TACI, unlike BAFF-R, is solely activated by oligomeric BAFF and APRIL to support survival of activated B cells and plasmablasts.

The cytokine BAFF binds to the receptors TACI, BCMA, and BAFF-R on B cells, whereas APRIL binds to TACI and BCMA only. The signaling properties of soluble trimeric BAFF (BAFF 3-mer) were compared with those of higher-order BAFF oligomers. All forms of BAFF bound BAFF-R and TACI, and elicited BAFF-R-dependent signals in primary B cells. In contrast, signaling through TACI in mature B cells or plasmablasts was only achieved by higher-order BAFF and APRIL oligomers, all of which were also po-tent activators of a multimerization-dependent reporter signaling pathway. These results indicate that, although BAFF-R and TACI can provide B cells with similar signals, only BAFF-R, but not TACI, can respond to soluble BAFF 3-mer, which is the main form of BAFF found in circulation. BAFF 60-mer, an efficient TACI agonist, was also detected in plasma of BAFF transgenic and nontransgenic mice and was more than 100-fold more active than BAFF 3-mer for the activation of multimerization-dependent signals. TACI supported survival of activated B cells and plasmablasts in vitro, providing a rational basis to explain the immunoglobulin deficiency reported in TACI-deficient persons.

NLRC5 deficiency selectively impairs MHC class I- dependent lymphocyte killing by cytotoxic T cells.

Nucleotide-binding oligomerization domain-like receptors (NLRs) are intracellular proteins involved in innate-driven inflammatory responses. The function of the family member NLR caspase recruitment domain containing protein 5 (NLRC5) remains a matter of debate, particularly with respect to NF-κB activation, type I IFN, and MHC I expression. To address the role of NLRC5, we generated Nlrc5-deficient mice (Nlrc5(Δ/Δ)). In this article we show that these animals exhibit slightly decreased CD8(+) T cell percentages, a phenotype compatible with deregulated MHC I expression. Of interest, NLRC5 ablation only mildly affected MHC I expression on APCs and, accordingly, Nlrc5(Δ/Δ) macrophages efficiently primed CD8(+) T cells. In contrast, NLRC5 deficiency dramatically impaired basal expression of MHC I in T, NKT, and NK lymphocytes. NLRC5 was sufficient to induce MHC I expression in a human lymphoid cell line, requiring both caspase recruitment and LRR domains. Moreover, endogenous NLRC5 localized to the nucleus and occupied the proximal promoter region of H-2 genes. Consistent with downregulated MHC I expression, the elimination of Nlrc5(Δ/Δ) lymphocytes by cytotoxic T cells was markedly reduced and, in addition, we observed low NLRC5 expression in several murine and human lymphoid-derived tumor cell lines. Hence, loss of NLRC5 expression represents an advantage for evading CD8(+) T cell-mediated elimination by downmodulation of MHC I levels-a mechanism that may be exploited by transformed cells. Our data show that NLRC5 acts as a key transcriptional regulator of MHC I in lymphocytes and support an essential role for NLRs in directing not only innate but also adaptive immune responses.

Lentivector immunization induces tumor antigen-specific B and T cell responses in vivo.

Expression of the cancer/germ-line antigen NY-ESO-1 by tumors elicits spontaneous humoral and cellular immune responses in some cancer patients. Development of vaccines capable of stimulating such comprehensive immune responses is desirable. We have produced recombinant lentivectors directing the intracellular synthesis of NY-ESO-1 (rLV/ESO) and have analyzed the in vivo immune response elicited by this vector. Single injection of rLV/ESO into HLA-A2-transgenic mice elicited long-lasting B and T cell responses against NY-ESO-1. CD8+ T cells against the HLA-A2-restricted peptide NY-ESO-1(157-165) were readily detectable ex vivo and showed restricted TCR Vbeta usage. Moreover, rLV/ESO elicited a far greater anti-NY-ESO-1(157-165) CD8+ T cell response than peptide- or protein-based vaccines. Anti-NY-ESO-1 antibodies were rapidly induced after immunization and their detection preceded that of the antigen-specific CD8+ T cells. The rLV/ESO also induced CD4+ T cells. These cells played an essential role as their depletion completely abrogated B cell and CD8+ T cell responses against NY-ESO-1. The induced CD4+ T cells were primarily directed against a single NY-ESO-1 epitope spanning amino acids 81-100. Altogether, our study shows that rLV/ESO induces potent and comprehensive immune responses in vivo.

