Alternate aerosol and systemic immunisation with a recombinant viral vector for tuberculosis, MVA85A: A phase I randomised controlled trial

Abstract

Background: There is an urgent need for an effective tuberculosis (TB) vaccine. Heterologous prime-boost regimens induce potent cellular immunity. MVA85A is a candidate TB vaccine. This phase I clinical trial was designed to evaluate whether alternating aerosol and intradermal vaccination routes would boost cellular immunity to the Mycobacterium tuberculosis antigen 85A (Ag85A).

Methods and findings: Between December 2013 and January 2016, 36 bacille Calmette-Guérin-vaccinated, healthy UK adults were randomised equally between 3 groups to receive 2 MVA85A vaccinations 1 month apart using either heterologous (Group 1, aerosol-intradermal; Group 2, intradermal-aerosol) or homologous (Group 3, intradermal-intradermal) immunisation. Bronchoscopy and bronchoalveolar lavage (BAL) were performed 7 days post-vaccination. Adverse events (AEs) and peripheral blood were collected for 6 months post-vaccination. The laboratory and bronchoscopy teams were blinded to treatment allocation. One participant was withdrawn and was replaced. Participants were aged 21-42 years, and 28/37 were female. In a per protocol analysis, aerosol delivery of MVA85A as a priming immunisation was well tolerated and highly immunogenic. Most AEs were mild local injection site reactions following intradermal vaccination. Transient systemic AEs occurred following vaccination by both routes and were most frequently mild. All respiratory AEs following primary aerosol MVA85A (Group 1) were mild. Boosting an intradermal MVA85A prime with an aerosolised MVA85A boost 1 month later (Group 2) resulted in transient moderate/severe respiratory and systemic AEs. There were no serious adverse events and no bronchoscopy-related complications. Only the intradermal-aerosol vaccination regimen (Group 2) resulted in modest, significant boosting of the cell-mediated immune response to Ag85A (p = 0.027; 95% CI: 28 to 630 spot forming cells per 1 × 106 peripheral blood mononuclear cells). All 3 regimens induced systemic cellular immune responses to the modified vaccinia virus Ankara (MVA) vector. Serum antibodies to Ag85A and MVA were only induced after intradermal vaccination. Aerosolised MVA85A induced significantly higher levels of Ag85A lung mucosal CD4+ and CD8+ T cell cytokines compared to intradermal vaccination. Boosting with aerosol-inhaled MVA85A enhanced the intradermal primed responses in Group 2. The magnitude of BAL MVA-specific CD4+ T cell responses was lower than the Ag85A-specific responses. A limitation of the study is that while the intradermal-aerosol regimen induced the most potent cellular Ag85A immune responses, we did not boost the last 3 participants in this group because of the AE profile. Timing of bronchoscopies aimed to capture peak mucosal response; however, peak responses may have occurred outside of this time frame.

Conclusions: To our knowledge, this is the first human randomised clinical trial to explore heterologous prime-boost regimes using aerosol and systemic routes of administration of a virally vectored vaccine. In this trial, the aerosol prime-intradermal boost regime was well tolerated, but intradermal prime-aerosol boost resulted in transient but significant respiratory AEs. Aerosol vaccination induced potent cellular Ag85A-specific mucosal and systemic immune responses. Whilst the implications of inducing potent mucosal and systemic immunity for protection are unclear, these findings are of relevance for the development of aerosolised vaccines for TB and other respiratory and mucosal pathogens.

Trial registration: ClinicalTrials.gov NCT01954563.

Conflict of interest statement

I have read the journal’s policy and the authors of this manuscript have the following competing interests: HMcS is a Jenner Institute Investigator and a Wellcome Trust Senior Clinical Research Fellow. ZM was a NIHR BRC Clinical Research Training fellow.

Figures

Fig 1. CONSORT diagram.

GP, general practitioner; LTBI, latent tuberculosis infection.

Fig 2. Frequency of related solicited adverse events.

Frequency of related solicited adverse events experienced at least once; recorded at peak severity grading in the 28 days following each vaccination. Red = severe, yellow = moderate, green = mild. X axis = number of volunteers, Y axis = symptoms. (a and b) Group 1, n = 12; (c and d) Group 2, vaccination 1, n = 13, vaccination 2, n = 9; (e and f) Group 3, n = 12.

