Laura Pattacini

Bystander-Activated Memory CD8 T Cells Control Early Pathogen Load in an Innate-like, NKG2D-Dependent Manner

During an infection the antigen-nonspecific memory CD8 T cell compartment is not simply an inert pool of cells, but becomes activated and cytotoxic. It is unknown how these cells contribute to the clearance of an infection. We measured the strength of T cell receptor (TCR) signals that bystander-activated, cytotoxic CD8 T cells (BA-CTLs) receive in vivo and found evidence of limited TCR signaling. Given this marginal contribution of the TCR, we asked how BA-CTLs identify infected target cells. We show that target cells express NKG2D ligands following bacterial infection and demonstrate that BA-CTLs directly eliminate these target cells in an innate-like, NKG2D-dependent manner. Selective inhibition of BA-CTL-mediated killing led to a significant defect in pathogen clearance. Together, these data suggest an innate role for memory CD8 T cells in the early immune response before the onset of a de novo generated, antigen-specific CD8 T cell response.

Differential effects of anti-TNF-α drugs on fibroblast-like synoviocyte apoptosis

OBJECTIVE Novel drugs targeting TNF-alpha are available for treatment of RA. Fibroblast-like synoviocytes (FLSs) play a fundamental role in RA progression, through their expansion caused in part by resistance to cell death induction. The aim of our study was to determine the effects of different anti-TNF-alpha agents on FLS apoptosis. METHODS FLS from patients with either RA or OA were co-cultured with peripheral blood mononuclear cells (PBMCs), and incubated with various drugs for 6 days. Subsequently, apoptosis induction was detected by Nucleosome ELISA and terminal deoxynucleotidyl transferase dUTP nick end labeling. Western blot was used to determine the activation of the phosphatase and tensin homologue deleted on chromosome 10 (PTEN)-focal adhesion kinase (FAK) pathway as well as Bax and Bcl-2 levels. Immunoprecipitation was used for studying phosphorylation of transmembrane TNF-alpha (tmTNF-alpha). RESULTS All the tested drugs induced apoptosis of FLSs in the presence of PBMCs obtained from the same patient only when the two cell populations were in direct contact by activating the PTEN-FAK pathway and increasing Bax levels. This effect was not due to antibody-dependent cell-mediated cytotoxicity. Only the two antibodies infliximab and adalimumab were able to up-regulate Bcl-2. CONCLUSIONS Etanercept is more effective in inducing FLS apoptosis compared with the other drugs tested. This induction is dependent on the presence of PBMCs, and involves the activation of PTEN-FAK pathway. Bcl-2 increase induced by the monoclonal antibodies infliximab and adalimumab may play a protective role and thus counteract their pro-apoptotic effect on FLSs.

-463 G/A myeloperoxidase promoter polymorphism in giant cell arteritis

Objective: To investigate potential associations between–463 G/A myeloperoxidase (MPO) promoter polymorphism and susceptibility to, and clinical features of giant cell arteritis (GCA). Methods: A total of 156 patients with biopsy-proven GCA who were residents of Reggio Emilia, Italy, and 235 population-based controls from the same geographic area were genotyped for–463 G/A promoter polymorphism of the MPO gene by molecular methods. The patients were subgrouped according to the presence or absence of polymyalgia rheumatica and severe ischaemic complications (visual loss and/or cerebrovascular accidents). Results: The distribution of the MPO-G/A genotype differed significantly between patients with GCA and the controls (pcorr = 0.003). Allele G was significantly more frequent in patients with GCA than in the controls (pcorr = 0.0002, OR 2.0, 95% CI 1.4 to 2.9). Homozygosity for the G allele was significantly more frequent in patients with GCA than in controls (pcorr = 0.0002, OR 2.2, 95% CI 1.4 to 3.4). No significant associations were found when patients with GCA with and without polymyalgia rheumatica or with and without severe ischaemic complications were compared. Conclusions: Our findings show that the–463 G/A promoter polymorphism of the MPO gene is associated with GCA susceptibility and support a role for MPO in the pathophysiology of GCA.

