Interferon gamma (IFN-γ) negative CD4+ and CD8+ T-cells can produce immune mediators in response to viral antigens

Abstract

Evaluation of antigen-specific T-cell responses to viral antigens is frequently performed on IFN-γ secreting cells. However, T-cells are capable of producing many more functions than just IFN-γ, some of which, like Perforin, are associated with immune protection in HIV-1 disease elite controllers. We evaluated the extent of missed T-cell functions when IFN-γ secretion is used as a surrogate marker for further evaluation of T-cell functions. Intracellular cytokine staining assay and flow cytometry were used to assess peripheral blood mononuclear cells (PBMCs) from 31 HIV-infected ART-naive individuals for the extent to which gated CD4+ and CD8+ IFN-γ producing and non-producing T-cells also secreted IL-2, Perforin, and TNF-α functions. Similarly, the extent of missed virus-specific responses in IFN-γ ELISpot assay negative T-cells from 5 HIV-1 uninfected individuals was evaluated. Cells from HIV-infected individuals were stimulated with pooled consensus group M (Con M) peptides; and those from healthy individuals were stimulated with pooled adenovirus (Ad) peptides. Overall, frequencies of virus-specific IFN-γ secreting CD4+ and CD8+ cells were low. Proportions of IFN-γ negative CD4+ expressing IL-2, Perforin, or TNF-α to Con M were significantly higher (5 of 7 functional profiles) than the corresponding IFN-γ positive CD4+ (0 of 7) T-cell phenotype, p = 0.02; Fisher’s Exact test. Likewise, proportions of CD8+ T-cells expressing other functions were significantly higher in 4 of the 7 IFN-γ negative CD8+ T-cells. Notably, newly stimulated Perforin, identified as Perforin co-expression with IL-2 or TNF-α, was significantly higher in IFN-γ negative CD8+ T-cell than in the positive CD8+ T-cells. Using SEB, lower responses in IFN-γ positive cells were most associated with CD4+ than CD8+ T-cells. These findings suggest that studies evaluating immunogenicity in response to HIV and Adenovirus viral antigens should not only evaluate T-cell responsiveness among IFN-γ producing cells but also among those T-cells that do not express IFN-γ.

COVID-19 vaccine mRNA-1273 elicits a protective immune profile in mice that is not associated with vaccine-enhanced disease upon SARS-CoV-2 challenge

“…Whether this reflects immune modulation by SARS-CoV-2 or intrinsic properties of S-specific cells remains to be determined. Importantly, approaches that focus solely on IFNg detection, particularly IFNg ELISpot, could severely underestimate the SARS-CoV-2 T cell response following either vaccination or infection (Dan et al, 2016;Nakiboneka et al, 2019). We suspect that the IL-2 + IFNg À CD4 + T cells detected 2 weeks post-boost following mRNA-1273 immunization in our study may reflect a primed but uncommitted subpopulation of memory cells with effector potential poised for differentiation into Th1 and Th2 cells depending on the cytokine microenvironment (Mosmann et al, 2009).…”

Identification of Protective CD8 T Cell Responses in a Mouse Model of Zika Virus Infection

“…By requiring the T cells to produce cytokine as a means of identification we biased our results toward these effector cell populations potentially missing ZIKV specific CD8+ T cell populations that do not make these cytokine responses. As such, it should be noted that studies have demonstrated that the T cells that don't produce IFN-y may be important for control of some viruses (68). Additionally, the use of 15mer amino acids to screen for epitopes requires some level of processing to the optimal 9mer for CD8+ T cell stimulation and identification, therefore we could miss epitopes that could not be optimally processed.…”

Identification of a Hematopoietic Cell Population Emerging From Mouse Bone Marrow With Proliferative Potential In Vitro and Immunomodulatory Capacity

“…Our study showed that co-culture of MSC with activated T cells in the presence of L-NAME partially reversed the MSC inhibitory effect. It is important to emphasize that this effect was elicited by IFNγ and TNFα, which were actively secreted by activated T cells ( 59 , 60 ), and in their absence MSC did not produced NO ( 40 , 46 ). Indeed, our in vitro studies confirmed that only MSC stimulated with both IFNγ and TNFα produced high levels of nitrite in the culture medium.…”