Proliferating Transitory T Cells with an Effector-like Transcriptional Signature Emerge from PD-1+ Stem-like CD8+ T Cells during Chronic Infection.

T cell dysfunction is a characteristic feature of chronic viral infection and cancer. Recent studies in chronic lymphocytic choriomeningitis virus (LCMV) infection have defined a PD-1+ Tcf-1+ CD8+ T cell subset capable of self-renewal and differentiation into more terminally differentiated cells that downregulate Tcf-1 and express additional inhibitory molecules such as Tim3. Here, we demonstrated that expression of the glycoprotein CD101 divides this terminally differentiated population into two subsets. Stem-like Tcf-1+ CD8+ T cells initially differentiated into a transitory population of CD101-Tim3+ cells that later converted into CD101+ Tim3+ cells. Recently generated CD101-Tim3+ cells proliferated in vivo, contributed to viral control, and were marked by an effector-like transcriptional signature including expression of the chemokine receptor CX3CR1, pro-inflammatory cytokines, and granzyme B. PD-1 pathway blockade increased the numbers of CD101-Tim3+ CD8+ T cells, suggesting that these newly generated transitional cells play a critical role in PD-1-based immunotherapy.

PD-1-cis IL-2R agonism yields better effectors from stem-like CD8+ T cells.

Expansion and differentiation of antigen-experienced PD-1+TCF-1+ stem-like CD8+ T cells into effector cells is critical for the success of immunotherapies based on PD-1 blockade1-4. Hashimoto et al. have shown that, in chronic infections, administration of the cytokine interleukin (IL)-2 triggers an alternative differentiation path of stem-like T cells towards a distinct population of 'better effector' CD8+ T cells similar to those generated in an acute infection5. IL-2 binding to the IL-2 receptor α-chain (CD25) was essential in triggering this alternative differentiation path and expanding better effectors with distinct transcriptional and epigenetic profiles. However, constitutive expression of CD25 on regulatory T cells and some endothelial cells also contributes to unwanted systemic effects from IL-2 therapy. Therefore, engineered IL-2 receptor ß- and γ-chain (IL-2Rßγ)-biased agonists are currently being developed6-10. Here we show that IL-2Rßγ-biased agonists are unable to preferentially expand better effector T cells in cancer models and describe PD1-IL2v, a new immunocytokine that overcomes the need for CD25 binding by docking in cis to PD-1. Cis binding of PD1-IL2v to PD-1 and IL-2Rßγ on the same cell recovers the ability to differentiate stem-like CD8+ T cells into better effectors in the absence of CD25 binding in both chronic infection and cancer models and provides superior efficacy. By contrast, PD-1- or PD-L1-blocking antibodies alone, or their combination with clinically relevant doses of non-PD-1-targeted IL2v, cannot expand this unique subset of better effector T cells and instead lead to the accumulation of terminally differentiated, exhausted T cells. These findings provide the basis for the development of a new generation of PD-1 cis-targeted IL-2R agonists with enhanced therapeutic potential for the treatment of cancer and chronic infections.

PD-1 combination therapy with IL-2 modifies CD8+ T cell exhaustion program.

Combination therapy with PD-1 blockade and IL-2 is highly effective during chronic lymphocytic choriomeningitis virus infection1. Here we examine the underlying basis for this synergy. We show that PD-1 + IL-2 combination therapy, in contrast to PD-1 monotherapy, substantially changes the differentiation program of the PD-1+TCF1+ stem-like CD8+ T cells and results in the generation of transcriptionally and epigenetically distinct effector CD8+ T cells that resemble highly functional effector CD8+ T cells seen after an acute viral infection. The generation of these qualitatively superior CD8+ T cells that mediate viral control underlies the synergy between PD-1 and IL-2. Our results show that the PD-1+TCF1+ stem-like CD8+ T cells, also referred to as precursors of exhausted CD8+ T cells, are not fate-locked into the exhaustion program and their differentiation trajectory can be changed by IL-2 signals. These virus-specific effector CD8+ T cells emerging from the stem-like CD8+ T cells after combination therapy expressed increased levels of the high-affinity IL-2 trimeric (CD25-CD122-CD132) receptor. This was not seen after PD-1 blockade alone. Finally, we show that CD25 engagement with IL-2 has an important role in the observed synergy between IL-2 cytokine and PD-1 blockade. Either blocking CD25 with an antibody or using a mutated version of IL-2 that does not bind to CD25 but still binds to CD122 and CD132 almost completely abrogated the synergistic effects observed after PD-1 + IL-2 combination therapy. There is considerable interest in PD-1 + IL-2 combination therapy for patients with cancer2,3, and our fundamental studies defining the underlying mechanisms of how IL-2 synergizes with PD-1 blockade should inform these human translational studies.

