MGP, IV, MD, JH and JS are all employees of Janssen, J&J (formerly Crucell). The salaries for these authors were provided by Janssen, J&J (formerly Crucell). Janssen, J&J did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials. The specific roles of these authors are articulated in the 'author contributions' section. No other authors have conflicts of interest.
Conceived and designed the experiments: JM MGP IV MD JH JS BL HM. Performed the experiments: SS SAH IS DAH VD LS ZRMT AM MW JM MKO PM. Analyzed the data: SS SAH IS DAH HM. Contributed reagents/materials/analysis tools: DAH JH HM. Wrote the paper: SS SAH IS DAH VD LS ZRMT AM MW SV JM MKO MGP IV MD JH JS BL PM HM. Trial management and coordination: SS SV BL PM.
MVA85A and AERAS-402 are two clinically advanced viral vectored TB vaccine candidates expressing
In this phase 1, open-label trial, 40 healthy previously BCG-vaccinated participants were enrolled into three treatment groups and vaccinated with 1 or 2 doses of AERAS-402 followed by MVA85A; or 3 doses of AERAS-402.
Most related adverse events (AEs) were mild and there were no vaccine related serious AEs. Boosting AERAS-402 with MVA85A significantly increased Ag85A-specific T-cell responses from day of vaccination. Two priming doses of AERAS-402 followed by MVA85A boost, resulted in a significantly higher AUC post-peak Ag85A response compared to three doses of AERAS-402 and historical data with MVA85A vaccination alone. The frequency of CD8+ T-cells producing IFN-γ, TNF-α and IL-2 was highest in the group receiving two priming doses of AERAS-402 followed by MVA85A.
Vaccination with AERAS-402 followed by MVA85A was safe and increased the durability of antigen specific T-cell responses and the frequency and polyfunctionality of CD8+ T-cells, which may be important in protection against TB. Further clinical trials with adenoviral prime-MVA85A boost regimens are merited to optimise vaccination intervals, dose and route of immunisation and to evaluate this strategy in the target population in TB high burden countries.
ClinicalTrials.gov
Tuberculosis (TB) remains a major global public health burden, with an estimated 9.0 million incident cases and 1.5 million deaths in 2013 [
MVA85A and AERAS-402 are two clinically advanced TB vaccine candidates. Both have been shown to boost immunity induced by prior BCG vaccination. MVA85A comprises the recombinant replication-deficient Modified Vaccinia virus Ankara expressing the immunodominant
This was a phase 1 open-label, non-randomized clinical vaccine with three treatment groups. The trial was approved by the Medicines and Healthcare products Regulatory Agency (MHRA, EudraCT 2012-002007-18), the Berkshire B Research Ethics Committee (reference12/SC/0283) and University Hospitals Birmingham NHS Foundation Trust Research and Development department (reference RRK4493). All participants provided written informed consent and the trial was conducted according to the principles of the Declaration of Helsinki and Good Clinical Practice. The CONSORT trial checklist and clinical trial protocol are available as
Subjects were recruited from the Centre for Clinical Vaccinology and Tropical Medicine, University of Oxford and the National Institute for Health Research (NIHR)/Wellcome Trust Clinical Research Facility at Birmingham. Screening and follow up visits occurred at both sites; all enrolment/vaccination visits occurred at the Oxford site.
Participants were BCG-vaccinated, healthy adults aged 18 to 55 with no clinically significant abnormalities in baseline haematology or biochemistry, negative serological testing for HIV, hepatitis B and hepatitis C viruses and a body mass index between 18 and 33 (kg/m2). Previous AERAS-402 clinical vaccine trials have included a Body Mass Index of > 33 kg/m2 as an exclusion factor; this was maintained in this study for consistency to allow comparison with previous clinical vaccine trials. Latent
AERAS-402 (1x1011 viral particles) was administered intramuscularly and MVA85A (1x108 plaque forming units) was administered intradermally in the deltoid region of the upper arm. Subjects in Group A received AERAS-402 at study day (D) 0 and D28 and MVA85A at D119. Subjects in Group B received AERAS-402 at D0 and MVA85A at D56. Subjects in Group C received AERAS-402 at D0, D28 and D119.
