BACKGROUND:First discovered in 1999 in Malaysia, Nipah virus (NiV) causes yearly outbreaks throughout south and southeast Asia with associated mortality rates of 40-75%. Due to the structural and sequence similarities between the NiV and Hendra virus (HeV) attachment G glycoproteins, and the extensive extant evidence of the ability of a recombinant soluble glycoprotein G (HeV-sG) to provide heterologous cross-protective immunity when used as vaccine (HeV-sG-V), this study aimed to evaluate HeV-sG-V for safety, tolerability, and immunogenicity against NiV. METHODS:We conducted a phase 1, single-centre, randomised, observer-blind, placebo-controlled study. Eligible participants were aged 18-49 years, healthy, and not pregnant; participants were ineligible if they were immunocompromised, had received blood products within 6 months of enrolment, had potential exposure to NiV or HeV, or had known allergies to components of the vaccine. Participants were randomly assigned in a 5:1 ratio to receive either one or two doses of the vaccine candidate (at 10 μg for the first cohort; 30 μg at days 1 and either days 8 or 29 for cohort 2; and 100 μg with the same timing for cohort 3) or placebo. The primary endpoints were solicited and unsolicited adverse events, clinically significant laboratory test result abnormalities, medically attended adverse events, and serious adverse events. Secondary endpoints were serum IgG binding via ELISA and neutralising antibody responses against prototypical NiV Bangladesh (NiVB) and NiV Malaysia (NiVM) reporter viruses. FINDINGS:Between Feb 24, 2020, and Oct 6, 2021, 268 participants were screened, and 192 were enrolled. 173 (90%) participants met the per-protocol criteria. Mild-to-moderate injection site pain was the most commonly reported adverse event. No serious adverse events, hospitalisations, or deaths were reported. The immune response to HeV-sG-V was dose-dependent; a single administration was not sufficiently immunogenic, whereas two administrations were immunogenic, with the highest response rates observed among vaccinees that received two administrations of the 100 μg HeV-sG-V 28 days apart (neutralising antibody geometric mean titres rose dramatically 7 days after the second investigational product dose, reaching 1485·6 (990·5-2228·1) and 2581·9 (147·1-3194·2) for NiVB and NiVM, respectively). INTERPRETATION:All three doses and regimens of HeV-sG-V had a tolerable risk profile and were able to induce an immune response. The induction of antibodies within 1 month of vaccination, along with the persistence afforded by two dosages, suggests the vaccine candidate has potential for reactive outbreak control and preventive use. FUNDING:Coalition for Epidemic Preparedness Innovations (CEPI).

BACKGROUND. An HIV-1 DNA vaccine composed of 7 highly conserved, structurally important elements (conserved elements, CE) of p24(Gag) was tested in a phase I randomized, double-blind clinical trial (HVTN 119, NCT03181789) in people without HIV. DNA vaccination of CE prime/CE+p55(Gag) boost was compared with p55(Gag). METHODS. Two groups (n = 25) received 4 DNA vaccinations (CE/CE+p55(Gag) or p55(Gag)) by intramuscular injection/electroporation, including IL-12 DNA adjuvant. The placebo group (n = 6) received saline. Participants were followed for safety and tolerability. Immunogenicity was assessed for T cell and antibody responses. RESULTS. Both regimens were safe and generally well tolerated. The p24CE vaccine was immunogenic and significantly boosted by CE+p55(Gag) (64% CD4(+), P = 0.037; 42% CD8(+), P = 0.004). CE+p55(Gag) induced responses to 5 of 7 CE, compared with only 2 CE by p55(Gag) DNA, with a higher response to CE5 in 30% of individuals (P = 0.006). CE+p55(Gag) induced significantly higher CD4(+) CE T cell breadth (0.68 vs. 0.22 CE; P = 0.029) and a strong trend for overall T cell breadth (1.14 vs. 0.52 CE; P = 0.051). Both groups developed high cellular and humoral responses. p24CE vaccine-induced CD4(+) CE T cell responses correlated (P = 0.007) with p24(Gag) antibody responses. CONCLUSION. The CE/CE+p55(Gag) DNA vaccine induced T cell responses to conserved regions in p24(Gag), increasing breadth and epitope recognition throughout p55(Gag) compared with p55(Gag) DNA. Vaccines focusing immune responses by priming responses to highly conserved regions could be part of a comprehensive HIV vaccine strategy.

