Physiological properties of astroglial cell lines derived from mice with high (SAMP8) and low (SAMR1, ICR) levels of endogenous retrovirus

Previous studies have reported that various inbred SAM mouse strains differ markedly with regard to a variety of parameters, such as capacity for learning and memory, life spans and brain histopathology. A potential cause of differences seen in these strains may be based on the fact that some strains have a high concentration of infectious murine leukemia virus (MuLV) in the brain, whereas other strains have little or no virus. To elucidate the effect of a higher titer of endogenous retrovirus in astroglial cells of the brain, we established astroglial cell lines from SAMR1 and SAMP8 mice, which are, respectively, resistant and prone to deficit in learning and memory and shortened life span. MuLV-negative astroglial cell lines established from ICR mice served as controls. Comparison of these cell lines showed differences in: 1) levels of the capsid antigen CAgag in both cell lysates and culture media, 2) expression of genomic retroelements, 3) the number of virus particles, 4) titer of infectious virus, 5) morphology, 6) replication rate of cells in culture and final cell concentrations, 7) expression pattern of proinflammatory cytokine genes. The results show that the expression of MuLV is much higher in SAMP8 than SAMR1 astrocyte cultures and that there are physiological differences in astroglia from the 2 strains. These results raise the possibility that the distinct physiological differences between SAMP8 and SAMR1 are a function of activation of endogenous retrovirus

Copper chelation delays the onset of prion disease.

The prion protein (PrP) binds copper and under some conditions copper can facilitate its folding into a more protease resistant form. Hence, copper levels may influence the infectivity of the scrapie form of prion protein (PrP Sc ). To determine the feasibility of copper-targeted therapy for prion disease, we treated mice with a copper chelator, D-(؊)-penicillamine (D-PEN), starting immediately following intraperitoneal scrapie inoculation. D-PEN delayed the onset of prion disease in the mice by about 11 days (p ‫؍‬ 0.002), and reduced copper levels in brain by 29% (p < 0.01) and in blood by 22% (p ‫؍‬ 0.03) compared with control animals. Levels of other metals were not significantly altered in the blood or brain. Modest correlation was observed between incubation period and levels of copper in brain (p ‫؍‬ 0.08) or blood (p ‫؍‬ 0.04), indicating that copper levels are only one of many factors that influence the rate of progression of prion disease. In vitro, copper dose-dependently enhanced the proteinase K resistance of the prion protein, and this effect was counteracted in a dose-dependent manner by co-incubation with D-PEN. Overall, these findings indicate that copper levels can influence the conformational state of PrP, thereby enhancing its infectivity, and this effect can be attenuated by chelatorbased therapy

IgM and IgG Antibodies to Phenolic Glycolipid I from Mycobacterium leprae in Leprosy: Insight into Patient Monitoring, Erythema Nodosum Leprosum, and Bacillary Persistence

Serum IgM and IgG antibodies against Mycobacterium leprae-derived phenolic glycolipid I (PG) were determined in leprosy patients, contacts, and controls by enzyme-linked immunosorbent assay (ELISA). Anti-PG IgM levels increased from the tuberculoid (TT) to the lepromatous (LL) pole of the disease spectrum. There was a positive linear correlation between anti-PG IgM and bacillary index (BI). patients with erythema nodosum leprosum (ENL) had lower levels of serum anti-PG IgM than non-ENL patients of comparable BI, suggesting that anti-PG IgM is involved in the pathogenesis of ENL. Initial observations indicate that high anti-PG IgM levels in bacillary-negative patients might reflect bacillary persistence. A study of 2 different substrate reagents in the ELISA [2,2'-azino-di(3-ethyl-benzthiazoline-6-sulfonic acid) (ABTS), 0.1mM H2O2, serum diluted 1:20, and o-phenylenediamine (OPD), 5mM H2O2, serum diluted 1:300] showed generally good correlation in detection of anti-PG IgM. However the OPD system detected more paucibacillary disease (BT), while the ABTS system detected the significant effect of ENL on the relationship between BI and anti-PG IgM. Anti-PG IgM was clearly dominant over anti-PG IgG. However, certain patients, including several patients who had upgraded from LL and borderline lepromatous leprosy (BL), showed high levels of anti-PG IgG. Since studies have shown that LL patients are selectively deficient in cell-mediated immunity, T-cell products may be required for the IgM to IgG isotype switch. We conclude that anti-PG IgM is useful for monitoring the bacillary load in individual patients and should prove useful for leprosy control strategies

Infected splenic dendritic cells are sufficient for prion transmission to the CNS in mouse scrapie

Transmissible spongiform encephalopathies display long incubation periods at the beginning of which the titer of infectious agents (prions) increases in peripheral lymphoid organs. This “replication” leads to a progressive invasion of the CNS. Follicular dendritic cells appear to support prion replication in lymphoid follicles. However, the subsequent steps of neuroinvasion remain obscure. CD11c(+) dendritic cells, an unrelated cell type, are candidate vectors for prion propagation. We found a high infectivity titer in splenic dendritic cells from prion-infected mice, suggesting that dendritic cells carry infection. To test this hypothesis, we injected RAG-1(0/0) mice intravenously with live spleen cell subsets from scrapie-infected donors. Injection of infected dendritic cells induced scrapie without accumulation of prions in the spleen. These results suggest that CD11c(+) dendritic cells can propagate prions from the periphery to the CNS in the absence of any additional lymphoid element