The initial plan was to enrol 15 subjects into each arm. However, due to challenges with enrolment the protocol was amended and 12 subjects were enrolled into Group A, 16 into Group B and 12 into Group C (
CONSORT flow diagram showing subject recruitment and follow up. Subjects were allocated to Groups A and B in parallel and once both groups were complete, subjects were enrolled to Group C. *One subject was lost to follow up in Group B post day 14 follow up visit. All AEs post Day 0 vaccination had resolved prior to loss to follow up. **Two subjects withdrew from the study; one subject withdrew from Group B post first vaccination as did not wish to undergo any further venepunctures; one subject withdrew from Group C post second vaccination due to unexpected relocation. Both withdrawals were not considered related to vaccination and all AEs had resolved prior to withdrawal. The subject lost to follow up and the subject who withdrew from Group A was replaced; the subject who withdrew from Group C was not replaced as the study was nearing completion.
Groups A and B were enrolled in parallel and once complete, subjects were enrolled into Group C. Subjects were not randomised to facilitate enrolment as the groups had different visit schedules.
Volunteers were enrolled within 90 days of screening visit. Volunteers in Groups A and C were followed up until day 203 (3 months post final vaccination visit at D119) and volunteers in Group B were followed up until day 140 (3 months post final vaccination visit at D56).
The primary endpoint was safety as assessed by frequency and severity of vaccine-related local and systemic adverse events (AEs). Expected local AEs (pain, erythema, swelling, warmth, pruritus, scaling, axillary lymphadenopathy and axillary tenderness) and systemic AEs (documented fever >38°C, feverishness, malaise, arthralgia, headache, myalgia, nausea, vomiting, fatigue, diarrhoea, dysuria, conjunctivitis, sore throat and upper respiratory tract type symptoms (cough and rhinorrhoea)) were solicited from subjects using a diary card for 7 days post-vaccination and at each follow-up visit. Haematology and biochemistry analysis was conducted at screening, and at D28, 42, 119 and 126 for subjects in Groups A and C, and at D14, 56 and 63 for Group B.
The secondary endpoint was immunogenicity of vaccinations in all three groups. This was measured by the ex vivo interferon-gamma (IFN-γ) ELISpot assay performed on fresh peripheral blood mononuclear cells (PBMC) stimulated with pools of mycobacterial peptides, as well as flow cytometric estimation of T cell IFN-γ, TNF-α, and IL-2 production, as quantified by intracellular cytokine staining (ICS). Blood samples for immunological analysis were taken at each study visit for all subjects: Days 0 (first vaccination), 28,42,56,119,126,147 and 203 for volunteers in Groups A and C and Days 0,14,28,56,63,84 and 140 for volunteers in Group B.
There were 21 protocol deviations during the trial period. 17 deviations were due to study visits which were out of specified time window as subjects could not attend on schedule due to unforeseen personal circumstances.
Safety bloods were omitted in error for one subject in Group A at D126; these bloods were within normal range when added at D147 visit.
Haematology safety bloods were collected in an incorrect vacutainer tube for one subject in Group C at D126 visit; these results were within normal range when repeated one week later.
Immunology bloods were omitted in error for one subject in Group A at D119 visit; these bloods were collected 4 days later, and within the window period for that study visit.
A lower dose of MVA85A (44 uL) was administered to one subject in Group B at D56 study visit as the subject had a vasovagal episode during vaccination.
These listed protocol deviations were not deemed to have an adverse impact on the safety of the subjects involved or on the scientific data collected during the trial period and therefore all data from all subjects was included in the analysis.
