Expansion of Immature Neutrophils During SIV Infection Is Associated With Their Capacity to Modulate T-Cell Function

In spite of the efficacy of combinational antiretroviral treatment (cART), HIV-1 persists in the host and infection is associated with chronic inflammation, leading to an increased risk of comorbidities, such as cardiovascular diseases, neurocognitive disorders, and cancer. Myeloid cells, mainly monocytes and macrophages, have been shown to be involved in the immune activation observed in HIV-1 infection. However, less attention has been paid to neutrophils, the most abundant circulating myeloid cell, even though neutrophils are strongly involved in tissue damage and inflammation in several chronic diseases, in particular, autoimmune diseases. Herein, we performed a longitudinal characterization of neutrophil phenotype and we evaluated the interplay between neutrophils and T cells in the model of pathogenic SIVmac251 experimental infection of cynomolgus macaques. We report that circulating granulocytes consists mainly of immature CD10- neutrophils exhibiting a prime phenotype during primary and chronic infection. We found that neutrophil priming correlates with CD8⁺ T cell activation. Moreover, we provide the evidence that neutrophils are capable of modulating CD4⁺ and CD8⁺ T-cell proliferation and IFN-γ production in different ways depending on the time of infection. Thus, our study emphasizes the role of primed immature neutrophils in the modulation of T-cell responses in SIV infection.

Abstract 5531: K0401-020 anti-VISTA antibody monotherapy increases specific CD8 T cell response in non-human primates

Background: VISTA is a B7 family protein described as a negative checkpoint of T cell responses, both in autoimmunity and cancer murine models. K01401-020 is a novel IND enabling anti-VISTA antibody. In vitro, when incubated with human blood cells, K01401-020 stimulates NK cells, monocytes and cytokine production, contributing to T cell activation. In vivo, in non-human primates, K01401-020 notably induced dendritic cell activation (Loukili et al, AACR 2019). However, so far, no in vivo demonstration of anti-VISTA pharmacodynamic effect on T cells has been demonstrated beyond mouse models. Thus, we explored the effect of anti-VISTA antibody on CD8 T cell specific activation in non-human primates, using SIV immunization as a model.

Methods: The detection of T cell response amplification by immune-checkpoint inhibitors is very challenging in primates during standard PK or safety studies in the absence of adequate antigen stimulation. KLH is described as an immunogen in monkeys but induces mainly a humoral (IgG/IgM) and not a CD8 response, and thus cannot reveal the pharmacodynamic activity of immune-checkpoint inhibitors. Here, we explored well-described model of primate immunization that induces specifically a cellular response including CD8 (Martinon et al, Hum Gene Ther. 2009) to reveal the activity of Immune-checkpoints inhibitors.

Groups of three adult cynomolgus macaques were immunized thrice with 1mg of MultiSIVmac239 GTU-DNA, by intradermal route with electroporation. One-day after the last immunization, animals received a single intravenous injection of either vehicle, anti-PD1 antibody (pembrolizumab) or anti-VISTA antibody K01401-020. IFNγ ELISPOT assay was performed on PBMCs in the presence of either Nef RM9 peptide or Gag (peptide pool), while RM9 tetramer assay and cell subsets phenotyping were performed on whole blood.

Results: RM9 and gag-specific CD8 responses were evidenced as soon as after the second immunization in at least 2/3 animals from all groups. The third immunization reactivated CD8-specific responses in all groups. Pembrolizumab and anti-VISTA antibody clearly amplified CD8 specific responses respectively in 2/3 and 3/3 monkeys.

Conclusions: Here we show for the first time that a single anti-VISTA antibody infusion monotherapy in non-human primates potentializes specific CD8 T cell responses against exogenous antigen. The above data suggests that anti-VISTA antibody K01401-020 given as a single agent may effectively boosts CD8 T cell activity against tumor antigens.

Confidential – Pierre Fabre and CEA collaboration

Citation Format: Christine Libon, Isabelle Vandenberghe, Romain Marlin, Wesley Gros, Marco Leonec, Mario Gomez-Pacheco, Anne-Sophie Gallouet, Françoise Fraboul, Abderrahim Mahfoudi, Nathalie Dereuddre-Bosquet, Pierre Ferré. K0401-020 anti-VISTA antibody monotherapy increases specific CD8 T cell response in non-human primates [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5531.

