T cell control of SARS-CoV-2: When, which, and where?

Efficient immune protection against viruses such as SARS-CoV-2 requires the coordinated activity of innate immunity, B and T cells. Accumulating data point to a critical role for T cells not only in the clearance of established infection, but also for aborting viral replication independently of humoral immunity. Here we review the evidence supporting the contribution of antiviral T cells and consider which of their qualitative features favour efficient control of infection. We highlight how studies of SARS-CoV-2 and other coronaviridae in animals and humans have provided important lessons on the optimal timing (When), functionality and specificity (Which), and location (Where) of antiviral T cells. We discuss the clinical implications, particularly for the development of next-generation vaccines, and emphasise areas requiring further study.

Respiratory mucosal immune memory to SARS-CoV-2 after infection and vaccination

Respiratory mucosal immunity induced by vaccination is vital for protection from coronavirus infection in animal models. In humans, the capacity of peripheral vaccination to generate sustained immunity in the lung mucosa, and how this is influenced by prior SARS-CoV-2 infection, is unknown. Here we show using bronchoalveolar lavage samples that donors with history of both infection and vaccination have more airway mucosal SARS-CoV-2 antibodies and memory B cells than those only vaccinated. Infection also induces populations of airway spike-specific memory CD4+ and CD8+ T cells that are not expanded by vaccination alone. Airway mucosal T cells induced by infection have a distinct hierarchy of antigen specificity compared to the periphery. Spike-specific T cells persist in the lung mucosa for 7 months after the last immunising event. Thus, peripheral vaccination alone does not appear to induce durable lung mucosal immunity against SARS-CoV-2, supporting an argument for the need for vaccines targeting the airways.

Quantitative, multiplexed, targeted proteomics for ascertaining variant specific SARS-CoV-2 antibody response

Determining the protection an individual has to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) variants of concern (VoCs) is crucial for future immune surveillance, vaccine development, and understanding of the changing immune response. We devised an informative assay to current ELISA-based serology using multiplexed, baited, targeted proteomics for direct detection of multiple proteins in the SARS-CoV-2 anti-spike antibody immunocomplex. Serum from individuals collected after infection or first- and second-dose vaccination demonstrates this approach and shows concordance with existing serology and neutralization. Our assays show altered responses of both immunoglobulins and complement to the Alpha (B.1.1.7), Beta (B.1.351), and Delta (B.1.617.1) VoCs and a reduced response to Omicron (B1.1.1529). We were able to identify individuals who had prior infection, and observed that C1q is closely associated with IgG1 (r > 0.82) and may better reflect neutralization to VoCs. Analyzing additional immunoproteins beyond immunoglobulin (Ig) G, provides important information about our understanding of the response to infection and vaccination.

Airway-resident T cells from unexposed individuals cross-recognize SARS-CoV-2

T cells can contribute to clearance of respiratory viruses that cause acute-resolving infections such as SARS-CoV-2, helping to provide long-lived protection against disease. Recent studies have suggested an additional role for T cells in resisting overt infection: pre-existing cross-reactive responses were preferentially enriched in healthcare workers who had abortive infections¹, and in household contacts protected from infection². We hypothesize that such early viral control would require pre-existing cross-reactive memory T cells already resident at the site of infection; such airway-resident responses have been shown to be critical for mediating protection after intranasal vaccination in a murine model of SARS-CoV³. Bronchoalveolar lavage samples from the lower respiratory tract of healthy donors obtained before the COVID-19 pandemic revealed airway-resident, SARS-CoV-2-cross-reactive T cells, which correlated with the strength of human seasonal coronavirus immunity. We therefore demonstrate the potential to harness functional airway-resident SARS-CoV-2-reactive T cells in next-generation mucosal vaccines.