Correlation of toxicities and efficacies of pemetrexed with clinical factors and single-nucleotide polymorphisms: a prospective observational study.

BACKGROUND: Pemetrexed is an efficacious multi-targeted antifolate with acceptable toxicity for non-squamous non-small cell lung cancer (non-Sq NSCLC) and malignant pleural mesothelioma. Vitamin B12 and folic acid as premedication can reduce the frequency of severe toxicities of pemetrexed chemotherapy. However, adverse effects are frequent in clinical settings. In this study, we aimed to identify the clinical factors and single-nucleotide polymorphisms (SNPs) associated with the toxicity and efficacy of pemetrexed chemotherapy. METHODS: This observational study was conducted from October 2012 to December 2019; we evaluated the toxicities and efficacies of pemetrexed chemotherapy using multivariate logistic or Cox regression analysis. In total, 106 patients received pemetrexed chemotherapy. SNPs were analyzed for four patients with malignant pleural mesothelioma and 67 with non-Sq NSCLC. RESULTS: The median progression-free survival (PFS) and overall survival of 63 patients with non-Sq NSCLC, excluding four in the adjuvant setting, were 6.8 and 33.3 months, respectively. Per propensity-score-adjusted multivariate Cox analyses, favorable factors for PFS were folic acid level ≥ 9.3 ng/mL before premedication, platinum combination, bevacizumab combination, vitamin B12 level < 1136 pg/mL before chemotherapy, A/A + A/G of BHMT (742 G > A), and A/A + A/C of DHFR (680 C > A). Favorable prognostic factors included good performance status, low smoking index, body mass index ≥ 20.66 kg/m2, folic acid level ≥ 5.55 ng/mL before premedication, higher retinol-binding protein before chemotherapy, and A/G of MTRR (66 A > G). Among the 71 patients who were analyzed for SNPs, the frequencies of hematologic toxicities and non-hematologic toxicities in Grades 3-4 were 38% and 36.6%, respectively. Per propensity-score-adjusted multivariate logistic analyses, risk factors for Grades 3-4 hematologic toxicities were vitamin B12 level < 486 pg/mL before premedication, leucocyte count < 6120 /µL before chemotherapy, folic acid level < 15.8 ng/mL before chemotherapy, status with a reduced dose of chemotherapy, and C/T + T/T of MTHFR (677 C > T). Risk factors for Grades 2-4 non-hematologic toxicities were homocysteine levels ≥ 11.8 nmol/mL before premedication, transthyretin level < 21.5 mg/dL before chemotherapy, C/C + T/T of MTHFR (677 C > T), and A/A + G/G of SLC19A1 [IVS2 (4935) G > A]. CONCLUSION: The information on metabolites and SNPs of the folate and methionine cycle will help predict the toxicities and efficacies of pemetrexed. TRIAL REGISTRATION: This trial was retrospectively registered with the University hospital Medical Information Network (UMIN000009366) on November 20, 2012.

A molecular basis for the control of preimmune escape variants by HIV-specific CD8+ T cells.

The capacity of the immune system to adapt to rapidly evolving viruses is a primary feature of effective immunity, yet its molecular basis is unclear. Here, we investigated protective HIV-1-specific CD8+ T cell responses directed against the immunodominant p24 Gag-derived epitope KK10 (KRWIILGLNK263-272) presented by human leukocyte antigen (HLA)-B∗2705. We found that cross-reactive CD8+ T cell clonotypes were mobilized to counter the rapid emergence of HIV-1 variants that can directly affect T cell receptor (TCR) recognition. These newly recruited clonotypes expressed TCRs that engaged wild-type and mutant KK10 antigens with similar affinities and almost identical docking modes, thereby accounting for their antiviral efficacy in HLA-B∗2705+ individuals. A protective CD8+ T cell repertoire therefore encompasses the capacity to control TCR-accessible mutations, ultimately driving the development of more complex viral escape variants that disrupt antigen presentation.

