Heterologous cAd3-Ebola and MVA-EbolaZ vaccines are safe and immunogenic in US and Uganda phase 1/1b trials.

Ebola virus disease (EVD) is a filoviral infection caused by virus species of the Ebolavirus genus including Zaire ebolavirus (EBOV) and Sudan ebolavirus (SUDV). We investigated the safety and immunogenicity of a heterologous prime-boost regimen involving a chimpanzee adenovirus 3 vectored Ebola vaccine [either monovalent (cAd3-EBOZ) or bivalent (cAd3-EBO)] prime followed by a recombinant modified vaccinia virus Ankara EBOV vaccine (MVA-EbolaZ) boost in two phase 1/1b randomized open-label clinical trials in healthy adults in the United States (US) and Uganda (UG). Trial US (NCT02408913) enrolled 140 participants, including 26 EVD vaccine-naïve and 114 cAd3-Ebola-experienced participants (April-November 2015). Trial UG (NCT02354404) enrolled 90 participants, including 60 EVD vaccine-naïve and 30 DNA Ebola vaccine-experienced participants (February-April 2015). All tested vaccines and regimens were safe and well tolerated with no serious adverse events reported related to study products. Solicited local and systemic reactogenicity was mostly mild to moderate in severity. The heterologous prime-boost regimen was immunogenic, including induction of durable antibody responses which peaked as early as two weeks and persisted up to one year after each vaccination. Different prime-boost intervals impacted the magnitude of humoral and cellular immune responses. The results from these studies demonstrate promising implications for use of these vaccines in both prophylactic and outbreak settings.

HIV-1 neutralizing antibodies elicited in humans by a prefusion-stabilized envelope trimer form a reproducible class targeting fusion peptide.

Elicitation of antibodies that neutralize the tier-2 neutralization-resistant isolates that typify HIV-1 transmission has been a long-sought goal. Success with prefusion-stabilized envelope trimers eliciting autologous neutralizing antibodies has been reported in multiple vaccine-test species, though not in humans. To investigate elicitation of HIV-1 neutralizing antibodies in humans, here, we analyze B cells from a phase I clinical trial of the "DS-SOSIP"-stabilized envelope trimer from strain BG505, identifying two antibodies, N751-2C06.01 and N751-2C09.01 (named for donor-lineage.clone), that neutralize the autologous tier-2 strain, BG505. Though derived from distinct lineages, these antibodies form a reproducible antibody class that targets the HIV-1 fusion peptide. Both antibodies are highly strain specific, which we attribute to their partial recognition of a BG505-specific glycan hole and to their binding requirements for a few BG505-specific residues. Prefusion-stabilized envelope trimers can thus elicit autologous tier-2 neutralizing antibodies in humans, with initially identified neutralizing antibodies recognizing the fusion-peptide site of vulnerability.

Primary exposure to SARS-CoV-2 variants elicits convergent epitope specificities, immunoglobulin V gene usage and public B cell clones.

An important consequence of infection with a SARS-CoV-2 variant is protective humoral immunity against other variants. However, the basis for such cross-protection at the molecular level is incompletely understood. Here, we characterized the repertoire and epitope specificity of antibodies elicited by infection with the Beta, Gamma and WA1 ancestral variants and assessed their cross-reactivity to these and the more recent Delta and Omicron variants. We developed a method to obtain immunoglobulin sequences with concurrent rapid production and functional assessment of monoclonal antibodies from hundreds of single B cells sorted by flow cytometry. Infection with any variant elicited similar cross-binding antibody responses exhibiting a conserved hierarchy of epitope immunodominance. Furthermore, convergent V gene usage and similar public B cell clones were elicited regardless of infecting variant. These convergent responses despite antigenic variation may account for the continued efficacy of vaccines based on a single ancestral variant.

Clinical outcomes and immune responses to SARS-CoV-2 vaccination in severe aplastic anaemia.

