and one resulted negative to FCI. In contrast, all the B. c. canis infected dogs were negative for erythrocytes membrane binding immunoglobulins detection. In addition, the mean percentages of erythrocytes binding IgG and IgM were statistically much lower in B. c. canis than in B. c. vogeli infected dogs. At the time of the diagnosis, the formation of erythrocyte membrane binding IgG and IgM by immune mechanisms appears not to be involved in B. c. canis infections while it is present in the majority of B. c. vogeli infections.

Erythrocytic antioxidant defense, lipid peroxides level and blood iron, zinc and copper concentrations in dogs naturally infected with Babesia gibsoni

Babesiosis is a common tick borne disease of dogs in tropical and subtropical regions of the world caused by different species of Babesia. The present study aimed to examine erythrocyte lipid peroxide and erythrocytic antioxidant levels in dogs with clinical babesiosis, caused by Babesia gibsoni, and impact of the disease on blood iron, zinc and copper levels. The study was conducted on 10 naturally occurring cases of canine babesiosis with the history of tick infestation, erratic pyrexia, and prolonged illness. Microscopic examination of Giemsa stained peripheral blood smears confirmed B. gibsoni infection in the erythrocytes. Six apparently healthy dogs of different age, sex and breeds, brought for either health checkup or vaccination were used for comparison. Levels of erythrocytic antioxidant enzymes were significantly (P<0.01) higher in sick dogs than those of cytologically negative dogs (catalase: 0.192+/-0.024 units/mg Hb vs 0.074+/-0.004 units/mg Hb; superoxide dismutase: 0.014+/-0.0009 units/mg Hb vs 0.006+/-0.0008 units/mg Hb and lipid peroxide: 6.01+/-0.30 nmol MDA/mg Hb vs 1.89+/-0.10 nmol MDA/mg Hb). The levels of blood micronutrients were significantly low in these dogs (iron: 89.87+/-8.12 microg/g vs 126.44+/-14.65 microg/g; zinc: 3.67+/-1.85 microg/g vs 5.62+/-1.83 microg/g and copper: 0.55+/-0.63 microg/g vs 0.65+/-0.04 microg/g). The study demonstrated oxidative damage in dogs naturally infected with B. gibsoni. Low level of blood iron, zinc and copper seems to have an additional role in the genesis of anaemia and oxidative stress.

Suppressive effect of culture supernatant of erythrocytes and serum from dogs infected with Babesia gibsoni on the morphological maturation of canine reticulocytes in vitro

The present study evaluated the effects of infected culture supernatant of erythrocytes, fractionation of culture supernatant and serum from dogs infected with Babesia gibsoni (B. gibsoni) on the maturation of canine reticulocytes in vitro. The SDS-PAGE demonstrated that significantly broader bands were generated by both the infected culture supernatant of erythrocytes and the serum from dogs chronically infected with B. gibsoni. The culture supernatant of erythrocytes infected with B. gibsoni strongly suppressed the maturation of reticulocytes. Prior studies showed that chronically infected serum had inhibitory effects on both the maturation of reticulocytes and the canine pyrimidine 5'-nucleotidase subclass I and purine-specific 5'-nucleotidase activity. In addition, serum free infected culture supernatant of erythrocytes had an inhibitory effect on the morphological maturation of reticulocytes. These results suggest that infected serum and culture supernatant of erythrocytes might accumulate excess proteins and/or metabolites as a result of the inhibited maturation of reticulocytes and decreased activity of erythrocyte 5'-nucleotidase. Furthermore, the fractions observed at >150 kDa- and 150-70 kDa- in the infected culture supernatant and serum retarded the maturation of canine reticulocytes in vitro. The results obtained from the in vitro examinations, in the present study, suggested that B. gibsoni itself and/or its metabolites might release certain proteins in the infected culture supernatant and serum from infected dogs and as a result delay morphological maturation of canine reticulocytes.

Inhibitory effect of pyrimidine and purine nucleotides on the multiplication of Babesia gibsoni: possible cause of low parasitemia and simultaneous reticulocytosis in canine babesiosis

The present study was conducted to determine the cause of low parasitemia and simultaneous reticulocytosis in canine babesiosis. The parasitemia was significantly decreased in in vitro cultures of Babesia gibsoni by the pretreatment of host canine erythrocytes with lead acetate, which is a specific inhibitor of pyrimidine 5'-nucleotidase subclass I (P5N-I). The serum from dogs chronically infected with B. gibsoni did not decrease the activities of hexokinase, glucose-6-phosphate dehydrogenase or 6-phosphogluconate dehydrogenase in canine reticulocytes, although it was previously reported that this serum had inhibitory effects on both the maturation of reticulocytes and the canine P5N-I and purine-specific 5'-nucleotidase activities. Furthermore, the in vitro multiplication of B. gibsoni was significantly inhibited by pyrimidine nucleotides such as cytidine 5'-monophosphate (5'-CMP), which is preferentially catalyzed by P5N-I and also inhibits the morphological maturation of canine reticulocytes. Purine nucleotides such as inosine 5'-monophosphate (5'-IMP) also had an inhibitory effect on the multiplication of this parasite. These results suggest that nucleotides such as 5'-CMP and 5'-IMP might accumulate in young erythrocytes and/or serum in dogs infected with B. gibsoni as a result of the decreased activity of erythrocyte 5'-nucleotidase, and the accumulation of these nucleotides might inhibit the multiplication of this parasite and simultaneously retard the maturation of reticulocytes. The results obtained from the in vitro examinations in the present study may partially clarify the relationship between low parasitemia and simultaneous reticulocytosis in vivo in canine babesiosis.

