149 research outputs found
Inhibition of p38 MAP kinase pathway induces apoptosis and prevents Epstein Barr virus reactivation in Raji cells exposed to lytic cycle inducing compounds
No full textBackground: EBV lytic cycle activators, such as phorbol esters, anti-immunoglobulin, transforming growth factor b (TGFb), sodium butyrate, induce apoptosis in EBV-negative but not in EBV-positive Burkitt's lymphoma (BL) cells. To investigate the molecular mechanisms allowing EBV-infected cells to be protected, we examined the expression of viral and cellular antiapoptotic proteins as well as the activation of signal transduction pathways in BL-derived Raji cells exposed to lytic cycle inducing agents. Results: Our data show that, following EBV activation, the latent membrane protein 1 (LMP1) and the cellular anti-apoptotic proteins MCL-1 and BCL-2 were quickly up-regulated and that Raji cells remained viable even when exposed simultaneously to P(BU)(2), sodium butyrate and TGFb. We report here that inhibition of p38 pathway, during EBV activation, led to a three fold increment of apoptosis and largely prevented lytic gene expression. Conclusion: These findings indicate that, during the switch from the latent to the lytic phase of EBV infection, p38 MAPK phosphorylation plays a key role both for protecting the host cells from apoptosis as well as for inducing viral reactivation. Because Raji cells are defective for late antigens expression, we hypothesize that the increment of LMP1 gene expression in the early phases of EBV lytic cycle might contribute to the survival of the EBV-positive cells
Epstein-Barr virus lytic cycle activation alters proteasome subunit expression in Burkitt's lymphoma cells
No full textWe have shown that Epstein-Barr virus (EBV) lytic cycle activation in Burkitt's lymphoma (BL) cells down-regulates chymotrypsin- and caspase-like activities of the proteasome. The aim of the present study was to evaluate whether EBV activation might also affect proteasome subunit composition. Our results indicate that, independently of the latency program established in the host cells, induction of the EBV lytic cycle reduces the expression of the proteasomal components beta 5, beta 1 and beta 2i, whereas it increases that of beta 2, beta 1i, PA28 alpha and PA28 beta. The modulation of the composition and enzymatic activities of the proteolytic complex are indicative of a less efficient generation of viral immunoepitopes
TTV and other anelloviruses: The astonishingly wide spread of a viral infection
No full textThe broad family of viruses known as anelloviruses (AV) infects both humans and numerous animal species. They have a tiny, covalently closed single-stranded DNA genome and the astonishing capacity to infect a very high percentage of healthy and ill people with chronic infections that could last a lifetime. AV, and particularly the prototype Torquetenovirus, have established a successful interaction with the host's immune system and the rate at which they replicate is a gauge to measure overall immune function, even though many aspects of their life cycle and pathogenesis are still poorly understood
Down-regulation of proteolytic complexes following EBV activation in BL cells
No full textIn Burkitt's lymphoma cells, Epstein Barr virus (EBV) latency products interact with the ubiquitin-proteasome system to promote episomal maintenance and immunological evasion while the tripeptidylpeptidase II (TPPII) functions as an alternative protease. In the present study, we have examined the activities and levels of the proteasome and TPPII complex in Raji and in Akata cells after induction of EBV lytic cycle. The results show that the chymotrypsin-like and caspase-like activities of the proteasome were substantially reduced in Raji and Akata cells. Similarly, TPPII activity was diminished in both cell lines but was recovered in Akata cells at longer time after induction. Protein levels of the alpha/beta subunits of the 20S proteasome and TPPII concentration decreased to different extents after EBV activation, whereas the ubiquitin binding S6' subunit of the 19S regulatory complex increased three to fourfold along with the levels of ubiquitin-conjugates. Collectively, these observations demonstrate impairment of two major cellular proteolytic systems at the onset of EBV lytic infection. (c) 2006 Elsevier Inc. All rights reserved
“Modulation of NKG2D and DNAM-1 activating receptors and their ligands during HIV-1 infection”.
No full textNatural killer (NK) cells play a critical role in host defense against viral infections.
Chronic HIV-1 infection is associated with an accumulation of dysfunctional NK
cell, that unsuccessfully control viral replication. However, the underlying
mechanisms for this NK cell dysfunction are poorly understood.
NK cells do not express an antigen
specific receptor, as do other lymphocytes. Instead, NK cells encode a variety of
different activating and inhibitory receptors and NK cell activation is dependent on a
delicate balance between signals of opposite sign elicited by the multiple NK cell
receptor–ligand interactions that follow NK cell–target cell interaction.
The goal of my PhD project was to analyze the role of NK cell activating pathways
upon HIV-1 infection.