A novel HIV vaccine adjuvanted by IC31 induces robust and persistent humoral and cellular immunity

The HIV vaccine strategy that, to date, generated immune protection consisted of a prime-boost regimen using a canarypox vector and an HIV envelope protein with alum, as shown in the RV144 trial. Since the efficacy was weak, and previous HIV vaccine trials designed to generate antibody responses failed, we hypothesized that generation of T cell responses would result in improved protection. Thus, we tested the immunogenicity of a similar envelope-based vaccine using a mouse model, with two modifications: a clade C CN54gp140 HIV envelope protein was adjuvanted by the TLR9 agonist IC31®, and the viral vector was the vaccinia strain NYVAC-CN54 expressing HIV envelope gp120. The use of IC31® facilitated immunoglobulin isotype switching, leading to the production of Env-specific IgG2a, as compared to protein with alum alone. Boosting with NYVAC-CN54 resulted in the generation of more robust Th1 T cell responses. Moreover, gp140 prime with IC31® and alum followed by NYVAC-CN54 boost resulted in the formation and persistence of central and effector memory populations in the spleen and an effector memory population in the gut. Our data suggest that this regimen is promising and could improve the protection rate by eliciting strong and long-lasting humoral and cellular immune responses.

Antiretroviral Pre-Exposure Prophylaxis Does Not Enhance Immune Responses to HIV in Exposed but Uninfected Persons

BACKGROUND Antiretroviral preexposure prophylaxis (PrEP), using daily oral combination tenofovir disoproxil fumarate plus emtricitabine, is an effective human immunodeficiency virus (HIV) prevention strategy for populations at high risk of HIV acquisition. Although the primary mode of action for the protective effect of PrEP is probably direct antiviral activity, nonhuman primate studies suggest that PrEP may also allow for development of HIV-specific immune responses, hypothesized to result from aborted HIV infections providing a source of immunologic priming. We sought to evaluate whether PrEP affects the development of HIV-specific immune response in humans. METHODS AND RESULTS Within a PrEP clinical trial among high-risk heterosexual African men and women, we detected HIV-specific CD4(+) and CD8(+) peripheral blood T-cell responses in 10%-20% of 247 subjects evaluated. The response rate and magnitude of T-cell responses did not vary significantly between those assigned PrEP versus placebo, and no significant difference between those assigned PrEP and placebo was observed in measures of innate immune function. CONCLUSIONS We found no evidence to support the hypothesis that PrEP alters either the frequency or magnitude of HIV-specific immune responses in HIV-1-exposed seronegative individuals. These results suggest that PrEP is unlikely to serve as an immunologic prime to aid protection by a putative HIV vaccine.

Regulatory T-Cell Activity But Not Conventional HIV-Specific T-Cell Responses Are Associated With Protection From HIV-1 Infection.

Objective: Two distinct hypotheses have been proposed for T-cell involvement in protection from HIV-1 acquisition. First, HIV-1–specific memory T-cell responses generated on HIV-1 exposure could mount an efficient response to HIV-1 and inhibit the establishment of an infection. Second, a lower level of immune activation could reduce the numbers of activated, HIV-1–susceptible CD4+ T cells, thereby diminishing the likelihood of infection. Methods: To test these hypotheses, we conducted a prospective study among high-risk heterosexual men and women, and tested peripheral blood samples from individuals who subsequently acquired HIV-1 during follow-up (cases) and from a subset of those who remained HIV-1 uninfected (controls). Results: We found no difference in HIV-1–specific immune responses between cases and controls, but Treg frequency was higher in controls as compared with cases and was negatively associated with frequency of effector memory CD4+ T cells. Conclusions: Our findings support the hypothesis that low immune activation assists in protection from HIV-1 infection.