To determine mechanisms of neonatal parasite antigen (Ag)-specific immune suppression associated with placental Plasmodium falciparum infection, we isolated cord blood mononuclear cells (CBMCs) from Gabonese neonates born to mothers with differing histories of P. falciparum infection and performed ex vivo and in vitro studies to evaluate immune regulatory activity. We found increased ex vivo percentages of CD4(+)CD25(hi) and CD4(+)CD25(+)CTLA-4(+) cells and increased interleukin (IL)-10 responses to parasite Ag in vitro in CBMCs from neonates born to mothers with placental P. falciparum infection at delivery. Depleting CBMCs of CD4(+)CD25(+) cells before cell culture led to the abrogation of parasite Ag-specific IL-10 responses, to enhanced interferon- gamma responses, and to enhanced expression of CD25 on CD8(+) T cells and of major histocompatibility complex class I and II on monocytes. These data demonstrate that parasite Ag-specific CD4(+) regulatory cells are generated in utero as a consequence of placental P. falciparum infection.

Available evidence suggests that immune cells from neonates born to mothers with placental Plasmodium falciparum (Pf) infection are sensitized to parasite Ag in utero but have reduced ability to generate protective Th1 responses. In this study, we detected Pf Ag-specific IFN-γ+ T cells in cord blood from human neonates whose mothers had received treatment for malaria or who had active placental Pf infection at delivery, with responses being significantly reduced in the latter group. Active placental malaria at delivery was also associated with reduced expression of monocyte MHC class I and II in vivo and following short term in vitro coculture with Pf Ag compared with levels seen in neonates whose mothers had received treatment during pregnancy. Given that APC activation and Th1 responses are driven in part by IFN-γ and down-regulated by IL-10, we examined the role of these cytokines in modulating the Pf Ag-specific immune responses in cord blood samples. Exogenous recombinant human IFN-γ and neutralizing anti-human IL-10 enhanced T cell IFN-γ production, whereas recombinant human IFN-γ also restored MHC class I and II expression on monocytes from cord blood mononuclear cells cocultured with Pf Ag. Accordingly, active placental malaria at delivery was associated with increased frequencies of Pf Ag-specific IL-10+CD4+ T cells in cord blood mononuclear cell cultures from these neonates. Generation and maintenance of IL-10+ T cells in utero may thus contribute to suppression of APC function and Pf Ag-induced Th1 responses in newborns born to mothers with placental malaria at delivery, which may increase susceptibility to infection later in life.

No abstract

Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) mediates the adherence of P. falciparuminfected erythrocytes to placental syncytiotrophoblasts via interactions with chondroitin sulfate A (CSA), a characteristic of pregnancy-associated malaria. Pregnancy-associated malaria predicts increased susceptibility of newborns to malaria, and it is postulated that transplacental passage of parasite antigen induces immune regulatory activity in the neonate. We wished to examine the immune responsiveness to a CSA-binding domain of PfEMP1, the DBL-␥3 domain, in cord and maternal venous blood obtained from pregnancies with various histories of P. falciparum infection. We assessed in vitro T-cell cytokine and plasma immunoglobulin G (IgG) and IgM responses to four peptides corresponding to highly conserved regions of a DBL-␥3 domain common to central African parasite isolates. The presence of placental P. falciparum infection at delivery was associated with elevated frequencies of DBL-␥3 peptide-specific CD3 ؉ interleukin-10-positive T cells in cord blood, while treatment and clearance of infection prior to delivery was associated with elevated frequencies of CD3؉ gamma interferon-positive T cells. DBL-␥3 peptide-specific IgM antibodies were detected in 12 of 60 (20%) cord plasma samples from those born to mothers with P. falciparum infection during pregnancy. Consistent with polyclonal anti-PfEMP1 antibody responses that are associated with protection against pregnancy-associated malaria, the presence of maternal IgG antibodies with specificity for one of the DBL-␥3 peptides showed a parity-dependent profile. These data demonstrate that peptides corresponding to conserved regions of the DBL-␥3 domain of PfEMP1 are immunogenic in P. falciparum-infected mothers and their offspring.

