Cross-talk between CD31 and the signaling lymphocytic activation molecule-associated protein during interferon- gamma production against Mycobacterium tuberculosis

Effective host defense against tuberculosis requires Th1 cytokine responses. We studied the regulation of interferon (IFN)- gamma production during tuberculosis by investigating the role of CD31, a receptor that attenuates T cell receptor signals. After antigen stimulation, CD3(+)CD31(+) blood lymphocytes decreased in healthy donors and in tuberculosis patients with robust Th1 responses to Mycobacterium tuberculosis and IFN- gamma was secreted only by CD31(-) T cells. In contrast, in patients with weak Th1 cytokine responses to M. tuberculosis, the level of CD3(+)CD31(+) lymphocytes was increased and IFN- gamma production was low. Furthermore, the inverse relationship between CD31 expression and IFN- gamma production was in contrast to signaling lymphocytic activation molecule (SLAM) expression, an IFN- gamma inducer in tuberculosis. Interestingly, CD31 bound to SLAM-associated protein (SAP), an IFN- gamma inhibitor in tuberculosis, and when CD31 and SAP were coexpressed in lymphocytes, their association inhibited the IFN- gamma response to M. tuberculosis. Thus, CD31, when binding to SAP, interferes with Th1 responses, suggesting that CD31 has a key regulatory role in the signaling pathway(s) leading to the IFN- gamma response to M. tuberculosis.     

Host immune response to Chlamydia pneumoniae heat shock protein 60 is associated with asthma.

Chlamydia pneumoniae infection has been associated with asthma. It has also been suggested that heat shock protein 60 (Hsp60) belonging to a class of highly conserved proteins may play a role in the pathogenesis of chlamydial infections. The purpose was to study whether the host immune response to C. pneumoniae Hsp60 is associated with asthma and decreased pulmonary function. An enzyme immunoassay was used to measure immunoglobulin-(Ig)A and IgG antibodies against recombinant C. pneumoniae Hsp60 and human Hsp60 in a study group consisting of 24 cases of recently symptomatic asthma and 62 nonasthmatic controls. A strong (r=0.50) and significant (p<0.001) correlation was observed between C. pneumoniae and human Hsp60 IgA antibodies, but only C. pneumoniae Hsp60 IgA antibodies were significantly associated with asthma (p = 0.02). Pulmonary function, as measured by forced expiratory volume in one second, also inversely correlated (r = -0.23, p = 0.04) with the quantity of C. pneumoniae Hsp60 IgA antibodies, suggesting an association with the severity of pulmonary obstruction. By showing an association of Chlamydia pneumoniae heat shock protein 60 immunoglobulin A antibodies with asthma, the results support the hypothesis of an association between Chlamydia pneumoniae infection and asthma and support the need for further investigations on the role of heat shock protein 60 in the pathogenesis of asthma.     

Heparan sulfate-like glycosaminoglycan is a cellular receptor for Chlamydia pneumoniae.

Chlamydia pneumoniae is an important human intracellular pathogen; however, the pathogenesis of C. pneumoniae infection is poorly understood, and the bacterial adherence mechanism to host cells is unknown. This study examined the role of glycosaminoglycans (GAGs) in the adhesion of C. pneumoniae to eukaryotic cells. Heparin and heparan sulfate were found to inhibit the attachment of C. pneumoniae to human epithelial cells. Reduction in infectivity resulted from the binding of heparin to the organism. Enzymatic removal of heparan sulfate moieties from the host cell surface led to a marked decrease in C. pneumoniae infectivity. Mutant CHO cell lines that were defective in heparan sulfate biosynthesis were less susceptible to C. pneumoniae infection than was the wild-type cell line. However, preincubation of the GAG-deficient CHO cells with exogenous heparin greatly increased infectivity.     

Identification and characterization of differentially expressed mRNAs in HIV type 1-infected human T cells

We used a novel differential display (DD) technique to identify host factors involved in virus replication, pathogenesis, and host response in HIV-1-infected T cells. Thirteen cDNA fragments differentially expressed in HIV-1NL4-3-infected MT-4 cells prior to the occurrence of specific apoptotic cell death were sequenced and identified. Two of seven elevated genes were identical to HIV-1 sequences and the other five were MIP-1alpha, ACTE-III, CD11c, arginase I, and CCR5. The six downregulated genes included prothymosin-a, Jaw-1, proteasome subunit XAPC7, splicing factor 9G8, GA17 protein, and an unknown mRNA. Northern blot and RT-PCR analyses confirmed the altered gene expressions in MT-4 cells as well as in another T cell line, MOLT-4. We also revealed that the amount of MIP-1alpha in culture supernatant of HIV-1-infected cells was increased by more than 15-fold relative to control cells, and the expression of its receptor CCR5 was cooperatively upregulated on the surface of these cells. Furthermore, the upregulation of CD11c after HIV-1 infection was slightly inhibited by blocking the MIP-1alpha-mediated signal transduction. These results indicate that genes altered on HIV-1 infection may be mutually organized and play an important role in HIV-1-induced pathogenesis.     

