Antigen-specific T-cell-mediated immunity after HIV-1 infection: implications for vaccine control of HIV development

Controlled human infectious models, a path forward in uncovering immunological correlates of protection: Lessons from enteric fevers studies

Enteric infectious diseases account for more than a billion disease episodes yearly worldwide resulting in approximately 2 million deaths, with children under 5 years old and the elderly being disproportionally affected. Enteric pathogens comprise viruses, parasites, and bacteria; the latter including pathogens such as Salmonella [typhoidal (TS) and non-typhoidal (nTS)], cholera, Shigella and multiple pathotypes of Escherichia coli (E. coli). In addition, multi-drug resistant and extensively drug-resistant (XDR) strains (e.g., S. Typhi H58 strain) of enteric bacteria are emerging; thus, renewed efforts to tackle enteric diseases are required. Many of these entero-pathogens could be controlled by oral or parenteral vaccines; however, development of new, effective vaccines has been hampered by lack of known immunological correlates of protection (CoP) and limited knowledge of the factors contributing to protective responses. To fully comprehend the human response to enteric infections, an invaluable tool that has recently re-emerged is the use of controlled human infection models (CHIMs) in which participants are challenged with virulent wild-type (wt) organisms. CHIMs have the potential to uncover immune mechanisms and identify CoP to enteric pathogens, as well as to evaluate the efficacy of therapeutics and vaccines in humans. CHIMs have been used to provide invaluable insights in the pathogenesis, host-pathogen interaction and evaluation of vaccines. Recently, several Oxford typhoid CHIM studies have been performed to assess the role of multiple cell types (B cells, CD8+ T, Tregs, MAIT, Monocytes and DC) during S. Typhi infection. One of the key messages that emerged from these studies is that baseline antigen-specific responses are important in that they can correlate with clinical outcomes. Additionally, volunteers who develop typhoid disease (TD) exhibit higher levels and more activated cell types (e.g., DC and monocytes) which are nevertheless defective in discrete signaling pathways. Future critical aspects of this research will involve the study of immune responses to enteric infections at the site of entry, i.e., the intestinal mucosa. This review will describe our current knowledge of immunity to enteric fevers caused byS. Typhi and S. Paratyphi A, with emphasis on the contributions of CHIMs to uncover the complex immunological responses to these organisms and provide insights into the determinants of protective immunity.

Th2-Biased Transcriptional Profile Predicts HIV Envelope-Specific Polyfunctional CD4+ T Cells That Correlated with Reduced Risk of Infection in RV144 Trial

Ag-specific T cells play a critical role in responding to viral infections. In the RV144 HIV vaccine clinical trial, a rare subset of HIV-specific polyfunctional CD4⁺ T cells correlated with reduced risk of HIV-1 infection. Polyfunctional T cells are a subset of Ag-specific T cells that are able to simultaneously produce multiple effector cytokines. Little is known about what differentiates polyfunctional T cells from other vaccine-elicited T cells in humans. Therefore, we developed a novel live-cell multiplexed cytokine capture assay to identify, isolate, and transcriptionally profile vaccine-specific polyfunctional CD4⁺ T cells. We applied these methods to samples from subjects who received the RV144 vaccine regimen, as part of the HVTN 097 clinical trial. We identified two surface receptors (CD44 and CD82) upregulated on polyfunctional T cells and a Th2-biased transcriptional signature (IL-4, IL-5, and IL-13) that predicted the envelope-specific polyfunctional CD4⁺ T cell profiles that had correlated with reduced risk of HIV infection in RV144. By linking single-cell transcriptional and functional profiles, we may be able to further define the potential contributions of polyfunctional T cells to effective vaccine-elicited immunity.

