Transcriptomic blood responses to mycobacteria in a BCG challenge model. Bos taurus

Cattle were vaccinated at week 0 with the live attenuated M. bovis BCG SSI vaccine strain; some animals remain as non-vaccinated controls. After eight weeks animals were challenged intranodally with 108 BCG Tokyo cfu. Lymph nodes were harvested at week 11 and bacterial load in lymph nodes evaluated. Some BCG vaccinates had bacterial loads similar to those found in non-vaccinated animals (not-protected) and some animals had lower bacterial loads (protected) than non-vaccinated animals. Immune responses to mycobacteria were monitored in vitro by stimulation of whole blood with medium, purified protein derivative from M. bovis (PPD-B) or live BCG Tokyo longitudinally. Blood samples from 6 BCG-protected, 6 BCG-not-protected and 6 not-vaccinated. Challenged cattle stimulated with mycobacterial antigens or not were used to prepare RNA for RNAseq analysis at weeks 0 (vaccination), 8 (challenge), 9, 10 and 11. The outcome of this project would help not only in the selection of vaccine candidates but would also inform on the formulation of novel vaccines/vaccination strategies. Overall design: Cattle were divided into three groups as follows: naïve, vaccinated protected and vaccinated not-protected. Blood samples that had been stimulated with PPD-B or BCG Tokyo (105 cfu/ml) or cultured with medium alone (negative control) from 6 animals of each group were used to prepare RNA for sequencing. Samples were obtained at four time points: week 0, week 8 (pre-challenge), week 9 (one week post-challenge) and week 10 (two weeks post-challenge); giving a total of 216. Three out of 216 mRNA samples did not pass the minimal QC criteria and were therefore removed.