Major Outer Membrane Protein Omp25 ofBrucella suisIs Involved in Inhibition of Tumor Necrosis Factor Alpha Production during Infection of Human Macrophages

Abstract

Brucella spp. can establish themselves and cause disease in humans and animals. The mechanisms by which Brucella spp. evade the antibacterial defenses of their host, however, remain largely unknown. We have previously reported that live brucellae failed to induce tumor necrosis factor alpha (TNF-␣) production upon human macrophage infection. This inhibition is associated with a nonidentified protein that is released into culture medium. Outer membrane proteins (OMPs) of gram-negative bacteria have been shown to modulate macrophage functions, including cytokine production. Thus, we have analyzed the effects of two major OMPs (Omp25 and Omp31) of Brucella suis 1330 (wild-type [WT] B. suis) on TNF-␣ production. For this purpose, omp25 and omp31 null mutants of B. suis (⌬omp25 B. suis and ⌬omp31 B. suis, respectively) were constructed and analyzed for the ability to activate human macrophages to secrete TNF-␣. We showed that, in contrast to WT B. suis or ⌬omp31 B. suis, ⌬omp25 B. suis induced TNF-␣ production when phagocytosed by human macrophages. The complementation of ⌬omp25 B. suis with WT omp25 (⌬omp25-omp25 B. suis mutant) significantly reversed this effect: ⌬omp25-omp25 B. suis-infected macrophages secreted significantly less TNF-␣ than did macrophages infected with the ⌬omp25 B. suis mutant. Furthermore, pretreatment of WT B. suis with an anti-Omp25 monoclonal antibody directed against an epitope exposed at the surface of the bacteria resulted in substancial TNF-␣ production during macrophage infection. These observations demonstrated that Omp25 of B. suis is involved in the negative regulation of TNF-␣ production upon infection of human macrophages.Members of the genus Brucella are gram-negative, facultatively intracellular bacteria that can induce chronic infections in humans. Following invasion of the reticuloendothelial system, the bacteria develop intracellularly within mononuclear phagocytes. Chronic infection generally results in the fixation of infected macrophages at specific locations within the body (spleen, brain, heart, bones), and the human disease is characterized by undulant fever, endocarditis, arthritis, and osteomyelitis (42). Brucellae are also pathogenic for animals, but the pathophysiology of the human infection differs in many respects from the illness induced in animals. In domestic ruminants, infection results mainly in abortion in females and orchitis in males (15) whereas in mice, infection resembles septicemia and does not become truly chronic (18). These observations therefore suggest a species-specific interaction of Brucella organisms with the immune systems of their different hosts. To survive and multiply within the host, one of the major strategies of pathogens is to affect the expression of cytokines, which is necessary for the normal protective function of the immune response (26).In previous papers (6, 7) we have reported that brucellae can adopt the following strategy. (i) In human monocytic phagocytes (but not in mouse macrophages), Brucella spp. impair the production o...

The two-component system BvrR/BvrS essential for Brucella abortus virulence regulates the expression of outer membrane proteins with counterparts in members of the Rhizobiaceae

“…suis Omp3a has been shown to be involved in the negative regulation of TNF-␣ production after infection of human macrophages, supporting a role for this protein in Brucella capability to survive within cells (31). Furthermore, we have found recently that bvrS mutants do not stimulate the generation of active forms of small GTPases of the Rho family on cell contact (32), indicating that this two-component system is also necessary for establishing an adequate cross talk with the host cell.…”

“…mAbs to the following Omps were used (17)(18)(19): Omp10 (A68͞07G11͞C10), Omp16 (A68͞08C03͞ G03), Omp19 (A76͞05C10͞A08, A76͞18B02͞D06), Omp25 (A18͞13D02͞F05, A19͞12B10͞F04, A59͞05F01͞C09, A70͞ 06B05͞A07, A76͞02C12͞C11, A68͞04B10͞F05, A68͞07D11͞ B03, A68͞28G06͞C07), Omp2b (Omp36) (A63͞08D08͞C07, A63͞05A07͞A08, A63͞03H02͞B01, A63͞11E05͞D11, A63͞ 13G02͞C04, A63͞04D11͞G01, A68͞25G05͞A05), and Omp1 (Omp89) (A53͞10B02͞A01). Anti-Omp25 mAbs A18͞13D02͞ F05, A19͞12B10͞F04, and A59͞05F01͞C09 recognize a linear epitope close to the amino-terminal section (amino acids [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. A mAb against the C͞Y epitope was conjugated with peroxidase (20), and was used for LPS detection.…”

Predominant T Helper 2 Immune Responses againstBartonella henselaein Naturally Infected Cats

“…Interestingly, the TNF-α expression in Cat A with the highest level of bacterial load was relatively lower than in the other cats, but Cat A had the highest levels of IL-4 mRNA expression. Following this possibility, outer membrane protein 25 secreted from Brucella suis showed a high sequence homology at amino acids levels to that of a 31-kDa protein (Pap31) of B. henselae, and was demonstrated to be a factor involved in the defect in TNF-α production (7,11).…”

DNA VACCINATION OF BISON TO BRUCELLAR ANTIGENS ELICITS ELEVATED ANTIBODY AND IFN-γ RESPONSES

“…The use of recombinant protein technology and monoclonal antibodies has shown that the major outer membrane proteins (OMPs) appear to be of limited use as vaccines against smooth B. abortus or B. melitensis infections (Cloeckaetr et al, 2002). Recently, how- (Edmonds et al, 2001(Edmonds et al, , 2002aJubier-Maurin et al, 2001). Pasquevich et al have shown that immunization with OMPs of recombinant Brucella species omp16 or omp19 induces protection against B. abortus infection (Pasquevich et al, 2009).…”