RNA-seq analysis reveals the role of Omp16 during Brucella infected RAW264.7 cells

Brucellosis is an endemic zoonotic infectious disease in the majority
developing country that causes huge economic losses. As immunogenic and
protective antigens at the surface of Brucella spp, outer membrance
proteins (Omps) are particularly attractive for developing vaccine and
could have more relevant role in host-pathogen interactions. Omp16, a
homologue to peptidoglycan-associated lipoproteins (pals), is essential
for Brucella survival in vitro. At present, the functions of Omp16 has
been poorly studies. Here, the gene expression profile of RAW264.7 cells
infected with Brucella. suis vaccine strain 2 (B. suis S2) and Omp16
mutant was analyzed by RNA-seq to investigate the cellular response
immediately after Brucella entry. The RNA-sequence analysis revealed that
a total 303 genes were significantly regulated by B. suis S2 24 h
postinfection. Of these, 273 differential expressed genes (DEGs) were
up-regulated and 30 DEGs were down-regulated. These DEGs was mainly
involved in innate immune signaling pathways, including pattern
recognition receptors (PRRs), proinflammatory cytokines and chemokines by
KEGG analysis. In Omp16 mutant infected cells, the expression of 52 total
cells genes were significantly upregulated and that of 9 total cells genes
were down-regulated compared to B. suis S2 infected RAW264.7 cells. The
KEGG pathway analysis showed that several upregulated genes were
proinflammatory cytokines and chemokines, such as interleukin-6 (IL-6),
IL-11, IL-12β, CCL2 (C-C motif chemokine), and CCL22. All together, we
clearly demonstrate that Brucella Omp16 can alter macrophage
immune-related pathways to increase proinflammatory cytokines and
chemokines to against Brucella infection, which provide insights into
illuminating the Brucella pathogenic strategies.