Transfer RNA-derived fragment production in calves challenged with Mycoplasma bovis or co-infected with bovine viral diarrhea virus and Mycoplasma bovis in several tissues and blood

Authors: Goldkamp, Anna; ATCHISON, RANDY - Animal And Plant Health Inspection Service (APHIS); FALKENBERG, SHOLLIE - Auburn University; Dassanayake, Rohana; NIELL, JOHN - Retired ARS Employee; Casas, Eduardo

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2024
Publication Date: 11/8/2024
Citation: Goldkamp, A.K., Atchison, R.G., Falkenberg, S.M., Dassanayake, R.P., Niell, J.D., Casas, E. 2024. Transfer RNA-derived fragment production in calves challenged with Mycoplasma bovis or co-infected with bovine viral diarrhea virus and Mycoplasma bovis in several tissues and blood. Frontiers in Veterinary Science. https://doi.org/10.3389/fvets.2024.1463431.
DOI: https://doi.org/10.3389/fvets.2024.1463431

Interpretive Summary: Transfer RNA-derived fragments (tRFs) are small RNA molecules that are produced in cattle and can regulate gene expression in the animal, including genes involved in the immune system. The objective of this study was to identify if there are differences in tRF expression in immune related tissues or in circulating biological fluids (serum and blood) when an animal is challenged with Mycoplasma bovis or challenged with Mycoplasma bovis (M. bovis) and bovine viral diarrhea virus (BVDV). The calves in this study were assigned to three treatment groups: Control (no challenge), M. bovis (M. bovis challenge), and a dual group (challenged with M. bovis and BVDV). A total of 93 tRFs differed in expression due to the challenge. Immune system tissue had the greatest differences in tRF expression due to challenge and blood and serum had the fewest. tRFs in blood and serum are uncorrelated with immune response and are poor candidates for diagnosis based on expression. Infection with M. bovis and BVDV had a greater effect on tRF expression compared to M. bovis alone. Ten tRFs were associated with an increase in the abundance of virus and had differences in expression in the challenged groups. These tRFs can be considered putative candidates for additional studies to determine their use in diagnosis of infection by these pathogens.

Technical Abstract: Understanding the molecular mechanisms underlying immune response can allow informed decisions in drug or vaccine development, and aid in the identification of biomarkers to predict exposure or evaluate treatment efficacy. The objective of this study was to identify differentially expressed transfer RNA-derived fragments (tRFs) in calves challenged with Mycoplasma bovis (M. bovis) or co-infected with M. bovis and bovine viral diarrhea virus (BVDV). Serum, white blood cells (WBC), liver, mesenteric lymph node (MLN), tracheal-bronchial lymph node (TBLN), spleen, and thymus were collected from Control (n = 2), M. bovis (MB; n = 3), and co-infected (Dual; n =3) animals, and small RNAs extracted for sequencing. A total of 13,485 tRFs were predicted, consisting of 11,351 internal-tRFs (i-tRFs), 1,060 5' halves, 798 5' tRFs, 247 3' tRFs, and 29 3' halves. An average of 94% of reads were derived from 5' halves and/or 5' tRFs in serum, liver, WBC, TBLN, spleen, MLN, and thymus. The expression of tRFs in lymphatic tissues (MLN, TBLN, Thymus, Spleen) were highly correlated with each other (r = 0.82), but not with serum and WBC. A total of 93 differentially expressed tRFs were observed in all tissues and blood, where 59 of 93 differentially expressed tRFs were 5' halves. The lowest number of differentially expressed tRFs were found in WBC and serum. The highest number of differentially expressed tRFs were found in thymus and MLN, which may underlie mechanisms of lymphoid depletion previously observed in BVDV. The tRFs that were differentially expressed due to infection (MB or Dual) were identified and 28 out of 29 tRFs were downregulated in infected groups compared to control in liver, MLN, TBLN, spleen, thymus, and WBC. Co-infection seemed to have synergistic effects on a subset of tRFs, where 11 of 14 tRFs were upregulated in dual compared to control and MB groups in liver, MLN, TBLN, thymus and WBC. Ten differentially expressed tRFs were derived from tRNAGlyCCC and reports have suggested that dysregulated tRNAGlyCCC tRFs have a role in viral replication. Additional studies should be pursued to investigate the targets of differentially expressed tRFs induced by infection and those expressed through synergistic mechanisms.