MVA85A was constructed as previously described [
Peripheral blood mononuclear cells (PBMC) were isolated from whole blood and interferon-gamma (IFN-γ) ELISpot assays were performed on freshly isolated PBMC from all subjects at 0, 28, 42, 56, 119, 126, 147 and 203 days post-vaccination (Groups A and C) and at 0, 14, 28, 56, 63, 84 and 140 days post-vaccination (Group B) as previously described [
Intracellular cytokine staining (ICS) was performed as previously described [
Recombinant Ag85A, Ag85B, and TB10.4, purified in-house at Aeras, were coated onto micro-well plates. The serum samples were diluted 1:100 and incubated with immobilized antigen for capture of antigen specific antibodies present in the serum samples. The captured antibodies were then probed by the addition of biotinylated anti-IgG antibodies and detected using a colorimetric substrate solution. Once the optimum color intensity was reached, the color development was stopped using a stop solution. The micro-well plates were read using an ELISA reader with SoftMax® Pro 5.4.1 data acquisition and analysis software.
The assay for Adenovirus 35 neutralizing activity was performed as previously described [
Safety data were summarised by frequency and severity of adverse events using descriptive statistics. ELISpot data was analysed using GraphPad Prism. The Mann Whitney U-test and Area Under the Curve (AUC) analysis were used to detect differences between groups. The Wilcoxon matched-pairs signed rank test was used to detect differences between time points within the same group.
The first volunteer was enrolled in October 2012 and the trial was completed in August 2014, within the expected 24 months trial duration.
Fifty three subjects were assessed for eligibility of which 40 were enrolled (See
The demographics of the enrolled subjects were comparable between the three groups (
Vaccine Group | ||||
---|---|---|---|---|
Group A (n = 12) | Group B (n = 16) | Group C (n = 12) | ||
Male, n (%) | 7 (58%) | 7 (44%) | 7 (58%) | |
Median age in years (range) | 23 (19–51) | 26 (19–54) | 27 (20–54) | |
Median time interval since BCG in years (range) | 9 (2–30) | 19 (1–41) | 12 (0–46) | |
BMI (kg/m2) (range) | 25 (20–32) | 25 (18–30) | 24 (19–31) | |
Europe | 12 | 14 | 10 | |
Asia | 0 | 1 | 2 | |
Australia | 0 | 1 | 0 |
Abbreviations: BCG, Bacillus Calmette–Guérin; BMI, Body mass index.
There were 908 adverse events (AEs) of which 708 (78%) were considered related to vaccination. Most AEs were mild or moderate (
Group A | Group B | Group C | Total AEs | |||||||
---|---|---|---|---|---|---|---|---|---|---|
Mild | 285 | 208 | 224 | 717 (79%) | ||||||
Moderate | 70 | 55 | 43 | 168 (19%) | ||||||
Severe | 7 | 2 | 14 | 23 (2%) | ||||||
Day 0 (n = 12) | Day 28 (n = 12) | Day 119 (n = 12) | Day 0 (n = 16) | Day 56 (n = 14) | Day 0 (n = 12) | Day 28 (n = 12) | Day 119 (n = 11) | |||
Mild | 26 | 23 | 59 | 23 | 73 | 27 | 22 | 19 | 272 (87%) | |
Moderate | 5 | 5 | 4 | 11 | 4 | 1 | 5 | 0 | 35 (11%) | |
Severe | 1 | 2 | 0 | 0 | 0 | 2 | 0 | 0 | 5 (2%) | |
Mild | 32 | 47 | 24 | 46 | 22 | 39 | 44 | 32 | 286 (72%) | |
Moderate | 25 | 18 | 7 | 22 | 7 | 15 | 9 | 0 | 103 (26%) | |
Severe | 0 | 0 | 0 | 0 | 0 | 3 | 1 | 3 | 7 (2%) | |
Abbreviations: AEs, adverse events.
One unrelated Serious Adverse Event occurred in a subject 80 days post final vaccination in Group A. This subject was diagnosed with presumptive Dengue fever while travelling in an endemic region, hospitalised for 2 days for supportive treatment and made a full recovery.