Specifically, I studied the modulation of the activating receptor NKG2D with
particular interest on the mechanism of release, namely shedding, of its ligands
(NKG2DLs) during HIV-1 infection in in vitro cell systems as well as in HIVinfected
patients.
Moreover, I investigated the modulation by viral proteins, such as Nef and Vpu, of
PVR (Poliovirus Receptor, CD155, Necl-5) a ligand for another stimulatory
receptor, DNAM-1 (DNAX accessory molecule-1 or CD226).The final goal of this work was to identify novel factors that regulate the function of
immune responses against HIV-1 and that could provide new prognostic biomarkers
and innovative antiviral strategies.The work was supported by grants of the Italian Ministry of Health, Programma
Nazionale di Ricerca sull’AIDS’ in collaboration with ISS and Ricerca Corrente 2010 cofunded by the Italian 5 x 1000 contribution 2008 and by grants of the Italian
Association for Cancer Research (AIRC), the Italian Ministry of University and Research
(MIUR), and the “Sapienza” University of Rome, Ital
Soluble ligands for the NKG2D receptor are released during HIV-1 infection and impair NKG2D expression and cytotoxicity of NK cells
No full textIn humans, the interaction of the natural killer group 2 member D (NKG2D)-activating receptor on natural killer (NK) and CD8+ T cells with its major histocompatibility complex class I-related chain (MIC) and UL16 binding protein (ULBP) ligands (NKG2DLs) promotes recognition and elimination of stressed cells, such as tumor or infected cells. Here, we investigated the capacity of HIV-1 to modulate NKG2DL expression and escape NGK2D-mediated immunosurveillance. In CD4+ T lymphocytes, both cell surface expression and release of MICA, MICB, and ULBP2 were up-regulated >2-fold by HIV-1 infection. In HIV-infected CD4+ T lymphocytes or Jurkat T-cell lines, increased shedding of soluble NKG2DLs (sNKG2DLs) was impaired by a matrix metalloproteinase inhibitor (MMPI). Moreover, naive HIV+ patients displayed increased plasma sMICA and sULBP2 levels and reduced NKG2D expression on NK and CD8+ T cells compared to patients receiving highly active antiretroviral therapy (HAART) or healthy donors. In individual patients, HAART uptake resulted in the drop of sNKG2DL and recovery of NKG2D expression. Finally, sNKG2DLs in patients' plasma down-regulated NKG2D on NK and CD8 + T cells and impaired NKG2D-mediated cytotoxicity of NK cells. Thus, NKG2D detuning by sNKG2DLs may promote HIV-1 immune evasion and compromise host resistance to opportunistic infections, but HAART and MMPI have the potential to avoid such immune dysfunction. © FASEB.Abstract
In humans, the interaction of the natural killer group 2 member D (NKG2D)-activating receptor on natural killer (NK) and CD8(+) T cells with its major histocompatibility complex class I-related chain (MIC) and UL16 binding protein (ULBP) ligands (NKG2DLs) promotes recognition and elimination of stressed cells, such as tumor or infected cells. Here, we investigated the capacity of HIV-1 to modulate NKG2DL expression and escape NGK2D-mediated immunosurveillance. In CD4(+) T lymphocytes, both cell surface expression and release of MICA, MICB, and ULBP2 were up-regulated >2-fold by HIV-1 infection. In HIV-infected CD4(+) T lymphocytes or Jurkat T-cell lines, increased shedding of soluble NKG2DLs (sNKG2DLs) was impaired by a matrix metalloproteinase inhibitor (MMPI). Moreover, naive HIV(+) patients displayed increased plasma sMICA and sULBP2 levels and reduced NKG2D expression on NK and CD8(+) T cells compared to patients receiving highly active antiretroviral therapy (HAART) or healthy donors. In individual patients, HAART uptake resulted in the drop of sNKG2DL and recovery of NKG2D expression. Finally, sNKG2DLs in patients' plasma down-regulated NKG2D on NK and CD8(+) T cells and impaired NKG2D-mediated cytotoxicity of NK cells. Thus, NKG2D detuning by sNKG2DLs may promote HIV-1 immune evasion and compromise host resistance to opportunistic infections, but HAART and MMPI have the potential to avoid such immune dysfunction
Inhibition of Poly(ADP-ribose)polymerase impairs Epstein Barr Virus lytic cycle progression
No full textAbstract Background Poly(ADP-ribosylation) is a post-translational modification of nuclear proteins involved in several cellular events as well as in processes that characterize the infective cycle of some viruses. In the present study, we investigated the role of poly(ADP-ribosylation) on Epstein-Barr Virus (EBV) lytic cycle activation. Results Inhibition of PARP-1 by 3-aminobenzamide (3-ABA) during EBV induction, diminished cell damage and apoptosis in the non-productive Raji cell line while markedly reducing the release of viral particles in the productive Jijoye cells. Furthermore, incubation with 3-ABA up-regulated the levels of LMP1 and EBNA2 latent viral proteins. At the same time, it slightly affected the expression of the immediate early BZLF1 gene, but largely down-regulated the levels of the early BFRF1 protein. The modulation of the expression of both latent and lytic EBV genes appeared to be post-transcriptionally regulated. Conclusion Taken together the data indicate that PARP-1 plays a role in the progression of EBV lytic cycle and therefore, PARP inhibitors might represent suitable pharmacological adjuncts to control viral spread in EBV productive infection.</p
