The use of a heterogeneously controlled mouse population reveals a significant correlation of acute phase parasitemia with mortality in Chagas disease.

Chagas disease develops upon infection with the protozoan parasite Trypanosoma cruzi and undergoes an acute phase characterized by massive parasite replication and the presence of parasites in the blood. This condition is known as acute phase parasitemia. This initial stage may result in a cure, in the development of the chronic stages of the disease or in the death of the infected host. Despite intensive investigation related to the characterization of the acute and chronic phases of the disease, the cause-effect relationship of acute phase parasitemia to the outcome of the disease is still poorly understood. In this study, we artificially generated a heterogeneously controlled mouse population by intercrossing F1 mice obtained from a parental breeding of highly susceptible A/J with highly resistant C57BL/6 mouse strains. This F2 population was infected and used to assess the correlation of acute phase parasitemia with the longevity of the animals. We used nonparametric statistical analyses and found a significant association between parasitemia and mortality. If males and females were evaluated separately, we found that the former were more susceptible to death, although parasitemia was similar in males and females. In females, we found a strong negative correlation between parasitemia and longevity. In males, however, additional factors independent of parasitemia may favor mouse mortality during the development of the disease. The correlations of acute phase parasitemia with mortality reported in this study may facilitate an appropriate prognostic approach to the disease in humans. Moreover, these results illustrate the complexity of the mammalian genetic traits that regulate host resistance during Chagas disease.

Myenteric plexus is differentially affected by infection with distinct Trypanosoma cruzi strains in Beagle dogs

Chagasic megaoesophagus and megacolon are characterised by motor abnormalities related to enteric nervous system lesions and their development seems to be related to geographic distribution of distinct Trypanosoma cruzi subpopulations. Beagle dogs were infected with Y or Berenice-78 (Be-78) T. cruzi strains and necropsied during the acute or chronic phase of experimental disease for post mortem histopathological evaluation of the oesophagus and colon. Both strains infected the oesophagus and colon and caused an inflammatory response during the acute phase. In the chronic phase, inflammatory process was observed exclusively in the Be-78 infected animals, possibly due to a parasitism persistent only in this group. Myenteric denervation occurred during the acute phase of infection for both strains, but persisted chronically only in Be-78 infected animals. Glial cell involvement occurred earlier in animals infected with the Y strain, while animals infected with the Be-78 strain showed reduced glial fibrillary acidic protein immunoreactive area of enteric glial cells in the chronic phase. These results suggest that although both strains cause lesions in the digestive tract, the Y strain is associated with early control of the lesion, while the Be-78 strain results in progressive gut lesions in this model.

Myenteric plexus is differentially affected by infection with distinct Trypanosoma cruzi strains in Beagle dogs.

Chagasic megaoesophagus and megacolon are characterised by motor abnormalities related to enteric nervous system lesions and their development seems to be related to geographic distribution of distinct Trypanosoma cruzi subpopulations. Beagle dogs were infected with Y or Berenice-78 (Be-78) T. cruzi strains and necropsied during the acute or chronic phase of experimental disease for post mortem histopathological evaluation of the oesophagus and colon. Both strains infected the oesophagus and colon and caused an inflammatory response during the acute phase. In the chronic phase, inflammatory process was observed exclusively in the Be-78 infected animals, possibly due to a parasitism persistent only in this group. Myenteric denervation occurred during the acute phase of infection for both strains, but persisted chronically only in Be-78 infected animals. Glial cell involvement occurred earlier in animals infected with the Y strain, while animals infected with the Be-78 strain showed reduced glial fibrillary acidic protein immunoreactive area of enteric glial cells in the chronic phase. These results suggest that although both strains cause lesions in the digestive tract, the Y strain is associated with early control of the lesion, while the Be-78 strain results in progressive gut lesions in this model.

Differential use of TLR2 and TLR9 in the regulation of immune responses during the infection with Trypanosoma cruzi.

Pathogens express ligands for several TLRs that may play a role in the induction or control of the inflammatory response during infection. Concerning Trypanosoma cruzi, the agent of Chagas disease, we have previously characterized glycosylphosphatidylinositol (GPI) anchored mucin-like glycoproteins (tGPI-mucin) and unmethylated CpG DNA sequences as TLR2 and TLR9 agonists, respectively. Here we sought to determine how these TLRs may modulate the inflammatory response in the following cell populations: F4/80(+)CD11b(+) (macrophages), F4/80(low)CD11b(+) (monocytes) and MHCII(+)CD11c(high) (dendritic cells). For this purpose, TLR2(-/-) and TLR9(-/-) mice were infected with Y strain of T. cruzi and different immunological parameters were evaluated. According to our previous data, a crucial role of TLR9 was evidenced in the establishment of Th1 response, whereas TLR2 appeared to act as immunoregulator in the early stage of infection. More precisely, we demonstrated here that TLR2 was mainly used by F4/80(+)CD11b(+) cells for the production of TNF-α. In the absence of TLR2, an increased production of IL-12/IL-23p40 and IFN-γ was noted suggesting that TLR2 negatively controls the Th1 response. In contrast, TLR9 was committed to IL-12/IL-23p40 production by MHCII(+)CD11c(high) cells that constitute the main source of IL-12/IL-23p40 during infection. Importantly, a down-regulation of TLR9 response was observed in F4/80(+)CD11b(+) and F4/80(low)CD11b(+) populations that correlated with the decreased TLR9 expression level in these cells. Interestingly, these cells recovered their capacity to respond to TLR9 agonist when MHCII(+)CD11c(high) cells were impeded from producing IL-12/IL-23p40, thereby indicating possible cross-talk between these populations. The differential use of TLR2 and TLR9 by the immune cells during the acute phase of the infection explains why TLR9- but not TLR2-deficient mice are susceptible to T. cruzi infection.