Immune boosting by B.1.1.529 Omicron) depends on previous SARS-CoV-2 exposure

The Omicron, or Pango lineage B.1.1.529, variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) carries multiple spike mutations with high transmissibility and partial neutralizing antibody (nAb) escape. Vaccinated individuals show protection against severe disease, often attributed to primed cellular immunity. We investigated T and B cell immunity against B.1.1.529 in triple BioNTech BNT162b2 messenger RNA-vaccinated health care workers (HCWs) with different SARS-CoV-2 infection histories. B and T cell immunity against previous variants of concern was enhanced in triple-vaccinated individuals, but the magnitude of T and B cell responses against B.1.1.529 spike protein was reduced. Immune imprinting by infection with the earlier B.1.1.7 (Alpha) variant resulted in less durable binding antibody against B.1.1.529. Previously infection-naïve HCWs who became infected during the B.1.1.529 wave showed enhanced immunity against earlier variants but reduced nAb potency and T cell responses against B.1.1.529 itself. Previous Wuhan Hu-1 infection abrogated T cell recognition and any enhanced cross-reactive neutralizing immunity on infection with B.1.1.529.

NK cells limit therapeutic vaccine-induced CD8+T cell immunity in a PD-L1-dependent manner

A better understanding of mechanisms that regulate CD8+T cell responses to therapeutic vaccines is needed to develop approaches to enhance vaccine efficacy for chronic viral infections and cancers. We show here that NK cell depletion enhanced antigen-specific T cell responses to chimp adenoviral vector (ChAdOx) vaccination in a mouse model of chronic HBV infection (CHB). Probing the mechanism underlying this negative regulation, we observed that CHB drove parallel up-regulation of programmed cell death ligand 1 (PD-L1) on liver-resident NK cells and programmed cell death 1 (PD-1) on intrahepatic T cells. PD-L1-expressing liver-resident NK cells suppressed PD-1hiCD8+T cells enriched within the HBV-specific response to therapeutic vaccination. Cytokine activation of NK cells also induced PD-L1, and combining cytokine activation with PD-L1 blockade resulted in conversion of NK cells into efficient helpers that boosted HBV-specific CD8+T cell responses to therapeutic vaccination in mice and to chronic infection in humans. Our findings delineate an immunotherapeutic combination that can boost the response to therapeutic vaccination in CHB and highlight the broader importance of PD-L1-dependent regulation of T cells by cytokine-activated NK cells.

Characterisation and induction of tissue-resident gamma delta T-cells to target hepatocellular carcinoma

Immunotherapy is now the standard of care for advanced hepatocellular carcinoma (HCC), yet many patients fail to respond. A major unmet goal is the boosting of T-cells with both strong HCC reactivity and the protective advantages of tissue-resident memory T-cells (T_RM). Here, we show that higher intratumoural frequencies of γδ T-cells, which have potential for HLA-unrestricted tumour reactivity, associate with enhanced HCC patient survival. We demonstrate that γδ T-cells exhibit bona fide tissue-residency in human liver and HCC, with γδT_RM showing no egress from hepatic vasculature, persistence for >10 years and superior anti-tumour cytokine production. The Vγ9Vδ2 T-cell subset is selectively depleted in HCC but can efficiently target HCC cell lines sensitised to accumulate isopentenyl-pyrophosphate by the aminobisphosphonate Zoledronic acid. Aminobisphosphonate-based expansion of peripheral Vγ9Vδ2 T-cells recapitulates a T_RM phenotype and boosts cytotoxic potential. Thus, our data suggest more universally effective HCC immunotherapy may be achieved by combining aminobisphosphonates to induce Vγ9Vδ2T_RM capable of replenishing the depleted pool, with additional intratumoural delivery to sensitise HCC to Vγ9Vδ2T_RM-based targeting.