Chlamydia pneumoniae (C. pneumoniae) infection upregulates atherosclerosis-related gene expression in human umbilical vein endothelial cells (HUVECs)

There is accumulating evidence that supports a role of infection in atherosclerosis, with possible mechanism by injuring to the endothelium and inducing an autoimmune response to heat shock proteins (HSPs). In this study, a cDNA array, containing 588 human cardiovascular genes, was utilized to analyze the gene expression profile of Chlamydia pneumoniae (C. pneumoniae) infected human umbilical vein endothelial cells (HUVECs). After 48h of C. pneumoniae infection, the HUVECs were harvested and subjected to immunofluorescent staining, electron microscopy, cDNA array hybridization, RT-PCR, and immunoblotting. This study found a panel of human host genes that were upregulated by C. pneumoniae. The majority of these genes were related to complex lipid metabolism, adhesion receptors, hormones, hormone receptors, and a metalloproteinase that may contribute to atherosclerosis in vivo. Representatives of upregulated gene products, i.e., heat shock protein 60 (HSP60), macrophage scavenger receptor, cytochrome P450, and VEGF165R were immunofluorescently detected in HUVECs, with their greater expression induced by C. pneumoniae infection. These findings supported the opinion that C. pneumoniae might contribute to atherosclerotic development in vivo.     

Chlamydia pneumoniae infections in asthma: clinical implications

Chlamydia pneumoniae is an intracellular pathogen that has been suggested to play a role in the pathology of asthma. However, so far none of the studies have provided clear evidence for a causative role of C. pneumoniae infections in asthma, although there is little doubt that chronic C. pneumoniae infection does aggravate asthma and should be treated. The diagnosis of C. pneumoniae infection is still a matter of concern for it is dependent on trained skilled personnel and can vary significantly between different diagnostic laboratories. This fact is also one of the major problems encountered when comparing epidemiological studies investigating the possible role of C. pneumoniae infections and their impact on the pathogenesis of other diseases. With regard to therapy, long-term treatment with macrolides is the best available method to eradicate C. pneumoniae. Successful therapy for C. pneumoniae, however, can also be complicated by the high possibility of de novo infection as epidemiological studies have shown that the prevalence of antibodies to C. pneumoniae increases with age in all populations studied. In the northern hemisphere the prevalence of C. pneumoniae is also affected by seasonal conditions. It is too early to draw any conclusions from the equatorial belt countries. The available data on C. pneumoniae in tropical countries indicate a much faster infection rate during early adulthood with 100% serological prevalence at an age greater than 25 years. This data, if confirmed, would argue against C. pneumoniae causing asthma since the asthma prevalence in those countries does not increase in a parallel pattern. An alternative interpretation of most studies could be that the increased rate of C. pneumoniae infections in patients with asthma results from a modified susceptibility towards the microorganism, due to yet unknown changes of the host cell's physiology. It should be kept in mind that increased prevalence of C. pneumoniae infection is not restricted to asthma. Further studies are needed to understand the role of C. pneumoniae, especially of chronic infection, in the pathogenesis of inflammatory diseases with a specific focus on the effect that the microorganism triggers in the infected host cell. Only when we understand what C. pneumoniae does to its host cell will we be able to judge its impact on the overall status of an affected patient, and this knowledge will help us to develop a successful therapy.     

Persistent infection with Chlamydia pneumoniae following acute respiratory illness.

Chlamydia pneumoniae is emerging as a significant cause of respiratory disease, including pneumonia and bronchitis, in humans. In this recently completed study of infection due to C. pneumoniae in patients presenting with pneumonia to SUNY Health Science Center at Brooklyn, we identified two individuals for whom cultures were positive on multiple occasions over a 1-year period. To determine the frequency of persistent respiratory infection with C. pneumoniae, follow-up specimens were obtained from nine individuals with culture-documented C. pneumoniae infection. Five of these individuals had persistent infection: four had a flulike illness characterized by pharyngitis, and one had bronchitis with prominent bronchospasm. All five individuals appeared to have acute C. pneumoniae infection as determined by results of serologic tests (titers of IgM antibody for all individuals were greater than or equal to 1:16). For three patients, cultures remained positive for 11 months despite therapy with 10- to 21-day courses of tetracycline or doxycycline. These observations suggest that persistent infection with C. pneumoniae may follow acute infection and may persist for many months. Infection with C. pneumoniae may be very difficult to eradicate with use of currently available antibiotics even if there is a clinical response to therapy.     