The Cellular Localization of Human Cytomegalovirus Glycoprotein Expression Greatly Influences the Frequency and Functional Phenotype of Specific CD4+ T Cell Responses

CMV infection is a significant cause of morbidity and mortality in immunocompromised individuals, and the development of a vaccine is of high priority. Glycoprotein B (gB) is a leading vaccine candidate but the glycoprotein H (gH) pentameric complex is now recognized as the major target for neutralizing Abs. However, little is known about the T cell immune response against gH and glycoprotein L (gL) and this is likely to be an important attribute for vaccine immunogenicity. In this study, we examine and contrast the magnitude and phenotype of the T cell immune response against gB, gH, and gL within healthy donors. gB-specific CD4(+) T cells were found in 95% of donors, and 29 epitopes were defined with gB-specific response sizes ranging from 0.02 to 2.88% of the CD4(+) T cell pool. In contrast, only 20% of donors exhibited a T cell response against gH or gL. Additionally, gB-specific CD4(+) T cells exhibited a more cytotoxic phenotype, with high levels of granzyme B expression. Glycoproteins were effectively presented following delivery to APCs but only gB-derived epitopes were presented following endogenous synthesis. gB expression was observed exclusively within vesicular structures colocalizing with HLA-DM whereas gH was distributed evenly throughout the cytoplasm. Grafting of the C-terminal domain from gB onto gH could not transfer this pattern of presentation. These results reveal that gB is a uniquely immunogenic CMV glycoprotein and this is likely to reflect its unique pattern of endogenous Ag presentation. Consideration may be required toward mechanisms that boost cellular immunity to gH and gL within future subunit vaccines.

Small alveolar macrophages are infected preferentially by HIV and exhibit impaired phagocytic function

HIV-1-infected persons are at higher risk of lower respiratory tract infections than HIV-1-uninfected individuals. This suggests strongly that HIV-infected persons have specific impairment of pulmonary immune responses, but current understanding of how HIV alters pulmonary immunity is incomplete. Alveolar macrophages (AMs), comprising small and large macrophages, are major effectors of innate immunity in the lung. We postulated that HIV-1 impairs pulmonary innate immunity through impairment of AM physiological functions. AMs were obtained by bronchoalveolar lavage from healthy, asymptomatic, antiretroviral therapy-naive HIV-1-infected and HIV-1-uninfected adults. We used novel assays to detect in vivo HIV-infected AMs and to assess AM functions based on the HIV infection status of individual cells. We show that HIV has differential effects on key AM physiological functions, whereby small AMs are infected preferentially by the virus, resulting in selective impairment of phagocytic function. In contrast, HIV has a more generalized effect on AM proteolysis, which does not require direct viral infection. These findings provide new insights into how HIV alters pulmonary innate immunity and the phenotype of AMs that harbors the virus. They underscore the need to clear this HIV reservoir to improve pulmonary immunity and reduce the high incidence of lower respiratory tract infections in HIV-1-infected individuals.

Functional proteome of macrophage carried nanoformulated antiretroviral therapy demonstrates enhanced particle carrying capacity

Our laboratory developed long-acting nanoformulations of antiretroviral therapy (nanoART) to improve drug compliance, reduce toxicities, and facilitate access of drug to viral reservoirs. These all function to inevitably improve treatment of human immunodeficiency virus (HIV) infection. Formulations are designed to harness the carrying capacities of mononuclear phagocytes (MP; monocytes and macrophages) and to use these cells as Trojan horses for drug delivery. Such a drug distribution system limits ART metabolism and excretion while facilitating access to viral reservoirs. Our prior works demonstrated a high degree of nanoART sequestration in macrophage recycling endosomes with broad and sustained drug tissue biodistribution and depots with limited untoward systemic toxicities. Despite such benefits, the effects of particle carriage on the cells' functional capacities remained poorly understood. Thus, we employed pulsed stable isotope labeling of amino acids in cell culture to elucidate the macrophage proteome and assess any alterations in cellular functions that would affect cell-drug carriage and release kinetics. NanoART-MP interactions resulted in the induction of a broad range of activation-related proteins that can enhance phagocytosis, secretory functions, and cell migration. Notably, we now demonstrate that particle-cell interactions serve to enhance drug loading while facilitating drug tissue depots and transportation.