Serum from dogs Infected with Babesia gibsoni inhibits maturation of reticulocytes and erythrocyte 5'-nucleotidase activity in vitro

Erythrocyte 5'-nucleotidase is thought to be involved in the maturation of erythrocytes. In the present study, in vitro incubation of canine erythrocytes demonstrated that significant inhibition of 5'-nucleotidase activity occurred in the presence of serum from dogs infected with Babesia gibsoni, when the enzyme was assayed with cytidine 5'-monophosphate (5'-CMP) and inosine 5'-monophosphate (5'-IMP) as substrates. The multiplication of B. gibsoni in in vitro culture also resulted in a significant decrease in the enzyme activity of erythrocytes in the culture. Furthermore, the infected serum and 5'-CMP retarded the maturation of canine reticulocytes in vitro. These results suggested that nucleotides such as 5'-CMP and 5'-IMP might accumulate in young erythrocytes and/or serum in dogs infected with B. gibsoni as a result of decreased activity of erythrocyte 5'-nucleotidase, resulting in the delayed maturation of reticulocytes.

Babesia gibsoni: preferential multiplication in reticulocytes is related to the presence of mitochondria and a high concentration of adenosine 5'-triphosphate in the cells

To determine the cause of the predilection of Babesia gibsoni for reticulocytes, the parasites were cultivated with various types of reconstituted erythrocyte ghosts, which were prepared by resealing erythrocyte ghosts together with variously treated erythrocyte lysate, in vitro. The level of parasitemia in the culture with reconstituted reticulocyte ghosts containing untreated reticulocyte lysate was significantly higher than that in the culture with reconstituted normocyte (mature erythrocyte) ghosts containing untreated normocyte lysate. The removal of mitochondria from reconstituted reticulocyte ghosts by filtration or centrifugation resulted in decreased of parasitemia in those cultures. In contrast, when mitochondria from reticulocytes were loaded into reconstituted normocyte ghosts, the parasitemia in the ghosts loaded mitochondria was increased to the same level as that in reconstituted reticulocyte ghosts. Furthermore, the parsitemia in the culture with reconstituted normocyte ghosts was proportional to the concentration of adenosine 5'-triphosphate in the ghosts. These results suggested that mitochondria of reticulocytes might enhance the multiplication of B. gibsoni through the generation of adenosine 5'-triphosphate within the cells.

The effect of macrophages on the erythrocyte oxidative damage and the pathogenesis of anemia in Babesia gibsoni-infected dogs with low parasitemia

The role of macrophages in the erythrocyte membrane oxidative damage and the pathogenesis of anemia in Babesia gibsoni-infected dogs with low parasitemia were investigated. Macrophages derived from peripheral blood monocytes (PBM) from B. gibsoni-infected dogs produced significantly higher chemiluminescent responses, indicating the release of reactive oxygen intermediates, than those from non-infected dogs when the cells were subjected to non-specific stimulation with phorbol 12-myristate 13-acetate (PMA) and opsonized zymosan (OZ), or infected dog erythrocyte membranes opsonized with infected dog serum. These results indicate that PBM of B. gibsoni-infected dogs with low parasitemia were highly activated compared to those of non-infected dogs. Furthermore, the membrane lipid peroxidation of normal dog erythrocytes incubated with PBM from B. gibsoni-infected dogs was significantly higher (p<0.05) than that of erythrocytes incubated with PBM from non-infected dogs when the PBM were stimulated with the opsonized membranes. These results suggest that the oxidative damage of erythrocytes observed in B. gibsoni-infected dogs with low parasitemia might be induced, in part, by reactive oxygen species released from the activated PBM. On the other hand, the present study also showed a significant increase (p<0.001) of IgG-bound erythrocytes in B. gibsoni-infected dogs compared with such erythrocytes in non-infected dogs. The increase of IgG-bound erythrocytes in infected dogs might reflect the increase of erythrocytes with oxidative damage induced by the infection with B. gibsoni. The results of the present study suggest that the increase of IgG-bound erythrocytes in the circulation of infected dogs induce a high degree of erythrocyte loss via immunological phagocytosis by activated macrophages, resulting in severe anemia in spite of low parasitemia.