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Marginal zone (MZ) B cells are innate-like B cells that not only rapidly secrete antibodies (Abs) against blood-borne pathogens but also serve Ab-independent functions such as antigen presentation and immune regulation, which may reflect their heterogeneity. Here, we discovered a subpopulation of MZ B cells that expressed higher levels of CD80, but not CD86, in naïve mice. CD80high MZ B cells revealed higher Ab-producing, proliferative, and IL-10-secreting capacities than CD80low MZ B cells. Notably, the CD80high MZ B cells survived 2 Gy whole-body irradiation, whereas CD80low MZ B cells were preferentially depleted by the irradiation and repleted in a month after the irradiation. The CD80high MZ B cells expressed higher levels of genes involved in proliferation, plasma cell differentiation, antioxidant response, and immune regulation. The CD80high MZ B cells contained autoreactive BCRs reactive to double-stranded DNA or type II collagen. Next-generation sequencing revealed more immunoglobulin heavy chains with a shorter complementarity-determining region 3 and no N-nucleotides in the CD80high MZ B cells than in CD80low MZ B cells. In summary, MZ B cells can be divided into two populations differing in CD80 expression, Ab-productive capacity, radioresistance, and B cell receptor repertoire, which may have different homeostatic functions.

T cells are important in tumour immunity but a better understanding is needed of the differentiation of antigen-specific T cells in human cancer1,2. Here we studied CD8 T cells in patients with human papillomavirus (HPV)-positive head and neck cancer and identified several epitopes derived from HPV E2, E5 and E6 proteins that allowed us to analyse virus-specific CD8 T cells using major histocompatibility complex (MHC) class I tetramers. HPV-specific CD8 T cells expressed PD-1 and were detectable in the tumour at levels that ranged from 0.1% to 10% of tumour-infiltrating CD8 T lymphocytes (TILs) for a given epitope. Single-cell RNA-sequencing analyses of tetramer-sorted HPV-specific PD-1+ CD8 TILs revealed three transcriptionally distinct subsets. One subset expressed TCF7 and other genes associated with PD-1+ stem-like CD8 T cells that are critical for maintaining T cell responses in conditions of antigen persistence. The second subset expressed more effector molecules, representing a transitory cell population, and the third subset was characterized by a terminally differentiated gene signature. T cell receptor clonotypes were shared between the three subsets and pseudotime analysis suggested a hypothetical differentiation trajectory from stem-like to transitory to terminally differentiated cells. More notably, HPV-specific PD-1+TCF-1+ stem-like TILs proliferated and differentiated into more effector-like cells after in vitro stimulation with the cognate HPV peptide, whereas the more terminally differentiated cells did not proliferate. The presence of functional HPV-specific PD-1+TCF-1+CD45RO+ stem-like CD8 T cells with proliferative capacity shows that the cellular machinery to respond to PD-1 blockade exists in HPV-positive head and neck cancer, supporting the further investigation of PD-1 targeted therapies in this malignancy. Furthermore, HPV therapeutic vaccination efforts have focused on E6 and E7 proteins; our results suggest that E2 and E5 should also be considered for inclusion as vaccine antigens to elicit tumour-reactive CD8 T cell responses of maximal breadth. An analysis of human papillomavirus (HPV)-specific CD8 T cells in patients with head and neck cancer identifies functional PD-1+TCF-1+CD8 T cells in the tumour with implications for therapeutic vaccination and PD-1 directed immunotherapy.

