The Role of Natural Antibodies to CC Chemokine Receptor 5 in HIV Infection

The CC chemokine receptor 5 (CCR5) is responsible for immune and inflammatory responses by mediation of chemotactic activity in leukocytes, although it is expressed on different cell types. It has been shown to act as co-receptor for the human and simian immunodeficiency viruses (HIV-1, HIV-2, and SIV). Natural reactive antibodies (Abs) recognizing first loop (ECL1) of CCR5 have been detected in several pools of immunoglobulins from healthy donors and from several cohorts of either HIV-exposed but uninfected subjects (ESN) or HIV-infected individuals who control disease progression (LTNP) as well. The reason of development of anti-CCR5 Abs in the absence of autoimmune disease is still unknown; however, the presence of these Abs specific for CCR5 or for other immune receptors and mediators probably is related to homeostasis maintenance. The majority of anti-CCR5 Abs is directed to HIV binding site (N-terminus and ECL2) of the receptor. Conversely, it is well known that ECL1 of CCR5 does not bind HIV; thus, the anti-CCR5 Abs directed to ECL1 elicit a long-lasting internalization of CCR5 but not interfere with HIV binding directly; these Abs block HIV infection in either epithelial cells or CD4+ T lymphocytes and the mechanism differs from those ones described for all other CCR5-specific ligands. The Ab-mediated CCR5 internalization allows the formation of a stable signalosome by interaction of CCR5, β-arrestin2 and ERK1 proteins. The signalosome degradation and the subsequent de novo proteins synthesis determine the CCR5 reappearance on the cell membrane with a very long-lasting kinetics (8 days). The use of monoclonal Abs to CCR5 with particular characteristics and mode of action may represent a novel mode to fight viral infection in either vaccinal or therapeutic strategies

Early activation of MyD88-mediated autophagy sustains HSV-1 replication in human monocytic THP-1 cells

Autophagy is a cellular degradation pathway that exerts numerous functions in vital biological processes. Among these, it contributes to both innate and adaptive immunity. On the other hand, pathogens have evolved strategies to manipulate autophagy for their own advantage. By monitoring autophagic markers, we showed that HSV-1 transiently induced autophagosome formation during early times of the infection of monocytic THP-1 cells and human monocytes. Autophagy is induced in THP-1 cells by a mechanism independent of viral gene expression or viral DNA accumulation. We found that the MyD88 signaling pathway is required for HSV-1-mediated autophagy, and it is linked to the toll-like receptor 2 (TLR2). Interestingly, autophagy inhibition by pharmacological modulators or siRNA knockdown impaired viral replication in both THP-1 cells and human monocytes, suggest that the virus exploits the autophagic machinery to its own benefit in these cells. Taken together, these findings indicate that the early autophagic response induced by HSV-1 exerts a proviral role, improving viral production in a semi-permissive model such as THP-1 cells and human monocytes

UV Radiation Activates Toll-Like Receptor 9 Expression in Primary Human Keratinocytes, an Event Inhibited by Human Papillomavirus 38 E6 and E7 Oncoproteins

International audienceSeveral lines of evidence indicate that cutaneous human papillomavirus (HPV) types belonging to the beta genus of the HPV phylogenetic tree synergize with UV radiation in the development of skin cancer. Accordingly, the E6 and E7 oncoproteins from some beta HPV types are able to deregulate pathways related to immune response and cellular transformation. Toll-like receptor 9 (TLR9), in addition to playing a role in innate immunity, has been shown to be involved in the cellular stress response. Using primary human keratinocytes as experimental models, we have shown that UV irradiation (and other cellular stresses) activates TLR9 expression. This event is closely linked to p53 activation. Silencing the expression of p53 or deleting its encoding gene affected the activation of TLR9 expression after UV irradiation. Using various strategies, we have also shown that the transcription factors p53 and c-Jun are recruited onto a specific region of the TLR9 promoter after UV irradiation. Importantly, the E6 and E7 oncoproteins from beta HPV38, by inducing the accumulation of the p53 antagonist ΔNp73α, prevent the UV-mediated recruitment of these transcription factors onto the TLR9 promoter, with subsequent impairment of TLR9 gene expression. This study provides new insight into the mechanism that mediates TLR9 upregulation in response to cellular stresses. In addition, we show that HPV38 E6 and E7 are able to interfere with this mechanism, providing another explanation for the possible cooperation of beta HPV types with UV radiation in skin carcinogenesis.IMPORTANCE Beta HPV types have been suggested to act as cofactors in UV-induced skin carcinogenesis by altering several cellular mechanisms activated by UV radiation. We show that the expression of TLR9, a sensor of damage-associated molecular patterns produced during cellular stress, is activated by UV radiation in primary human keratinocytes (PHKs). Two transcription factors known to be activated by UV radiation, p53 and c-Jun, play key roles in UV-activated TLR9 expression. The E6 and E7 oncoproteins from beta HPV38 strongly inhibit UV-activated TLR9 expression by preventing the recruitment of p53 and c-Jun to the TLR9 promoter. Our findings provide additional support for the role that beta HPV types play in skin carcinogenesis by preventing activation of specific pathways upon exposure of PHKs to UV radiation

