Immunity induced by Plasmodium vivax infections leads to memory T-cell recruitment and activation during subsequent infections. Here, we investigated the role of regulatory T cells (Treg) in coordination with the host immune response during P. vivax infection. Our results showed a significant increase in the percentage of FOXP31 Treg, IL-10-secreting Type I Treg (Tr1) and IL-10 levels in patients with acute P. vivax infection as compared with those found in either naïve or immune controls. The concurrent increase in the Treg population could also be reproduced in vitro using peripheral blood mononuclear cells from naïve controls stimulated with crude antigens extracted from P. vivax-infected red blood cells. Acute P. vivax infections were associated with a significant decrease in the numbers of DC, indicating a general immunosuppression during P. vivax infections. However, unlike P. falciparum infections, we found that the ratio of myeloid DC (MDC) to plasmacytoid DC (PDC) was significantly lower in acute P. vivax patients than that of naïve and immune controls. Moreover, the reduction in PDC may be partly responsible for the poor antibody responses during P. vivax infections. Taken together, these results suggest that P. vivax parasites interact with DC, which alters the MDC/PDC ratio that potentially leads to Treg activation and IL-10 release.Key words: Dendritic cell . IL-10 . Malaria . Plasmodium vivax . Regulatory T cell Eur. J. Immunol. 2008. 38: 2697-2705 DOI 10.1002 Immunity to infection 2697 IntroductionMalaria is a common tropical disease causing deaths among Plasmodium falciparum-infected children mainly in Sub-Saharan Africa [1]. P. falciparum causes malignant tertian malaria that accounts for most malaria-associated deaths, whereas P. vivax causes relapsing fever and the infection rarely becomes fatal. Although a better understanding of immunity is needed for the design of effective vaccines, immune regulation in the host during malaria infection is not fully understood, and few studies have been conducted in patients with P. vivax infections. Our recent study has shown that anti-P. vivax antibody levels were very low in immune individuals living in endemic area and in patients with acute P. vivax malaria. For the cell-mediated arm, an acute P. vivax infection was associated with the activation of memory T cells belonging to either a cytotoxic or helper phenotype [2]. Additionally, previous evidence [3,4] shows that immunization with pre-erythrocytic antigens can induce IFN-g release. This suggests that P. vivax can activate the immune system via the Th1 pathway. However, a possible suppressing mechanism arises from the activation of regulatory T cells (Treg) as has been shown in a murine malaria study [5]. Treg constitutively express CD25, which is the IL-2/a chain receptor [6]. Co-presentation of CD25 with forkhead box protein P3 (FOXP3) dictates the immune-suppressive role of Treg via the release of . Treg have been shown to alter the balance between myeloid dendritic cells (MDC) and plasmacytoi...

Asymptomatic leishmaniasis cases have continuously increased, especially among patients with HIV who are at risk to develop further symptoms of cutaneous and visceral leishmaniasis. Thus, early diagnosis using a simple, sensitive and reliable diagnostic assay is important because populations at risk mostly reside in rural communities where laboratory equipment is limited. In this study, the highly sensitive and selective determination of Leishmania infection in asymptomatic HIV patients was achieved using dual indicators (SYBR safe and gold-nanoparticle probe; AuNP-probe) in one-step LAMP method based on basic instruments. The assay can be simply evaluated under the naked eye due to clear interpretation of fluorescent emission of LAMP-SYBR safe dye-complex and colorimetric precipitate of specific AuNP-probes. The sensitivities and specificities of fluorescent SYBR safe dye and AuNP-probe indicators were equal, which were as high as 94.1 and 97.1%, respectively. Additionally, detection limits were 102 parasites/mL (0.0147 ng/µL), ten times more sensitivity than other related studies. To empower leishmaniasis surveillance, this inexpensive one-step SYBR safe and AuNP-LAMP assay is reliably fast and simple for field diagnostics to point-of-care settings, which can be set up in all levels of health care facilities including resource limited areas, especially in low to middle income countries.

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SummaryPlasmodium falciparum infection causes transient immunosuppression during the parasitaemic stage. However, the immune response during simultaneous infections with both P. vivax and P. falciparum has been investigated rarely. In particular, it is not clear whether the host's immune response to malaria will be different when infected with a single or mixed malaria species. Phenotypes of T cells from mixed P. vivax-P. falciparum (PV-PF) infection were characterized by flow cytometry, and anti-malarial antibodies in the plasma were determined by an enzyme-linked immunosorbent assay. We found the percentage of CD3 + d2 + -T cell receptor (TCR) T cells in the acutemixed PV-PF infection and single P. vivax infection three times higher than in the single P. falciparum infection. This implied that P. vivax might lead to the host immune response to the production of effector T killer cells. During the parasitaemic stage, the mixed PV-PF infection had the highest number of plasma antibodies against both P. vivax and P. falciparum. Interestingly, plasma from the group of single P. vivax or P. falciparum malaria infections had both anti-P. vivax and anti-P. falciparum antibodies. In addition, antigenic cross-reactivity of P. vivax or P. falciparum resulting in antibodies against both malaria species was shown in the supernatant of lymphocyte cultures cross-stimulated with either antigen of P. vivax or P. falciparum. The role of d2 Ϯ TCR T cells and the antibodies against both species during acute mixed malaria infection could have an impact on the immunity to malaria infection.

A novel and sensitive magnetic polymeric nanoparticle (MPNP)-polymerase chain reaction-colorimetry (magneto-PCR-colorimetry) technique was developed for detection of Vibrio cholerae ( V. cholerae ). The technique involved an amplification of V. cholerae DNA on the surface of an MPNP and then employed the intrinsic catalytic activity of the MPNP to detect the target gene by colorimetry. An amino-modified forward primer was covalently labeled onto the MPNP surface which would bind to PCR product during PCR cycling. By employing the catalytic activity of the MPNP, the analysis of PCR product bound MPNP yielded a sensitivity of 10(3) CFU/mL of V. cholerae in buffer system within 4 h. The specificity and efficiency of the technique were investigated by using various bacterial DNAs in drinking and tap water.