Pre-existing polymerase-specific T cells expand in abortive seronegative SARS-CoV-2

Individuals with potential exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) do not necessarily develop PCR or antibody positivity, suggesting that some individuals may clear subclinical infection before seroconversion. T cells can contribute to the rapid clearance of SARS-CoV-2 and other coronavirus infections1-3. Here we hypothesize that pre-existing memory T cell responses, with cross-protective potential against SARS-CoV-2 (refs. 4-11), would expand in vivo to support rapid viral control, aborting infection. We measured SARS-CoV-2-reactive T cells, including those against the early transcribed replication-transcription complex (RTC)12,13, in intensively monitored healthcare workers (HCWs) who tested repeatedly negative according to PCR, antibody binding and neutralization assays (seronegative HCWs (SN-HCWs)). SN-HCWs had stronger, more multispecific memory T cells compared with a cohort of unexposed individuals from before the pandemic (prepandemic cohort), and these cells were more frequently directed against the RTC than the structural-protein-dominated responses observed after detectable infection (matched concurrent cohort). SN-HCWs with the strongest RTC-specific T cells had an increase in IFI27, a robust early innate signature of SARS-CoV-2 (ref. 14), suggesting abortive infection. RNA polymerase within RTC was the largest region of high sequence conservation across human seasonal coronaviruses (HCoV) and SARS-CoV-2 clades. RNA polymerase was preferentially targeted (among the regions tested) by T cells from prepandemic cohorts and SN-HCWs. RTC-epitope-specific T cells that cross-recognized HCoV variants were identified in SN-HCWs. Enriched pre-existing RNA-polymerase-specific T cells expanded in vivo to preferentially accumulate in the memory response after putative abortive compared to overt SARS-CoV-2 infection. Our data highlight RTC-specific T cells as targets for vaccines against endemic and emerging Coronaviridae.

Antigen Delivery to DEC205+ Dendritic Cells Induces Immunological Memory and Protective Therapeutic Effects against HPV-Associated Tumors at Different Anatomical Sites

The generation of successful anticancer vaccines relies on the ability to induce efficient and long-lasting immune responses to tumor antigens. In this scenario, dendritic cells (DCs) are essential cellular components in the generation of antitumor immune responses. Thus, delivery of tumor antigens to specific DC populations represents a promising approach to enhance the efficiency of antitumor immunotherapies. In the present study, we employed antibody-antigen conjugates targeting a specific DC C-type lectin receptor. For that purpose, we genetically fused the anti-DEC205 monoclonal antibody to the type 16 human papillomavirus (HPV-16) E7 oncoprotein to create a therapeutic vaccine to treat HPV-associated tumors in syngeneic mouse tumor models. The therapeutic efficacy of the αDEC205-E7 mAb was investigated in three distinct anatomical tumor models (subcutaneous, lingual and intravaginal). The immunization regimen comprised two doses of the αDEC205-E7 mAb coadministered with a DC maturation stimulus (Polyinosinic:polycytidylic acid, poly (I:C)) as an adjuvant. The combined immunotherapy produced robust antitumor effects on both the subcutaneous and orthotopic tumor models, stimulating rapid tumor regression and long-term survival. These outcomes were related to the activation of tumor antigen-specific CD8⁺ T cells in both systemic compartments and lymphoid tissues. The αDEC205-E7 antibody plus poly (I:C) administration induced long-lasting immunity and controlled tumor relapses. Our results highlight that the delivery of HPV tumor antigens to DCs, particularly via the DEC205 surface receptor, is a promising therapeutic approach, providing new opportunities for the development of alternative immunotherapies for patients with HPV-associated tumors at different anatomical sites.

Targeting human Acyl-CoA:cholesterol acyltransferase as a dual viral and T cell metabolic checkpoint

