Cervicovaginal Immune Responses to 3 Deltoid or Thigh Intramuscular (IM) TicoVac
Condition: Tick-Borne Encephalitis
MeSH terms: Encephalitis, Tick-Borne; Encephalitis
Study type: Interventional
Phase: Phase 4

Summary: 
      Many viral infections of global importance, including HIV, are transmitted across the mucosal
      surface of the genital tract. As immunity against these infections is likely to be primarily
      mediated by antibodies in mucosal secretions, developing techniques to increase the levels
      and persistence of antiviral antibody on mucosal surfaces may enhance the protection against
      a number of important infections. Preclinical studies have anatomically targeted vaccine
      antigens to sites where genital tract immunity is induced. This response is likely due to the
      ability of regional lymph Preclinical studies have anatomically targeted vaccine antigens to
      sites where genital tract immunity is induced. This response is likely due to the ability of
      regional lymph nodes to "pattern" the cell surface markers of responding vaccine specific
      lymphocytes with homing markers. In contrast, injecting a distant muscle (such as in the arm)
      which shares no anatomical relationship with the vagina, may not pattern cells with homing
      markers for the genital tract. Direct injection of inguinal lymph nodes is impractical in
      humans but intramuscular injection into the thigh will target antigens to the deep inguinal
      lymph nodes shared in common with the cervix/vagina.

      This study will be a Phase IV randomised, single centre, open label, laboratory assessment
      blinded exploratory trial to assess mucosal immunogenicity following three targeted
      intramuscular immunisations with TicoVac vaccine. 20 subjects will be randomised to each of2
      groups immunised in right deltoid or right anterolateral thigh.

      Following an initial screening visit subjects will be immunised at 0, 1 and 6 months. There
      will be follow up visits 5 days after each immunisation and a final visit at 7 months. Blood
      samples and cervicovaginal secretions will be taken prior to each immunisation for
      immunological measures. In addition, blood samples will be taken at each immunisation and
      follow up visit for measurement of peripheral blood mononuclear cells.

      The study is funded by ADITEC, which is a collaborative research programme that aims to
      accelerate the development of novel and powerful immunisation technologies for the next
      generation of human vaccines.
    

Detailed description: 
      The study will investigate whether targeting vaccine antigens to lymph nodes (internal iliac)
      which drain both the lower limb and the cervix/vagina alters the subsequent antibody response
      detected in the cervix/vagina, when compared with targeting vaccine antigens to unrelated
      lymph nodes such as those in the axilla that drain the right deltoid muscle of upper arm.

      The right arm has been specifically selected as lymphatics in the right upper part of the
      body drains directly into the blood stream via the right lymphatic duct with no shared
      lymphatic connections to the rest of the body. In contrast lymph from the rest of the body
      ultimately drains into the thoracic duct (see figure below). By immunising the right arm the
      investigators can be sure that vaccine antigens and antigen presenting cells and activated
      lymphocytes will not pass through any lymph nodes in common with the cervix or vagina. In
      contrast by injecting the anterolateral thigh (right side selected for uniformity) the
      investigators can be sure that vaccine antigens will pass through the external inguinal lymph
      nodes which will also receive antigens and lymphocytes responding to vaginal or cervical
      infection or inflammation. The choice of right leg is just to standardise.

      It is the investigators hypothesis therefore that as a result of antigen presentation and
      stimulation within a specifically "genital tract milieu" T &B lymphocytes leaving the
      external iliac nodes as a result of an immunisation into the thigh will be patterned in such
      a way as to more likely home back to the cervix and vagina due to the common drainage of the
      cervix, vagina and thigh (Figure 1) into the external iliac and lateral aortic lymph nodes.
      In contrast, cells leaving the axillary lymph nodes after immunisation of the right arm will
      enter the blood directly via the right lymphatic duct and so will not pass through any lymph
      nodes in common with the cervix and vagina.

