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.

Pan-serotype diagnostic for foot-and-mouth disease using the consensus antigen of nonstructural protein 3B

An amino acid consensus sequence for the seven serotypes of foot-and-mouth disease virus (FMDV) nonstructural protein 3B, including all three contiguous repeats, and its use in the development of a pan-serotype diagnostic test for all seven FMDV serotypes are described. The amino acid consensus sequence of the 3B protein was determined from a multiple-sequence alignment of 125 sequences of 3B. The consensus 3B (c3B) protein was expressed as a soluble recombinant fusion protein with maltose-binding protein (MBP) using a bacterial expression system and was affinity purified using amylose resin. The MBP-c3B protein was used as the antigen in the development of a competition enzyme-linked immunosorbent assay (cELISA) for detection of anti-3B antibodies in bovine sera. The comparative diagnostic sensitivity and specificity at 47% inhibition were estimated to be 87.22% and 93.15%, respectively. Reactivity of c3B with bovine sera representing the seven FMDV serotypes demonstrated the pan-serotype diagnostic capability of this bioreagent. The consensus antigen and competition ELISA are described here as candidates for a pan-serotype diagnostic test for FMDV infection.