Defining CD8+ T cells that provide the proliferative burst after PD-1 therapy.

Chronic viral infections are characterized by a state of CD8+ T-cell dysfunction that is associated with expression of the programmed cell death 1 (PD-1) inhibitory receptor. A better understanding of the mechanisms that regulate CD8+ T-cell responses during chronic infection is required to improve immunotherapies that restore function in exhausted CD8+ T cells. Here we identify a population of virus-specific CD8+ T cells that proliferate after blockade of the PD-1 inhibitory pathway in mice chronically infected with lymphocytic choriomeningitis virus (LCMV). These LCMV-specific CD8+ T cells expressed the PD-1 inhibitory receptor, but also expressed several costimulatory molecules such as ICOS and CD28. This CD8+ T-cell subset was characterized by a unique gene signature that was related to that of CD4+ T follicular helper (TFH) cells, CD8+ T cell memory precursors and haematopoietic stem cell progenitors, but that was distinct from that of CD4+ TH1 cells and CD8+ terminal effectors. This CD8+ T-cell population was found only in lymphoid tissues and resided predominantly in the T-cell zones along with naive CD8+ T cells. These PD-1+CD8+ T cells resembled stem cells during chronic LCMV infection, undergoing self-renewal and also differentiating into the terminally exhausted CD8+ T cells that were present in both lymphoid and non-lymphoid tissues. The proliferative burst after PD-1 blockade came almost exclusively from this CD8+ T-cell subset. Notably, the transcription factor TCF1 had a cell-intrinsic and essential role in the generation of this CD8+ T-cell subset. These findings provide a better understanding of T-cell exhaustion and have implications in the optimization of PD-1-directed immunotherapy in chronic infections and cancer.

Prolonged SARS-CoV-2 infection associated with long-term corticosteroid use in a patient with impaired B-cell immunity.

Corticosteroids are widely used to treat severe COVID-19, but in immunocompromised individuals, who are susceptible to persistent infection, long term corticosteroid use may delay viral clearance. We present a case of prolonged SARS-CoV-2 infection in a man with significantly impaired B-cell immunity due to non-Hodgkin lymphoma which had been treated with rituximab. SARS-CoV-2 shedding persisted, despite treatment with remdesivir. Viral sequencing confirmed the persistence of the same viral strain, ruling out the possibility of reinfection. Although SARS-CoV-2 IgG, IgA and IgM remained negative throughout the treatment period, after reduction of the corticosteroid dose, PCR became negative. Long-term corticosteroid treatment, especially in immunocompromised individuals, may result in suppression of cell-mediated immunity and prolonged SARS-CoV-2 infection.

Epigenetic signature of PD-1+ TCF1+ CD8 T cells that act as resource cells during chronic viral infection and respond to PD-1 blockade.

We have recently defined a novel population of PD-1 (programmed cell death 1)+ TCF1 (T cell factor 1)+ virus-specific CD8 T cells that function as resource cells during chronic LCMV infection and provide the proliferative burst seen after PD-1 blockade. Such CD8 T cells have been found in other chronic infections and also in cancer in mice and humans. These CD8 T cells exhibit stem-like properties undergoing self-renewal and also differentiating into the terminally exhausted CD8 T cells. Here we compared the epigenetic signature of stem-like CD8 T cells with exhausted CD8 T cells. ATAC-seq analysis showed that stem-like CD8 T cells had a unique signature implicating activity of HMG (TCF) and RHD (NF-κB) transcription factor family members in contrast to higher accessibility to ETS and RUNX motifs in exhausted CD8 T cells. In addition, regulatory regions of the transcription factors Tcf7 and Id3 were more accessible in stem-like cells whereas Prdm1 and Id2 were more accessible in exhausted CD8 T cells. We also compared the epigenetic signatures of the 2 CD8 T cell subsets from chronically infected mice with effector and memory CD8 T cells generated after an acute LCMV infection. Both CD8 T cell subsets generated during chronic infection were strikingly different from CD8 T cell subsets from acute infection. Interestingly, the stem-like CD8 T cell subset from chronic infection, despite sharing key functional properties with memory CD8 T cells, had a very distinct epigenetic program. These results show that the chronic stem-like CD8 T cell program represents a specific adaptation of the T cell response to persistent antigenic stimulation.

