Early life malnutrition and fluctuating asymmetry in the rat bony labyrinth.

Maternal malnutrition during gestation and lactation is known to have adverse effects on offspring. We evaluate the impact of maternal diet on offspring bony labyrinth morphology. The bony labyrinth develops early and is thought to be stable to protect vital sensory organs within. For these reasons, bony labyrinth morphology has been used extensively to assess locomotion, hearing function, and phylogeny in primates and numerous other taxa. While variation related to these parameters has been documented, there is still a component of intraspecific variation that is unexplained. Although the labyrinthine developmental window is small, it may provide the opportunity for developmental instability to produce corresponding shape differences, as measured by fluctuating asymmetry (FA). We hypothesized that (a) offspring with poor maternal diet would exhibit increased FA, but (b) no unilateral shape difference. To test these hypotheses, we used two groups of rats (Rattus norvegicus; Crl:WI[Han] strain), one control group and one group exposed to a isocaloric, protein-restricted maternal diet during gestation and suckling. Individuals were sampled at weaning, sexual maturity, and old age. A Procrustes analysis of variance identified statistically significant FA in all diet-age subgroups. No differences in level of FA were identified among the subgroups, rejecting our first hypothesis. A principal components analysis identified no unilateral shape differences, supporting our second hypothesis. These results indicate that bony labyrinth morphology is remarkably stable and likely protected from a poor maternal diet during development. In light of this result, other factors must be explored to explain intraspecific variation in labyrinthine shape.

Human immunodeficiency virus type 1-associated CD40 ligand transactivates B lymphocytes and promotes infection of CD4+ T cells.

Abnormal activation of B lymphocytes is a feature commonly seen in human immunodeficiency virus type 1 (HIV-1)-infected persons. However, the mechanism(s) responsible for this dysfunction is still poorly understood. Having recently shown that CD40L, the ligand for CD40, is inserted within emerging HIV-1 particles, we hypothesized that the contact between virus-anchored host CD40L and CD40 on the surface of B lymphocytes might result in the activation of this cell type. We report here that CD40L-bearing viruses, but not isogenic virions lacking host-derived CD40L, can induce immunoglobulin G and interleukin-6 production. Furthermore, such viral entities were found to induce B-cell homotypic adhesion. These effects were paralleled at the intracellular level by the nuclear translocation of the ubiquitous transcription factor NF-kappaB. The presence of host-derived CD40L within virions resulted in an increased virus attachment to B cells and a more-efficient B-cell-mediated transfer of HIV-1 to autologous CD4(+) T lymphocytes. All the above processes were independent of the virus-encoded envelope glycoproteins. Altogether, the data gathered from this series of investigations suggest that the incorporation of host-encoded CD40L in HIV-1 is likely to play a role in the B-cell abnormalities that are seen in infected individuals.

HIV type 1 can act as an APC upon acquisition from the host cell of peptide-loaded HLA-DR and CD86 molecules.

It is well documented that a wide range of host-derived cell surface constituents is inserted within HIV type 1 (HIV-1) and located on the exterior of the virion. Although no virus-associated protein of host origin has been shown to be absolutely required for virus replication, studies have revealed that many of these proteins are functional and can affect several steps of the virus life cycle. In this study, we found that HIV-1 acquires peptide-loaded class II MHC (MHC-II) and the costimulatory CD86 molecules from the host cell. Moreover, we present evidence that virions bearing such peptide-loaded MHC-II and CD86 proteins can lead to activation of the transcription factors NF-kappa B and NF-AT in an Ag-specific human T cell line. A linear correlation was found between activation of NF-kappa B and the amount of peptide-loaded MHC-II molecules inserted within HIV-1. Finally, transcription of unintegrated and integrated HIV-1 DNA was promoted upon exposure of peptide-specific human T cells to viruses bearing both peptide-loaded MHC-II and CD86 proteins. These data suggest that HIV-1 can operate as an APC depending on the nature of virus-anchored host cell membrane components. It can be proposed that HIV-1 can manipulate one of its primary targets through the process of incorporation of host-derived proteins.