SARS-CoV-2 Breakthrough Infections According to the Immune Response Elicited after mRNA Third Dose Vaccination in COVID-19-Naïve Hospital Personnel
No full textBackground: Vaccine-induced SARS-CoV-2-anti-spike antibody (anti-S/RBD) titers are often used as a marker of immune protection and to anticipate the risk of breakthrough infections, although no clear cut-off is available. We describe the incidence of SARS-CoV-2 vaccine breakthrough infections in COVID-19-free personnel of our hospital, according to B- and T-cell immune response elicited one month after mRNA third dose vaccination. Methods: The study included 487 individuals for whom data on anti-S/RBD were available. Neutralizing antibody titers (nAbsT) against the ancestral Whuan SARS-CoV-2, and the BA.1 Omicron variant, and SARS-CoV-2 T-cell specific response were measured in subsets of 197 (40.5%), 159 (32.6%), and 127 (26.1%) individuals, respectively. Results: On a total of 92,063 days of observation, 204 participants (42%) had SARS-CoV-2 infection. No significant differences in the probability of SARS-CoV-2 infection for different levels of anti-S/RBD, nAbsT, Omicron nAbsT, or SARS-CoV-2 T cell specific response, and no protective thresholds for infection were found. Conclusions: Routine testing for vaccine-induced humoral immune response to SARS-CoV-2 is not recommended if measured as parameters of ‘protective immunity’ from SARS-CoV-2 after vaccination. Whether these findings apply to new Omicron-specific bivalent vaccines is going to be evaluated
Antiviral potential of Vδ2 T-cells in children given TCR αβ/CD19 cell depleted HLA-haploidentical HSCT
No full textgamma delta T cells represent key players in immune surveillance after T-cell receptor alpha/beta (alpha beta)/CD19depleted HLA-haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Although encouraging data are available on the impact of V delta 2-targeting therapy in improving HSCT clinical outcomes, their role in providing antimicrobial immunity is largely unexplored. This study aimed to investigate the antiviral protective profile of V delta 2 T cells in pediatric patients given haplo-HSCT. The characterization of gamma delta T cells was performed in pediatric recipients (n = 26) in the donor graft and at 30, 60, and 120 days after haplo-HSCT. The antiviral activity of V delta 2 T cells and the cytomegalovirus (CMV)-specific alpha beta T-cell immunity was analyzed. Early after HSCT, V delta 2 T cells was significantly higher in patients who did not experience viral reactivation (No-VR) than in patients with CMV reactivation. Interestingly, this difference was already present in the grafts. Clustering analysis identified a protective subset of V delta 2 T cells in patients with No-VR, expressing CD16, NKG2D, and CD107a, and producing Th1 cytokines. This subset directly correlated with interleukin-15 and inversely with the CMV DNA level. Stimulated V delta 2 T cells inhibit CMV replication, acquired CD86/HLA-DR molecules, induced HLA-DR on monocytes, and improved the alpha beta CMV-specific T-cell response. Altogether, these results identify an antiviral protective profile displayed by V delta 2 T cells early after HSCT, and define their ability to inhibit CMV replication, to induce antigen-presenting cell maturation and to improve alpha beta virus-specific T-cell response, opening a new application of V delta 2-targeting immunotherapy after HSCT, adding the antiviral to the antitumor potential
Strong immunogenicity of heterologous prime-boost immunizations with the experimental vaccine GRAd-COV2 and BNT162b2 or ChAdOx1-nCOV19
No full textHere we report on the humoral and cellular immune response in eight volunteers who autonomously chose to adhere to the Italian national COVID-19 vaccination campaign more than 3 months after receiving a single-administration GRAd-COV2 vaccine candidate in the context of the phase-1 clinical trial. We observed a clear boost of both binding/neutralizing antibodies as well as T-cell responses upon receipt of the heterologous BNT162b2 or ChAdOx1-nCOV19 vaccines. These results, despite the limitation of the small sample size, support the concept that a single dose of an adenoviral vaccine may represent an ideal tool to effectively prime a balanced immune response, which can be boosted to high levels by a single dose of a different vaccine platform
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