Survival motor neuron protein deficiency alters microglia reactivity

Survival motor neuron (SMN) protein deficiency results in loss of alpha motor neurons and subsequent muscle atrophy in patients with spinal muscular atrophy (SMA). Reactive microglia have been reported in SMA mice and depleting microglia rescues the number of proprioceptive synapses, suggesting a role in SMA pathology. Here, we explore the contribution of lymphocytes on microglia reactivity in SMA mice and investigate how SMN deficiency alters the reactive profile of human induced pluripotent stem cell (iPSC)-derived microglia. We show that microglia adopt a reactive morphology in spinal cords of SMA mice. Ablating lymphocytes did not alter the reactive morphology of SMA microglia and did not improve the survival or motor function of SMA mice, indicating limited impact of peripheral immune cells on the SMA phenotype. We found iPSC-derived SMA microglia adopted an amoeboid morphology and displayed a reactive transcriptome profile, increased cell migration, and enhanced phagocytic activity. Importantly, cell morphology and electrophysiological properties of motor neurons were altered when they were incubated with conditioned media from SMA microglia. Together, these data reveal that SMN-deficient microglia adopt a reactive profile and exhibit an exaggerated inflammatory response with potential impact on SMA neuropathology.

Preliminary assessment of Treponema pallidum-specific IgM antibody detection and a new rapid point-of-care assay for the diagnosis of syphilis in human immunodeficiency virus-1-infected patients

The aims of the study were to assess whether Treponema pallidum-specific IgM may provide a useful marker of infectious syphilis in human immunodeficiency virus (HIV)-infected patients, and to compare the performance of a prototype IgM-rapid point-of-care test (PoCT) with a standard IgM-enzyme immunoassay (EIA). Twenty samples from HIV-infected patients with untreated syphilis (n = 4 primary syphilis, n = 11 secondary and n = 5 early latent) and 51 follow-up samples at three, six or 12 months after treatment were tested for the presence of IgM with the Mercia-EIA (Microgen Bioproducts Ltd, Camberley, UK) and a prototype PoCT (Select Vaccines Ltd, Melbourne, Australia). Although sample numbers were small, IgM detection by EIA appears to be a reliable marker for untreated syphilis in HIV-infected patients with primary (4/4 IgM-positive) or secondary syphilis (10/11 IgM-positive, 1/11 equivocal). After treatment, IgM was no longer detected after three months in the majority of patients (87%) and was either negative or equivocal in all patients after six and 12 months. The overall sensitivity of the IgM-PoCT was 82% and varied with clinical stage, being highest in secondary (10/10 EIA positives) but lower in primary (2/4 EIA positives) and early latent syphilis (2/3 EIA positives). Overall specificity was 95%. Rapid detection of IgM would enable clinicians to distinguish between past-treated and infectious syphilis and allow for diagnosis and treatment in a single visit.

Early transmission characteristics of influenza A(H1N1)v in Australia: Victorian state, 16 May - 3 June 2009

Australia was one of the first countries of the southern hemisphere to experience influenza A(H1N1)v with community transmission apparent in Victoria, Australia, by 22 May 2009. With few identified imported cases, the epidemic spread through schools and communities leading to 897 confirmed cases by 3 June 2009. The estimated reproduction ratio up to 31 May 2009 was 2.4 (95% credible interval (CI): 2.1-2.6). Methods designed to account for undetected transmission reduce this estimate to 1.6 (95% CI: 1.5-1.8). Time varying reproduction ratio estimates show a steady decline in observed transmission over the first 14 days of the epidemic. This could be accounted for by ascertainment bias or a true impact of interventions including antiviral prophylaxis, treatment and school closure. Most cases (78%) in the first 19 days in Victoria were under the age of 20 years-old. Estimates suggest that the average youth primary case infected at least two other youths in the early growth phase, which was sufficient to drive the epidemic.

Phosphorylation of p27Kip1 at Thr-157 interferes with its association with importin alpha during G1 and prevents nuclear re-entry

We have studied mechanisms of Akt-mediated phosphorylation and regulation of cellular localization of p27. Akt phosphorylates Thr-157 in p27 and retains it in the cytosol. In cells arrested in G(1) and then synchronized to enter into S phase, Akt-mediated phosphorylation of Thr-157 p27 occurred in the cytosol during G(1) phase of the cell cycle. Both T157A and S10A p27 mutants localized in the nucleus in all phases of the cell cycle regardless of the expression of active Akt. Thr-157 phosphorylation was undetectable in S10A-p27, suggesting that Ser-10 phosphorylation is required for p27 localization in the cytosol and subsequent phosphorylation at Thr-157. Phosphorylation at Thr-157 interrupted the association of p27 with importin alpha. A T157A-p27 mutant protein exhibited higher association with importin alpha than wild-type-p27. Treatment of transfected and endogenous p27 with alkaline phosphatase rescued its association with importin alpha. Leptomycin B inhibited cytosolic Thr-157 P-p27 staining, implying that CRM1-dependent nuclear export is required for Akt-mediated Thr-157 phosphorylation. Heterokaryon shuttling assays with NIH3T3 (mouse) cells transfected with FLAG-p27 and HeLa (human) cells revealed that both wild type and T157A-p27 shuttled from NIH3T3 to HeLa cell nuclei with similar frequencies. However, S10A-p27 was found only in the NIH3T3 nuclei of NIH3T3-HeLa cell fusions. These results suggest that 1) Ser-10 phosphorylation is required for nuclear export of p27, 2) subsequent Akt-mediated phosphorylation at Thr-157 during G(1) phase corrals p27 in the cytosol, and 3) Thr-157 phosphorylation inhibits the association of p27 with importin alpha thus preventing its re-entry into the nucleus.