Phase 1 safety and immunogenicity testing of DNA and recombinant modified vaccinia Ankara vaccines expressing HIV-1 virus-like particles

Assessment of CD8+ T-cell mediated immunity in an influenza A(H3N2) human challenge model in Belgium: a single centre, randomised, double-blind phase 2 study

BACKGROUND

Protection afforded by inactivated influenza vaccines can theoretically be improved by inducing T-cell responses to conserved internal influenza A antigens. We assessed whether, in an influenza controlled human infection challenge, susceptible individuals receiving a vaccine boosting T-cell responses would exhibit lower viral load and decreased symptoms compared with placebo recipients.

METHODS

In this single centre, randomised, double-blind phase 2 study, healthy adult (aged 18-55 years) volunteers with microneutralisation titres of less than 20 to the influenza A(H3N2) challenge strain were enrolled at an SGS quarantine facility in Antwerp, Belgium. Participants were randomly assigned double-blind using a permuted-block list with a 3:2 allocation ratio to receive 0·5 mL intramuscular injections of modified vaccinia Ankara (MVA) expressing H3N2 nucleoprotein (NP) and matrix protein 1 (M1) at 1·5 × 108 plaque forming units (4·3 × 108 50% tissue culture infectious dose [TCID50]; MVA-NP+M1 group) or saline placebo (placebo group). At least 6 weeks later, participants were challenged intranasally with 0·5 mL of a 1 × 106 TCID50/mL dose of influenza A/Belgium/4217/2015 (H3N2). Nasal swabs were collected twice daily from day 2 until day 11 for viral PCR, and symptoms of influenza were recorded from day 2 until day 11. The primary outcome was to determine the efficacy of MVA-NP+M1 vaccine to reduce the degree of nasopharyngeal viral shedding as measured by the cumulative viral area under the curve using a log-transformed quantitative PCR. This study is registered with ClinicalTrials.gov, NCT03883113.

FINDINGS

Between May 2 and Oct 24, 2019, 145 volunteers were enrolled and randomly assigned to the MVA-NP+M1 group (n=87) or the placebo group (n=58). Of these, 118 volunteers entered the challenge period (71 in the MVA-NP+M1 group and 47 in the placebo group) and 117 participants completed the study (71 in the MVA-NP+M1 group and 46 in the placebo group). 78 (54%) of the 145 volunteers were female and 67 (46%) were male. The primary outcome, overall viral load as determined by quantitative PCR, did not show a statistically significant difference between the MVA-NP+M1 (mean 649·7 [95% CI 552·7-746·7) and placebo groups (mean 726·1 [604·0-848·2]; p=0·17). All reported treatment emergent adverse events (TEAEs; 11 in the vaccination phase and 51 in the challenge phase) were grade 1 and 2, except for two grade 3 TEAEs in the placebo group in the challenge phase. A grade 4 second trimester fetal death, considered possibly related to the MVA-NP+M1 vaccination, and an acute psychosis reported in a placebo participant during the challenge phase were reported.

INTERPRETATION

The use of an MVA vaccine to expand CD4+ or CD8+ T cells to conserved influenza A antigens in peripheral blood did not affect nasopharyngeal viral load in an influenza H3N2 challenge model in seronegative, healthy adults.

FUNDING

Department of Health and Human Services; Administration for Strategic Preparedness and Response; Biomedical Advanced Research and Development Authority; and Barinthus Biotherapeutics.

Harnessing T-Cells for Enhanced Vaccine Development against Viral Infections

Despite significant strides in vaccine research and the availability of vaccines for many infectious diseases, the threat posed by both known and emerging infectious diseases persists. Moreover, breakthrough infections following vaccination remain a concern. Therefore, the development of novel vaccines is imperative. These vaccines must exhibit robust protective efficacy, broad-spectrum coverage, and long-lasting immunity. One promising avenue in vaccine development lies in leveraging T-cells, which play a crucial role in adaptive immunity and regulate immune responses during viral infections. T-cell recognition can target highly variable or conserved viral proteins, and memory T-cells offer the potential for durable immunity. Consequently, T-cell-based vaccines hold promise for advancing vaccine development efforts. This review delves into the latest research advancements in T-cell-based vaccines across various platforms and discusses the associated challenges.

Personalized Cancer Vaccines Go Viral: Viral Vectors in the Era of Personalized Immunotherapy of Cancer

The aim of personalized cancer vaccines is to elicit potent and tumor-specific immune responses against neoantigens specific to each patient and to establish durable immunity, while minimizing the adverse events. Over recent years, there has been a renewed interest in personalized cancer vaccines, primarily due to the advancement of innovative technologies for the identification of neoantigens and novel vaccine delivery platforms. Here, we review the emerging field of personalized cancer vaccination, with a focus on the use of viral vectors as a vaccine platform. The recent advancements in viral vector technology have led to the development of efficient production processes, positioning personalized viral vaccines as one of the preferred technologies. Many clinical trials have shown the feasibility, safety, immunogenicity and, more recently, preliminary evidence of the anti-tumor activity of personalized vaccination, fostering active research in the field, including further clinical trials for different tumor types and in different clinical settings.

Intradermal but not intramuscular modified vaccinia Ankara immunizations protect against intravaginal tier2 simian-human immunodeficiency virus challenges in female macaques

Route of immunization can markedly influence the quality of immune response. Here, we show that intradermal (ID) but not intramuscular (IM) modified vaccinia Ankara (MVA) vaccinations provide protection from acquisition of intravaginal tier2 simian-human immunodeficiency virus (SHIV) challenges in female macaques. Both routes of vaccination induce comparable levels of serum IgG with neutralizing and non-neutralizing activities. The protection in MVA-ID group correlates positively with serum neutralizing and antibody-dependent phagocytic activities, and envelope-specific vaginal IgA; while the limited protection in MVA-IM group correlates only with serum neutralizing activity. MVA-ID immunizations induce greater germinal center Tfh and B cell responses, reduced the ratio of Th1 to Tfh cells in blood and showed lower activation of intermediate monocytes and inflammasome compared to MVA-IM immunizations. This lower innate activation correlates negatively with induction of Tfh responses. These data demonstrate that the MVA-ID vaccinations protect against intravaginal SHIV challenges by modulating the innate and T helper responses.

Viral vectored vaccines: design, development, preventive and therapeutic applications in human diseases

Human diseases, particularly infectious diseases and cancers, pose unprecedented challenges to public health security and the global economy. The development and distribution of novel prophylactic and therapeutic vaccines are the prioritized countermeasures of human disease. Among all vaccine platforms, viral vector vaccines offer distinguished advantages and represent prominent choices for pathogens that have hampered control efforts based on conventional vaccine approaches. Currently, viral vector vaccines remain one of the best strategies for induction of robust humoral and cellular immunity against human diseases. Numerous viruses of different families and origins, including vesicular stomatitis virus, rabies virus, parainfluenza virus, measles virus, Newcastle disease virus, influenza virus, adenovirus and poxvirus, are deemed to be prominent viral vectors that differ in structural characteristics, design strategy, antigen presentation capability, immunogenicity and protective efficacy. This review summarized the overall profile of the design strategies, progress in advance and steps taken to address barriers to the deployment of these viral vector vaccines, simultaneously highlighting their potential for mucosal delivery, therapeutic application in cancer as well as other key aspects concerning the rational application of these viral vector vaccines. Appropriate and accurate technological advances in viral vector vaccines would consolidate their position as a leading approach to accelerate breakthroughs in novel vaccines and facilitate a rapid response to public health emergencies.

Vector Aided Microenvironment programming (VAMP): reprogramming the TME with MVA virus expressing IL-12 for effective antitumor activity

BACKGROUND

Tumor microenvironment (TME) represents a critical hurdle in cancer immunotherapy, given its ability to suppress antitumor immunity. Several efforts are made to overcome this hostile TME with the development of new therapeutic strategies modifying TME to boost antitumor immunity. Among these, cytokine-based approaches have been pursued for their known immunomodulatory effects on different cell populations within the TME. IL-12 is a potent pro-inflammatory cytokine that demonstrates striking immune activation and tumor control but causes severe adverse effects when systemically administered. Thus, local administration is considered a potential strategy to achieve high cytokine concentrations at the tumor site while sparing systemic adverse effects.

METHODS

Modified Vaccinia Ankara (MVA) vector is a potent inducer of pro-inflammatory response. Here, we cloned IL-12 into the genome of MVA for intratumoral immunotherapy, combining the immunomodulatory properties of both the vector and the cargo. The antitumor activity of MVA-IL-12 and its effect on TME reprogramming were investigated in preclinical tumor models. RNA sequencing (RNA-Seq) analysis was performed to assess changes in the TME in treated and distal tumors and the effect on the intratumoral T-cell receptor repertoire.

RESULTS

Intratumoral injection of MVA-IL-12 resulted in strong antitumor activity with the complete remission of established tumors in multiple murine models, including those resistant to checkpoint inhibitors. The therapeutic activity of MVA-IL-12 was associated with very low levels of circulating cytokine. Effective TME reprogramming was demonstrated on treatment, with the reduction of immunosuppressive M2 macrophages while increasing pro-inflammatory M1, and recruitment of dendritic cells. TME switch from immunosuppressive into immunostimulatory environment allowed for CD8 T cells priming and expansion leading to tumor attack.

CONCLUSIONS

Intratumoral administration of MVA-IL-12 turns immunologically 'cold' tumors 'hot' and overcomes resistance to programmed cell death protein-1 blockade.

Intravenous administration of viral vectors expressing prostate cancer antigens enhances the magnitude and functionality of CD8+ T cell responses

BACKGROUND

The use of immunotherapeutic vaccination in prostate cancer is a promising approach that likely requires the induction of functional, cytotoxic T cells . The experimental approach described here uses a well-studied adenovirus-poxvirus heterologous prime-boost regimen, in which the vectors encode a combination of prostate cancer antigens, with the booster dose delivered by either the intravenous or intramuscular (IM) route. This prime-boost regimen was investigated for antigen-specific CD8+ T cell induction.