Galectin-1 acts as a soluble host factor that promotes HIV-1 infectivity through stabilization of virus attachment to host cells.

The establishment of HIV type 1 (HIV-1) infection is initiated by the stable attachment of the virion to the target cell surface. Although this process relies primarily upon interaction between virus-encoded gp120 and cell surface CD4, a number of distinct interactions influence binding of HIV-1 to host cells. In this study, we report that galectin-1, a dimeric beta-galactoside-binding protein, promotes infection with R5, X4, and R5X4 variants. Galectin-1 acts as a soluble adhesion molecule by facilitating attachment of HIV-1 to the cell surface. This postulate is based on experiments where galectin-1 rendered HIV-1 particles more refractory to various agents that block HIV-1 adsorption and coreceptor binding (i.e., a blocking anti-CD4, soluble CD4, human anti-HIV-1 polyclonal Abs; stromal cell-derived factor-1alpha; RANTES). Experiments performed with the fusion inhibitor T-20 confirmed that galectin-1 is primarily affecting HIV-1 attachment. The relevance of the present findings for the pathogenesis of HIV-1 infection is provided by the fact that galectin-1 is abundantly expressed in the thymus and lymph nodes, organs that represent major reservoirs for HIV-1. Moreover, galectin-1 is secreted by activated CD8(+) T lymphocytes, which are found in high numbers in HIV-1-positive patients. Therefore, it is proposed that galectin-1, which is released in an exocrine fashion at HIV-1 replication sites, can cross-link HIV-1 and target cells and promote a firmer adhesion of the virus to the cell surface, thereby augmenting the efficiency of the infection process. Overall, our findings suggest that galectin-1 might affect the pathogenesis of HIV-1 infection.

Activation of HTLV-I gene transcription by protein tyrosine phosphatase inhibitors.

Human T-cell leukemia virus type I (HTLV-I) transcription generally depends on the ability of the viral Tax protein to bind the CREB transcription factor and form an active complex by recruiting CBP/p300 coactivators to the long terminal repeat (LTR). Studies have demonstrated that T-cell activating agents that stimulate CREB are potent inducers of HTLV-I transcription. Herein, we demonstrate that bpV[pic], a protein tyrosine phosphatase (PTP) inhibitor activates the HTLV-I LTR in the presence and absence of Tax expression. Optimal activation occurred at 8 h and was synergistic with forskolin or PGE(2). Infected cell lines and cells transfected with HTLV-I proviral DNA were equally responsive to the synergistic effect of bpV and forskolin on HTLV-I gene expression. Activation of the LTR by bpV[pic] was T-cell receptor-independent, but required ZAP70, calcineurin activity and functional calcium entry. Inhibition of the SHP-1 PTP was suggested to be important. Transfection experiments with a CREB dominant-negative mutant and with isolated TRE1- or CREB-responsive reporter constructs and treatment with the MDL-12,330A adenylate cyclase inhibitor all supported the involvement of a CREB/ATF family member in this bpV-dependent activation of the HTLV-I LTR, although CREB itself did not seem to be involved. Analysis of HTLV-I reporter constructs containing mutated CREB-binding sites also implied the involvement of another element in this activation. These results demonstrate for the first time a powerful effect of PTP inhibitors on HTLV-I LTR activity and suggest participation of both CREB-dependent and -independent pathways in this activation.

NF-kappaB induction by bisperoxovanadium compounds requires CD45, p36(LAT), PKC, and IKK activity and exhibits kinetics of activation comparable to those of TCR/CD28 coengagement.