Patients with severe aplastic anaemia (SAA) are often not vaccinated against viruses due to concerns of ineffective protective antibody response and potential for pathogenic global immune system activation, leading to relapse. We evaluated the impact of COVID-19 vaccination on haematological indices and disease status and characterized the humoural and cellular responses to vaccination in 50 SAA patients, who were previously treated with immunosuppressive therapy (IST). There was no significant difference in haemoglobin (p = 0.52), platelet count (p = 0.67), absolute lymphocyte (p = 0.42) and neutrophil (p = 0.98) counts prior to and after completion of vaccination series. Relapse after vaccination, defined as a progressive decline in counts requiring treatment, occurred in three patients (6%). Humoural response was detectable in 90% (28/31) of cases by reduction in an in-vitro Angiotensin II Converting Enzyme (ACE2) binding and neutralization assay, even in patients receiving ciclosporin (10/11, 90.1%). Comparison of spike-specific T-cell responses in 27 SAA patients and 10 control subjects revealed qualitatively similar CD4+ Th1-dominant responses to vaccination. There was no difference in CD4+ (p = 0.77) or CD8+ (p = 0.74) T-cell responses between patients on or off ciclosporin therapy at the time of vaccination. Our data highlight appropriate humoural and cellular responses in SAA previously treated with IST and true relapse after vaccination is rare.

Safety and immunogenicity of an HIV-1 prefusion-stabilized envelope trimer (Trimer 4571) vaccine in healthy adults: A first-in-human open-label, randomized, dose-escalation, phase 1 clinical trial.

Background: Advances in therapeutic drugs have increased life-expectancies for HIV-infected individuals, but the need for an effective vaccine remains. We assessed safety and immunogenicity of HIV-1 vaccine, Trimer 4571 (BG505 DS-SOSIP.664) adjuvanted with aluminum hydroxide (alum), in HIV-negative adults. Methods: We conducted a phase I, randomized, open-label, dose-escalation trial at the National Institutes of Health Clinical Center in Bethesda, MD, USA. Eligible participants were HIV-negative, healthy adults between 18-50 years. Participants were randomized 1:1 to receive Trimer 4571 adjuvanted with 500 mcg alum by either the subcutaneous (SC) or intramuscular (IM) route at weeks 0, 8, and 20 in escalating doses of 100 mcg or 500 mcg. The primary objectives were to evaluate the safety and tolerability of Trimer 4571 with a secondary objective of evaluating vaccine-induced antibody responses. The primary and safety endpoints were evaluated in all participants who received at least one dose of Trimer 4571. Trial results were summarized using descriptive statistics. This trial is registered at ClinicalTrials.gov, NCT03783130. Findings: Between March 7 and September 11, 2019, 16 HIV-negative participants were enrolled, including six (38%) males and ten (62%) females. All participants received three doses of Trimer 4571. Solicited reactogenicity was mild to moderate in severity, with one isolated instance of severe injection site redness (6%) following a third 500 mcg SC administration. The most commonly reported solicited symptoms included mild injection site tenderness in 14 (88%) and mild myalgia in six (38%) participants. The most frequent unsolicited adverse event attributed to vaccination was mild injection site pruritus in six (38%) participants. Vaccine-induced seropositivity occurred in seven (44%) participants and resolved in all but one (6%). No serious adverse events occurred. Trimer 4571-specific binding antibodies were detected in all groups two weeks after regimen completion, primarily focused on the glycan-free trimer base. Neutralizing antibody activity was limited to the 500 mcg dose groups. Interpretation: Trimer 4571 was safe, well tolerated, and immunogenic in this first-in-human trial. While this phase 1 trial is limited in size, our results inform and support further evaluation of prefusion-stabilized HIV-1 envelope trimers as a component of vaccine design strategies to generate broadly neutralizing antibodies against HIV-1. Funding: Intramural Research Program of the Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health.

Safety and tolerability of AAV8 delivery of a broadly neutralizing antibody in adults living with HIV: a phase 1, dose-escalation trial.