METHODS

The coding sequences for four antigens expressed in prostate cancer, 5T4, PSA, PAP, and STEAP1, were inserted into replication-incompetent chimpanzee adenovirus Oxford 1 (ChAdOx1) and into replication-deficient modified vaccinia Ankara (MVA). In four strains of mice, ChAdOx1 prime was delivered intramuscularly, with an MVA boost delivered by either IM or intravenous routes. Immune responses were measured in splenocytes using ELISpot, multiparameter flow cytometry, and a targeted in vivo killing assay.

RESULTS

The prime-boost regimen was highly immunogenic, with intravenous administration of the boost resulting in a sixfold increase in the magnitude of antigen-specific T cells induced and increased in vivo killing relative to the intramuscular boosting route. Prostate-specific antigen (PSA)-specific responses were dominant in all mouse strains studied (C57BL/6, BALBc, CD-1 and HLA-A2 transgenic).

CONCLUSION

This quadrivalent immunotherapeutic approach using four antigens expressed in prostate cancer induced high magnitude, functional CD8+ T cells in murine models. The data suggest that comparing the intravenous versus intramuscular boosting routes is worthy of investigation in humans.

Development of Modified Vaccinia Virus Ankara-Based Vaccines: Advantages and Applications

Modified vaccinia virus Ankara (MVA) is a promising viral vector for vaccine development. MVA is well studied and has been widely used for vaccination against smallpox in Germany. This review describes the history of the origin of the virus and its properties as a vaccine, including a high safety profile. In recent years, MVA has found its place as a vector for the creation of vaccines against various diseases. To date, a large number of vaccine candidates based on the MVA vector have already been developed, many of which have been tested in preclinical and clinical studies. We discuss data on the immunogenicity and efficacy of some of these vaccines.

A clade C HIV-1 vaccine protects against heterologous SHIV infection by modulating IgG glycosylation and T helper response in macaques

The rising global HIV-1 burden urgently requires vaccines capable of providing heterologous protection. Here, we developed a clade C HIV-1 vaccine consisting of priming with modified vaccinia Ankara (MVA) and boosting with cyclically permuted trimeric gp120 (CycP-gp120) protein, delivered either orally using a needle-free injector or through parenteral injection. We tested protective efficacy of the vaccine against intrarectal challenges with a pathogenic heterologous clade C SHIV infection in rhesus macaques. Both routes of vaccination induced a strong envelope-specific IgG in serum and rectal secretions directed against V1V2 scaffolds from a global panel of viruses with polyfunctional activities. Envelope-specific IgG showed lower fucosylation compared with total IgG at baseline, and most of the vaccine-induced proliferating blood CD4⁺ T cells did not express CCR5 and α4β7, markers associated with HIV target cells. After SHIV challenge, both routes of vaccination conferred significant and equivalent protection, with 40% of animals remaining uninfected at the end of six weekly repeated challenges with an estimated efficacy of 68% per exposure. Induction of envelope-specific IgG correlated positively with G1FB glycosylation, and G2S2F glycosylation correlated negatively with protection. Vaccine-induced TNF-α⁺ IFN-γ⁺ CD8⁺ T cells and TNF-α⁺ CD4⁺ T cells expressing low levels of CCR5 in the rectum at prechallenge were associated with decreased risk of SHIV acquisition. These results demonstrate that the clade C MVA/CycP-gp120 vaccine provides heterologous protection against a tier2 SHIV rectal challenge by inducing a polyfunctional antibody response with distinct Fc glycosylation profile, as well as cytotoxic CD8 T cell response and CCR5-negative T helper response in the rectum.

Single-dose replicating poxvirus vector-based RBD vaccine drives robust humoral and T cell immune response against SARS-CoV-2 infection

The coronavirus disease 2019 (COVID-19) pandemic requires the continued development of safe, long-lasting, and efficacious vaccines for preventive responses to major outbreaks around the world, and especially in isolated and developing countries. To combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we characterize a temperature-stable vaccine candidate (TOH-Vac1) that uses a replication-competent, attenuated vaccinia virus as a vector to express a membrane-tethered spike receptor binding domain (RBD) antigen. We evaluate the effects of dose escalation and administration routes on vaccine safety, efficacy, and immunogenicity in animal models. Our vaccine induces high levels of SARS-CoV-2 neutralizing antibodies and favorable T cell responses, while maintaining an optimal safety profile in mice and cynomolgus macaques. We demonstrate robust immune responses and protective immunity against SARS-CoV-2 variants after only a single dose. Together, these findings support further development of our novel and versatile vaccine platform as an alternative or complementary approach to current vaccines.

DNA and modified vaccinia Ankara prime-boost vaccination generates strong CD8+ T cell responses against minor histocompatibility antigen HA-1

Allogeneic immune responses underlie the graft-versus-leukaemia effect of stem cell transplantation, but disease relapse occurs in many patients. Minor histocompatibility antigen (mHAg) peptides mediate alloreactive T cell responses and induce graft-versus-leukaemia responses when expressed on patient haematopoietic tissue. We vaccinated nine HA-1-negative donors against HA-1 with a 'prime-boost' protocol of either two or three DNA 'priming' vaccinations prior to 'boost' with modified vaccinia Ankara (MVA). HA-1-specific CD8+ T cell responses were observed in seven donors with magnitude up to 1·5% of total CD8+ T cell repertoire. HA-1-specific responses peaked two weeks post-MVA challenge and were measurable in most donors after 12 months. HA-1-specific T cells demonstrated strong cytotoxic activity and lysed target cells with endogenous HA-1 protein expression. The pattern of T cell receptor (TCR) usage by HA-1-specific T cells revealed strong conservation of T cell receptor beta variable 7-9 (TRBV7-9) usage between donors. These findings describe one of the strongest primary peptide-specific CD8+ T cell responses yet recorded to a DNA-MVA prime-boost regimen and this may reflect the strong immunogenicity of mHAg peptides. Prime-boost vaccination in donors or patients may prove of substantial benefit in boosting graft-versus-leukaemia responses.

A recombinant measles virus vaccine strongly reduces SHIV viremia and virus reservoir establishment in macaques

Replicative vectors derived from live-attenuated measles virus (MV) carrying additional non-measles vaccine antigens have long demonstrated safety and immunogenicity in humans despite pre-existing immunity to measles. Here, we report the vaccination of cynomolgus macaques with MV replicative vectors expressing simian-human immunodeficiency virus Gag, Env, and Nef antigens (MV-SHIV Wt) either wild type or mutated in the immunosuppressive (IS) domains of Nef and Env antigens (MV-SHIV Mt). We found that the inactivation of Nef and Env IS domains by targeted mutations led to the induction of significantly enhanced post-prime cellular immune responses. After repeated challenges with low doses of SHIV-SF162p3, vaccinees were protected against high viremia, resulting in a 2-Log reduction in peak viremia, accelerated viral clearance, and a decrease -even complete protection for nearly half of the monkeys- in reservoir cell infection. This study demonstrates the potential of a replicative viral vector derived from the safe and widely used measles vaccine in the development of a future human vaccine against HIV-1.

Elucidating mechanisms of antitumor immunity mediated by live oncolytic vaccinia and heat-inactivated vaccinia

Background

Viral-based immunotherapy can overcome resistance to immune checkpoint blockade (ICB) and fill the unmet needs of many patients with cancer. Oncolytic viruses (OVs) are defined as engineered or naturally occurring viruses that selectively replicate in and kill cancer cells. OVs also induce antitumor immunity. The purpose of this study was to compare the antitumor effects of live oncolytic vaccinia viruses versus the inactivated versions and elucidate their underlying immunological mechanisms.

Methods

We engineered a replication-competent, oncolytic vaccinia virus (OV-GM) by inserting a murine GM-CSF gene into the thymidine kinase locus of a mutant vaccinia E3L∆83N, which lacks the Z-DNA-binding domain of vaccinia virulence factor E3. We compared the antitumor effects of intratumoral (IT) delivery of live OV-GM versus heat-inactivated OV-GM (heat-iOV-GM) in a murine B16-F10 melanoma bilateral implantation model. We also generated vvDD, a well-studied oncolytic vaccinia virus, and compared the antitumor effects of live vvDD vs heat-inactivated vvDD (heat-ivvDD) in a murine A20 B-cell lymphoma bilateral tumor implantation model.

Results

Heat-iOV-GM infection of dendritic cells (DCs) and tumor cells in vitro induced type I interferon and proinflammatory cytokines and chemokines, whereas live OV-GM did not. IT live OV-GM was less effective in generating systemic antitumor immunity compared with heat-iOV-GM. Similar to heat-iOV-GM, the antitumor effects of live OV-GM also require Batf3-dependent CD103⁺ dendritic cells. When combined with systemic delivery of ICB, IT heat-iOV-GM was more effective in eradicating tumors, compared with live OV-GM. IT heat-ivvDD was also more effective in treating murine A20 B-cell lymphoma, compared with live vvDD.

Conclusions

Tumor lysis induced by the replication of oncolytic vaccinia virus has a limited effect on the generation of systemic antitumor immunity. The activation of Batf3-dependent CD103⁺ DCs is critical for antitumor effects induced by both live OV-GM and heat-iOV-GM, with the latter being more potent than live OV-GM in inducing innate and adaptive immunity in both locally injected and distant, non-injected tumors. We propose that evaluations of both innate and adaptive immunity, induced by IT oncolytic viral immunotherapy at injected and non-injected tumors, should be included as potential biomarkers for host responses to viral therapy.

Efficacy and Safety of a Modified Vaccinia Ankara-NP+M1 Vaccine Combined with QIV in People Aged 65 and Older: A Randomised Controlled Clinical Trial (INVICTUS)

BACKGROUND

Pre-existing T cell responses to influenza have been correlated with improved clinical outcomes in natural history and human challenge studies. We aimed to determine the efficacy, safety and immunogenicity of a T-cell directed vaccine in older people.

METHODS

This was a multicentre, participant- and safety assessor-blinded, randomised, placebo-controlled trial of the co-administration of Modified Vaccinia Ankara encoding nucleoprotein and matrix protein 1 (MVA-NP+M1) and annual influenza vaccine in participants ≥ 65. The primary outcome was the number of days with moderate or severe influenza-like symptoms (ILS) during the influenza season.

