Detection of Signal Regulatory Protein α in Saimiri sciureus (Squirrel Monkey) by Anti-Human Monoclonal Antibody

Abstract

Non-human primates (NHP) are suitable models for studying different aspects of the human system, including pathogenesis and protective immunity to many diseases. However, the lack of specific immunological reagents for neo-tropical monkeys, such as Saimiri sciureus, is still a major factor limiting studies in these models. An alternative strategy to circumvent this obstacle has been the selection of immunological reagents directed to humans, which present cross-reactivity with NHP molecules. In this context and considering the key role of inhibitory immunoreceptors—such as the signal regulatory protein α (SIRPα)—in the regulation of immune responses, in the present study, we attempted to evaluate the ability of anti-human SIRPα monoclonal antibodies to recognize SIRPα in antigen-presenting S. sciureus peripheral blood mononuclear cells (PBMC). As shown by flow cytometry analysis, the profile of anti-SIRPα staining as well as the levels of SIRPα-positive cells in PBMC from S. sciureus were similar to those observed in human PBMC. Furthermore, using anti-SIRPα monoclonal antibody, it was possible to detect a decrease of the SIRPα levels on surface of S. sciureus cells after in vitro stimulation with lipopolysaccharides. Finally, using computed-based analysis, we observed a high degree of conservation of SIRPα across six species of primates and the presence of shared epitopes in the extracellular domain between humans and Saimiri genus that could be targeted by antibodies. In conclusion, we have identified a commercially available anti-human monoclonal antibody that is able to detect SIRPα of S. sciureus monkeys and that, therefore, can facilitate the study of the immunomodulatory role of SIRPα when S. sciureus is used as a model.

Modulation of Signal Regulatory Protein α (SIRPα) by Plasmodium Antigenic Extract: A Preliminary In Vitro Study on Peripheral Blood Mononuclear Cells

“…As expected, stimulation of PBMCs with LPS by 24 and 48 h resulted in a decreased expression of SIRPα in the population of monocyte-like cells characterized by morphology criteria in flow cytometry analysis ( Figure 1 ). This is in agreement with previous studies in which Saimiri monkey PBMCs [ 28 ], mouse macrophages [ 29 ] and DCs derived from human peripheral blood or mouse bone marrow [ 30 ] were stimulated with LPS. Similar downregulation of SIRPα has also been described after viral double-stranded RNA (polyI:C) stimulation of mouse macrophages, in which SIRPα signaling was shown to negatively regulate TLR3-dependent antiviral pathways [ 31 ].…”

Class C CpG Oligodeoxynucleotide Immunomodulatory Response in Aged Squirrel Monkey (Saimiri Boliviensis Boliviensis)

“…However, manifestation of target organ toxicity represented as the occurrence of leukocyte infiltrates within the major organs of deposition has not been observed in our initial mouse reports, further supporting the safety of this immunomodulatory approach (Scholtzova et al, 2014(Scholtzova et al, , 2017. In addition, the present findings should be interpreted with caution, because only selected cross-reactive reagents with specific cell subpopulations were included in this study (de Souza et al, 2017). It is also important to note that the small size of SQMs limits the volume of blood that can be collected at any time point.…”