Identification of novel immunodominant CD4+ Th1-type T-cell peptide epitopes from herpes simplex virus glycoprotein D that confer protective immunity

Dysfunctional Senescent Herpes Simplex Virus-Specific CD57+CD8+ T Cells Are Associated with Symptomatic Recurrent Ocular Herpes in Humans

Herpes simplex virus (HSV)-specific CD8+ T cells protect mice from herpes infection and disease. However, the phenotype and function of HSV-specific CD8+ T cells that play a key role in the "natural" protection seen in HSV-1-seropositive healthy asymptomatic (ASYMP) patients (who have never had clinical herpes disease) remain to be determined. We previously reported that symptomatic (SYMP) patients (who have frequent bouts of recurrent ocular herpes disease) had more undifferentiated and dysfunctional HSV-specific CD8+ T cells. In contrast, healthy ASYMP individuals maintained a significantly higher proportion of differentiated polyfunctional CD8+ T cells. Here, we report that HSV-specific CD8+ T cells from 10 SYMP patients, but not HSV-specific CD8+ T cells from 10 ASYMP patients, have phenotypic and functional characteristics of cellular senescence, including: (i) high frequency of senescent (CD57+) and exhausted (PD-1+) CD8+ T cells; (ii) late terminally differentiated (KLRG1+), non-proliferating CD8+ T cells; (iii) HSV-specific CD8+ T cells which decreased in number over time and were not homeostatically maintained, as indicated by a reduction in the number of CD127+CD8+ T cells; (iv) loss of the co-stimulatory molecule CD28 on HSV-specific CD8+ T cells; and (v) decreased production of effector molecules (granzyme B and perforin) by HSV-specific CD8+ T cells. Our findings provide insights into the role of senescence in HSV-specific CD8+ T cells in susceptibility to recurrent herpes and have implications for T-cell-based immunotherapeutic strategies against recurrent herpes in humans.

Immunological Control of Herpes Simplex Virus Type 1 Infection: A Non-Thermal Plasma-Based Approach

Herpes simplex virus type 1 (HSV-1) causes a lifelong infection due to latency established in the trigeminal ganglia, which is the source of recurrent outbreaks of cold sores. The lifelong persistence of HSV-1 is further facilitated by the lack of cure strategies, unsuccessful vaccine development, and the inability of the host immune system to clear HSV-1. Despite the inefficiencies of the immune system, the course of HSV-1 infection remains under strict immunological control. Specifically, HSV-1 is controlled by a CD8+ T cell response that is cytotoxic to HSV-1-infected cells, restricts acute infection, and uses noncytolytic mechanisms to suppress reactivation in the TG. When this CD8+ T cell response is disrupted, reactivation of latent HSV-1 occurs. With antiviral therapies unable to cure HSV-1 and prophylactic vaccine strategies failing to stimulate a protective response, we propose non-thermal plasma (NTP) as a potential therapy effective against recurrent HSV-1 infection. We have demonstrated that NTP, when applied directly to HSV-1-infected cells, has antiviral effects and stimulates cellular stress and immunomodulatory responses. We further propose that the direct effects of NTP will lead to long-lasting indirect effects such as reduced viral seeding into the TG and enhanced HSV-1-specific CD8+ T cell responses that exert greater immune control over HSV-1 infection.

The Cooperation of IL-29 and PLGA Nanoparticles Improves the Protective Immunity of the gD-1 DNA Vaccine Against Herpes Simplex Virus Type 1 in Mice

In clinical practice, the low immunogenicity and low stability of the DNA plasmid vaccine candidates are two significant shortcomings in their application against infectious diseases. To overcome these two disadvantages, the plasmid expressing IL-29 (pIL-29) as a genetic adjuvant and polylactic-co-glycolic acid (PLGA) as a non-viral delivery system were used, respectively. In this study, the pIL-29 encapsulated in PLGA nanoparticles (nanoIL-29) and the pgD1 encapsulated in PLGA nanoparticles (nanoVac) were simultaneously applied to boost immunologic responses against HSV-1. We generated spherical nanoparticles with encapsulation efficiency of 75 ± 5% and sustained the release of plasmids from them. Then, Balb/c mice were subcutaneously immunized twice with nanoVac+nanoIL-29, Vac+IL-29, nanoVac, Vac, nanoIL-29, and/or IL-29 in addition to negative and positive control groups. Cellular immunity was evaluated via lymphocyte proliferation assay, cytotoxicity test, and IFN-γ, IL-4, and IL-2 measurements. Mice were also challenged with 50X LD50 of HSV-1. The nanoVac+nanoIL-29 candidate vaccine efficiently enhances CTL and Th1-immune responses and increases the survival rates by 100% in mice vaccinated by co-administration of nanoVac and nanoIL-29 against the HSV-1 challenge. The newly proposed vaccine is worth studying in further clinical trials, because it could effectively improve cellular immune responses and protected mice against HSV-1.

Antiviral Activity of Oridonin Against Herpes Simplex Virus Type 1

Purpose

In search of new potent treatment of herpes simplex keratitis (HSK), inhibitory effect of oridonin (Ori) on herpes simplex virus type 1 (HSV-1) was validated by experiments.

Methods

For evaluating inhibitory effect of oridonin on herpes simplex virus type 1, a series of in-vivo and in-vitro studies were carried out. Mouse HSV-1 infection model was used in the in-vivo experiments. Experimental mice were classified in five different groups: Mock (mock-infected), HSV-1+ DMSO, HSV-1+ Ori, HSV-1+ ACV, combined Ori and ACV+HSV-1. Corneas of Mock, HSV-1+ DMSO, HSV-1+ Ori group were sent for mRNA-sequencing after 3 days post infection (dpi). The expression of virus and host-related genes was evaluated by quantitative real-time polymerase chain reaction (qPCR). Vero cells HSV-1 infection models were used in the in-vitro experiments.

Results

The application of ACV, Oridonin alone or a combination of both could alleviate HSV-1 severity and inhibit HSV-1 virus replication in C57BL/6 mice models. qPCR showed that compared with mock group, the expression of interleukin-6 (il-6), interleukin-1α (il-1α), and Tumor-necrosis factor-alpha (tnf-α) was up-regulated in DMSO+HSV-1 group and suppressed in other three group. Moreover, the expression of nod-like receptor protein (nlrp3), caspase 1 and interleukin-1β (il-1β) were depressed in the oridonin-treated group. Oridonin significantly inhibits HSV-1 replication, HSV-1 related gene expression, and the production of progeny HSV-1 viruses in vitro. Besides, oridonin affect the replication phase but not HSV-1 entry or penetration and cannot inactivate HSV-1.

Conclusion

Oridonin alleviates herpes simplex keratitis infection in mouse, which may be attributed to inhibition of the NLRP3-inflammasome-IL-1β pathway. Our study illustrates that Oridonin has potential promise for application in treating HSK and other diseases caused by HSV-1 infection.

Multiple-Allele MHC Class II Epitope Engineering by a Molecular Dynamics-Based Evolution Protocol

Epitopes that bind simultaneously to all human alleles of Major Histocompatibility Complex class II (MHC II) are considered one of the key factors for the development of improved vaccines and cancer immunotherapies. To engineer MHC II multiple-allele binders, we developed a protocol called PanMHC-PARCE, based on the unsupervised optimization of the epitope sequence by single-point mutations, parallel explicit-solvent molecular dynamics simulations and scoring of the MHC II-epitope complexes. The key idea is accepting mutations that not only improve the affinity but also reduce the affinity gap between the alleles. We applied this methodology to enhance a Plasmodium vivax epitope for multiple-allele binding. In vitro rate-binding assays showed that four engineered peptides were able to bind with improved affinity toward multiple human MHC II alleles. Moreover, we demonstrated that mice immunized with the peptides exhibited interferon-gamma cellular immune response. Overall, the method enables the engineering of peptides with improved binding properties that can be used for the generation of new immunotherapies.

Human Epitopes Identified from Herpes Simplex Virus Tegument Protein VP11/12 (UL46) Recall Multifunctional Effector Memory CD4+ TEM Cells in Asymptomatic Individuals and Protect from Ocular Herpes Infection and Disease in "Humanized" HLA-DR Transgenic Mice

While the role of CD8+ T cells in the control of herpes simplex virus 1 (HSV-1) infection and disease is gaining wider acceptance, a direct involvement of effector CD4+ T cells in this protection and the phenotype and function of HSV-specific human CD4+ T cell epitopes remain to be fully elucidated. In the present study, we report that several epitopes from the HSV-1 virion tegument protein (VP11/12) encoded by UL46 are targeted by CD4+ T cells from HSV-seropositive asymptomatic individuals (who, despite being infected, never develop any recurrent herpetic disease). Among these, we identified two immunodominant effector memory CD4+ TEM cell epitopes, amino acids (aa) 129 to 143 of VP11/12 (VP11/12129-143) and VP11/12483-497, using in silico, in vitro, and in vivo approaches based on the following: (i) a combination of the TEPITOPE algorithm and PepScan library scanning of the entire 718 aa of HSV-1 VP11/12 sequence; (ii) an in silico peptide-protein docking analysis and in vitro binding assay that identify epitopes with high affinity to soluble HLA-DRB1 molecules; and (iii) an ELISpot assay and intracellular detection of gamma interferon (IFN-γ), CD107a/b degranulation, and CD4+ T cell carboxyfluorescein succinimidyl ester (CFSE) proliferation assays. We demonstrated that native VP11/12129-143 and VP11/12483-497 epitopes presented by HSV-1-infected HLA-DR-positive target cells were recognized mainly by effector memory CD4+ TEM cells while being less targeted by FOXP3+ CD4+ CD25+ regulatory T cells. Furthermore, immunization of HLA-DR transgenic mice with a mixture of the two immunodominant human VP11/12 CD4+ TEM cell epitopes, but not with cryptic epitopes, induced HSV-specific polyfunctional IFN-γ-producing CD107ab+ CD4+ T cells associated with protective immunity against ocular herpes infection and disease.IMPORTANCE We report that naturally protected HSV-1-seropositive asymptomatic individuals develop a higher frequency of antiviral effector memory CD4+ TEM cells specific to two immunodominant epitopes derived from the HSV-1 tegument protein VP11/12. Immunization of HLA-DR transgenic mice with a mixture of these two immunodominant CD4+ T cell epitopes induced a robust antiviral CD4+ T cell response in the cornea that was associated with protective immunity against ocular herpes. The emerging concept of developing an asymptomatic herpes vaccine that would boost effector memory CD4+ and CD8+ TEM cell responses is discussed.