RESULTS

846 of a planned 2030 participants were recruited in the UK prior to, and throughout, the 2017/18 flu season. There was no evidence of a difference in the reported rates of days of moderate or severe ILS during influenza-like illness episodes (unadjusted OR = 0.95, 95% CI: 0.54-1.69; adjusted OR = 0.91, 95% CI: 0.51-1.65). The trial was stopped after one season due to a change in the recommended annual flu vaccine, for which safety of the new combination had not been established. More participants in the MVA-NP+M1 group had transient moderate or severe pain, redness, and systemic responses in the first seven days.

CONCLUSION

The MVA-NP+M1 vaccine is well tolerated in those aged 65 years and over. Larger trials would be needed to determine potential efficacy.

AIDSVAX protein boost improves breadth and magnitude of vaccine-induced HIV-1 envelope-specific responses after a 7-year rest period

BACKGROUND

Eliciting durable humoral immunity with sufficient breadth and magnitude is important for HIV-1 vaccine design. The HVTN 114 vaccine trial evaluated different boost regimens administered after a 7-year rest period in participants previously enrolled in HVTN 205, who received either three MVA/HIV62B (MMM) or two DNA and two MVA/HIV62B (DDMM) injections; both vaccines expressed multiple HIV-1 antigens in non-infectious virus-like-particles. The primary objective of HVTN 114 was to assess the impact of a heterologous gp120 protein AIDSVAX B/E boost on the magnitude, breadth and durability of vaccine-induced immune responses.

METHODS

We enrolled 27 participants from HVTN 205 into five groups. Eight participants who previously received MMM were randomized and boosted with either MVA/HIV62B alone (T1; n = 4) or MVA/HIV62B and AIDSVAX B/E (T2; n = 4). Nineteen participants who received DDMM were randomized and boosted with MVA/HIV62B alone (T3; n = 6), MVA/HIV62B and AIDSVAX B/E (T4; n = 6), or AIDSVAX B/E alone (T5; n = 7). Boosts were at months 0 and 4. Participants were followed for safety and immunogenicity for 10 months and were pooled for analysis based on the regimen: MVA-only (T1 + T3), MVA + AIDSVAX (T2 + T4), and AIDSVAX-only (T5).

RESULTS

All regimens were safe and well-tolerated. Prior to the boost vaccination, binding antibody and CD4+T-cell responses were observed 7 years after HVTN 205 vaccinations. Late boosting with AIDSVAX, with or without MVA, resulted in high binding antibody responses to gp120 and V1V2 epitopes, with increased magnitude and breadth compared to those observed in HVTN 205. Late boosting with MVA, with or without AIDSVAX, resulted in increased gp140 and gp41 antibody responses and higher CD4+T-cell responses to Env and Gag.

CONCLUSIONS

Late boosting with AIDSVAX, alone or in combination with MVA, can broaden binding antibody responses and increase T-cell responses even years following the original MVA/HIV62B with or without DNA-priming vaccine.

One or two injections of MVA-vectored vaccine shields hACE2 transgenic mice from SARS-CoV-2 upper and lower respiratory tract infection

Modified vaccinia virus Ankara (MVA) is a replication-restricted smallpox vaccine, and numerous clinical studies of recombinant MVAs (rMVAs) as vectors for prevention of other infectious diseases, including COVID-19, are in progress. Here, we characterize rMVAs expressing the S protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Modifications of full-length S individually or in combination included two proline substitutions, mutations of the furin recognition site, and deletion of the endoplasmic retrieval signal. Another rMVA in which the receptor binding domain (RBD) is flanked by the signal peptide and transmembrane domains of S was also constructed. Each modified S protein was displayed on the surface of rMVA-infected cells and was recognized by anti-RBD antibody and soluble hACE2 receptor. Intramuscular injection of mice with the rMVAs induced antibodies, which neutralized a pseudovirus in vitro and, upon passive transfer, protected hACE2 transgenic mice from lethal infection with SARS-CoV-2, as well as S-specific CD3+CD8+IFNγ+ T cells. Antibody boosting occurred following a second rMVA or adjuvanted purified RBD protein. Immunity conferred by a single vaccination of hACE2 mice prevented morbidity and weight loss upon intranasal infection with SARS-CoV-2 3 wk or 7 wk later. One or two rMVA vaccinations also prevented detection of infectious SARS-CoV-2 and subgenomic viral mRNAs in the lungs and greatly reduced induction of cytokine and chemokine mRNAs. A low amount of virus was found in the nasal turbinates of only one of eight rMVA-vaccinated mice on day 2 and none later. Detection of low levels of subgenomic mRNAs in turbinates indicated that replication was aborted in immunized animals.

A modified vaccinia Ankara vector-based vaccine protects macaques from SARS-CoV-2 infection, immune pathology, and dysfunction in the lungs

A combination of vaccination approaches will likely be necessary to fully control the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Here, we show that modified vaccinia Ankara (MVA) vectors expressing membrane-anchored pre-fusion stabilized spike (MVA/S) but not secreted S1 induced strong neutralizing antibody responses against SARS-CoV-2 in mice. In macaques, the MVA/S vaccination induced strong neutralizing antibodies and CD8+ T cell responses, and conferred protection from SARS-CoV-2 infection and virus replication in the lungs as early as day 2 following intranasal and intratracheal challenge. Single-cell RNA sequencing analysis of lung cells on day 4 after infection revealed that MVA/S vaccination also protected macaques from infection-induced inflammation and B cell abnormalities and lowered induction of interferon-stimulated genes. These results demonstrate that MVA/S vaccination induces neutralizing antibodies and CD8+ T cells in the blood and lungs and is a potential vaccine candidate for SARS-CoV-2.

Ebola-GP DNA Prime rAd5-GP Boost: Influence of Prime Frequency and Prime/Boost Time Interval on the Immune Response in Non-human Primates

Heterologous prime-boost immunization regimens are a common strategy for many vaccines. DNA prime rAd5-GP boost immunization has been demonstrated to protect non-human primates against a lethal challenge of Ebola virus, a pathogen that causes fatal hemorrhagic disease in humans. This protection correlates with antibody responses and is also associated with IFNγ⁺ TNFα⁺ double positive CD8⁺ T-cells. In this study, we compared single DNA vs. multiple DNA prime immunizations, and short vs. long time intervals between the DNA prime and the rAd5 boost to evaluate the impact of these different prime-boost strategies on vaccine-induced humoral and cellular responses in non-human primates. We demonstrated that DNA/rAd5 prime-boost strategies can be tailored to induce either CD4⁺ T-cell or CD8⁺ T-cell dominant responses while maintaining a high magnitude antibody response. Additionally, a single DNA prime immunization generated a stable memory response that could be boosted by rAd5 3 years later. These results suggest DNA/rAd5 prime-boost provides a flexible platform that can be fine-tuned to generate desirable T-cell memory responses.

MVA Vector Vaccines Inhibit SARS CoV-2 Replication in Upper and Lower Respiratory Tracts of Transgenic Mice and Prevent Lethal Disease

Replication-restricted modified vaccinia virus Ankara (MVA) is a licensed smallpox vaccine and numerous clinical studies investigating recombinant MVAs (rMVAs) as vectors for prevention of other infectious diseases have been completed or are in progress. Two rMVA COVID-19 vaccine trials are at an initial stage, though no animal protection studies have been reported. Here, we characterize rMVAs expressing the S protein of CoV-2. Modifications of full length S individually or in combination included two proline substitutions, mutations of the furin recognition site and deletion of the endoplasmic retrieval signal. Another rMVA in which the receptor binding domain (RBD) flanked by the signal peptide and transmembrane domains of S was also constructed. Each modified S protein was displayed on the surface of rMVA-infected human cells and was recognized by anti-RBD antibody and by soluble hACE2 receptor. Intramuscular injection of mice with the rMVAs induced S-binding and pseudovirus-neutralizing antibodies. Boosting occurred following a second homologous rMVA but was higher with adjuvanted purified RBD protein. Weight loss and lethality following intranasal infection of transgenic hACE2 mice with CoV-2 was prevented by one or two immunizations with rMVAs or by passive transfer of serum from vaccinated mice. One or two rMVA vaccinations also prevented recovery of infectious CoV-2 from the lungs. A low amount of virus was detected in the nasal turbinates of only one of eight rMVA-vaccinated mice on day 2 and none later. Detection of subgenomic mRNA in turbinates on day 2 only indicated that replication was abortive in immunized animals.

Poststudy Point-of-Care Oral Fluid Testing in Human Immunodeficiency Virus-1 Vaccinees

Background

Experimental human immunodeficiency virus (HIV)-1 vaccines frequently elicit antibodies against HIV-1 that may react with commonly used HIV diagnostic tests, a phenomenon known as vaccine-induced seropositivity/seroreactivity (VISP/VISR). We sought to determine, under clinic conditions, whether a patient-controlled HIV test, OraQuick ADVANCE Rapid HIV-1/2 Antibody Test, detected HIV-1 vaccine-induced antibodies.

Methods

Plasma assessment of HIV-1 cross-reactivity was examined in end-of-study samples from 57 healthy, HIV-uninfected participants who received a candidate vaccine that has entered Phase 2B and 3 testing. We also screened 120 healthy, HIV-uninfected, unblinded HIV-1 vaccine participants with VISP/VISR for an assessment using saliva. These participants came from 21 different parent vaccine protocols representing 17 different vaccine regimens, all of which contained an HIV-1 envelope immunogen. OraQuick ADVANCE was compared with results from concurrent blood samples using a series of commercial HIV screening immunoassays.

Results

Fifty-seven unique participant plasma samples were assayed in vitro, and only 1 (1.8%) was reactive by OraQuick ADVANCE. None of the 120 clinic participants (0%; 95% confidence interval, 0% to 3.7%) tested positive by OraQuick ADVANCE, and all were confirmed to be uninfected by HIV-1 viral ribonucleic acid testing. One hundred eighteen of the 120 (98.3%) participants had a reactive HIV test for VISP/VISR: 77 (64%) had at least 1 reactive fourth-generation HIV-1 diagnostic test (P < .0001 vs no reactive OraQuick ADVANCE results), and 41 (34%) only had a reactive test by the less specific third-generation Abbott Prism assay.

