Endotoxins and their significance for murine trypanosomiasis

The study of endotoxins is complicated by their heterogenous nature, their multiple effects and the complex methodologies required for their identification. In this brief review, Vic Pentreath summarizes how the substances have been implicated in the pathogenesis of several diseases caused by parasitic protozoa, and how the parasites (eg. Plasmodium falciparum and Trypanosoma cruzi) may themselves contain endotoxin-like materials. Recent studies have shown that, during T. b. brucei infection in mice, serum endotoxin levels become markedly elevated and that endotoxin-like substances are also present in the purified parasite extracts.     

Individual Variation in Levels of Haptoglobin-Related Protein in Children from Gabon

Background

Haptoglobin related protein (Hpr) is a key component of trypanosome lytic factors (TLF), a subset of high-density lipoproteins (HDL) that form the first line of human defence against African trypanosomes. Hpr, like haptoglobin (Hp) can bind to hemoglobin (Hb) and it is the Hpr-Hb complexes which bind to these parasites allowing uptake of TLF. This unique form of innate immunity is primate-specific. To date, there have been no population studies of plasma levels of Hpr, particularly in relation to hemolysis and a high prevalence of ahaptoglobinemia as found in malaria endemic areas.

Methods and Principal Findings

We developed a specific enzyme-linked immunosorbent assay to measure levels of plasma Hpr in Gabonese children sampled during a period of seasonal malaria transmission when acute phase responses (APR), malaria infection and associated hemolysis were prevalent. Median Hpr concentration was 0.28 mg/ml (range 0.03–1.1). This was 5-fold higher than that found in Caucasian children (0.049 mg/ml, range 0.002–0.26) with no evidence of an APR. A general linear model was used to investigate associations between Hpr levels, host polymorphisms, parasitological factors and the acute phase proteins, Hp, C-reactive protein (CRP) and albumin. Levels of Hpr were associated with Hp genotype, decreased with age and were higher in females. Hpr concentration was strongly correlated with that of Hp, but not CRP.

Conclusions/Significance

Individual variation in Hpr levels was related to Hp level, Hp genotype, demographics, malaria status and the APR. The strong correlations between plasma levels of Hp and Hpr suggest that they are regulated by similar mechanisms. These population-based observations indicate that a more dynamic view of the relative roles of Hpr and Hpr-Hb complexes needs to be considered in understanding innate immunity to African trypanosomes and possibly other pathogens including the newly discovered Plasmodium spp of humans and primates.     

Cytokines and the acute phase response in post-treatment reactive encephalopathy of Trypanosoma brucei brucei infected mice

Stimulation of the acute phase response during infection of mice with Trypanosoma brucei brucei (T. b. brucei) was investigated in an experimental model of the post-treatment reactive encephalopathy (PTRE), a common side-effect of anti-trypanosome therapy. Plasma levels of the acute phase proteins (APP), haptoglobin (Hp) and serum amyloid P (SAP) increased by day 7 post-infection, but by day 20 had fallen to an intermediate level. This was accompanied by induction of the cytokines, interleukin (IL)-6 and tumour necrosis factor-alpha (TNFalpha) in both liver and brain. Treatment of mice on day 21 with a subcurative dose of diminazene aceturate (Berenil), a procedure known to induce a mild PTRE, cleared the parasite from the circulation with plasma APP and liver expression of mRNA for IL-6 and TNFalpha returning to the levels in the controls. Cytokine mRNA for both IL-6 and TNFalpha was detected in the brains of animals with developing PTRE although TNFalpha was not significantly greater than in the control group. A further subcurative dose of Berenil, leading to a more severe PTRE, was associated with elevated serum concentrations of Hp and SAP, increased TNFalpha mRNA in the liver and detectable IL-6 and TNFalpha mRNA in the brain. mRNA for IL-1alpha was expressed in brain and liver samples from all animals. A severe PTRE caused a systemic acute phase response which was not apparent with a mild PTRE. The pattern of cytokine mRNA induction was similar following both drug treatments. However, the difference in APP production could be caused by a breakdown in the blood-brain barrier during severe PTRE allowing cytokine synthesised in the brain to enter the circulation and maintain a systemic response.     

