Background:
Microbial translocation contributes to inflammation in HIV-infected humans and has been associated with increased mortality and morbidity in individuals treated with antiretrovirals. Thus, there is interest in understanding the mechanisms underlying microbial translocation. To characterize translocating bacterial populations, we isolated and identified translocating bacteria from chronically SIV-infected macaques and characterized their genomes and proteomes. Proteome profiling identified a cytosine-specific DNA methyltransferase as being enriched in translocating taxa. We hypothesized that inhibiting this enzyme with the cytidine analog 5-Aza-2’-deoxycytidine would more strongly inhibit the growth of translocating bacteria compared to non-translocating bacteria.
Methods:
Liver, mesenteric lymph node, and spleen samples were taken during necropsy from twenty chronically SIV- or SHIV-infected RM. Tissue samples were homogenized and plated under aerobic and anaerobic conditions. Isolates were identified using MALDI-TOF and/or 16S rDNA sequencing. Bacterial proteomes were analyzed by tandem mass spectrometry and genomics by next generation sequencing. 5-Aza-2’-deoxycytidine mediated growth inhibition was determined in vitro via longitudinal OD600 readings. Area under the curve was used to determine inhibitory effects between species, Welch’s t test or Mann-Whitney test used to compare results depending on normal distribution.
Results:
Thirty-six translocating bacterial taxa were identified from 4 bacterial phyla. Translocating bacteria showed different proteome features from non-translocating bacteria with 47.21% of proteins identified as being unique. Top hits included cytosine-specific DNA methyltransferases and copper homeostasis protein CutC, which were found in five of the eight translocating bacterial species. 5-Aza-2’-deoxycytidine preferentially inhibited the growth of translocating bacterial species compared to non-translocating species.
Conclusions:
Microbial translocation does not seem to be stochastic and unique taxa of translocating bacteria commonly express DNA methylation enzymes. Inhibition of these enzymes in vitro results in significant reduction of growth in these taxa. Blocking activity of these enzymes in vivo may offer unique treatment modalities to reduce microbial translocation and improve the prognosis of HIV-infected individuals.