The migratory patterns of virus-specific CD8 T cells during chronic viral infection are not well understood. To address this issue, we have done parabiosis experiments during chronic lymphocytic choriomeningitis virus (LCMV) infection of mice. We found that despite the high frequency of virus-specific CD8 T cells in both lymphoid and nonlymphoid tissues there was minimal migration of virus-specific CD8 T cells between the chronically infected conjoined parabiont mice. This was in contrast to parabionts between mice that had undergone an acute LCMV infection where virus-specific CD8 T cells established equilibrium demonstrating circulation of memory T cells generated after viral clearance. We have identified a population of PD-1+ TCF1+CXCR5+Tim-3- stemlike virus-specific CD8 T cells that reside in lymphoid tissues and act as resource cells for maintaining the T cell response during chronic infection. These are the cells that proliferate and give rise to the more terminally differentiated PD-1+ CXCR5-Tim-3+ CD8 T cells. Both the stemlike CD8 T cells and their terminally differentiated progeny showed minimal migration during chronic infection and the few LCMV-specific CD8 T cells that were present in circulation were the recently emerging progeny from the stemlike CD8 T cells. The PD-1+ TCF1+CXCR5+ stemlike CD8 T cells were truly resident in lymphoid tissues and did not circulate in the blood. We propose that this residency in specialized niches within lymphoid tissues is a key aspect of their biology and is essential for maintaining their quiescence and stemlike program under conditions of a chronic viral infection.

Significance PD-1+ TCF1+ stem-like CD8 T cells are critical for maintaining the T cell response during chronic viral infection and cancer, and provide the proliferative burst seen after PD-1 immunotherapy. These cells undergo a slow self-renewal and also give rise to the more terminally differentiated and exhausted CD8 T cells. Here we define the epigenetic landscape of the stem-like CD8 T cells and their more differentiated progeny. These 2 CD8 T cell subsets from chronically infected mice showed substantial differences, but also shared common features that were distinct from the epigenetic signature of effector and memory CD8 T cells generated after an acute viral infection. This information will be useful in targeting epigenetic changes to improve current immunotherapies., 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.

Combination therapy with PD-1 blockade and IL-2 is highly effective during chronic lymphocytic choriomeningitis virus infection(1). Here we examine the underlying basis for this synergy. We show that PD-1 + IL-2 combination therapy, unlike PD-1 monotherapy, dramatically changes the differentiation program of the PD-1(+)TCF-1(+) 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(+)TCF-1(+) 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 plays 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 CD25 but still binds CD122/CD132 almost completely abrogated the synergistic effects seen after PD-1 + IL-2 combination therapy. There is currently considerable interest in PD-1 + IL-2 combination therapy for patients with cancer(2,3) and our fundamental studies defining the underlying mechanisms of how IL-2 synergizes with PD-1 blockade should inform these human translational studies.

Recent studies on chronic viral infections have defined a novel programmed cell death 1-positive (PD-1(+)) T cell factor 1-positive (TCF1(+)) stem-like CD8 T cell subset that gives rise to the terminally differentiated exhausted CD8 T cells. In this study, we performed T cell receptor beta (TCRβ) sequencing of virus-specific CD8 T cells during chronic lymphocytic choriomeningitis virus (LCMV) infection to examine the TCR diversity and lineage relationship of these two functionally distinct subsets. We found that >95% of the TCR repertoire of the exhausted CD8 T cell subset was shared with the stem-like CD8 T cells. The TCR repertoires of both CD8 T cell subsets were composed mostly of a few dominant clonotypes, but there was slightly more breadth and diversity in the stem-like CD8 T cells than their exhausted counterpart (∼40 versus ∼15 GP33(+) clonotypes; ∼20 versus ∼7 GP276(+) clonotypes). Interestingly, the breadth of the TCR repertoire was broader during the early stages (day 8) of the chronic infection than the later stages (days 45 to 60), showing that there was a narrowing of the TCR repertoire during chronic infection (∼2-fold GP33(+) and GP276(+) stem-like subset; ∼10-fold GP33(+) and ∼5-fold GP276(+) exhausted subset). In contrast, during acute LCMV infection, the TCR repertoire was much broader in both GP33-specific effector (∼160 clonotypes) and memory CD8 T cells (∼160 clonotypes). Overall, our data demonstrate that the virus-specific CD8 T cell TCR repertoire is broad and remains stable after acute LCMV infection, but it contracts and is narrower during chronic infection. Our study also shows that the repertoire of the exhausted CD8 T cell subset is almost completely derived from the stem-like CD8 T cell subset during established chronic LCMV infection. IMPORTANCE CD8 TCR repertoires responding to chronic viral infections (HIV, hepatitis C virus [HCV], Epstein-Barr virus [EBV], and cytomegalovirus [CMV]) have limited breadth and diversity. How these repertoires change and are maintained throughout the chronic infection are unknown. We thus characterized the LCMV-specific CD8 TCR repertoires of stem-like and terminally exhausted subsets generated during chronic LCMV infections. During chronic LCMV infections, the repertoires started as diverse but became more clonal at the late time point. Further, the exhausted subset was composed of dominant clonotypes that were shared with the stem-like subset. Together, we demonstrate that the TCR repertoire contracts over time and is almost exclusively derived from the stem-like subset late during the persistent viral infection. Our data suggest that dominant clonotypes in the exhausted subset are derived from a diverse pool of stem-like clonotypes, which may be contributing to the clonality observed during chronic viral infections.