Major acute phase response of haptoglobin and serum amyloid-P following experimental infection of mice with Trypanosoma brucei brucei

Investigation of the pathophysiological role of the systemic cytokines, including interleukin-1, interleukin-6 and tumour necrosis factor , in the host response to infection with African trypanosomes is hampered by the low and transient concentrations of these cytokines in plasma. One of the actions of these cytokines is the stimulation of hepatocyte production of acute phase proteins such as serum amyloid-P and haptoglobin. These acute phase proteins are more stable in the circulation than the cytokines and can be measured as a means of assessing the systemic cytokine response in the trypanosome-infected host. The plasma concentrations of serum amyloid-P and haptoglobin were measured in an experimental mouse model of Trypanosoma brucei brucei infection. Both serum amyloid-P and haptoglobin, increased markedly following infection. Peak concentrations of serum amyloid-P at 125 μg/ml and haptoglobin at 2 g/l were attained 10 to 12 days after infection. Thereafter, serum amyloid-P concentration decreased to approximately 40 μg/ml while the haptoglobin concentration remained elevated at approximately 1.5 g/l. The reactions of the serum amyloid-P and haptoglobin following experimental Trypanosoma brucei brucei infection in mice demonstrate that a major acute phase response has occurred indicating that the systemic cytokine network has been activated. Further studies are required to identify whether the response is stimulated by the parasite or indirectly by tissue damage.     

The induction of tyrosine aminotransferase activity and its use as an indirect assay for endotoxin in mice infected with Plasmodium vinckei petteri

Gauci R., Bennett D., Clark I. A. and Bryant C. 1982. The induction of tyrosine aminotransferase activity and its use as an indirect assay for endotoxin in mice infected with Plasmodium vinckei petteri. International Journal for Parasitology12: 279–284. It has been suggested that the malaria parasite contains an endotoxin-like substance which, by activating the reticuloendothelial system, causes much of the pathology of malaria when it is released into the host bloodstream during schizogony. In this study, an in vivo assay was developed, based on the determination of hepatic tyrosine aminotransferase activity in infected mice, to measure substances which act like endotoxin. Tyrosine aminotransferase is important in gluconeogenesis and is induced by endotoxin. Mice infected with Plasmodium vinckei petteri become sensitised to bacterial endotoxin as small amounts of endotoxin, without effect in uninfected mice, elevate tyrosine aminotransferase activity. The increase in sensitivity is gradual and progressive and is detectable by day 2 of the 9 day infection. Tyrosine aminotransferase activity is first lowered and then raised markedly during the course of the disease. A cell-free preparation of malaria parasites increased tyrosine aminotransferase activity when injected into mice sensitised with Coxiella antigen. These results are consistent with the hypothesis that parasitised red cells contain an endotoxin-like substance which directly or indirectly may be responsible for producing some of the symptoms of malaria in mice.     

Hepatic response to the oxidative stress induced by E. coli endotoxin: Glutathione as an index of the acute phase during the endotoxic shock

Reactive oxygen species are important mediators of cellular damage during endotoxic shock. In order to investigate the hepatic response to the oxidative stress induced by endotoxin, hepatic and plasma glutathione (total, GSH and GSSG), GSSG/GSH ratio as well as Mn-superoxide dismutase and catalase activities were determined during the acute and recovery phases of reversible endotoxic shock in the rat. A significant increase in liver and plasma total glutathione content was observed 5 h after endotoxin treatment (acute phase), followed by a diminution of these parameters below control values at 48 h (recovery phase). The significant increases of GSSG levels and GSSG/GSH ratio are indicative of oxidative stress occurring during the acute phase. Liver Mn-SOD activity showed a similar time dependency as the GSSG/GSH ratio; however, a marked decrease in the liver catalase activity was observed during the process. These results indicate the participation of liver glutathione in the response to endotoxin and the possible use of plasma glutathione levels and GSSG/GSH ratio as indicators of the acute phase during the endotoxic process. (Mol Cell Biochem 159: 115-121, 1996)     

Acute Phase Proteins in Response to <Emphasis Type="Italic">Dictyocaulus viviparus</Emphasis>Infection in Calves