Combination of HIV-1-specific CD4 Th1 cell responses and IgG2 antibodies is the best predictor for persistence of long-term nonprogression

BACKGROUND: Strong T cell and antibody responses to human immunodeficiency virus (HIV), low virus production, and some genetic traits have been individually associated with nonprogression of HIV infection, but the best correlate with protection against disease progression remains unknown. METHODS: We prospectively followed 66 untreated long-term nonprogressors and analyzed relationships between HIV-1-specific CD4 T helper (Th) 1 and CD8 T cell responses and HIV-1-specific antibodies, HIV-1 RNA and proviral DNA loads, host genes, and CD4 Th1 cell counts at entry into the study and 4 years later. RESULTS: HIV-1 p24-specific CD4 Th1 cell proliferation, interferon (IFN)- gamma production, and IFN- gamma -producing cell frequencies at entry significantly and negatively correlated with HIV-1 RNA and proviral DNA loads and were independent of CD4 Th1 cell counts and host genes. HIV-1 Gag-specific IFN- gamma -producing CD8 T cell frequencies correlated with HIV-1 proviral DNA loads but not with RNA loads. Only high frequencies of HIV-1 p24-specific CD4 Th1 cells combined with HIV-1 gp41-specific IgG2 antibodies significantly predicted persistence of high CD4 Th1 cell counts. CONCLUSION: HIV-1-specific CD4 Th1 responses combined with IgG2 antibodies and IFN- gamma -producing CD4 Th1 cells are better predictors of long-term nonprogression than are virus parameters, host genes, or HIV-1-specific CD4 Th1 or CD8 T cell proliferation.     

Acute alcohol intoxication suppresses the interleukin 23 response to Klebsiella pneumoniae infection

BACKGROUND: Bacterial pneumonia is a widely recognized infection in the alcohol-abusing patient. Interleukin 23 (IL-23) is a recently described cytokine critical for IL-17 induction and host survival during Klebsiella pneumoniae infection, a pulmonary pathogen commonly seen in alcoholics. We investigated the effect of acute alcohol intoxication on the IL-23 response to this infection. METHODS: Male C57BL/6 mice were given an intraperitoneal injection of ethanol (3.0 g/kg) or phosphate-buffered saline (PBS) 30 minutes before infection. Alveolar macrophages (AM) were cultured with bacteria in ethanol (0, 50, and 100 mM) to determine alcohol's effect on AM IL-23 expression, the bioactivity of which was determined by splenocyte IL-17 inducing activity. The role of IL-10 in alcohol-mediated suppression of AM IL-23 p19 mRNA expression was assessed using wild-type (WT) and IL-10 knock-out (KO) mice. Efficacy of AM pretreatment with interferon gamma (IFN-gamma) on IL-23 expression before ethanol exposure and infection was evaluated. RESULTS: In vivo, acute intoxication suppresses the lung and bronchoalveolar lavage cell IL-23 response to pathogen. This effect was confirmed in vitro as ethanol dose-dependently inhibits AM IL-23 during infection. Acute intoxication increases lung and BAL cell IL-10 mRNA expression 2 hours after in vivo infection and, in vitro, recombinant IL-10 inhibits AM IL-23 expression. However, alcohol impairs IL-23 similarly in AM harvested from both WT and IL-10 KO mice. Interferon gamma pretreatment strongly inhibits AM IL-23 production in both the presence and absence of alcohol. CONCLUSIONS: Acute alcohol intoxication inhibits the pulmonary IL-23 response to K. pneumoniae infection both in vivo and in vitro, an effect independent of IL-10 induction. Interferon gamma priming antagonizes IL-23 and is, therefore, not likely to be a useful adjuvant therapy in restoring IL-23/IL-17 responses during infection and intoxication.     

Cellular transcriptional profiling in influenza A virus-infected lung epithelial cells: the role of the nonstructural NS1 protein in the evasion of the host innate defense and its potential contribution to pandemic influenza

The NS1 protein of influenza A virus contributes to viral pathogenesis, primarily by enabling the virus to disarm the host cell type IFN defense system. We examined the downstream effects of NS1 protein expression during influenza A virus infection on global cellular mRNA levels by measuring expression of over 13,000 cellular genes in response to infection with wild-type and mutant viruses in human lung epithelial cells. Influenza A/PR/8/34 virus infection resulted in a significant induction of genes involved in the IFN pathway. Deletion of the viral NS1 gene increased the number and magnitude of expression of cellular genes implicated in the IFN, NF-kappaB, and other antiviral pathways. Interestingly, different IFN-induced genes showed different sensitivities to NS1-mediated inhibition of their expression. A recombinant virus with a C-terminal deletion in its NS1 gene induced an intermediate cellular mRNA expression pattern between wild-type and NS1 knockout viruses. Most significantly, a virus containing the 1918 pandemic NS1 gene was more efficient at blocking the expression of IFN-regulated genes than its parental influenza A/WSN/33 virus. Taken together, our results suggest that the cellular response to influenza A virus infection in human lung cells is significantly influenced by the sequence of the NS1 gene, demonstrating the importance of the NS1 protein in regulating the host cell response triggered by virus infection.