Activated B cells express functional Fas ligand.

Fas ligand (FasL, Apo-1L) is a member of the tumor necrosis factor protein family and binding to its receptor (Fas, Apo-1, CD95) triggers cell death through apoptosis. Ligand expression is restricted to cells with known cytolytic activity and found on hematopoietic cells of the T cell and natural killer lineage. Here we provide evidence that B lymphocytes can express FasL. Flow cytometric analysis revealed that FasL is expressed on the surface of B cells upon stimulation with either lipopolysaccharide or phorbol 12-myristate 13-acetate/ionomycin. FasL expression on activated B cells was confirmed by western blot and reverse transcriptase polymerase chain reaction analysis. FasL on B cells is functional since lipopolysaccharide-activated B lymphocytes derived from wild type, but not from gld mutant mice, were able to kill Fas-sensitive target cells. Our data suggest that the Fas system may contribute to the control of B cell homeostasis.

Peripheral T cell activation and deletion induced by transfer of lymphocyte subsets expressing endogenous or exogenous mouse mammary tumor virus.

Murine T cell reactivity with products of the minor lymphocyte stimulatory (Mls) locus correlates with the expression of particular variable (V) domains of the T cell receptor (TCR) beta chain. It was recently demonstrated that Mls antigens are encoded by an open reading frame (ORF) in the 3' long terminal repeat of either endogenous or exogenous mouse mammary tumor virus (MMTV). Immature thymocytes expressing reactive TCR-V beta domains are clonally deleted upon exposure to endogenous Mtv's. Mature T cells proliferate vigorously in response to Mls-1a (Mtv-7) in vivo, but induction of specific anergy and deletion after exposure to Mtv-7-expressing cells in the periphery has also been described. We show here that B cells and CD8+ (but not CD4+) T cells from Mtv-7+ mice efficiently induce peripheral deletion of reactive T cells upon transfer to Mtv-7- recipients, whereas only B cells stimulate specific T cell proliferation in vivo. In contrast to endogenous Mtv-7, transfer of B, CD4+, or CD8+ lymphocyte subsets from mice maternally infected with MMTV(SW), an infectious homologue of Mtv-7, results in specific T cell deletion in the absence of a detectable proliferative response. Finally, we show by secondary transfers of infected cells that exogenous MMTV(SW) is transmitted multidirectionally between lymphocyte subsets and ultimately to the mammary gland. Collectively our data demonstrate heterogeneity in the expression and/or presentation of endogenous and exogenous MMTV ORF by lymphocyte subsets and emphasize the low threshold required for induction of peripheral T cell deletion by these gene products.

gp100(209-2M) peptide immunization of human lymphocyte antigen-A2+ stage I-III melanoma patients induces significant increase in antigen-specific effector and long-term memory CD8+ T cells.