Three experiments were carried out to examine the acute phase response, as measured by the acute phase proteins (APP) haptoglobin, serum amyloid A (SAA) and fibrinogen, in calves infected with lungworm, Dictyocaulus vivparus. In addition, eosinophil counts were analysed. Three different dose models were used in 3 separate experiments: I) 250 D. viviparus infective third stage larvae (L3) once daily for 2 consecutive days, II) 100 D. viviparus L3 once daily for 5 consecutive days, and III) 2000 L3 once. All 3 dose regimes induced elevated levels of haptoglobin, SAA and fibrinogen, although there was considerable variation both between and within experiments. A significant increase was observed in all 3 APP at one or several time points in experiment I and III, whereas in experiment II, the only significant elevation was observed for fibrinogen at one occasion. The eosinophil numbers were significantly elevated in all 3 experiments. The results show that lungworm infection can induce an acute phase response, which can be monitored by the selected APP. Elevated APP levels in combination with high numbers of eosinophils in an animal with respiratory disease may be used as an indicator of lung worm infection, and help the clinician to decide on treatment. However, high numbers of eosinophils and low levels of APP do not exclude a diagnosis of lungworm. Thus, lungworm infection may not be detected if measurements of APP are used to assess calf health in herds or individual animals.     

Hypotension and disseminated intravascular coagulation following intralesional bacillus Calmette-Guérin therapy for locally metastatic melanoma

Summary Four patients developed serious hypotension and signs of disseminated intravascular coagulation shortly after a second round of Tice bacillus Calmette-Guérin (BCG) injections into locally recurrent cutaneous melanoma satellite nodules. Each of these patients survived following intensive therapy with isoniazid, pyridoxine, steroids, pressors, antibiotics, and cardio-renal support including, in one case, three acute hemodialyses. Plasma specimens from two of the four patients caused gelation of lysate from the amebocytes ofLimulus polyphemus, indicating the presence of endotoxin or an endotoxin-like substance. In vitro studies on the BCG preparations led us to conclude that this endotoxin activity in the plasma is not the result of direct injection of endotoxin with the BCG preparation, but rather from release of endotoxin from endogenous sources, such as the intestinal tract during a period of relative hypotension following an allergic reaction. Prior immunity appeared to be the consistent factor in the toxic reactions reported herein. Finally, we present recommendations for serial monitoring of these patients and discuss the use of an alternative agent for intralesional therapy.     

Hemorphins Act as Homeostatic Agents in Response to Endotoxin-Induced Stress

The effect of synthetic LVV-hemorphin-7 and hemorphin-7 on hypothalamo-pituitary-adrenocortical axis activity in response to endotoxin-induced stress was studied. The intraperitoneal (ip) endotoxin (lipopolysaccaride, LPS) (0.5 mg/kg) administration in combination with hemorphin (1 mg/kg) induce significant decrease in plasma corticosterone and modest decrease in plasma levels of tumor necrosis factor-alpha (TNFα) in compare with elevated levels of both corticosterone and TNFα in plasma of rats received LPS administration alone. Increased activity of calcineurin in both plasma and brain of rats received ip administration of LPS, was recovered under LPS + hemorphin treatment. In two independent proteome analysis, using 2-dimensional fluorescence difference gel electrophoresis and the isotope coded protein label technology, peptidyl-prolyl cis-trans-isomerase A (cyclophilin A) was identified as regulated by hemorphins protein in mouse brain. A therapeutic potential of hemorphins and mechanisms of their homeostatic action in response to endotoxin-induced stress are discussed.     

重症急性胰腺炎患者早期肠内营养治疗的作用及价值探讨

目的:探讨经鼻空肠管早期行肠内营养(EN)在重症急性胰腺炎(S AP)治疗中的作用。方法:40例SAP患者随机分为治疗组和对照组,每组各20例,对照组给予常规治疗,治疗组在常规治疗的基础上加用肠内营养。观察两组治疗前后血清白蛋白和淀粉酶水平、血浆内毒素及肿瘤坏死因子TNF-α水平的变化情况。考察治愈率症、感染率、病死率、平均住院时间及费用。结果:治疗组患者行肠内营养后,血浆内毒素、TNF-α下降速度明显快于对照组P<0.05,感染率、平均住院时间与费用明显降低。结论:EN能改善ASP患者的营养状况,改善肠道黏膜屏障及降低炎性细胞因子分泌来加强治疗效果,是SAP重要治疗手段。     

