An engineered Plasmodium falciparum C-terminal 19-kilodalton merozoite surface protein 1 vaccine candidate induces high levels of interferon-gamma production associated with cellular immune responses to specific peptide sequences in Gambian adults naturally exposed to malaria

Infants' Peripheral Blood Lymphocyte Composition Reflects Both Maternal and Post-Natal Infection with Plasmodium falciparum

Maternal parasitoses modulate fetal immune development, manifesting as altered cellular immunological activity in cord blood that may be linked to enhanced susceptibility to infections in early life. Plasmodium falciparum typifies such infections, with distinct placental infection-related changes in cord blood exemplified by expanded populations of parasite antigen-specific regulatory T cells. Here we addressed whether such early-onset cellular immunological alterations persist through infancy. Specifically, in order to assess the potential impacts of P. falciparum infections either during pregnancy or during infancy, we quantified lymphocyte subsets in cord blood and in infants' peripheral blood during the first year of life. The principal age-related changes observed, independent of infection status, concerned decreases in the frequencies of CD4⁺, NK^dim and NKT cells, whilst CD8⁺, Treg and Teff cells' frequencies increased from birth to 12 months of age. P. falciparum infections present at delivery, but not those earlier in gestation, were associated with increased frequencies of Treg and CD8⁺ T cells but fewer CD4⁺ and NKT cells during infancy, thus accentuating the observed age-related patterns. Overall, P. falciparum infections arising during infancy were associated with a reversal of the trends associated with maternal infection i.e. with more CD4⁺ cells, with fewer Treg and CD8⁺ cells. We conclude that maternal P. falciparum infection at delivery has significant and, in some cases, year-long effects on the composition of infants' peripheral blood lymphocyte populations. Those effects are superimposed on separate and independent age- as well as infant infection-related alterations that, respectively, either match or run counter to them.

Immunomodulatory effects of recombinant BCG expressing MSP-1C of Plasmodium falciparum on LPS- or LPS+IFN-γ-stimulated J774A.1 cells

Macrophage phagocytosis is the first line of defense of the innate immune system against malaria parasite infection. This study evaluated the immunomodulatory effects of BCG and recombinant BCG (rBCG) strains expressing the C-terminus of the merozoite surface protein-1 (MSP-1C) of Plasmodium falciparum on mouse macrophage cell line J774A.1 in the presence or absence of lipopolysaccharide (LPS) or LPS + IFN-γ. The rBCG strain significantly enhanced phagocytic activity, production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, nitric oxide (NO), and inducible nitric oxide synthase (iNOS) as compared with parental BCG strain, and these activities increased in the presence of LPS and LPS+IFN-γ. Furthermore, the rBCG strain also significantly reduced the macrophage viability as well as the rBCG growth suggesting the involvement of macrophage apoptosis. Taken together, these data indicate that the rBCG strain has an immunomodulatory effect on macrophages, thus strengthen the rational use of rBCG to control malaria infection.