Identification of an acute-phase reactant in murine infections with Trypanosoma brucei

Profiling the Murine Acute Phase and Inflammatory Responses to African Snake Venom: An Approach to Inform Acute Snakebite Pathology

Snake envenoming causes rapid systemic and local effects that often result in fatal or long-term disability outcomes. It seems likely that acute phase and inflammatory responses contribute to these haemorrhagic, coagulopathic, neurotoxic, nephrotoxic and local tissue destructive pathologies. However, the contributory role of acute phase/inflammatory responses to envenoming is under-researched and poorly understood—particularly for envenoming by sub-Saharan African venomous snakes. To provide data to help guide future studies of human patients, and to explore the rationale for adjunct anti-inflammatory medication, here we used an in vivo murine model to systematically assess acute phase and inflammatory responses of mice to ten African snake venoms. In addition to investigating snake species-specific effects of venom on the cardiovascular system and other key organs and tissues, we examined the response to intravascular envenoming by acute phase reactants, including serum amyloid A, P-selectin and haptoglobin, and several cytokines. Venoms of the spitting (Naja nigricollis) and forest (N. melanoleuca) cobras resulted in higher acute phase and inflammatory responses than venoms from the other cobras, mambas and vipers tested. Naja nigricollis venom also stimulated a 100-fold increase in systemic interleukin 6. Thin blood films from venom-treated mice revealed species-specific changes in red blood cell morphology, indicative of membrane abnormalities and functional damage, lymphopenia and neutrophil leukocytosis. Our ex vivo assays with healthy human blood treated with these venoms identified that N. nigricollis venom induced marked levels of haemolysis and platelet aggregation. We conclude that African snake venoms stimulate very diverse responses in this mouse model of acute systemic envenoming, and that venoms of the African cobras N. nigricollis and N. melanoleuca, in particular, cause marked inflammatory and non-specific acute phase responses. We also report that several African snake venoms cause haemolytic changes. These findings emphasise the importance of understanding acute responses to envenoming, and that further research in this area may facilitate new diagnostic and treatment approaches, which in turn may lead to better clinical outcomes for snakebite patients.

Some serum acute phase proteins and immunoglobulins concentrations in calves with rotavirus, coronavirus, E. coli F5 and Eimeria species

The purpose of this study was to evaluate the changes in the serum concentrations of haptoglobin (Hp), serum amyloid A (SAA) and IgG, IgA in calves with diarrhea caused by rotavirus, coronavirus, Escherichia coli F5 and Eimeria species. The experiment was carried out on 40 diarrhoeic and 10 non-diarrhoeic calves (group C). A total of 13 calves were infected with rotavirus or coronavirus (group V), 12 calves with E. coli F5 (group B) and 15 calves with Eimeria species (group P). SAA and Hp levels of calves in groups V, B and P were statistically higher than group C (P<0.05). SAA and Hp levels of the group B and group P were significantly higher than the group V (P<0.05). SAA and Hp levels in group B were not significantly higher than the group P. The levels of IgG and IgA were found to be lower in groups B and V compared to other groups. There was a negative correlation between immunoglobulins and the levels of serum Hp and SAA in groups B and V (r=-0.315 and r=-0.369, respectively, P<0.05). Serum SAA, Hp, IgA and IgG levels could be useful for the diagnosis and differential diagnosis of diarrhea caused by rotavirus, coronavirus, E. coli F5 and Eimeria species.

Role of acute phase proteins in the immune response of rabbits infected with Trypanosoma evansi

The aim of this study was to characterize the response of acute phase proteins (APP) in rabbits experimentally infected with Trypanosoma evansi (T. evansi), and to relate the findings with serum immunoglobulins levels, in order to verify the relation between APP and the immune response of rabbits. A total of 12 animals were used in this experiment and divided into 2 groups, control and infected, of six rabbits each. The experimental period was 118 days, and blood was collected on days 0, 5, 20, 35, 65, 95 and 118 post-infection (PI). The infection with T. evansi stimulated APP and immunoglobulins production, once the infected animals showed an increase in C-reactive protein, haptoglobin, alpha 2-macroglobulin and IgM levels. The elevation in IgM levels observed in this study, when related to the increase in C-reactive protein and haptoglobin levels, suggests the involvement of these proteins in host defense against flagellated protozoa, with possible participation in the control of the parasitemia in rabbits infected with T. evansi.

