Multiple Layers of CD80/86-Dependent Costimulatory Activity Regulate Primary, Memory, and Secondary Lymphocytic Choriomeningitis Virus-Specific T Cell Immunity

Abstract

The lymphocytic choriomeningitis virus (LCMV) system constitutes one of the most widely used models for the study of infectious disease and the regulation of virus-specific T cell immunity. However, with respect to the activity of costimulatory and associated regulatory pathways, LCMV-specific T cell responses have long been regarded as relatively independent and thus distinct from the regulation of T cell immunity directed against many other viral pathogens. Here, we have reevaluated the contribution of CD28-CD80/86 costimulation in the LCMV system by use of CD80/86-deficient mice, and our results demonstrate that a disruption of CD28-CD80/86 signaling compromises the magnitude, phenotype, and/or functionality of LCMVspecific CD8 ؉ and/or CD4 ؉ T cell populations in all stages of the T cell response. Notably, a profound inhibition of secondary T cell immunity in LCMV-immune CD80/86-deficient mice emerged as a composite of both defective memory T cell development and a specific requirement for CD80 but not CD86 in the recall response, while a related experimental scenario of CD28-dependent yet CD80/86-independent secondary CD8 ؉ T cell immunity suggests the existence of a CD28 ligand other than CD80/ 86. Furthermore, we provide evidence that regulatory T cells (T REG s), the homeostasis of which is altered in CD80/86 ؊/؊ mice, contribute to restrained LCMV-specific CD8 ؉ T cell responses in the presence of CD80/86. Our observations can therefore provide a more coherent perspective on CD28-CD80/86 costimulation in antiviral T cell immunity that positions the LCMV system within a shared context of multiple defects that virus-specific T cells acquire in the absence of CD28-CD80/86 costimulation.T he generation of specific T cell immunity is governed by multiple determinants that shape the proliferative expansion and functional maturation of effector T cells (T E ) as well as their subsequent differentiation into memory T cells (T M ). Conceptualization of these processes permits the straightforward demarcation of T cell receptor (TCR)-peptide/major histocompatibility complex (MHC) interactions ("signal 1"), yet the simple notion of a defined "costimulus" required for the optimization of specific T cell responses, historically referred to as "signal 2," has been eroded by the realization that a multiplicity of diverse receptor-ligand interactions between T cells and antigen-presenting cells (APCs), soluble factors (e.g., cytokines), and specific temporospatial constraints operate in concert to control the eventual magnitude as well as the molecular, phenotypic, and functional properties of responding T E populations. Thus, it is the integration of signals derived from a large complex of stimulatory and inhibitory interactions that permits activated T cells the translation of minimal kinetic alterations into profound modifications of the ensuing T cell response (26,84). Insofar as these interactions produce a kinetic, quantitative, and/or qualitative enhancement of specific T cell immunity, individual components with...

CD4+ and CD8+ T cell–dependent antiviral immunity requires STIM1 and STIM2

“…Early during infection, STIM1 and STIM2 were required for the differentiation of naive CD8 + T cells into fully functional cytolytic effector cells and mediated the production of cytokines and prevented cellular exhaustion in viral-specific CD8 + effector T cells. [33][34][35][36][37][38][39][40][41] . The total numbers of NP 396-404 -and GP [33][34][35][36][37][38][39][40][41] -specific CD8 + T cells were comparable in DKO and WT mice 8 and 35 days p.i., but were moderately reduced 60 days p.i.…”

“…To understand whether recrudescence of LCMV was due to impaired viral clearance during acute infection, we analyzed the cytotoxic function of DKO CD8 + T cells. CD8 + T cells from WT and DKO P14 mice (which express a transgenic LMCV-specific TCR) were cocultured with LCMV GP [33][34][35][36][37][38][39][40][41] peptide-pulsed target cells. We observed that DKO CD8 + T cells were significantly impaired in their ability to kill target cells in vitro (Figure 2A).…”

“…We observed that DKO CD8 + T cells were significantly impaired in their ability to kill target cells in vitro (Figure 2A). Furthermore, when we isolated splenocytes from LCMV ARM -infected WT and DKO mice and stimulated them with GP [33][34][35][36][37][38][39][40][41] peptide or PMA and ionomycin in vitro, we found significantly reduced IFN-γ production in CD8 + T cells from DKO mice compared with that in WT controls ( Figure 2B). Together, these data indicate that STIM1 and STIM2 are required for antiviral effector functions of CD8 + T cells, consistent with previous reports (23,44).…”

“…adaptive immunity is the rapid expansion of the long-lived memory CD8 + T cells upon secondary infection with virus (35). This recall response is controlled by a number of factors including IL-2 secretion by CD8 + or CD4 + T cells (36,37), costimulatory signals such as CD40L (29,38), and the exhaustion of CD8 + T cells (39). Recall responses to viral reinfection result in the proliferation of memory CD8 + T cells and their differentiation into effector cells that are able to kill virus-infected cells and provide strong protective immunity.…”

“…Viral titers at day 60 p.i. correlated negatively with IFN-γ production after in vitro restimulation with LCMV GP [33][34][35][36][37][38][39][40][41] To test whether impaired memory CD8 + T cell maintenance could be due to altered expression of transcription factors that determine effector and memory fates of CD8 + T cells, we analyzed the levels of T-bet and Eomes in T eff and memory CD8 + T cell subsets of WT and DKO mice. Thirty-five and 60 days p.i., we observed that expression of T-bet was decreased and that of Eomes increased in DKO memory CD8 + T cells compared with expression levels in WT controls, resulting in a decreased T-bet/Eomes ratio ( Figure 3E), which suggests that DKO CD8 + T cells are biased toward memory cells.…”