Adeno-associated viral vector-mediated transfer of DNA coding for broadly neutralizing anti-HIV antibodies (bnAbs) offers an alternative to attempting to induce protection by vaccination or by repeated infusions of bnAbs. In this study, we administered a recombinant bicistronic adeno-associated virus (AAV8) vector coding for both the light and heavy chains of the potent broadly neutralizing HIV-1 antibody VRC07 (AAV8-VRC07) to eight adults living with HIV. All participants remained on effective anti-retroviral therapy (viral load (VL) <50 copies per milliliter) throughout this phase 1, dose-escalation clinical trial ( NCT03374202 ). AAV8-VRC07 was given at doses of 5 × 1010, 5 × 1011 and 2.5 × 1012 vector genomes per kilogram by intramuscular (IM) injection. Primary endpoints of this study were to assess the safety and tolerability of AAV8-VRC07; to determine the pharmacokinetics and immunogenicity of in vivo VRC07 production; and to describe the immune response directed against AAV8-VRC07 vector and its products. Secondary endpoints were to assess the clinical effects of AAV8-VRC07 on CD4 T cell count and VL and to assess the persistence of VRC07 produced in participants. In this cohort, IM injection of AAV8-VRC07 was safe and well tolerated. No clinically significant change in CD4 T cell count or VL occurred during the 1-3 years of follow-up reported here. In participants who received AAV8-VRC07, concentrations of VRC07 were increased 6 weeks (P = 0.008) and 52 weeks (P = 0.016) after IM injection of the product. All eight individuals produced measurable amounts of serum VRC07, with maximal VRC07 concentrations >1 µg ml-1 in three individuals. In four individuals, VRC07 serum concentrations remained stable near maximal concentration for up to 3 years of follow-up. In exploratory analyses, neutralizing activity of in vivo produced VRC07 was similar to that of in vitro produced VRC07. Three of eight participants showed a non-idiotypic anti-drug antibody (ADA) response directed against the Fab portion of VRC07. This ADA response appeared to decrease the production of serum VRC07 in two of these three participants. These data represent a proof of concept that adeno-associated viral vectors can durably produce biologically active, difficult-to-induce bnAbs in vivo, which could add valuable new tools to the fight against infectious diseases.

Primary exposure to SARS-CoV-2 variants elicits convergent epitope specificities, immunoglobulin V gene usage and public B cell clones.

An important consequence of infection with a SARS-CoV-2 variant is protective humoral immunity against other variants. The basis for such cross-protection at the molecular level is incompletely understood. Here we characterized the repertoire and epitope specificity of antibodies elicited by Beta, Gamma and ancestral variant infection and assessed their cross-reactivity to these and the more recent Delta and Omicron variants. We developed a high-throughput approach to obtain immunoglobulin sequences and produce monoclonal antibodies for functional assessment from single B cells. Infection with any variant elicited similar cross-binding antibody responses exhibiting a remarkably conserved hierarchy of epitope immunodominance. Furthermore, convergent V gene usage and similar public B cell clones were elicited regardless of infecting variant. These convergent responses despite antigenic variation may represent a general immunological principle that accounts for the continued efficacy of vaccines based on a single ancestral variant.

Ultrapotent antibodies against diverse and highly transmissible SARS-CoV-2 variants.

The emergence of highly transmissible SARS-CoV-2 variants of concern (VOCs) that are resistant to therapeutic antibodies highlights the need for continuing discovery of broadly reactive antibodies. We identified four receptor binding domain-targeting antibodies from three early-outbreak convalescent donors with potent neutralizing activity against 23 variants, including the B.1.1.7, B.1.351, P.1, B.1.429, B.1.526, and B.1.617 VOCs. Two antibodies are ultrapotent, with subnanomolar neutralization titers [half-maximal inhibitory concentration (IC50) 0.3 to 11.1 nanograms per milliliter; IC80 1.5 to 34.5 nanograms per milliliter). We define the structural and functional determinants of binding for all four VOC-targeting antibodies and show that combinations of two antibodies decrease the in vitro generation of escape mutants, suggesting their potential in mitigating resistance development.

Antibodies with potent and broad neutralizing activity against antigenically diverse and highly transmissible SARS-CoV-2 variants.