Serum acute phase proteins in control and Theileria annulata infected water buffaloes (Bubalus bubalis)

This study was carried out to ascertain the changes in acute phase proteins (APPs) and pro-inflammatory cytokines in Theileria annulata infected water buffalo. Thirty infected water buffaloes and 20 parasitologically free were used. In the present study there was significant (P ≤ 0.05) increase in haptoglobin (Hp), serum amyloid A (SAA), ceruloplasmin, α1-acid glycoprotein (AGP) and fibrinogen levels (2.18 ± 0.29 g/l, 156.58 ± 3.48 mg/l, 31.23 ± 1.25mg/dl, 370.23 ± 33.21 mg/l and 16.17 ± 1.18 g/l, respectively) in T. annulata infected water buffaloes when compared to healthy ones (0.13 ± 0.01 g/l, 23.9 ± 0.56 mg/l, 21.23 ± 1.21 mg/dl, 240.53 ± 22.45 mg/l and 4.2 ± 0.1 6g/l, respectively). Moreover, there was significant (P ≤ 0.05) increase in the levels of TNF-α, IL-1α, IL-6, IL-12, IL-1β and IFN-γ (2.55 ± 0.12 ng/ml, 98.32 ± 4.21 pg/ml, 152.32 ± 5.62 pg/ml, 26.44 ± 1.43 ng/ml, 240.33 ± 20.45 pg/ml and 123.65 ± 5.67 pg/ml, respectively) in T. annulata infected water buffaloes when compared to healthy ones (0.42 ± 0.04 ng/ml, 55.32 ± 3.21 pg/ml, 88.23 ± 3.21 pg/ml, 7.45 ± 0.67 ng/ml, 98.33 ± 3.45 pg/ml and 34.76 ± 1.56 pg/ml, respectively). There was also significant decrease (P ≤ 0.05) in the Hb content, PCV%, RBCs and WBCs counts in the diseased water buffaloes compared to the control ones. Neutropenia, eosinopenia, lymphopenia, monocytopenia and thrombocytopenia were also recorded. The biochemical changes revealed significant (P ≤ 0.05) elevation in the levels of AST, ALT, ALP, LDL-c, VLDL-c, BHBA and NEFA, with significant (P ≤ 0.05) decrease in the levels of total proteins, albumin, globulins, cholesterol, triglyceride, glucose, G6PD, calcium and phosphorus in T. annulata infected water buffaloes when compared to healthy ones. It could be concluded that APPs and pro-inflammatory cytokines could be used as a valuable biomarkers in T. annulata infected water buffaloes (Bubalus bubalis).

Changing patterns of acute phase proteins and inflammatory mediators in experimental caprine coccidiosis

This experiment was conducted to assess the changing patterns and relative values of acute phase proteins and inflammatory cytokines in experimental caprine coccidiosis. Eighteen newborn kids were allocated to 3 equal groups. Two groups, A and B, were inoculated with a single dose of 1×10(3) and1×10(5) sporulated oocysts of Eimeria arloingi, respectively. The third group, C, received distilled water as the control. Blood samples were collected from the jugular vein of each kid in both groups before inoculation and at days 7, 14, 21, 28, 35, and 42 post-inoculation (PI), and the levels of haptoglobin (Hp), serum amyloid A (SAA), TNF-α, and IFN-γ were measured. For histopathological examinations, 2 kids were selected from each group, euthanized, and necropsied on day 42 PI. Mean Hp concentrations in groups A and B (0.34 and 0.68 g/L) at day 7 PI were 3.2 and 6.3 times higher than the levels before inoculation. The mean SAA concentrations in groups A and B (25.6 and 83.5 µg/ml) at day 7 PI were 4.2 and 13.7 times higher than the levels before inoculation. The magnitude and duration of the Hp and SAA responses correlated well with the inoculation doses and the severity of the clinical signs and diarrhea in kids. These results were consistent with the histopathological features, which showed advanced widespread lesions in group B. In both groups, significant correlations were observed for TNF-α and IFN-γ with SAA and Hp, respectively. In conclusion, Hp and SAA can be useful non-specific diagnostic indicators in caprine coccidiosis.

Divergent antimicrobial peptide (AMP) and acute phase protein (APP) responses to Trypanosoma congolense infection in trypanotolerant and trypanosusceptible cattle