Biology of plasmacytoid dendritic cells and natural killer cells in HIV-1 infection

PURPOSE

This review summarizes recent literature on the biology of dendritic cells and natural killer cells in HIV-1 infection and the importance of crosstalk between them in the development of strong antiviral immunity.

RECENT FINDINGS

Type I interferons produced by dendritic cells in response to HIV-1 have been suggested to act as a double-edged sword, stemming HIV-1 replication on the one hand and causing T-cell loss on the other. Recent epidemiologic evidence demonstrates a strong association between the natural killer cell receptor KIR3DS1 (along with its presumed ligand HLA-B Bw4-80I) in the control of HIV-1 replication.

SUMMARY

Dendritic and natural killer cells play a central role in the innate immune response to viral infections through both the direct elimination of infected cells and modulation of each other's function.

Cyclosporin A and tacrolimus reduce T-cell polyfunctionality but not interferon-γ responses directed at cytomegalovirus

Cytomegalovirus (CMV) -specific immunity is often estimated by the number of in vitro CMV antigen-inducible interferon-γ-positive (IFN-γ(+) ) T cells. However, recent work indicates that simultaneous production of IFN-γ, tumour necrosis factor-α (TNF-α) and interleukin-2 (IL-2) (referred to as 'polyfunctionality') is more relevant for anti-viral protection. Here, we compared polyfunctionality of CMV-specific T cells (pp65 and IE-1 proteins) in 23 solid-organ transplant patients and seven healthy controls by flow cytometry. The proportions of TNF-α(+) /IFN-γ(+) /IL-2 cells among the activated cells were significantly reduced in transplant patients but not the frequencies of IFN-γ(+) CD8(+) T cells. Immunosuppression reduces polyfunctionality, which reflects the increased infection risk in this patient group.

Interleukin-12p70 expression by dendritic cells of HIV-1-infected patients fails to stimulate gag-specific immune responses

A variety of immune-based therapies has been developed in order to boost or induce protective CD8⁺ T cell responses in order to control HIV replication. Since dendritic cells (DCs) are professional antigen-presenting cells (APCs) with the unique capability to stimulate naïve T cells into effector T cells, their use for the induction of HIV-specific immune responses has been studied intensively. In the present study we investigated whether modulation of the activation state of DCs electroporated with consensus codon-optimized HxB2 gag mRNA enhances their capacity to induce HIV gag-specific T cell responses. To this end, mature DCs were (i) co-electroporated with mRNA encoding interleukin (IL)-12p70 mRNA, or (ii) activated with a cytokine cocktail consisting of R848 and interferon (IFN)-γ. Our results confirm the ability of HxB2 gag-expressing DCs to expand functional HIV-specific CD8⁺ T cells. However, although most of the patients had detectable gag-specific CD8⁺ T cell responses, no significant differences in the level of expansion of functional CD8⁺ T cells could be demonstrated when comparing conventional or immune-modulated DCs expressing IL-12p70. This result which goes against expectation may lead to a re-evaluation of the need for IL-12 expression by DCs in order to improve T-cell responses in HIV-1-infected individuals.

Insights into human CD8(+) T-cell memory using the yellow fever and smallpox vaccines

Live virus vaccines provide a unique opportunity to study human CD8(+) T-cell memory in the context of a controlled, primary acute viral infection. Yellow fever virus-17D and Dryvax are two such live-virus vaccines that are highly efficacious, used worldwide and provide long-term immunity against yellow fever and smallpox respectively. In this review, we describe the properties of virus-specific memory CD8(+) T cells generated in smallpox and yellow fever vaccinees. We address fundamental questions regarding magnitude, functional quality and longevity of the CD8(+) T-cell response, which are otherwise challenging to address in humans. These findings provide insights into the attributes of the human immune system as well as provide a benchmark for the optimal quality of a CD8(+) T-cell response that can be used to evaluate novel candidate vaccines.