NLRP3, NLRP12, and IFI16 Inflammasomes Induction and Caspase-1 Activation Triggered by Virulent HSV-1 Strains Are Associated With Severe Corneal Inflammatory Herpetic Disease

The crosstalk between the host's inflammasome system and the invading virulent/less-virulent viruses determines the outcome of the ensuing inflammatory response. An appropriate activation of inflammasomes triggers antiviral inflammatory responses that clear the virus and heal the inflamed tissue. However, an aberrant activation of inflammasomes can result in a harmful and overwhelming inflammation that could damage the infected tissue. The underlying host's immune mechanisms and the viral virulent factors that impact severe clinical inflammatory disease remain to be fully elucidated. In this study, we used herpes simplex virus type 1 (HSV-1), the causative agent of corneal inflammatory herpetic disease, as a model pathogen to determine: (i) Whether and how the virulence of a virus affects the type and the activation level of the inflammasomes; and (ii) How triggering specific inflammasomes translates into protective or damaging inflammatory response. We showed that, in contrast to the less-virulent HSV-1 strains (RE, F, KOS, and KOS63), corneal infection of B6 mice with the virulent HSV-1 strains (McKrae, 17 or KOS79): (i) Induced simultaneous expression of the NLRP3, NLRP12, and IFI16 inflammasomes; (ii) Increased production of the biologically active Caspase-1 and pro-inflammatory cytokines IL-1β and IL-18; (iii) Heightened recruitment into the inflamed cornea of CD45highLy6C+Ly6G-F4/80+CD11b+CD11c- inflammatory monocytes and CD45highCD11b+F4/80-Ly6GhiLy6Cmed neutrophils; and (iv) This intensified inflammatory response was associated with a severe corneal herpetic disease, irrespective of the level of virus replication in the cornea. Similarly, in vitro infection of human corneal epithelial cells and human monocytic THP-1 cells with the virulent HSV-1 strains triggered a synchronized early expression of NLRP3, NLRP12 and IFI16, 2 h post-infection, associated with formation of single and dense specks of the adapter molecule ASC in HSV(+) cells, but not in the neighboring bystander HSV(-) cells. This was associated with increased cleavages of Caspase-1, IL-1β, and IL-18. These findings suggest a previously unappreciated role of viral virulence in a synchronized early induction of the NLRP3, NLRP12, and IFI16 inflammasomes that lead to a damaging inflammatory response. A potential role of common virus virulent factors that stimulate this harmful inflammatory corneal disease is currently under investigation.

Unique Type I Interferon, Expansion/Survival Cytokines, and JAK/STAT Gene Signatures of Multifunctional Herpes Simplex Virus-Specific Effector Memory CD8+ TEM Cells Are Associated with Asymptomatic Herpes in Humans

A large proportion of the world population harbors herpes simplex virus 1 (HSV-1), a major cause of infectious corneal blindness. HSV-specific CD8⁺ T cells protect from herpesvirus infection and disease. However, the genomic, phenotypic, and functional characteristics of CD8⁺ T cells associated with the protection seen in asymptomatic (ASYMP) individuals, who, despite being infected, never experienced any recurrent herpetic disease, remains to be fully elucidated. In this investigation, we compared the phenotype, function, and level of expression of a comprehensive panel of 579 immune genes of memory CD8⁺ T cells, sharing the same HSV-1 epitope specificities, and freshly isolated peripheral blood from well-characterized cohorts of protected ASYMP and nonprotected symptomatic (SYMP) individuals, with a history of numerous episodes of recurrent herpetic disease, using the high-throughput digital NanoString nCounter system and flow cytometry. Interestingly, our results demonstrated that memory CD8⁺ T cells from ASYMP individuals expressed a unique set of genes involved in expansion and survival, type I interferon (IFN-I), and JAK/STAT pathways. Frequent multifunctional HSV-specific effector memory CD62L^low CD44^high CD8⁺ T_EM cells were detected in ASYMP individuals compared to more of monofunctional central memory CD62L^high CD44^high CD8⁺ T_CM cells in SYMP individuals. Shedding light on the genotype, phenotype, and function of antiviral CD8⁺ T cells from "naturally protected" ASYMP individuals will help design future T-cell-based ocular herpes immunotherapeutic vaccines.IMPORTANCE A staggering number of the world population harbors herpes simplex virus 1 (HSV-1) potentially leading to blinding recurrent herpetic disease. While the majority are asymptomatic (ASYMP) individuals who never experienced any recurrent herpetic disease, symptomatic (SYMP) individuals have a history of numerous episodes of recurrent ocular herpetic disease. This study elucidates the phenotype, the effector function, and the gene signatures of memory CD8⁺ T-cell populations associated with protection seen in ASYMP individuals. Frequent multifunctional HSV-specific effector memory CD8⁺ T_EM cells were detected in ASYMP individuals. In contrast, nonprotected SYMP individuals had more central memory CD8⁺ T_CM cells. The memory CD8⁺ T_EM cells from ASYMP individuals expressed unique gene signatures characterized by higher levels of type I interferon (IFN), expansion and expansion/survival cytokines, and JAK/STAT pathways. Future studies on the genotype, phenotype, and function of antiviral CD8⁺ T cells from "naturally protected" ASYMP individuals will help in the potential design of T-cell-based ocular herpes vaccines.

Phenotypic and Functional Signatures of Herpes Simplex Virus-Specific Effector Memory CD73+CD45RAhighCCR7lowCD8+ TEMRA and CD73+CD45RAlowCCR7lowCD8+ TEM Cells Are Associated with Asymptomatic Ocular Herpes

HSV type 1 (HSV-1)-specific CD8⁺ T cells protect from herpes infection and disease. However, the nature of protective CD8⁺ T cells in HSV-1 seropositive healthy asymptomatic (ASYMP) individuals (with no history of clinical herpes disease) remains to be determined. In this study, we compared the phenotype and function of HSV-specific CD8⁺ T cells from HLA-A*02:01-positive ASYMP and symptomatic (SYMP) individuals (with a documented history of numerous episodes of recurrent ocular herpetic disease). We report that although SYMP and ASYMP individuals have similar frequencies of HSV-specific CD8⁺ T cells, the "naturally" protected ASYMP individuals have a significantly higher proportion of multifunctional HSV-specific effector memory CD8⁺ T cells (CD73⁺CD45RA^highCCR7^lowCD8⁺ effector memory RA (T_EMRA) and CD73⁺CD45RA^lowCCR7^lowCD8⁺ effector memory (T_EM) as compared with SYMP individuals. Similar to humans, HSV-1-infected ASYMP B6 mice had frequent multifunctional HSV-specific CD73⁺CD8⁺ T cells in the cornea, as compared with SYMP mice. Moreover, in contrast to wild type B6, CD73^-/- deficient mice infected ocularly with HSV-1 developed more recurrent corneal herpetic infection and disease. This was associated with less functional CD8⁺ T cells in the cornea and trigeminal ganglia, the sites of acute and latent infection. The phenotypic and functional characteristics of HSV-specific circulating and in situ CD73⁺CD8⁺ T cells, demonstrated in both ASYMP humans and mice, suggest a positive role for effector memory CD8⁺ T cells expressing the CD73 costimulatory molecule in the protection against ocular herpes infection and disease. These findings are important for the development of safe and effective T cell-based herpes immunotherapy.

