Elite controllers (ECs) are a rare group of HIV seropositive individuals who are able to control viral replication without antiretroviral therapy. The mechanisms responsible for this phenotype, however, have not been fully elucidated. In this study, we examined CD4؉ T cell resistance to HIV in a cohort of elite controllers and explored transcriptional signatures associated with cellular resistance. We demonstrate that a subgroup of elite controllers possess CD4 ؉ T cells that are specifically resistant to R5-tropic HIV while remaining fully susceptible to X4-tropic and vesicular stomatitis virus G (VSV-G)-pseudotyped viruses. Transcriptome analysis revealed 17 genes that were differentially regulated in resistant elite controllers relative to healthy controls. Notably, the genes encoding macrophage inflammatory protein 1␣ (MIP-1␣), CCL3 and CCL3L1, were found to be upregulated. The MIP-1␣, MIP-1␤, and RANTES chemokines are natural ligands of CCR5 and are known to interfere with HIV replication. For three elite controllers, we observed increased production of MIP-1␣ and/or MIP-1␤ at the protein level. The supernatant from resistant EC cells contained MIP-1␣ and MIP-1␤ and was sufficient to confer R5-tropic resistance to susceptible CD4 ؉ T cells. Additionally, this effect was reversed by using inhibitory anti-MIP antibodies. These results suggest that the T cells of these particular elite controllers may be naturally resistant to HIV infection by blocking R5-tropic viral entry. IMPORTANCEHIV is a pandemic health problem, and the majority of seropositive individuals will eventually progress to AIDS unless antiretroviral therapy (ART) is administered. However, rare patients, termed elite controllers, have a natural ability to control HIV infection in the absence of ART, but the mechanisms by which they achieve this phenotype have not been fully explored. This paper identifies one mechanism that may contribute to this natural resistance: some elite controllers have CD4 ؉ T cells that produce high levels of MIP chemokines, which block R5-tropic HIV entry. This mechanism could potentially be exploited to achieve a therapeutic effect in other HIV-seropositive individuals. In the absence of antiretroviral therapy (ART), the majority of HIV-seropositive patients have detectable viral loads (VLs) and experience a slow but inevitable decline in the number of CD4 ϩ T cells, eventually culminating in the development of AIDS. However, in rare individuals (Ͻ1% of the HIV-seropositive population), viral replication is suppressed to extremely low or undetectable levels. These patients, termed elite controllers (ECs), typically retain relatively high CD4 ϩ T cell counts and do not progress to AIDS, even in the absence of ART (1-4). Sequencing of HIV and in vitro functional assays suggest that most ECs possess replicationcompetent virus (5). Long-term nonprogressors (LTNPs), representing ϳ2 to 15% of HIV-seropositive patients, are a second group of individuals with a protective phenotype, in whom the virus continues to rep...

Circadian rhythms coordinate an organism's activities and biological processes to the optimal time in the 24-h daylight cycle. We previously demonstrated that male C57BL/6 mice develop sepsis more rapidly when the disease is induced in the nighttime versus the daytime. In this report, we elucidate the mechanism of this diurnal difference. Sepsis was induced via cecal ligation and puncture (CLP) at zeitgeber time (ZT)-19 (2 am) or ZT-7 (2 pm). Like the males used in our prior study, female C57BL/6 mice had a worse outcome when CLP was induced at ZT-19 versus ZT-7, and these effects persisted when we pooled the data from both sexes. In contrast, mice with a mutated () gene had a similar outcome when CLP was induced at ZT-19 versus ZT-7. Bone marrow chimeras reconstituted with C57BL/6 immune cells exhibited a worse outcome when sepsis was induced at ZT-19 versus ZT-7, whereas chimeras with -mutated immune cells did not. Next, murine macrophages were subjected to serum shock to synchronize circadian rhythms and exposed to bacteria cultured from the mouse cecum at 4-h intervals for 48 h. We observed that IL-6 production oscillated with a 24-h period in C57BL/6 cells exposed to cecal bacteria. Interestingly, we observed a similar pattern when cells were exposed to the TLR2 agonist lipoteichoic acid. Furthermore, TLR2-knockout mice exhibited a similar sepsis phenotype when CLP was induced at ZT-19 versus ZT-7. Together, these data suggest that circadian rhythms in immune cells mediate diurnal variations in murine sepsis severity via a TLR2-dependent mechanism.

IFN regulatory factor 3 (IRF3) is a transcription factor that is activated by multiple pattern-recognition receptors. We demonstrated previously that IRF3 plays a detrimental role in a severe mouse model of sepsis, induced by cecal ligation and puncture. In this study, we found that IRF3-knockout (KO) mice were greatly protected from sepsis in a clinically relevant version of the cecal ligation and puncture model incorporating crystalloid fluids and antibiotics, exhibiting improved survival, reduced disease score, lower levels of serum cytokines, and improved phagocytic function relative to wild-type (WT) mice. Computational modeling revealed that the overall complexity of the systemic inflammatory/immune network was similar in IRF3-KO versus WT septic mice, although the tempo of connectivity differed. Furthermore, the mediators driving the network differed: TNF-a, IL-1b, and IL-6 predominated in WT mice, whereas MCP-1 and IL-6 predominated in IRF3-KO mice. Network analysis also suggested differential IL-6-related inflammatory programs in WT versus IRF3-KO mice. We created bone marrow chimeras to test the role of IRF3 within leukocytes versus stroma. Surprisingly, chimeras with IRF3-KO bone marrow showed little protection from sepsis, whereas chimeras with IRF3-KO stroma showed a substantial degree of protection. We found that WT and IRF3-KO macrophages had a similar capacity to produce IL-6 and phagocytose bacteria in vitro. Adoptive transfer experiments demonstrated that the genotype of the host environment affected the capacity of monocytes to produce IL-6 during sepsis. Thus, IRF3 acts principally within the stromal compartment to exacerbate sepsis pathogenesis via differential impacts on IL-6-related inflammatory programs.

Interferon regulatory factor 3 is a transcription factor that induces type 1 interferons and related inflammatory genes following activation of pattern recognition receptors. Our prior report demonstrates that IRF3-KO mice are substantially protected from sepsis in a lethal mouse model of cecal ligation and puncture (CLP). Here, we demonstrate that IRF3 remains relevant in the context of a CLP model incorporating clinical treatments (lactated ringer’s solution and antibiotics). 92.3% of IRF3-KO mice survived sepsis in this model, compared to 61.5% of wild-type mice. Septic IRF3-KO mice also had an improved disease score and lower levels of serum cytokines (IL-6 and IL-12), relative to wild-type counterparts. To examine if IRF3 exerts its effect within leukocytes, we generated bone marrow chimeras. We found that chimeras with IRF3-KO leukocytes did not exhibit a significant survival advantage over chimeras with wild-type leukocytes. However, chimeras with IRF3-KO stroma exhibited substantially improved survival relative to chimeras with wild-type stroma, paired with lower disease score and serum cytokines (IL-6 and IL-12). In vitro experiments with thioglycollate-elicited macrophages from IRF3-KO and wild-type mice demonstrate that IRF3 does not directly reduce the amount of IL-6 produced in response to cecal bacteria. However, wild-type monocytes that are adoptively transferred into septic hosts produce less IL-6 when the host is IRF3-KO vs wild-type. These experiments reveal the surprising finding that IRF3 exerts its major effect on sepsis pathogenesis through its presence in stromal cells, with indirect effects on leukocytes.