Humans chronically infected with schistosomiasis usually have impaired parasite Ag-specific lymphocyte proliferation and IFN-gamma production that may facilitate persistence of the parasite while producing little clinical disease. The mechanisms that contribute to the immunologic hyporesponsiveness in these patients remain undefined. IL-10 has been shown to exert an inhibitory effect on cell-mediated immunity. To determine whether endogenous IL-10 has a role in regulating parasite-specific anergy in schistosomiasis, neutralizing anti-IL-10 added to PBMC from Schistosoma haematobium patients' enhanced adult worm (SWAP)- or egg Ag (SEA)-driven lymphocyte proliferation and/or IFN-gamma production by 2- to >100-fold in 32 of 38 subjects. In contrast, anti-IL-10 failed to significantly augment the mycobacterial Ag, purified protein derivative (PPD)-driven lymphocyte proliferation, or IFN-gamma production in 9 or 10 of 14 individuals, respectively. SWAP or SEA triggered IL-10 release from PBMC of both patients and healthy individuals; however, CD4+ cells were a significant source of IL-10 only in infected subjects. PPD relative to SWAP induced fivefold less IL-10 release by CD4+ cells (p < 0.01). A possible mechanism whereby IL-10 suppressed Ag-specific T cell responses was demonstrated by the ability of SWAP and not PPD to suppress B7 expression on PBMC. Anti-IL-10 completely inhibited the parasite Ag-induced down-regulation of B7 expression. These studies indicate that IL-10 contributes to parasite Ag-induced T cell hyporesponsiveness observed in patients with chronic schistosomiasis hematobia.

Memory CD8+ T cells play a significant role in mediating protective immunity from pathogens, particularly viruses and intracellular bacteria. Inducing the optimal response, from both a quantitative and qualitative perspective, has been a research priority for determining the effectiveness of new vaccines. Depending on the pathogen, central memory (TCM) or effector memory (TEM) may be more important in providing adequate protection. Therefore, when developing new vaccines, it is important to realize which memory CD8+ T cell subset is vital and potentially ‘drive’ the response to elicit a protective level ratio in favor of one subset. Here we describe the phenotype of vaccinia specific memory CD8+ T cells. TEMRA+ memory T cells produce the most IFN-γ of any memory subset and are present in individuals last vaccinated over 30 years ago. Concurrently, we address the development of memory CD8+ T cells upon administration of Dryvax, as well as new smallpox vaccines such as Modified Vaccinia Ankara (MVA) in a murine model. Previous studies have indicated that TEM appear to provide better secondary protection than TCM and the data presented here indicate that these cells are maintained long term (>30 years). Therefore, we propose that new smallpox vaccines, such as MVA, should elicit a memory cell population in favor of TEM similar to that induced by Dryvax or other traditional smallpox vaccines.

No abstract

Childhood apraxia of speech (CAS) is a severe and rare form of speech sound disorder (SSD) with an estimated prevalence of 0.01-2%. CAS typically occurs in isolation (sporadic), but may segregate in families with broader speech and language deficits. We hypothesized that disruptive genetic changes may be involved in the etiology of CAS, and were resolvable by examination of whole genome sequence. We sequenced 27 families with a CAS child within the Cleveland Family Speech and Reading Study, examining 101 individuals in all. CAS subjects displayed errors on single word articulation (75%), multisyllabic real word repetition (93%), multisyllabic non-word repetition (82%), and oral motor function (82%); many also exhibited problems with fine and gross motor skills. We identified 17 genomic regions including 19 unique structural variants (SVs) present in children with CAS. Three variants were shared across families, but the rest were unique; some events were de novo. In four families, siblings with milder phenotypes co-inherited the same SVs, suggesting that some SVs display variable expressivity. In an independent sample, we replicated eight SVs using microarray technology and found that many of these SVs were present in children with milder forms of SSD. Bioinformatic examination of the deletions/duplications identified four SVs with substantial functional consequences (cytobands 2q24.3, 6p12.3-6p12.2, 11q23.2-11q23.3, and 16p11.2). Of these, the 16p11.2 deletion is the most well-established variant that causes a broad array of neurological features. These discoveries show that SVs are a heterogeneous, but prevalent cause of CAS, identifiable by standard genetic testing.