#CrohnsDisease #CD #MAP #vaccine #vaccination
Crohn’s disease (CD) is a
chronic inflammatory
condition of the gastrointestinal tract, marked by persistent intestinal
inflammation. Its etiology remains
poorly understood, resulting from a complex
interplay between
genetic predisposition, environmental factors, immune
dysregulation, and
alterations of the gut microbiota. Despite therapeutic
advances, the disease remains
progressive, recurrent, and incurable. A
significant
unmet medical need persists, especially for patients with
refractory disease or frequent relapses.
Among the pathogenic hypotheses being explored,
the involvement of an intracellular infectious agent—particularly Mycobacterium
avium subspecies paratuberculosis (MAP)—has regained interest. This
mycobacterium has been detected in the intestinal tissues of some CD patients
and may trigger or sustain a chronic immune response in genetically predisposed
individuals.
In this context, an innovative vaccine-based
approach has been explored through the development of two experimental
viral-vectored vaccines: ChAdOx2 HAV, based on a non-replicating simian
adenoviral vector, and MVA HAV, which uses a modified Ankara poxvirus
vector. These vaccines are designed to express four MAP-specific antigens
(AhpC, Gsd, p12, mpa), selected for their immunogenic potential.
This study was launched to assess the
safety,
tolerability, and immunogenicity of these vaccines in patients with
active
Crohn’s disease. It represents a
novel therapeutic vaccination strategy
targeting a suspected infectious agent and, if successful, could pave the way
for a new approach to Crohn’s disease management.
Can a vaccine really calm Crohn’s?
Twenty-eight adults with mild to moderate
Crohn’s disease were enrolled and randomly assigned into five groups. Two
groups received a single dose of ChAdOx2 HAV, two other groups received a
single dose of MVA HAV, and a fifth group received a prime-boost regimen
with ChAdOx2 HAV followed by an MVA HAV booster, eight weeks apart. No
participant was on immunosuppressive therapy to preserve the integrity of the
immune evaluation.
Vaccines were administered intramuscularly, and
patients were followed for 12 to 32 weeks depending on their group. The
vaccines were very well tolerated. A total of 196 adverse events were
reported—most were mild (76%) or moderate (23%) and resolved within seven days.
Only three severe adverse events (grade 3) were observed, with no established
link to vaccination. Two serious adverse events (SAEs) were reported, both
deemed unrelated to the vaccines.
From an immunological standpoint, the
vaccination induced a T-cell response marked by activation of
interferon-gamma-producing cells. This response was especially strong in the
prime-boost group, where the median cell count rose from 53 to 1,335 after the
booster, stabilizing at 544 after two months—suggesting durable immune
activation. All four vaccine antigens contributed equally to this response.
Clinically, improvement was observed with a
drop in the CDAI score, especially in the high-dose ChAdOx2 and prime-boost
groups. In the latter, six out of eight patients achieved a score below 150,
corresponding to clinical remission. Similarly, the endoscopic SES-CD
score, which measures mucosal inflammation, decreased by more than 50% in four
patients, indicating visible mucosal healing.
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Toward a new target in Crohn’s disease?
Crohn’s disease is a chronic inflammatory bowel
disorder, currently managed mainly through immunomodulation. Despite
therapeutic progress, a significant number of patients experience partial or
complete treatment failure, and the exact causes of the disease remain elusive.
One persistent hypothesis is the possible involvement of Mycobacterium avium
subspecies paratuberculosis, an intracellular pathogen suspected of
triggering an abnormal immune response in certain individuals.
Faced with this challenge, this study aimed to test
for the first time in humans a therapeutic vaccine targeting MAP, assessing
the safety, tolerability, and immunogenicity of the ChAdOx2 HAV and MVA HAV
vectors in patients with active Crohn’s disease. It represents an innovative
approach, focusing on modulating anti-MAP immunity rather than merely
suppressing inflammation.
The results show that both vaccines have a
satisfactory safety profile, with good tolerability and strong activation of
antigen-specific T cells in the prime-boost group. Clinically, signs of
improvement were seen in both the CDAI and endoscopic markers, even though the
study was not designed to formally evaluate therapeutic efficacy.
These findings represent a key milestone
in the development of a therapeutic vaccine for Crohn’s disease. They warrant
further investigation in larger cohorts, incorporating clinical,
microbiological, and immunological efficacy endpoints. This approach could
potentially lead to a paradigm shift in treatment, by targeting an
underlying cause of the disease.
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