Acute viral infection or vaccination generates highly functional memory CD8 T cells following the Ag resolution. In contrast, persistent antigenic stimulation in chronic viral infection and cancer leads to a state of T-cell dysfunction termed T-cell exhaustion. We and other have recently identified a novel subset of exhausted CD8 T cells that act as stem cells for maintaining virus-specific CD8 T cells in a mouse model of chronic lymphocytic choriomeningitis virus infection. This stem cell-like CD8 T-cell subset has been also observed in both mouse and human tumor models. Most importantly, in both chronic viral infection and tumor models, the proliferative burst of Ag-specific CD8 T cells driven by PD-1-directed immunotherapy comes exclusively from this stem cell-like CD8 T-cell subset. Therefore, a better understanding of the mechanisms how CD8 T-cell subsets are regulated during chronic viral infection and cancer is required to improve the current immunotherapies that restore the function of exhausted CD8 T cells. In this review, we discuss the differentiation of virus-specific CD8 T cells during chronic viral infection, the characteristics and function of CD8 T-cell subsets, and the therapeutic intervention of PD-1-directed immunotherapy in cancer.

Tumour-infiltrating lymphocytes are associated with a survival benefit in several tumour types and with the response to immunotherapy1–8. However, the reason some tumours have high CD8 T cell infiltration while others do not remains unclear. Here we investigate the requirements for maintaining a CD8 T cell response against human cancer. We find that CD8 T cells within tumours consist of distinct populations of terminally differentiated and stem-like cells. On proliferation, stem-like CD8 T cells give rise to more terminally differentiated, effector-molecule-expressing daughter cells. For many T cells to infiltrate the tumour, it is critical that this effector differentiation process occur. In addition, we show that these stem-like T cells reside in dense antigen-presenting-cell niches within the tumour, and that tumours that fail to form these structures are not extensively infiltrated by T cells. Patients with progressive disease lack these immune niches, suggesting that niche breakdown may be a key mechanism of immune escape. The authors examine the immune cell infiltrates of human tumours and provide evidence for a population of CD8 T cells with stem-cell characteristics and proliferative capacity that reside in an antigen-presenting niche within tumours.

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.

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.

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.

The common γ-chain cytokines, interleukin (IL)-2, IL-7, and IL-15, regulate critical aspects of antiviral CD8 T-cell responses. During acute infections, IL-2 controls expansion and differentiation of antiviral CD8 T cells, whereas IL-7 and IL-15 are key cytokines to maintain memory CD8 T cells long term in an antigen-independent manner. On the other hand, during chronic infections, in which T-cell exhaustion is established, precise roles of these cytokines in regulation of antiviral CD8 T-cell responses are not well defined. Nonetheless, administration of IL-2, IL-7, or IL-15 can increase function of exhausted CD8 T cells, and thus can be an attractive therapeutic approach. A new subset of stem-cell-like CD8 T cells, which provides a proliferative burst after programmed cell death (PD)-1 therapy, has been recently described during chronic viral infection. Further understanding of cytokine-mediated regulation of this CD8 T-cell subset will improve cytokine therapies to treat chronic infections and cancer in combination with immune checkpoint inhibitors.

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.