The emergence of highly transmissible SARS-CoV-2 variants of concern (VOC) that are resistant to therapeutic antibodies highlights the need for continuing discovery of broadly reactive antibodies. We identify four receptor-binding domain targeting antibodies from three early-outbreak convalescent donors with potent neutralizing activity against 12 variants including the B.1.1.7 and B.1.351 VOCs. Two of them are ultrapotent, with sub-nanomolar neutralization titers (IC50 <0.0006 to 0.0102 µ g/mL; IC80 < 0.0006 to 0.0251 µ g/mL). We define the structural and functional determinants of binding for all four VOC-targeting antibodies, and show that combinations of two antibodies decrease the in vitro generation of escape mutants, suggesting potential means to mitigate resistance development. These results define the basis of therapeutic cocktails against VOCs and suggest that targeted boosting of existing immunity may increase vaccine breadth against VOCs.

Safety, tolerability, pharmacokinetics, and immunogenicity of the therapeutic monoclonal antibody mAb114 targeting Ebola virus glycoprotein (VRC 608): an open-label phase 1 study.

BACKGROUND: mAb114 is a single monoclonal antibody that targets the receptor-binding domain of Ebola virus glycoprotein, which prevents mortality in rhesus macaques treated after lethal challenge with Zaire ebolavirus. Here we present expedited data from VRC 608, a phase 1 study to evaluate mAb114 safety, tolerability, pharmacokinetics, and immunogenicity. METHODS: In this phase 1, dose-escalation study (VRC 608), conducted at the US National Institutes of Health (NIH) Clinical Center (Bethesda, MD, USA), healthy adults aged 18-60 years were sequentially enrolled into three mAb114 dose groups of 5 mg/kg, 25 mg/kg, and 50 mg/kg. The drug was given to participants intravenously over 30 min, and participants were followed for 24 weeks. Participants were only enrolled into increased dosing groups after interim safety assessments. Our primary endpoints were safety and tolerability, with pharmacokinetic and anti-drug antibody assessments as secondary endpoints. We assessed safety and tolerability in all participants who received study drug by monitoring clinical laboratory data and self-report and direct clinician assessment of prespecified infusion-site symptoms 3 days after infusion and systemic symptoms 7 days after infusion. Unsolicited adverse events were recorded for 28 days. Pharmacokinetic and anti-drug antibody assessments were completed in participants with at least 56 days of data. This trial is registered with ClinicalTrials.gov, number NCT03478891, and is active but no longer recruiting. FINDINGS: Between May 16, and Sept 27, 2018, 19 eligible individuals were enrolled. One (5%) participant was not infused because intravenous access was not adequate. Of 18 (95%) remaining participants, three (17%) were assigned to the 5 mg/kg group, five (28%) to the 25 mg/kg group, and ten (55%) to the 50 mg/kg group, each of whom received a single infusion of mAb114 at their assigned dose. All infusions were well tolerated and completed over 30-37 min with no infusion reactions or rate adjustments. All participants who received the study drug completed the safety assessment of local and systemic reactogenicity. No participants reported infusion-site symptoms. Systemic symptoms were all mild and present only in four (22%) of 18 participants across all dosing groups. No unsolicited adverse events occurred related to mAb114 and one serious adverse event occurred that was unrelated to mAb114. mAb114 has linear pharmacokinetics and a half-life of 24·2 days (standard error of measurement 0·2) with no evidence of anti-drug antibody development. INTERPRETATION: mAb114 was well tolerated, showed linear pharmacokinetics, and was easily and rapidly infused, making it an attractive and deployable option for treatment in outbreak settings. FUNDING: Vaccine Research Center, US National Institute of Allergy and Infectious Diseases, and NIH.

Safety, tolerability, and immunogenicity of two Zika virus DNA vaccine candidates in healthy adults: randomised, open-label, phase 1 clinical trials.