Laser Adjuvant-Assisted Peptide Vaccine Promotes Skin Mobilization of Dendritic Cells and Enhances Protective CD8+ TEM and TRM Cell Responses against Herpesvirus Infection and Disease

There is an urgent need for chemical-free and biological-free safe adjuvants to enhance the immunogenicity of vaccines against widespread viral pathogens, such as herpes simplex virus 2 (HSV-2), that infect a large proportion of the world human population. In the present study, we investigated the safety, immunogenicity, and protective efficacy of a laser adjuvant-assisted peptide (LAP) vaccine in the B6 mouse model of genital herpes. This LAP vaccine and its laser-free peptide (LFP) vaccine analog contain the immunodominant HSV-2 glycoprotein B CD8⁺ T cell epitope (HSV-gB_498-505) covalently linked with the promiscuous glycoprotein D CD4⁺ T helper cell epitope (HSV-gD_49-89). Prior to intradermal delivery of the LAP vaccine, the lower-flank shaved skin of B6 or CD11c/eYFP transgenic mice received a topical skin treatment with 5% imiquimod cream and then was exposed for 60 s to a laser, using the FDA-approved nonablative diode. Compared to the LFP vaccine, the LAP vaccine (i) triggered mobilization of dendritic cells (DCs) in the skin, which formed small spots along the laser-treated areas, (ii) induced phenotypic and functional maturation of DCs, (iii) stimulated long-lasting HSV-specific effector memory CD8⁺ T cells (T_EM cells) and tissue-resident CD8⁺ T cells (T_RM cells) locally in the vaginal mucocutaneous tissues (VM), and (iv) induced protective immunity against genital herpes infection and disease. As an alternative to currently used conventional adjuvants, the chemical- and biological-free laser adjuvant offers a well-tolerated, simple-to-produce method to enhance mass vaccination for widespread viral infections.IMPORTANCE Herpes simplex viruses 1 and 2 (HSV-1 and HSV-2) infect a large proportion of the world population. There is an urgent need for chemical-free and biological-free safe adjuvants that would advance mass vaccination against the widespread herpes infections. The present study demonstrates that immunization with a laser-assisted herpes peptide vaccine triggered skin mobilization of dendritic cells (DCs) that stimulated strong and long-lasting HSV-specific effector memory CD8⁺ T cells (T_EM cells) and tissue-resident CD8⁺ T cells (T_RM cells) locally in the vaginal mucocutaneous tissues. The induced local CD8⁺ T cell response was associated with protection against genital herpes infection and disease. These results draw attention to chemical- and biological-free laser adjuvants as alternatives to currently used conventional adjuvants to enhance mass vaccination for widespread viral infections, such as those caused by HSV-1 and HSV-2.

Cyclopeptide scaffolds in carbohydrate-based synthetic vaccines

Cyclopeptides have been recently used successfully as carriers for the multivalent presentation of carbohydrate and peptide antigens in immunotherapy. Beside their synthetic versatility, these scaffolds are indeed interesting due to their stability against enzyme degradation and low immunogenicity. This mini-review highlights the recent advances in the utilization of cyclopeptides to prepare fully synthetic vaccines prototypes against cancers and pathogens.

The potential of currently unavailable herpes virus vaccines

INTRODUCTION

Despite overwhelming experimental work, there are no licensed vaccines against the most frequent Alphaherpesviruses, namely herpes simplex virus 1 and 2 (HSV1 and 2) nor against the Epstein-Barr virus (EBV), a member of the subfamily Gammaherpesvirus.

AREAS COVERED

Since the DNAs of both HSVs reside in the regional sensory ganglia in a latent state (i.e. as circularized episomal molecules), a corresponding vaccine might be useful for immunotherapy rather than for prevention of primary infection. Here we describe the design of a purified subunit vaccine as well as the preparation and efficacy of a recombinant fusion protein consisting of the gD ectodomain from our domestic attenuated HSV1 strain HSZP. The EBV vaccines considered so far, were destined for prevention of infectious mononucleosis (IM) or to prevent formation of EBV related tumors. To design the EBV peptide vaccine, at least 15 carefully selected immunogenic epitopes coming from 12 virus coded proteins were bound to synthetic micro-particle carriers along with a non-specific pathogen recognizing receptor (PRR) stimulating both the T as well as B lymphocytes.

EXPERT COMMENTARY

The efficacy of a novel EBV peptide in the rabbit model was based on criteria such as antibody formation (EA-D detected by ELISA, early and capsid proteins tested by immunoblot), presence of LMP1 antigen and of viral DNA in peripheral white blood cells. Out of 19 peptide combinations used for vaccination, at least 6 showed a satisfactory protective effect.

Differential expression of mRNA and miRNA in guinea pigs following infection with HSV2v

MicroRNAs (miRNAs) are 22-nucleotide single-stranded RNAs which regulate gene expression by targeting 3′ untranslated regions. Previous studies have suggested that miRNAs may be used as markers for investigating the molecular regulation of gene expression. In the present study, miRNA and mRNA expression profiles were investigated using a massively parallel next generation sequencing technique to compare herpes simplex virus (HSV)2-infected (n=3) and healthy (n=3) epithelial tissues from guinea pigs. Total RNA was isolated and RNA sequencing was performed using a HiSeq 2000 sequencing system. Differential expression of miRNA and mRNA was analyzed using two-tailed t-tests. A negative correlation was detected between the miRNAs and their predicted target genes. Following infection with HSV2, 205 and 159 miRNAs were demonstrated to be upregulated and downregulated, respectively. These differentially expressed miRNAs were associated with cellular and metabolic processes, biological regulation, response to stimuli and cellular components of the immune system, as determined by functional gene ontology analysis. Following HSV2 infection, 6 upregulated miRNAs including miR-592, miR-1245b-5p, miR-150, miR-342-5p, miR-1245b-3p and miR-124 were demonstrated to participate in the toll-like receptor (TLR) pathway by targeting related genes. These results suggested that the downregulated genes were associated with the TLR pathway after infection with HSV2. The results of reverse transcription-quantitative polymerase chain reaction analysis were consistent with RNA sequencing, indicating that the increased expression of these miRNAs downregulated the TLR pathway-associated genes, which may mediate the progression of HSV2-induced genital herpes.

Antibody to HSV gD peptide induced by vaccination does not protect against HSV-2 infection in HSV-2 seronegative women

BACKGROUND

In the HIV-1 vaccine trial RV144, ALVAC-HIV prime with an AIDSVAX® B/E boost reduced HIV-1 acquisition by 31% at 42 months post first vaccination. The bivalent AIDSVAX® B/E vaccine contains two gp120 envelope glycoproteins, one from the subtype B HIV-1 MN isolate and one from the subtype CRF01_AE A244 isolate. Each envelope glycoprotein harbors a highly conserved 27-amino acid HSV-1 glycoprotein D (gD) tag sequence that shares 93% sequence identity with the HSV-2 gD sequence. We assessed whether vaccine-induced anti-gD antibodies protected females against HSV-2 acquisition in RV144.

METHODS

Of the women enrolled in RV144, 777 vaccine and 807 placebo recipients were eligible and randomly selected according to their pre-vaccination HSV-1 and HSV-2 serostatus for analysis. Immunoglobulin G (IgG) and IgA responses to gD were determined by a binding antibody multiplex assay and HSV-2 serostatus was determined by Western blot analysis. Ninety-three percent and 75% of the vaccine recipients had anti-gD IgG and IgA responses two weeks post last vaccination, respectively. There was no evidence of reduction in HSV-2 infection by vaccination compared to placebo recipients over 78 weeks of follow-up. The annual incidence of HSV-2 infection in individuals who were HSV-2 negative at baseline or HSV-1 positive and HSV-2 indeterminate at baseline were 4.38/100 person-years (py) and 3.28/100 py in the vaccine and placebo groups, respectively. Baseline HSV-1 status did not affect subsequent HSV-2 acquisition. Specifically, the estimated odds ratio of HSV-2 infection by Week 78 for female placebo recipients who were baseline HSV-1 positive (n = 422) vs. negative (n = 1120) was 1.14 [95% confidence interval 0.66 to 1.94, p = 0.64)]. No evidence of reduction in the incidence of HSV-2 infection by vaccination was detected.

CONCLUSIONS

AIDSVAX® B/E containing gD did not confer protection from HSV-2 acquisition in HSV-2 seronegative women, despite eliciting anti-gD serum antibodies.

Dendritic cell-based vaccines in treating recurrent herpes labialis: Results of pilot clinical study

Recurrent herpes simplex labialis caused predominantly with herpes simplexvirus 1(HSV-1) is a major problem, for which various treatments have minimal impact. Given the important role of the immune system in controlling virus infection, an activation of virus-specific immune responses, in particular,using dendritic cell (DCs) vaccines, seems to be a promising approach for the treatment of patients with frequent recurrences of herpes labialis. The current paper presents the results of a pilot study of the safety and efficacy of DC vaccines in 14 patients with recurrent HSV-1 infections. DCs were generated in presence of GM-CSF and IFN-alpha and were loaded with HSV-1 recombinant viral glycoprotein D (HSV1gD). DCs cells were injected subcutaneously as 2 courses of vaccination during 9 months. Immunotherapy with DCs did not induce any serious side effects and resulted in more than 2-fold reduction in the recurrence rate and significant enhancement of the inter-recurrent time during the 9 months of treatment and subsequent 6-month follow-up period. An obvious clinical improvement was accompanied with an induction of an antigen-specific response to HCV1gD and a normalization of reduced mitogenic responsiveness of mono-nuclear cells. According to long-term survey data (on average 48 months after the beginning of therapy), 87% of respondents reported the decreased incidence of recurrent infection. At this time, most patients (85.7%) responded to HCV1gD stimulation. The data obtained suggests that dendritic cell vaccines may be a promising new approach for the treatment of recurrent labial herpes.

Multiple Approaches for Increasing the Immunogenicity of an Epitope-Based Anti-HIV Vaccine

The development of a highly effective vaccine against the human immunodeficiency virus (HIV) will likely be based on rational vaccine design, since traditional vaccine approaches have failed so far. In recent years, an understanding of what type of immune response is protective against infection and/or disease facilitated vaccine design. T cell-based vaccines against HIV have the goal of limiting both transmission and disease progression by inducing broad and functionally relevant T cell responses. In this context, CD4(+) T cells play a direct cytotoxic role and are also important for the generation and maintenance of functional CD8(+) T and B cell responses. The use of MHC-binding algorithms has allowed the identification of novel CD4(+) T cell epitopes that could be used in vaccine design, the so-called epitope-driven vaccine design. Epitope-based vaccines have the ability to focus the immune response on highly antigenic, conserved epitopes that are fully recognized by the target population. We have recently mapped a set of conserved multiple HLA-DR-binding HIV-1 CD4 epitopes and observed interferon (IFN)-γ-producing CD4(+) T cells when we tested these peptides in peripheral blood mononuclear cells (PBMCs) from HIV-infected individuals. We then designed multiepitopic DNA vaccines that induced broad and polyfunctional T cell responses in immunized mice. In this review we will focus on alternative strategies to increase the immunogenicity of an epitope-based vaccine against HIV infection.

