Type I IFN induces vascular permeability delivering iron binding proteins to the site of Cryptococcosis gattii infection resulting in local nutritional immunity and contained infection

While Cryptococcus neoformans primarily infect AIDS patients, Cryptococcus gattii (Cg) causes deadly mycosis in mostly non-HIV patients even in Cg endemic areas with high rates of AIDS. Previous work found that type I IFN (t1IFN), which is induced by HIV infection, protects mice from Cg. Thus, we sought to examine the mechanisms mediating t1IFN protection from Cg. Previous data ruled out cellular immunity, so we examined soluble immune factors. We found that induction of t1IFN by stabilized poly(I:C) (pICLC) induced the expression of serum proteins into the lung airspace fluids. PICLC induced the leak of intravenously injected FITC-dextran into lung airspace fluids suggesting that serum proteins reach the lung airspace via t1IFN-induced vascular permeability. The pICLC-mediated expression of serum proteins into the lung airspace was dependent on t1IFN but not IL-6, IL-1 or TNF-α indicating that this effect is mediated by t1IFN and not by other cytokines characterized to affect vascular permeability. Transferrin and ferritin were among the leaked serum proteins found in the lung airspace and were directly inhibitory to cryptococcus in vitro so we hypothesized that the presence of these proteins in the lung airspace may result in local iron deficiency. Iron supplementation reversed pICLC-protection while iron chelation mediated similar protection as pICLC. Together these data suggest that t1IFN induces vascular permeability in the lung which delivers iron binding proteins to the Cg niche. These host proteins restrict iron to Cg and limit infection. In addition to explaining the pICLC-induced protection from Cg, these studies illustrate a novel connection between t1IFN and vascular permeability that may be significant to other systems.

Regions of mouse chromosomes 2 and 11 in SJL mice contain critical alleles for resistance to Cryptococcus neoformans

Cryptococcus neoformans (Cn) remains a leading cause of deadly mycosis. While previous studies have elucidated some of the host immune processes, little is known about the fundamental host factors that determine the outcome of Cn infection. Unfortunately, all commonly used inbred mice (including the common C57BL/6) are highly susceptible to virulent Cn strains, whereas humans are resistant to Cn unless immunocompromised. Thus, we sought a murine Cn infection system that more closely models humans. Testing the susceptibility of about 20 inbred strains of mice, we found that the SJL strain is, by far, the most Cn resistant inbred mouse strain in contrast to the closely related FVB strain being completely susceptible. While the early stages of Cn infection seem similar, SJL mice eventually cleared Cn and resolved pulmonary pathology, with little CNS dissemination. In contrast, susceptible mice showed significant and increasing fungal loads in both lungs and brains with associated pathology and death. F1 mice from FVB × SJL crosses were highly resistant to Cn suggesting that the resistant phenotype is dominant. Twenty percent of N2 mice (FVB × SJL F1 mice backcrossed to FVB) survived infection suggesting the involvement of multiple loci. Gene mapping uncovered two areas of genetic linkage to Cn resistance. These areas of interest were in portions of chromosomes 2 and 11. Genomic analysis found several candidate genes which are currently under evaluation. Mapping these cryptococcal resistance gene alleles may illuminate pathways of natural resistance which could be utilized for improved therapeutic options or to identify human populations at risk for cryptococcosis, making SJL mice an important tool for understanding cryptococcosis.

Anxiogenic effects in the rat elevated plus-maze of 5-HT(2C) agonists into ventral but not dorsal hippocampus

The effect of the non-selective 5-HT2C receptor agonist trifluoromethyl-phenylpiperazine (TFMPP, 0.75, 1.5 and 3.0 microg) and the preferential 5-HT2C agonist 6-chloro-2(1-piperazinyl)pyrazine (MK-212, 0.1, 0.3 and 1.0 microg) microinjected into the ventral or dorsal hippocampus was investigated in anxiety measures of rats exposed to the elevated plus-maze test. Ventral hippocampal (VH) microinjections of the 0.75 or 1.5 microg doses of TFMPP reduced open-arm exploration without affecting the number of closed-arm entries, indicating a selective anxiogenic profile. The highest dose (3.0 microg) reduced open- and closed-arm entries, suggesting interference in locomotor activity. The 0.1 microg dose of MK-212 also caused a selective anxiogenic effect when microinjected into the ventral hippocampus, without disturbing locomotor activity. Microinjections of the two higher doses of MK-212 (0.3 or 1.0 microg) into the ventral hippocampus led to a decrease of exploration in both arms of the maze. In contrast to the anxiogenic effect observed in the VH, neither TFMPP nor MK-212 significantly changed anxiety measures when microinjected into the dorsal hippocampus. These results suggest that activation of 5-HT2C postsynaptic receptors located in the ventral, but not in the dorsal, hippocampus play an important role in anxiety triggered by the elevated plus-maze test.