重症急性胰腺炎患者血清IL-6水平与内毒素移位及肠黏膜紧密连接蛋白表达关系的研究

目的：大量研究表明重症急性胰腺炎（SAP）患者血清中高浓度IL-6 和肠黏膜低表达的紧密连接蛋白可促进内毒素移位的发生。本文主要研究重症胰腺炎患者血清IL-6 水平对内毒素移位和肠黏膜紧密连接蛋白表达的影响。方法：50 例重症胰腺炎患者,其中12 例在患病早期因结肠受累合并腹胀,对12 例结肠受累患者应用结肠镜行结肠灌洗进行腹腔减压,同时取结肠黏膜进行活组织检查。所有病人在治疗的第3 天,第7天,第10 天,第14 天抽取外周静脉血。40 例健康志愿者作为对照组。应用ELISA方法检测血清IL-6 水平,鲎试验（LAL）方法检测血清内毒素含量,应用免疫荧光和Western blotting 方法检测肠黏膜紧密连接蛋白表达水平。结果：SAP 患者血清IL-6 和内毒素含量明显高于健康对照组,而结肠黏膜紧密连接蛋白表达低于对照组;在临床治疗过程中,早期SAP 患者血清IL-6 和内毒素水平高于晚期（P 值均＜0.05）。SAP 早期血清高浓度的IL-6 与结肠黏膜紧密连接蛋白的低表达具有相关性,差异有统计学意义（r=0.735,P＜0.05）。结论：血清IL-6 水平可作为早期评价重症急性胰腺炎严重程度的一项指标,IL-6 水平与重症急性胰腺炎临床病程有相关性,可能导致肠道内毒素移位。     

Abnormal changes of plasma acute phase proteins in schizophrenia and the relation between schizophrenia and haptoglobin (Hp) gene

Summary. In this study we focused on detecting schizophrenia related changes of plasma proteins using proteomic technology and examining the relation between schizophrenia and haptoglobin (Hp) genotype. We investigated plasma proteins from schizophrenic subjects (n = 42) and healthy controls (n = 46) by two-dimensional gel electrophoresis (2-DE) in combination with mass spectrometry. To further reveal the genetic relationship between acute phase proteins (APPs) and schizophrenia disease, we tested Hp α1/Hp α2 (Hp 1/2) polymorphism and two single nucleotide polymorphisms (SNPs) of Hp, rs2070937 and rs5473, for associations with schizophrenia in the Chinese Han population. With the relatively high number of samples for 2-DE work, we found that four proteins in the family of positive APPs were all up-regulated in patients. In genetic association study, we found significant associations existing between schizophrenia and Hp polymorphisms, Hp 1/2 and rs2070937 variants. Schizophrenia is accompanied by both an altered expression of Hp protein and a different genotype distribution of Hp gene, demonstrating that Hp is associated with schizophrenia. The results from proteomic and genomic aspects both indicate that acute phase reaction is likely to be an aetiological agent in the pathophysiology of schizophrenia, but not just an accompanying symptom. The positive APPs are schizophrenic related proteins, with the highly concordant results on four positive APPs. The first two authors contributed equally.     

Elevated plasma concentrations of haptoglobin in European brown bears during hibernation

Haptoglobin (Hp), a hemoglobin-binding protein, is known as an acute phase protein and increases during the acute phase of inflammation in most mammals. We reported previously in brown bears that the mean Hp concentrations were higher in blood samples obtained in winter than those in spring. To examine a possible relation of the seasonal variations of Hp to hibernation, in the present study, we measured the plasma concentrations of Hp as well as some other acute phase proteins (alpha(2)-macroglobulin, alpha(1)-antitrypsin, C-reactive protein) in 6 European brown bears (Ursus arctos), from which blood samples were obtained at 5-6 different months of year including February, the time of hibernation. The Hp concentrations showed clear seasonal variations, being highest in February. The alpha(2)-macroglobulin concentrations also showed a similar but much smaller rise in February, but those of alpha(1)-antitrypsin and C-reactive protein did not show any seasonal variations. Our results suggest that the seasonal variation of plasma Hp concentration in brown bears is associated with a hibernation-specific mechanism more than that of acute phase response.     

Consequences of haemolysis without haptoglobin

Abstract

Haptoglobin (Hp), a conserved plasma glycoprotein, forms very stable soluble complexes with free plasma haemoglobin. Haemoglobin binding by haptoglobin is thought to be important in the rapid hepatic clearance of haemoglobin from the plasma and in the inhibition of glomerular filtration of haemoglobin. It is thought to reduce haemoglobin-induced renal damage during haemolysis. To evaluate these functions, Hp knockout (Hp^-/-) mice were created. The Hp^-/- mouse was generated by a standard gene replacement technique in mouse embryonic stem cells. These mice were evaluated with and without haemolysis using several parameters: mortality, haemoglobin clearance, renal tissue damage and function.