A phylogenetic framework of the legume genus Aeschynomene for comparative genetic analysis of the Nod-dependent and Nod-independent symbioses

BACKGROUND

Among semi-aquatic species of the legume genus Aeschynomene, some have the property of being nodulated by photosynthetic Bradyrhizobium lacking the nodABC genes necessary for the synthesis of Nod factors. Knowledge of the specificities underlying this Nod-independent symbiosis has been gained from the model legume Aeschynomene evenia but our understanding remains limited due to the lack of comparative genetics with related taxa using a Nod factor-dependent process. To fill this gap, we combined different approaches to perform a thorough comparative analysis in the genus Aeschynomene.

RESULTS

This study significantly broadened previous taxon sampling, including in allied genera, in order to construct a comprehensive phylogeny. In the phylogenetic tree, five main lineages were delineated, including a novel lineage, the Nod-independent clade and another one containing a polytomy that comprised several Aeschynomene groups and all the allied genera. This phylogeny was matched with data on chromosome number, genome size and low-copy nuclear gene sequences to reveal the diploid species and a polytomy containing mostly polyploid taxa. For these taxa, a single allopolyploid origin was inferred and the putative parental lineages were identified. Finally, nodulation tests with different Bradyrhizobium strains revealed new nodulation behaviours and the diploid species outside of the Nod-independent clade were compared for their experimental tractability and genetic diversity.

CONCLUSIONS

The extended knowledge of the genetics and biology of the different lineages sheds new light of the evolutionary history of the genus Aeschynomene and they provide a solid framework to exploit efficiently the diversity encountered in Aeschynomene legumes. Notably, our backbone tree contains all the species that are diploid and it clarifies the genetic relationships between the Nod-independent clade and the Nod-dependent lineages. This study enabled the identification of A. americana and A. patula as the most suitable species to undertake a comparative genetic study of the Nod-independent and Nod-dependent symbioses.

Naturally occurring variations in the nod-independent model legume Aeschynomene evenia and relatives: a resource for nodulation genetics

BACKGROUND

Among semi-aquatic species of the legume genus Aeschynomene, some have the unique property of being root and stem-nodulated by photosynthetic Bradyrhizobium lacking the nodABC genes necessary for the production of Nod factors. These species provide an excellent biological system with which to explore the evolution of nodulation in legumes. Among them, Aeschynomene evenia has emerged as a model legume to undertake the genetic dissection of the so-called Nod-independent symbiosis. In addition to the genetic analysis of nodulation on a reference line, natural variation in a germplasm collection could also be surveyed to uncover genetic determinants of nodulation. To this aim, we investigated the patterns of genetic diversity in a collection of 226 Nod-independent Aeschynomene accessions.

RESULTS

A combination of phylogenetic analyses, comprising ITS and low-copy nuclear genes, along with cytogenetic experiments and artificial hybridizations revealed the richness of the Nod-independent Aeschynomene group with the identification of 13 diploid and 6 polyploid well-differentiated taxa. A set of 54 SSRs was used to further delineate taxon boundaries and to identify different genotypes. Patterns of microsatellite diversity also illuminated the genetic basis of the Aeschynomene taxa that were all found to be predominantly autogamous and with a predicted simple disomic inheritance, two attributes favorable for genetics. In addition, taxa displaying a pronounced genetic diversity, notably A. evenia, A. indica and A. sensitiva, were characterized by a clear geographically-based genetic structure and variations in root and stem nodulation.

CONCLUSION

A well-characterized germplasm collection now exists as a major genetic resource to thoroughly explore the natural variation of nodulation in response to different bradyrhizobial strains. Symbiotic polymorphisms are expected to be found notably in the induction of nodulation, in nitrogen fixation and also in stem nodulation. Subsequent genetic analysis and locus mapping will pave the way for the identification of the underlying genes through forward or reverse genetics. Such discoveries will significantly contribute to our understanding of the molecular mechanisms underpinning how some Aeschynomene species can be efficiently nodulated in a Nod-independent fashion.