Conclusions

These data suggest that this widely available patient-controlled test has limited reactivity to HIV-1 antibodies elicited by these candidate HIV-1 vaccines.

Frequent Anti-V1V2 Responses Induced by HIV-DNA Followed by HIV-MVA with or without CN54rgp140/GLA-AF in Healthy African Volunteers

Antibody responses that correlated with reduced risk of HIV acquisition in the RV144 efficacy trial were assessed in healthy African volunteers who had been primed three times with HIV-DNA (subtype A, B, C) and then randomized into two groups; group 1 was boosted twice with HIV-MVA (CRF01_AE) and group 2 with the same HIV-MVA coadministered with subtype C envelope (Env) protein (CN54rgp140/GLA-AF). The fine specificity of plasma Env-specific antibody responses was mapped after the final vaccination using linear peptide microarray technology. Binding IgG antibodies to the V1V2 loop in CRF01_AE and subtype C Env and Env-specific IgA antibodies were determined using enzyme-linked immunosorbent assay. Functional antibody-dependent cellular cytotoxicity (ADCC)-mediating antibody responses were measured using luciferase assay. Mapping of linear epitopes within HIV-1 Env demonstrated strong targeting of the V1V2, V3, and the immunodominant region in gp41 in both groups, with additional recognition of two epitopes located in the C2 and C4 regions in group 2. A high frequency of V1V2-specific binding IgG antibody responses was detected to CRF01_AE (77%) and subtype C antigens (65%). In conclusion, coadministration of CN54rgp140/GLA-AF with HIV-MVA did not increase the frequency, breadth, or magnitude of anti-V1V2 responses or ADCC-mediating antibodies induced by boosting with HIV-MVA alone.

Optimal priming of poxvirus vector (NYVAC)-based HIV vaccine regimens for T cell responses requires three DNA injections. Results of the randomized multicentre EV03/ANRS VAC20 Phase I/II Trial

DNA vectors have been widely used as a priming of poxvirus vaccine in prime/boost regimens. Whether the number of DNA impacts qualitatively or quantitatively the immune response is not fully explored. With the aim to reinforce T-cell responses by optimizing the prime-boost regimen, the multicentric EV03/ANRS VAC20 phase I/II trial, randomized 147 HIV-negative volunteers to either 3xDNA plus 1xNYVAC (weeks 0, 4, 8 plus 24; n = 74) or to 2xDNA plus 2xNYVAC (weeks 0, 4 plus 20, 24; n = 73) groups. T-cell responses (IFN-γ ELISPOT) to at least one peptide pool were higher in the 3xDNA than the 2xDNA groups (91% and 80% of vaccinees) (P = 0.049). In the 3xDNA arm, 26 (37%) recipients developed a broader T-cell response (Env plus at least to one of the Gag, Pol, Nef pools) than in the 2xDNA (15; 22%) arms (primary endpoint; P = 0.047) with a higher magnitude against Env (at week 26) (P<0.001). In both groups, vaccine regimens induced HIV-specific polyfunctional CD4 and CD8 T cells and the production of Th1, Th2 and Th17/IL-21 cytokines. Antibody responses were also elicited in up to 81% of vaccines. A higher percentage of IgG responders was noted in the 2xDNA arm compared to the 3xDNA arm, while the 3xDNA group tended to elicit a higher magnitude of IgG3 response against specific Env antigens. We show here that the modulation of the prime strategy, without modifying the route or the dose of administration, or the combination of vectors, may influence the quality of the responses.

Development of a safe and effective HIV-1 vaccine would undoubtedly be the best solution for the ultimate control of the worldwide AIDS pandemic. To date, only one large phase III trial (RV144 Thai study) showed a partial and modest protection against HIV infection. This result raised hope in the field and encouraged the development of vaccines or strategies in order to improve vaccine efficacy. Several vaccine strategies designed to elicit broad HIV-specific T cells and/or neutralizing antibodies to prevent HIV-1 transmission are under evaluation. Among diverse candidate vaccines, the safety and immunogenicity of multi-gene DNA-based and Pox-virus derived vaccines have been evaluated in several clinical studies. The present study was designed to optimize the combination of these two vaccines with the aim of determining the optimal number of DNA primes for a poxvirus-based HIV vaccine regimen. We show here that the prime boost combination is highly immunogenic and that the number of DNA primes induces differentially T cell and antibody responses. A better priming of poxvirus-based vaccine regimens for T cells is obtained with 3 DNA injections. Our results contribute and extend data of several preclinical studies pointing out the potential interest of DNA as a prime capable not only of improving immune responses but also of imprinting the long-term responses to boost vaccines.

Advances in therapeutic vaccines for treating human papillomavirus-related cervical intraepithelial neoplasia

AIM

Human papillomavirus (HPV) is the etiologic agent of the majority of cervical intraepithelial lesions (CIN) and cervical cancers. While prophylactic HPV vaccines prevent infections from the main high-risk HPV types associated with cervical cancer, alternative nonsurgical and nonablative therapeutics to treat HPV infection and preinvasive HPV diseases have been experimentally investigated. Therapeutic vaccines are an emerging investigational strategy. This review aims to introduce the results of the main clinical trials on the use of therapeutic vaccines for treating HPV infection and -related CIN, reporting the ongoing studies on this field.

METHODS

Data research was conducted using MEDLINE, EMBASE, Web of Sciences, Scopus, ClinicalTrial.gov, OVID and Cochrane Library querying for all articles related to therapeutic vaccines for the treatment of HPV-related CIN. Selection criteria included randomized clinical trials, nonrandomized controlled studies and review articles.

RESULTS

Preliminary data are available on the evaluation of therapeutic vaccines for treating cervical HPV infections and CIN. Despite having in vitro demonstrated to obtain humoral and cytotoxic responses, therapeutic vaccines have not yet clinically demonstrated consistent success; moreover, each class of therapeutic vaccines has advantages and limitations. Early clinical data are available in the literature for these compounds, except for MVA E2, which reached the phase III clinical trial status, obtaining positive clinical outcomes.

CONCLUSION

Despite promising results, to date many obstacles are still present before hypothesize an introduction in the clinical practice within the next years. Further studies will draw a definitive conclusion on the role of therapeutic vaccines in this setting.

Antibody and cellular responses to HIV vaccine regimens with DNA plasmid as compared with ALVAC priming: An analysis of two randomized controlled trials

BACKGROUND

DNA plasmids promise a pragmatic alternative to viral vectors for prime-boost HIV-1 vaccines. We evaluated DNA plasmid versus canarypox virus (ALVAC) primes in 2 randomized, double-blind, placebo-controlled trials in southern Africa with harmonized trial designs. HIV Vaccine Trials Network (HVTN) 111 tested DNA plasmid prime by needle or needleless injection device (Biojector) and DNA plasmid plus gp120 protein plus MF59 adjuvant boost. HVTN 100 tested ALVAC prime and ALVAC plus gp120 protein plus MF59 adjuvant boost (same protein/adjuvant as HVTN 111) by needle.

METHODS AND FINDINGS

The primary endpoints for this analysis were binding antibody (bAb) responses to HIV antigens (gp120 from strains ZM96, 1086, and TV1; variable 1 and 2 [V1V2] regions of gp120 from strains TV1, 1086, and B.CaseA, as 1086 V1V2 and B.CaseA were correlates of risk in the RV144 efficacy trial), neutralizing antibody (nAb) responses to pseudoviruses TV1c8.2 and MW925.26, and cellular responses to vaccine-matched antigens (envelope [Env] from strains ZM96, 1086, and TV1; and Gag from strains LAI and ZM96) at month 6.5, two weeks after the fourth vaccination. Per-protocol cohorts included vaccine recipients from HVTN 100 (n = 186, 60% male, median age 23 years) enrolled between February 9, 2015, and May 26, 2015 and from HVTN 111 (n = 56, 48% male, median age 24 years) enrolled between June 21, 2016, and July 13, 2017. IgG bAb response rates were 100% to 3 Env gp120 antigens in both trials. Response rates to V1V2 were lower and similar in both trials except to vaccine-matched 1086 V1V2, with rates significantly higher for the DNA-primed regimen than the ALVAC-primed regimen: 96.6% versus 72.7% (difference = 23.9%, 95% CI 15.6%-32.2%, p < 0.001). Among positive responders, bAb net mean fluorescence intensity (MFI) was significantly higher with the DNA-primed regimen than ALVAC-primed for 1086 V1V2 (geometric mean [GM] 2,833.3 versus 1,200.9; ratio = 2.36, 95% CI 1.42-3.92, p < 0.001) and B.CaseA V1V2 (GM 2314.0 versus 744.6, ratio = 3.11, 95% CI 1.51-6.38, p = 0.002). nAb response rates were >98% in both trials, with significantly higher 50% inhibitory dilution (ID50) among DNA-primed positive responders (n = 53) versus ALVAC-primed (n = 182) to tier 1A MW965.26 (GM 577.7 versus 265.7, ratio = 2.17, 95% CI 1.67-2.83, p < 0.001) and to TV1c8.2 (GM 187.3 versus 100.4, ratio = 1.87, 95% CI 1.48-2.35, p < 0.001). CD4+ T-cell response rates were significantly higher with DNA plasmid prime via Biojector than ALVAC prime (91.4% versus 52.8%, difference = 38.6%, 95% CI 20.5%-56.6%, p < 0.001 for ZM96.C; 88.0% versus 43.1%, difference = 44.9%, 95% CI 26.7%-63.1%, p < 0.001 for 1086.C; 55.5% versus 2.2%, difference = 53.3%, 95% CI 23.9%-82.7%, p < 0.001 for Gag LAI/ZM96). The study's main limitations include the nonrandomized comparison of vaccines from 2 different trials, the lack of data on immune responses to other non-vaccine-matched antigens, and the uncertain clinical significance of the observed immunological effects.