Thirty-five HLA-A2(+) patients with completely resected stage I-III melanoma were vaccinated multiple times over 6 months with a modified melanoma peptide, gp100(209-2M), emulsified in Montanide adjuvant. Direct ex vivo gp100(209-2M) tetramer analysis of pre- and postvaccine peripheral blood mononuclear cells (PBMCs) demonstrated significant increases in the frequency of tetramer(+) CD8(+) T cells after immunization for 33 of 35 evaluable patients (median, 0.36%; range, 0.05-8.9%). Ex vivo IFN-gamma cytokine flow cytometry analysis of postvaccine PBMCs after brief gp100(209-2M) in vitro activation showed that for all of the patients studied tetramer(+) CD8(+) T cells produced IFN-gamma; however, some patients had significant numbers of tetramer(+) IFN-gamma(-) CD8(+)T cells suggesting functional anergy. Additionally, 8 day gp100(209-2M) in vitro stimulation (IVS) of pre- and postvaccine PBMCs resulted in significant expansion of tetramer(+) CD8(+) T cells from postvaccine cells for 34 patients, and these IVS tetramer(+) CD8(+) T cells were functionally responsive by IFN-gamma cytokine flow cytometry analysis after restimulation with either native or modified gp100 peptide. However, correlated functional and phenotype analysis of IVS-expanded postvaccine CD8(+) T cells demonstrated the proliferation of functionally anergic gp100(209-2M)- tetramer(+) CD8(+) T cells in several patients and also indicated interpatient variability of gp100(209-2M) stimulated T-cell proliferation. Flow cytometry analysis of cryopreserved postvaccine PBMCs from representative patients showed that the majority of tetramer(+) CD8+ T cells (78.1 +/- 4.2%) had either an "effector" (CD45 RA(+)/CCR7(-)) or an "effector-memory" phenotype (CD45RA(-)/CCR7(-)). Notably, analysis of PBMCs collected 12-24 months after vaccine therapy demonstrated the durable presence of gp100(209-2M)-specific memory CD8(+) T cells with high proliferation potential. Overall, this report demonstrates that after vaccination with a MHC class I-restricted melanoma peptide, resected nonmetastatic melanoma patients can mount a significant antigen-specific CD8(+) T-cell immune response with a functionally intact memory component. The data further support the combined use of tetramer binding and functional assays in correlated ex vivo and IVS settings as a standard for immunomonitoring of cancer vaccine patients.