Protective effects of recombinant glycoprotein D based prime boost approach against duck enteritis virus in mice model

Duck virus enteritis, also known as duck plague, is an acute herpes viral infection of ducks caused by duck enteritis virus (DEV). The method of repeated immunization with a live attenuated vaccine has been used for the prevention and control of duck enteritis virus (DEV). However, the incidence of the disease in vaccinated flocks and latency reactivation are the major constraints in the present vaccination programme. The immunogenicity and protective efficacy afforded by intramuscular inoculation of plasmid DNA encoding DEV glycoprotein D (pCDNA-gD) followed by DEV gD expressed in Saccharomyces cerevisia (rgD) was assessed in a murine model. Compared with mice inoculated with DNA (pCDNA-gD) or protein (rgD) only, mice inoculated with the combination of gD DNA and protein had enhanced ELISA antibody titers to DEV and had accelerated clearance of virus following challenge infection. Furthermore, the highest levels of lymphocyte proliferation response, IL-4, IL-12 and IFN-γ production were induced following priming with the DNA vaccine and boosting with the rgD protein. For instance, the specially designed recombinant DEV vector vaccine would be the best choice to use in ducks. It offers an excellent solution to the low vaccination coverage rate in ducks. We expect that the application of this novel vaccine in the near future will greatly decrease the virus load in the environment and reduce outbreaks of DEV in ducks.

Phenotypic and functional characterization of herpes simplex virus glycoprotein B epitope-specific effector and memory CD8+ T cells from symptomatic and asymptomatic individuals with ocular herpes

Herpes simplex virus 1 (HSV-1) glycoprotein B (gB)-specific CD8(+) T cells protect mice from herpes infection and disease. However, whether and which HSV-1 gB-specific CD8(+) T cells play a key role in the "natural" protection seen in HSV-1-seropositive healthy asymptomatic (ASYMP) individuals (who have never had clinical herpes disease) remain to be determined. In this study, we have dissected the phenotypes and the functions of HSV-1 gB-specific CD8(+) T cells from HLA-A*02:01 positive, HSV-1 seropositive ASYMP and symptomatic (SYMP) individuals (with a history of numerous episodes of recurrent ocular herpes disease). We found the following. (i) Healthy ASYMP individuals maintained a significantly higher proportion of differentiated HSV-1 gB-specific effector memory CD8(+) T cells (TEM cells) (CD45RA(low) CCR7(low) CD44(high) CD62L(low)). In contrast, SYMP patients had frequent less-differentiated central memory CD8(+) T cells (TCM cells) (CD45RA(low) CCR7(high) CD44(low) CD62L(high)). (ii) ASYMP individuals had significantly higher proportions of multifunctional effector CD8(+) T cells which responded mainly to gB342-350 and gB561-569 "ASYMP" epitopes, and simultaneously produced IFN-γ, CD107(a/b), granzyme B, and perforin. In contrast, effector CD8(+) T cells from SYMP individuals were mostly monofunctional and were directed mainly against nonoverlapping gB17-25 and gB183-191 "SYMP" epitopes. (iii) Immunization of an HLA-A*02:01 transgenic mouse model of ocular herpes with "ASYMP" CD8(+) TEM cell epitopes, but not with "SYMP" CD8(+) TCM cell epitopes, induced a strong CD8(+) T cell-dependent protective immunity against ocular herpes infection and disease. Our findings provide insights into the role of HSV-specific CD8(+) TEM cells in protection against herpes and should be considered in the development of an effective vaccine.

IMPORTANCE

A significantly higher proportion of differentiated and multifunctional HSV-1 gB-specific effector memory CD8(+) T cells (TEM cells) (CD45RA(low) CCR7(low) CD44(high) CD62L(low)) were found in healthy ASYMP individuals who are seropositive for HSV-1 but never had any recurrent herpetic disease, while there were frequent less-differentiated and monofunctional central memory CD8(+) T cells (TCM cells) (CD45RA(low) CCR7(high) CD44(low) CD62L(high)) in SYMP patients. Immunization with "ASYMP" CD8(+) TEM cell epitopes, but not with "SYMP" CD8(+) TCM cell epitopes, induced a strong protective HSV-specific CD8(+) T cell response in HLA-A*02:01 transgenic mice. These findings are important for the development of a safe and effective T cell-based herpes vaccine.

Alterations in antigen-specific naive CD4 T cell precursors after sepsis impairs their responsiveness to pathogen challenge

Patients surviving the acute stages of sepsis develop compromised T cell immunity and increased susceptibility to infection. Little is known about the decreased CD4 T cell function after sepsis. We tracked the loss and recovery of endogenous Ag-specific CD4 T cell populations after cecal ligation and puncture-induced sepsis and analyzed the CD4 T cell response to heterologous infection during or after recovery. We observed that the sepsis-induced early loss of CD4 T cells was followed by thymic-independent numerical recovery in the total CD4 T cell compartment. Despite this numerical recovery, we detected alterations in the composition of naive CD4 T cell precursor pools, with sustained quantitative reductions in some populations. Mice that had experienced sepsis and were then challenged with epitope-bearing, heterologous pathogens demonstrated significantly reduced priming of recovery-impaired Ag-specific CD4 T cell responses, with regard to both magnitude of expansion and functional capacity on a per-cell basis, which also correlated with intrinsic changes in Vβ clonotype heterogeneity. Our results demonstrate that the recovery of CD4 T cells from sepsis-induced lymphopenia is accompanied by alterations to the composition and function of the Ag-specific CD4 T cell repertoire.

Specificities of human CD4+ T cell responses to an inactivated flavivirus vaccine and infection: correlation with structure and epitope prediction

Tick-borne encephalitis (TBE) virus is endemic in large parts of Europe and Central and Eastern Asia and causes more than 10,000 annual cases of neurological disease in humans. It is closely related to the mosquito-borne yellow fever, dengue, Japanese encephalitis, and West Nile viruses, and vaccination with an inactivated whole-virus vaccine can effectively prevent clinical disease. Neutralizing antibodies are directed to the viral envelope protein (E) and an accepted correlate of immunity. However, data on the specificities of CD4(+) T cells that recognize epitopes in the viral structural proteins and thus can provide direct help to the B cells producing E-specific antibodies are lacking. We therefore conducted a study on the CD4(+) T cell response against the virion proteins in vaccinated people in comparison to TBE patients. The data obtained with overlapping peptides in interleukin-2 (IL-2) enzyme-linked immunosorbent spot (ELISpot) assays were analyzed in relation to the three-dimensional structures of the capsid (C) and E proteins as well as to epitope predictions based on major histocompatibility complex (MHC) class II peptide affinities. In the C protein, peptides corresponding to two out of four alpha helices dominated the response in both vaccinees and patients, whereas in the E protein concordance of immunodominance was restricted to peptides of a single domain (domain III). Epitope predictions were much better for C than for E and were especially erroneous for the transmembrane regions. Our data provide evidence for a strong impact of protein structural features that influence peptide processing, contributing to the discrepancies observed between experimentally determined and computer-predicted CD4(+) T cell epitopes. Importance: Tick-borne encephalitis virus is endemic in large parts of Europe and Asia and causes more than 10,000 annual cases of neurological disease in humans. It is closely related to yellow fever, dengue, Japanese encephalitis, and West Nile viruses, and vaccination with an inactivated vaccine can effectively prevent disease. Both vaccination and natural infection induce the formation of antibodies to a viral surface protein that neutralize the infectivity of the virus and mediate protection. B lymphocytes synthesizing these antibodies require help from other lymphocytes (helper T cells) which recognize small peptides derived from proteins contained in the viral particle. Which of these peptides dominate immune responses to vaccination and infection, however, was unknown. In our study we demonstrate which parts of the proteins contribute most strongly to the helper T cell response, highlight specific weaknesses of currently available approaches for their prediction, and demonstrate similarities and differences between vaccination and infection.

Asymptomatic memory CD8+ T cells: from development and regulation to consideration for human vaccines and immunotherapeutics

Generation and maintenance of high quantity and quality memory CD8(+) T cells determine the level of protection from viral, bacterial, and parasitic re-infections, and hence constitutes a primary goal for T cell epitope-based human vaccines and immunotherapeutics. Phenotypically and functionally characterizing memory CD8(+) T cells that provide protection against herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) infections, which cause blinding ocular herpes, genital herpes, and oro-facial herpes, is critical for better vaccine design. We have recently categorized 2 new major sub-populations of memory symptomatic and asymptomatic CD8(+) T cells based on their phenotype, protective vs. pathogenic function, and anatomical locations. In this report we are discussing a new direction in developing T cell-based human herpes vaccines and immunotherapeutics based on the emerging new concept of "symptomatic and asymptomatic memory CD8(+) T cells."