AbstractAntibody affinity maturation is a critical step in development of functional antiviral immunity; however, accurate measurement of affinity maturation of polyclonal serum antibody responses to particulate antigens such as virions is challenging. We describe a novel avidity assay employing biolayer interferometry and dengue virus-like particles. After validation using anti-dengue monoclonal antibodies, the assay was used to assess avidity of antibody responses to a tetravalent dengue vaccine candidate (TAK-003) in children, adolescents, and adults during two phase 2 clinical trials conducted in dengue-endemic regions. Vaccination increased avidity index and avidity remained high through 1 year postvaccination. Neutralizing antibody titers and avidity index did not correlate overall; however, a correlation was observed between neutralizing antibody titer and avidity index in those subjects with the highest degree of antibody affinity maturation. Therefore, vaccination with TAK-003 stimulates polyclonal affinity maturation and functional antibody responses, including neutralizing antibodies.Clinical Trials RegistrationNCT01511250 and NCT02302066.

The emergence of Marburg virus (MARV) in Guinea and Ghana triggered the assembly of the MARV vaccine “MARVAC” consortium representing leaders in the field of vaccine research and development aiming to facilitate a rapid response to this infectious disease threat. Here, we discuss current progress, challenges, and future directions for MARV vaccines.

Background Marburg virus (MARV), an Ebola-like virus, remains an eminent threat to public health as demonstrated by its high associated mortality rate (23-90%) and recent emergence in West Africa for the first time. Although a recombinant vesicular stomatitis virus (rVSV)-based vaccine (Ervebo) is licensed for Ebola virus disease (EVD), no approved countermeasures exist against MARV. Results from clinical trials indicate Ervebo prevents EVD in 97.5-100% of vaccinees 10 days onwards post-immunization. Methodology/Findings Given the rapid immunogenicity of the Ervebo platform against EVD, we tested whether a similar, but highly attenuated, rVSV-based Vesiculovax vector expressing the glycoprotein (GP) of MARV (rVSV-N4CT1-MARV-GP) could provide swift protection against Marburg virus disease (MVD). Here, groups of cynomolgus monkeys were vaccinated 7, 5, or 3 days before exposure to a lethal dose of MARV (Angola variant). All subjects (100%) immunized one week prior to challenge survived; 80% and 20% of subjects survived when vaccinated 5- and 3-days pre-exposure, respectively. Lethality was associated with higher viral load and aberrant innate immunity signaling, whereas survival correlated with development of MARV GP-specific antibodies and early expression of NK cell-, B-cell-, and cytotoxic T-cell-related transcriptional signatures. Conclusions/Significance These results emphasize the utility of Vesiculovax vaccines for MVD outbreak management. The highly attenuated nature of rVSV-N4CT1 vaccines, which are clinically safe in humans, may be preferable to vaccines based on the same platform as Ervebo (rVSV “delta G” platform), which in some trial participants induced vaccine-related adverse events in association with viral replication including arthralgia/arthritis, dermatitis, and cutaneous vasculitis. Author Summary Marburg virus (MARV) is one of the deadliest viruses known to man. One of the most effective vaccines against this pathogen uses a recombinant vesicular stomatitis virus (rVSV) platform to express MARV glycoprotein (GP) immunogen. As rVSV-based vaccines may be used as medical interventions to mitigate or prevent outbreaks of MARV, defining the time window needed to elicit protection is vital. Here, a rVSV vector expressing MARV glycoprotein (rVSV-N4CT1-MARV-GP) fully protected nonhuman primates from lethality and disease when given as soon as 1 week prior to exposure. At 5- and 3-days pre-exposure, partial protection (80% and 20% survival, respectively) was achieved. Vaccination with rVSV-N4CT1-MARV-GP appears to “jump-start” the immune system to allow sufficient time for MARV-specific adaptive responses to form. This fast- acting vaccine is based on a similar platform as Ervebo, the only FDA- and EU-approved vaccine for preventing Ebola virus infection. The rVSV-N4CT1-MARV-GP vaccine features additional attenuations in the rVSV backbone that may contribute to a more acceptable safety profile in vaccinees, as Ervebo in some recipients induced vaccine- related adverse events including rashes and joint pain.

