Abstract Oral mucositis (OM) is a common debilitating dose-limiting toxicity of cancer treatment, including hematopoietic stem cell transplantation (HSCT). We hypothesized that the oral microbiome is disturbed during allogeneic HSCT, partially accounting for the variability in OM severity. Using 16S ribosomal RNA gene sequence analysis, metabolomic profiling, and computational methods, we characterized the behavior of the salivary microbiome and metabolome of 184 patients pre- and post-HSCT. Transplantation was associated with a decrease in oral α diversity in all patients. In contrast to the gut microbiome, an association with overall survival was not detected. Among 135 patients given methotrexate for graft-versus-host disease prophylaxis pre-HSCT, Kingella and Atopobium abundance correlated with future development of severe OM. Posttransplant, Methylobacterium species were significantly enriched in patients with severe OM. Moreover, the oral microbiome and metabolome of severe OM patients underwent distinct changes post-HSCT, compared with patients with no or mild OM. Changes in specific metabolites were well explained by microbial composition, and the common metabolic pathway was the polyamines pathway, which is essential for epithelial homeostasis. Together, our findings suggest that salivary microbial composition and metabolites are associated with the development of OM, offering new insights on pathophysiology and potential avenues of intervention.

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Following penetration of human immunodeficiency virus 1 (HIV-1) 3 into the host cell, reverse transcription of the viral RNA produces cDNA that is then integrated into the host chromosome (1). The integration of the viral cDNA is an essential early step in the HIV-1 life cycle. This reaction is catalyzed by the viral integrase (IN), a 32-kDa protein that is an integral part of the viral pre-integration complex (PIC) (2). The IN protein is encoded by the viral pol gene and is translated as part of a large Gag-Pol polyprotein that is processed by the viral protease (3, 4).For the integration process to occur, the viral IN must recognize specific sequences in the viral cDNA, at the termini of the long terminal repeat (LTR) elements. Retroviral integration proceeds in two steps: in the first, termed 3Ј-end processing, a dinucleotide is removed from the 3Ј-end. This reaction occurs in the cytoplasm, within the PIC (5, 6). In the next step, after entering the nucleus, the processed viral double-stranded DNA is joined to the host target DNA by an IN-mediated strandtransfer reaction.Due to its central role in HIV replication, the IN protein is an attractive target for antiviral therapy (4). Identifying specific IN inhibitors may provide a novel approach for multi-therapy strategies. Moreover, probably no cellular counterpart of IN exists in human cells and therefore, IN inhibitors should not interfere with normal cellular processes. However, only a few IN inhibitors have been described to date (4). This is in contrast to the number of inhibitors obtained against reverse transcriptase (RT) and the protease, which are the other HIV-1 enzymes that are currently used as targets for the development of anti-HIV-1 drugs (4). A promising approach for the discovery of IN inhibitors is the use of peptides derived from the IN-binding sequences of IN-interacting proteins.Specific domains within viral proteins are responsible for their interaction with host-cell receptors and with other viral and cellular proteins enabling the completion of the viral propagation cycle within the host cell (1, 6). Peptides derived from these binding domains may interfere with virus-host and virusvirus protein interactions and as such are excellent candidates as therapeutic agents. Using this approach, short peptides that inhibit IN enzymatic activity were obtained following analysis of the interaction between two of the HIV-1 proteins, RT and IN. Screening a complete library of RT-derived peptides demonstrated that two domains of about 20 amino acids mediate this interaction. Peptides bearing these amino acid sequences blocked IN enzymatic activities in vitro (7).In the present work, we observed a not yet described interaction between the HIV-1 Rev and IN proteins. The HIV-1 Rev is a karyophilic protein, which is required at the late phase of the viral life cycle for promoting nuclear export of partially spliced or un-spliced viral RNA (8, 9). Based on this finding, we identi-* This work was supported in part by grants from the Israel Science Foundat...

BackgroundThe integrase (IN) of human immunodeficiency virus type 1 (HIV-1) has been implicated in different steps during viral replication, including nuclear import of the viral pre-integration complex. The exact mechanisms underlying the nuclear import of IN and especially the question of whether it bears a functional nuclear localization signal (NLS) remain controversial.ResultsHere, we studied the nuclear import pathway of IN by using multiple in vivo and in vitro systems. Nuclear import was not observed in an importin α temperature-sensitive yeast mutant, indicating an importin α-mediated process. Direct interaction between the full-length IN and importin α was demonstrated in vivo using bimolecular fluorescence complementation assay (BiFC). Nuclear import studies in yeast cells, with permeabilized mammalian cells, or microinjected cultured mammalian cells strongly suggest that the IN bears a NLS domain located between residues 161 and 173. A peptide bearing this sequence -NLS-IN peptide- inhibited nuclear accumulation of IN in transfected cell-cycle arrested cells. Integration of viral cDNA as well as HIV-1 replication in viral cell-cycle arrested infected cells were blocked by the NLS-IN peptide.ConclusionOur present findings support the view that nuclear import of IN occurs via the importin α pathway and is promoted by a specific NLS domain. This import could be blocked by NLS-IN peptide, resulting in inhibition of viral infection, confirming the view that nuclear import of the viral pre-integration complex is mediated by viral IN.