A Study to Quantify Bacille Calmette Guerin (BCG) and Characterise the Immune Response After BCG Vaccination
Condition: Tuberculosis
MeSH terms: Tuberculosis
Study type: Interventional
Phase: Phase 1

Summary: 
      This is a human pilot study of 16 healthy BCG-naïve volunteers to quantify BCG from the BCG
      vaccination site. Volunteers will be vaccinated with BCG. The first 8 will go on to have a
      punch biopsy and suction blister of the vaccination sites at 2 weeks post vaccination (arm A)
      the second 8 will have a biopsy and blister at 1 or 4 weeks post-vaccination (arm B). Methods
      of mycobacterial quantification on these tissue samples will then be compared
    

Detailed description: 
      Over the last 3 years, the McShane group in Oxford have established a clinical trial
      programme to evaluate the safety and immunogenicity of this BCG prime-MVA85A boost
      vaccination strategy in a series of Phase I studies in the UK.

      To date, in Oxford, the safety and immunogenicity of MVA85A (dose 5x10^7 pfu) has been
      assessed in 14 mycobacterially and BCG naïve individuals, 27 individuals previously
      vaccinated with BCG and 12 individuals latently infected with M.tb. In all 53 individuals
      there have been no serious or severe adverse events, and a single vaccination with MVA85A has
      been highly immunogenic in BCG naïve volunteers, and significantly moreso in BCG primed
      volunteers. (23) Following the success of the UK studies, 21 healthy individuals (11 BCG
      naïve, 10 BCG primed) in the Gambia and 24 healthy adults in Cape Town, South Africa (ongoing
      age de-escalation phase II trial), have now been vaccinated with MVA85A, with no serious or
      severe adverse events, and a safety and immunogenicity profile comparable to the UK. A study
      in infants in the Gambia is now underway and the adolescent arm of the age de-escalation
      studies in Cape Town is now also underway.

      Interferon-gamma as a protective correlate and the need to identify other immunological
      correlates of protection:

      In all of the studies to date, (both preclinical and clinical), the main immunological
      readout has been the ex-vivo interferon-gamma (IFN- ) Elispot assay, used to assess specific
      T cell responses to tuberculin PPD, purified antigen 85 complex and pools of overlapping
      15mer peptides spanning the length of antigen 85A. The secretion of IFN-y from
      antigen-specific T cells is the best available immunological correlate of protective
      immunity. The rationale and evidence supporting the use of assays for determining IFN-
      production as a correlate of protection are substantial, but alone, it may not be sufficient.
      There is increasing evidence that CD4(+) T cells possess IFN-gamma-independent mechanisms
      that can limit the growth of an intracellular pathogen and are dominant in secondary
      responses to M. tuberculosis.

      It is clear that new immunological correlates of protection need to be identified, and given
      the considerable time and cost involved in any Phase III efficacy trial of a new TB vaccine,
      there is therefore an urgent need to identify protective correlates which will help
      distinguish between candidates demonstrated to be safe and immunogenic in phase I trials.

      Whilst we cannot infect human volunteers with TB to address this issue, we can use another
      replicating mycobacteria, BCG, as a surrogate. A good vaccine for TB should also reduce BCG
      replication and increase BCG clearance. The objective of this proposal is to perform the
      preliminary work necessary to develop such a BCG 'challenge' model in which bacterial (BCG)
      load in the skin is assessed following vaccination with MVA85A.

      Such a challenge model is based on evidence that animals given subunit vaccination against TB
      have attenuated T cell responses to replicating mycobacteria administered as challenge
      agents. The hypothesis for this model is that replication of BCG and hence the induction of a
      BCG induced immune response will be abrogated by pre-existing immunity induced by a subunit
      vaccine, MVA85A. In addition, replication of intradermal BCG administered as a challenge
      agent can be assessed by biopsies of volunteers' skin. So, these methods would allow
      correlation of immune responses elicited by MVA85A vaccination with direct or indirect
      measures of diminished intradermal mycobacterial (BCG) replication in humans.

      There are three parts to this model:

        1. Preliminary mouse pilot study

           This involves current ongoing work to identify the time at which the mycobacterial load
           at the BCG vaccination site (ear) may be at its highest (and therefore most detectable
           by bacterial quantification methods), in a murine model:

           Mice are being vaccinated with intradermal BCG, into the ear, and then sacrificed at
           different timepoints, the ears and lymphoid tissues being harvested for BCG
           quantitation.

           Real -time PCR (RTPCR), histological analysis using staining with Ziehl-Nielson and
           mycobacterial culture techniques are being performed on the tissues to quantify the BCG
           present. Numbers of BCG present at all timepoints are being compared. Preliminary work
           suggests that BCG replication at the vaccination site decreases with time, but this is
           being investigated further. The results from this have advised on the timings of biopsy
           and blister in the human pilot study, such that the chances of recovering significant
           numbers of BCG will be maximised.

        2. Human pilot study based on results of 1) This proposal refers to this part of the model.
           24 BCG naïve human volunteers will be vaccinated with BCG (SSI strain) intradermally
           into the deltoid muscle of each arm. The total dose given will be the standard dose used
           in BCG vaccination programs worldwide: 0.1ml of 2-8x10^6 pfu/ml, i.e., 2-8x10^5 pfu. In
           this study half this dose (1-4x10^5 pfu) will be administered into each arm. All
           volunteers will then have a punch biopsy at one vaccination site and a suction blister
           formed at the other, (so that each volunteer will be their own comparison), at 3
           different timepoints post-vaccination.