Background: As robust dengue-specific CD4+ and CD8+ T cell responses are essential for protective immunity, we assessed cell-mediated immune (CMI) responses to a DENV-2-based dengue tetravalent vaccine candidate (TAK-003) in adolescents living in Panama, a dengue-endemic country. Methods: Peripheral blood mononuclear cells were collected from a subset of 67 participants > 10 years old included in a phase 2 clinical trial of TAK-003 (Clinicaltrials.gov: NCT02302066). Following stimulation with dengue peptides, the frequency, magnitude, and cross-reactivity of the CD8+ and CD4+ T cell IFN-c, TNF-a and IL-2 responses were assessed by flow cytometry. Results: Intracellular cytokine staining identified NS1, NS3, and NS5 as the most common non-structural (NS) targets of the CD4+ T-cell response (IFN-c+); NS3 and NS5 were the main NS targets of the CD8+ T cell response (IFN-c+). Both CD4+ and CD8+ T-cell responses were multi-functional (IFN-c + TNF-a + IL-2+) and cross-reactive against DENV-1, -3, and -4 serotypes. Similar responses were seen in all CMI assessments irrespective of participant baseline status for dengue neutralizing antibodies and T cells. Conclusions: TAK-003 elicited cross-reactive, multi-functional CD4+ and CD8+ T-cell responses, irrespective of dengue pre-exposure. (c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Auro Vaccines LLC has developed a protein vaccine to prevent disease from Nipah and Hendra virus infection that employs a recombinant soluble Hendra glycoprotein (HeV-sG) adjuvanted with aluminum phosphate. This vaccine is currently under clinical evaluation in a Phase 1 study. The Benefit-Risk Assessment of VAccines by TechnolOgy Working Group (BRAVATO; ex-V3SWG) has prepared a standardized template to describe the key considerations for the benefit-risk assessment of protein vaccines. This will help key stakeholders to assess potential safety issues and understand the benefit-risk of such a vaccine platform. The structured and standardized assessment provided by the template may also help contribute to improved public acceptance and communication of licensed protein vaccines.

Background Dengue virus (DENV) can cause life-threatening disease characterized by endothelial dysfunction and vascular leakage. DENV nonstructural protein 1 (NS1) induces human endothelial hyperpermeability and vascular leak in mice, and NS1 vaccination confers antibody-mediated protective immunity. We evaluated the magnitude, cross-reactivity, and functionality of NS1-specific IgG antibody responses in sera from a phase 2 clinical trial of Takeda’s live-attenuated tetravalent dengue vaccine candidate (TAK-003). Methods We developed an enzyme-linked immunosorbent assay to measure anti-DENV NS1 IgG in sera from DENV-naive or preimmune subjects pre- and postvaccination with TAK-003 and evaluated the functionality of this response using in vitro models of endothelial permeability. Results TAK-003 significantly increased DENV-2 NS1-specific IgG in naive individuals, which cross-reacted with DENV-1, -3, and -4 NS1 to varying extents. NS1-induced endothelial hyperpermeability was unaffected by prevaccination serum from naive subjects but was variably inhibited by serum from preimmune subjects. After TAK-003 vaccination, all samples from naive and preimmune vaccinees completely abrogated DENV-2 NS1-induced hyperpermeability and cross-inhibited hyperpermeability induced by DENV-1, -3, and -4 NS1. Inhibition of NS1-induced hyperpermeability correlated with NS1-specific IgG concentrations. Postvaccination sera also prevented NS1-induced degradation of endothelial glycocalyx components. Conclusion We provide evidence for functional NS1-specific IgG responses elicited by a candidate dengue vaccine. Clinical Trials Registration NCT01511250.