African animal trypanosomiasis (AAT) is endemic across Sub-Saharan African and is a major constraint to livestock production. The ability of certain cattle breeds to remain productive despite infection is known as trypanotolerance; however, the underlying immune mechanisms contributing to this trait remain poorly understood. Antimicrobial peptides (AMPs) and acute phase proteins (APPs) are evolutionarily conserved effector molecules of the innate immune system that have important roles in the resolution of infection and activation of the adaptive immune response. Expression levels of AMP genes (TAP, LAP, BNBD4, DEFB1, DEFB5 and LEAP2) and APP genes (HP, CP, AGP, LBP, SAA3 and CRP) were investigated using real time quantitative reverse transcription PCR (qRT-PCR) in peripheral blood mononuclear cells (PBMC) isolated from two breeds of African cattle (trypanotolerant N'Dama and trypanosusceptible Boran), experimentally infected with Trypanosoma congolense. Haptoglobin and serum amyloid A (SAA) were also measured in plasma using quantitative protein assays. Results demonstrated that tracheal antimicrobial peptide (TAP) gene expression increased by 32-fold in Boran, compared to only 3-fold in N'Dama, by 14 days post-infection (dpi) and rising to 136-fold at 29 dpi in Boran, compared to 47-fold in N'Dama (P<0.05). Protein expression levels of SAA are elevated in N'Dama, rising to 163 microg/ml at 14 dpi compared with 72 microg/ml in Boran. The SAA expression profile mirrors the wave of parasitaemia detected in N'Dama. Seven single nucleotide polymorphisms (SNPs) were identified in the promoter regions of the SAA3 and SAA4 genes, which are predicted to affect transcription factor binding and thereby contributing to the differential patterns of expression detected between the breeds. Whereas elevated TAP expression is a conserved component of the innate immune response to infection in both breeds, higher SAA expression levels may contribute toward trypanotolerance in N'Dama.

The protozoan parasite, Theileria annulata, induces a distinct acute phase protein response in cattle that is associated with pathology

Acute phase proteins (APP) are synthesised in the liver in response to the systemic presence of high levels of pro-inflammatory cytokines. Bacteria are considered to be strong inducers of APP whereas viruses are weak or non-inducers of APP. Very few reports have been published on APP induction by parasites. Here, we report that the tick-borne protozoan parasite of cattle, Theileria annulata, induced an atypical acute phase response in cattle. Following experimental infection, serum amyloid A (SAA) appeared first, followed by a rise in alpha(1) acid glycoprotein (alpha(1)AGP) in all animals, whereas haptoglobin, which is a major APP in cattle, only appeared in some of the animals, and generally at a low level. All three APP only became elevated around or after the appearance of schizonts in draining lymph nodes and after the first observed temperature rise. Increased alpha(1)AGP levels coincided with the appearance of piroplasms. The production of SAA and alpha(1)AGP correlated strongly with each other, and also with some clinical measures of disease severity including the time to fever, development of leucopaenia, parasitaemia and mortality. These results are consistent with the hypothesis that T. annulata causes severe pathology in susceptible cattle by inducing high levels of pro-inflammatory cytokines.

Activity of human trypanosome lytic factor in mice

The inability of the cattle pathogen Trypanosoma brucei brucei to infect humans is due to an innate factor in human serum termed Trypanosome Lytic Factor (TLF). Human haptoglobin-related protein is the proposed toxin in TLF and can exist either as a component of a minor subclass of high-density lipoprotein (TLF-1) or as a lipid free, high molecular weight protein complex (TLF-2). The trypanolytic activity of both TLF-1 and TLF-2 has been studied in vitro but their relative contributions to protection against T. b. brucei infection in vivo has not been established. In the present studies we show that treatment of T. b. brucei infected mice with TLF-1 resulted in a dose dependent decrease in parasite numbers but did not affect parasite numbers in mice infected with Trypanosoma brucei rhodesiense, the causative agent of the human sleeping sickness. Similarly, pretreatment of mice with TLF-1 resulted in protection against a challenge by T. b. brucei but had no effect on T. b. rhodesiense challenge. Induction of the acute phase protein haptoglobin, a natural antagonist of TLF-1, diminished but did not abolish the protection against trypanosome challenge. In addition, haptoglobin knockout mice showed higher levels of TLF-1 mediated protection against a T. b. brucei challenge. These results suggest that while TLF-1 is active in vivo, even in the presence of elevated levels of haptoglobin, its activity is modulated in a dose dependent fashion by haptoglobin in the circulation.

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.

Characterization and sequencing of a respiratory burst-inhibiting acid phosphatase from Francisella tularensis

Acid phosphatases (Acp) of intracellular pathogens have recently been implicated as virulence factors that enhance intracellular survival through suppression of the respiratory burst. We describe here the identification, purification, characterization, and sequencing of a novel burst-inhibiting acid phosphatase from the facultative intracellular bacterium, Francisella tularensis. Similar to other the burst-inhibiting Acps, F. tularensis Acp (AcpA) is tartrate-resistant and has broad substrate specificity. The AcpA enzyme is unique, however, in that it is easily released from the bacterial cell in soluble form, is a basic enzyme, suppresses the respiratory burst of not only fMet-Leu-Phe but also phorbol 12-myristate 13-acetate-stimulated neutrophils and does not fit into any of the three currently recognized classes of acid phosphatase. We also report the complete nucleotide sequence of the gene acpA, encoding AcpA, and the deduced primary structure of its encoded polypeptide. Comparative sequence analyses of AcpA is discussed. To our knowledge, this is the first report describing the cloning and sequencing of a burst-inhibiting acid phosphatase.