Fig 3. Frequency of antigen-specific IFNγ secreting cells to Ag85A, MVA CD4 peptides, and MVA CD8 peptides by group.

Frequency of antigen-specific IFNγ secreting cells to (a–c) Ag85A peptides (top row), (d–f) MVA CD4 peptides (middle row), and (g–i) MVA CD8 peptides (bottom row) in Group 1 (left column), Group 2 (middle column), and Group 3 (right column). X axis: time points in days, Y axis: SFC per 1 × 106 PBMCs. Shown are significant differences from baseline (day 0). Non-significant differences (p > 0.05) omitted for clarity. *p < 0.05, **p < 0.01, ***p < 0.001. Ag85A, antigen 85A; MVA, modified vaccinia virus Ankara; PBMC, peripheral blood mononuclear cell; SPC, spot forming cells.

Fig 4. WB ICS Ag85A-specific CD4+ T cell responses.

WB ICS Ag85A-specific CD4+ T cells positive for IFNγ (a), TNFα (b), IL2 (c), and IL17 (d) and CD8+ T cells positive for IFNγ (e) and TNFα (f). X axis = time points in days, Y axis = percent of CD4+ or CD8+ T cells positive for that cytokine. Statistically significant differences from baseline and between groups are shown. Non-significant differences (p > 0.05) are omitted for clarity. *p < 0.05, **p < 0.01, ***p < 0.001. Note the different Y axis scales. Ag85A, antigen 85A; ICS, intracellular cytokine staining; WB, whole blood.

Fig 5. Whole blood ICS MVA-specific CD4+ and CD8+ T cells positive for IFNγ and TNFα.

X axis = time points in days, Y axis = percent of CD4+ (a and b) or CD8+ T (c and d) cells positive for that cytokine. Statistically significant differences from baseline and between groups are shown. Non-significant differences (p > 0.05) are omitted for clarity. *p < 0.05, **p < 0.01. Note the different Y axis scales. Ag85A, antigen 85A; BAL, bronchoalveolar lavage; ICS, intracellular cytokine staining; MVA, modified vaccinia virus Ankara.

Fig 6. BAL Ag85A-specific CD4+ T cell responses.

BAL Ag85A-specific CD4+ T cells positive for IFNγ (a), TNFα (b), IL2 (c), and IL17 (d) and Ag85A-specific CD8+ T cells positive for IFNγ (e) and TNFα (f). Non-significant differences (p > 0.05) are omitted for clarity. *p < 0.05, **p < 0.01, ***p < 0.001. Note the different Y axis scales. Ag85A, antigen 85A; BAL, bronchoalveolar lavage.

Fig 7. BAL Ag85A-specific polyfunctional CD4+ and CD8+ T cell responses.

(a) CD4+ IFNγ+ TNFα+ IL2+ IL17+; (b) CD4+ IFNγ+ TNFα+ IL2+, (c) CD4+ IFNγ+ TNFα+ IL17+; (d) CD4+ IFNγ+ TNFα+; (e) CD4+ IFNγ+ IL2+, (f) CD4+ IFNγ+ IL17+; (g) CD8+ IFNγ+ TNFα+. Non-significant differences (p > 0.05) are omitted for clarity. *p < 0.05, **p < 0.01, ***p < 0.001. Note the different Y axis scales. Ag85A, antigen 85A; BAL, bronchoalveolar lavage.

Fig 8. BAL MVA-specific CD4+ T cell responses.

BAL MVA-specific CD4+ T cell responses (a and b) and CD8+ T cell responses (c and d) positive for cytokines IFNγ and TNFα. Non-significant differences (p > 0.05) are omitted for clarity. *p < 0.05, **p < 0.01. Ag85A, antigen 85A; BAL, bronchoalveolar lavage; MVA, modified vaccinia virus Ankara.

Fig 9. Serum IgG responses.

Responses against Ag85A (a–c) and MVA (d–f) for Groups 1, 2, and 3 (from left to right). X axis = time point in days, Y axis = OD read at 405 nm. Non-significant differences (p > 0.05) are omitted for clarity. *p < 0.05, **p < 0.01, ***p < 0.001. p-Values denote significant differences from day 0. Note the different Y axis scales. Ag85A, antigen 85A; MVA, modified vaccinia virus Ankara; OD, optical density.