BACKGROUND: The Zika virus epidemic and associated congenital infections have prompted rapid vaccine development. We assessed two new DNA vaccines expressing premembrane and envelope Zika virus structural proteins. METHODS: We did two phase 1, randomised, open-label trials involving healthy adult volunteers. The VRC 319 trial, done in three centres, assessed plasmid VRC5288 (Zika virus and Japanese encephalitis virus chimera), and the VRC 320, done in one centre, assessed plasmid VRC5283 (wild-type Zika virus). Eligible participants were aged 18-35 years in VRC19 and 18-50 years in VRC 320. Participants were randomly assigned 1:1 by a computer-generated randomisation schedule prepared by the study statistician. All participants received intramuscular injection of 4 mg vaccine. In VRC 319 participants were assigned to receive vaccinations via needle and syringe at 0 and 8 weeks, 0 and 12 weeks, 0, 4, and 8 weeks, or 0, 4, and 20 weeks. In VRC 320 participants were assigned to receive vaccinations at 0, 4, and 8 weeks via single-dose needle and syringe injection in one deltoid or split-dose needle and syringe or needle-free injection with the Stratis device (Pharmajet, Golden, CO, USA) in each deltoid. Both trials followed up volunteers for 24 months for the primary endpoint of safety, assessed as local and systemic reactogenicity in the 7 days after each vaccination and all adverse events in the 28 days after each vaccination. The secondary endpoint in both trials was immunogenicity 4 weeks after last vaccination. These trials are registered with ClinicalTrials.gov, numbers NCT02840487 and NCT02996461. FINDINGS: VRC 319 enrolled 80 participants (20 in each group), and VRC 320 enrolled 45 participants (15 in each group). One participant in VRC 319 and two in VRC 320 withdrew after one dose of vaccine, but were included in the safety analyses. Both vaccines were safe and well tolerated. All local and systemic symptoms were mild to moderate. In both studies, pain and tenderness at the injection site was the most frequent local symptoms (37 [46%] of 80 participants in VRC 319 and 36 [80%] of 45 in VRC 320) and malaise and headache were the most frequent systemic symptoms (22 [27%] and 18 [22%], respectively, in VRC 319 and 17 [38%] and 15 [33%], respectively, in VRC 320). For VRC5283, 14 of 14 (100%) participants who received split-dose vaccinations by needle-free injection had detectable positive antibody responses, and the geometric mean titre of 304 was the highest across all groups in both trials. INTERPRETATION: VRC5283 was well tolerated and has advanced to phase 2 efficacy testing. FUNDING: Intramural Research Program of the Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health.

Attenuated PfSPZ Vaccine induces strain-transcending T cells and durable protection against heterologous controlled human malaria infection.

A live-attenuated malaria vaccine, Plasmodium falciparum sporozoite vaccine (PfSPZ Vaccine), confers sterile protection against controlled human malaria infection (CHMI) with Plasmodium falciparum (Pf) parasites homologous to the vaccine strain up to 14 mo after final vaccination. No injectable malaria vaccine has demonstrated long-term protection against CHMI using Pf parasites heterologous to the vaccine strain. Here, we conducted an open-label trial with PfSPZ Vaccine at a dose of 9.0 × 105 PfSPZ administered i.v. three times at 8-wk intervals to 15 malaria-naive adults. After CHMI with homologous Pf parasites 19 wk after final immunization, nine (64%) of 14 (95% CI, 35-87%) vaccinated volunteers remained without parasitemia compared with none of six nonvaccinated controls (P = 0.012). Of the nine nonparasitemic subjects, six underwent repeat CHMI with heterologous Pf7G8 parasites 33 wk after final immunization. Five (83%) of six (95% CI, 36-99%) remained without parasitemia compared with none of six nonvaccinated controls. PfSPZ-specific T-cell and antibody responses were detected in all vaccine recipients. Cytokine production by T cells from vaccinated subjects after in vitro stimulation with homologous (NF54) or heterologous (7G8) PfSPZ were highly correlated. Interestingly, PfSPZ-specific T-cell responses in the blood peaked after the first immunization and were not enhanced by subsequent immunizations. Collectively, these data suggest durable protection against homologous and heterologous Pf parasites can be achieved with PfSPZ Vaccine. Ongoing studies will determine whether protective efficacy can be enhanced by additional alterations in the vaccine dose and number of immunizations.

Chimpanzee Adenovirus Vector Ebola Vaccine.