Clinical proteomics : a focus on transformed human T and B lymphocytes

Résumé large public La protéomique clinique est une discipline qui vise l'étude des protéines dans un but diagnostique ou thérapeutique. Nous avons utilisé cette approche pour étudier les lymphocytes T «tueurs » ou cytotoxiques qui font partie des globules blancs du système sanguin et agissent dans la lutte contre les infections et les tumeurs. Ces cellules sont impliquées dans l'immunothérapie cellulaire qui se fonde sur la capacité naturelle des ces lymphocytes à repérer les cellules tumorales et à les détruire. L'introduction du gène de la télomérase dans les lymphocytes T résulte en une prolongation de leur longévité, ce qui en ferait des candidats intéressants pour l'immunothérapie cellulaire. Il subsiste cependant des doutes quant aux conséquences de l'utilisation de ces lymphocytes «immortalisés ». Pour répondre à cette question, nous avons comparé le profile protéique de lymphocytes T cytotoxiques «jeunes » et vieux » avec celui des lymphocytes «immortalisés ». Nous avons trouvé que ces derniers présentent une double face et partagent à la fois les caractéristiques de la jeunesse et de la vieillesse. Dans une seconde étude de protéomique clinique, nous nous sommes penchés sur les lymphocytes B «immortalisés » cette fois-ci non pas avec la télomérase, mais avec le virus d'Epstein-Barr. Ces derniers sont utilisés comme modèle dans l'étude de la leucodystrophie, une maladie génétique rare qui affecte le cerveau. Notre but est d'identifier des marqueurs biologiques potentiels qui pourraient aider le diagnostic et le traitement de cette maladie neurodégénérative. Nous avons pour ce faire comparé les profiles protéiques des lymphocytes B «immortalisés » provenant d'individus sains et malades. Malheureusement, notre analyse n'a pas révélé de différences notoires entre ces deux classes de lymphocytes. Ceci nous permet toutefois de conclure que la maladie n'affecte pas la synthèse des protéines de manière prépondérante dans ces cellules sanguines. En résumé, le travail présenté dans cette thèse montre à la fois le potentiel et les limites de l'analyse des protéines lymphocytaires, dans différentes situations biologiques. Résumé La protéomique clinique ouvre la porte vers de multiples horizons relatifs au traitement de diverses maladies. Ce domaine particulier alliant la protéomique à la médecine, implique l'intervention de la biologie moléculaire et cellulaire. Dans notre étude, nous nous sommes d'abord intéressés aux lymphocytes T CD8+ cytotoxiques dans le contexte de l'immunothérapie adoptive. Le fondement de cette thérapie repose sur la capacité naturelle de ces lymphocytes à reconnaître les cellules tumorales et à les détruire chez les patients atteints de cancer. L'introduction du gène de la transcriptase réverse de la télomérase (hTERT) dans les lymphocytes T humains permet de rallonger leur durée de vie, sans toutefois induire d'altérations liées à la transformation. Cependant, des incertitudes subsistent quant à la ressemblance physiologique et biochimique entre ces cellules surexprirnant la télomérase et les cellules normales. Afin de répondre à cette question, nous avons comparé l'expression des protéines de lymphocytes humains T CD8+ «jeunes » et «vieux »avec celle de lymphocytes transduits avec hTERT. Nous avons trouvé que les lymphocytes T surexprimant la télomérase ont un profile protéique intermédiaire, avec certaines expressions protéiques similaires aux jeunes cellules T et d'autres se rapprochant des cellules vieilles. Dans la seconde partie de notre étude, nous nous sommes intéressés aux lymphocytes B transformés avec le virus d'Epstein-Barr provenant de patients atteints d'une maladie génétique rare du cerveau, la leucodystrophie. Dans cette maladie, des mutations dans le facteur de transcription eIF2B, impliqué dans la synthèse protéique, ont été trouvées. Afin d'analyser les conséquences de ces mutations et de trouver des biomarqueurs spécifiques à cette maladie, nous avons effectué une analyse protéomique des lymphoblastes provenant de malades et d'individus sains. Nous avons trouvé que les mutations dans le complexe ubiquitaire eIF2B n'affectent pas de manière significative l'expression des protéines des lymphoblastes mutés. En conclusion, notre travail illustre le potentiel et les limitations des technologies protéomiques utilisées pour disséquer l'implication des protéines dans différentes situations biologiques. Summary Clinical proteomics opens the door to multiple applications related to the treatment of diseases. This particular field is at the crossroad of proteomics and medicine and involves tools from cellular and molecular biology. We focused first our investigations on cytotoxic T cells in the context of adoptive immunotherapy, which is an interesting and evolving field. The basis of this therapy relies on the natural capacity of cytotoxic CD8+ T lymphocytes in recognizing tumor cells and destroying them in cancer patients. As their number is reduced, the idea would be to use transformed T lymphocytes with extended life span. Overexpression of telomerase into human T lymphocytes results in the extension of their replicative life span, but it still remains unclear whether these cells are physiologically indistinguishable from normal ones. To address this question, we compared the proteome of young and aged CD8+ T lymphocytes with that of T cells transduced with hTERT and found that the latter cells displayed an intermediate protein pattern, sharing similar protein expression with young, but also with aged T cells. We were then interested in studying Epstein-Barr virus transformed B lymphocytes in the context of a rare human brain genetic disorder called leukodystrophy. In this disease, mutations in the ubiquitous factor eIF2B involved in protein synthesis and its regulation have been reported. In order to analyze the functional consequences of the mutations and to find out specific biomarkers of eIF2B-related disorders, proteomic and peptidomic studies were carried out on lymphoblasts from eIF2Bmutated patients versus healthy patients. Following two-dimensional gel electrophoresis and mass fingerprints, mutations in the eIF2B complex did not appear to significantly affect the proteome of the mutated lymphoblasts extracts. To conclude, our work emphasizes the potentials and the limitations of the proteomic technologies used to analyze the role of lymphocyte proteins in different biological situations.

The Th2 lymphoproliferation developing in LatY136F mutant mice triggers polyclonal B cell activation and systemic autoimmunity.