External validation and update of prediction models for unfavorable outcomes in hospitalized patients with COVID-19 in Japan.

INTRODUCTION: Most of the currently used prognostic models for COVID-19 are based on Western cohorts, but it is unknown whether any are applicable to patients with COVID-19 in Japan. METHODS: This retrospective cohort study included 160 patients with COVID-19 who were admitted to the National Center for Global Health and Medicine between January 26, 2020 and July 25, 2020. We searched PubMed for prognostic models for COVID-19. The predicted outcome was initiation of respiratory support or death. Performance of the candidate models was evaluated according to discrimination and calibration. We recalibrated the intercept of each model with our data. We also updated each model by adding ß2-microglobulin (ß2MG) to the model and recalculating the intercept and the coefficient of ß2MG. RESULTS: Mean patient age was 49.8 years, 68% were male, 88.7% were Japanese. The study outcomes occurred in 15 patients, including two deaths. Two-hundred sixty-nine papers were screened, and four candidate prognostic models were assessed. The model of Bartoletti et al. had the highest area under receiver operating characteristic curve (AUC) (0.88; 95% confidence interval 0.81-0.96). All four models overestimated the probability of occurrence of the outcome. None of the four models showed statistically significant improvement in AUCs by adding ß2MG. CONCLUSIONS: Our results suggest that the existing prediction models for COVID-19 overestimate the probability of occurrence of unfavorable outcomes in a Japanese cohort. When applying a prediction model to a different cohort, it is desirable to evaluate its performance according to the prevalent health situation in that region.

Direct hemoperfusion using a polymyxin B-immobilized polystyrene column for COVID-19.

OBJECTIVE: To evaluate the efficacy and safety of direct hemoperfusion using a polymyxin B-immobilized polystyrene column (PMX-DHP) in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-positive pneumonia patients. METHODS: This study was a case series conducted at a designated infectious diseases hospital. Twelve SARS-CoV-2-positive patients with partial pressure of arterial oxygen/percentage of inspired oxygen (P/F) ratio < 300 were treated with PMX-DHP on two consecutive days each during hospitalization. We defined day 1 as the first day when PMX-DHP was performed. PMX-DHP efficacy was assessed on days 7 and 14 after the first treatment based on eight categories. Subsequently, improvement in P/F ratio and urinary biomarkers on days 4 and 8, malfunctions, and ventilator and extracorporeal membrane oxygenation avoidance rates were also evaluated. RESULTS: On day 14 after the first treatment, disease severity decreased in 58.3% of the patients. P/F ratio increased while urine ß2-microglobulin decreased on days 4 and 8. Cytokine measurement pre- and post-PMX-DHP revealed decreased levels of interleukin-6 and the factors involved in vascular endothelial injury, including vascular endothelial growth factor. Twenty-two PMX-DHPs were performed, of which seven and five PMX-DHPs led to increased inlet pressure and membrane coagulation, respectively. When the membranes coagulated, the circuitry needed to be reconfigured. Circuit problems were usually observed when D-dimer and fibrin degradation product levels were high before PMX-DHP. CONCLUSIONS: Future studies are expected to determine the therapeutic effect of PMX-DHP on COVID-19. Because of the relatively high risk of circuit coagulation, coagulation capacity should be assessed beforehand.

Role of PD-1 during effector CD8 T cell differentiation.