Determining divergent metabolic requirements of T cells, and the viruses and tumours they fail to combat, could provide new therapeutic checkpoints. Inhibition of acyl-CoA:cholesterol acyltransferase (ACAT) has direct anti-carcinogenic activity. Here, we show that ACAT inhibition has antiviral activity against hepatitis B (HBV), as well as boosting protective anti-HBV and anti-hepatocellular carcinoma (HCC) T cells. ACAT inhibition reduces CD8+ T cell neutral lipid droplets and promotes lipid microdomains, enhancing TCR signalling and TCR-independent bioenergetics. Dysfunctional HBV- and HCC-specific T cells are rescued by ACAT inhibitors directly ex vivo from human liver and tumour tissue respectively, including tissue-resident responses. ACAT inhibition enhances in vitro responsiveness of HBV-specific CD8+ T cells to PD-1 blockade and increases the functional avidity of TCR-gene-modified T cells. Finally, ACAT regulates HBV particle genesis in vitro, with inhibitors reducing both virions and subviral particles. Thus, ACAT inhibition provides a paradigm of a metabolic checkpoint able to constrain tumours and viruses but rescue exhausted T cells, rendering it an attractive therapeutic target for the functional cure of HBV and HBV-related HCC.

Human Liver Memory CD8+ T Cells Use Autophagy for Tissue Residence

Tissue-resident memory T cells have critical roles in long-term pathogen and tumor immune surveillance in the liver. We investigate the role of autophagy in equipping human memory T cells to acquire tissue residence and maintain functionality in the immunosuppressive liver environment. By performing ex vivo staining of freshly isolated cells from human liver tissue, we find that an increased rate of basal autophagy is a hallmark of intrahepatic lymphocytes, particularly liver-resident CD8⁺ T cells. CD8⁺ T cells with increased autophagy are those best able to proliferate and mediate cytotoxicity and cytokine production. Conversely, blocking autophagy induction results in the accumulation of depolarized mitochondria, a feature of exhausted T cells. Primary hepatic stellate cells or the prototypic hepatic cytokine interleukin (IL)-15 induce autophagy in parallel with tissue-homing/retention markers. Inhibition of T cell autophagy abrogates tissue-residence programming. Thus, upregulation of autophagy adapts CD8⁺ T cells to combat mitochondrial depolarization, optimize functionality, and acquire tissue residence.

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An increased rate of basal autophagy is a hallmark of liver-resident CD8⁺ T cells

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Enhanced T cell autophagy can be imprinted by IL-15 or hepatic stellate cells

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Autophagy induction is required for tissue-residence programming in vitro

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Enhanced autophagy maintains T_RM mitochondrial fitness in the liver

Discordant neutralizing antibody and T cell responses in asymptomatic and mild SARS-CoV-2 infection

Understanding the nature of immunity following mild/asymptomatic infection with SARS-CoV-2 is crucial to controlling the pandemic. We analyzed T cell and neutralizing antibody responses in 136 healthcare workers (HCW) 16-18 weeks after United Kingdom lockdown, 76 of whom had mild/asymptomatic SARS-CoV-2 infection captured by serial sampling. Neutralizing antibodies (nAb) were present in 89% of previously infected HCW. T cell responses tended to be lower following asymptomatic infection than in those reporting case-definition symptoms of COVID-19, while nAb titers were maintained irrespective of symptoms. T cell and antibody responses were sometimes discordant. Eleven percent lacked nAb and had undetectable T cell responses to spike protein but had T cells reactive with other SARS-CoV-2 antigens. Our findings suggest that the majority of individuals with mild or asymptomatic SARS-CoV-2 infection carry nAb complemented by multispecific T cell responses at 16-18 weeks after mild or asymptomatic SARS-CoV-2 infection.

Expression of a soluble IL-10 receptor enhances the therapeutic effects of a papillomavirus-associated antitumor vaccine in a murine model