Lat(Y136F) knock-in mice harbor a point mutation in Tyr(136) of the linker for activation of T cells and show accumulation of Th2 effector cells and IgG1 and IgE hypergammaglobulinemia. B cell activation is not a direct effect of the mutation on B cells since in the absence of T cells, mutant B cells do not show an activated phenotype. After adoptive transfer of linker for activation of T cell mutant T cells into wild-type, T cell-deficient recipients, recipient B cells become activated. We show in vivo and in vitro that the Lat(Y136F) mutation promotes T cell-dependent B cell activation leading to germinal center, memory, and plasma cell formation even in an MHC class II-independent manner. All the plasma and memory B cell populations found in physiological T cell-dependent B cell responses are found. Characterization of the abundant plasmablasts found in secondary lymphoid organs of Lat(Y136F) mice revealed the presence of a previously uncharacterized CD93-expressing subpopulation, whose presence was confirmed in wild-type mice after immunization. In Lat(Y136F) mice, B cell activation was polyclonal and not Ag-driven because the increase in serum IgG1 and IgE concentrations involved Abs and autoantibodies with different specificities equally. Although the noncomplement-fixing IgG1 and IgE are the only isotypes significantly increased in Lat(Y136F) serum, we observed early-onset systemic autoimmunity with nephritis showing IgE autoantibody deposits and severe proteinuria. These results show that Th2 cells developing in Lat(Y136F) mice can trigger polyclonal B cell activation and thereby lead to systemic autoimmune disease.

T and B lymphocytes exert distinct effects on the homeostasis of NK cells.

There is growing evidence that lymphocytes impact the development and/or function of other lymphocyte populations. Based on such observations we have tested whether the NK cell compartment was phenotypically and functionally altered in the absence of B and/or T cells. Here we show that T cell deficiency significantly accelerates BM NK cell production and the subsequent seeding of splenic and liver NK cell compartments. In contrast, B cell deficiency reduces splenic NK cell survival. In the absence of T and B cells, the size of the NK cell compartments is determined by the combination of these positive and negative effects. Even though NK cell homeostasis is significantly altered, NK cells from T and/or B cell-deficient mice show a normal capacity to kill a susceptible target cell line and to produce IFN. Nevertheless, we noted that the usage of MHC class I-specific Ly49 family receptors was significantly altered in the absence of T and/or B cells. In general, B cell deficiency expanded Ly49 receptor usage, while T cell deficiency exerted both positive and negative effects. These findings show that B and T cells significantly and differentially influence the homeostasis and the phenotype of NK cells.

Th2 activities induced during virgin T cell priming in the absence of IL-4, IL-13, and B cells.

Virgin T cells being primed to Th2-inducing or Th1-inducing Ags, respectively, start to synthesize IL-4 or IFN-gamma as they begin to proliferate. Parallel respective induction of B cells to produce gamma1 or gamma2a switch transcripts provides additional evidence of early divergent Th activity. This report concerns the roles of IL-4, IL-13, and B cells in these early events in vivo. Th2 responses were induced in lymph nodes against hapten-protein given s.c. with killed Bordetella pertussis adjuvant. In T cell proliferation in wild-type mice, IL-4 message up-regulation and gamma1 and epsilon switch transcript production were underway 48-72 h after immunization. The absence of IL-4, IL-13, or B cells did not alter the early T cell proliferative response. The gamma1 and epsilon switch transcript production was still induced in the absence of IL-4, IL-13, or both, but at a reduced level, while the dominance of switching to IgG1 in the extrafollicular hapten-specific plasma cell response was retained. The up-regulation of IL-4 message was not reduced or delayed in the absence of B cells and was only marginally reduced by the absence of IL-13. It is concluded that signals delivered by dendritic cells, which are not dependent on the presence of IL-4, IL-13, or B cells, can prime virgin T cells and induce the early Th2 activities studied. These early events that direct virgin T cells toward Th2 differentiation contrast with the critical later role of Th2 cytokines in selectively expanding Th2 clones and driving further IL-4 synthesis.

Peptide-antibody conjugates for tumour therapy: a MHC-class-II-restricted tetanus toxin peptide coupled to an anti-Ig light chain antibody can induce cytotoxic lysis of a human B-cell lymphoma by specific CD4 T cells.