BACKGROUND: The unprecedented 2014 epidemic of Ebola virus disease (EVD) prompted an international response to accelerate the availability of a preventive vaccine. A replication-defective recombinant chimpanzee adenovirus type 3-vectored ebolavirus vaccine (cAd3-EBO), encoding the glycoprotein from Zaire and Sudan species, that offers protection in the nonhuman primate model, was rapidly advanced into phase 1 clinical evaluation. METHODS: We conducted a phase 1, dose-escalation, open-label trial of cAd3-EBO. Twenty healthy adults, in sequentially enrolled groups of 10 each, received vaccination intramuscularly in doses of 2×1010 particle units or 2×1011 particle units. Primary and secondary end points related to safety and immunogenicity were assessed throughout the first 8 weeks after vaccination; in addition, longer-term vaccine durability was assessed at 48 weeks after vaccination. RESULTS: In this small study, no safety concerns were identified; however, transient fever developed within 1 day after vaccination in two participants who had received the 2×1011 particle-unit dose. Glycoprotein-specific antibodies were induced in all 20 participants; the titers were of greater magnitude in the group that received the 2×1011 particle-unit dose than in the group that received the 2×1010 particle-unit dose (geometric mean titer against the Zaire antigen at week 4, 2037 vs. 331; P=0.001). Glycoprotein-specific T-cell responses were more frequent among those who received the 2×1011 particle-unit dose than among those who received the 2×1010 particle-unit dose, with a CD4 response in 10 of 10 participants versus 3 of 10 participants (P=0.004) and a CD8 response in 7 of 10 participants versus 2 of 10 participants (P=0.07) at week 4. Assessment of the durability of the antibody response showed that titers remained high at week 48, with the highest titers in those who received the 2×1011 particle-unit dose. CONCLUSIONS: Reactogenicity and immune responses to cAd3-EBO vaccine were dose-dependent. At the 2×1011 particle-unit dose, glycoprotein Zaire-specific antibody responses were in the range reported to be associated with vaccine-induced protective immunity in challenge studies involving nonhuman primates, and responses were sustained to week 48. Phase 2 studies and efficacy trials assessing cAd3-EBO are in progress. (Funded by the Intramural Research Program of the National Institutes of Health; VRC 207 ClinicalTrials.gov number, NCT02231866 .).

Safety and Immunogenicity of a rAd35-EnvA Prototype HIV-1 Vaccine in Combination with rAd5-EnvA in Healthy Adults (VRC 012).

BACKGROUND: VRC 012 was a Phase I study of a prototype recombinant adenoviral-vector serotype-35 (rAd35) HIV vaccine, the precursor to two recently published clinical trials, HVTN 077 and 083. On the basis of prior evaluation of multiclade rAd5 HIV vaccines, Envelope A (EnvA) was selected as the standard antigen for a series of prototype HIV vaccines to compare various vaccine platforms. In addition, prior studies of rAd5-vectored vaccines suggested pre-existing human immunity may be a confounding factor in vaccine efficacy. rAd35 is less seroprevalent across human populations and was chosen for testing alone and in combination with a rAd5-EnvA vaccine in the present two-part phase I study. METHODS: First, five subjects each received a single injection of 109, 1010, or 1011 particle units (PU) of rAd35-EnvA in an open-label, dose-escalation study. Next, 20 Ad5/Ad35-seronegative subjects were randomized to blinded, heterologous prime-boost schedules combining rAd5-EnvA and rAd35-EnvA with a three month interval. rAd35-EnvA was given at 1010 or 1011 PU to ten subjects each; all rAd5-EnvA injections were 1010 PU. EnvA-specific immunogenicity was assessed four weeks post-injection. Solicited reactogenicity and clinical safety were followed after each injection. RESULTS: Vaccinations were well tolerated at all dosages. Antibody responses measured by ELISA were detected at 4 weeks in 30% and 50% of subjects after single doses of 1010 or 1011 PU rAd35, respectively, and in 89% after a single rAd5-EnvA 1010 PU injection. EnvA-specific IFN-γ ELISpot responses were detected at four weeks in 0%, 70%, and 50% of subjects after the respective rAd35-EnvA dosages compared to 89% of subjects after rAd5. T cell responses were higher after a single rAd5-EnvA 1010 PU injection than after a single rAd35-EnvA 1010 PU injection, and humoral responses were low after a single dose of either vector. Of those completing the vaccine schedule, 100% of rAd5-EnvA recipients and 90% of rAd35-EnvA recipients had both T cell and humoral responses after boosting with the heterologous vector. ELISpot response magnitude was similar in both regimens and comparable to a single dose of rAd5. A trend toward more robust CD8 T cell responses using rAd5-EnvA prime and rAd35-EnvA boost was observed. Humoral response magnitude was also similar after either heterologous regimen, but was several fold higher than after a single dose of rAd5. Adverse events (AEs) related to study vaccines were in general mild and limited to one episode of hematuria, Grade two. Activated partial thromboplastin time (aPTT) AEs were consistent with an in vitro effect on the laboratory assay for aPTT due to a transient induction of anti-phospholipid antibody, a phenomenon that has been reported in other adenoviral vector vaccine trials. CONCLUSIONS: Limitations of the rAd vaccine vectors, including the complex interactions among pre-existing adenoviral immunity and vaccine-induced immune responses, have prompted investigators to include less seroprevalent vectors such as rAd35-EnvA in prime-boost regimens. The rAd35-EnvA vaccine described here was well tolerated and immunogenic. While it effectively primed and boosted antibody responses when given in a reciprocal prime-boost regimen with rAd5-EnvA using a three-month interval, it did not significantly improve the frequency or magnitude of T cell responses above a single dose of rAd5. The humoral and cellular immunogenicity data reported here may inform future vaccine and study design. TRIAL REGISTRATION: ClinicalTrials.gov NCT00479999.

