Malaria parasites within red blood cells digest host hemoglobin into a hydrophobic heme polymer, known as hemozoin (HZ), which is subsequently released into the blood stream and then captured by and concentrated in the reticulo-endothelial system. Accumulating evidence suggests that HZ is immunologically active, but the molecular mechanism(s) through which HZ modulates the innate immune system has not been elucidated. This work demonstrates that HZ purified from Plasmodium falciparum is a novel non-DNA ligand for Toll-like receptor (TLR)9. HZ activated innate immune responses in vivo and in vitro, resulting in the production of cytokines, chemokines, and up-regulation of costimulatory molecules. Such responses were severely impaired in TLR9^−/− and myeloid differentiation factor 88 (MyD88)^−/−, but not in TLR2, TLR4, TLR7, or Toll/interleukin 1 receptor domain–containing adaptor-inducing interferon β^−/− mice. Synthetic HZ, which is free of the other contaminants, also activated innate immune responses in vivo in a TLR9-dependent manner. Chloroquine (CQ), an antimalarial drug, abrogated HZ-induced cytokine production. These data suggest that TLR9-mediated, MyD88-dependent, and CQ-sensitive innate immune activation by HZ may play an important role in malaria parasite–host interactions.

With the severe acute respiratory syndrome epidemic of 2003 and renewed attention on avian influenza viral pandemics, new surveillance systems are needed for the earlier detection of emerging infectious diseases. We applied a “next-generation” parallel sequencing platform for viral detection in nasopharyngeal and fecal samples collected during seasonal influenza virus (Flu) infections and norovirus outbreaks from 2005 to 2007 in Osaka, Japan. Random RT-PCR was performed to amplify RNA extracted from 0.1–0.25 ml of nasopharyngeal aspirates (N = 3) and fecal specimens (N = 5), and more than 10 µg of cDNA was synthesized. Unbiased high-throughput sequencing of these 8 samples yielded 15,298–32,335 (average 24,738) reads in a single 7.5 h run. In nasopharyngeal samples, although whole genome analysis was not available because the majority (>90%) of reads were host genome–derived, 20–460 Flu-reads were detected, which was sufficient for subtype identification. In fecal samples, bacteria and host cells were removed by centrifugation, resulting in gain of 484–15,260 reads of norovirus sequence (78–98% of the whole genome was covered), except for one specimen that was under-detectable by RT-PCR. These results suggest that our unbiased high-throughput sequencing approach is useful for directly detecting pathogenic viruses without advance genetic information. Although its cost and technological availability make it unlikely that this system will very soon be the diagnostic standard worldwide, this system could be useful for the earlier discovery of novel emerging viruses and bioterrorism, which are difficult to detect with conventional procedures.

Poor health and malnutrition in preschool children are longstanding problems in Bangladesh. Gut microbiota plays a tremendous role in nutrient absorption and determining the state of health. In this study, metagenomic tool was employed to assess the gut microbiota composition of healthy and malnourished children. DNA was extracted from fecal samples of seven healthy and seven malnourished children (n = 14; age 2–3 years) were analyzed for the variable region of 16S rRNA genes by universal primer PCR followed by high-throughput 454 parallel sequencing to identify the bacterial phyla and genera. Our results reveal that the healthy children had a significantly higher number of operational taxonomic unit in their gut than that of the malnourished children (healthy vs. malnourished: 546 vs. 310). In malnourished children, bacterial population of the phyla Proteobacteria and Bacteroidetes accounted for 46 and 18%, respectively. Conversely, in healthy children, Proteobacteria and Bacteroidetes accounted for 5% and 44, respectively (p < 0.001). In malnourished children, the phylum Proteobacteria included pathogenic genera, namely Klebsiella and Escherichia, which were 174-fold and 9-fold higher, respectively, than their healthy counterpart. The predominance of potentially pathogenic Proteobacteria and minimal level of Bacteroidetes as commensal microbiota might be associated to the ill health of malnourished children in Bangladesh.

Proteins expressed on the surfaces of erythrocytes infected with Plasmodium falciparum help the parasite to evade the host immune system by acting as ligands for immune inhibitory receptors and thereby downregulating the immune response. The malaria parasite, Plasmodium falciparum, uses several strategies to evade the host immune system during infection. Here, the authors report that a subset of parasite-derived ligands from the RIFIN protein family, which are expressed on the surface of infected red blood cells (erythrocytes), engage the immune inhibitory receptors leucocyte immunoglobulin-like receptor B1 (LILRB1) or leucocyte-associated immunoglobulin-like receptor 1 (LAIR1), which leads to the downregulation of immune responses. Malaria is among the most serious infectious diseases affecting humans, accounting for approximately half a million deaths each year1. Plasmodium falciparum causes most life-threatening cases of malaria. Acquired immunity to malaria is inefficient, even after repeated exposure to P. falciparum2, but the immune regulatory mechanisms used by P. falciparum remain largely unknown. Here we show that P. falciparum uses immune inhibitory receptors to achieve immune evasion. RIFIN proteins are products of a polymorphic multigene family comprising approximately 150–200 genes per parasite genome3 that are expressed on the surface of infected erythrocytes. We found that a subset of RIFINs binds to either leucocyte immunoglobulin-like receptor B1 (LILRB1) or leucocyte-associated immunoglobulin-like receptor 1 (LAIR1). LILRB1-binding RIFINs inhibit activation of LILRB1-expressing B cells and natural killer (NK) cells. Furthermore, P. falciparum-infected erythrocytes isolated from patients with severe malaria were more likely to interact with LILRB1 than erythrocytes from patients with non-severe malaria, although an extended study with larger sample sizes is required to confirm this finding. Our results suggest that P. falciparum has acquired multiple RIFINs to evade the host immune system by targeting immune inhibitory receptors.

The restriction map of a BamHI DNA fragment that contains the recA gene of Escherichia coli has been established and a large portion of the fragment's nucleotide sequence has been determined. The coding region of the recA gene contains 1059 nucleotide residues and encodes a single protein of 353 amino acid residues. The amino acid sequence of the first five residues of the NH2 terminus of the recA protein agrees with the sequence predicted from the DNA sequence except for the absence of formylmethionine in the purified protein. Immediately after the coding sequence, there is a G+C-rich sequence with dyad symmetry followed by an A+T-rich sequence. These could signal termination of transcription. The site of initiation for synthesis in vitro of the recA messenger RNA has been determined by analysis of the 5' nucleotide sequence of [gamma-32P]ATP-labeled transcripts. The promoter region shos a high degree of symmetry and contains sequences commonly found in recognition and binding sites for RNA polymerase.