Hp^-/- mice were viable but had a small, significant reduction in postnatal viability. The lack of Hp did not impair clearance of free plasma haemoglobin. Induction of severe haemolysis by phenylhydrazine caused extensive haemoglobin precipitation in the renal tubular cells. However, haemoglobin precipitation in the kidney was not increased in Hp^-/- mice. Nevertheless, Hp^-/- mice were more susceptible to phenylhydrazine with a mortality rate of 55% in Hp^-/- mice versus 18% in Hp^+/+ mice. In general, phenylhydrazine-treated Hp^-/- mice suffered greater tissue damage, as evidenced by the induction of a hepatic acute phase response, resulting in increased plasma₁-acidic glycoprotein (AGP) levels and higher plasma malonaldehyde (MDA) and 4-hydroxy-2(E)-nonenal (HNE) levels. Gross pathological analysis indicated that the kidney was the most affected tissue in phenylhydrazine-treated Hp^-/- and Hp^+/+ mice, and Hp^-/- mice were more severely affected. They had lower mitotic indices in their kidneys, higher basal levels of renal lipid peroxidation, as evidenced by levels of malonaldehyde and 4-hydroxy-2(E)-nonenal (MDA/HNE) and elevated levels of 8-hydroxyguanine (but not other products of oxidative DNA damage). There also was increased induction of haem oxygenase-1. The more severe renal damage in Hp^-/- mice was also evident in the delayed erythropoietin gene expression and poorer renal clearance of [³H]-inulin. The reduction in glomerular filtration function in Hp ^+/+ and Hp^-/- mice could be restored to baseline by vasodilators (prazosin or diazoxide), implicating renal vasoconstriction as a major mechanism of acute renal failure during induced haemolysis.

These data suggest that Hp plays a pivotal role in reducing renal oxidative damage during haemolysis.     

Incidence and pathophysiological relevance of postoperative endotoxemia

Abstract Patients who underwent surgical procedures usually develop elevated body temperature, changes of plasma levels of some proteins, and leucocytosis. These alterations are summarized as the postoperative acute-phase reaction. Also endotoxin can induce the described phenomena suggesting that endotoxin may play a role concerning the induction of the acute phase reaction. In order to test that hypothesis we determined endotoxin plasma levels preoperatively and daily postoperatively in patients who were operated on because of goiter ( n = 20), colonic, pancreatic and gastric diseases ( n = 58). A significant increase of endotoxin plasma levels was found at the first and third day after abdominal surgery whereas after goiter surgery the increase revealed to be only very slight. However, the decrease between the first and second postoperative day in the latter group was again statistically significant suggesting postoperative endotoxemia even after minor operations. Furthermore a correlation between the amount of circulating endotoxin and pulmonary or infectious complications could be established in patients after major operations even at the first postoperative day suggesting a pathogenetic relevance of postoperative endotoxemia.     

Haptoglobin concentrations in free-range and temporarily captive juvenile steller sea lions

Haptoglobin (Hp) is an acute-phase protein synthesized in the liver that circulates at elevated concentrations in response to tissue damage caused by inflammation, infection, and trauma. As part of a larger study, sera Hp concentrations were measured in temporarily captive (n = 21) and free-range (n = 38) western stock juvenile Steller sea lions (Eumetopias jubatus) sampled from 2003 to 2006. Baseline Hp concentration at time of capture was 133.3 +/- 17.4 mg/dl. Temporarily captive animals exhibited a 3.2-fold increase in Hp concentrations during the first 4 wk of captivity, followed by a return to entry levels by week 5. Haptoglobin levels were not influenced by age, season, or parasite load. There was a significant positive correlation between Hp concentrations and white blood cell count (P < 0.001) and globulin levels (P < 0.001) and a negative correlation to red blood cell count and hematocrit (P < 0.001 for both). There was no correlation between Hp levels and platelet count (P = 0.095) or hemoglobin (P = 0.457). Routine blubber biopsies collected under gas anesthesia did not produce a measurable Hp response. One animal with a large abscess had an Hp spike of 1,006.0 mg/dl that returned to entry levels after treatment. In conclusion, serum Hp levels correlate to the stable clinical health status observed during captivity, with moderate Hp response during capture and initial acclimation to captivity and acute response to inflammation and infection.     