Protection against malaria at 1 year and immune correlates following PfSPZ vaccination.

An attenuated Plasmodium falciparum (Pf) sporozoite (SPZ) vaccine, PfSPZ Vaccine, is highly protective against controlled human malaria infection (CHMI) 3 weeks after immunization, but the durability of protection is unknown. We assessed how vaccine dosage, regimen, and route of administration affected durable protection in malaria-naive adults. After four intravenous immunizations with 2.7 × 10(5) PfSPZ, 6/11 (55%) vaccinated subjects remained without parasitemia following CHMI 21 weeks after immunization. Five non-parasitemic subjects from this dosage group underwent repeat CHMI at 59 weeks, and none developed parasitemia. Although Pf-specific serum antibody levels correlated with protection up to 21-25 weeks after immunization, antibody levels waned substantially by 59 weeks. Pf-specific T cell responses also declined in blood by 59 weeks. To determine whether T cell responses in blood reflected responses in liver, we vaccinated nonhuman primates with PfSPZ Vaccine. Pf-specific interferon-γ-producing CD8 T cells were present at ∼100-fold higher frequencies in liver than in blood. Our findings suggest that PfSPZ Vaccine conferred durable protection to malaria through long-lived tissue-resident T cells and that administration of higher doses may further enhance protection.

Homologous boosting with adenoviral serotype 5 HIV vaccine (rAd5) vector can boost antibody responses despite preexisting vector-specific immunity in a randomized phase I clinical trial.

BACKGROUND: Needle-free delivery improves the immunogenicity of DNA vaccines but is also associated with more local reactogenicity. Here we report the first comparison of Biojector and needle administration of a candidate rAd5 HIV vaccine. METHODS: Thirty-one adults, 18-55 years, 20 naive and 11 prior rAd5 vaccine recipients were randomized to receive single rAd5 vaccine via needle or Biojector IM injection at 1010 PU in a Phase I open label clinical trial. Solicited reactogenicity was collected for 5 days; clinical safety and immunogenicity follow-up was continued for 24 weeks. RESULTS: Overall, injections by either method were well tolerated. There were no serious adverse events. Frequency of any local reactogenicity was 16/16 (100%) for Biojector compared to 11/15 (73%) for needle injections. There was no difference in HIV Env-specific antibody response between Biojector and needle delivery. Env-specific antibody responses were more than 10-fold higher in subjects receiving a booster dose of rAd5 vaccine than after a single dose delivered by either method regardless of interval between prime and boost. CONCLUSIONS: Biojector delivery did not improve antibody responses to the rAd5 vaccine compared to needle administration. Homologous boosting with rAd5 gene-based vectors can boost insert-specific antibody responses despite pre-existing vector-specific immunity. TRIAL REGISTRATION: Clinicaltrials.gov NCT00709605 NCT00709605.

Phase I randomized clinical trial of VRC DNA and rAd5 HIV-1 vaccine delivery by intramuscular (i.m.), subcutaneous (s.c.) and intradermal (i.d.) administration (VRC 011).

