Peripheral blood samples of 138 co-habitants from 25 families with recently diagnosed cases of visceral leishmaniasis in the Metropolitan Region of Belo Horizonte, Minas Gerais, Brazil, were analyzed by indirect fluorescent antibody test (IFAT), rK39 and Leishmania chagasi Enzyme Linked Immunosorbent Assay (ELISA), intradermal skin-test and Polymerase Chain Reaction (PCR) over a 12-month period. The cumulative positivity was significantly higher by PCR (29.7%) than by IFAT, rK39 ELISA, L. chagasi ELISA and intradermal skin-test (5.1%, 6.5%, 14.5% and 2.9%, respectively). In addition, the cytokine profile was measured in 16 of the 138 volunteers, of whom eight were asymptomatic carriers and eight were non-infected co-habitants. The innate immunity cells from asymptomatic carriers displayed, upon in vitro antigenic stimulation, a modulated increase in cytokine synthesis that was distinct from that observed in non-infected volunteers. This study suggests that the identification of a large proportion of asymptomatic carriers is facilitated when more than one diagnostic method is applied and that a mixed pattern of immune response is correlated with clinical status of asymptomatic individuals. These observations suggest also that asymptomatic infection by L. chagasi is a frequent event and that control programs could benefit by including this indicator in their interventions.

SummaryOver past decades the 17DD yellow fever vaccine has proved to be effective in controlling yellow fever and promises to be a vaccine vector for other diseases, but the cellular and molecular mechanisms by which it elicits such broadbased immunity are still unclear. In this study we describe a detailed phenotypic investigation of major and minor peripheral blood lymphocyte subpopulations aimed at characterizing the kinetics of the adaptive immune response following primary 17DD vaccination. Our major finding is a decreased frequency of circulating CD19+ cells at day 7 followed by emerging activation/modulation phenotypic features (CD19 + and CD8 + cells further support this hypothesis. We hypothesize that this controlled microenviroment seems to be the key to prevent the development of serious adverse events, and even deaths, associated with the 17DD vaccine reported in the literature.

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Ten-month-old calves Bos taurus taurus were immunized with three doses of SBm7462 with saponin as an adjuvant at 30-day intervals and were evaluated for IgG isotypes, phenotype circulating lymphocytes and changes in the lymph nodes (LN). SBm7462 stimulated the production of predominantly IgG1-isotype IgG antibodies. The lymph nodes exhibited activation at the seventh day after the first immunization, with areas of paracortical and interfollicular hyperplasia and the early formation of germinal centers (GC). Fifteen days after the first immunization, the GC exhibited compartmentalization of cellular populations, a light zone (LZ), a dark zone (DZ) and a mantle. At the same time, hyperplasia of the medullary cords was observed with cells associating with DC cells. Seven days after the first immunization, apoptosis in the DZ and in the paracortical region became evident. By day 15, there was an increase in the medullary cords, which became more numerous at days 35 and 42. PAP-positive cells were found in the paracortical region, medullary cords and GC 7 days after the first immunization. At day 35, there were further strongly PAP-positive cells in the medullary cords. By comparison, none of these changes were observed in the lymph nodes of control groups at any of the days analyzed. The number of CD21(+) lymphocytes increased in the immunized groups after the first inoculation, with a maximum number observed at 15 and 10 days after the first and third immunizations, respectively. Compared to pre-immunization counts, the percentage of WC1(+) gammadelta T-lymphocytes displayed more variation, increasing 5 days after the second immunization but decreasing over the following days. According to the results, the synthetic anti Rhipicephalus microplus vaccine elicits a complete immune response being T-dependant.

ABSTRACT. Differences in cellular and humoral immunity in Zebu (Bos taurus indicus) and European (B. taurus taurus) cattle breeds, which may be related to differences in resistance or susceptibility to infectious or parasitic diseases, are largely unknown. This study aimed to perform a comparative analysis of innate and adaptive immunity of European (including Holstein, Brown Swiss, and Hereford) and Zebu (including Gir, Nelore, and Guzera) breeds, by assessing their peripheral blood leukocyte profiles (i.e., monocytes, eosinophils, and lymphocytes, including CD4 + and CD8 + T cells, and CD21 + B cells). Phenotypic profile of peripheral blood bovine leukocytesHigher frequencies of cells involved in innate immunity were observed in Zebu breeds, particularly monocytes and non-T and non-B cells (13.37 ± 0.9058 and 37.67 ± 1.55, respectively). This finding may contribute to the increased resistance of B. taurus indicus to certain infectious and parasitic diseases. Considering other leukocyte populations in the peripheral blood, among-breed variation was greater than differences between the two subspecies. This study will serve as a basis for further investigations regarding comparative immunology and resistance to infectious and parasitic diseases of cattle.