23 severe AEs were reported of which 12 were considered related to vaccination and occurred post AERAS-402 vaccination. Four subjects recorded transient severe pain (2 in Group A and 2 in Group C) and one subject recorded transient severe swelling at the vaccination site after AERAS-402.
One subject reported feverishness and malaise on D1 post first AERAS-402 vaccination requiring one day absence from work; this subject also recorded a fever (39.3°C) on the day of vaccination which returned to 37.3°C within 6 hours. This same subject reported nausea and abdominal pain post the third AERAS-402 vaccination requiring one day absence from work, with resolution of symptoms by D2 post vaccination. Another subject reported severe headache on the evening of third AERAS-402 vaccination which resolved within 24 hours. These AEs was assigned possible causality due to temporal association with vaccination.
21 laboratory abnormalities were detected of which 13 (11 mild, 1 moderate and 1 severe) were considered related to AERAS-402 vaccination. There were no laboratory AEs related to MVA85A vaccination. One subject in Group C had a moderate increase in alanine transaminase and a severe increase in aspartate aminotransferase post second AERAS-402 vaccination. Both returned to baseline prior to third vaccination and were considered possibly related to vaccination due to a temporal association with vaccination. All related laboratory AEs were transient, asymptomatic and returned to baseline by the end of the trial. All related AEs (including laboratory AEs) are listed in
Group A | Group B | Group C | |||||||
---|---|---|---|---|---|---|---|---|---|
Adverse events | Vaccine | AERAS-402 | AERAS-402 | MVA85A | AERAS-402 | MVA85A | AERAS-402 | AERAS-402 | AERAS-402 |
Day 0 (n = 12) | Day 28 (n = 12) | Day 119 (n = 12) | Day 0 (n = 16) | Day 56 (n = 14) | Day 0 (n = 12) | Day 28 (n = 12) | Day 119 (n = 11) | ||
Axillary lymphadenopathy | 2(17%) | 0(0%) | 3(25%) | 0(0%) | 3(21%) | 0(0%) | 0(0%) | 0(0%) | |
Axillary tenderness | 0(0%) | 1(8%) | 2(17%) | 0(0%) | 1(7%) | 1(8%) | 1(8%) | 0(0%) | |
Local erythema | 6(50%) | 6(50%) | 12(100%) | 8(50%) | 14(100%) | 9(75%) | 7(58%) | 5(45%) | |
Local pain | 12(100%) | 10(83%) | 9(75%) | 15(94%) | 9(64%) | 12(100%) | 11(92%) | 8(73%) | |
Local pruritus | 2(17%) | 1(8%) | 6(50%) | 1(6%) | 10(71%) | 1(8%) | 0(0%) | 0(0%) | |
Local scaling | 0(0%) | 0(0%) | 10(83%) | 0(0%) | 13(93%) | 0(0%) | 0(0%) | 0(0%) | |
Local swelling | 3(25%) | 4(33%) | 12(100%) | 2(13%) | 14(100%) | 6(50%) | 5(42%) | 4(36%) | |
Local warmth | 6(50%) | 5(42%) | 8(67%) | 8(50%) | 10(71%) | 1(8%) | 3(25%) | 1(9%) | |
Injection site bruise | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 1(9%) | |
Arthralgia | 3(25%) | 5(42%) | 2(17%) | 3(19%) | 2(14%) | 5(42%) | 4(33%) | 3(27%) | |
Cough | 1(8%) | 3(25%) | 0(0%) | 1(6%) | 1(7%) | 0(0%) | 1(8%) | 0(0%) | |
Diarrhoea | 2(17%) | 1(8%) | 0(0%) | 2(13%) | 0(0%) | 1(8%) | 1(8%) | 0(0%) | |
Fatigue | 8(67%) | 9(75%) | 6(50%) | 8(50%) | 5(36%) | 10(83%) | 8(67%) | 6(55%) | |