           Preliminary BCG quantitation methods on the biopsy tissue from the first 6 volunteers
           (who had a biopsy at 2 weeks post-vaccination) show that between 5x10^2 and 4x10^3 BCG
           cfu are present at the vaccination site, 2 weeks post-vaccination. We do not yet know if
           the replication of BCG in the skin peaks before, at, or after this timepoint.

           Results from the preliminary murine experiments suggest that BCG replication in the skin
           decreases over time, which would seem to necessitate another early timepoint in the
           human trial, to "catch" this replication. However, it is also known (from murine
           experiments) that maximal BCG replication in the local draining lymphoid tissue occurs
           at 3-4 weeks post-vaccination, so by not quantitating BCG in the skin at 4 weeks we may
           miss the peak of BCG replication. In addition we do not know if BCG replication
           intradermally in the mouse ear will necessarily resemble that in human skin.

           For these reasons, and in order to fully characterise the kinetics of BCG in human skin
           post-vaccination, we shall vaccinate 3 groups of volunteers as outlined in section 4,
           "Trial Design", incorporating both early and later timepoints for biopsy and blisters
           (1, 2 and 4 weeks).

           The suction blister is created using a standard technique used by a number of
           dermatology research groups; a negative pressure of 25-40 kPa (200-300mmHg) below
           atmospheric pressure is applied via a suction chamber, for 2 to 4 hours using a clinical
           suction pump (VP25 portable suction unit, Eschmann, Sussex, UK) until a unilocular
           blister measuring 10-15mm in diameter is formed. This procedure is painless.

           Mycobacterial quantification techniques will be applied to the biopsy and fluid
           specimens (RT-PCR and culture), and the timepoint yielding the highest numbers of BCG
           will then be chosen for the randomised human trial. In addition, flow cytometry assays
           will be applied to the blister fluid specimens to characterise the local cellular
           reaction to BCG.

        3. Future Prospective randomised human trial (based on results of 1 & 2):

      2 groups of BCG naïve subjects will be randomised to receive either a single immunization
      with MVA85A or saline. The numbers per group will be decided on the basis of the results from
      the murine work and BCG pilot study, accounting for the level of variability in BCG
      replication, such that the number per group should be able to reliably detect a significant
      difference in BCG replication between the 2 groups (should it exist). The vaccine-induced
      immune response will be fully characterised. At 4 weeks, all volunteers will then be
      "challenged" (intradermally) with BCG. BCG-induced immune responses will be monitored for a
      further 6 months. In addition, a punch biopsy (+/- suction blister) will be taken from the
      BCG vaccination site and the amount of bacteria present quantified. The correlation between
      any reduction in BCG replication and MVA85A-induced immune response will then be assessed, in
      order to identify a potential correlate of protection.

      Future candidate vaccines can then be assessed against their capacity to induce such an
      immune response.

      Potential risks to human subjects:

      The general risks to participants in this human pilot study are associated with phlebotomy,
      vaccination, punch biopsy and suction blister techniques. Mild tenderness, bruising, or
      fainting may result from venepuncture. The volume of blood drawn over the study period
      (504.5ml +/- 20ml) should not compromise these otherwise healthy subjects.

      BCG is a licensed vaccine which has been in use for the last 100 years, given to 4 billion
      people, and has an excellent safety profile.

      Potential vaccination risks include the following:

      (Local reactions: An inflammatory reaction as manifested by redness and swelling, that can
      form a small ulcer, may occur at the site of vaccine injection. This usually heals and leaves
      a small flat scar. It is also possible to develop some swelling of glands in the armpit, but
      less than one centimetre across. These are natural reactions to the vaccine.

      Uncommonly (less than 1 in 100 people) swelling of glands in the armpit to more than 1cm
      across or an ulcer that discharges fluid at the injection site may occur.

      Rare side effects (less than 1 in 1000 people) include inflammation of glands, sometimes with
      abscesses and discharge of fluid from the swellings.

      Systemic Reactions: Systemic reactions to immunization with BCG that could potentially occur
      are rare (less than 1 in 1000 people) and include low-grade fever and headache, and allergic
      reactions. Disseminated complications of BCG such as osteitis or osteomyelitis have also been
      reported but are extremely rare and have usually been reported in immunocompromised, not
      immunocompetent individuals.

      Punch biopsy and suction blister risks:

      There is a small risk that the punch biopsy site or blister site may become infected. If this
      did occur, treatment with antibiotics may be required. The punch biopsy site will heal to
      form a small scar. A small scar might develop at the blister site but often this is barely
      visible after several months.

      Allergic Reactions and Anaphylaxis: As with any vaccine, allergic reactions are possible.
      Very rarely allergic reactions to local anaesthetic (administered prior to the punch biopsy)
      may occur.

      Known Potential Benefits:

      Volunteers will benefit from partial protection against TB, by vaccination with BCG.
      Volunteers will gain some information about their general health status at the pre-study
      screening assessment. It is also hoped that the information gained from this study will
      contribute to the development of a safe and effective TB vaccine for HIV negative and
      positive individuals.
    

Intervention name(s): BCG
Intervention type(s): Biological
Intervention description(s): Mycobacterium bovis Bacille Calmette-Guerin
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Basic Science