PD-1 (programmed cell death-1) is the central inhibitory receptor regulating CD8 T cell exhaustion during chronic viral infection and cancer. Interestingly, PD-1 is also expressed transiently by activated CD8 T cells during acute viral infection, but the role of PD-1 in modulating T cell effector differentiation and function is not well defined. To address this question, we examined the expression kinetics and role of PD-1 during acute lymphocytic choriomeningitis virus (LCMV) infection of mice. PD-1 was rapidly up-regulated in vivo upon activation of naive virus-specific CD8 T cells within 24 h after LCMV infection and in less than 4 h after peptide injection, well before any cell division had occurred. This rapid PD-1 expression by CD8 T cells was driven predominantly by antigen receptor signaling since infection with a LCMV strain with a mutation in the CD8 T cell epitope did not result in the increase of PD-1 on antigen-specific CD8 T cells. Blockade of the PD-1 pathway using anti-PD-L1 or anti-PD-1 antibodies during the early phase of acute LCMV infection increased mTOR signaling and granzyme B expression in virus-specific CD8 T cells and resulted in faster clearance of the infection. These results show that PD-1 plays an inhibitory role during the naive-to-effector CD8 T cell transition and that the PD-1 pathway can also be modulated at this stage of T cell differentiation. These findings have implications for developing therapeutic vaccination strategies in combination with PD-1 blockade.

CD8 T Cell Exhaustion in Chronic Infection and Cancer: Opportunities for Interventions.

Antigen-specific CD8 T cells are central to the control of chronic infections and cancer, but persistent antigen stimulation results in T cell exhaustion. Exhausted CD8 T cells have decreased effector function and proliferative capacity, partly caused by overexpression of inhibitory receptors such as programmed cell death (PD)-1. Blockade of the PD-1 pathway has opened a new therapeutic avenue for reinvigorating T cell responses, with positive outcomes especially for patients with cancer. Other strategies to restore function in exhausted CD8 T cells are currently under evaluation-many in combination with PD-1-targeted therapy. Exhausted CD8 T cells comprise heterogeneous cell populations with unique differentiation and functional states. A subset of stem cell-like PD-1+ CD8 T cells responsible for the proliferative burst after PD-1 therapy has been recently described. A greater understanding of T cell exhaustion is imperative to establish rational immunotherapeutic interventions.

Genetic diagnostic features after failure of initial treatment with epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors among non-small-cell lung cancer patients harboring EGFR mutations.

BACKGROUND: Osimertinib, a third-generation epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI), can be used as second-line treatment for lung cancer patients harboring the T790M substitution. Although osimertinib is more effective than the first-generation EGFR-TKIs used for first-line treatment, its efficacy with respect to long-term patient survival remains unclear even upon the administration of a complete sequence of EGFR-TKI therapy. Moreover, limited information is available regarding genetic diagnostic approaches after the treatment of EGFR-TKI-naïve patients. This study investigated the clinical characteristics of EGFR-mutated lung cancer patients harboring the T790M substitution resistant to EGFR-TKIs, as well as the advantages of rebiopsy and liquid biopsy for these patients. METHODS: The medical records of patients screened for EGFR mutations were reviewed. Upon failure of naïve treatment with EGFR-TKIs, except for osimertinib, single-plexus cobas version 2 was repeatedly used to detect the T790M substitution in EGFR via tissue or liquid biopsy. RESULTS: From April 2016 through May 2019, 113 patients were found to harbor EGFR mutations. Sixty patients were treated with EGFR-TKIs, among whom 46 underwent tissue or liquid biopsy. Twenty-nine of these 46 (63%) patients harbored the T790M substitution. In total, 141 rebiopsies were performed. The T790M substitution was detected in 24 of 43 tissue biopsies and 11 of 98 liquid biopsies. If patients displayed an EGFR exon 19 deletion, had a new lesion, and were administered gefitinib as first-line therapy, they were suspected to harbor the T790M substitution. Furthermore, the T790M substitution was detected through rebiopsy in patients with coexisting original mutations, brain metastases, tumor enlargement by ≥12 mm, or metastases at minor sites. CONCLUSION: Among patients with positive factors associated with the T790M mutation, repeated tissue or liquid biopsies are useful to maximize the detection rate of the T790M substitution. Furthermore, these biopsies need to be repeated numerous times in order to reduce "detection overlook" among such patients.

Adenovirus Serotype 5 Vaccination Results in Suboptimal CD4 T Helper 1 Responses in Mice.

