Evaluation of the influence of tissue parasite density on hematological and phenotypic cellular parameters of circulating leukocytes and splenocytes during ongoing canine visceral leishmaniasis.

During Leishmania infection, tissue parasitism at different sites may differ and imply distinct immunopathological patterns during canine visceral leishmaniasis (CVL). For this reason, we have assessed by flow cytometry the impact of spleen and skin parasite density on the phenotypic profile of splenocytes and circulating leukocytes of 40 Brazilian dogs naturally infected by Leishmania chagasi categorized according to splenic and cutaneous parasite load. Our major statistically significant findings demonstrated that dogs with splenic high parasitism presented a significant decrease in absolute counts of CD5+ T lymphocytes in comparison with dogs presenting splenic medium parasitism. Moreover, a decrease in the absolute number of circulating monocytes was observed as a hallmark of high parasitism. The increased frequency of CD8+ T cells is associated with low splenic parasitism during CVL. Although we did not found any significant differences between the immunophenotypic analysis performed in circulating lymphocytes according to cutaneous parasite load, there were negative correlations between CD5+ and CD8+ T cells and cutaneous parasite density reemphasizes the role of T cell-mediated immune response in resistance mechanisms during ongoing CVL. These results add new insights about the pathogenesis of CVL and may help in the establishment of additional tools for future studies on drugs and vaccine approaches.

Analysis of the cytokine profile in spleen cells from dogs naturally infected by Leishmania chagasi.

Recent studies suggest that asymptomatic dogs infected with canine visceral leishmaniasis (CVL) develop a Th1 immunological profile whilst oligosymptomatic and symptomatic CVL-infected animals present a Th2 profile. In the present study, an RT-PCR method has been standardised and employed to evaluate the frequency and the semi-quantitative level of expression of the cytokines IL-4, IL-10, IL-12, INF-gamma and TNF-alpha in splenocytes of 30 dogs naturally infected with Leishmania chagasi and of 7 non-infected dogs (NID). An increase in the level of expression of IL-12 (p=0.059) was detected in all CVL-infected dogs compared with NID. In dogs exhibiting high parasitism, the frequency of expression of IL-10 was higher (p=0.011) than in animals presenting low parasitism or medium parasitism (MP) and in NID animals, whilst the level of expression of IL-10 was higher (p=0.0094) than in animals exhibiting MP and in the NID group. Positive correlations between the levels of expression of IL-10 with respect to the progression of the disease (IL-10: r=0.3510; p=0.0337) and the levels of expression of IL-10 and INF-gamma increase in parasitism (IL-10: r=0.3428; p=0.0438 and INF-gamma: r=0.4690; p=0.0045) were observed. Such data suggest that CVL is marked by a balanced production of Th1 and Th2 cytokines, with a predominant accumulation of IL-10 as a consequence of an increase in parasitic load and progression of the disease, and INF-gamma was related with the increase in parasitic load.

Phenotypic features of circulating leucocytes as immunological markers for clinical status and bone marrow parasite density in dogs naturally infected by Leishmania chagasi.

Canine visceral leishmaniasis (CVL) manifests itself as a broad clinical spectrum ranging from asymptomatic infection to patent severe disease. Despite relevant findings suggesting changes on lymphocytes subsets regarding the CVL clinical forms, it still remains to be elucidated whether a distinct phenotypic profile would be correlated with degree of tissue parasite density. Herein, we have assessed the correlation between the clinical status as well as the impact of bone marrow parasite density on the phenotypic profile of peripheral blood leucocytes in 40 Brazilian dogs naturally infected by Leishmania chagasi. Our major findings describe the lower frequency of B cells and monocytes as the most important markers of severe CVL. Our main statistically significant findings reveal that the CD8(+) T cell subset reflects most accurately both the clinical status and the overall bone marrow parasite density, as increased levels of CD8(+) lymphocytes appeared as the major phenotypic feature of asymptomatic disease and dogs bearing a low parasite load. Moreover, enhanced major histocompatibility complex (MHC)-II density as well as a higher CD45RB/CD45RA expression index seems to represent a key element to control disease morbidity. The association between clinical status, bone marrow parasitism and CD8(+) T cells re-emphasizes the role of the T cell-mediated immune response in the resistance mechanisms during ongoing CVL. Higher levels of circulating T lymphocytes (both CD4(+) and CD8(+) T cells) and lower MHC-II expression by peripheral blood lymphocytes seem to be the key for the effective immunological response, a hallmark of asymptomatic CVL.

Activated protein C resistance is uncommon in sudden death due to pulmonary embolism.

Activated protein C resistance (APC-R) is the most common inherited defect of the coagulation system known to date, affecting 3-5% of Americans. It is an autosomal dominant disorder associated with an increased risk of venous thrombosis and is reportedly found in 21% of individuals with deep venous thrombosis. Medical examiners are in a unique position to make the diagnosis since a fatal pulmonary embolism may be the first manifestation of the disorder. This study examines the prevalence of APC-R in individuals who die suddenly of pulmonary embolism to help medical examiners decide if routine testing is indicated. We examined 66 cases of sudden death due to pulmonary embolism seen at the Bexar County Forensic Science Center in San Antonio, Texas, from 1993-1997. The median age was 46 years with a range of 14 to 93 years. Fifty-three percent were Caucasian, 24% were African-American, and 23% were Hispanic. Twenty-seven percent had no known risk factors for pulmonary embolism. Whole blood was tested for the factor V codon 506Q mutation responsible for APC-R using polymerase chain reaction. The prevalence of APC-R was 4.5%, which is similar to the prevalence of APC-R in the general American population. These data imply that individuals with APC-R are not in increased risk for sudden death due to pulmonary embolism, or, conversely, that most fatal pulmonary emboli seen in the medical examiner setting are not induced by APC-R. Routine postmortem testing for the factor V 506Q mutation does not appear indicated at this time, given the low prevalence and high cost of testing.