CONCLUSIONS

In this study, we found that further investigation of DNA/protein regimens is warranted given enhanced immunogenicity to the V1V2 correlates of decreased HIV-1 acquisition risk identified in RV144, the only HIV vaccine trial to date to show any efficacy.

Human Immunodeficiency Virus C.1086 Envelope gp140 Protein Boosts following DNA/Modified Vaccinia Virus Ankara Vaccination Fail To Enhance Heterologous Anti-V1V2 Antibody Response and Protection against Clade C Simian-Human Immunodeficiency Virus Challenge

The RV144 human immunodeficiency virus type 1 (HIV-1) vaccine trial showed a strong association between anti-gp70 V1V2 scaffold (V1V2) and anti-V2 hot spot peptide (V2 HS) antibody responses and reduced risk of HIV infection. Accordingly, a primary goal for HIV vaccines is to enhance the magnitude and breadth of V1V2 and V2 HS antibody responses in addition to neutralizing antibodies. Here, we tested the immunogenicity and efficacy of HIV-1 C.1086 gp140 boosts administered sequentially after priming with CD40L-adjuvanted DNA/simian-human immunodeficiency virus (SHIV) and boosting with modified vaccinia virus Ankara (MVA)-SHIV vaccines in rhesus macaques. The DNA/MVA vaccination induced robust vaccine-specific CD4 and CD8 T cell responses with a polyfunctional profile. Two gp140 booster immunizations induced very high levels (∼2 mg/ml) of gp140 binding antibodies in serum, with strong reactivity directed against the homologous (C.1086) V1V2, V2 HS, V3, and gp41 immunodominant (ID) proteins. However, the vaccine-induced antibody showed 10-fold (peak) and 32-fold (prechallenge) weaker binding to the challenge virus (SHIV1157ipd3N4) V1V2 and failed to bind to the challenge virus V2 HS due to a single amino acid change. Point mutations in the immunogen V2 HS to match the V2 HS in the challenge virus significantly diminished the binding of vaccine-elicited antibodies to membrane-anchored gp160. Both vaccines failed to protect from infection following repeated SHIV1157ipd3N4 intrarectal challenges. However, only the protein-boosted animals showed enhanced viral control. These results demonstrate that C.1086 gp140 protein immunizations administered following DNA/MVA vaccination do not significantly boost heterologous V1V2 and V2 HS responses and fail to enhance protection against heterologous SHIV challenge.IMPORTANCE HIV, the virus that causes AIDS, is responsible for millions of infections and deaths annually. Despite intense research for the past 25 years, there remains no safe and effective vaccine available. The significance of this work is in identifying the pros and cons of adding a protein boost to an already well-established DNA/MVA HIV vaccine that is currently being tested in the clinic. Characterizing the effects of the protein boost can allow researchers going forward to design vaccines that generate responses that will be more effective against HIV. Our results in rhesus macaques show that boosting with a specific HIV envelope protein does not significantly boost antibody responses that were identified as immune correlates of protection in a moderately successful RV144 HIV vaccine trial in humans and highlight the need for the development of improved HIV envelope immunogens.

First-in-Human Randomized, Controlled Trial of Mosaic HIV-1 Immunogens Delivered via a Modified Vaccinia Ankara Vector

Background

Mosaic immunogens are bioinformatically engineered human immunodeficiency virus type 1 (HIV-1) sequences designed to elicit clade-independent coverage against globally circulating HIV-1 strains.

Methods

This phase 1, double-blinded, randomized, placebo-controlled trial enrolled healthy HIV-uninfected adults who received 2 doses of a modified vaccinia Ankara (MVA)-vectored HIV-1 bivalent mosaic immunogen vaccine or placebo on days 0 and 84. Two groups were enrolled: those who were HIV-1 vaccine naive (n = 15) and those who had received an HIV-1 vaccine (Ad26.ENVA.01) 4-6 years earlier (n = 10). We performed prespecified blinded cellular and humoral immunogenicity analyses at days 0, 14, 28, 84, 98, 112, 168, 270, and 365.

Results

All 50 planned vaccinations were administered. Vaccination was safe and generally well tolerated. No vaccine-related serious adverse events occurred. Both cellular and humoral cross-clade immune responses were elicited after 1 or 2 vaccinations in all participants in the HIV-1 vaccine-naive group. Env-specific responses were induced after a single immunization in nearly all subjects who had previously received the prototype Ad26.ENVA.01 vaccine.

Conclusions

No safety concerns were identified, and multiclade HIV-1-specific immune responses were elicited.

Clinical Trials Registration

NCT02218125.

A Single Dose of Modified Vaccinia Ankara Expressing Lassa Virus-like Particles Protects Mice from Lethal Intra-cerebral Virus Challenge

Lassa fever surpasses Ebola, Marburg, and all other hemorrhagic fevers except Dengue in its public health impact. Caused by Lassa virus (LASV), the disease is a scourge on populations in endemic areas of West Africa, where reported incidence is higher. Here, we report construction, characterization, and preclinical efficacy of a novel recombinant vaccine candidate GEO-LM01. Constructed in the Modified Vaccinia Ankara (MVA) vector, GEO-LM01 expresses the glycoprotein precursor (GPC) and zinc-binding matrix protein (Z) from the prototype Josiah strain lineage IV. When expressed together, GP and Z form Virus-Like Particles (VLPs) in cell culture. Immunogenicity and efficacy of GEO-LM01 was tested in a mouse challenge model. A single intramuscular dose of GEO-LM01 protected 100% of CBA/J mice challenged with a lethal dose of ML29, a Mopeia/Lassa reassortant virus, delivered directly into the brain. In contrast, all control animals died within one week. The vaccine induced low levels of antibodies but Lassa-specific CD4+ and CD8+ T cell responses. This is the first report showing that a single dose of a replication-deficient MVA vector can confer full protection against a lethal challenge with ML29 virus.

Optimized Mucosal Modified Vaccinia Virus Ankara Prime/Soluble gp120 Boost HIV Vaccination Regimen Induces Antibody Responses Similar to Those of an Intramuscular Regimen

The benefits of mucosal vaccines over injected vaccines are difficult to ascertain, since mucosally administered vaccines often induce serum antibody responses of lower magnitude than those induced by injected vaccines. This study aimed to determine if mucosal vaccination using a modified vaccinia virus Ankara expressing human immunodeficiency virus type 1 (HIV-1) gp120 (MVAgp120) prime and a HIV-1 gp120 protein boost could be optimized to induce serum antibody responses similar to those induced by an intramuscularly (i.m.) administered MVAgp120 prime/gp120 boost to allow comparison of an i.m. immunization regimen to a mucosal vaccination regimen for the ability to protect against a low-dose rectal simian-human immunodeficiency virus (SHIV) challenge. A 3-fold higher antigen dose was required for intranasal (i.n.) immunization with gp120 to induce serum anti-gp120 IgG responses not significantly different than those induced by i.m. immunization. gp120 fused to the adenovirus type 2 fiber binding domain (gp120-Ad2F), a mucosal targeting ligand, exhibited enhanced i.n. immunogenicity compared to gp120. MVAgp120 was more immunogenic after i.n. delivery than after gastric or rectal delivery. Using these optimized vaccines, an i.n. MVAgp120 prime/combined i.m. (gp120) and i.n. (gp120-Ad2F) boost regimen (i.n./i.m.-plus-i.n.) induced serum anti-gp120 antibody titers similar to those induced by the intramuscular prime/boost regimen (i.m./i.m.) in rabbits and nonhuman primates. Despite the induction of similar systemic anti-HIV-1 antibody responses, neither the i.m./i.m. nor the i.n./i.m.-plus-i.n. regimen protected against a repeated low-dose rectal SHIV challenge. These results demonstrate that immunization regimens utilizing the i.n. route are able to induce serum antigen-specific antibody responses similar to those induced by systemic immunization.IMPORTANCE Mucosal vaccination is proposed as a method of immunization able to induce protection against mucosal pathogens that is superior to protection provided by parenteral immunization. However, mucosal vaccination often induces serum antigen-specific immune responses of lower magnitude than those induced by parenteral immunization, making the comparison of mucosal and parenteral immunization difficult. We identified vaccine parameters that allowed an immunization regimen consisting of an i.n. prime followed by boosters administered by both i.n. and i.m. routes to induce serum antibody responses similar to those induced by i.m. prime/boost vaccination. Additional studies are needed to determine the potential benefit of mucosal immunization for HIV-1 and other mucosally transmitted pathogens.

Prime-Boost Immunizations with DNA, Modified Vaccinia Virus Ankara, and Protein-Based Vaccines Elicit Robust HIV-1 Tier 2 Neutralizing Antibodies against the CAP256 Superinfecting Virus

A vaccine regimen that elicits broadly neutralizing antibodies (bNAbs) is a major goal in HIV-1 vaccine research. In this study, we assessed the immunogenicity of the CAP256 superinfecting viral envelope (CAP256 SU) protein delivered by modified vaccinia virus Ankara (MVA) and DNA vaccines in different prime-boost combinations followed by a soluble protein (P) boost. The envelope protein (Env) contained a flexible glycine linker and I559P mutation. Trimer-specific bNAbs PGT145, PG16, and CAP256 VRC26_08 efficiently bound to the membrane-bound CAP256 envelope expressed on the surface of cells transfected or infected with the DNA and MVA vaccines. The vaccines were tested in two different vaccination regimens in rabbits. Both regimens elicited autologous tier 2 neutralizing antibodies (NAbs) and high-titer binding antibodies to the matching CAP256 Env and CAP256 V1V2 loop scaffold. The immunogenicity of DNA and MVA vaccines expressing membrane-bound Env alone was compared to that of Env stabilized in a more native-like conformation on the surface of Gag virus-like particles (VLPs). The inclusion of Gag in the DNA and MVA vaccines resulted in earlier development of tier 2 NAbs for both vaccination regimens. In addition, a higher proportion of the rabbits primed with DNA and MVA vaccines that included Gag developed tier 2 NAbs than did those primed with vaccine expressing Env alone. Previously, these DNA and MVA vaccines expressing subtype C mosaic HIV-1 Gag were shown to elicit strong T cell responses in mice. Here we show that when the CAP256 SU envelope protein is included, these vaccines elicit autologous tier 2 NAbs.IMPORTANCE A vaccine is urgently needed to combat HIV-1, particularly in sub-Saharan Africa, which remains disproportionately affected by the AIDS pandemic and accounts for the majority of new infections and AIDS-related deaths. In this study, two different vaccination regimens were compared. Rabbits that received two DNA primes followed by two modified vaccinia virus Ankara (MVA) and two protein inoculations developed better immune responses than those that received two MVA and three protein inoculations. In addition, DNA and MVA vaccines that expressed mosaic Gag VLPs presenting a stabilized Env antigen elicited better responses than Env alone, which supports the inclusion of Gag VLPs in an HIV-1 vaccine.