CD8 T-Cell Responses before and after Structured Treatment Interruption in Ugandan Adults Who Initiated ART with CD4 T Cells <200 Cell/μL: The DART Trial STI Substudy

Objective. To better understand attributes of ART-associated HIV-induced T-cell responses that might be therapeutically harnessed. Methods. CD8(+) T-cell responses were evaluated in some HIV-1 chronically infected participants of the fixed duration STI substudy of the DART trial. Magnitudes, breadths, and functionality of IFN-γ and Perforin responses were compared in STI (n = 42) and continuous treatment (CT) (n = 46) before and after a single STI cycle when the DART STI trial was stopped early due to inferior clinical outcome in STI participants. Results. STI and CT had comparable magnitudes and breadths of monofunctional CD8(+)IFNγ(+) and CD8(+)Perforin(+) responses. However, STI was associated with significant decline in breadth of bi-functional (CD8(+)IFNγ(+)Perforin(+)) responses; P = .02, Mann-Whitney test. Conclusions. STI in individuals initiated onto ART at <200 CD4(+) T-cell counts/μl significantly reduced occurrence of bifunctional CD8(+)IFNγ(+)/Perforin(+) responses. These data add to others that found no evidence to support STI as a strategy to improve HIV-specific immunity during ART.

Immunotherapy coming of age: what will it take to make it standard of care for glioblastoma?

With the recent approval by the FDA of an immunotherapy for prostate cancer and another positive immunotherapy trial in melanoma, immunotherapy may finally be coming of age. So what will it take for it to become part of the standard treatment for glioblastoma? To put this question into perspective, we summarize critical background information in neuro-immunology, address immunotherapy clinical trial design, and discuss a number of extrinsic factors that will impact the development of immunotherapy in neuro-oncology.

Principles of vaccine design-Lessons from nature

Microbial pathogens have developed complex and efficient ways of counteracting and evading innate and adaptive immune mechanisms. The strategies used by pathogens determine strongly the type of immune response a vaccine should elicit and how the vaccine should be formulated. Improved knowledge of immune response mechanisms has brought successes in the development of vaccines that protect against challenging pathogens as well as vaccines that can be used in immunocompromised and elderly populations. This includes the production of highly purified antigens that provide a better reactogenicity and safety profile than some of the early whole-pathogen vaccines. Successful attempts to improve antigen purity, however, can result in weakened immunogenicity. The search for approaches to overcome this has led to new technologies, such as live vector vaccines, DNA vaccines and novel adjuvant formulations, which have been based on growing knowledge of the interplay between innate and adaptive immune systems and the central role played by antigen-presenting cells. Of these technologies, one of the most promising to date is based on the use of innovative adjuvants combined with careful antigen selection. Vaccine design has therefore become more tailored, and in turn has opened up the potential of extending its application in immunotherapies to tackle diseases such as cancer, Alzheimer disease and immune-mediated disorders.

Natural killer cells that respond to human immunodeficiency virus type 1 (HIV‐1) peptides are associated with control of HIV‐1 infection

Human immunodeficiency virus (HIV)-specific natural killer (CD3- cells), CD4, and CD8 T cellular responses were determined in 79 HIV‐1-infected women in response to HIV‐1 peptide pools (Gag, Pol, Nef, Reg, and Env) with use of a whole‐blood intracellular cytokine staining assay that measures interferon-γ and/or interleukin-2. HIV‐specific CD3- cell responses to any region (Env and Reg predominantly targeted) were associated with lower viral load (P = .031) and higher CD4 T cell count (P = .015). Env‐specific CD3- cell responses were stronger in women who had both Gag CD4 and CD8 T cell responses and, in turn, was associated with lower viral load (P = .005). CD3- cell responders had significantly higher representation of CD4 T cell responses to Env and Reg (P = .012 and P = .015, respectively) and higher magnitudes of CD4 T cell responses (P = .017 and P = .037, respectively) than did nonresponders. Peptide‐specific natural killer cells are associated with markers of less severe disease progression among HIV‐1-infected women (lower viral load and higher CD4 T cell count) and with stronger HIV‐specific T cell responses.

