Skip to Content

Immunohistochemistry (IHC) for MAP Detection 

What is Immunohistochemistry (IHC)?

Using antibody-based staining techniques, immunohistochemistry (IHC) is a potent laboratory technique for identifying particular antigens in tissue samples. IHC provides vital information about disease progression, localization, and tissue response in the context of Mycobacterium avium subspecies paratuberculosis (MAP) by allowing researchers and diagnosticians to directly visualize the pathogen within host tissues. 

IHC looks at the pathogen's precise location within tissues, as opposed to molecular or serological diagnostics, which find bacterial DNA or antibodies in fluids. This offers a distinct viewpoint on the cellular interactions between MAP and the host.

How Does It Work?

MAP-targeting antibodies are used in IHC in conjunction with enzymes like alkaline phosphatase or peroxidase. A chromogenic substrate is added after the antibody has bound to the MAP antigen found in tissue slices. This causes a color shift that makes it possible to see MAP under a microscope in the context of the tissue, where it frequently manifests as colored shapes or clusters in the sample.

Applications principales

  • Détection de MAP dans les tissus intestinaux et lymphatiques
  • Études sur la distribution tissulaire du pathogène
  • Outil de confirmation dans les cas subcliniques ou chroniques
  • Complément d’analyse aux méthodes de culture ou PCR

Avantages de l’IHC

  • Visualisation directe du pathogène dans les tissus
  • Localisation précise : permet de distinguer MAP dans le contexte histologique
  • Détection possible chez des animaux subcliniquement infectés
  • Méthode complémentaire utile en diagnostic différentiel

Advances in ELISA Development

Antigen Selection and Specificity

The selection of specific MAP antigens is key to improving ELISA accuracy. Research has focused on identifying unique antigenic proteins that reduce cross-reactivity. However, the shared epitopes among mycobacterial species make this a complex task.

Indigenous ELISA Kits

In India, the Central Institute for Research on Goats (CIRG) developed an indigenous ELISA using antigens derived from locally isolated MAP strains. Initially standardized from clinical MAP cases, including the "Tepes" strain used for Johnin production, these semi-purified protoplasmic antigens provided higher local strain specificity.

One of the fundamental methods in the field of MAP diagnostics is still immunohistochemistry. It may not have the throughput of PCR or ELISA, but it is particularly useful for histopathological analysis, research, and confirmation because it can show MAP inside tissues. IHC improves our knowledge of paratuberculosis and facilitates improved livestock population health management when paired with other diagnostic instruments.