Low cellular response in vitro among subjects with long-term exposure to malaria transmission in Brazilian endemic areas.

Abstract

Abstract. The cellular and humoral immune responses to Plasmodium falciparum and P. vivax recombinant circumsporozoite (rCS) proteins were studied in two populations in the Brazilian malaria-endemic region. One group of subjects lived in an urban area that was free from the risk of malaria and was exposed to the disease through short visits to the endemic area. The other group had lived for approximately 10 years in a rural area, where they were continuously exposed to transmission. Proliferative responses to rCS proteins were observed in 50% of 16 adults not continuously exposed to malaria but in only five of 48 subjects (10%) resident in the transmission area. The antibody responses to rCS proteins were approximately 50% in both groups. The interferon-␥ (IFN-␥) response evaluated only among continuously exposed subjects was low. There was no association between the presence of antibodies and the detection of proliferative or IFN-␥ T cell responses. These findings suggest that continuous exposure to malaria in areas of low endemicity may lead to a specific decrease of the in vitro T cell function.

Analysis of Circumsporozoite Protein–specific Immune Responses Following Recent Infection With Plasmodium Vivax

“…46 It is worth noting that in a recent Brazilian study proliferative responses to recombinant CSP were observed in 50% of the adults not continuously exposed to malaria, but in only 10% of subjects from a transmission area. 47 As in our study, antibody responses were similar in both groups. These studies are very complementary and point to the likely effect of recent infection on immunomodulation/lymphocyte trafficking, and also highlighted the importance of timing of blood collection when analyzing T cell responses.…”

CD4+CD25+Foxp3+Regulatory T Cells, Dendritic Cells, and Circulating Cytokines in Uncomplicated Malaria: Do Different Parasite Species Elicit Similar Host Responses?

“…While an early proinflammatory response is required to reduce the parasite load, immunoregulatory mechanisms can prevent further organ damage once parasitemia is under control and may cause the suppression of T-cell responses to both malarial and unrelated antigens, which is often observed in malaria-exposed populations (2,17,18).…”

Efficient Development ofPlasmodiumLiver Stage–Specific Memory CD8+T Cells during the Course of Blood‐Stage Malarial Infection

“…This suggested that natural exposure to Plasmodium infection primes CD8 ϩ T cells specific for liver stages that were recalled by the recombinant vaccine [30]. Therefore, it was apparent that CD8 ϩ T cells against liver-stage antigens, albeit at low frequencies, are present in these vaccinees before vaccination and generally in individuals in malaria-endemic areas [31][32][33][34][35], where the development of immunity to liver stages is irrevocably associated with concomitant blood-stage parasitemia.…”