Background The safety and immunogenicity of a highly attenuated recombinant vesicular stomatitis virus (rVSV) expressing HIV-1 gag (rVSVN4CT1-HIV-lgag1) was shown in previous phase 1 clinical studies. An rVSV vector expressing Ebola virus glycoprotein (EBOV-GP) in place of HIV-1 gag (rVSVN4CT1-EBOVGP1) showed single-dose protection from lethal challenge with low passage Ebola virus in non-human primates. We aimed to evaluate the safety and immunogenicity of the rVSVN4CT1-EBOVGP1 vaccine in healthy adults. Methods We did a randomised double-blind, placebo-controlled, phase 1 dose-escalation study at a single clinical site (Optimal Research) in Melbourne, FL, USA. Eligible participants were healthy men and non-pregnant women aged 18-60 years, with a body-mass index (BMI) of less than 40 kg/m(2), no history of filovirus infection, VSV infection, or receipt of rVSV in previous studies, and who had not visited regions where Ebola virus outbreaks have occurred. Three cohorts were enrolled to assess a low (2.5x10(4) plaque forming units [PFU]), intermediate (2 x 10(5) PFU), or high dose (1.8x10(6) PFU) of the vaccine. Participants within each cohort were randomly allocated (10:3) to receive vaccine or placebo by intramuscular injection in a homologous prime and boost regimen, with 4 weeks between doses. All syringes were masked with syringe sleeves; participants and study site staff were not blinded to dose level but were blinded to active vaccine and placebo. The primary outcomes were safety and tolerability; immunogenicity, assessed as GP-specific humoral immune response (at 2 weeks after each dose) and cellular immune response (at 1 and 2 weeks after each dose), was a secondary outcome. All randomised participants were included in primary and safety analyses. This trial is registered with ClinicalTrials.gov, NCT02718469. Findings Between Dec 22,2015, and Sept 15,2016,39 individuals (18 [46%] men and 21 [54%] women, mean age 51 years [SD 10]) were enrolled, with ten participants receiving the vaccine and three participants receiving placebo in each of three cohorts. One participant in the intermediate dose cohort was withdrawn from the study because of a diagnosis of invasive ductal breast carcinoma 24 days after the first vaccination, which was considered unrelated to the vaccine. No severe adverse events were observed. Solicited local adverse events occurred in ten (26%) of 39 participants after the first dose and nine (24%) of 38 participants after the second dose; the events lasted 3 days or less, were predominantly injection site tenderness (17 events) and injection site pain (ten events), and were either mild (19 events) or moderate (ten events) in intensity. Systemic adverse events occurred in 13 (33%) of 39 participants after the first dose and eight (21%) of 38 participants after the second dose; the events were mild (45 events) or moderate (11 events) in severity, and the most common events were malaise or fatigue (13 events) and headache (12 events). Arthritis and maculopapular, vesicular, or purpuric rash distal to the vaccination site(s) were not reported. A GP-specific IgG response was detected in all vaccine recipients after two doses (and IgG response frequency was 100% after a single high dose), and an Ebola virus neutralising response was detected in 100% of participants in the high-dose cohort. Interpretation The rVSVN4CT1-EBOVGP1 vaccine was well tolerated at all dose levels tested and was immunogenic despite a high degree of attenuation. The combined safety and immunogenicity profile of the rVSVN4CT1-EBOVGP1 vaccine vector support phase 1-2 clinical evaluation. Copyright (C) 2020 Elsevier Ltd. All rights reserved.

BACKGROUND:The addition of plasmid cytokine adjuvants, electroporation, and live attenuated viral vectors may further optimize immune responses to DNA vaccines in heterologous prime-boost combinations. The objective of this study was to test the safety and tolerability of a novel prime-boost vaccine regimen incorporating these strategies with different doses of IL-12 plasmid DNA adjuvant. METHODS:In a phase 1 study, 88 participants received an HIV-1 multiantigen (gag/pol, env, nef/tat/vif) DNA vaccine (HIV-MAG, 3000 μg) co-administered with IL-12 plasmid DNA adjuvant at 0, 250, 1000, or 1500 μg (N = 22/group) given intramuscularly with electroporation (Ichor TriGrid™ Delivery System device) at 0, 1 and 3 months; followed by attenuated recombinant vesicular stomatitis virus, serotype Indiana, expressing HIV-1 Gag (VSV-Gag), 3.4 ⊆ 107 plaque-forming units (PFU), at 6 months; 12 others received placebo. Injections were in both deltoids at each timepoint. Participants were monitored for safety and tolerability for 15 months. RESULTS:The dose of IL-12 pDNA did not increase pain scores, reactogenicity, or adverse events with the co-administered DNA vaccine, or following the VSV-Gag boost. Injection site pain and reactogenicity were common with intramuscular injections with electroporation, but acceptable to most participants. VSV-Gag vaccine often caused systemic reactogenicity symptoms, including a viral syndrome (in 41%) of fever, chills, malaise/fatigue, myalgia, and headache; and decreased lymphocyte counts 1 day after vaccination. CONCLUSIONS:HIV-MAG DNA vaccine given by intramuscular injection with electroporation was safe at all doses of IL-12 pDNA. The VSV-Gag vaccine at this dose was associated with fever and viral symptoms in some participants, but the vaccine regimens were safe and generally well-tolerated. TRIAL REGISTRATION:Clinical Trials.gov NCT01578889.