Asymptomatic HLA-A*02:01-restricted epitopes from herpes simplex virus glycoprotein B preferentially recall polyfunctional CD8+ T cells from seropositive asymptomatic individuals and protect HLA transgenic mice against ocular herpes

Evidence from C57BL/6 mice suggests that CD8(+) T cells, specific to the immunodominant HSV-1 glycoprotein B (gB) H-2(b)-restricted epitope (gB498-505), protect against ocular herpes infection and disease. However, the possible role of CD8(+) T cells, specific to HLA-restricted gB epitopes, in protective immunity seen in HSV-1-seropositive asymptomatic (ASYMP) healthy individuals (who have never had clinical herpes) remains to be determined. In this study, we used multiple prediction algorithms to identify 10 potential HLA-A*02:01-restricted CD8(+) T cell epitopes from the HSV-1 gB amino acid sequence. Six of these epitopes exhibited high-affinity binding to HLA-A*02:01 molecules. In 10 sequentially studied HLA-A*02:01-positive, HSV-1-seropositive ASYMP individuals, the most frequent, robust, and polyfunctional CD8(+) T cell responses, as assessed by a combination of tetramer, IFN-γ-ELISPOT, CFSE proliferation, CD107a/b cytotoxic degranulation, and multiplex cytokine assays, were directed mainly against epitopes gB342-350 and gB561-569. In contrast, in 10 HLA-A*02:01-positive, HSV-1-seropositive symptomatic (SYMP) individuals (with a history of numerous episodes of recurrent clinical herpes disease) frequent, but less robust, CD8(+) T cell responses were directed mainly against nonoverlapping epitopes (gB183-191 and gB441-449). ASYMP individuals had a significantly higher proportion of HSV-gB-specific CD8(+) T cells expressing CD107a/b degranulation marker and producing effector cytokines IL-2, IFN-γ, and TNF-α than did SYMP individuals. Moreover, immunization of a novel herpes-susceptible HLA-A*02:01 transgenic mouse model with ASYMP epitopes, but not with SYMP epitopes, induced strong CD8(+) T cell-dependent protective immunity against ocular herpes infection and disease. These findings should guide the development of a safe and effective T cell-based herpes vaccine.

CD4 T cell responses in latent and chronic viral infections

The spectrum of tasks which is fulfilled by CD4 T cells in the setting of viral infections is large, ranging from support of CD8 T cells and humoral immunity to exertion of direct antiviral effector functions. While our knowledge about the differentiation pathways, plasticity, and memory of CD4 T cell responses upon acute infections or immunizations has significantly increased during the past years, much less is still known about CD4 T cell differentiation and their beneficial or pathological functions during persistent viral infections. In this review we summarize current knowledge about the differentiation, direct or indirect antiviral effector functions, and the regulation of virus-specific CD4 T cells in the setting of persistent latent or active chronic viral infections with a particular emphasis on herpes virus infections for the former and chronic lymphocytic choriomeningitis virus infection for the latter.

Activation of monocytic cells by immunostimulatory lipids conjugated to peptide antigens

Bacterial derived lipoproteins constitute potent macrophage activators in vivo and are effective stimuli, enhancing the immune response especially with respect to low or non-immunogenic compounds. In the present study we have prepared branched lipopeptide constructs in which different (B- and T-cell) epitopes of Herpes simplex virus type 1, derived from glycoproteins B (gB) and D (gD), are linked to a synthetic lipid core. The ability of the lipid core peptide (LCP) constructs (LCP-gB and LCP-gD) to induce cytokine expression and activate the mitogen-activated protein kinase cascade has been evaluated and compared with the behaviour of the isolated epitopes and the lipid core. In this respect, the use of LCP technology coupled with the use of three different gB or gD peptide epitopes in the same branched constructs could represent an interesting approach in order to obtain efficient delivery systems in the development of a synthetic multiepitopic vaccine for the prevention of viral infections.

Broad and cross-clade CD4+ T-cell responses elicited by a DNA vaccine encoding highly conserved and promiscuous HIV-1 M-group consensus peptides

T-cell based vaccine approaches have emerged to counteract HIV-1/AIDS. Broad, polyfunctional and cytotoxic CD4⁺ T-cell responses have been associated with control of HIV-1 replication, which supports the inclusion of CD4⁺ T-cell epitopes in vaccines. A successful HIV-1 vaccine should also be designed to overcome viral genetic diversity and be able to confer immunity in a high proportion of immunized individuals from a diverse HLA-bearing population. In this study, we rationally designed a multiepitopic DNA vaccine in order to elicit broad and cross-clade CD4⁺ T-cell responses against highly conserved and promiscuous peptides from the HIV-1 M-group consensus sequence. We identified 27 conserved, multiple HLA-DR-binding peptides in the HIV-1 M-group consensus sequences of Gag, Pol, Nef, Vif, Vpr, Rev and Vpu using the TEPITOPE algorithm. The peptides bound in vitro to an average of 12 out of the 17 tested HLA-DR molecules and also to several molecules such as HLA-DP, -DQ and murine IA^b and IA^d. Sixteen out of the 27 peptides were recognized by PBMC from patients infected with different HIV-1 variants and 72% of such patients recognized at least 1 peptide. Immunization with a DNA vaccine (HIVBr27) encoding the identified peptides elicited IFN-γ secretion against 11 out of the 27 peptides in BALB/c mice; CD4⁺ and CD8⁺ T-cell proliferation was observed against 8 and 6 peptides, respectively. HIVBr27 immunization elicited cross-clade T-cell responses against several HIV-1 peptide variants. Polyfunctional CD4⁺ and CD8⁺ T cells, able to simultaneously proliferate and produce IFN-γ and TNF-α, were also observed. This vaccine concept may cope with HIV-1 genetic diversity as well as provide increased population coverage, which are desirable features for an efficacious strategy against HIV-1/AIDS.

The herpes simplex virus type 1 latency-associated transcript inhibits phenotypic and functional maturation of dendritic cells

We recently found that the herpes simplex virus-1 (HSV-1) latency-associated transcript (LAT) results in exhaustion of virus-specific CD8⁺ T cells in latently-infected trigeminal ganglia (TG). In this study we sought to determine if this impairment may involve LAT directly and/or indirectly interfering with DC maturation. We found that a small number of HSV-1 antigen-positive DCs are present in the TG of latently-infected CD11c/eYFP mice; however, this does not imply that these DCs are acutely or latently infected. Some CD8⁺ T cells are adjacent to DCs, suggesting possible interactions. It has previously been shown that wild-type HSV-1 interferes with DC maturation. Here we show for the first time that this is associated with LAT expression, since compared to LAT⁻ virus: (1) LAT⁺ virus interfered with expression of MHC class I and the co-stimulatory molecules CD80 and CD86 on the surface of DCs; (2) LAT⁺ virus impaired DC production of the proinflammatory cytokines IL-6, IL-12, and TNF-α; and (3) DCs infected in vitro with LAT⁺ virus had significantly reduced the ability to stimulate HSV-specific CD8⁺ T cells. While a similar number of DCs was found in LAT⁺ and LAT⁻ latently-infected TG of CD11c/eYFP transgenic mice, more HSV-1 Ag-positive DCs and more exhausted CD8 T cells were seen with LAT⁺ virus. Consistent with these findings, HSV-specific cytotoxic CD8⁺ T cells in the TG of mice latently-infected with LAT⁺ virus produced less IFN-γ and TNF-α than those from TG of LAT⁻-infected mice. Together, these results suggest a novel immune-evasion mechanism whereby the HSV-1 LAT increases the number of HSV-1 Ag-positive DCs in latently-infected TG, and interferes with DC phenotypic and functional maturation. The effect of LAT on TG-resident DCs may contribute to the reduced function of HSV-specific CD8⁺ T cells in the TG of mice latently infected with LAT⁺ virus.

Future of an "Asymptomatic" T-cell Epitope-Based Therapeutic Herpes Simplex Vaccine

Considering the limited success of the recent herpes clinical vaccine trial [1], new vaccine strategies are needed. Infections with herpes simplex virus type 1 and type 2 (HSV-1 & HSV-2) in the majority of men and women are usually asymptomatic and results in lifelong viral latency in neurons of sensory ganglia (SG). However, in a minority of men and women HSV spontaneous reactivation can cause recurrent disease (i.e., symptomatic individuals). Our recent findings show that T cells from symptomatic and asymptomatic men and women (i.e. those with and without recurrences, respectively) recognize different herpes epitopes. This finding breaks new ground and opens new doors to assess a new vaccine strategy: mucosal immunization with HSV-1 & HSV-2 epitopes that induce strong in vitro CD4 and CD8 T cell responses from PBMC derived from asymptomatic men and women (designated here as "asymptomatic" protective epitopes") could boost local and systemic "natural" protective immunity, induced by wild-type infection. Here we highlight the rationale and the future of our emerging "asymptomatic" T cell epitope-based mucosal vaccine strategy to decrease recurrent herpetic disease.

Vaxfectin-adjuvanted plasmid DNA vaccine improves protection and immunogenicity in a murine model of genital herpes infection

The herpes simplex type 2 (HSV-2) envelope glycoprotein (gD2) was evaluated as a potential antigen candidate for a plasmid DNA (pDNA)-based HSV-2 vaccine. The pDNA was formulated with Vaxfectin, a cationic lipid-based adjuvant, and tested in a murine HSV-2 lethal challenge model. gD2 was expressed as full-length (FL) and secreted (S) gD2 forms. A 0.1 µg pDNA dose was tested to distinguish treatment conditions for survival and a 100 µg pDNA dose was tested to distinguish treatment conditions for reduction in vaginal and latent HSV-2 copies. Vaxfectin-formulated gD2 pDNA significantly increased serum IgG titres and survival for both FL gD2 and S gD2 compared with gD2 pDNA alone. Mice immunized with FL gD2 formulated with Vaxfectin showed reduction in vaginal and dorsal root ganglia (DRG) HSV-2 copies. The stringency of this protection was further evaluated by testing Vaxfectin-formulated FL gD2 pDNA at a high 500 LD(50) inoculum. At this high viral challenge, the 0.1 µg dose of FL gD2 Vaxfectin-formulated pDNA yielded 80 % survival compared with no survival for FL gD2 pDNA alone. Vaxfectin-formulated FL gD2 pDNA, administered at a 100 µg pDNA dose, significantly reduced HSV-2 DNA copy number, compared with FL gD2 DNA alone. In addition, 40 % of mice vaccinated with adjuvanted FL pDNA had no detectable HSV-2 viral genomes in the DRG, whereas all mice vaccinated with gD2 pDNA alone were positive for HSV-2 viral genomes. These results show the potential contribution of Vaxfectin-gD2 pDNA to a future multivalent HSV-2 vaccine.