T follicular helper (Tfh) cells are specialized providers of cognate B cell help, which is important in promoting the induction of high-affinity antibody production in germinal centers (GCs). Interleukin-6 (IL-6) and IL-21 have been known to play important roles in Tfh cell differentiation. Here, we demonstrate that IL-7 plays a pivotal role in Tfh generation and GC formation in vivo , as treatment with anti-IL-7 neutralizing antibody markedly impaired the development of Tfh cells and IgG responses. Moreover, codelivery of mouse Fc-fused IL-7 (IL-7-mFc) with a vaccine enhanced the generation of GC B cells as well as Tfh cells but not other lineages of T helper cells, including Th1, Th2, and Th17 cells. Interestingly, a 6-fold-lower dose of an influenza virus vaccine codelivered with Fc-fused IL-7 induced higher antigen-specific and cross-reactive IgG titers than the vaccine alone in both mice and monkeys and led to markedly enhanced protection against heterologous influenza virus challenge in mice. Enhanced generation of Tfh cells by IL-7-mFc treatment was not significantly affected by the neutralization of IL-6 and IL-21, indicating an independent role of IL-7 on Tfh differentiation. Thus, IL-7 holds promise as a critical cytokine for selectively inducing Tfh cell generation and enhancing protective IgG responses. IMPORTANCE Here, we demonstrate for the first time that codelivery of Fc-fused IL-7 significantly increased influenza virus vaccine-induced antibody responses, accompanied by robust expansion of Tfh cells and GC B cells as well as enhanced GC formation. Furthermore, IL-7-mFc induced earlier and cross-reactive IgG responses, leading to striking protection against heterologous influenza virus challenge. These results suggest that Fc-fused IL-7 could be used for inducing strong and cross-protective humoral immunity against highly mutable viruses, such as HIV and hepatitis C virus, as well as influenza viruses.

Background & Aims Here, we evaluated the safety and immunogenicity of hepatitis B virus (HBV) DNA vaccine, HB-110, in mice and Korean patients with chronic hepatitis B (CHB) undergoing adefovir dipivoxil (ADV) treatment. Methods For animal study, mice (BALB/c or HBV transgenic) were immunized with mHB-110, and T-cell and antibody responses were evaluated. For clinical study, 27 patients randomly received either ADV alone or ADV in combination with HB-110. Liver function tests, serum HBV DNA levels and the presence of HBeAg/anti-HBe were analysed. T-cell responses were estimated by ELISPOT and FACS analysis. Results mHB-110 induced higher T-cell and antibody responses than mHB-100 in mice. No adverse effects were observed by HB-110 cotreated with ADV. HBV-specific T-cell responses were induced in a portion of patients in medium to high dose of HB-110. Interestingly, HB-110 exhibited positive effects on ALT normalization and maintenance of HBeAg seroconversion. One patient, who received high dose of HB-110 exhibited HBeAg seroconversion during vaccination, which correlated with vaccine-induced T-cell responses without ALT elevation. Conclusions HB-110 was safe and tolerable in CHB patients. In contrast to results in animal models, HB-110 in Korean patients exhibited weaker capability of inducing HBV-specific T-cell responses and HBeAg seroconversion than HB-100 in Caucasian patients. As Asian patients, who are generally infected via vertical transmission, appeared to have higher level of immune tolerance than Caucasian, novel approaches for breaking immune tolerance rather than enhancing immunogenicity may be more urgently demanded to develop effective therapeutic HBV DNA vaccines.

Chemokines have been known to play an important role in eliciting adaptive immune responses by, selectively attracting the innate cellular components to the site of antigen presentation. In this study, we demonstrated that all three CXCR3 ligands, CXCL9, CXCL10, and CXCL11, could act as a strong, genetic adjuvant. Among them, CXCL11 increased vaccine antigen-specific CD8 T cells, including, several cytokine secretions (IFN-γ and TNF-α) to a greater degree than the other two CXCR3 ligands. Fc-fusion of CXCL11 (CXCL11-Fc) induced similar but slightly higher CD8 T cell response, which, appeared to be antigen- (ovalbumin (OVA) vs. human papillomavirus 16 (HPV16) E7) and vaccine, type- (adenovirus vs. DNA vaccine) independent. In addition, the adjuvant effect of CXCL11-Fc was, further confirmed by suppressing tumor growth and extension of survival rates in a therapeutic tumor, model, which was correlated with enhanced antigen-specific CD8 T cell responses. Interestingly, the, enhanced antigen-specific CD8 T cell responses by co-delivery of CXCL11-Fc were associated with CD8, T cell proliferation, followed by increased total and effector memory T cell frequencies. Taken together, our findings provide a novel role of CXCL11 as a strong genetic adjuvant which might be used to, increase antigen-specific CD8 T cell immunity elicited by vaccination.