Complement as an endogenous adjuvant for dendritic cell-mediated induction of retrovirus-specific CTLs

Previous studies have demonstrated the involvement of complement (C) in induction of efficient CTL responses against different viral infections, but the exact role of complement in this process has not been determined. We now show that C opsonization of retroviral particles enhances the ability of dendritic cells (DCs) to induce CTL responses both in vitro and in vivo. DCs exposed to C-opsonized HIV in vitro were able to stimulate CTLs to elicit antiviral activity significantly better than non-opsonized HIV. Furthermore, experiments using the Friend virus (FV) mouse model illustrated that the enhancing role of complement on DC-mediated CTL induction also occurred in vivo. Our results indicate that complement serves as natural adjuvant for DC-induced expansion and differentiation of specific CTLs against retroviruses.

Immune escape mutations detected within HIV-1 epitopes associated with viral control during treatment interruption

We analyzed immune responses in chronically HIV-infected individuals who took part in a treatment interruption (TI) trial designed for patients who initiated antiretroviral therapy within 6 months of seroconversion. In the 2 subjects who exhibited the best viral control, we detected CD8(+) T-cell responses against 1-2 Gag epitopes during the early weeks of TI and a subsequent increase in the number of epitopes recognized by the later time points. Each of these subjects developed mutations within the epitopes targeted by the highest magnitude responses. In the subject with the worst viral control, we detected responses against 2 Gag epitopes throughout the entire TI and no Gag mutations. The magnitude of these responses increased dramatically with time, greatly exceeding those detected in the virologic controllers. The highest levels of contemporaneous autologous neutralizing antibody activity were detected in the virologic controllers, and a subsequent escape mutation developed within the envelope gene of one controller that abrogated the response. These data suggest that immune escape mutations are a sign of viral control during TI, and that the absence of immune escape mutations in the presence of high levels of viral replication indicates the lack of an effective host immune response.

AAV-1-mediated gene transfer to skeletal muscle in humans results in dose-dependent activation of capsid-specific T cells

In a clinical trial for adeno-associated virus serotype 1 (AAV-1)-mediated gene transfer to muscle for lipoprotein lipase (LPL) deficiency, 1 subject from the high-dose cohort experienced a transient increase in the muscle enzyme creatine phosphokinase (CPK) 4 weeks after gene transfer. Simultaneously, after an initial downward trend consistent with expression of LPL, plasma triglyceride levels returned to baseline. We characterized B- and T-cell responses to the vector and the transgene product in the subjects enrolled in this study. IFN-gamma enzyme-linked immunosorbent spot (ELISpot) and intracellular cytokine staining assays performed on peripheral blood mononuclear cells (PBMCs) from the subject who experienced the CPK elevation showed the activation of capsid-specific CD4(+) and CD8(+) T cells. Four of 8 subjects had detectable T-cell responses to capsid with dose-dependent kinetics of appearance. Subjects with detectable T-cell responses to capsid also had higher anti-AAV-1 IgG3 antibody titer. No subject developed B- or T-cell responses to the LPL transgene product. These findings suggest that T-cell responses directed to the AAV-1 capsid are dose-dependent. Whether they also limit the duration of expression of the transgene at higher doses is unclear, and will require additional analyses at later time points.

Gamma/Delta T cell mRNA levels decrease at mucosal sites and increase at lymphoid sites following an oral SIV infection of macaques

The oral and esophageal mucosa have been identified as possible sites of HIV/SIV entry following oral infection. Here, gamma/delta (gammadelta) T cells, a multi-functional T cell subset, were assessed at oral/esophageal mucosa and lymphoid sites at the earliest times (1-14 days) post-oral SIV inoculation utilizing quantitative RT-PCR. During these earliest times post-infection, decreased gammadelta TCR mRNA levels were observed at the oral gingiva and esophageal mucosa, while increased levels were observed within regional lymph nodes (cervical and retropharyngeal). Higher lymph node gammadelta TCR levels were associated with increased mRNA expression of the lymphoid homing chemokine/receptor (CCL21/CCR7) pair in these lymph nodes. In contrast to gammadelta TCR levels, CD4 mRNA expression remained relatively stable through 4 days post-infection, and depletion of CD4 T cells was only evident after 7 or 14 days post-infection. The decrease of gammadelta T cell mRNA from mucosal sites and the corresponding increase at lymphoid sites suggest a rapid redistribution of these immune cells at these earliest times post-SIV infection.