Adenovirus serotype 5 (Ad5) is one of the most widely used viral vectors and is known to generate potent T cell responses. While many previous studies have characterized Ad5-induced CD8 T cell responses, there is a relative lack of detailed studies that have analyzed CD4 T cells elicited by Ad5 vaccination. Here, we immunized mice with Ad5 vectors encoding lymphocytic choriomeningitis virus (LCMV) glycoprotein (GP) and examined GP-specific CD4 T cell responses elicited by Ad5 vectors and compared them to those induced by an acute LCMV infection. In contrast to LCMV infection, where balanced CD4 T helper 1 (Th1) and T follicular helper (Tfh) responses were induced, Ad5 immunization resulted in a significantly reduced frequency of Th1 cells. CD4 T cells elicited by Ad5 vectors expressed decreased levels of Th1 markers, such as Tim3, SLAM, T-bet, and Ly6C, had smaller amounts of cytotoxic molecules like granzyme B, and produced less interferon gamma than CD4 T cells induced by LCMV infection. This defective CD4 Th1 response appeared to be intrinsic for Ad5 vectors and not a reflection of comparing a nonreplicating vector to a live viral infection, since immunization with a DNA vector expressing LCMV-GP generated efficient CD4 Th1 responses. Analysis at early time points (day 3 or 4) after immunization with Ad5 vectors revealed a defect in the expression of CD25 (interleukin-2 [IL-2] receptor alpha chain) on Ad5-elicited CD4 T cells, and administration of exogenous IL-2 following Ad5 immunization partially restored CD4 Th1 responses. These results suggest that impairment of Th1 commitment after Ad5 immunization could be due to reduced IL-2-mediated signaling.IMPORTANCE During viral infection, generating balanced responses of Th1 and Tfh cells is important to induce effective cell-mediated responses and provide optimal help for antibody responses. In this study, to investigate vaccine-induced CD4 T cell responses, we characterized CD4 T cells after immunization with Ad5 vectors expressing LCMV-GP in mice. Ad5 vectors led to altered effector differentiation of LCMV GP-specific CD4 T cells compared to that during LCMV infection. CD4 T cells following Ad5 immunization exhibited impaired Th1 lineage commitment, generating significantly decreased Th1 responses than those induced by LCMV infection. Our results suggest that suboptimal IL-2 signaling possibly plays a role in reduced Th1 development following Ad5 immunization.

Sensitivity and specificity of QuantiFERON-TB Gold Plus compared with QuantiFERON-TB Gold In-Tube and T-SPOT.TB on active tuberculosis in Japan.

BACKGROUND: The QuantiFERON-TB Gold Plus (QFT-Plus) was introduced in 2015 as a new generation of interferon-gamma release assays (IGRAs) designed to detect Mycobacterium tuberculosis infection (TB). Examination of its diagnostic accuracy is crucial before it is launched in Japan. METHOD: We examined 99 patients with laboratory-confirmed active TB (patients) and 117 healthy volunteers with no risk of TB infection (controls) at a medical center in Tokyo, Japan. Blood samples were collected from both the patients and controls and tested using three types of IGRAs: the QFT-Plus, the QuantiFERON-TB Gold In-Tube (QFT-GIT), and the T-SPOT.TB (T-SPOT). The sensitivity and specificity of each IGRA were examined and compared. RESULTS: The sensitivity of the QFT-Plus was 98.9% (95% confidence interval [CI], 0.934-0.998) and similar to that of the QFT-GIT (97.9%; 95% CI, 0.929-0.998) and T-SPOT (96.9%; 95% CI, 0.914-0.994). The specificity of the QFT-Plus was the same as that of the QFT-GIT and T-SPOT (98.1%; 95% CI, 0.934-0.998). One patient with uncontrolled diabetes mellitus showed negative results on all three IGRAs. CONCLUSIONS: The QFT-Plus showed a high degree of agreement with the QFT-GIT and T-SPOT, with high sensitivity and specificity. Severe diabetes mellitus may influence the results of IGRAs. Larger studies are needed to validate the accuracy of the GFT-Plus and determine whether it can contribute as adjunctive method for the early diagnosis of active TB in Japan.

Fine-tuning of CD8(+) T-cell effector functions by targeting the 2B4-CD48 interaction.