Gut-derived endotoxin translocation is the main aggravating mechanism of acute severe pancreatitis

Severe acute pancreatitis (SAP) is a serious systemic disease. It exacerbates when complicated with multiple organ dysfunction syndrome or failure (MODS or MOF). However, the aggravating mechanism of SAP is still unknown up to now. Study showed that maintaining integrity of intestinal mucosal barrier function by given effective antibiotics, selective digestive decontamination (SDD) and enteral nutrition therapy to the patients with SAP could significantly reduce infection of pancreatic necrotic tissue and improve the patient's outcome. Combining the findings of gut-derived bacteria in animals' pancreas, liver, spleen, mesenteric lymph nodes with increasing concentration of inflammatory cytokines and endotoxin in plasma with SAP, we hypothesize that gut-derived endotoxin translocation is the main aggravating mechanism of SAP. The hypothesis holds potential as a target for therapeutic intervention.     

The acute phase protein haptoglobin and its relation to oxidative status in piglets undergoing weaning-induced stress

Abstract

Haptoglobin (Hp) prevents the hemoglobin driven generation of hydroxyl radicals and lipid peroxides. Hp can reduce the neutrophil respiratory burst and is an antioxidative molecule in its own right. We aimed to evaluate Hp concentrations, oxidative stress and antioxidative capacity in blood during weaning and to characterise potential relationships between these parameters. Two batches of 10 piglets each (2 trials) weaned at the age of 27–30 days were fed a starter feed mix ad libitum. Blood samples were taken 1 week before weaning and at weekly intervals thereafter. Oxidative stress was monitored via the D-ROM^® system, antioxidative capacity was measured with the TEAC assay and Hp concentrations were measured by ELISA. Neutrophil phagocytic activity and oxidative burst were examined via flow-cytometry. Body weights were recorded weekly. Hp concentrations were increased in both trials post-weaning (P < 0.01); oxidative stress and oxidative burst were elevated in trial I (P < 0.005). In trial I, Hp and ROM values returned to baseline levels at 6 weeks post-weaning. The piglets in trial II showed respiratory symptoms and maintained elevated Hp concentrations. ROM values and Hp were related (r = 0.58; P < 0.01). Hp and body weight gain were inversely related post-weaning.     

CpG-DNA upregulates the major acute-phase proteins SAA and SAP

The acute-phase response is an immediate reaction of the host against invading microorganisms. We show here that oligodeoxynucleotides (ODNs) containing a CpG motif rapidly induce the major murine acute-phase proteins in vivo , i.e. serum amyloid A (SAA) and serum amyloid P (SAP). Serum levels of these proteins are elevated within 12 h and peak at 24 h after the injection of CpG-ODN or endotoxin. Liver cells produce the proteins with the same kinetics. Injection of interleukin 6 (IL-6), IL-1β and tumour necrosis factor α (TNF-α) induces SAA and SAP in vivo , but the CpG-ODN-mediated induction does not depend on the presence of the TNF receptor p55, as the acute-phase response in TNF receptor p55-deficient mice does not differ from that of wild-type mice. Aside from CpG-ODN, bacterial genomic DNA also induces the acute-phase response in LPS-resistant C3H/Hej mice. The induction of the major acute-phase proteins SAA and SAP is blocked by the simultaneous injection of CpG-ODN together with d -galactosamine ( d -GalN). As d -GalN sensitizes the host for the toxic effects of TNF-α, a possible mechanism could be the prevention of synthesis of the major acute-phase proteins SAA and SAP.     

Increase in a heat-shock protein from blood cells in response of nestling house martins (Delichon urbica) to parasitism: an experimental approach

Heat-shock proteins (HSPs) are synthesized by animals and plants in response to various stressors. The level of the HSP60 stress protein was measured from the cell fraction of peripheral blood obtained from nestling house martins (Delichon urbica) to test whether ectoparasitism increased the concentration of stress protein. We assessed HSP from nestlings raised in nests previously treated with an insecticide or infested with 50 martin bugs (Oeciacus hirundinis). In addition, haematozoa infections were checked in blood smears. Nestlings from parasite-infested nests, or nestlings infected with trypanosomes, had increased levels of HSP in their blood cells. Nestling growth as determined from wing length was negatively related to HSP60 levels and within-brood variation in wing length increased with increasing levels of the stress protein independently of treatment and infection by trypanosomes. These results suggest HSPs may play a role in host-parasite interactions, and that they can be used reliably for measuring physiological responses to parasites. Received: 4 February 1998 / Accepted: 4 May 1998