Activation of a dendritic cell-T cell axis by Ad5 immune complexes creates an improved environment for replication of HIV in T cells

The STEP HIV vaccine trial, which evaluated a replication-defective adenovirus type 5 (Ad5) vector vaccine, was recently stopped. The reasons for this included lack of efficacy of the vaccine and a twofold increase in the incidence of HIV acquisition among vaccinated recipients with increased Ad5-neutralizing antibody titers compared with placebo recipients. To model the events that might be occurring in vivo, the effect on dendritic cells (DCs) of Ad5 vector alone or treated with neutralizing antiserum (Ad5 immune complexes [IC]) was compared. Ad5 IC induced more notable DC maturation, as indicated by increased CD86 expression, decreased endocytosis, and production of tumor necrosis factor and type I interferons. We found that DC stimulation by Ad5 IC was mediated by the Fcgamma receptor IIa and Toll-like receptor 9 interactions. DCs treated with Ad5 IC also induced significantly higher stimulation of Ad5-specific CD8 T cells equipped with cytolytic machinery. In contrast to Ad5 vectors alone, Ad5 IC caused significantly enhanced HIV infection in DC-T cell cocultures. The present results indicate that Ad5 IC activates a DC-T cell axis that, together with the possible persistence of the Ad5 vaccine in seropositive individuals, may set up a permissive environment for HIV-1 infection, which could account for the increased acquisition of HIV-1 infection among Ad5 seropositive vaccine recipients.

Scientific consultation on cell mediated immunity (CMI) in dengue and dengue vaccine development

Dengue is a re-emerging arboviral disease of great public health importance. Limited understanding of protective immune responses against dengue has hampered advancement of dengue vaccine candidates. Demonstrating an immunological correlate of protection has been limited to associating quantitative neutralizing antibody titers with clinical outcomes following infection. There have been a number of studies investigating the role of cell mediated immunity (CMI) in natural infections and these have demonstrated roles in both virus clearance and potentiating disease. Vaccine developers have extended the exploratory study of CMI in natural infection to the study of dengue vaccine recipients. Primary infections and monovalent vaccine administration generates dengue type-specific T-cell responses. Secondary infection, vaccination of flavivirus primed individuals, or administration of multivalent vaccine candidates results in broad, cross-reactive T-cell responses, similar to the broadening of antibody patterns. However, the precise function of CMI in protection or disease pathology remains ill-defined and, at present, there is no evidence to suggest that CMI can be utilized as a correlate of protection. Nonetheless, the study of CMI in natural infection and following vaccine administration should continue in an attempt to improve the understanding of dengue immunopathology, vaccine candidate immunogenicity, and potential correlates of protection.

Priming of a novel subset of CD28+ rapidly expanding high-avidity effector memory CTL by post maturation electroporation-CD40L dendritic cells is IL-12 dependent

Dendritic cell (DC)-based immunotherapeutics must induce robust CTL capable of killing tumor or virally infected cells in vivo. In this study, we show that RNA electroporated post maturation and coelectroporated with CD40L mRNA (post maturation electroporation (PME)-CD40L DC) generate high-avidity CTL in vitro that lyse naturally processed and presented tumor Ag. Unlike cytokine mixture-matured DC which induce predominantly nonproliferative effector memory CD45RA(+) CTL, PME-CD40L DC prime a novel subset of Ag-specific CTL that can be expanded to large numbers upon sequential DC stimulation in vitro. We have defined these cells as rapidly expanding high-avidity (REHA) CTL based on: 1) the maintenance of CD28 expression, 2) production of high levels of IFN-gamma and IL-2 in response to Ag, and 3) the demonstration of high-avidity TCR that exhibit strong cytolytic activity toward limiting amounts of native Ag. We demonstrate that induction of REHA CTL is dependent at least in part on the production of IL-12. Interestingly, neutralization of IL-12 did not effect cytolytic activity of REHA CTL when Ag is not limiting, but did result in lower TCR avidity of Ag-reactive CTL. These results suggest that PME-CD40L DC are uniquely capable of delivering the complex array of signals needed to generate stable CD28(+) REHA CTL, which if generated in vivo may have significant clinical benefit for the treatment of infectious disease and cancer.