Polyfunctionality and cytotoxic activity dictate CD8(+) T-cell efficacy in the eradication of infected and malignant cells. The induction of these effector functions depends on the specific interaction between the T-cell receptor (TCR) and its cognate peptide-MHC class I complex, in addition to signals provided by co-stimulatory or co-inhibitory receptors, which can further regulate these functions. Among these receptors, the role of 2B4 is contested, as it has been described as either co-stimulatory or co-inhibitory in modulating T-cell functions. We therefore combined functional, transcriptional and epigenetic approaches to further characterize the impact of disrupting the interaction of 2B4 with its ligand CD48, on the activity of human effector CD8(+) T-cell clones. In this setting, we show that the 2B4-CD48 axis is involved in the fine-tuning of CD8(+) T-cell effector function upon antigenic stimulation. Blocking this interaction resulted in reduced CD8(+) T-cell clone-mediated cytolytic activity, together with a subtle drop in the expression of genes involved in effector function regulation. Our results also imply a variable contribution of the 2B4-CD48 interaction to the modulation of CD8(+) T-cell functional properties, potentially linked to intrinsic levels of T-bet expression and TCR avidity. The present study thus provides further insights into the role of the 2B4-CD48 interaction in the fine regulation of CD8(+) T-cell effector function upon antigenic stimulation.

Host-specific adaptation of HIV-1 subtype B in the Japanese population.

UNLABELLED: The extent to which HIV-1 clade B strains exhibit population-specific adaptations to host HLA alleles remains incompletely known, in part due to incomplete characterization of HLA-associated HIV-1 polymorphisms (HLA-APs) in different global populations. Moreover, it remains unknown to what extent the same HLA alleles may drive significantly different escape pathways across populations. As the Japanese population exhibits distinctive HLA class I allele distributions, comparative analysis of HLA-APs between HIV-1 clade B-infected Japanese and non-Asian cohorts could shed light on these questions. However, HLA-APs remain incompletely mapped in Japan. In a cohort of 430 treatment-naive Japanese with chronic HIV-1 clade B infection, we identified 284 HLA-APs in Gag, Pol, and Nef using phylogenetically corrected methods. The number of HLA-associated substitutions in Pol, notably those restricted by HLA-B*52:01, was weakly inversely correlated with the plasma viral load (pVL), suggesting that the transmission and persistence of B*52:01-driven Pol mutations could modulate the pVL. Differential selection of HLA-APs between HLA subtype members, including those differing only with respect to substitutions outside the peptide-binding groove, was observed, meriting further investigation as to their mechanisms of selection. Notably, two-thirds of HLA-APs identified in Japan had not been reported in previous studies of predominantly Caucasian cohorts and were attributable to HLA alleles unique to, or enriched in, Japan. We also identified 71 cases where the same HLA allele drove significantly different escape pathways in Japan versus predominantly Caucasian cohorts. Our results underscore the distinct global evolution of HIV-1 clade B as a result of host population-specific cellular immune pressures. IMPORTANCE: Cytotoxic T lymphocyte (CTL) escape mutations in HIV-1 are broadly predictable based on the HLA class I alleles expressed by the host. Because HLA allele distributions differ among worldwide populations, the pattern and diversity of HLA-associated escape mutations are likely to be somewhat distinct to each race and region. HLA-associated polymorphisms (HLA-APs) in HIV-1 have previously been identified at the population level in European, North American, Australian, and African cohorts; however, large-scale analyses of HIV-1 clade B-specific HLA-APs in Asians are lacking. Differential intraclade HIV-1 adaptation to global populations can be investigated via comparative analyses of HLA-associated polymorphisms across ethnic groups, but such studies are rare. Here, we identify HLA-APs in a large Japanese HIV-1 clade B cohort using phylogenetically informed methods and observe that the majority of them had not been previously characterized in predominantly Caucasian populations. The results highlight HIV's unique adaptation to cellular immune pressures imposed by different global populations.

Harnessing CD8 T cell responses using PD-1-IL-2 combination therapy.

