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Characterization of the bovine salivary gland transcriptome associated with Mycobacterium avium subsp.
Sanjay Mallikarjunappa1,2, Mounir Adnane1,3, Paul Cormican1
1Animal & Bioscience Research Department, Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Co. Meath, Ireland.
Background:
Mycobacterium avium subsp. paratuberculosis (MAP), the etiologic agent of Johne's disease is spread between cattle via the fecal-oral route, yet the functional changes in the salivary gland associated with infection remain uncharacterized. In this study, we hypothesized that experimental challenge with MAP would induce stable changes in gene expression patterns in the salivary gland that may shed light on the mucosal immune response as well as the regional variation in immune capacity of this extensive gland. Holstein-Friesian cattle were euthanized 33 months' post oral challenge with MAP strain CIT003 and both the parotid and mandibular salivary glands were collected from healthy control (n = 5) and MAP exposed cattle (n = 5) for histopathological and transcriptomic analysis.
Results:
A total of 205, 21, 61, and 135 genes were significantly differentially expressed between control and MAP exposed cattle in dorsal mandibular (M1), ventral mandibular (M2), dorsal parotid (P1) and ventral parotid salivary glands (P2), respectively. Expression profiles varied between the structurally divergent parotid and mandibular gland sections which was also reflected in the enriched biological pathways identified. Changes in gene expression associated with MAP exposure were detected with significantly elevated expression of BoLA DR-ALPHA, BOLA-DRB3 and complement factors in MAP exposed cattle. In contrast, reduced expression of genes such as polymeric immunoglobin receptor (PIGR), TNFSF13, and the antimicrobial genes lactoferrin (LF) and lactoperoxidase (LPO) was detected in MAP exposed animals.
Conclusions:
This first analysis of the transcriptomic profile of salivary glands in cattle adds an important layer to our understanding of salivary gland immune function. Transcriptomic changes associated with MAP exposure have been identified including reduced LF and LPO. These critical antimicrobial and immunoregulatory proteins are known to be secreted into saliva and their downregulation may contribute to disease susceptibility. Future work will focus on the validation of their expression levels in saliva from additional cattle of known infection status as a potential strategy to augment disease diagnosis.
Insights
Mycobacterium avium subsp. paratuberculosis (MAP) infection alters cattle salivary gland gene expression, reducing key antimicrobial proteins like lactoferrin (LF) and lactoperoxidase (LPO). This downregulation may increase susceptibility to Johne
Area of Science:
- Veterinary Immunology
- Bovine Infectious Diseases
- Salivary Gland Biology
Background:
- Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), spreads via the fecal-oral route in cattle.
- Functional changes in cattle salivary glands following MAP infection are not well understood.
- This study investigates gene expression in salivary glands post-MAP challenge.
Purpose of the Study:
- To characterize gene expression patterns in cattle salivary glands after experimental MAP challenge.
- To explore potential regional variations in immune capacity within the salivary glands.
- To identify molecular mechanisms underlying salivary gland response to MAP infection.
Main Methods:
- Holstein-Friesian cattle were orally challenged with MAP strain CIT003.
- Salivary glands (parotid and mandibular) were collected 33 months post-challenge from control and MAP-exposed cattle.
- Histopathological and transcriptomic analyses were performed on collected tissues.
Main Results:
- Significant differential gene expression was observed in all analyzed salivary gland sections (mandibular and parotid).
- MAP exposure led to increased expression of bovine leukocyte antigen (BoLA) DR-ALPHA, BOLA-DRB3, and complement factors.
- Reduced expression of polymeric immunoglobulin receptor (PIGR), TNFSF13, lactoferrin (LF), and lactoperoxidase (LPO) was noted in MAP-exposed cattle.
Conclusions:
- This study provides the first transcriptomic analysis of cattle salivary glands, revealing insights into their immune function.
- Downregulation of critical antimicrobial proteins LF and LPO in salivary glands may contribute to Johne's disease susceptibility.
- Future research will validate salivary LF and LPO levels for potential use in disease diagnosis.
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