The presence of IL-10, produced either by tumor cells or immunosuppressive cells, is frequently associated with a poor prognosis for cancer progression. It may also negatively impact anticancer treatments, such as immunotherapies, that otherwise would promote the activation of cytotoxic T cells capable of detecting and destroying malignant cells. In the present study, we evaluated a new adjuvant approach for anticancer immunotherapy using a plasmid vector encoding a soluble form of the IL-10 receptor (pIL-10R). pIL-10R was coadministered to mice with a DNA vaccine encoding the type 16 human papillomavirus (HPV-16) E7 oncoprotein genetically fused with glycoprotein D of herpes simplex virus (HSV) (pgDE7h). Immunization regimens based on the coadministration of pIL-10R and pgDE7h enhanced the antitumor immunity elicited in mice injected with TC-1 cells, which express HPV-16 oncoproteins. The administration of the DNA vaccines by in vivo electroporation further enhanced the anticancer effects of the vaccines, leading to the activation of tumor-infiltrating polyfunctional E7-specific cytotoxic CD8+ T cells and control of the expansion of immunosuppressive cells. In addition, the combination of immunotherapy and pIL-10R allowed the control of tumors in more advanced growth stages that otherwise would not be treatable by the pgDE7h vaccine. In conclusion, the proposed treatment involving the expression of IL-10R enhanced the antitumor protective immunity induced by pgDE7h administration and may contribute to the development of more efficient clinical interventions against HPV-induced tumors.

Induction of resident memory T cells enhances the efficacy of cancer vaccine

Tissue-resident memory T cells (Trm) represent a new subset of long-lived memory T cells that remain in tissue and do not recirculate. Although they are considered as early immune effectors in infectious diseases, their role in cancer immunosurveillance remains unknown. In a preclinical model of head and neck cancer, we show that intranasal vaccination with a mucosal vector, the B subunit of Shiga toxin, induces local Trm and inhibits tumour growth. As Trm do not recirculate, we demonstrate their crucial role in the efficacy of cancer vaccine with parabiosis experiments. Blockade of TFGβ decreases the induction of Trm after mucosal vaccine immunization, resulting in the lower efficacy of cancer vaccine. In order to extrapolate this role of Trm in humans, we show that the number of Trm correlates with a better overall survival in lung cancer in multivariate analysis. The induction of Trm may represent a new surrogate biomarker for the efficacy of cancer vaccine. This study also argues for the development of vaccine strategies designed to elicit them.

Herpes Simplex Virus Glycoprotein D Targets a Specific Dendritic Cell Subset and Improves the Performance of Vaccines to Human Papillomavirus-Associated Tumors

Cervical cancer is a major public health problem and one of the leading causes of cancer deaths in women. Virtually all cases of cervical cancer, as well as a growing share of anal and head/neck tumors, are associated with human papillomavirus (HPV) infection. Despite the effectiveness, the available prophylactic vaccines do not benefit women with cervical lesions or cancer. Therefore, the search of new immunotherapeutic approaches to treat HPV-induced tumors is still a priority. The present study characterizes a therapeutic antitumor vaccine based on the genetic fusion of the Herpes simplex virus-1 (HSV-1) glycoprotein D (gD) with the E7 oncoprotein from HPV-16 (gDE7). Two subcutaneous doses of gDE7, admixed with poly (I:C), conferred complete and long-lasting therapeutic antitumor protection on mice previously challenged with tumor cells expressing the HPV-16 oncoproteins. The vaccine induced multifunctional E7-specific CD8⁺ T cells with cytotoxic activity and effector memory phenotype (CD44⁺ CD62L^low). In addition, gDE7 admixed with poly (I:C) vaccination controlled the expansion of tumor-induced regulatory T cells and myeloid-derived suppressor cells. More importantly, gDE7 activated mouse CD11c⁺ CD8α⁺ and human BDCA3⁺ dendritic cells (DC), specialized in antigen cross-presentation to CD8⁺ T cells, under in vitro conditions. These results indicated that the activation of a specific DC population, mediated by gD, improved the antigen-specific immune responses and the therapeutic performance induced by antitumor vaccines. These results open perspectives for the clinical testing of gDE7-based vaccines under the concept of active immunization as a tool for the therapeutic control of cancer. Mol Cancer Ther; 16(9); 1922-33. ©2017 AACR.