Immunodominant "asymptomatic" herpes simplex virus 1 and 2 protein antigens identified by probing whole-ORFome microarrays with serum antibodies from seropositive asymptomatic versus symptomatic individuals

Herpes simplex virus 1 (HSV-1) and HSV-2 are medically significant pathogens. The development of an effective HSV vaccine remains a global public health priority. HSV-1 and HSV-2 immunodominant "asymptomatic" antigens (ID-A-Ags), which are strongly recognized by B and T cells from seropositive healthy asymptomatic individuals, may be critical to be included in an effective immunotherapeutic HSV vaccine. In contrast, immunodominant "symptomatic" antigens (ID-S-Ags) may exacerbate herpetic disease and therefore must be excluded from any HSV vaccine. In the present study, proteome microarrays of 88 HSV-1 and 84 HSV-2 open reading frames(ORFs) (ORFomes) were constructed and probed with sera from 32 HSV-1-, 6 HSV-2-, and 5 HSV-1/HSV-2-seropositive individuals and 47 seronegative healthy individuals (negative controls). The proteins detected in both HSV-1 and HSV-2 proteome microarrays were further classified according to their recognition by sera from HSV-seropositive clinically defined symptomatic (n = 10) and asymptomatic (n = 10) individuals. We found that (i) serum antibodies recognized an average of 6 ORFs per seropositive individual; (ii) the antibody responses to HSV antigens were diverse among HSV-1- and HSV-2-seropositive individuals; (iii) panels of 21 and 30 immunodominant antigens (ID-Ags) were identified from the HSV-1 and HSV-2 ORFomes, respectively, as being highly and frequently recognized by serum antibodies from seropositive individuals; and (iv) interestingly, four HSV-1 and HSV-2 cross-reactive asymptomatic ID-A-Ags, US4, US11, UL30, and UL42, were strongly and frequently recognized by sera from 10 of 10 asymptomatic patients but not by sera from 10 of 10 symptomatic patients (P < 0.001). In contrast, sera from symptomatic patients preferentially recognized the US10 ID-S-Ag (P < 0.001). We have identified previously unreported immunodominant HSV antigens, among which were 4 ID-A-Ags and 1 ID-S-Ag. These newly identified ID-A-Ags could lead to the development of an efficient "asymptomatic" vaccine against ocular, orofacial, and genital herpes.

Discovery of potential diagnostic and vaccine antigens in herpes simplex virus 1 and 2 by proteome-wide antibody profiling

Routine serodiagnosis of herpes simplex virus (HSV) infections is currently performed using recombinant glycoprotein G (gG) antigens from herpes simplex virus 1 (HSV-1) and HSV-2. This is a single-antigen test and has only one diagnostic application. Relatively little is known about HSV antigenicity at the proteome-wide level, and the full potential of mining the antibody repertoire to identify antigens with other useful diagnostic properties and candidate vaccine antigens is yet to be realized. To this end we produced HSV-1 and -2 proteome microarrays in Escherichia coli and probed them against a panel of sera from patients serotyped using commercial gG-1 and gG-2 (gGs for HSV-1 and -2, respectively) enzyme-linked immunosorbent assays. We identified many reactive antigens in both HSV-1 and -2, some of which were type specific (i.e., recognized by HSV-1- or HSV-2-positive donors only) and others of which were nonspecific or cross-reactive (i.e., recognized by both HSV-1- and HSV-2-positive donors). Both membrane and nonmembrane virion proteins were antigenic, although type-specific antigens were enriched for membrane proteins, despite being expressed in E. coli.

Current trends in negative immuno-synergy between two sexually transmitted infectious viruses: HIV-1 and HSV-1/2

In the current era of effective anti-retroviral therapy, immuno-compromised patients with HIV-1 infection do live long enough to suffer diseases caused by many opportunistic infections, such as herpes simplex virus type 1 and/or type 2 (HSV-1/2). An estimated two-third of the 40 million individuals that have contracted HIV-1 worldwide are co-infected with HSV-1/2 viruses, the causative agents of ocular oro-facial and genital herpes. The highest prevalence of HIV and HSV-1/2 infections are confined to the same regions of Sub-Saharan Africa. HSV-1/2 infections affect HIV-1 immunity, and vice versa. While important research gains have been made in understanding herpes and HIV immunity, the cellular and molecular mechanisms underlying the crosstalk between HSV-1/2 and HIV co-infection remain to be fully elucidated. Understanding the mechanisms behind the apparent HSV/HIV negative immuno-synergy maybe the key to successful HSV and HIV vaccines; both are currently unavailable. An effective herpes immunotherapeutic vaccine would in turn - indirectly - contribute in reducing HIV epidemic. The purpose of this review is: (i) to summarize the current trends in understanding the negative immuno-crosstalk between HIV and HSV-1/2 infections; and (ii) to discuss the possibility of developing a novel mucosal herpes immunotherapeutic strategy or even a combined or chimeric immunotherapeutic vaccine that simultaneously targets HIV and HSV-1/2 infections. These new trends in immunology of HSV-1/2 and HIV co-infections should become part of current efforts in preventing sexually transmitted infections. The alternative is needed to balance the ethical and financial concerns associated with the rising number of unsuccessful mono-valent clinical vaccine trials.

Immunology in the Clinic Review Series; focus on host responses: T cell responses to herpes simplex viruses

Herpes virus infections are chronic and co-exist with acquired immune responses that generally prevent severe damage to the host, while allowing periodic shedding of virus and maintenance of its transmission in the community. Herpes simplex viruses type 1 and 2 (HSV-1, HSV-2) are typical in this regard and are representative of the viral subfamily Alphaherpesvirinae, which has a tropism for neuronal and epithelial cells. This review will emphasize recent progress in decoding the physiologically important CD8(+) and CD4(+) T cell responses to HSV in humans. The expanding data set is discussed in the context of the search for an effective HSV vaccine as therapy for existing infections and to prevent new infections.

HIV-1 infection impairs HSV-specific CD4(+) and CD8(+) T-cell response by reducing Th1 cytokines and CCR5 ligand secretion

BACKGROUND

The concept of HIV-1/HSV-negative immunosynergy has recently come to light, which leads us to explore the impact of HIV-1 infection on HSV-specific T-cell immunity.

METHODS

: A combination of interferon (IFN)-γ ELISpot and Luminex-based multicytokine profiling assays was used to compare, in a cross-sectional study, the HSV-specific CD4 and CD8 T-cell responses between 20 HIV-1/HSV-coinfected and 12 HIV-1-uninfected/HSV-infected individuals after in vitro restimulation with HSV glycoprotein D (gD) peptide epitopes.

RESULTS

In response to CD4 and CD8 gD peptide epitopes, mean value (±standard errors of the mean) of the different IFN-γ-secreting T cells (ISC) means was significantly reduced in HIV-1/HSV-coinfected individuals (70 ISC ± 10 and 60 ISC ± 8/10 cells) compared with HIV-1-uninfected/HSV-infected individuals (280 ISC ± 25 and 234 ISC ± 23/10 cells, both P < 0.001). After stimulation with the immunodominant CD4 gD and CD8 gD peptide epitopes, the Th1 cytokine and CCR5 ligand secretions were decreased in the HIV-1-infected group although Th17 cytokines increased. The mean concentration of interleukin (IL)-2, IFN-γ, the IFN-γ-induced protein 10 kDa, and the monokine induced by IFN-γ was correlated to the mean concentration of macrophage inflammatory proteins (MIP-1α, MIP-1β), RANTES and Eotaxin (ρ = 0.56, P = 0.02 and ρ = 0.52, P = 0.03).

CONCLUSIONS

HIV-1 infection impairs both the number and function of HSV-specific T cells. The downregulation of Th1 cytokines and CCR5 ligands in HIV-1/HSV-coinfected individuals may further facilitate both HSV reactivations and HIV-1 replication.

The Role of Plasmacytoid Dendritic Cells in Innate and Adaptive Immune Responses against Alpha Herpes Virus Infections

In 1999, two independent groups identified plasmacytoid dendritic cells (PDC) as major type I interferon- (IFN-) producing cells in the blood. Since then, evidence is accumulating that PDC are a multifunctional cell population effectively coordinating innate and adaptive immune responses. This paper focuses on the role of different immune cells and their interactions in the surveillance of alpha herpes virus infections, summarizes current knowledge on PDC surface receptors and their role in direct cell-cell contacts, and develops a risk factor model for the clinical implications of herpes simplex and varicella zoster virus reactivation. Data from studies involving knockout mice and cell-depletion experiments as well as human studies converge into a "spider web", in which the direct and indirect crosstalk between many cell populations tightly controls acute, latent, and recurrent alpha herpes virus infections. Notably, cells involved in innate immune regulations appear to shape adaptive immune responses more extensively than previously thought.

