An HIV-1 replication pathway utilizing reverse transcription products that fail to integrate.

Integration is a central event in the replication of retroviruses, yet ≥ 90% of HIV-1 reverse transcripts fail to integrate, resulting in accumulation of unintegrated viral DNA in cells. However, understanding what role, if any, unintegrated viral DNA plays in the natural history of HIV-1 has remained elusive. Unintegrated HIV-1 DNA is reported to possess a limited capacity for gene expression restricted to early gene products and is considered a replicative dead end. Although the majority of peripheral blood CD4(+) T cells are refractory to infection, nonactivated CD4 T cells present in lymphoid and mucosal tissues are major targets for infection. Treatment with cytokine interleukin-2 (IL-2), IL-4, IL-7, or IL-15 renders CD4(+) T cells permissive to HIV-1 infection in the absence of cell activation and proliferation and provides a useful model for infection of resting CD4(+) T cells. We found that infection of cytokine-treated resting CD4(+) T cells in the presence of raltegravir or with integrase active-site mutant HIV-1 yielded de novo virus production following subsequent T cell activation. Infection with integration-competent HIV-1 naturally generated a population of cells generating virus from unintegrated DNA. Latent infection persisted for several weeks and could be activated to virus production by a combination of a histone deacetylase inhibitor and a protein kinase C activator or by T cell activation. HIV-1 Vpr was essential for unintegrated HIV-1 gene expression and de novo virus production in this system. Bypassing integration by this mechanism may allow the preservation of genetic information that otherwise would be lost.

Isolation and identification of a bacteriocin with antibacterial and antibiofilm activity from Citrobacter freundii.

Multi- and pan-antibiotic-resistant bacteria area major health challenge in hospital settings. Furthermore,when susceptible bacteria establish surface-attached biofilm populations, they become recalcitrant to antimicrobial therapy. Therefore, there is a need for novel antimicrobials that are effective against multi-drug-resistant and surface-attached bacteria. A screen to identify prokaryote-derived antimicrobials from a panel of over 100 bacterial strains was performed. One compound isolated from Citrobacter freundii exhibited antimicrobial activity against a wide range of Gram-negative bacteria and was effective against biofilms. Random transposon mutagenesis was performed to find mutants unable to produce the antimicrobial compound.Transposons mapped to a bacteriocin gene located on a small plasmid capable of replication in Escherichia coli. The plasmid was sequenced and found to be highly similar to a previously described colicinogenic plasmid.Expression of the predicted bacteriocin immunity gene conferred bacteriocin immunity to E. coli. The predicted bacteriocin gene, colA-43864, expressed in E. coli was sufficient to generate anti-microbial activity, and purified recombinant ColA-43864 was highly effective in killing E. coli, Citrobacter species, and Klebsiella pneumoniae cells in a planktonic and biofilm state. This study suggests that bacteriocins can be an effective way to control surface-attached pathogenic bacteria.

Sensory discrimination of teeth and implant-supported restorations.

PURPOSE: The purpose of this study was to examine patient responses to load application on natural teeth and implants using a visual analog scale (VAS). MATERIALS AND METHODS: Ten subjects were selected from the University of Medicine and Dentistry of New Jersey patient pool who had a single implant-supported crown restoration adjacent to a natural tooth. Vibrational loads of 0.2 N, 0.4 N, and 0.6 N were applied to the tooth and implant-supported crown. The VAS was used to measure the magnitude of sensation. Patient responses were recorded in sets of five alternating paired trials and analyzed for differences in the responses to teeth and implant-supported crowns. RESULTS: Patients were able to discriminate between loads to implants and natural teeth 100% of the time (P = or < .01). The responses to loading of the implant were less strong than those to loading of the natural tooth 100% of the time (P = or < .01). However, the VAS score ratios between implant and natural tooth consistently increased with an increase in load. CONCLUSION: Although periodontal ligament receptors are lacking in the peri-implant area, patients appear to have some proprioceptive awareness of implant loading. This awareness becomes more similar to that of natural teeth as the vibrational load is increased.