ABSTRACT Previous studies demonstrated that a single intramuscular (i.m.) dose of an attenuated recombinant vesicular stomatitis virus (rVSV) vector (VesiculoVax vector platform; rVSV-N4CT1) expressing the glycoprotein (GP) from the Mayinga strain of Zaire ebolavirus (EBOV) protected nonhuman primates (NHPs) from lethal challenge with EBOV strains Kikwit and Makona. Here, we studied the immunogenicities of an expanded range of attenuated rVSV vectors expressing filovirus GP in mice. Based on data from those studies, an optimal attenuated trivalent rVSV vector formulation was identified that included rVSV vectors expressing EBOV, Sudan ebolavirus (SUDV), and the Angola strain of Marburg marburgvirus (MARV) GPs. NHPs were vaccinated with a single dose of the trivalent formulation, followed by lethal challenge 28 days later with each of the three corresponding filoviruses. At day 14 postvaccination, a serum IgG response specific for all three GPs was detected in all the vaccinated macaques. A modest and balanced cell-mediated immune response specific for each GP was also detected in a majority of the vaccinated macaques. No matter the level of total GP-specific immune response detected postvaccination, all the vaccinated macaques were protected from disease and death following lethal challenge with each of the three filoviruses. These findings indicate that vaccination with a single dose of attenuated rVSV-N4CT1 vectors each expressing a single filovirus GP may provide protection against the filoviruses most commonly responsible for outbreaks of hemorrhagic fever in sub-Saharan Africa. IMPORTANCE The West African Ebola virus Zaire outbreak in 2013 showed that the disease was not only a regional concern, but a worldwide problem, and highlighted the need for a safe and efficacious vaccine to be administered to the populace. However, other endemic pathogens, like Ebola virus Sudan and Marburg, also pose an important health risk to the public and therefore require development of a vaccine prior to the occurrence of an outbreak. The significance of our research was the development of a blended trivalent filovirus vaccine that elicited a balanced immune response when administered as a single dose and provided complete protection against a lethal challenge with all three filovirus pathogens.

ABSTRACT The HIV Vaccine Trials Network (HVTN) 087 vaccine trial assessed the effect of increasing doses of pIL-12 (interleukin-12 delivered as plasmid DNA) adjuvant on the immunogenicity of an HIV-1 multiantigen (MAG) DNA vaccine delivered by electroporation and boosted with a vaccine comprising an attenuated vesicular stomatitis virus expressing HIV-1 Gag (VSV-Gag). We randomized 100 healthy adults to receive placebo or 3 mg HIV-MAG DNA vaccine (ProfectusVax HIV-1 gag / pol or ProfectusVax nef / tat / vif , env ) coadministered with pIL-12 at 0, 250, 1,000, or 1,500 μg intramuscularly by electroporation at 0, 1, and 3 months followed by intramuscular inoculation with 3.4 × 10 7 PFU VSV-Gag vaccine at 6 months. Immune responses were assessed after the prime and boost and 6 months after the last vaccination. High-dose pIL-12 increased the magnitude of CD8 + T-cell responses postboost compared to no pIL-12 ( P = 0.02), while CD4 + T-cell responses after the prime were higher in the absence of pIL-12 than with low- and medium-dose pIL-12 ( P ≤ 0.05). The VSV boost increased Gag-specific CD4 + and CD8 + T-cell responses in all groups ( P < 0.001 for CD4 + T cells), inducing a median of four Gag epitopes in responders. Six to 9 months after the boost, responses decreased in magnitude, but CD8 + T-cell response rates were maintained. The addition of a DNA prime dramatically improved responses to the VSV vaccine tested previously in the HVTN 090 trial, leading to broad epitope targeting and maintained CD8 + T-cell response rates at early memory. The addition of high-dose pIL-12 given with a DNA prime by electroporation and boosted with VSV-Gag increased the CD8 + T-cell responses but decreased the CD4 + responses. This approach may be advantageous in reshaping the T-cell responses to a variety of chronic infections or tumors. (This study has been registered at ClinicalTrials.gov under registration no. NCT01578889.)