A DNA vaccine encoding multiple HIV CD4 epitopes elicits vigorous polyfunctional, long-lived CD4+ and CD8+ T cell responses

T-cell based vaccines against HIV have the goal of limiting both transmission and disease progression by inducing broad and functionally relevant T cell responses. Moreover, polyfunctional and long-lived specific memory T cells have been associated to vaccine-induced protection. CD4⁺ T cells are important for the generation and maintenance of functional CD8⁺ cytotoxic T cells. We have recently developed a DNA vaccine encoding 18 conserved multiple HLA-DR-binding HIV-1 CD4 epitopes (HIVBr18), capable of eliciting broad CD4⁺ T cell responses in multiple HLA class II transgenic mice. Here, we evaluated the breadth and functional profile of HIVBr18-induced immune responses in BALB/c mice. Immunized mice displayed high-magnitude, broad CD4⁺/CD8⁺ T cell responses, and 8/18 vaccine-encoded peptides were recognized. In addition, HIVBr18 immunization was able to induce polyfunctional CD4⁺ and CD8⁺ T cells that proliferate and produce any two cytokines (IFNγ/TNFα, IFNγ/IL-2 or TNFα/IL-2) simultaneously in response to HIV-1 peptides. For CD4⁺ T cells exclusively, we also detected cells that proliferate and produce all three tested cytokines simultaneously (IFNγ/TNFα/IL-2). The vaccine also generated long-lived central and effector memory CD4⁺ T cells, a desirable feature for T-cell based vaccines. By virtue of inducing broad, polyfunctional and long-lived T cell responses against conserved CD4⁺ T cell epitopes, combined administration of this vaccine concept may provide sustained help for CD8⁺ T cells and antibody responses- elicited by other HIV immunogens.

CD4+ T cells are not required for the induction of dengue virus-specific CD8+ T cell or antibody responses but contribute to protection after vaccination

The contribution of T cells to the host response to dengue virus (DENV) infection is not well understood. We previously demonstrated a protective role for CD8(+) T cells during primary DENV infection using a mouse-passaged DENV strain and IFN-α/βR(-/-) C57BL/6 mice, which are susceptible to DENV infection. In this study, we examine the role of CD4(+) T cells during primary DENV infection. Four I-A(b)-restricted epitopes derived from three of the nonstructural DENV proteins were identified. CD4(+) T cells expanded and were activated after DENV infection, with peak activation occurring on day 7. The DENV-specific CD4(+) T cells expressed intracellular IFN-γ, TNF, IL-2, and CD40L, and killed peptide-pulsed target cells in vivo. Surprisingly, depletion of CD4(+) T cells before DENV infection had no effect on viral loads. Consistent with this observation, CD4(+) T cell depletion did not affect the DENV-specific IgG or IgM Ab titers or their neutralizing activity, or the DENV-specific CD8(+) T cell response. However, immunization with the CD4(+) T cell epitopes before infection resulted in significantly lower viral loads. Thus, we conclude that whereas CD4(+) T cells are not required for controlling primary DENV infection, their induction by immunization can contribute to viral clearance. These findings suggest inducing anti-DENV CD4(+) T cell responses by vaccination may be beneficial.

Identification and characterization of Th cell epitopes in MrkD adhesin of Klebsiella pneumoniae

In this study, we identified the Th epitopes in MrkD of Klebsiella pneumoniae, an excellent vaccine candidate antigen. By using the RANKPEP prediction algorithm, we have identified and characterized three Th epitopes within the MrkD antigen, which can be recognized by CD4+ T cells from BALB/c (H-2(d)) mice. They were M(221-235), M(175-189), and M(264-278). These epitopes have important value for studying the immune response of K. pneumoniae infection and for designing effective vaccine against K. pneumoniae.

A novel HLA (HLA-A*0201) transgenic rabbit model for preclinical evaluation of human CD8+ T cell epitope-based vaccines against ocular herpes

We introduced a novel humanized HLA-A*0201 transgenic (HLA Tg) rabbit model to assess the protective efficacy of a human CD8(+) T cell epitope-based vaccine against primary ocular herpes infection and disease. Each of the three immunodominant human CD8(+) T cell peptide epitopes from HSV-1 glycoprotein D (gD(53-61), gD(70-78), and gD(278-286)) were joined with a promiscuous human CD4(+) T cell peptide epitope (gD(49-82)) to construct three separate pairs of CD4-CD8 peptides. Each CD4-CD8 peptide pair was then covalently linked to an N(epsilon)-palmitoyl-lysine residue via a functional base lysine amino group to construct CD4-CD8 lipopeptides. HLA Tg rabbits were immunized s.c. with a mixture of the three CD4-CD8 HSV-1 gD lipopeptides. The HSV-gD-specific T cell responses induced by the mixture of CD4-CD8 lipopeptide vaccine and the protective efficacy against acute virus replication and ocular disease were determined. Immunization induced HSV-gD(49-82)-specific CD4(+) T cells in draining lymph node (DLN); induced HLA-restricted HSV-gD(53-61), gD(70-78), and gD(278-286)-specific CD8(+) T cells in DLN, conjunctiva, and trigeminal ganglia and reduced HSV-1 replication in tears and corneal eye disease after ocular HSV-1 challenge. In addition, the HSV-1 epitope-specific CD8(+) T cells induced in DLNs, conjunctiva, and the trigeminal ganglia were inversely proportional with corneal disease. The humanized HLA Tg rabbits appeared to be a useful preclinical animal model for investigating the immunogenicity and protective efficacy of human CD8(+) T cell epitope-based prophylactic vaccines against ocular herpes. The relevance of HLA Tg rabbits for future investigation of human CD4-CD8 epitope-based therapeutic vaccines against recurrent HSV-1 is discussed.

The virion host shut-off (vhs) protein blocks a TLR-independent pathway of herpes simplex virus type 1 recognition in human and mouse dendritic cells

Molecular pathways underlying the activation of dendritic cells (DCs) in response to Herpes Simplex Virus type 1 (HSV-1) are poorly understood. Removal of the HSV virion host shut-off (vhs) protein relieves a block to DC activation observed during wild-type infection. In this study, we utilized a potent DC stimulatory HSV-1 recombinant virus lacking vhs as a tool to investigate the mechanisms involved in the activation of DCs by HSV-1. We report that the release of pro-inflammatory cytokines by conventional DC (cDC) during HSV-1 infection is triggered by both virus replication-dependent and replication-independent pathways. Interestingly, while vhs is capable of inhibiting the release of cytokines during infection of human and mouse cDCs, the secretion of cytokines by plasmacytoid DC (pDC) is not affected by vhs. These data prompted us to postulate that infection of cDCs by HSV triggers a TLR independent pathway for cDC activation that is susceptible to blockage by the vhs protein. Using cDCs isolated from mice deficient in both the TLR adaptor protein MyD88 and TLR3, we show that HSV-1 and the vhs-deleted virus can activate cDCs independently of TLR signaling. In addition, virion-associated vhs fails to block cDC activation in response to treatment with TLR agonists, but it efficiently blocked cDC activation triggered by the paramyxoviruses Sendai Virus (SeV) and Newcastle Disease Virus (NDV). This block to SeV- and NDV-induced activation of cDC resulted in elevated SeV and NDV viral gene expression indicating that infection with HSV-1 enhances the cell's susceptibility to other pathogens through the action of vhs. Our results demonstrate for the first time that a viral protein contained in the tegument of HSV-1 can block the induction of DC activation by TLR-independent pathways of viral recognition.

Nasolacrimal duct closure modulates ocular mucosal and systemic CD4(+) T-cell responses induced following topical ocular or intranasal immunization

Both topical ocular and topical intranasal immunizations have been reported to stimulate the ocular mucosal immune system (OMIS) and the systemic immune system. Nasolacrimal ducts (NLDs) are the connecting bridges between the OMIS and nasal cavity-associated lymphoid tissue (NALT). These ducts drain topical ocularly administrated solutions into the inferior meatus of the nose to reach the NALT. Inversely, NLDs also drain intranasally administrated solutions to the mucosal surface of the eye and thus the OMIS. This unique anatomical connection between the OMIS and NALT systems provoked us to test whether the OMIS and NALT are immunologically interdependent. In this report, we show that both topical ocular administration and topical intranasal administration of a mixture of immunodominant CD4(+) T-cell epitope peptides from herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) emulsified with the CpG(2007) mucosal adjuvant are capable of inducing local (in conjunctiva) as well as systemic (in spleen) HSV-peptide-specific CD4(+) T-cell responses. Interestingly, surgical closure of NLDs did not significantly alter local ocular mucosal CD4(+) T-cell responses induced following topical ocular immunization but did significantly enhance systemic CD4(+) T-cell responses (as measured by both T-cell proliferation and gamma interferon (IFN-gamma) production; P < 0.005). In contrast, NLD closure significantly decreased ocular mucosal, but not systemic, CD4(+) T-cell responses following intranasal administration of the same vaccine solution (P < 0.001). The study suggests that NALT and the OMIS are immunologically interconnected.

Prospects for Developing an Effective Vaccine Against Ocular Herpes Simplex Virus Infection

One of the hallmarks of herpes simplex virus (HSV) infection is the establishment of a lifelong latent infection accompanied by periods of recurrent disease. Primary HSV infections or repeated clinical recurrences do not elicit immune responses capable of completely preventing recurrences of endogenous virus. It is therefore questionable if vaccination approaches that seek to mimic the immune response to natural infection will reduce infection or disease due to an exogenous viral challenge. Approaches to the induction of protective responses by altering or enhancing both innate and adaptive immunity, using novel vaccines specifically tested in models of HSV infections of the eye, such as recombinant viral vaccine vectors and DNA vaccines, are detailed in this review.