Documented fever | 2(17%) | 3(25%) | 0(0%) | 0(0%) | 0(0%) | 2(17%) | 1(8%) | 0(0%) | |
Felt feverish | 10(83%) | 8(67%) | 3(25%) | 9(56%) | 5(36%) | 9(75%) | 7(58%) | 7(64%) | |
Headache | 9(75%) | 8(67%) | 5(42%) | 10(63%) | 8(57%) | 10(83%) | 8(67%) | 6(55%) | |
Malaise | 7(58%) | 6(50%) | 5(42%) | 8(50%) | 3(21%) | 8(67%) | 8(67%) | 7(64%) | |
Myalgia | 7(58%) | 7(58%) | 2(17%) | 8(50%) | 3(21%) | 7(58%) | 7(58%) | 2(18%) | |
Nausea | 0(0%) | 2(17%) | 1(8%) | 5(31%) | 0(0%) | 1(8%) | 1(8%) | 2(18%) | |
Rhinorrhoea | 2(17%) | 5(42%) | 4(33%) | 2(13%) | 1(7%) | 1(8%) | 1(8%) | 0(0%) | |
Sore eyes | 1(8%) | 2(17%) | 1(8%) | 3(19%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | |
Sore throat | 2(17%) | 1(8%) | 2(17%) | 2(13%) | 1(7%) | 1(8%) | 1(8%) | 0(0%) | |
Vomiting | 1(8%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 1(9%) | |
Abdominal pain | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 1(9%) | |
Chills | 0(0%) | 1(8%) | 0(0%) | 2(13%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | |
Insomnia | 0(0%) | 0(0%) | 0(0%) | 1(6%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | |
Lightheadedness | 0(0%) | 0(0%) | 0(0%) | 1(6%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | |
Loss of appetite | 0(0%) | 0(0%) | 0(0%) | 1(6%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | |
Migraine | 0(0%) | 1(8%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | |
Night sweats | 0(0%) | 0(0%) | 0(0%) | 1(6%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | |
Rigors | 0(0%) | 1(8%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | |
Elevated ALT | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 2(17%) | 0(0%) | |
Elevated AST | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 2(17%) | 0(0%) | |
Hyperbilirubinaemia | 1(8%) | 0(0%) | 0(0%) | 1(6%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | |
Lymphopaenia | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 0(0%) | 1(8%) | 0(0%) | |
Neutropaenia | 1(8%) | 2(17%) | 0(0%) | 0(0%) | 0(0%) | 2(17%) | 1(8%) | 0(0%) |
Local adverse events that were reported twice by individual subjects (8 adverse events) in the seven day diary card period are included in the summary adverse event
All related adverse events were reported during the seven day diary card period apart from one volunteer who reported axillary tenderness at day 20 post second AERAS-402 vaccination which was deemed possibly related to vaccination. Abbreviations: AEs, adverse events; ALT, alanine transaminase; AST, aspartate aminotransferase.
In all groups, ex-
Responses to Ag85A (A), Ag85B (B) and TB10.4 (C) in BCG-vaccinated, healthy adults for Group A (AERAS-402, AERAS-402, MVA85A), Group B (AERAS-402, MVA85A) and Group C (AERAS-402, AERAS-402, AERAS-402). Responses to Ag85A are also shown from TB022 (MVA85A). Box and whisker plots show median, inter-quartile range, minimum and maximum values. Stars denote significant changes in responses after vaccination (Wilcoxon matched pairs) * p = < 0.05, ** p = < 0.01, *** p = < 0.001, ns = not significant.