Despite substantial clinical benefits, complete eradication of HIV has not been possible using antiretroviral therapy (ART) alone. Strategies that can either eliminate persistent viral reservoirs or boost host immunity to prevent rebound of virus from these reservoirs after discontinuation of ART are needed; one possibility is therapeutic vaccination. We report the results of a randomized, placebo-controlled trial of a therapeutic vaccine regimen in patients in whom ART was initiated during the early stage of HIV infection and whose immune system was anticipated to be relatively intact. The objectives of our study were to determine whether the vaccine was safe and could induce an immune response that would maintain suppression of plasma viremia after discontinuation of ART. Vaccinations were well tolerated with no serious adverse events but produced only modest augmentation of existing HIV-specific CD4+ T cell responses, with little augmentation of CD8+ T cell responses. Compared with placebo, the vaccination regimen had no significant effect on the kinetics or magnitude of viral rebound after interruption of ART and no impact on the size of the HIV reservoir in the CD4+ T cell compartment. Notably, 26% of subjects in the placebo arm exhibited sustained suppression of viremia (<400 copies/ml) after treatment interruption, a rate of spontaneous suppression higher than previously reported. Our findings regarding the degree and kinetics of plasma viral rebound after ART interruption have potentially important implications for the design of future trials testing interventions aimed at achieving ART-free control of HIV infection.

An effective vaccine for HIV still remains elusive. Our previous studies showed that a protein-based FLSC (a genetic fusion of gp120 and CD4) protected macaques against repeat rectal challenges with SHIV162P3 but efficacy was low. We hypothesized that DNA would provide a superior prime to a subunit boost than subunit alone and that the adjuvants IL-12 and/or LTA1 would improve priming. FLSC delivery regimens were evaluated in a challenge model using SIVsmE543 antigens and a cross clade challenge with SIVmac251. Eight macaques/group were immunized with DNA expressing a gag/pol fusion and FLSC with/without LTA1, IL-12 or LTA1+IL-12 by electroporation on weeks 0, 4 and 8. Booster immunizations of 300 μg of FLSCsmCG7V/alum were given at week 42. Two weeks later, animals were weekly challenged rectally 10 times with SIVmac251. Immune measures were compared using T tests (parametric) or Mann-Whitney Rank Sum Tests (non-parametric). Infection rates were compared using Log Rank tests. The DNA/IL-12 prime regimen provided 75% efficacy compared to the same regimen without IL-12. Efficacy did not correlate with antibody binding or neutralizing titers to Tier 1 SIVmac251 whereas ADCC titers and antibody binding ratios of FcgR3/FcgR1 correlated with protection, provided T cell responses were low. The DNA/LTA1/IL-12 regimen generated substantially superior CMI responses, but showed no protection. These results suggest that vaccines generating ADCC capable antibodies with high FcgR3/FcgR1 ratios that evoke minimal T cell responses may be the most protective.

Background:Therapeutic vaccination is being studied in eradication and “functional cure” strategies for HIV-1. The Profectus Biosciences multiantigen (MAG) HIV-1 DNA vaccine encodes HIV-1 Gag/Pol, Nef/Tat/Vif, and Envelope, and interleukin-12 (IL-12) and is delivered by electroporation combined with intramuscular injection (IM-EP). Methods:Sixty-two HIV-1–infected patients on antiretroviral therapy (plasma HIV-1 RNA levels ⩽200 copies/mL; CD4+ T-cell counts ≥500 cells/mm3) were randomly allocated 5:1 to receive vaccine or placebo. At weeks 0, 4, and 12, 4 consecutive cohorts received 3000 &mgr;g HIV MAG pDNA with 0, 50, 250, or 1000 &mgr;g of IL-12 pDNA by IM-EP. A fifth cohort received HIV MAG pDNA and 1000 &mgr;g of IL-12 pDNA by standard IM injection. Results:CD4+ T cells expressing IL-2 in response to Gag and Pol and interferon-&ggr; responses to Gag, Pol, and Env increased from baseline to week 14 in the low-dose (50-&mgr;g) IL-12 arm vs. placebo (P < 0.05; intracellular cytokine staining). The total increase in the IL-2–expressing CD4+ T-cell responses to any antigen was also higher in the low-dose IL-12 arm vs. placebo (P = 0.04). Cytokine responses by CD8 T cells to HIV antigens were not increased in any vaccine arm relative to placebo. Conclusions:HIV-1 MAG/low-dose IL-12 DNA vaccine delivered by IM-EP augmented CD4+ but not CD8+ T-cell responses to multiple HIV-1 antigens.