Kopycinski J, Gilmour J, Kumar S, Muthu M, Subramaniam S, Swaminathan S, Prasad Tripathy S, Luke HE. Induction and maintenance of bi-functional (IFN-γ + IL-2+ and IL-2+ TNF-α+) T cell responses by DNA prime MVA boosted subtype C prophylactic vaccine tested in a Phase I trial in India

Effective vaccine design relies on accurate knowledge of protection against a pathogen, so as to be able to induce relevant and effective protective responses against it. An ideal Human Immunodeficiency virus (HIV) vaccine should induce humoral as well as cellular immune responses to prevent initial infection of host cells or limit early events of viral dissemination. A Phase I HIV-1 prophylactic vaccine trial sponsored by the International AIDS Vaccine Initiative (IAVI) was conducted in India in 2009.The trial tested a HIV-1 subtype C vaccine in a prime-boost regimen, comprising of a DNA prime (ADVAX) and Modified Vaccine Ankara (MVA) (TBC-M4) boost. The trial reported that the vaccine regimen was safe, well tolerated, and resulted in enhancement of HIV-specific immune responses. However, preliminary immunological studies were limited to vaccine-induced IFN-γ responses against the Env and Gag peptides. The present study is a retrospective study to characterize in detail the nature of the vaccine-induced cell mediated immune responses among volunteers, using Peripheral Blood Mononuclear Cells (PBMC) that were archived during the trial. ELISpot was used to measure IFN-γ responses and polyfunctional T cells were analyzed by intracellular multicolor flow cytometry. It was observed that DNA priming and MVA boosting induced Env and Gag specific bi-functional and multi-functional CD4⁺ and CD8⁺ T cells expressing IFN-γ, TNF-α and IL-2. The heterologous prime-boost regimen appeared to be slightly superior to the homologous prime-boost regimen in inducing favorable cell mediated immune responses. These results suggest that an in-depth analysis of vaccine-induced cellular immune response can aid in the identification of correlates of an effective immunogenic response, and inform future design of HIV vaccines.

Clade C HIV-1 Envelope Vaccination Regimens Differ in Their Ability To Elicit Antibodies with Moderate Neutralization Breadth against Genetically Diverse Tier 2 HIV-1 Envelope Variants

The goals of preclinical HIV vaccine studies in nonhuman primates are to develop and test different approaches for their ability to generate protective immunity. Here, we compared the impact of 7 different vaccine modalities, all expressing the HIV-1 1086.C clade C envelope (Env), on (i) the magnitude and durability of antigen-specific serum antibody responses and (ii) autologous and heterologous neutralizing antibody capacity. These vaccination regimens included immunization with different combinations of DNA, modified vaccinia virus Ankara (MVA), soluble gp140 protein, and different adjuvants. Serum samples collected from 130 immunized monkeys at two key time points were analyzed using the TZM-bl cell assay: at 2 weeks after the final immunization (week 40/41) and on the day of challenge (week 58). Key initial findings were that inclusion of a gp140 protein boost had a significant impact on the magnitude and durability of Env-specific IgG antibodies, and addition of 3M-052 adjuvant was associated with better neutralizing activity against the SHIV1157ipd3N4 challenge virus and a heterologous HIV-1 CRF01 Env, CNE8. We measured neutralization against a panel of 12 tier 2 Envs using a newly described computational tool to quantify serum neutralization potency by factoring in the predetermined neutralization tier of each reference Env. This analysis revealed modest neutralization breadth, with DNA/MVA immunization followed by gp140 protein boosts in 3M-052 adjuvant producing the best scores. This study highlights that protein-containing regimens provide a solid foundation for the further development of novel adjuvants and inclusion of trimeric Env immunogens that could eventually elicit a higher level of neutralizing antibody breadth.IMPORTANCE Despite much progress, we still do not have a clear understanding of how to elicit a protective neutralizing antibody response against HIV-1 through vaccination. There have been great strides in the development of envelope immunogens that mimic the virus particle, but less is known about how different vaccination modalities and adjuvants contribute to shaping the antibody response. We compared seven different vaccines that were administered to rhesus macaques and that delivered the same envelope protein through various modalities and with different adjuvants. The results demonstrate that some vaccine components are better than others at eliciting neutralizing antibodies with breadth.

Viral Replicative Capacity, Antigen Availability via Hematogenous Spread, and High TFH:TFR Ratios Drive Induction of Potent Neutralizing Antibody Responses

Live viral vaccines elicit protective, long-lived humoral immunity, but the underlying mechanisms through which this occurs are not fully elucidated. Generation of affinity matured, long-lived protective antibody responses involve close interactions between T follicular helper (T_FH) cells, germinal center (GC) B cells, and T follicular regulatory (T_FR) cells. We postulated that escalating concentrations of antigens from replicating viruses or live vaccines, spread through the hematogenous route, are essential for the induction and maintenance of long-lived protective antibody responses. Using replicating and poorly replicating or nonreplicating orthopox and influenza A viruses, we show that the magnitude of TFH cell, GC B cell, and neutralizing antibody responses is directly related to virus replicative capacity. Further, we have identified that both lymphoid and circulating T_FH:T_FR cell ratios during the peak GC response can be used as an early predictor of protective, long-lived antibody response induction. Finally, administration of poorly or nonreplicating viruses to allow hematogenous spread generates significantly stronger T_FH:T_FR ratios and robust T_FH, GC B cell and neutralizing antibody responses.IMPORTANCE Neutralizing antibody response is the best-known correlate of long-term protective immunity for most of the currently licensed clinically effective viral vaccines. However, the host immune and viral factors that are critical for the induction of robust and durable antiviral humoral immune responses are not well understood. Our study provides insight into the dynamics of key cellular mediators of germinal center reaction during live virus infections and the influence of viral replicative capacity on the magnitude of antiviral antibody response and effector function. The significance of our study lies in two key findings. First, the systemic spread of even poorly replicating or nonreplicating viruses to mimic the spread of antigens from replicating viruses due to escalating antigen concentration is fundamental to the induction of durable antibody responses. Second, the T_FH:T_FR ratio may be used as an early predictor of protective antiviral humoral immune responses long before memory responses are generated.

HIV-1 vaccination by needle-free oral injection induces strong mucosal immunity and protects against SHIV challenge

The oral mucosa is an attractive site for mucosal vaccination, however the thick squamous epithelium limits antigen uptake. Here we utilize a modified needle-free injector to deliver immunizations to the sublingual and buccal (SL/B) tissue of rhesus macaques. Needle-free SL/B vaccination with modified vaccinia Ankara (MVA) and a recombinant trimeric gp120 protein generates strong vaccine-specific IgG responses in serum as well as vaginal, rectal and salivary secretions. Vaccine-induced IgG responses show a remarkable breadth against gp70-V1V2 sequences from multiple clades of HIV-1. In contrast, topical SL/B immunizations generates minimal IgG responses. Following six intrarectal pathogenic SHIV-SF162P3 challenges, needle-free but not topical immunization results in a significant delay of acquisition of infection. Delay of infection correlates with non-neutralizing antibody effector function, Env-specific CD4+ T-cell responses, and gp120 V2 loop specific antibodies. These results demonstrate needle-free MVA/gp120 oral vaccination as a practical and effective route to induce protective immunity against HIV-1.

Optimizing the immunogenicity of HIV prime-boost DNA-MVA-rgp140/GLA vaccines in a phase II randomized factorial trial design

Background

We evaluated the safety and immunogenicity of (i) an intradermal HIV-DNA regimen given with/without intradermal electroporation (EP) as prime and (ii) the impact of boosting with modified vaccinia virus Ankara (HIV-MVA) administered with or without subtype C CN54rgp140 envelope protein adjuvanted with Glucopyranosyl Lipid A (GLA-AF) in volunteers from Tanzania and Mozambique.

Methods

Healthy HIV-uninfected adults (N = 191) were randomized twice; first to one of three HIV-DNA intradermal priming regimens by needle-free ZetaJet device at weeks 0, 4 and 12 (Group I: 2x0.1mL [3mg/mL], Group II: 2x0.1mL [3mg/mL] plus EP, Group III: 1x0.1mL [6mg/mL] plus EP). Second the same volunteers received 10⁸ pfu HIV-MVA twice, alone or combined with CN54rgp140/GLA-AF, intramuscularly by syringe, 16 weeks apart. Additionally, 20 volunteers received saline placebo.

Results

Vaccinations and electroporation did not raise safety concerns. After the last vaccination, the overall IFN-γ ELISpot response rate to either Gag or Env was 97%. Intradermal electroporation significantly increased ELISpot response rates to HIV-DNA-specific Gag (66% group I vs. 86% group II, p = 0.026), but not to the HIV-MVA vaccine-specific Gag or Env peptide pools nor the magnitude of responses. Co-administration of rgp140/GLA-AF with HIV-MVA did not impact the frequency of binding antibody responses against subtype B gp160, C gp140 or E gp120 antigens (95%, 99%, 79%, respectively), but significantly enhanced the magnitude against subtype B gp160 (2700 versus 300, p<0.001) and subtype C gp140 (24300 versus 2700, p<0.001) Env protein. At relatively low titers, neutralizing antibody responses using the TZM-bl assay were more frequent in vaccinees given adjuvanted protein boost.

Conclusion

Intradermal electroporation increased DNA-induced Gag response rates but did not show an impact on Env-specific responses nor on the magnitude of responses. Co-administration of HIV-MVA with rgp140/GLA-AF significantly enhanced antibody responses.

