The importance of human FcyRI in mediating protection to malaria

The success of passive immunization suggests that antibody-based therapies will be effective at controlling malaria. We describe the development of fully human antibodies specific for Plasmodium falciparum by antibody repertoire cloning from phage display libraries generated from immune Gambian adults. Although these novel reagents bind with strong affinity to malaria parasites, it remains unclear if in vitro assays are predictive of functional immunity in humans, due to the lack of suitable animal models permissive for P. falciparum. A potentially useful solution described herein allows the antimalarial efficacy of human antibodies to be determined using rodent malaria parasites transgenic for P. falciparum antigens in mice also transgenic for human Fc-receptors. These human IgG1s cured animals of an otherwise lethal malaria infection, and protection was crucially dependent on human FcγRI. This important finding documents the capacity of FcγRI to mediate potent antimalaria immunity and supports the development of FcγRI-directed therapy for human malaria.

Generation of mutant leukaemia inhibitory factor (LIF)-IgG heavy chain fusion proteins as bivalent antagonists of LIF

Two leukaemia inhibitory factor (LIF) mutants, designated MH35-BD and LIF05, have been shown to have a capacity to inhibit the biological activities of not only human LIF (hLIF) but also other interleukin-6 (IL-6) subfamily cytokines such as human oncostatin M (hOSM). These cytokines share the same receptor complex in which the glycoprotein 130 (gp130) subunit is a common constituent. However, at low concentrations and in their monomeric forms, such molecules have a relatively short plasma half-life due to rapid clearance from the kidneys. Here, to prolong their serum half-lives, we have used a multi-step polymerase chain reaction (PCR) to fuse each of the LIF05 and MH35-BD cDNA fragments to a sequence encoding the Fc portion, and the hinge region, of the human immunoglobulin G (hIgG) heavy chain. The linking was achieved through an oligomer encoding a thrombin-sensitive peptide linker thus generating MH35-BD:Fc and LIF05:Fc, respectively. Both Fc fusion constructs were expressed in insect cell Sf21 and the proteins were purified by two successive affinity chromatography steps using nickel–nitrilotriacetic acid (Ni–NTA) agarose and protein A beads. The Ba/F3 cell-based proliferation assay was used to confirm that the proteins were biologically active. In addition, preliminary pharmacokinetics indicates that the Fc fusion constructs have a longer serum half-life compared to their non-fusion counterparts.

Middle East respiratory syndrome coronavirus antibody reactors among camels in Dubai, United Arab Emirates, in 2005

We tested, using a low starting dilution, sequential serum samples from dromedary camels, sheep and horses collected in Dubai from February/April to October of 2005 and from dromedary camels for export/import testing between Canada and USA in 2000-2001. Using a standard Middle East respiratory syndrome coronavirus (MERS-CoV) neutralization test, serial sera from three sheep and three horses were all negative while sera from 9 of 11 dromedary camels from Dubai were positive for antibodies supported by similar results in a MERS-CoV recombinant partial spike protein antibody ELISA. The two negative Dubai camels were both dromedary calves and remained negative over the 5 months studied. The six dromedary samples from USA and Canada were negative in both tests. These results support the recent findings that infection with MERS-CoV or a closely related virus is not a new occurrence in camels in the Middle East. Therefore, interactions of MERS-CoV at the human-animal interface may have been ongoing for several, perhaps many, years and by inference, a widespread pandemic may be less likely unless significant evolution of the virus allow accelerated infection and spread potential in the human population.

Characterization of antibody V segment diversity in the Tasmanian devil (Sarcophilus harrisii)

The Tasmanian devil (Sarcophilus harrisii) immune system has recently been under scrutiny because of the emergence of a contagious cancer, which has decimated devil numbers. Here we provide a comprehensive description of the Tasmanian devil immunoglobulin variable regions. We show that heavy chain variable (VH) and light chain variable (VL) repertoires are similar to those described in other marsupial taxa: VL diversity is high, but VH diversity is restricted and belongs only to clan III. As in other mammals, one VH and one Vλ germline family and multiple incomplete Vκ germline sequences were identified in the genome. High Vκ variation was observed in transcripts and we predict that it may have arisen by gene conversion and/or somatic mutations, as it does not appear to have originated from germline variation. Phylogenetic analyses revealed that devil VL gene segments are highly complex and ancient, with some lineages predating the separation of marsupials and eutherians. These results indicate that although the evolutionary history of immune genes lead to the expansions and contractions of immune gene families between different mammalian lineages, some of the ancestral immune gene variants are still maintained in extant species. A high degree of similarity was found between devil and other marsupial VH segments, demonstrating that they originated from a common clade of closely related sequences. The VL families had a higher variation than VH both between and within species. We suggest that, similar to other studied marsupial species, the complex VL segment repertoire compensates for the limited VH diversity in Tasmanian devils.