There is considerable interest in developing more effective programmed cell death (PD)-1 combination therapies against cancer. One major obstacle to these efforts is a dysfunctional/exhausted state of CD8 T cells, which PD-1 monotherapy is not able to overcome. Recent studies have highlighted that PD-1+ T cell factor (TCF)-1+ stem-like CD8 T cells are not fate locked into the exhaustion program and their differentiation trajectory can be changed by interleukin (IL)-2 signals. Modifying the CD8 T cell exhaustion program and generating better effectors from stem-like CD8 T cells by IL-2 form the fundamental immunological basis for combining IL-2 with PD-1 therapy. Many versions of IL-2-based products are being tested and each product should be carefully evaluated for its ability to modulate dysfunctional states of anti-tumor CD8 T cells.

Relapse of COVID-19 and Viral Evolution in a Patient With Good Syndrome: A Case Report.

Delays in clearance and rapid evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been reported in immunocompromised patients. We encountered a case of recurrent, multi-mutational SARS-CoV-2 infection in a 40-year-old man with severe immunodeficiency due to Good syndrome. The patient had not received the SARS-CoV-2 vaccination. In August 2021, he was first admitted to the hospital owing to coronavirus disease 2019 (COVID-19) pneumonia and was administered dexamethasone, remdesivir, and baricitinib. Although his fever and respiratory condition improved once, chest computed tomography (CT) revealed extensive diffuse consolidation and ground-glass opacities (GGOs), and both methylprednisolone pulse therapy and tocilizumab yielded a limited effect. After a third course of remdesivir without immunosuppressants or steroids, the patient recovered, and he tested negative for SARS-CoV-2. On day 272 since the clinical onset, he was readmitted with dyspnea and mild fever due to a COVID-19 recurrence. He was infected with the Delta variant (AY.29), despite the Omicron (BA.2) variant being predominant at that time. During this admission, additional remdesivir and casirivimab/imdevimab yielded marked effects, and the SARS-CoV-2 quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) tests rapidly returned negative. Phylogenetic analysis demonstrated the accumulation of mutations, including those yielding remdesivir resistance, throughout the SARS-CoV-2 genome. Appropriate use of antivirals and monoclonal antibodies may aid in the recovery of patients with COVID-19 and immunodeficiency and in preventing the emergence of multi-mutational SARS-CoV-2 variants.

Early generation of a precursor CD8 T cell that can adapt to acute or chronic viral infection.

Virus specific PD-1+ TCF-1+ TOX+ stem-like CD8+ T cells are essential for maintaining T cell responses during chronic infection and are also critical for PD-1 directed immunotherapy. In this study we have used the mouse model of chronic LCMV infection to examine when these virus specific stem-like CD8+ T cells are generated during the course of chronic infection and what is the role of antigen in maintaining the stem-like program. We found that these stem-like CD8+ T cells are generated early (day 5) during chronic infection and that antigen is essential for maintaining their stem-like program. This early generation of stem-like CD8+ T cells suggested that the fate commitment to this cell population was agnostic to the eventual outcome of infection and the immune system prepares a priori for a potential chronic infection. Indeed, we found that an identical virus specific stem-cell like CD8+ T cell population was also generated during acute LCMV infection but these cells were lost once the virus was cleared. To determine the fate of these early PD-1+TCF-1+TOX+ stem-like CD8+ T cells that are generated during both acute and chronic LCMV infection we set up two reciprocal adoptive transfer experiments. In the first experiment we transferred day 5 stem-like CD8+ T cells from chronically infected into acutely infected mice and examined their differentiation after viral clearance. We found that these early stem-like CD8+ T cells downregulated canonical markers of the chronic stem-like CD8+ T cells and expressed markers (CD127 and CD62L) associated with central memory CD8+ T cells. In the second experiment, we transferred day 5 stem-like cells from acutely infected mice into chronically infected mice and found that these CD8+ T cells could function like resource cells after transfer into a chronic environment by generating effector CD8+ T cells in both lymphoid and non-lymphoid tissues while also maintaining the number of stem-like CD8+ T cells. These findings provide insight into the generation and maintenance of virus specific stem-like CD8+ T cells that play a critical role in chronic viral infection. In particular, our study highlights the early generation of stem-like CD8+ T cells and their ability to adapt to either an acute or chronic infection. These findings are of broad significance since these novel stem-like CD8+ T cells play an important role in not only viral infections but also in cancer and autoimmunity.