Relationship between Amphipathic ß Structures in the ß1 Domain of Apolipoprotein B and the Properties of the Secreted Lipoprotein Particles in McA-RH7777 Cells.

Our previous studies demonstrated that the first 1000 amino acid residues (the ßα1 domain) of human apolipoprotein (apo) B-100, termed apoB:1000, are required for the initiation of lipoprotein assembly and the formation of a monodisperse stable phospholipid (PL)-rich particle. The objectives of this study were (a) to assess the effects on the properties of apoB truncates undergoing sequential inclusion of the amphipathic ß strands in the 700 N-terminal residues of the ß1 domain of apoB-100 and (b) to identify the subdomain in the ß1 domain that is required for the formation of a microsomal triglyceride transfer protein (MTP)-dependent triacylglycerol (TAG)-rich apoB-containing particle. Characterization of particles secreted by stable transformants of McA-RH7777 cells demonstrated the following. (1) The presence of amphipathic ß strands in the 200 N-terminal residues of the ß1 domain resulted in the secretion of apoB truncates (apoB:1050 to apoB:1200) as both lipidated and lipid-poor particles. (2) Inclusion of residues 300-700 of the ß1 domain led to the secretion of apoB:1300, apoB:1400, apoB:1500, and apoB:1700 predominantly as lipidated particles. (3) Particles containing residues 1050-1500 were all rich in PL. (4) There was a marked increase in the lipid loading capacity and TAG content of apoB:1700-containing particles. (5) Only the level of secretion of apoB:1700 was markedly diminished by MTP inhibitor BMS-197636. These results suggest that apoB:1700 marks the threshold for the formation of a TAG-rich particle and support the concept that MTP participates in apoB assembly and secretion at the stage where particles undergo a transition from PL-rich to TAG-rich.

Investigating the epidemiology of repeat Chlamydia trachomatis detection after treatment by using C. trachomatis OmpA genotyping.

Repeat Chlamydia trachomatis detection frequently occurs within months after C. trachomatis infection treatment. The origins of such infection (persistence versus reinfection from untreated or new partners) are varied and difficult to determine. C. trachomatis strains can be differentiated by sequencing the ompA gene encoding the outer membrane protein A (OmpA). We used OmpA genotyping to investigate the epidemiology of repeat C. trachomatis detection after treatment in C. trachomatis-infected subjects seen at a sexually transmitted diseases clinic. Subjects were enrolled, tested for C. trachomatis, treated with azithromycin, and scheduled for a 6-month follow-up for repeat C. trachomatis testing. OmpA genotyping was performed on C. trachomatis-positive urogenital specimens obtained from patients at enrollment and follow-up. The enrollment visit OmpA genotypes for C. trachomatis were determined for 162 subjects (92% female, 94% African American). C. trachomatis was detected at follow-up in 39 subjects (24%). The OmpA genotype distribution at enrollment did not differ in those with versus those without repeat C. trachomatis detection. Of the 35 subjects with C. trachomatis strains genotyped at enrollment and follow-up, 7 (20%) had the same ompA sequence at both visits, while 28 (80%) had discordant sequences. A new sexual partner was reported more often in subjects with discordant C. trachomatis strains than in those with concordant strains (13 [46%] versus 1 [14%]; P = 0.195). Half of the subjects with discordant C. trachomatis strains who reported sexual activity since treatment denied a new sexual partner; 62% of these subjects reported that their partner was treated. Our study demonstrates that most repeat C. trachomatis detections after treatment were new infections with a different C. trachomatis strain rather than reinfection with the same strain. OmpA genotyping can be a useful tool in understanding the origins of repeat C. trachomatis detection after treatment.

T cell phenotypes in women with Chlamydia trachomatis infection and influence of treatment on phenotype distributions.

T cell phenotypes involved in the immune response to Chlamydia trachomatis (CT) have not been fully elucidated in humans. We evaluated differences in T cell phenotypes between CT-infected women and CT-seronegative controls and investigated changes in T cell phenotype distributions after CT treatment and their association with reinfection. We found a higher expression of T cell activation markers (CD38+HLA-DR+), T helper type 1 (Th1)- and Th2-associated effector phenotypes (CXCR3+CCR5+ and CCR4+, respectively), and T cell homing marker (CCR7) for both CD4+ and CD8+ T cells in CT-infected women. At follow-up after treatment of infected women, there were a lower proportion of CD4+ and CD8+ T cells expressing these markers. These findings suggest a dynamic interplay of CD4+ and CD8+ T cells in CT infection, and once the infection is treated, these cell markers return to basal expression levels. In women without reinfection, a significantly higher proportion of CD8+ T cells co-expressing CXCR3 with CCR5 or CCR4 at follow-up was detected compared to women with reinfection, suggesting they might play some role in adaptive immunity. Our study elucidated changes in T cell phenotypes during CT infection and after treatment, broadening our understanding of adaptive immune mechanisms in human CT infections.

Distinct peripheral vs mucosal T-cell phenotypes in chlamydia-infected women.