The Abrogation of Phosphorylation Plays a Relevant Role in the CCR5 Signalosome Formation with Natural Antibodies to CCR5

The exposure to CCR5 (CC chemokine receptor 5) specific natural antibodies in vitro produces a Class B β-arrestin2-dependent CCR5 retention with the aid of ERK1, due to the formation of a CCR5 signalosome, which remains stable for at least 48 h. Considering that β-arrestins and MAPKs are receptive to environmental signals, their signal complexes could be one of the key junction for GPCRs internalization related signal transduction. Here, we demonstrate that, in T cells, the phosphorylation status of either CCR5 receptor or ERK1 protein is necessary to drive the internalized receptor into the early endosomes, forming the CCR5 signalosome. In particular, our data show that β-arrestin2/ERK1 complex is a relevant transducer in the CCR5 signaling pathway. Understanding the mechanism of CCR5 regulation is essential for many inflammatory disorders, tumorigenesis and viral infection such as HIV

Wilms' tumor gene 1 (WT1) silencing inhibits proliferation of malignant peripheral nerve sheath tumor sNF96.2 cell line.

Wilms' tumor gene 1 (WT1) plays complex roles in tumorigenesis, acting as tumor suppressor gene or an oncogene depending on the cellular context. WT1 expression has been variably reported in both benign and malignant peripheral nerve sheath tumors (MPNSTs) by means of immunohistochemistry. The aim of the present study was to characterize its potential pathogenetic role in these relatively uncommon malignant tumors. Firstly, immunohistochemical analyses in MPNST sNF96.2 cell line showed strong WT1 staining in nuclear and perinuclear areas of neoplastic cells. Thus, we investigated the effects of silencing WT1 by RNA interference. Through Western Blot analysis and proliferation assay we found that WT1 knockdown leads to the reduction of cell growth in a time- and dose-dependent manner. siWT1 inhibited proliferation of sNF96.2 cell lines likely by influencing cell cycle progression through a decrease in the protein levels of cyclin D1 and inhibition of Akt phosphorylation compared to the control cells. These results indicate that WT1 knockdown attenuates the biological behavior of MPNST cells by decreasing Akt activity, demonstrating that WT1 is involved in the development and progression of MPNSTs. Thus, WT1 is suggested to serve as a potential therapeutic target for MPNSTs

The inflammasome adaptor ASC delays UV-induced skin tumorigenesis in Beta HPV38 E6 and E7 Transgenic mice.

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The complete mitochondrial genome of the zebra seabream Diplodus cervinus (Perciformes, Sparidae) from the Mediterranean Sea

The complete nucleotide sequence of the mitochondrial (mt) genome of the demersal zebra seabream Diplodus cervinus (Lowe, 1838) was determined for the first time. The double stranded circular molecule is 16,559 base pairs (bp) in length and encodes for the typical 37 metazoan mitochondrial genes, and 2 non-coding regions (D-loop and L-origin). The gene arrangement of the D. cervinus mt genome follows the usual one for fishes. The nucleotide sequences of the mt protein coding and ribosomal genes of D. cervinus mt genome were aligned with orthologous sequences from representatives of the Sparidae family and phylogenetic relationships were inferred. Maximum likelihood analyses placed D. cervinus as a sister species of Diplodus sargus (Linnaeus, 1758)