Interleukin-7 (IL-7) is essential to T-cell survival as well as homeostatic proliferation, and clinical trials that exploit the mitogenic effects of IL-7 have achieved success in treating human diseases. In mice, the in vivo potency of IL-7 improves dramatically when it is administered as a complex with the anti-IL-7 neutralizing monoclonal antibody clone M25. However, the mechanism whereby M25 augments IL-7 potency is unknown. We have analyzed the discrete contributions of the antibody constant (Fc) and IL-7-binding (Fab) domains to the mechanism. By engaging the neonatal Fc receptor the Fc domain extends the in vivo lifespan of IL-7/M25 complexes and accounts for the majority of their activity. Unexpectedly, the IL-7-neutralizing Fab domain provides an additional, albeit smaller, contribution, possibly by serving as a cytokine depot. This study is the first to demonstrate that the neutralizing aspect of the monoclonal antibody is directly involved in enhancing the potency of a cytokine with a single form of receptor. Lessons from the mechanism of IL-7/M25 complexes inform the design of next-generation cytokine therapeutics.

Background We previously reported that IFN-γ producing T cell responses induced by the combined therapy of DNA vaccine and lamivudine for one year are important for the induction of sustained virological response (SVR). However, IFN-γ production is not sufficient to predict sustained viremia control in chronic hepatitis B (CHB) carriers treated. Methods Twelve CHB carriers were intramuscularly immunized 12 times at a 4-week interval with 8 mg of HBV DNA vaccine during the standard lamivudine treatment (100 mg/daily/1 year). The level of cytokines during and after the combined therapy in plasma of all 12 CHB carriers treated was determined by each ELISA kit. Six out of 12 CHB carriers revisited the clinic, and their HBV DNA levels were examined. Results The combined therapy increased plasma IL-12 and IL-12/p40 ratio during the treatment (baseline vs. peak level: 41.8±8.3 vs. 163.1±29.2 pg/ml; p

Most influenza vaccines target hemagglutinin (HA) in order to protect the host against infection. However, theses vaccines are strain-specific due to major antigenic variations of HA. Since it is difficult to predict epidemic and pandemic strains of influenza virus, the development of effective vaccines against divergent influenza viruses is urgently needed. Although M2e-based vaccines are associated with weaker protection than HA-based vaccines that induce neutralizing antibodies against challenge virus matched-strain, the extracellular domain of Matrix 2 protein (M2e) is one of a potential broad-spectrum immunogen because it contains highly conserved sequences among influenza A viruses. In this study, M2e sequence was fused to H1N1 HA DNA (M2e-HA) and the immunogenicity and antiviral efficacy of this DNA vaccine was evaluated in response to challenge with a heterosubtypic H5N2 avian influenza virus. Compared to vaccination with HA or M2e DNA alone, vaccination with M2e-HA DNA or combination of M2e DNA and HA DNA (M2e DNA+HA DNA) induced a broad immunity without evidence of immune interference. In addition, HA-specific CD8(+) and M2e-specific T cell responses elicited by M2e-HA DNA vaccination were significantly higher than those of HA or M2e DNA vaccine alone, respectively. Following challenge with a heterosubtypic influenza virus infection, vaccination with M2e-HA DNA conferred complete protection against mortality. In combination, these results suggest that DNA vaccines expressing a fusion protein, M2e-HA, may provide an attractive approach for the development of broad-spectrum influenza vaccines.

