Citations

ABSTRACT Dominant, constitutively expressed antiretroviral factors, including TRIM5α and APOBEC3 proteins, are distinguished from the conventional innate immune systems and are classified as intrinsic immunity factors. Here, we demonstrate that interferon alpha (IFN-α) treatment upregulates TRIM5α mRNA in rhesus monkey cells, which correlates with the enhanced TRIM5α-mediated pre- and postintegration blocks of human immunodeficiency virus replication. In human cells, IFN-α increases the levels of TRIM5α mRNA, resulting in enhanced antiviral activity against N-tropic murine leukemia virus infection. These observations indicate that the TRIM5α-mediated antiviral effects can be orchestrated by the conventional innate immune response. It is conceivable that TRIM5α plays an essential role in controlling both the initial retroviral exposure and the subsequent viral dissemination in vivo.

Abstract Purpose: Attenuated measles viruses are promising experimental anticancer agents currently being evaluated in a phase I dose escalation trial for ovarian cancer patients. Virus attachment, entry, and subsequent intercellular fusion between infected and uninfected neighboring cells are mediated via the two measles receptors (CD46 and SLAM). To minimize potential toxicity due to measles virus–associated immunosuppression and infection of nontarget tissues, we sought to develop an ovarian cancer exclusive fully retargeted measles virus. Experimental Design and Results: Interactions of measles virus with its natural receptors were ablated, and a single-chain antibody (scFv) specific for α-folate receptor (FRα), a target overexpressed on 90% of nonmucinous ovarian cancer, was genetically engineered on the viral attachment protein (MV-αFR). Specificity of virus tropism was tested on tumor and normal cells. Biodistribution of measles virus infection was evaluated in measles-susceptible CD46 transgenic mice, whereas antitumor activity was monitored noninvasively by bioluminescence imaging in xenograft models. Tropism and fusogenic activity of MV-αFR was redirected exclusively to FRα without compromise to virus infectivity. In contrast to the parental virus, MV-αFR has no background infectivity on normal human cells. The antitumor activity of MV-αFR, as assessed by tumor volume reduction and overall survival increase, was equal to the parental virus in two models of human ovarian cancer (s.c. and i.p.). Conclusions: A FR-exclusive ovarian cancer targeted oncolytic virus was generated and shown to be therapeutically effective, thus introducing a new modality for FR targeting and a candidate measles virus for clinical testing.

ABSTRACT Murine primary cells are poorly permissive to human immunodeficiency virus type 1 (HIV-1) vector infection. Retroviral infectivity is influenced by dominant inhibitors such as TRIM5α. Sensitivity to TRIM5α is altered by interactions between cyclophilin A and the HIV-1 capsid. Here we demonstrate that competitive inhibitors of cyclophilins, cyclosporine or the related Debio-025, stimulate HIV-1 vector transduction of primary murine cells, including bone marrow and macrophages, up to 20-fold. Unexpectedly, the infectivity of an HIV-1 mutant or a simian lentivirus that does not recruit cyclophilin A is also stimulated by these drugs. We propose that cyclosporine and related compounds will be useful tools for experimental infection of murine primary cells. It is possible that HIV-1 infection of murine cells is inhibited by dominant factors related to immunophilins.

Prooxidents can induce reversible inhibition or irreversible inactivation and degradation of the mitochondrial enzyme aconitase. Cardiac ischemia/reperfusion is associated with an increase in mitochondrial free radical production. In the current study, the effects of reperfusion-induced production of prooxidants on mitochondrial aconitase and proteolytic activity were determined to assess whether alterations represented a regulated response to changes in redox status or oxidative damage. Evidence is provided that ATP-dependent proteolytic activity increased during early reperfusion followed by a time-dependent reduction in activity to control levels. These alterations in proteolytic activity paralleled an increase and subsequent decrease in the level of oxidatively modified protein. In vitro data supports a role for prooxidants in the activation of ATP-dependent proteolytic activity. Despite inhibition during early periods of reperfusion, aconitase was not degraded under the conditions of these experiments. Aconitase activity exhibited a decline in activity followed by reactivation during cardiac reperfusion. Loss and regain in activity involved reversible sulfhydryl modification. Aconitase was found to associate with the iron binding protein frataxin exclusively during reperfusion. In vitro , frataxin has been shown to protect aconitase from [4Fe-4S] 2+ cluster disassembly, irreversible inactivation, and, potentially, degradation. Thus, the response of mitochondrial aconitase and ATP-dependent proteolytic activity to reperfusion-induced prooxidant production appears to be a regulated event that would be expected to reduce irreparable damage to the mitochondria.

Numerous degenerative disorders are associated with elevated levels of prooxidants and declines in mitochondrial aconitase activity. Deficiency in the mitochondrial iron-binding protein frataxin results in diminished activity of various mitochondrial iron-sulfur proteins including aconitase. We found that aconitase can undergo reversible citrate-dependent modulation in activity in response to pro-oxidants. Frataxin interacted with aconitase in a citrate-dependent fashion, reduced the level of oxidant-induced inactivation, and converted inactive [3Fe-4S] 1+ enzyme to the active [4Fe-4S] 2+ form of the protein. Thus, frataxin is an iron chaperone protein that protects the aconitase [4Fe-4S] 2+ cluster from disassembly and promotes enzyme reactivation.