Protection against HPV-16-Associated Tumors Requires the Activation of CD8+ Effector Memory T Cells and the Control of Myeloid-Derived Suppressor Cells

Active anticancer immunotherapeutic approaches have been shown to induce cellular or humoral immune responses in patients, but, thus far, the observed outcomes did not ensure their recommendation for clinical use. The induction of tumor-specific CD8(+) T cells, although required for the clearance of most solid tumors, was shown to be insufficient for the development of a successful immunotherapeutic approach. The suppressive immune environment triggered by tumors, including the expansion of myeloid-derived suppressor cells (MDSC), is detrimental to the development of antitumor immune responses and precludes the generation of more promising clinical outcomes. In this work, we characterized the CD8(+) T-cell population specifically involved in the control of tumor growth and the role of MDSCs after administration of an antitumor therapeutic DNA vaccine targeting human papillomavirus type 16 (HPV-16)-associated tumors. Activation of cytotoxic high-avidity CD8(+) T cells with an effector memory phenotype was found in mice grafted with tumor cells expressing the HPV-16 oncoproteins. In addition, MDSC antibody depletion further enhanced the immunotherapeutic effects of the vaccine, resulting in the complete eradication of tumor cells. Collectively, the current results indicate that the simultaneous control of MDSCs and activation of high-avidity tumor-specific effector memory CD8(+) T cells are key features for tumor protection by immunotherapeutic approaches and deserve further testing under clinical conditions. Mol Cancer Ther; 15(8); 1920-30. ©2016 AACR.

Bacterial spores as particulate carriers for gene gun delivery of plasmid DNA

Bacillus subtilis spores represent a suitable platform for the adsorption of proteins, enzymes and viral particles at physiological conditions. In the present work, we demonstrate that purified spores can also adsorb DNA on their surface after treatment with cationic molecules. In addition, we demonstrate that DNA-coated B. subtilis spores can be used as particulate carriers and act as an alternative to gold microparticles for the biolistic (gene gun) administration of plasmid DNA in mice. Gene gun delivery of spores pre-treated with DODAB (dioctadecyldimethylammonium bromide) allowed efficient plasmid DNA absorption and induced protein expression levels similar to those obtained with gold microparticles. More importantly, we demonstrated that a DNA vaccine adsorbed on spores can be loaded into biolistic cartridges and efficiently delivered into mice, which induced specific cellular and antibody responses. Altogether, these data indicate that B. subtilis spores represent a simple and low cost alternative for the in vivo delivery of DNA vaccines by the gene gun technology.

A Therapeutic Her2/neu Vaccine Targeting Dendritic Cells Preferentially Inhibits the Growth of Low Her2/neu-Expressing Tumor in HLA-A2 Transgenic Mice

PURPOSE

E75, a peptide derived from the Her2/neu protein, is the most clinically advanced vaccine approach against breast cancer. In this study, we aimed to optimize the E75 vaccine using a delivery vector targeting dendritic cells, the B-subunit of Shiga toxin (STxB), and to assess the role of various parameters (Her2/neu expression, combination with trastuzumab) in the efficacy of this cancer vaccine in a relevant preclinical model.

EXPERIMENTAL DESIGN

We compared the differential ability of the free E75 peptide or the STxB-E75 vaccine to elicit CD8(+) T cells, and the impact of the vaccine on murine HLA-A2 tumors expressing low or high levels of Her2/neu.

RESULTS

STxB-E75 synergized with granulocyte macrophage colony-stimulating factors and CpG and proved to be more efficient than the free E75 peptide in the induction of multifunctional and high-avidity E75-specific anti-CD8(+) T cells resulting in a potent tumor protection in HLA-A2 transgenic mice. High expression of HER2/neu inhibited the expression of HLA-class I molecules, leading to a poor recognition of human or murine tumors by E75-specific cytotoxic CD8(+) T cells. In line with these results, STxB-E75 preferentially inhibited the growth of HLA-A2 tumors expressing low levels of Her2/neu. Coadministration of anti-Her2/neu mAb potentiated this effect.

CONCLUSIONS

STxB-E75 vaccine is a potent candidate to be tested in patients with low Her2/neu-expressing tumors. It could also be indicated in patients expressing high levels of Her2/neu and low intratumoral T-cell infiltration to boost the recruitment of T cells-a key parameter in the efficacy of anti-Her2/neu mAb therapy. Clin Cancer Res; 22(16); 4133-44. ©2016 AACR.

