Between 1996 and 2001, the prevalence of placental malaria in pregnant women living in Yaounde, Cameroon and its effect on pregnancy outcome were evaluated with respect to gravidity and maternal age. Results showed that 19.9% of the women had placental malaria at delivery. After adjusting for relevant covariates, the major risk factor for placental malaria was an age < 25 years old. Placental malaria significantly increased the prevalence of anemia in women regardless of gravidity or age. In addition, the mean infant birth weight was lower and the percentage of pre-term deliveries (PTDs) and low birth weight (LBW) babies were higher in primigravidae and women < 20 years of age who had placental malaria. However, in a multivariate regression model taking relevant covariates into consideration, the major risk factor for PTDs was maternal anemia, and maternal anemia as well as first and second pregnancies were important risk factors for LBW babies.

The immune system has numerous mechanisms that it can use to combat pathogens and eliminate infections. Nevertheless, studies of immune responses often focus on single pathways required for protective responses. We applied microarray analysis of RNA in order to investigate the types of immune responses produced against infection with the intestinal pathogen Giardia duodenalis. Infection with G. duodenalis is one of the most common causes of diarrheal disease in the world. While several potential antiparasitic effector mechanisms, including complement lysis, nitric oxide (NO), and α-defensin peptides, have been shown to inhibit parasite growth or kill Giardia in vitro, studies in vivo have thus far shown clear roles only for antibody and mast cell responses in parasite control. A total of 96 transcripts were identified as being upregulated or repressed more than 2-fold in the small intestine 10 days following infection. Microarray data were validated using quantitative PCR. The most abundant category of transcripts was antibody genes, while the most highly induced transcripts were all mast cell proteases. Among the other induced transcripts was matrix metalloprotease 7 (Mmp7), the protease responsible for production of mature α-defensins in mice. While infections in Mmp7-deficient mice showed only a small increase in parasite numbers, combined genetic deletion of Mmp7 and inducible nitric oxide synthase (iNOS, Nos2) or pharmacological blockade of iNOS in Mmp7-deficient mice resulted in significant increases in parasite loads following infection. Thus, α-defensins and NO are redundant mechanisms for control of Giardia infections in vivo.

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Infection with Giardia duodenalis is one of the most common causes of diarrheal disease in the world. While numerous studies have identified important contributions of adaptive immune responses to parasite control, much less work has examined innate immunity and its connections to the adaptive response during this infection. We explored the role of complement in immunity to Giardia using mice deficient in mannose-binding lectin (Mbl2) or complement factor 3a receptor (C3aR). Both strains exhibited delayed clearance of parasites and a reduced ability to recruit mast cells in the intestinal submucosa. C3aR-deficient mice had normal production of antiparasite IgA, but ex vivo T cell recall responses were impaired. These data suggest that complement is a key factor in the innate recognition of Giardia and that recruitment of mast cells and activation of T cell immunity through C3a are important for parasite control. Giardia duodenalis is one of the most common protozoan infections of humans as well as other mammals throughout the world and is a leading cause of diarrheal disease in these species (1-3). Symptomatic infections occur in ϳ20 to 80% of humans with positive stool samples and are characterized by nausea, vomiting, epigastric pains, and diarrhea (1, 2, 4, 5). These symptoms are associated with nutrient malabsorption and can lead to weight loss and malnutrition in children, exposing this vulnerable group to failure to thrive and developmental problems (6, 7). Disease resolves spontaneously in Ͼ85% of cases. In certain cases, in spite of a healthy and fully developed immune system, the acute phase of the disease develops into chronic disease. In these cases, symptoms of the disease will reappear for short and recurrent periods (3,4,8). The mechanisms explaining interactions between the host and the parasite leading to parasite clearance and disease pathogenesis are poorly understood.Studies of immune responses against Giardia have demonstrated important roles for both innate and adaptive immunity (7, 9). Antibody production following infection is robust, and IgA is very effective at eliminating parasites (9). Antibody-independent roles of T cells can also eliminate infections (10). Early studies indicated that Giardia trophozoites are susceptible to killing by factors in nonimmune human serum, milk, and intestinal fluid (11-13). Recently, killing by normal serum was demonstrated to involve the lectin pathway (14), consistent with the expression of N-acetylglucosamine (GlcNAc) on the surface of trophozoites (15,16). Studies of cells of the innate immune system indicate that macrophages, dendritic cells, mast cells, and intestinal epithelial cells are all involved. In vitro macrophages have been shown to be capable of ingesting Giardia, and we recently showed that macrophages accumulate in the lamina propria following infection (17, 18). Bone marrow-derived dendritic cells mature in response to Giardia extracts, but cytokine production in response to Toll-like receptor (TLR) agonists is modulated toward interle...