Human embryonic stem cell-derived oligodendrocyte progenitor cells express the serotonin receptor and are susceptible to JC virus infection.

We studied the susceptibility of human embryonic stem cell-derived oligodendrocyte progenitor cells to infection with JC virus, the causative agent of progressive multifocal leukoencephalopathy (PML). A human embryonic stem cell line, H7, was used to derive an enriched population of cells expressing the oligodendrocyte progenitor cell-specific marker NG2. These cells expressed the 5HT2a receptor (5HT2aR) for JC virus and were highly susceptible to infection. Infection was reduced by treatment with anti-5HT2aR antibodies and by the 5HT2aR antagonists ritanserin and ketanserin. This is the first demonstration that human embryonic stem cell-derived oligodendrocyte progenitor cells are susceptible to JC virus infection and indicates that cells poised to replenish mature oligodendrocytes in PML lesions may also be a target of viral infection.

Interferon beta1-a and selective anti-5HT(2a) receptor antagonists inhibit infection of human glial cells by JC virus.

JC virus (JCV) is the causative agent of progressive multifocal leukoenchaphalopathy (PML). The disease develops when JCV gains access to the central nervous system, infects and destroys oligodendrocytes. The disease is rapidly progressing, typically fatal and no effective therapies exist to treat or prevent PML. The recent occurrence of PML in multiple sclerosis patients being treated with Avonex (IFNbeta1-a) and Tysabri (Natalizumab) and the recent reports linking JCV infection to the 5HT(2a) serotonin receptor led us to evaluate the effects of IFNbeta1-a and a panel of 5HT(2a) receptor antagonists for their ability to modulate virus infection. IFNbeta1-a was found to be a potent inhibitor of both virus infection and viral early and late gene expression. In addition, several 5HT(2a) receptor antagonists inhibited initial infection of cells by JCV but were less effective at reducing viral loads in an already established infection.

Invasion of host cells by JC virus identifies a novel role for caveolae in endosomal sorting of noncaveolar ligands.

Invasion of glial cells by the human polyomavirus, JC virus (JCV), leads to a rapidly progressing and uniformly fatal demyelinating disease known as progressive multifocal leukoencephalopathy. The endocytic trafficking steps used by JCV to invade cells and initiate infection are not known. We demonstrated that JCV infection was inhibited by dominant defective and constitutively active Rab5-GTPase mutants that acted at distinct steps in endosomal sorting. We also found that labeled JCV colocalized with labeled cholera toxin B and with caveolin-1 (cav-1) on early endosomes following internalization by clathrin-dependent endocytosis. JCV entry and infection were both inhibited by dominant defective mutants of eps15 and Rab5-GTPase. Expression of a dominant-negative scaffolding mutant of cav-1 did not inhibit entry or infection by JCV. A single-cell knockdown experiment using cav-1 shRNA did not inhibit JCV entry but interfered with a downstream trafficking event important for infection. These data show that JCV enters cells by clathrin-dependent endocytosis, is transported immediately to early endosomes, and is then sorted to a caveolin-1-positive endosomal compartment. This latter step is dependent on Rab5-GTPase, cholesterol, caveolin-1, and pH. This is the first example of a ligand that enters cells by clathrin-dependent endocytosis and is then sorted from early endosomes to caveosomes, indicating that caveolae-derived vesicles play a more important role than previously realized in sorting cargo from early endosomes.

Inter-brand differences in iron content of breakfast cereals and their impact on measurement of iron intake.

BACKGROUND/AIMS: Fortified breakfast cereals (FBCs) are an important source of iron in the UK diet. In order to quantify their contribution to iron nutrition, food composition data for these products must be accurate. The very large amount of products available, together with inter-brand differences in iron content mean that discrepancies between the iron content of many FBCs and values in standard food composition databases (FCD) exist. The variation in reported iron contents of FBCs was examined and the impact of this variation on measurement of iron intake using standard food composition tables was investigated. METHOD: Data on the reported iron content of 128 FBCs were collected. Completed food diaries from 291 participants of the UK Women's Cohort study were used in the analysis. Mean iron intake from a 4-day food diary was calculated using UK food tables' values for FBCs. This was repeated using values reported by the manufacturer for each brand of cereal. The two sets of results were then compared. RESULTS: There is wide variation in iron content of breakfast cereals available in the United Kingdom. Use of FCD values instead of brand-specific values under- or overestimates an individual's iron intake by as much as 28 or 22% respectively. These results suggest that use of FCD values for breakfast cereals is potentially a source of substantial error in measurement of individuals' iron intake. CONCLUSION: Dietitians need to be aware of inter-brand differences in iron content and formulate advice accordingly. Failure to collect brand-specific data for the iron content of FBCs could lead to measurement error in measuring iron intake in dietary studies.