Anti-idiotype antibody therapy of B-cell lymphomas, despite numerous promising experimental and clinical studies, has so far met with limited success. Tailor-made monoclonal anti-idiotype antibodies have been injected into a large series of lymphoma patients, with a few impressive complete tumour remissions but a large majority of negative responses. The results presented here suggest that, by coupling to antilymphoma idiotype antibodies a few molecules of the tetanus toxin universal epitope peptide P2 (830-843), one could markedly increase the efficiency of this therapy. We show that after 2-hr incubation with conjugates consisting of the tetanus toxin peptide P2 coupled by an S-S bridge to monoclonal antibodies directed to the lambda light chain of human immunoglobulin, human B-lymphoma cells can be specifically lysed by a CD4 T-lymphocyte clone specific for the P2 peptide. Antibody without peptide did not induce B-cell killing by the CD4 T-lymphocyte clone. The free cysteine-peptide was also able to induce lysis of the B-lymphoma target by the T-lymphocyte clone, but at a molar concentration 500 to 1000 times higher than that of the coupled peptide. Proliferation assays confirmed that the antibody-peptide conjugate was antigenically active at a much lower concentration than the free peptide. They also showed that antibody-peptide conjugates required an intact processing function of the B cell for peptide presentation, which could be selectively inhibited by leupeptin and chloroquine.(ABSTRACT TRUNCATED AT 250 WORDS)

Notch 1-deficient common lymphoid precursors adopt a B cell fate in the thymus.

We have recently reported that Notch 1, a member of the Notch multigene family, is essential for the development of murine T cells. Using a mouse model in which Notch 1 is inactivated in bone marrow (BM) precursors we have shown that B cells instead of T cells are found in the thymus of BM chimeras. However, it is not clear whether these B cells develop by default from a common lymphoid precursor due to the absence of Notch 1 signaling, or whether they arise as a result of perturbed migration of BM-derived B cells and/or altered homeostasis of normal resident thymic B cells. In this report we show that Notch 1-deficient thymic B cells resemble BM B cells in phenotype and turnover kinetics and are located predominantly in the medulla and corticomedullary junction. Peripheral blood lymphocyte analysis shows no evidence of recirculating Notch1(-/)- BM B cells. Furthermore, lack of T cell development is not due to a failure of Notch1(-/)- precursors to home to the thymus, as even after intrathymic reconstitution with BM cells, B cells instead of T cells develop from Notch 1-deficient precursors. Taken together, these results provide evidence for de novo ectopic B cell development in the thymus, and support the hypothesis that in the absence of Notch 1 common lymphoid precursors adopt the default cell fate and develop into B cells instead.

Effects of epitope modification on T cell receptor-ligand binding and antigen recognition by seven H-2Kd-restricted cytotoxic T lymphocyte clones specific for a photoreactive peptide derivative.

We tested for antigen recognition and T cell receptor (TCR)-ligand binding 12 peptide derivative variants on seven H-2Kd-restricted cytotoxic T lymphocytes (CTL) clones specific for a bifunctional photoreactive derivative of the Plasmodium berghei circumsporozoite peptide 252-260 (SYIPSAEKI). The derivative contained iodo-4-azidosalicylic acid in place of PbCS S-252 and 4-azidobenzoic acid on PbCS K-259. Selective photoactivation of the N-terminal photoreactive group allowed crosslinking to Kd molecules and photoactivation of the orthogonal group to TCR. TCR photoaffinity labeling with covalent Kd-peptide derivative complexes allowed direct assessment of TCR-ligand binding on living CTL. In most cases (over 80%) cytotoxicity (chromium release) and TCR-ligand binding differed by less than fivefold. The exceptions included (a) partial TCR agonists (8 cases), for which antigen recognition was five-tenfold less efficient than TCR-ligand binding, (b) TCR antagonists (2 cases), which were not recognized and capable of inhibiting recognition of the wild-type conjugate, (c) heteroclitic agonists (2 cases), for which antigen recognition was more efficient than TCR-ligand binding, and (d) one partial TCR agonist, which activated only Fas (C1)95), but not perforin/granzyme-mediated cytotoxicity. There was no correlation between these divergences and the avidity of TCR-ligand binding, indicating that other factors than binding avidity determine the nature of the CTL response. An unexpected and novel finding was that CD8-dependent clones clearly incline more to TCR antagonism than CD8-independent ones. As there was no correlation between CD8 dependence and the avidity of TCR-ligand binding, the possibility is suggested that CD8 plays a critical role in aberrant CTL function.