Mucosal vaccines: novel strategies and applications for the control of pathogens and tumors at mucosal sites

The mucosal immune system displays several adaptations reflecting the exposure to the external environment. The efficient induction of mucosal immune responses also requires specific approaches, such as the use of appropriate administration routes and specific adjuvants and/or delivery systems. In contrast to vaccines delivered via parenteral routes, experimental, and clinical evidences demonstrated that mucosal vaccines can efficiently induce local immune responses to pathogens or tumors located at mucosal sites as well as systemic response. At least in part, such features can be explained by the compartmentalization of mucosal B and T cell populations that play important roles in the modulation of local immune responses. In the present review, we discuss molecular and cellular features of the mucosal immune system as well as novel immunization approaches that may lead to the development of innovative and efficient vaccines targeting pathogens and tumors at different mucosal sites.

Bacillus subtilis spores as adjuvants for DNA vaccines

Recently, Bacillus subtilis spores were shown to be endowed with strong adjuvant capacity when co-administered with purified antigenic proteins. In the present study we assessed whether spores possess adjuvant properties when combined with DNA vaccines. We showed that B. subtilis spores promoted the activation of dendritic cells in vitro and induced migration of pro-inflammatory cells after parenteral administration to mice. Likewise, co-administration of spores with a DNA vaccine encoding the human papillomavirus type 16 (HPV-16) E7 protein enhanced the activation of antigen-specific CD8(+) T cell responses in vivo. Mice immunized with the DNA vaccine admixed with spores presented a protective immunity increase to previously implanted tumor cells, capable of expressing HPV-16 oncoproteins. Finally, we observed that the adjuvant effect can vary accordingly to the number of co-administered spores which may be ascribed with the ability to induce. Collectively, the present results demonstrate for the first time that B. subtilis spores can also confer adjuvant effects to DNA vaccines.

Enhanced therapeutic effects conferred by an experimental DNA vaccine targeting human papillomavirus-induced tumors

Human papillomavirus (HPV) infection is responsible for all cervical cancer cases, other anogenital cancers, and head and neck tumors. The epidemiological relevance of HPV-induced tumors reinforces the need for the development of therapeutic antitumor vaccines. Clinical trials with different vaccine formulations, particularly DNA vaccines, have provided promising results but have still been unable to achieve the immunogenicity required for use in infected patients. In experimental conditions, anticancer HPV-specific vaccines induced E7-specific CD8(+) T-cell responses but did not confer full therapeutic antitumor protection in mice with transplanted HPV-expressing TC-1 cells, which are the most frequently used nonclinical protection correlate for antitumor effects. Our group has developed a DNA vaccine strategy based on the fusion of HPV oncoproteins to the herpes virus gD protein. This vaccine promoted the induction of antigen-specific cytotoxic CD8(+) T-cell responses and partial antitumor therapeutic effects based on the blockade of coinhibitory signals and the enhancement of coactivation mechanisms. In the present study, we report conditions leading to full therapeutic antitumor effects using the TC-1 cell murine model after a single vaccine dose. The combination of a coadministered plasmid encoding IL-2, optimization of the coding sequence for mammalian cells, and the use of different delivery routes resulted in enhancements of the E7-specific cytotoxic CD8(+) T-cell responses and full therapeutic protection under experimental conditions. The combination of these strategies augmented the potency of the DNA vaccine formulation to levels not previously achieved by other therapeutic antitumor vaccines under similar experimental conditions, including some that have been taken to clinical trials.