PROBLEM: Differences in circulating (peripheral) and mucosal T-cell phenotypes in chlamydia-infected women remain largely unknown. METHOD OF STUDY: Thirteen paired mononuclear cell specimens from blood and cervicovaginal lavages collected from chlamydia-infected women were stained and analyzed using ten-color cell surface flow cytometry for T-cell distribution, activation status, homing, and T helper (Th)-associated chemokine receptors (CKRs). RESULTS: A higher proportion of genital mucosal T-cells were activated (CD38+ HLA-DR+ ) and expressed CCR5 and Th1-associated CKR CXCR3+ CCR5+ compared to peripheral T-cells, but a lower proportion of mucosal T-cells expressed homing CKR CCR7, Th-2 associated CKR CCR4, and CXCR3+ CCR4+ for both T-cell subsets. CONCLUSION: T-cell phenotypes differed in the peripheral vs genital mucosa compartments in chlamydia-infected women. As chlamydia infects mucosal epithelial cells, the finding of a higher frequency of activated T-cells and Th-1 phenotypes in the mucosa likely reflects an adaptive immune response to infection.

The Predominant CD4+ Th1 Cytokine Elicited to Chlamydia trachomatis Infection in Women Is Tumor Necrosis Factor Alpha and Not Interferon Gamma.

Chlamydia trachomatis infection is the most prevalent bacterial sexually transmitted infection and can cause significant reproductive morbidity in women. There is insufficient knowledge of C. trachomatis-specific immune responses in humans, which could be important in guiding vaccine development efforts. In contrast, murine models have clearly demonstrated the essential role of T helper type 1 (Th1) cells, especially interferon gamma (IFN-γ)-producing CD4+ T cells, in protective immunity to chlamydia. To determine the frequency and magnitude of Th1 cytokine responses elicited to C. trachomatis infection in humans, we stimulated peripheral blood mononuclear cells from 90 chlamydia-infected women with C. trachomatis elementary bodies, Pgp3, and major outer membrane protein and measured IFN-γ-, tumor necrosis factor alpha (TNF-α)-, and interleukin-2 (IL-2)-producing CD4+ and CD8+ T-cell responses using intracellular cytokine staining. The majority of chlamydia-infected women elicited CD4+ TNF-α responses, with frequency and magnitude varying significantly depending on the C. trachomatis antigen used. CD4+ IFN-γ and IL-2 responses occurred infrequently, as did production of any of the three cytokines by CD8+ T cells. About one-third of TNF-α-producing CD4+ T cells coproduced IFN-γ or IL-2. In summary, the predominant Th1 cytokine response elicited to C. trachomatis infection in women was a CD4+ TNF-α response, not CD4+ IFN-γ, and a subset of the CD4+ TNF-α-positive cells produced a second Th1 cytokine.

Chlamydia trachomatis infection in African American women who exclusively have sex with women.

Little is known about whether Chlamydia trachomatis can be sexually transmitted between women or how often it occurs in women who have sex with women (WSW). We investigated Chlamydia trachomatis prevalence and serum Chlamydia trachomatis-specific antibody responses among African American WSW who reported a lifetime history of sex only with women (exclusive WSW) (n = 21) vs. an age-matched group of women reporting sex with women and men (WSWM) (n = 42). Participants completed a survey, underwent a pelvic examination in which a cervical swab was collected for Chlamydia trachomatis nucleic acid amplification testing (NAAT), and had serum tested for anti-Chlamydia trachomatis IgG1 and IgG3 antibodies using a Chlamydia trachomatis elementary body-based ELISA. No exclusive WSW had a positive Chlamydia trachomatis NAAT vs. 5 (11.9%) WSWM having a positive Chlamydia trachomatis NAAT (p = 0.16). Compared with WSWM, WSW were significantly less likely to be Chlamydia trachomatis seropositive (7 [33.3%] vs. 29 [69%], p = 0.007). Among Chlamydia trachomatis seropositive women, all were seropositive by IgG1, and the magnitude of Chlamydia trachomatis-specific IgG1 responses did not differ in Chlamydia trachomatis-seropositive WSW vs. WSWM. In conclusion, Chlamydia trachomatis seropositivity was relatively common in exclusive African American WSW, though significantly less common than in African American WSWM.

Lower sexually transmissible infection prevalence among lifetime exclusive women who have sex with women compared with women who have sex with women and men.

UNLABELLED: Background Sexually transmissible infection (STI) history, prevalence and seroprevalence among lifetime exclusive women who have sex with women (WSW) and an age-matched group of women who have sex with women and men (WSWM) was evaluated. METHODS: Participants completed a study questionnaire and had genital specimens and sera collected for STI testing. RESULTS: Twenty-one lifetime exclusive WSW and 42 WSWM were included. WSWM were more likely to report a history of prior STIs and be seropositive for chlamydia and HSV-2. Prevalent STIs were less common among WSW. CONCLUSIONS: While lifetime exclusive WSW are at risk of contracting STIs, WSWM are disproportionally affected. Healthcare providers should consider routine STI screening among WSW.