Tumor-specific immunotherapy targeting the EGFRvIII mutation in patients with malignant glioma

Conventional therapies for malignant gliomas (MGs) fail to target tumor cells exclusively, such that their efficacy is ultimately limited by non-specific toxicity. Immunologic targeting of tumor-specific gene mutations, however, may allow more precise eradication of neoplastic cells. The epidermal growth factor receptor variant III (EGFRvIII) is a consistent tumor-specific mutation that is widely expressed in MGs and other neoplasms. This mutation encodes a constitutively active tyrosine kinase that enhances tumorgenicity and migration and confers radiation and chemotherapeutic resistance. This in-frame deletion mutation splits a codon resulting in the creation of a novel glycine at the fusion junction between normally distant parts of the molecule and producing a sequence re-arrangement which creates a tumor-specific epitope for cellular or humoral immunotherapy in patients with MGs. We have previously shown that vaccination with a peptide that spans the EGFRvIII fusion junction is an efficacious immunotherapy in syngeneic murine models, but patients with MGs have a profound immunosuppression that may inhibit the ability of antigen presenting cells (APCs), even those generated ex vivo, to induce EGFRvIII-specific immune responses. In this report, we summarize our results in humans targeting this mutation in two consecutive and one multi-institutional Phase II immunotherapy trials. These trials demonstrated that vaccines targeting EGFRvIII are capable of inducing potent T- and B-cell immunity in these patients, and lead to an unexpectedly long survival time. Most importantly, vaccines targeting EGFRvIII were universally successful at eliminating tumor cells expressing the targeted antigen without any evidence of symptomatic collateral toxicity. These studies establish the tumor-specific EGFRvIII mutation as a novel target for humoral- and cell-mediated immunotherapy in a variety of cancers. The recurrence of EGFRvIII-negative tumors in our patients, however, highlights the need for targeting a broader repertoire of tumor-specific antigens.

HIV rebound after discontinuation of antiretroviral therapy increases and expands HIV-specific CD8+ responses but has no impact on its functionality

A higher functionality of CD8(+) T cells might contribute to low-level HIV replication in long-term nonprogressors (LTNPs). However, the contrary could also be true, being the function of CD8(+) T cells modulated by HIV replication. We tested whether enhanced HIV replication following antiretroviral therapy interruption could modify the functional profile of HIV-specific CD8(+) responses. Production of MIP-1beta, IL-2, TNF-alpha, and CD107 expression by CD8(+) T cells in response to Gag and Nef optimal peptide pools was analyzed using polychromatic flow cytometry in nine HIV-infected individuals followed for 12 months after discontinuation of antiretroviral therapy. At baseline, CD8(+) T cell subsets with the greatest contribution to response were MIP-beta(+)TNF-alpha(-)IL-2(-)CD107(+) and MIP-beta(+)TNF-alpha(-)IL-2(-)CD107. Most responses were mediated by subsets expressing only one or two molecules. After 12 months of discontinuing antiretroviral therapy, no significant differences were observed in the functional profile of Gag- and Nef-specific CD8(+) responses. However, viral rebound induced a significant increase in the heterogeneity of Gag-specific CD8(+) responses. In summary, viral replication following discontinuation of antiretroviral therapy has no significant impact on qualitative aspects of HIV-specific CD8(+) responses. Thus, a higher functionality of CD8(+) responses does not seem to be the consequence of low-level virus replication.

