Prevention of CD8 T Cell Deletion during Chronic Viral Infection

During chronic viral infections, CD8 T cells rapidly lose antiviral and immune-stimulatory functions in a sustained program termed exhaustion. In addition to this loss of function, CD8 T cells with the highest affinity for viral antigen can be physically deleted. Consequently, treatments designed to restore function to exhausted cells and control chronic viral replication are limited from the onset by the decreased breadth of the antiviral T cell response. Yet, it remains unclear why certain populations of CD8 T cells are deleted while others are preserved in an exhausted state. We report that CD8 T cell deletion during chronic viral infection can be prevented by therapeutically lowering viral replication early after infection. The initial resistance to deletion enabled long-term maintenance of antiviral cytolytic activity of the otherwise deleted high-affinity CD8 T cells. In combination with decreased virus titers, CD4 T cell help and prolonged interactions with costimulatory molecules B7-1/B7-2 were required to prevent CD8 T cell deletion. Thus, therapeutic strategies to decrease early virus replication could enhance virus-specific CD8 T cell diversity and function during chronic infection.

NR4A1 Deletion in Marginal Zone B Cells Exacerbates Atherosclerosis in Mice—Brief Report

Objective: NR4A orphan receptors have been well studied in vascular and myeloid cells where they play important roles in the regulation of inflammation in atherosclerosis. NR4A1 (nerve growth factor IB) is among the most highly induced transcription factors in B cells following BCR (B-cell receptor) stimulation. Given that B cells substantially contribute to the development of atherosclerosis, we examined whether NR4A1 regulates B-cell function during atherogenesis. Approach and Results: We found that feeding Ldlr −/− mice a Western diet substantially increased Nr4a1 expression in marginal zone B (MZB) cells compared with follicular B cells. We then generated Ldlr −/− mice with complete B- or specific MZB-cell deletion of Nr4a1 . Complete B-cell deletion of Nr4a1 led to increased atherosclerosis, which was accompanied by increased T follicular helper cell–germinal center axis response, as well as increased serum total cholesterol and triglycerides levels. Interestingly, specific MZB-cell deletion of Nr4a1 increased atherosclerosis in association with an increased T follicular helper–germinal center response but without any impact on serum cholesterol or triglyceride levels. Nr4a1 −/− MZB cells showed decreased PDL1 (programmed death ligand-1) expression, which may have contributed to the enhanced T follicular helper response. Conclusions: Our findings reveal a previously unsuspected role for NR4A1 in the atheroprotective role of MZB cells.

Abstract MP42: T Cell Deletion Normalizes Sex Differences Of Blood Pressure But Not Renal Damage In Dahl Salt-sensitive Rats

The immune system has a clear role in the development of hypertension and renal damage in male Dahl salt-sensitive (SS) rats, but far less is known about this phenotype in females, especially in regard to the contribution of immune-related mechanisms. The current study examined the hypertensive and kidney injury phenotype in response to a 3 week high salt challenge (HS, 4.0% NaCl, AIN-76A) in female versus male SS rats (n>10/group). Measured via radiotelemetry, there was no difference in low salt (LS, 0.4% NaCl) mean arterial pressure (MAP) between females and males (129±2 vs 124±2 mmHg, respectively). However, after 3 weeks of HS, females had a significant attenuation in the development of hypertension compared to males (161±3 vs 177±7 mmHg). This coincided with significantly less renal damage, evident by markedly reduced albuminuria (105±16 vs 183±16 mg/day) and medullary protein cast formation (7.0±0.7 vs 14.6±1.1%) in the females. Assessed via flow cytometry, there were fewer CD45+ total leukocytes (48% reduction), CD3+ T cells (51%), CD45R+ B cells (73%), and CD11b/c+ monocytes/macrophages (47%) in female versus male kidneys. To interrogate the contribution of adaptive immunity, specifically T cells, to the development of this sex difference, the same parameters were investigated in female and male SS CD247-/- rats which lack CD3+ T cells. The absence of functional T cells significantly reduced blood pressure in both females (147±6 vs 161±3 mmHg; SS CD247-/- vs SS) and males (157±8 vs 177±7 mmHg) after 3 weeks of HS, with no statistical difference between female and male SS CD247-/- rats. While a reduction in albuminuria (females: 37±12 vs 105±16 mg/day; males: 88±13 vs 183±16 mg/day, SS CD247-/- vs SS) and medullary protein cast formation (females: 1.8±0.4 vs 7.0±0.7%; males: 9.1±0.7 vs 14.6±1.1%) was observed in SS CD247-/- versus SS rats regardless of sex, there was greater protection from these measures of kidney damage in SS CD247-/- female versus SS CD247-/- males. Together, our data indicate that female SS rats are significantly protected from high salt-induced hypertension and renal disease compared to males rats. The deletion of T cells normalized high salt blood pressure between male and female rats but sex differences in renal damage still persisted.