Pulse-induced permeabilization of cellular membranes, generally referred to as electroporation (EP), has been used for years as a tool to increase macromolecule uptake in tissues, including nucleic acids, for gene therapeutic applications, and this technique has been shown to result in improved immunogenicity. In this study, we assessed the utility of EP as a tool to improve the efficacy of HB-110, a novel therapeutic DNA vaccine against chronic hepatitis B, now in phase 1 of clinical study in South Korea. The potency of HB-110 in mice was shown to be improved by EP. The rapid onset of antigen expression and higher magnitude of humoral and cellular responses in electric pulse-treated mice revealed that EP may enable a substantial reduction in the dosage of DNA vaccine required to elicit a response similar in magnitude to that achievable via conventional administration. This study also showed that EP-based vaccination at 4-week-intervals elicited a cellular immune response which was about two-fold higher than the response elicited by conventional vaccination at 2-week intervals. These results may provide a rationale to reduce the clinical dose and increase the interval between the doses in the multidose vaccination schedule. Electric pulsing also elicited a more balanced immune response against four antigens expressed by HB-110: S, preS, Core, and Pol.

This study investigated the pharmacokinetic profile and biodistribution of HB-110, a novel HBV therapeutic vaccine candidate, in mice. HB-110 was rapidly degraded in the blood after i.v. injection with a half-life of 1.9+/-0.083 min, and was no longer detected at 60 min except in one individual near the detection limit. In the i.m. injection, plasmid DNA was detectable at the injection site until 11 days after administration, but the amounts were just above the detection limit. The blood concentration of HB-110 showed a maximum of 604 pg/mL at 15 min after i.m. injection, which was followed by degradation to undetectable levels at 90 min. The plasmid DNA in tissues peaked at 90 min after administration. The highest concentration of plasmid DNA was detected in the liver (24.172 pg/mg tissue), and considerable amounts were also observed in the lung (9.467 pg/mg tissue) and spleen (7.688 pg/mg tissue). The amount of plasmid DNA in tissues was 2 to 3 orders of magnitude lower than in the injection site at the same time points. The HB-110 concentration in tissues, including gonads, decreased rapidly and was undetectable 24 h after administration.

Hepatitis B virus (HBV) currently infects more than 400 million people worldwide and they are at risk of developing chronic liver disease, cirrhosis and hepatocellular carcinoma. The immune response to HBV-encoded antigens is responsible both for viral clearance and for disease pathogenesis during HBV infection. While the humoral antibody response to viral envelope antigens contributes to the clearance of circulating virus particles, the cellular immune responses to the envelope, nucleocapsid, and polymerase antigens were known to eliminate virus in infected hepatocytes through cytolytic as well as noncytolytic mechanisms. Liver injury could be initiated by an immune response against HBV, but mainly resulted from HBV non-specific lymphocytes and macrophages. There are growing evidences that T helper 1 memory T cells play a predominant role in suppressing viral replication mainly by IFN-gamma through noncytolytic antiviral mechanism. Elucidation of the immunological and virological basis for HBV infection may yield effective immunotherapeutic and antiviral strategies to terminate chronic HBV infection.

Background A crucial limitation of DNA vaccines is its weak immunogenicity, especially in terms of eliciting antibody responses in non-human primates or humans; therefore, it is essential to enhance immune responses to vaccination for the development of successful DNA vaccines for humans. Methods Here, we approached this issue by evaluating interleukin-7 (IL-7) as a genetic adjuvant in cynomolgus monkeys immunized with multigenic HCV DNA vaccine. Results Codelivery of human IL-7 (hIL-7)-encoding DNA appeared to increase DNA vaccine-induced antibody responses specific for HCV E2 protein, which plays a critical role in protecting from HCV infection. HCV-specific T cell responses were also significantly enhanced by codelivery of hIL-7 DNA. Interestingly, the augmentation of T cell responses by codelivery of hIL-7 DNA was shown to be due to the enhancement of both the breadth and magnitude of immune responses against dominant and subdominant epitopes. Conclusion Taken together, these findings suggest that the hIL-7-expressing plasmid serves as a promising vaccine adjuvant capable of eliciting enhanced vaccine-induced antibody and broad T cell responses.