NLRC5 deficiency impairs MHC class I-dependent lymphocyte killing by cytotoxic T cells

Purpose/Objective: NLRs are intracellular proteins involved in sensing pathogen- and danger-associated molecular patterns, thereby initiating inflammatory responses or cell death. The function of the family member NLRC5 remains a matter of debate, particularly with respect to NF-jB activation, type I IFN, and MHC class I expression. Materials and methods: To study the function of this NLR in vivo, we generated Nlrc5-deficient mice. Results: We found that NLRC5 deletion led to a mild reduction in MHC class I expression on DCs and an intermediate decrease on B cells, while MHC class I levels were dramatically lowered on T, NKT, and NK cells. Nlrc5-/- lymphocytes showed decreased H-2 gene transcript abundance and, accordingly, NLRC5 was sufficient to drive MHC class I expression in a human lymphoid cell line. Moreover, endogenous NLRC5 localized to the nucleus and occupied the proximal promoter region of H-2 genes. Notably, cytotoxic T cell-mediated elimination of Nlrc5-/- lymphocytes was markedly reduced. In addition, we observed low NLRC5 expression in several murine and human lymphoid-derived tumor cell lines. Conclusions: We found that NLRC5 acts as a key transcriptional regulator of MHC class I genes, in particular in lymphocytes. Loss of NLRC5 expression represents an advantage for evading CD8+ T cellmediated elimination by downmodulation of MHCI levels * a mechanism transformed cells may take advantage of. Therefore, our data support an essential role for NLRs in directing not only innate, but also adaptive immune responses (Staehli F et al. J Immunol 2012).

Minor protease inhibitor mutations at baseline do not increase the risk for a virological failure in HIV-1 subtype B infected patients.

BACKGROUND: Minor protease inhibitor (PI) mutations often exist as polymorphisms in HIV-1 sequences from treatment-naïve patients. Previous studies showed that their presence impairs the antiretroviral treatment (ART) response. Evaluating these findings in a larger cohort is essential. METHODS: To study the impact of minor PI mutations on time to viral suppression and time to virological failure, we included patients from the Swiss HIV Cohort Study infected with HIV-1 subtype B who started first-line ART with a PI and two nucleoside reverse transcriptase inhibitors. Cox regression models were performed to compare the outcomes among patients with 0 and ≥ 1 minor PI mutation. Models were adjusted for baseline HIV-1 RNA, CD4 cell count, sex, transmission category, age, ethnicity, year of ART start, the presence of nucleoside reverse transcriptase inhibitor mutations, and stratified for the administered PIs. RESULTS: We included 1199 patients of whom 944 (78.7%) received a boosted PI. Minor PI mutations associated with the administered PI were common: 41.7%, 16.1%, 4.7% and 1.9% had 1, 2, 3 or ≥ 4 mutations, respectively. The time to viral suppression was similar between patients with 0 (reference) and ≥ 1 minor PI mutation (multivariable hazard ratio (HR): 1.1 [95% confidence interval (CI): 1.0-1.3], P = .196). The time to virological failure was also similar (multivariable HR:.9 [95% CI:.5-1.6], P = .765). In addition, the impact of each single minor PI mutation was analyzed separately: none was significantly associated with the treatment outcome. CONCLUSIONS: The presence of minor PI mutations at baseline has no effect on the therapy outcome in HIV infected individuals.