One Group's Historical Reflections on DNA Vaccine Development

DNA vaccines were pioneered by several groups in the early 1990s. This article presents the reflections of one of these groups on their work with retroviral vectors in chickens that contributed to the discovery and early development of DNA vaccines. Although the findings were initially met with skepticism, the work presented here combined with that of others founded a new method of vaccination: the direct inoculation of purified DNA encoding the target antigen.

DNA Vaccine-Induced Long-Lasting Cytotoxic T Cells Targeting Conserved Elements of Human Immunodeficiency Virus Gag Are Boosted Upon DNA or Recombinant Modified Vaccinia Ankara Vaccination

DNA-based vaccines able to induce efficient cytotoxic T-cell responses targeting conserved elements (CE) of human immunodeficiency virus type 1 (HIV-1) Gag have been developed. These CE were selected by stringent conservation, the ability to induce T-cell responses with broad human leukocyte antigen coverage, and the association between recognition of CE epitopes and viral control in HIV-infected individuals. Based on homology to HIV, a simian immunodeficiency virus p27^gag CE DNA vaccine has also been developed. This study reports on the durability of the CE-specific T-cell responses induced by HIV and simian immunodeficiency virus CE DNA-based prime/boost vaccine regimens in rhesus macaques, and shows that the initially primed CE-specific T-cell responses were efficiently boosted by a single CE DNA vaccination after the long rest period (up to 2 years). In another cohort of animals, the study shows that a single inoculation with non-replicating recombinant Modified Vaccinia Ankara (rMVA62B) also potently boosted CE-specific responses after around 1.5 years of rest. Both CE DNA and rMVA62B booster vaccinations increased the magnitude and cytotoxicity of the CE-specific responses while maintaining the breadth of CE recognition. Env produced by rMVA62B did not negatively interfere with the recall of the Gag CE responses. rMVA62B could be beneficial to further boosting the immune response to Gag in humans. Vaccine regimens that employ CE DNA as a priming immunogen hold promise for application in HIV prevention and therapy.

A Trimeric HIV-1 Envelope gp120 Immunogen Induces Potent and Broad Anti-V1V2 Loop Antibodies against HIV-1 in Rabbits and Rhesus Macaques

Trimeric HIV-1 envelope (Env) immunogens are attractive due to their ability to display quaternary epitopes targeted by broadly neutralizing antibodies (bNAbs) while obscuring unfavorable epitopes. Results from the RV144 trial highlighted the importance of vaccine-induced HIV-1 Env V1V2-directed antibodies, with key regions of the V2 loop as targets for vaccine-mediated protection. We recently reported that a trimeric JRFL-gp120 immunogen, generated by inserting an N-terminal trimerization domain in the V1 loop region of a cyclically permuted gp120 (cycP-gp120), induces neutralizing activity against multiple tier-2 HIV-1 isolates in guinea pigs in a DNA prime/protein boost approach. Here, we tested the immunogenicity of cycP-gp120 in a protein prime/boost approach in rabbits and as a booster immunization to DNA/modified vaccinia Ankara (MVA)-vaccinated rabbits and rhesus macaques. In rabbits, two cycP-gp120 protein immunizations induced 100-fold higher titers of high-avidity gp120-specific IgG than two gp120 immunizations, with four total gp120 immunizations being required to induce comparable titers. cycP-gp120 also induced markedly enhanced neutralizing activity against tier-1A and -1B HIV-1 isolates, substantially higher binding and breadth to gp70-V1V2 scaffolds derived from a multiclade panel of global HIV-1 isolates, and antibodies targeting key regions of the V2-loop region associated with reduced risk of infection in RV144. Similarly, boosting MVA- or DNA/MVA-primed rabbits or rhesus macaques with cycP-gp120 showed a robust expansion of gp70-V1V2-specific IgG, neutralization breadth to tier-1B HIV-1 isolates, and antibody-dependent cellular cytotoxicity activity. These results demonstrate that cycP-gp120 serves as a robust HIV Env immunogen that induces broad anti-V1V2 antibodies and promotes neutralization breadth against HIV-1.

IMPORTANCE Recent focus in HIV-1 vaccine development has been the design of trimeric HIV-1 Env immunogens that closely resemble native HIV-1 Env, with a major goal being the induction of bNAbs. While the generation of bNAbs is considered a gold standard in vaccine-induced antibody responses, results from the RV144 trial showed that nonneutralizing antibodies directed toward the V1V2 loop of HIV-1 gp120, specifically the V2 loop region, were associated with decreased risk of infection, demonstrating the need for the development of Env immunogens that induce a broad anti-V1V2 antibody response. In this study, we show that a novel trimeric gp120 protein, cycP-gp120, generates high titers of high-avidity and broadly cross-reactive anti-V1V2 antibodies, a result not found in animals immunized with monomeric gp120. These results reveal the potential of cycP-gp120 as a vaccine candidate to induce antibodies associated with reduced risk of HIV-1 infection in humans.

Intradermal HIV-1 DNA Immunization Using Needle-Free Zetajet Injection Followed by HIV-Modified Vaccinia Virus Ankara Vaccination Is Safe and Immunogenic in Mozambican Young Adults: A Phase I Randomized Controlled Trial

We assessed the safety and immunogenicity of HIV-DNA priming using Zetajet™, a needle-free device intradermally followed by intramuscular HIV-MVA boosts, in 24 healthy Mozambicans. Volunteers were randomized to receive three immunizations of 600 μg (n = 10; 2 × 0.1 ml) or 1,200 μg (n = 10; 2 × 0.2 ml) of HIV-DNA (3 mg/ml), followed by two boosts of 10⁸ pfu HIV-MVA. Four subjects received placebo saline injections. Vaccines and injections were safe and well tolerated with no difference between the two priming groups. After three HIV-DNA immunizations, IFN-γ ELISpot responses to Gag were detected in 9/17 (53%) vaccinees, while none responded to Envelope (Env). After the first HIV-MVA, the overall response rate to Gag and/or Env increased to 14/15 (93%); 14/15 (93%) to Gag and 13/15 (87%) to Env. There were no significant differences between the immunization groups in frequency of response to Gag and Env or magnitude of Gag responses. Env responses were significantly higher in the higher dose group (median 420 vs. 157.5 SFC/million peripheral blood mononuclear cell, p = .014). HIV-specific antibodies to subtype C gp140 and subtype B gp160 were elicited in all vaccinees after the second HIV-MVA, without differences in titers between the groups. Neutralizing antibody responses were not detected. Two (13%) of 16 vaccinees, one in each of the priming groups, exhibited antibodies mediating antibody-dependent cellular cytotoxicity to CRF01_AE. In conclusion, HIV-DNA vaccine delivered intradermally in volumes of 0.1-0.2 ml using Zetajet was safe and well tolerated. Priming with the 1,200 μg dose of HIV-DNA generated higher magnitudes of ELISpot responses to Env.

A Single Dose of Modified Vaccinia Ankara expressing Ebola Virus Like Particles Protects Nonhuman Primates from Lethal Ebola Virus Challenge

Ebola virus (EBOV), isolate Makona, was the causative agent of the West African epidemic devastating predominantly Guinea, Liberia and Sierra Leone from 2013-2016. While several experimental vaccine and treatment approaches have been accelerated through human clinical trials, there is still no approved countermeasure available against this disease. Here, we report the construction and preclinical efficacy testing of a novel recombinant modified vaccinia Ankara (MVA)-based vaccine expressing the EBOV-Makona glycoprotein GP and matrix protein VP40 (MVA-EBOV). GP and VP40 form EBOV-like particles and elicit protective immune responses. In this study, we report 100% protection against lethal EBOV infection in guinea pigs after prime/boost vaccination with MVA-EBOV. Furthermore, this MVA-EBOV protected macaques from lethal disease after a single dose or prime/boost vaccination. The vaccine elicited a variety of antibody responses to both antigens, including neutralizing antibodies and antibodies with antibody-dependent cellular cytotoxic activity specific for GP. This is the first report that a replication-deficient MVA vector can confer full protection against lethal EBOV challenge after a single dose vaccination in macaques.

Vaccination with Combination DNA and Virus-Like Particles Enhances Humoral and Cellular Immune Responses upon Boost with Recombinant Modified Vaccinia Virus Ankara Expressing Human Immunodeficiency Virus Envelope Proteins

Heterologous prime boost with DNA and recombinant modified vaccinia virus Ankara (rMVA) vaccines is considered as a promising vaccination approach against human immunodeficiency virus (HIV-1). To further enhance the efficacy of DNA-rMVA vaccination, we investigated humoral and cellular immune responses in mice after three sequential immunizations with DNA, a combination of DNA and virus-like particles (VLP), and rMVA expressing HIV-1 89.6 gp120 envelope proteins (Env). DNA prime and boost with a combination of VLP and DNA vaccines followed by an rMVA boost induced over a 100-fold increase in Env-specific IgG antibody titers compared to three sequential immunizations with DNA and rMVA. Cellular immune responses were induced by VLP-DNA and rMVA vaccinations at high levels in CD8 T cells, CD4 T cells, and peripheral blood mononuclear cells secreting interferon (IFN)-γ, and spleen cells producing interleukin (IL)-2, 4, 5 cytokines. This study suggests that a DNA and VLP combination vaccine with MVA is a promising strategy in enhancing the efficacy of DNA-rMVA vaccination against HIV-1.

Safety and Immunogenicity of PENNVAX-G DNA Prime Administered by Biojector 2000 or CELLECTRA Electroporation Device With Modified Vaccinia Ankara-CMDR Boost

Background

We report the first-in-human safety and immunogenicity evaluation of PENNVAX-G DNA/modified vaccinia Ankara-Chiang Mai double recombinant (MVA-CMDR) prime-boost human immuonodeficiency virus (HIV) vaccine, with intramuscular DNA delivery by either Biojector 2000 needle-free injection system (Biojector) or CELLECTRA electroporation device.