Area under the curve (AUC) analysis was performed on Groups A, B, C and subjects from a previous trial, TB022, who received MVA85A alone [
There was no difference between groups in their baseline responses to the adenovirus peptides. After first vaccination with AERAS-402, responses in all groups increased significantly (
Responses to MVA peptides for CD4+ (A), and CD8+ T-cell epitopes (B) and summed responses to 3 pools of adenovirus peptides (C) in BCG-vaccinated, healthy adults for Group A (AERAS-402, AERAS-402, MVA85A), Group B (AERAS-402, MVA85A) and Group C (AERAS-402, AERAS-402, AERAS-402). Box and whisker plots show median, inter-quartile range, minimum and maximum values. Stars denote significant changes in responses after vaccination (Wilcoxon matched pairs) * p = < 0.05, ** p = < 0.01, *** p = < 0.001, ns = not significant.
AUC was done at week 1, 4 and 12 post MVA85A for Group A, B and MVA85A alone [
Total intracellular cytokine responses are presented as percentages of CD4+ T-cells or CD8+ T-cells producing mycobacteria-specific IFN-γ, TNF-α and IL-2 cytokines. Percentage of CD4+ (A, C and E) and CD8+ (B, D and F) responses in peripheral blood mononuclear cells to stimulation with Ag85A (A and B), Ag85B (C and D) and TB10.4 (E and F) peptides in healthy, BCG-vaccinated adults from Group A (AAM, green line), Group B (AM, blue line), Group C (AAA, red line) and TB022 (M, black line). Lines show median responses in each group, whiskers show inter-quartile range.
No significant differences were detected between Group B and Group C in CD4+ T-cell or CD8+ T-cell responses to any antigens. Both the CD4+ and CD8+ T-cell response were significantly higher in Group A as compared to Group B in response to Ag85A (CD4 p = 0.0127; CD8 p = 0.0172) and Ag85B (CD4 p = 0.0173; CD8 p = 0.0233).
AUC analysis for the expression of the CD4+ T-cell activation marker, CD154, was significantly higher in Group A than in Group C in both Ag85A- and Ag85B-stimulated cells (p = 0.01 and p = 0.0068 respectively, data not shown).
After MVA85A vaccination, CD4+ and CD8+ T cell responses to Ag85A were higher in Group B when compared with MVA85A alone (
Ag85A CD4+ T-cells cytokines were significantly higher in Group A than in Group C post third vaccination (
At peak time points, (D126 for Groups A and C, D63 for Group B and D7 for TB022), Group A had less Ag85A CD4+ polyfunctional positive T-cells than Group B. Groups A and B had more Ag85A-specific polyfunctional CD4+ T-cells than Group C. All three groups had less polyfunctional Ag85A-specific CD4+ T-cells than samples from TB022 (
Polyfunctionality of CD4+ (A, C, E and G) and CD8+ (B, D, F and H) T-cells in response to stimulation with Ag85A and Ag85B peptides in healthy, BCG-vaccinated adults from Group A (AAM, green), Group B (AM, blue), Group C (AAA, red) and TB022 (M, black). Panels A-D show peak responses to Ag85A (A and B) and Ag85B (C and D), whereas panels E-H show plateau responses to Ag85A (E and F) and Ag85B (G and H). Plots show box and whisker with inter-quartile range and minimum and maximum values.
Polyfunctional CD8+ T-cells responses were only observed when MVA85A was preceded by AERAS-402 (
At plateau, (D203 for Groups A and C, D140 for Group B and D84 for TB022), Group C had less polyfunctional Ag85A CD4+ T-cell response than all other groups (
Ag85A-specific IgG responses increased significantly after vaccination with AERAS-402 and MVA85A (
Serum antibody responses to Ag85A (A), Ag85B (B) and TB10.4 (C) in the three study groups; Group A (AERAS-402, AERAS-402, MVA85A), Group B (AERAS-402, MVA85A) and Group C (AERAS-402, AERAS-402, AERAS-402). Antibody responses were measured in optical density (OD), data is presented as fold change responses calculated by dividing each time point’s antibody response by its corresponding day 0 response. Box and whisker plots show median, inter-quartile range, minimum and maximum values. Stars denote significant changes in responses after vaccination (Wilcoxon matched pairs) * p = < 0.05, ** p = < 0.01, *** p = < 0.001, ns = not significant.