      The investigators will detect an effect of targeted immunisation in a number of ways:

        1. By detecting increased levels of vaccine-specific antibodies in cervico-vaginal
           secretions as a result of more activated B cells (plasmablasts) homing back to the
           genital tract. IgG antibodies may be transudated from the blood but local mucosal IgG
           may also be produced. In contrast, mucosal IgA is most likely to be locally produced and
           may therefore be preferentially affected by targeted immunisation. However as individual
           levels of mucosal antibody vary widely between subjects, especially with IgA, the
           investigators will set primary endpoints on the basis of a fold-increase in antibody
           levels from baseline, rather than concentration. As mucosal IgG responses are generally
           more reliable and of greater magnitude the investigators have set the primary objective
           as vaccine-specific mucosal IgG after all three immunisations. Vaccine-specific mucosal
           IgA responses after all three immunisations are the secondary objective. The study has
           been powered on the basis of the investigators limited experience with similar vaccines
           to detect a doubling of proportions of responders for IgG and IgA. The investigators
           have based the fold-increase in vaccine-specific mucosal IgG and IgA on the
           investigators limited experience with a similar vaccine injected into the arm(7).

           In addition, the investigators will measure changes in other variables that are
           exploratory in nature as assays and quantification are less well established:

        2. By detecting a "mucosal" pattern of B cell responses in the blood with increased numbers
           of vaccine-specific B cells after genital targeted immunisation.

        3. By detecting differences in the cell surface phenotypic markers on vaccine-specific
           lymphocytes indicating a mucosal origin.

      There will be two treatment groups:

        -  Group 1 will receive the vaccine in the right deltoid muscle (upper arm) which drains to
           unrelated lymph nodes in the axilla.

        -  Group 2 will receive the vaccine in the upper anterolateral right thigh, from which
           antigens will be expected to drain to the inguinal lymph nodes that also drain the
           cervix/vagina.

      To ensure complete disconnection of draining lymph nodes it will always be the RIGHT arm or
      RIGHT leg that is immunised.

      It is hypothesised that targeting the internal iliac nodes will lead to an enhanced mucosal
      antibody response in the cervix/vagina, which will be detected by increased vaccine-specific
      IgA in cervico-vaginal secretions collected in a Softcup. In addition, lymphocytes (B and T
      cells) from external iliac lymph nodes may carry surface markers associated with mucosal
      homing and secrete different combinations of cytokines (Th17) than those emanating from
      axillary nodes which will express a systemic phenotype. This can be detected by flow
      cytometry, ELISPOT after bead separation using phenotypic markers, and other immunological
      assays.

      Immune response readouts will be IgG and IgA antibodies against the TBEV antigens in the
      vaccine, comparing the two groups at the time point when the peak response is expected (28
      days after third immunisation).

      As the investigators wish to investigate the ability of the vaccine to specifically prime
      subjects in a targeted way, participants must be naive to the vaccine antigens and so must
      not have had the vaccine or TBEV infection before. Therefore the investigators will use
      TicoVac - a TBEV vaccine licenced in the UK that UK adults have not generally received, as
      TBEV infection is not endemic in the UK. TicoVac is widely used in central and eastern Europe
      where TBEV is endemic but extremely uncommon, and is offered to travellers from UK to endemic
      areas who are likely to engage in high risk activity (hiking, trekking).

      Mucosal responses against TBEV are not relevant as TBEV is transmitted by tick bites. Immune
      responses to TicoVac will act as a model for other vaccines in which the mucosal antibody
      response in the vagina is of relevance to block infection (e.g. HIV, HPV, HSV) and in which
      targeted immunisation may increase efficacy.

      Although strictly speaking the induction of anti-TBEV antibodies in cervico-vaginal
      secretions is of no relevance to the efficacy of the TicoVac vaccine against a blood-injected
      virus, the investigators have designated them as parameters of efficacy in this model of
      targeted immunisation.

      The purpose of this human immune physiology study is to use TBEV vaccine as a model
      neoantigen to investigate immune readouts after antigen targeting. The collection of adverse
      event or safety data is therefore not relevant to the study objectives and there will be no
      systematic collection of safety data, other than those required for a Risk Assessed "Type A"
      CTIMP (SUSAR reporting to MHRA/REC/Concerned Investigators, Annual List of Suspected Serious
      Adverse Reactions as part of the Annual Safety Report/Development Safety Update Report).
    

Intervention name(s): TicoVac
Intervention type(s): Drug
Intervention description(s): Intramuscular immunisation to right deltoid muscle (Group 1) or right upper anterolateral thigh muscle (Group 2).
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Tick-Borne Encephalitis Virus