A guiding principle for HIV vaccine design has been that cellular and humoral immunity work together to provide the strongest degree of efficacy. However, three efficacy trials of Ad5-vectored HIV vaccines showed no protection. Transmission was increased in two of the trials, suggesting that this vaccine strategy elicited CD4+ T-cell responses that provide more targets for infection, attenuating protection or increasing transmission. The degree to which this problem extends to other HIV vaccine candidates is not known. Here, we show that a gp120-CD4 chimeric subunit protein vaccine (full-length single chain) elicits heterologous protection against simian-human immunodeficiency virus (SHIV) or simian immunodeficiency virus (SIV) acquisition in three independent rhesus macaque repeated low-dose rectal challenge studies with SHIV162P3 or SIVmac251. Protection against acquisition was observed with multiple formulations and challenges. In each study, protection correlated with antibody-dependent cellular cytotoxicity specific for CD4-induced epitopes, provided that the concurrent antivaccine T-cell responses were minimal. Protection was lost in instances when T-cell responses were high or when the requisite antibody titers had declined. Our studies suggest that balance between a protective antibody response and antigen-specific T-cell activation is the critical element to vaccine-mediated protection against HIV. Achieving and sustaining such a balance, while enhancing antibody durability, is the major challenge for HIV vaccine development, regardless of the immunogen or vaccine formulation.

Background Strategies to enhance the immunogenicity of DNA vaccines in humans include i) co-administration of molecular adjuvants, ii) intramuscular administration followed by in vivo electroporation (IM/EP) and/or iii) boosting with a different vaccine. Combining these strategies provided protection of macaques challenged with SIV; this clinical trial was designed to mimic the vaccine regimen in the SIV study. Methods Seventy five healthy, HIV-seronegative adults were enrolled into a phase 1, randomized, double-blind, placebo-controlled trial. Multi-antigenic HIV (HIVMAG) plasmid DNA (pDNA) vaccine alone or co-administered with pDNA encoding human Interleukin 12 (IL-12) (GENEVAX IL-12) given by IM/EP using the TriGrid Delivery System was tested in different prime-boost regimens with recombinant Ad35 HIV vaccine given IM. Results All local reactions but one were mild or moderate. Systemic reactions and unsolicited adverse events including laboratory abnormalities did not differ between vaccine and placebo recipients. No serious adverse events (SAEs) were reported. T cell and antibody response rates after HIVMAG (x3) prime—Ad35 (x1) boost were independent of IL-12, while the magnitude of interferon gamma (IFN-γ) ELISPOT responses was highest after HIVMAG (x3) without IL-12. The quality and phenotype of T cell responses shown by intracellular cytokine staining (ICS) were similar between groups. Inhibition of HIV replication by autologous T cells was demonstrated after HIVMAG (x3) prime and was boosted after Ad35. HIV specific antibodies were detected only after Ad35 boost, although there was a priming effect with 3 doses of HIVMAG with or without IL-12. No anti-IL-12 antibodies were detected. Conclusion The vaccines were safe, well tolerated and moderately immunogenic. Repeated administration IM/EP was well accepted. An adjuvant effect of co-administered plasmid IL-12 was not detected. Trial Registration ClinicalTrials.gov NCT01496989