AUC analyses for neutralising antibody responses show no significant differences between the three groups (data not shown).
We report the first TB clinical vaccine trial to evaluate an adenoviral prime—MVA boost regimen. The safety profile of AERAS-402 and MVA85A were comparable to data reported previously [
The vast majority of systemic AEs were mild or moderate in nature. There were 7 severe systemic AEs that were considered related to AERAS-402 vaccination, 4 of which were considered possibly related due to temporal association with vaccination. All of the vaccine related severe systemic AEs, apart from the transient rise in AST discussed below, resolved within 48 hours. The most objective measurement of systemic reactogenicity, pyrexia, was reported as severe on only one occasion throughout the study, a recorded fever of 39.3°C on the day of first AERAS-402 vaccination in a volunteer in Group C, which returned to normal within 6 hours. There was one severe laboratory AE, a transient elevation in AST post second AERAS-402 vaccination in Group C, which normalised prior to third vaccination. This AE was deemed possibly related to vaccination due to temporal association; the rise in AST may also have been attributable to excessive exercise prior to safety bloods measurement. There were no vaccination deferrals and there were no study withdrawals attributable to related AEs.
Ex-
Multiparameter flow cytometry showed a high frequency of cytokine producing CD8+ T-cells in Ag85A and Ag85B-stimulated PBMC after MVA85A boost in Groups A and B, with Group A showing a higher frequency post-boost. At peak response post-MVA85A, the frequency of polyfunctional CD4+ T-cells producing IFN-γ, TNF-α and IL-2, and expressing CD154, a marker of CD4+ T-cell activation, in response to stimulation with Ag85A, was highest in the MVA85A alone group, followed by Group B and then Group A. However, the frequency of CD8+ T-cells producing all 3 cytokines and upregulating the expression of CD107a, an indicator of CD8+ T-cell cytotoxicity, was highest in Group A, followed by Group B and barely detectable in the MVA85A alone group. The same trend is true for plateau responses, but with reduced frequencies.
Ag85A-specific IgG responses peaked four weeks after vaccination with MVA85A, but did not significantly differ between the groups receiving either one or two doses of AERAS-402 prime. However, responses were higher in both of the Adenovirus prime-MVA boost groups than either the MVA or Adenoviral alone groups. Although cell-mediated immunity is crucial in protection against TB, the role of antibody responses in protection against TB is of increasing interest; sera from TB contacts with high tuberculin-specific IgG titers has been shown to block proliferation of PBMC cultured with tuberculin [
We have shown that an AERAS-402 prime-MVA85A boost regimen increases durability of antigen specific T-cell responses, increases the frequency and polyfunctionality of CD8+ T-cells and increases antibody responses when compared with AERAS-402 or MVA85A vaccination alone. This improved cellular and humoral immunogenicity may be important in protection against TB. One of the challenges faced by the TB vaccine field is the low immunogenicity induced by candidate vaccines in the target population, compared to UK adults. This adenoviral prime-MVA boost strategy may increase the magnitude and durability of vaccine-induced responses and broaden the quality of the immune response in the target population. Further studies with adenoviral prime-MVA85A boost regimens are merited to optimise intervals between vaccinations, dose and route of immunisation, and also to evaluate this strategy in the target population in TB high burden countries.
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The authors wish to thank Eleanor Berry, Alison Lawrie, Natalie Lella, Ian Poulton, Mary Smith, Raquel Lopez Ramon, Jack Quaddy, Karen Boardman, Anthea Williams, Abigail Robb, Mariea Parvaz, Dawn M O’Dee, Andrew J.Graves, Gretta Blatner, Lew Barker, Jacqueline O’Shea, Stephen Lockhart and all the trial participants. We also wish to acknowledge the Wellcome Trust Clinical Research Facility, Birmingham for contribution to trial recruitment.