BACKGROUND: Phase 1 evaluation of the VRC HIV DNA and rAd5 vaccines delivered intramuscularly (i.m.) supported proceeding to a Phase 2 b efficacy study. Here we report comparison of the i.m., subcutaneous (s.c.) and intradermal (i.d.) routes of administration. METHODS: Sixty subjects were randomized to 6 schedules to evaluate the i.m., s.c. or i.d. route for prime injections. Three schedules included DNA primes (Wks 0,4,8) and 3 schedules included rAd5 prime (Wk0); all included rAd5 i.m. boost (Wk24). DNA vaccine dosage was 4 mg i.m. or s.c., but 0.4 mg i.d., while all rAd5 vaccinations were 1010 PU. All injections were administered by needle and syringe. RESULTS: Overall, 27/30 subjects completed 3 DNA primes; 30/30 subjects completed rAd5 primes. Mild local pruritus (itchiness), superficial skin lesions and injection site nodules were associated with i.d. and s.c., but not i.m. injections. All routes induced T-cell and antibody immune responses after rAd5 boosting. Overall, >95% had Env antibody and >80% had Env T-cell responses. CONCLUSIONS: The pattern of local reactogenicity following i.d. and s.c. injections differed from i.m. injections but all routes were well-tolerated. There was no evidence of an immunogenicity advantage following s.c. or i.d. delivery, supporting i.m. delivery as the preferred route of administration. TRIAL REGISTRATION: Clinicaltrials.gov NCT00321061.

Protection against malaria by intravenous immunization with a nonreplicating sporozoite vaccine.

Consistent, high-level, vaccine-induced protection against human malaria has only been achieved by inoculation of Plasmodium falciparum (Pf) sporozoites (SPZ) by mosquito bites. We report that the PfSPZ Vaccine--composed of attenuated, aseptic, purified, cryopreserved PfSPZ--was safe and well tolerated when administered four to six times intravenously (IV) to 40 adults. Zero of six subjects receiving five doses and three of nine subjects receiving four doses of 1.35 × 10(5) PfSPZ Vaccine and five of six nonvaccinated controls developed malaria after controlled human malaria infection (P = 0.015 in the five-dose group and P = 0.028 for overall, both versus controls). PfSPZ-specific antibody and T cell responses were dose-dependent. These data indicate that there is a dose-dependent immunological threshold for establishing high-level protection against malaria that can be achieved with IV administration of a vaccine that is safe and meets regulatory standards.

Priming immunization with DNA augments immunogenicity of recombinant adenoviral vectors for both HIV-1 specific antibody and T-cell responses.

BACKGROUND: Induction of HIV-1-specific T-cell responses relevant to diverse subtypes is a major goal of HIV vaccine development. Prime-boost regimens using heterologous gene-based vaccine vectors have induced potent, polyfunctional T cell responses in preclinical studies. METHODS: The first opportunity to evaluate the immunogenicity of DNA priming followed by recombinant adenovirus serotype 5 (rAd5) boosting was as open-label rollover trials in subjects who had been enrolled in prior studies of HIV-1 specific DNA vaccines. All subjects underwent apheresis before and after rAd5 boosting to characterize in depth the T cell and antibody response induced by the heterologous DNA/rAd5 prime-boost combination. RESULTS: rAd5 boosting was well-tolerated with no serious adverse events. Compared to DNA or rAd5 vaccine alone, sequential DNA/rAd5 administration induced 7-fold higher magnitude Env-biased HIV-1-specific CD8(+) T-cell responses and 100-fold greater antibody titers measured by ELISA. There was no significant neutralizing antibody activity against primary isolates. Vaccine-elicited CD4(+) and CD8(+) T-cells expressed multiple functions and were predominantly long-term (CD127(+)) central or effector memory T cells and that persisted in blood for >6 months. Epitopes mapped in Gag and Env demonstrated partial cross-clade recognition. CONCLUSION: Heterologous prime-boost using vector-based gene delivery of vaccine antigens is a potent immunization strategy for inducing both antibody and T-cell responses. TRIAL REGISTRATION: ClinicalTrials.gov NCT00102089, NCT00108654.