Phylogenetic analysis of porcine circovirus type 2 (PCV2) pre- and post-epizootic postweaning multisystemic wasting syndrome (PMWS)

The porcine circovirus type 2 (PCV2) genome encodes three major open reading frames (ORFs) encoding the replicase proteins (ORF1), the viral capsid protein (ORF2), and a protein with suggested apoptotic activity (ORF3). Previous phylogenetic analyses of complete genome sequences of PCV2 from GenBank have demonstrated 95–100% intra-group nucleotide sequence identity. However, although these isolates were readily grouped into clusters and clades, there was no correlation between the occurrence of specific PCV2 genotypes and the geographic origin or health status of the pig. In the present study, a unique dataset from a field study spanning the years pre and post the recognition of postweaning multisystemic wasting syndrome (PMWS) in Sweden was utilized. Using this dataset it was possible to discriminate three Swedish genogroups (SG1-3) of PCV2, of which SG1 was recovered from a pig on a healthy farm ten years before the first diagnosis of PMWS in Sweden. The SG1 PCV2/ORF2 gene sequence has been demonstrated to exhibit a high genetic stability over time and has subsequently only been demonstrated in samples from pigs on nondiseased farms. In contrast, SG2 was almost exclusively found on farms that had only recently broken down with PMWS whereas the SG3 genogroup predominated in pigs from PMWS-affected farms. These results further support the results obtained from earlier in vitro and in vivo experimental models and suggest the association of specific PCV2 genogroups with diseased and nondiseased pigs in the field. The GenBank accession numbers of the 37 sequences reported in this paper are: Sw64-EF184228; SwN2-EF184227; SwN1-EF184226; Sw3(03)-EF184225; Sw20-EF184224; Sw19-EF184223; Sw52-EF184222; Sw51-EF184221; Sw93(ab)-EF184220; Sw93′(bb)-EF371551; Sw4(04)-EF371518; Sw2(02)-EF371519; Sw71-EF371520; Sw79-EF371521; Sw81-EF371522; Sw78-EF371523; No4-EF371524; No2-EF371525; No3-EF371526; No5-EF371527; Sw5-EF371528; Sw40-EF371529; Sw42-EF371530; Sw24-EF371531; Sw29-EF371532; Sw32-EF371533; Sw35-EF371534; Sw68-EF371535; Sw73-EF371536; Sw74-EF371537; Sw75-EF371538; Sw82-EF371539; Sw31-EF371540; It1-EF371547; It5-EF371548; It16-EF371549; It18-EF371550.     

Targeted expression of a multifunctional chimeric neurotrophin in the lesioned sciatic nerve accelerates regeneration of sensory and motor axons

Peripheral nerve injury markedly regulates expression of neurotrophins and their receptors in the lesioned nerve. However, the role of endogenously produced neurotrophins in the process of nerve regeneration is unclear. Expression of a multifunctional neurotrophin, pan-neurotrophin-1 (PNT-1), was targeted to the peripheral nerves of transgenic mice by using a gene promoter that is specifically activated after nerve lesion but that is otherwise silent in all other tissues and during development. PNT-1 is a chimeric neurotrophin that combines the active sites of the neurotrophins nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 and binds and activates all known neurotrophin receptors. In adult transgenic mice, PNT-1 was highly expressed in transected but not in intact sciatic nerve. Morphometric analyses at the electron microscopy level showed increased and accelerated recovery of axon diameter of myelinated fibers in crushed peripheral nerves of transgenic mice compared with wild type. Examination of nerve bundles in target tissues indicated accelerated reinnervation of foot pad dermis and flexor plantaris muscle in transgenic mice. Moreover, transected sensory and motor axons of transgenic mice showed faster and increased return of neurophysiological responses, suggesting an accelerated rate of axonal elongation. Importantly, transgenic mice also showed a markedly ameliorated loss of skeletal muscle weight, indicating functional regeneration of motor axons. Together, these data provide evidence, at both the anatomical and functional levels, that neurotrophins endogenously produced by the lesioned nerve are capable of significantly accelerating the regeneration of both sensory and motor axons after peripheral nerve damage. In addition, our results indicate that exogenous PNT-1 administration may be an effective therapeutic treatment of peripheral nerve injuries.     

NF-κB-dependent regulation of brain-derived neurotrophic factor in hippocampal neurons by X-linked inhibitor of apoptosis protein

X chromosome-linked inhibitor of apoptosis protein (XIAP) is an anti-apoptotic protein enhancing cell survival. Brain-derived neurotrophic factor (BDNF) also promotes neuronal viability but the links between XIAP and BDNF have remained unclear. We show here that the overexpression of XIAP increases BDNF in transgenic mice and cultured rat hippocampal neurons, whereas downregulation of XIAP by silencing RNA decreased BDNF. XIAP also stimulated BDNF signaling, as shown by increased phosphorylation of the TrkB receptor and the downstream molecule, cAMP response element-binding protein. The mechanism involved nuclear factor-κB (NF-κB) activation and blocking of NF-κB signaling inhibited the increased activities of BDNF promoters I and IV by XIAP. In neuronal cultures XIAP also upregulated interleukin (IL)-6, which is an NF-κB-responsive gene. The addition of IL-6 elevated whereas incubation with IL-6-blocking antibodies reduced BDNF in the neurons. BDNF itself activated NF-κB in the neurons at higher concentrations. The data show that XIAP has trophic effects on hippocampal neurons by increasing BDNF and TrkB activity. The results reveal a cytokine network in the brain involving BDNF, IL-6 and XIAP interconnected via the NF-κB system.