Suppression of viral replication with highly active antiretroviral therapy has no impact on the functional profile of HIV-specific CD8(+) T cells

A better control of viral replication in long-term non-progressors has been associated with polyfunctional CD8(+) T cell responses. However, low levels of HIV replication could be the cause rather than the consequence of enhanced immune responses in long-term non-progressors. The functional profile and the expansion ability of HIV-Gag- and HIV-Nef-specific CD8 responses were analysed measuring the production of MIP-1beta, IL-2, TNF-alpha and expression of CD107, using polychromatic flow cytometry, in 36 HIV-infected patients at baseline and after 12 months of highly active antiretroviral therapy (HAART) and complete viral suppression. Most patients presented detectable Gag and Nef responses both at baseline and after 1 year of HAART, with a significant decline after achieving viral suppression. At baseline, the majority of CD8(+) response was due to cells producing only MIP-1beta or simultaneously MIP-1beta and CD107. The functional profile did not significantly change after achieving complete viral suppression with HAART. Therefore, control of HIV-1 replication after 1 year of HAART had no significant impact on the quality of HIV-1-specific CD8 response, but the effects of treatment in long-term, or of early HAART are not known. Thus, it is still uncertain whether multifunctional CD8 responses are the cause or consequence of low plasma viremia.

Virological outcome after structured interruption of antiretroviral therapy for human immunodeficiency virus infection is associated with the functional profile of virus-specific CD8+ T cells

A clear understanding of the antiviral effects of CD8(+) T cells in the context of chronic human immunodeficiency virus (HIV) infection is critical for the development of prophylactic vaccines and therapeutics designed to support T-cell-mediated immunity. However, defining the potential correlates of effective CD8(+) T-cell immunity has proven difficult; notably, comprehensive analyses have demonstrated that the size and shape of the CD8(+) T-cell response are not necessarily indicative of efficacy determined by measures of plasma viral load. Here, we conducted a detailed quantitative and qualitative analysis of CD8(+) T-cell responses to autologous virus in a cohort of six HIV-infected individuals with a history of structured interruption of antiretroviral therapy (ART) (SIT). The magnitude and breadth of the HIV-specific response did not, by themselves, explain the changes observed in plasma virus levels after the cessation of ART. Furthermore, mutational escape from targeted epitopes could not account for the differential virological outcomes in this cohort. However, the functionality of HIV-specific CD8(+) T-cell populations upon antigen encounter, determined by the simultaneous and independent measurement of five CD8(+) T-cell functions (degranulation and gamma interferon, macrophage inflammatory protein 1beta, tumor necrosis factor alpha, and interleukin-2 levels) reflected the emergent level of plasma virus, with multiple functions being elicited in those individuals with lower levels of viremia after SIT. These data show that the quality of the HIV-specific CD8(+) T-cell response, rather than the quantity, is associated with the dynamics of viral replication in the absence of ART and suggest that the effects of SIT can be assessed by measuring the functional profile of HIV-specific CD8(+) T cells.

Comparative evaluation of oral and intranasal priming with replication-competent adenovirus 5 host range mutant (Ad5hr)-simian immunodeficiency virus (SIV) recombinant vaccines on immunogenicity and protective efficacy against SIV(mac251)

Oral, replication-competent Ad-HIV vaccines are advancing to human trials. Previous evaluation of protective efficacy in non-human primates has primarily followed upper respiratory tract administrations. Here we compared sequential oral (O/O) versus intranasal/oral (I/O) priming of rhesus macaques with Ad5 host range mutant-SIV recombinants expressing SIV env/rev, gag, and nef genes followed by boosting with SIV gp120 protein. Cellular immune responses in PBMC were stronger and more frequent after I/O administration. Both groups developed mucosal immunity, including memory cells in bronchial alveolar lavage, and gut-homing receptors on PBMC. Following intrarectal SIV(mac251) challenge, both groups exhibited equivalent, significant protection and robust post-challenge cellular immunity. Our results illustrate the promise of oral replication-competent Ad-recombinant vaccines. Pre-challenge PBMC ELISPOT and proliferative responses did not predict protection in the O/O group, highlighting the need for simple, non-invasive methods to reliably assess mucosal immunity.