Methods

Healthy, HIV-uninfected adults were randomized to receive 4 mg of PENNVAX-G DNA delivered intramuscularly by Biojector or electroporation at baseline and week 4 followed by intramuscular injection of 108 plaque forming units of MVA-CMDR at weeks 12 and 24. The open-label part A was conducted in the United States, followed by a double-blind, placebo-controlled part B in East Africa. Solicited and unsolicited adverse events were recorded, and immune responses were measured.

Results

Eighty-eight of 100 enrolled participants completed all study injections, which were generally safe and well tolerated, with more immediate, but transient, pain in the electroporation group. Cellular responses were observed in 57% of vaccine recipients tested and were CD4 predominant. High rates of binding antibody responses to CRF01_AE antigens, including gp70 V1V2 scaffold, were observed. Neutralizing antibodies were detected in a peripheral blood mononuclear cell assay, and moderate antibody-dependent, cell-mediated cytotoxicity activity was demonstrated.

Discussion

The PVG/MVA-CMDR HIV-1 vaccine regimen is safe and immunogenic. Substantial differences in safety or immunogenicity between modes of DNA delivery were not observed.

Clinical Trials Registration

NCT01260727.

HIV-1 gp120 and Modified Vaccinia Virus Ankara (MVA) gp140 Boost Immunogens Increase Immunogenicity of a DNA/MVA HIV-1 Vaccine

An important goal of human immunodeficiency virus (HIV) vaccine design is identification of strategies that elicit effective antiviral humoral immunity. One novel approach comprises priming with DNA and boosting with modified vaccinia virus Ankara (MVA) expressing HIV-1 Env on virus-like particles. In this study, we evaluated whether the addition of a gp120 protein in alum or MVA-expressed secreted gp140 (MVAgp140) could improve immunogenicity of a DNA prime-MVA boost vaccine. Five rhesus macaques per group received two DNA primes at weeks 0 and 8 followed by three MVA boosts (with or without additional protein or MVAgp140) at weeks 18, 26, and 40. Both boost immunogens enhanced the breadth of HIV-1 gp120 and V1V2 responses, antibody-dependent cellular cytotoxicity (ADCC), and low-titer tier 1B and tier 2 neutralizing antibody responses. However, there were differences in antibody kinetics, linear epitope specificity, and CD4 T cell responses between the groups. The gp120 protein boost elicited earlier and higher peak responses, whereas the MVAgp140 boost resulted in improved antibody durability and comparable peak responses after the final immunization. Linear V3 specific IgG responses were particularly enhanced by the gp120 boost, whereas the MVAgp140 boost also enhanced responses to linear C5 and C2.2 epitopes. Interestingly, gp120, but not the MVAgp140 boost, increased peak CD4⁺ T cell responses. Thus, both gp120 and MVAgp140 can augment potential protection of a DNA/MVA vaccine by enhancing gp120 and V1/V2 antibody responses, whereas potential protection by gp120, but not MVAgp140 boosts, may be further impacted by increased CD4⁺ T cell responses.

IMPORTANCE Prior immune correlate analyses with humans and nonhuman primates revealed the importance of antibody responses in preventing HIV-1 infection. A DNA prime-modified vaccinia virus Ankara (MVA) boost vaccine has proven to be potent in eliciting antibody responses. Here we explore the ability of boosts with recombinant gp120 protein or MVA-expressed gp140 to enhance antibody responses elicited by the GOVX-B11 DNA prime-MVA boost vaccine. We found that both types of immunogen boosts enhanced potentially protective antibody responses, whereas the gp120 protein boosts also increased CD4⁺ T cell responses. Our data provide important information for HIV vaccine designs that aim for effective and balanced humoral and T cell responses.

A Zika Vaccine Targeting NS1 Protein Protects Immunocompetent Adult Mice in a Lethal Challenge Model

Zika virus (ZIKV) is a mosquito-borne flavivirus that has rapidly extended its geographic range around the world. Its association with abnormal fetal brain development, sexual transmission, and lack of a preventive vaccine have constituted a global health concern. Designing a safe and effective vaccine requires significant caution due to overlapping geographical distribution of ZIKV with dengue virus (DENV) and other flaviviruses, possibly resulting in more severe disease manifestations in flavivirus immune vaccinees such as Antibody-Dependent Enhancement (ADE, a phenomenon involved in pathogenesis of DENV, and a risk associated with ZIKV vaccines using the envelope proteins as immunogens). Here, we describe the development of an alternative vaccine strategy encompassing the expression of ZIKV non-structural-1 (NS1) protein from a clinically proven safe, Modified Vaccinia Ankara (MVA) vector, thus averting the potential risk of ADE associated with structural protein-based ZIKV vaccines. A single intramuscular immunization of immunocompetent mice with the MVA-ZIKV-NS1 vaccine candidate provided robust humoral and cellular responses, and afforded 100% protection against a lethal intracerebral dose of ZIKV (strain MR766). This is the first report of (i) a ZIKV vaccine based on the NS1 protein and (ii) single dose protection against ZIKV using an immunocompetent lethal mouse challenge model.

DNA Priming Increases Frequency of T-Cell Responses to a Vesicular Stomatitis Virus HIV Vaccine with Specific Enhancement of CD8+ T-Cell Responses by Interleukin-12 Plasmid DNA

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 × 10⁷ 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.).

Safety and vaccine-induced HIV-1 immune responses in healthy volunteers following a late MVA-B boost 4 years after the last immunization

Background

We have previously shown that an HIV vaccine regimen including three doses of HIV-modified vaccinia virus Ankara vector expressing HIV-1 antigens from clade B (MVA-B) was safe and elicited moderate and durable (1 year) T-cell and antibody responses in 75% and 95% of HIV-negative volunteers (n = 24), respectively (RISVAC02 study). Here, we describe the long-term durability of vaccine-induced responses and the safety and immunogenicity of an additional MVA-B boost.

Methods

13 volunteers from the RISVAC02 trial were recruited to receive a fourth dose of MVA-B 4 years after the last immunization. End-points were safety, cellular and humoral immune responses to HIV-1 and vector antigens assessed by ELISPOT, intracellular cytokine staining (ICS) and ELISA performed before and 2, 4 and 12 weeks after receiving the boost.

Results

Volunteers reported 64 adverse events (AEs), although none was a vaccine-related serious AE. After 4 years from the 1^st dose of the vaccine, only 2 volunteers maintained low HIV-specific T-cell responses. After the late MVA-B boost, a modest increase in IFN-γ T-cell responses, mainly directed against Env, was detected by ELISPOT in 5/13 (38%) volunteers. ICS confirmed similar results with 45% of volunteers showing that CD4+ T-cell responses were mainly directed against Env, whereas CD8+ T cell-responses were similarly distributed against Env, Gag and GPN. In terms of antibody responses, 23.1% of the vaccinees had detectable Env-specific binding antibodies 4 years after the last MVA-B immunization with a mean titer of 96.5. The late MVA-B boost significantly improved both the response rate (92.3%) and the magnitude of the systemic binding antibodies to gp120 (mean titer of 11460). HIV-1 neutralizing antibodies were also enhanced and detected in 77% of volunteers. Moreover, MVA vector-specific T cell and antibody responses were boosted in 80% and 100% of volunteers respectively.

Conclusions

One boost of MVA-B four years after receiving 3 doses of the same vaccine was safe, induced moderate increases in HIV-specific T cell responses in 38% of volunteers but significantly boosted the binding and neutralizing antibody responses to HIV-1 and to the MVA vector.

Trial registration

ClinicalTrials.gov NCT01923610.

Immunogenicity and efficacy of DNA/MVA HIV vaccines in rhesus macaque models

INTRODUCTION

Despite 30 years of research on HIV, a vaccine to prevent infection and limit disease progression remains elusive. The RV144 trial showed moderate, but significant protection in humans and highlighted the contribution of antibody responses directed against HIV envelope as an important immune correlate for protection. Efforts to further build upon the progress include the use of a heterologous prime-boost regimen using DNA as the priming agent and the attenuated vaccinia virus, Modified Vaccinia Ankara (MVA), as a boosting vector for generating protective HIV-specific immunity. Areas covered: In this review, we summarize the immunogenicity of DNA/MVA vaccines in non-human primate models and describe the efficacy seen in SIV infection models. We discuss immunological correlates of protection determined by these studies and potential approaches for improving the protective immunity. Additionally, we describe the current progress of DNA/MVA vaccines in human trials. Expert commentary: Efforts over the past decade have provided the opportunity to better understand the dynamics of vaccine-induced immune responses and immune correlates of protection against HIV. Based on what we have learned, we outline multiple areas where the field will likely focus on in the next five years.

Human Ig knockin mice to study the development and regulation of HIV-1 broadly neutralizing antibodies

A major challenge for HIV-1 vaccine research is developing a successful immunization approach for inducing broadly neutralizing antibodies (bnAbs). A key shortcoming in meeting this challenge has been the lack of animal models capable of identifying impediments limiting bnAb induction and ranking vaccine strategies for their ability to promote bnAb development. Since 2010, immunoglobulin knockin (KI) technology, involving inserting functional rearranged human variable exons into the mouse IgH and IgL loci has been used to express bnAbs in mice. This approach has allowed immune tolerance mechanisms limiting bnAb production to be elucidated and strategies to overcome such limitations to be evaluated. From these studies, along with the wealth of knowledge afforded by analyses of recombinant Ig-based bnAb structures, it became apparent that key functional features of bnAbs often are problematic for their elicitation in mice by classic vaccine paradigms, necessitating more iterative testing of new vaccine concepts. In this regard, bnAb KI models expressing deduced precursor V(D)J rearrangements of mature bnAbs or unrearranged germline V, D, J segments (that can be assembled into variable region exons that encode bnAb precursors), have been engineered to evaluate novel immunogens/regimens for effectiveness in driving bnAb responses. One promising approach emerging from such studies is the ability of sequentially administered, modified immunogens (designed to bind progressively more mature bnAb precursors) to initiate affinity maturation. Here, we review insights gained from bnAb KI studies regarding the regulation and induction of bnAbs, and discuss new Ig KI methodologies to manipulate the production and/or expression of bnAbs in vivo, to further facilitate vaccine-guided bnAb induction studies.