Conjugate vaccines consisting of the capsular polysaccharide (PS) of Haemophilus influenzae type b (Hib) covalently linked to carrier proteins, unlike pure PS, are immunogenic in infants and have significantly reduced Hib infections in the United States, but require multiple doses to induce protective anti-PS Ab titers. Hib-meningococcal outer membrane protein complex (OMPC) conjugate vaccine, however, elicits protective anti-PS Ab titers after one dose. We found that OMPC and Hib-OMPC engaged human Toll-like receptor 2 (TLR2) expressed in human embryonic kidney (HEK) cells, inducing IL-8 production, and engaged mouse TLR2 on bone marrow-derived dendritic cells, inducing TNF release. Hib conjugated to the carrier proteins CRM197 and tetanus toxoid did not engage TLR2 on HEK or dendritic cells. Engagement of TLR2 by Hib-OMPC was MyD88 dependent, as Hib-OMPC-induced TNF production was ablated in MyD88 knockout (KO) mice. Hib-OMPC was significantly less immunogenic in TLR2 KO mice, inducing lower Hib PS IgG and IgM titers compared with those in wild-type mice. Splenocytes from OMPC-immunized TLR2 KO mice also produced significantly less IL-6 and TNF-α than those from wild-type mice. Hib-OMPC is unique among glycoconjugate vaccines by engaging TLR2, and the ability of Hib-OMPC to elicit protective levels of Abs after one dose may be related to TLR2-mediated induction and regulation of cytokines produced by T cells and macrophages in addition to the peptide/MHC II-dependent recruitment of T cell help commonly afforded by carrier proteins. TLR2 engagement by an adjuvant or carrier protein may be a useful strategy for augmentation of the anti-PS Ab response induced by glycoconjugate vaccines.

Over the last two decades, there has been an increasing awareness regarding the potential impact of indoor air pollution on human health. People working in an indoor environment often experience symptoms such as eye, nose, and throat irritation. Investigations into these complaints have ascribed the effects, in part, to compounds emitted from building materials, cleaning/consumer products, and indoor chemistry. One suspect indoor air contaminant that has been identified is the dicarbonyl 4-oxopentanal (4-OPA). 4-OPA is generated through the ozonolysis of squalene and several high-volume production compounds that are commonly found indoors. Following preliminary workplace sampling that identified the presence of 4-OPA, these studies examined the inflammatory and allergic responses to 4-OPA following both dermal and pulmonary exposure using a murine model. 4-OPA was tested in a combined local lymph node assay and identified to be an irritant and sensitizer. A Th1-mediated hypersensitivity response was supported by a positive response in the mouse ear swelling test. Pulmonary exposure to 4-OPA caused a significant elevation in nonspecific airway hyperreactivity, increased numbers of lung-associated lymphocytes and neutrophils, and increased interferon-γ production by lung-associated lymph nodes. These results suggest that both dermal and pulmonary exposure to 4-OPA may elicit irritant and allergic responses and may help to explain some of the adverse health effects associated with poor indoor air quality.

Immune evasion is required for Mycobacterium tuberculosis to survive in the face of robust adaptive CD4؉ T-cell responses. We have previously shown that M. tuberculosis can indirectly inhibit CD4 ؉ T cells by suppressing the major histocompatibility complex class II antigen-presenting cell function of macrophages. This study was undertaken to determine if M. tuberculosis could directly inhibit CD4 ؉ T-cell activation. Murine CD4 ؉ T cells were purified from spleens by negative immunoaffinity selection followed by flow sorting. Purified CD4 ؉ T cells were activated for 16 to 48 h with CD3 and CD28 monoclonal antibodies in the presence or absence of M. tuberculosis and its subcellular fractions. CD4؉ T-cell activation was measured by interleukin 2 production, proliferation, and expression of activation markers, all of which were decreased in the presence of M. tuberculosis. Fractionation identified that M. tuberculosis cell wall glycolipids, specifically, phosphatidylinositol mannoside and mannosecapped lipoarabinomannan, were potent inhibitors. Glycolipid-mediated inhibition was not dependent on Toll-like receptor signaling and could be bypassed through stimulation with phorbol 12-myristate 13-acetate and ionomycin. ZAP-70 phosphorylation was decreased in the presence of M. tuberculosis glycolipids, indicating that M. tuberculosis glycolipids directly inhibited CD4؉ T-cell activation by interfering with proximal T-cell-receptor signaling.Aerosolized Mycobacterium tuberculosis infects alveolar and lung parenchymal macrophages, where it replicates unrestrained in the face of innate responses until T-cell immunity controls its growth. Despite robust activation of innate and adaptive immunity, M. tuberculosis survives and persists as a latent infection (15, 18). CD4 ϩ T cells have a central role in controlling M. tuberculosis during acute and latent infections (53). Animal studies have shown that depletion or absence of CD4 ϩ T cells during primary infection results in unchecked M. tuberculosis growth in the lung and decreased survival (37,38,41). Depletion of CD4 ϩ T cells during latent infection also worsens disease and survival (46). In humans, loss of CD4 ϩ T cells from progressive human immunodeficiency virus infection is directly responsible for the high rates of tuberculosis in human immunodeficiency virus-infected persons (48).Much is known about how M. tuberculosis manipulates macrophages for its survival (19,29,44). However, the way in which M. tuberculosis interferes with adaptive T-cell immunity is not well understood. Our recent studies have demonstrated that M. tuberculosis can modulate CD4 ϩ T-cell function both indirectly and directly. M. tuberculosis, through Toll-like receptor 2 (TLR-2), inhibits gamma-interferon-regulated genes that result in decreased major histocompatibility complex class II (MHC-II) antigen processing by macrophages for effector and memory CD4 ϩ T cells (22,23,40,43). M. tuberculosis can also induce increased adhesion to fibronectin through ␣ 5 ␤ 1 integrin on CD4 ϩ T cells (45)...