Enhanced intracellular replication of Salmonella enteritidis in HLA-B27-expressing human monocytic cells: dependency on glutamic acid at position 45 in the B pocket of HLA-B27.

Abstract

OBJECTIVE:

To reveal the cause of the impaired elimination of Salmonella enteritidis in HLA-B27-transfected human monocytic cells and to study whether the B pocket of HLA-B27 contributes to these modulatory effects.

METHODS:

Stable U937 cell transfectants expressing HLA-A2, B27, or different forms of B27 with amino acid substitutions in the B pocket were prepared. Mock-transfected cells were prepared using the antibiotic resistance vector (pSV2neo) alone. Cells were differentiated, infected with S enteritidis, and the number of live intracellular S enteritidis organisms was determined using the colony-forming unit method. To visualize intracellular S enteritidis, the bacteria were transformed with green fluorescent protein (GFP), and studied by confocal microscopy.

RESULTS:

Cells expressing wild-type HLA-B27 were more permissive of intracellular replication of S enteritidis compared with mock-transfected or A2-transfected controls. Cells expressing B27 with an altered B pocket composition having either 6 amino acid substitutions (B27.A2B; substitutions H9F, T24A, E45M, I66K, C67V, and K70H) or a single substitution (B27.E45M) were no longer permissive of S enteritidis replication. In contrast, cells expressing B27 with the single substitution of F for H at position 9 (B27.H9F) retained their permissiveness. Studies using GFP-transformed S enteritidis confirmed that the increase in the amount of intracellular bacteria in B27-expressing cells was due to replication of the bacteria.

CONCLUSION:

Our data indicate that HLA-B27 expression modulates the host-microbe interaction that results in an impaired capacity of monocytes to resist intracellular replication of S enteritidis. The phenotype is dependent on glutamic acid at position 45 in the B pocket and, thus, may be due to properties of the B27 heavy chain that are related to this residue. The ability of HLA-B27 to confer susceptibility to Salmonella-triggered reactive arthritis may occur, at least in part, through these modulatory effects.

• Authors: Markus A Penttinen, Kaisa M Heiskanen, Rajashree Mohapatra, Monica L DeLay, Robert A Colbert, Lea Sistonen, Kaisa Granfors
• Journal: Arthritis and rheumatism (Arthritis Rheum) Vol. 50 Issue 7 Pg. 2255-63 (Jul 2004) ISSN: 0004-3591 [Print] United States
• PMID: 15248225 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• HLA-B27 Antigen
• Histocompatibility Antigens Class I
• Luminescent Proteins
• Green Fluorescent Proteins
• Methionine

Topics

• Amino Acid Sequence
• Amino Acid Substitution
• Cell Line
• Cell Membrane (metabolism)
• Endoplasmic Reticulum (metabolism)
• Gene Transfer Techniques
• Green Fluorescent Proteins
• HLA-B27 Antigen (chemistry, genetics, metabolism)
• Histocompatibility Antigens Class I (genetics, metabolism)
• Humans
• Intracellular Membranes (microbiology)
• Luminescent Proteins (genetics)
• Methionine
• Monocytes (immunology, microbiology)
• Phenotype
• Protein Folding
• Salmonella Infections (microbiology)
• Salmonella enteritidis (growth & development)
• Time Factors
• Transfection