Estudo dos níveis plasmáticos de alfa-macroglobulinas durante a fase aguda da infecção por Trypanosoma cruzi / Study of the plasma levels of alpha-macroglobulins during the acute phase of infection for Trypanosoma cruzi

Analisou-se a resposta de fase aguda (RFA) à infecção experimental por T. cruzi, através de estudos dos níveis plasmáticos de uma família de proteínas de fase aguda (PFA), as alfa-macroglobulinas (AM) em diversas cepas de camundongos. As AM são importantes inibidores fisiológicos de proteases, tendo também atividade imunomodulatória. Para a realização deste estudo foi fundamental a elaboração de um método de ELISA de inibição extremamente sensível, permitindo a detecção de AM em pequenos volumes de plasma. O desenvolvimento deste ELISA viabilizou o acompanhamento individualizado de animais controle e infectados e a comparação das respostas de animais resistentes e suscetíveis à infecção. Os resultados obtidos demonstram que as AM são importantes PFA em duas das três cepas de camundongos isogênicos estudadas. Ficou demonstrado ainda que os padrões de síntese de AM durante a fase aguda são diferentes nas diversas cepas estudadas, embora sejam homogêneos entre animais de umamesma cepa. Os resultados indicam que as AM atuam como PFA também em animais geneticamente heterogêneas, embora nestes casos o nível e a cinética de síntese de A2M sejam extremamente variáveis. Não se observou a existência de correlação entre níveis de AM e resistência ou susceptibilidade à fase aguda da infecção por T. cruzi. Resultados preliminares obtidos com pacientes durante a fase aguda da infecção por T. cruzi demonstraram que as AM atuam como PFA também na doença de Chagas e que a síntese destas proteínas em humanos apresenta uma heterogeneidade comparável àquela sugerida pelos estudos experimentais. O fato de que as AM têm função imunomodulatória, associado à heterogeneidade de sua síntese durante a fase aguda da infecção por T. cruzi, confirmam a importância de estudos posteriores abordando o eventual envolvimento das AM nos diversos desenvolvimentos da doença de Chagas em sua fase crônica.

Reaçäo de fase aguda e parasitismo na veia central da supra-renal de chagásicos crônicos / Acute-phase reaction and parasitism in the central adrenal vein in Chagas' disease patients

The systemic reaction to severe trauma and/or infection, acute phase response (APR), are often associated with immunosuppression and reactivation of chronic latent infection. Our main purpose was to verify, in a group of 71 autopsied chronic chagasic with or without APR, the frequency of T. cruzi nests in the central vein of adrenal gland (CVAG). APR, defined by: 1) death secondary to sepsis and/or trauma plus, 2) bleeding stress gastric ulcerations or 3) spleen reactional state or 4) liver steatosis, was observed in 30 chronic chagasic (APR+). Weight, height and body mass index (BMI) were obtained. APR(+) chronic chagasic had worse nutritional status than APR(-) ones: weight = 49.0 vs 54.5 kg; BMI = 17.5 vs 20.6 kg/m2 (median p < 0.05). CVAG T. cruzi nests frequency were similar (43.3 per cent and 43.9 per cent , respectively) between both Groups. We conclude that APR(+) chronic chagasic had worse nutritional status than APR(-) ones, and that APR development did not change the CVAG T. cruzi nests frequency

[Acute-phase reaction and parasitism in the central adrenal vein in Chagas' disease patients]. / Reação de fase aguda e parasitismo na veia central da supra-renal de chagásicos crônicos.

The systemic reaction to severe trauma and/or infection, acute phase response (APR), are often associated with immunosuppression and reactivation of chronic latent infection. Our main purpose was to verify, in a group of 71 autopsied chronic chagasic with or without APR, the frequency of T. cruzi nests in the central vein of adrenal gland (CVAG). APR, defined by: 1) death secondary to sepsis and/or trauma plus, 2) bleeding stress gastric ulcerations or 3) spleen reactional state or 4) liver steatosis, was observed in 30 chronic chagasic (APR+). Weight, height and body mass index (BMI) were obtained. APR(+) chronic chagasic had worse nutritional status than APR(-) ones: weight = 49.0 vs 54.5 kg; BMI = 17.5 vs 20.6 kg/m2 (median p < 0.05). CVAG T. cruzi nests frequency were similar (43.3% and 43.9%, respectively) between both Groups. We conclude that APR(+) chronic chagasic had worse nutritional status than APR(-) ones, and that APR development did not change the CVAG T. cruzi nests frequency.