Potent adjuvant activity of cationic liposome-DNA complexes for genital herpes vaccines

Development of a herpes simplex virus (HSV) vaccine is a priority because these infections are common. It appears that potent adjuvants will be required to augment the immune response to subunit HSV vaccines. Therefore, we evaluated cationic liposome-DNA complexes (CLDC) as an adjuvant in a mouse model of genital herpes. Using a whole-virus vaccine (HVAC), we showed that the addition of CLDC improved antibody responses compared to vaccine alone. Most important, CLDC increased survival, reduced symptoms, and decreased vaginal virus replication compared to vaccine alone or vaccine administered with monophosphoryl lipid A (MPL) plus trehalose dicorynomycolate (TDM) following intravaginal challenge of mice. When CLDC was added to an HSV gD2 vaccine, it increased the amount of gamma interferon that was produced from splenocytes stimulated with gD2 compared to the amount produced with gD2 alone or with MPL-alum. The addition of CLDC to the gD2 vaccine also improved the outcome following vaginal HSV type 2 challenge compared to vaccine alone and was equivalent to vaccination with an MPL-alum adjuvant. CLDC appears to be a potent adjuvant for HSV vaccines and should be evaluated further.

A genital tract peptide epitope vaccine targeting TLR-2 efficiently induces local and systemic CD8+ T cells and protects against herpes simplex virus type 2 challenge

The next generation of needle-free mucosal vaccines is being rationally designed according to rules that govern the way in which the epitopes are recognized by and stimulate the genital mucosal immune system. We hypothesized that synthetic peptide epitopes extended with an agonist of Toll-like receptor 2 (TLR-2), that are abundantly expressed by dendritic and epithelial cells of the vaginal mucosa, would lead to induction of protective immunity against genital herpes. To test this hypothesis, we intravaginally (IVAG) immunized wild-type B6, TLR-2 (TLR2(-/-)) or myeloid differentiation factor 88 deficient (MyD88(-/-)) mice with a herpes simplex virus type 2 (HSV-2) CD8+ T-cell peptide epitope extended by a palmitic acid moiety (a TLR-2 agonist). IVAG delivery of the lipopeptide generated HSV-2-specific memory CD8+ cytotoxic T cells both locally in the genital tract draining lymph nodes and systemically in the spleen. Moreover, lipopeptide-immunized TLR2(-/-) and MyD88(-/-) mice developed significantly less HSV-specific CD8+ T-cell response, earlier death, faster disease progression, and higher vaginal HSV-2 titers compared to lipopeptide-immunized wild-type B6 mice. IVAG immunization with self-adjuvanting lipid-tailed peptides appears to be a novel mucosal vaccine approach, which has attractive practical and immunological features.

Immunodominant epitopes in herpes simplex virus type 2 glycoprotein D are recognized by CD4 lymphocytes from both HSV-1 and HSV-2 seropositive subjects

In human recurrent cutaneous herpes simplex, there is a sequential infiltrate of CD4 and then CD8 lymphocytes into lesions. CD4 lymphocytes are the major producers of the key cytokine IFN-gamma in lesions. They recognize mainly structural proteins and especially glycoproteins D and B (gD and gB) when restimulated in vitro. Recent human vaccine trials using recombinant gD showed partial protection of HSV seronegative women against genital herpes disease and also, in placebo recipients, showed protection by prior HSV1 infection. In this study, we have defined immunodominant peptide epitopes recognized by 8 HSV1(+) and/or 16 HSV2(+) patients using (51)Cr-release cytotoxicity and IFN-gamma ELISPOT assays. Using a set of 39 overlapping 20-mer peptides, more than six immunodominant epitopes were defined in gD2 (two to six peptide epitopes were recognized for each subject). Further fine mapping of these responses for 4 of the 20-mers, using a panel of 9 internal 12-mers for each 20-mers, combined with MHC II typing and also direct in vitro binding assay of these peptides to individual DR molecules, showed more than one epitope per 20-mers and promiscuous binding of individual 20-mers and 12-mers to multiple DR types. All four 20-mer peptides were cross-recognized by both HSV1(+)/HSV2(-) and HSV1(-)/HSV2(+) subjects, but the sites of recognition differed within the 20-mers where their sequences were divergent. This work provides a basis for CD4 lymphocyte cross-recognition of gD2 and possibly cross-protection observed in previous clinical studies and in vaccine trials.

In silico prediction and immunological validation of common HLA-DRB1-restricted T cell epitopes of Candida albicans secretory aspartyl proteinase 2

ABSTRACT Sap2 is the most abundant virulence factor expressed during Candida infection, and the principal protein known to induce antibody response during Candida infection in humans. Its role in T-cell activation however, has not yet been determined. Sequence analysis revealed that Sap2 contains two variable regions: Var1 and Var2. Computational predictions by the Hotspot Hunter program identified that Var1 contains three candidate T-cell epitopes, whereas Var2 contains four. Thirty-nine overlapping peptides of Sap2 were then synthesized, and tested for their ability to induce proliferation of PBMC from 12 donors. Peptides P11, P17 and P31 exhibited significantly higher proliferative indices when compared with those of other peptides or controls. P17 and P31 are located in the areas of prediction, while P11 is not. There were other peptides outside the prediction areas that could stimulate PBMC proliferation at low levels. Nevertheless, the proliferative noise caused by such peptides was ruled out by IL-2 ELISpot analysis. Only P17 and P31 were shown to induce clonal proliferation of IFN-gamma producing lymphocytes, suggesting that these two peptides contain T cell epitopes. P11, which stimulated IL-2 producing clones, contains a known B-cell epitope. Interestingly, P17 and P31 elicited both Th1 and Th2 cell responses with significant numbers of IL-13 secreting clones in response to stimulation. Taken together, the computer-based T cell epitope prediction method could identify the immunogenic T cell epitopes of C. albicans Sap2 that promiscuously bind to the HLA-DRB1 supertype.

Asymptomatic human CD4+ cytotoxic T-cell epitopes identified from herpes simplex virus glycoprotein B

The identification of "asymptomatic" (i.e., protective) epitopes recognized by T cells from herpes simplex virus (HSV)-seropositive healthy individuals is a prerequisite for an effective vaccine. Using the PepScan epitope mapping strategy, a library of 179 potential peptide epitopes (15-mers overlapping by 10 amino acids) was identified from HSV type 1 (HSV-1) glycoprotein B (gB), an antigen that induces protective immunity in both animal models and humans. Eighteen groups (G1 to G18) of 10 adjacent peptides each were first screened for T-cell antigenicity in 38 HSV-1-seropositive but HSV-2-seronegative individuals. Individual peptides within the two immunodominant groups (i.e., G4 and G14) were further screened with T cells from HLA-DR-genotyped and clinically defined symptomatic (n = 10) and asymptomatic (n = 10) HSV-1-seropositive healthy individuals. Peptides gB(161-175) and gB(166-180) within G4 and gB(661-675) within G14 recalled the strongest HLA-DR-dependent CD4(+) T-cell proliferation and gamma interferon production. gB(166-180), gB(661-675), and gB(666-680) elicited ex vivo CD4(+) cytotoxic T cells (CTLs) that lysed autologous HSV-1- and vaccinia virus (expressing gB)-infected lymphoblastoid cell lines. Interestingly, gB(166-180) and gB(666-680) peptide epitopes were strongly recognized by CD4(+) T cells from 10 of 10 asymptomatic patients but not by CD4(+) T cells from 10 of 10 symptomatic patients (P < 0.0001; analysis of variance posttest). Inversely, CD4(+) T cells from symptomatic patients preferentially recognized gB(661-675) (P < 0.0001). Thus, we identified three previously unrecognized CD4(+) CTL peptide epitopes in HSV-1 gB. Among these, gB(166-180) and gB(666-680) appear to be "asymptomatic" peptide epitopes and therefore should be considered in the design of future herpes vaccines.

Immune responses of mice with different genetic backgrounds to improved multiepitope, multitarget malaria vaccine candidate antigen FALVAC-1A

FALVAC-1A is a second-generation multitarget, multiepitope synthetic candidate vaccine against Plasmodium falciparum, incorporating elements designed to yield a stable and immunogenic molecule. Characteristics of the immunogenicity of FALVAC-1A were evaluated in congenic (H-2(b), H-2(k), and H-2(d)) and outbred strains of mice. The influences of four adjuvants (aluminum phosphate, QS-21, Montanide ISA-720, and copolymer CRL-1005) on different aspects of the immune response were also assessed. FALVAC-1A generated strong antibody responses in all mouse strains. The highest mean enzyme-linked immunosorbent assay (ELISA) antibody concentrations against FALVAC-1A were observed in the outbred ICR mice, followed by B10.BR, B10.D2, and C57BL/6 mice, though this order varied for the different adjuvants, with no statistical differences between mouse strains. In all mouse strains, the highest anti-FALVAC-1A antibody titers in ELISAs were induced by FALVAC-1A in copolymer and ISA-720 formulations, followed by QS-21 and AlPO4. These antibodies were of all four subclasses, though immunoglobulin G1 (IgG1) predominated, with the exception of FALVAC-1A with the QS-21 adjuvant, which induced predominantly IgG2c responses. Both sporozoites and blood stages of P. falciparum were recognized by anti-FALVAC-1A sera in the immunofluorescence assay. In addition to antibody, cellular immune responses were detected; these responses were studied by examining spleen cells producing gamma interferon and interleukin-4 in enzyme-linked immunospot assays. In summary, FALVAC-1A was found to be highly immunogenic and elicited functionally relevant antibodies that can recognize sporozoites and blood-stage parasites in diverse genetic backgrounds.