We have previously shown that bisperoxovanadium (bpV) phosphotyrosyl phosphatase inhibitors can potently activate NF-kappaB. We have already determined that p56(lck), ZAP-70, SLP-76, capacitative entry of calcium, and calcium-regulated effectors are important in bpV-induced NF-kappaB activation. In this study, we evaluated whether other signal transducers previously reported in NF-kappaB induction by T cell activating stimuli are also activated by bpV compounds. Nuclear translocation of NF-kappaB was evaluated in cell lines deficient for either CD45 or p36(LAT) to assess the role of these signal transducers in bpV-mediated NF-kappaB activation. A deficiency of either protein greatly reduced the extent of NF-kappaB nuclear translocation following bpV treatment. Isoform-specific PKC inhibitors were then used to show that bpV compounds activate NF-kappaB through both calcium-sensitive and -insensitive PKC isoforms. The implication of the IkappaB-kinase complex was then investigated through the use of an IkappaBalpha-specific kinase assay and plasmids expressing catalytically inactive forms of IKKalpha and IKKbeta. Upstream kinases involved in IKK complex activation such as TPL-2/COT, NIK, and IKKepsilon were also shown to play an important role in bpV-mediated NF-kappaB activation. Finally, reporter gene transcriptional assays and gel shift assays were performed to compare the kinetics of activation of NF-kappaB by bpV with those of antigenic and TNFalpha stimulation. We demonstrate, both in Jurkat cells and in primary T cells, that bpV-mediated NF-kappaB activation kinetics are comparable to those of an antigenic stimulation but occur much slower than the kinetics seen upon TNFalpha treatment.

The immunosuppressant rapamycin represses human immunodeficiency virus type 1 replication.

The immunosuppressive macrolide rapamycin is used in humans to prevent graft rejection. This drug acts by selectively repressing the translation of proteins that are encoded by an mRNA bearing a 5'-polypyrimidine tract (e.g., ribosomal proteins, elongation factors). The human immunodeficiency virus type 1 (HIV-1) carries a polypyrimidine motif that is located within the tat exon 2. Treatment of human T lymphoid cells with rapamycin resulted in a marked diminution of HIV-1 transcription when infection was performed with luciferase reporter T-tropic and macrophage-tropic viruses. Replication of fully infectious HIV-1 particles was abolished by rapamycin treatment. The rapamycin-mediated inhibitory effect on HIV-1 production was reversed by FK506. The anti-HIV-1 effect of rapamycin was also seen in primary human cells (i.e., peripheral blood lymphocytes) from different healthy donors. Rapamycin was shown to diminish basal HIV-1 long terminal repeat gene expression, and the observed effect of rapamycin on HIV-1 replication seems to be independent of the virus-specific transactivating Tat protein. A constitutive beta-actin promoter-based reporter gene vector was unaffected by rapamycin treatment. Kinetic virus infection studies and exposure to reporter viruses pseudotyped with heterologous envelope proteins (i.e., amphotropic murine leukemia virus and vesicular stomatitis virus G) suggested that rapamycin is primarily affecting the life cycle of HIV-1 at a transcriptional level. Northern blot analysis confirmed that this compound is selectively targeting HIV-1 mRNA synthesis.

HIV-1 transcription and virus production are both accentuated by the proinflammatory myeloid-related proteins in human CD4+ T lymphocytes.

S100A8, S100A9, and S100A12, collectively known as myeloid-related proteins (MRPs), are highly expressed by the myeloid cell lineage and are found in the extracellular milieu during infections and inflammatory conditions. Recent data showed high levels of MRPs in the serum of HIV type 1 (HIV-1)-infected patients which correlated with disease progression and low CD4(+) counts. Therefore, we set out to investigate the effect of MRPs on HIV-1 replication. We observed a 4- to 5-fold induction of virus production in J1.1, a human T lymphoid cell line latently infected with HIV-1, following treatment with MRPs. Using luciferase-based reporter gene assays, we demonstrated that MRPs induce a dose- and time-dependent activation of the HIV-1 long terminal repeat promoter region that could be blocked by specific anti-MRP polyclonal Abs and by physical denaturation of these proteins. The MRP-mediated induction was acting through the HIV-1 enhancer sequence and was dependent upon NF-kappaB activity. These latter results were also confirmed by EMSA experiments conducted in Jurkat cells and freshly isolated PBMCs. In conclusion, we demonstrate that MRPs induce HIV-1 transcriptional activity and viral replication in infected CD4(+) T-lymphocytes at concentrations similar to those found in the serum of HIV-1-infected patients.