Two second-generation attenuated Ebola virus vaccines based on recombinant vesicular stomatitis virus protect macaques against infection with a recent Ebola virus isolate from Guinea. The N1 and N4 rVSV vectors described in this manuscript are the subject of patents licensed to Profectus BioSciences, Inc. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the University of Texas Medical Branch. Two variants of the recently developed VesiculoVax recombinant vesicular stomatitis virus (VSV)-based Ebola vaccine have been tested for their ability to protect cynomolgus monkeys against heterologous challenge with the new outbreak strain of Ebola virus. Animals received a single injection of either N4CT1 or N1CT1 VesiculoVax and were exposed to a high dose of Ebola four weeks later. None of the vaccinated animals developed illness and all survived. This works raises the prospect that second-generation vaccines may have fewer safety concerns than the first-generation vaccines currently in use in the field. The family Filoviridae contains three genera, Ebolavirus (EBOV), Marburg virus, and Cuevavirus1. Some members of the EBOV genus, including Zaire ebolavirus (ZEBOV), can cause lethal haemorrhagic fever in humans. During 2014 an unprecedented ZEBOV outbreak occurred in West Africa and is still ongoing, resulting in over 10,000 deaths, and causing global concern of uncontrolled disease. To meet this challenge a rapid-acting vaccine is needed. Many vaccine approaches have shown promise in being able to protect nonhuman primates against ZEBOV2. In response to the current ZEBOV outbreak several of these vaccines have been fast tracked for human use. However, it is not known whether any of these vaccines can provide protection against the new outbreak Makona strain of ZEBOV. One of these approaches is a first-generation recombinant vesicular stomatitis virus (rVSV)-based vaccine expressing the ZEBOV glycoprotein (GP) (rVSV/ZEBOV). To address safety concerns associated with this vector, we developed two candidate, further-attenuated rVSV/ZEBOV vaccines. Both attenuated vaccines produced an approximately tenfold lower vaccine-associated viraemia compared to the first-generation vaccine and both provided complete, single-dose protection of macaques from lethal challenge with the Makona outbreak strain of ZEBOV.

DNA encoded adjuvants are well known for increasing the magnitude of cellular and/or humoral immune responses directed against vaccine antigens. DNA adjuvants can also tune immune responses directed against vaccine antigens to better protect against infection of the target organism. Two potent DNA adjuvants that have unique abilities to tune immune responses are the catalytic A1 domains of Cholera Toxin (CTA1) and Heat-Labile Enterotoxin (LTA1). Here, we have characterized the adjuvant activities of CTA1 and LTA1 using HIV and SIV genes as model antigens. Both of these adjuvants enhanced the magnitude of antigen-specific cellular immune responses on par with those induced by the well-characterized cytokine adjuvants IL-12 and GM-CSF. CTA1 and LTA1 preferentially enhanced cellular responses to the intracellular antigen SIVmac239-gag over those for the secreted HIVBaL-gp120 antigen. IL-12, GM-CSF and electroporation did the opposite suggesting differences in the mechanisms of actions of these diverse adjuvants. Combinations of CTA1 or LTA1 with IL-12 or GM-CSF generated additive and better balanced cellular responses to both of these antigens. Consistent with observations made with the holotoxin and the CTA1-DD adjuvant, CTA1 and LTA1 evoked mixed Th1/Th17 cellular immune responses. Together, these results show that CTA1 and LTA1 are potent DNA vaccine adjuvants that favor the intracellular antigen gag over the secreted antigen gp120 and evoke mixed Th1/Th17 responses against both of these antigens. The results also indicate that achieving a balanced immune response to multiple intracellular and extracellular antigens delivered via DNA vaccination may require combining adjuvants that have different and complementary mechanisms of action.

Previously, recombinant vesicular stomatitis virus (rVSV) pseudotypes expressing Ebolavirus glycoproteins (GPs) in place of the VSV G protein demonstrated protection of nonhuman primates from lethal homologous Ebolavirus challenge. Those pseudotype vectors contained no additional attenuating mutations in the rVSV genome. Here we describe rVSV vectors containing a full complement of VSV genes and expressing the Ebola virus (EBOV) GP from an additional transcription unit. These rVSV vectors contain the same combination of attenuating mutations used previously in the clinical development pathway of an rVSV/human immunodeficiency virus type 1 vaccine. One of these rVSV vectors (N4CT1-EBOVGP1), which expresses membrane-anchored EBOV GP from the first position in the genome (GP1), elicited a balanced cellular and humoral GP-specific immune response in mice. Guinea pigs immunized with a single dose of this vector were protected from any signs of disease following lethal EBOV challenge, while control animals died in 7-9 days. Subsequently, N4CT1-EBOVGP1 demonstrated complete, single-dose protection of 2 macaques following lethal EBOV challenge. A single sham-vaccinated macaque died from disease due to EBOV infection. These results demonstrate that highly attenuated rVSV vectors expressing EBOV GP may provide safer alternatives to current EBOV vaccines.