Bicistronic DNA vaccines simultaneously encoding HIV, HSV and HPV antigens promote CD8⁺ T cell responses and protective immunity

Millions of people worldwide are currently infected with human papillomavirus (HPV), herpes simplex virus (HSV) or human immunodeficiency virus (HIV). For this enormous contingent of people, the search for preventive and therapeutic immunological approaches represents a hope for the eradication of latent infection and/or virus-associated cancer. To date, attempts to develop vaccines against these viruses have been mainly based on a monovalent concept, in which one or more antigens of a virus are incorporated into a vaccine formulation. In the present report, we designed and tested an immunization strategy based on DNA vaccines that simultaneously encode antigens for HIV, HSV and HPV. With this purpose in mind, we tested two bicistronic DNA vaccines (pIRES I and pIRES II) that encode the HPV-16 oncoprotein E7 and the HIV protein p24 both genetically fused to the HSV-1 gD envelope protein. Mice i.m. immunized with the DNA vaccines mounted antigen-specific CD8⁺ T cell responses, including in vivo cytotoxic responses, against the three antigens. Under experimental conditions, the vaccines conferred protective immunity against challenges with a vaccinia virus expressing the HIV-derived protein Gag, an HSV-1 virus strain and implantation of tumor cells expressing the HPV-16 oncoproteins. Altogether, our results show that the concept of a trivalent HIV, HSV, and HPV vaccine capable to induce CD8⁺ T cell-dependent responses is feasible and may aid in the development of preventive and/or therapeutic approaches for the control of diseases associated with these viruses.

Purified herpes simplex type 1 glycoprotein D (gD) genetically fused with the type 16 human papillomavirus E7 oncoprotein enhances antigen-specific CD8+ T cell responses and confers protective antitumor immunity

Type 1 herpes virus (HSV-1) glycoprotein D (gD) enhances antigen-specific immune responses, particularly CD8(+) T cell responses, in mice immunized with DNA vaccines encoding hybrid proteins genetically fused with the target antigen at a site near the C-terminal end. These effects are attributed to the interaction of gD with the herpes virus entry mediator (HVEM) and the concomitant blockade of a coinhibitory mechanism mediated by the B- and T-lymphocyte attenuator (BTLA). However, questions concerning the requirement for endogenous synthesis of the antigen or the adjuvant/antigen fusion itself have not been addressed so far. In the present study, we investigated these points using purified recombinant gDs, genetically fused or not with type 16 papilloma virus (HPV-16) E7 oncoprotein. Soluble recombinant gDs, but not denatured forms, retained the ability to bind surface-exposed cellular receptors of HVEM-expressing U937 cells. In addition, in vivo administration of the recombinant proteins, particularly gD genetically fused with E7 (gDE7), promoted the activation of dendritic cells (DC) and antigen-specific cytotoxic CD8(+) T cells. More relevantly, mice immunized with the gDE7 protein developed complete preventive and partial therapeutic antitumor protection, as measured in mice following the implantation of TC-1 cells expressing HPV-16 oncoproteins. Collectively, these results demonstrate that the T cell adjuvant effects of the HSV-1 gD protein did not require endogenous synthesis and could be demonstrated in mice immunized with purified recombinant proteins.

Anti-tumor DNA vaccines based on the expression of human papillomavirus-16 E6/E7 oncoproteins genetically fused with the glycoprotein D from herpes simplex virus-1

DNA vaccines encoding the human papillomavirus type-16 (HPV-16) E6 and E7 oncoproteins genetically fused to the human herpes simplex virus type 1 (HSV-1) gD protein were tested in mice for induction of T cell-mediated immunity and protection against tumor cell challenge. Hybrid genes, generated after insertion of E6 or E7-encoding sequences into internal sites of the gD-encoding gene, were transcribed in vitro and the chimeric proteins were expressed at the surface of in vitro-transfected mammalian cells. Female C57BL/6 mice immunized with 4 intramuscular doses (100 microg of DNA/dose) of the DNA vaccines encoding E7 efficiently generated E7-specific CD8(+) T cells. Vaccination of mice with the DNA vaccines encoding the E7, or both E6 and E7, conferred complete protection to challenges from TC-1 tumor cells and partial therapeutic effect (40%) in mice inoculated with TC-1 cells on the same day or 5 days prior to the first vaccine dose.