Biomedical subjects

C V Paya

Publications and source records attributed to C V Paya.

At least 55 records · Page 3Linked to original sources

PubMed1999

Human herpesvirus 6 seronegativity before transplantation predicts the occurrence of fungal infection in liver transplant recipients.

BACKGROUND: Invasive fungal infection has a major impact on the morbidity and mortality of liver transplant recipients. Human herpesvirus (HHV)-6 infection after transplantation is associated with an immunosuppressive state and the development of cytomegalovirus disease. Because cytomegalovirus infection is a risk factor for invasive fungal infection after transplantation, we have examined whether HHV-6 and fungal infection are associated after transplantation. METHODS: Pretransplantation sera from 247 consecutive liver transplant recipients were analyzed for IgG to HHV-6. Thirty-three (13%) HHV-6-seronegative recipients were identified. Six of 33 (18%) seronegative recipients experienced fungal infection as compared with 15 of 214 (7%) seropositive recipients (P=0.034). RESULTS: In a univariate analysis of risk factors for fungal infection, pretransplantation seronegativity to HHV-6 (P=0.034), intraoperative cryoprecipitate requirements greater than the 75th percentile (P=0.035), reoperation (P=0.005), biliary stricturing postoperatively (P=0.046), and gastrointestinal or vascular complications postoperatively (P=0.030) were identified as significant risk factors. Moreover, in pairwise multivariate analysis, pretransplantation HHV-6 seronegativity remained a significant variable even in the presence of each of the other variables. CONCLUSIONS: These results suggest that HHV-6 seronegativity before transplantation is a valuable clinical marker that identifies patients at risk for developing fungal infection after transplantation.

Disease-Free Survival↗

PubMed1999

Signal transduction pathways triggered by the FcepsilonRIIb receptor (CD23) in human monocytes lead to nuclear factor-kappaB activation.

BACKGROUND: Alveolar macrophages play a key role in the initiation of the inflammatory reaction of allergic asthma. Alveolar macrophages and peripheral blood monocytes are activated when IgE/allergen immune complexes bind to the CD23 receptor, which leads to the production of inflammatory cytokines. OBJECTIVE: We sought to investigate the molecular mechanisms regulating this early inflammatory response. We have focused on the study of the signal transduction pathways triggered by CD23 in human monocytes and the promonocytic cell line U937. METHODS: CD23 was cross-linked in human monocytes and U937 cells with IgE immune complexes. Surface expression of CD23 was determined by FACS analysis. Transcription factor activation and gene transcription were studied by gel-shift assays and Northern blot analysis, respectively. IkappaBalpha phosphorylation and degradation was analyzed by Western blot. RESULTS: Nuclear factor (NF)-kappaB is the main transcription factor involved in the gene activation that follows CD23 cross-linking in monocytes. CD23-induced NF-kappaB is a heterodimer composed of p65/p50 subunits. NF-kappaB nuclear translocation is secondary to the phosphorylation and subsequent degradation of the NF-kappaB inhibitory molecule IkappaBalpha. Tyrosine kinase-dependent, and not protein kinase C-dependent, pathways mediate CD23-triggered NF-kappaB activation but do not participate in the direct phosphorylation of IkappaBalpha. IkappaBalpha degradation and NF-kappaB nuclear translocation correlate with transcriptional activation of the inflammatory cytokines TNF-alpha and IL-1beta. CONCLUSIONS: NF-kappaB is the main transcription factor involved in the signal transduction pathway of CD23 in monocytes.

Cell Line↗

PubMed1999

Prevention of infections in solid organ transplant recipients.

Solid organ transplantation has become an important therapeutic option for multiple chronic diseases. With the advent of newer and potent immunosuppressive regimens, graft survival has improved, but at the expense of an increased risk for the development of infections secondary to bacterial, fungal, viral and parasitic pathogens. Prevention of such infectious complications with effective, well tolerated, and cost-effective anti-microbials would be ideal to improve the outcome of transplanted patients. However, the emergence of multi-drug resistant pathogens, medication toxicity and drug-drug interactions need to be carefully evaluated. This review summarizes the most relevant data pertaining to our current understanding of infection prevention for solid organ transplant recipients. Specific recommendations are given for the prevention of each group of microorganisms and types of solid organ transplant.

Anti-Infective Agents↗

PubMed1999

Ikappakappa mediates NF-kappaB activation in human immunodeficiency virus-infected cells.

Human monocytes and macrophages are persistent reservoirs of human immunodeficiency virus (HIV) type-1. Persistent HIV infection of these cells results in increased levels of NF-kappaB in the nucleus secondary to increased IkappaBalpha, IkappaBbeta, and IkappaBepsilon degradation, a mechanism postulated to regulate viral persistence. To characterize the molecular mechanisms regulating HIV-mediated degradation of IkappaB, we have sought to identify the regulatory domains of IkappaBalpha targeted by HIV infection. Using monocytic cells stably expressing different transdominant molecules of IkappaBalpha, we determined that persistent HIV infection of these cells targets the NH2 but not the COOH terminus of IkappaBalpha. Further analysis demonstrated that phosphorylation at S32 and S36 is necessary for HIV-dependent IkappaBalpha degradation and NF-kappaB activation. Of the putative N-terminal IkappaBalpha kinases, we demonstrated that the Ikappakappa complex, but not p90(rsk), is activated by HIV infection and mediates HIV-dependent NF-kappaB activation. Analysis of viral replication in cells that constitutively express IkappaBalpha negative transdominant molecules demonstrated a lack of correlation between virus-induced NF-kappaB (p65/p50) nuclear translocation and degree of viral persistence in human monocytes.

Binding Sites↗

PubMed1999

Cryptosporidium parvum induces apoptosis in biliary epithelia by a Fas/Fas ligand-dependent mechanism.

Although the clinical features of sclerosing cholangitis from opportunistic infections of the biliary tree in patients with acquired immunodeficiency syndrome (AIDS) are well known, the mechanisms by which associated pathogens, such as Cryptosporidium parvum, cause disease are obscure. Using an in vitro model of biliary cryptosporidiosis, we observed that C. parvum induces apoptosis in cultured human biliary epithelia. Both caspase protease inhibitors and neutralizing antibodies to either Fas receptor (Fas) and Fas ligand (FasL) inhibited this process; neutralizing antibodies to other apoptotic cytokines [interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta (TGF-beta)] had no effect. C. parvum stimulated FasL membrane surface translocation, increased both FasL and Fas protein expression in infected biliary epithelia, and induced a marked increase of soluble FasL (but not IL-1beta, TNF-alpha, and TGF-beta) in supernatants from infected cells. When a coculture model is used in which infected and uninfected cell populations were physically separated by a semipermeable membrane, both uninfected biliary epithelia and uninfected Fas-sensitive Jurkat cells (but not a Fas-resistant Jurkat cell line) underwent apoptosis when cocultured with infected biliary epithelia. Moreover, both a neutralizing antibody to FasL and a metalloprotease inhibitor blocked the apoptosis in uninfected cocultured cells. Activation of caspase activity was also observed in uninfected cocultured biliary epithelia. The data suggest that C. parvum induces apoptosis in biliary epithelia by a Fas/FasL-dependent mechanism involving both autocrine and paracrine pathways. These observations may be relevant to both the pathogenesis and therapy of the cholangitis seen in AIDS patients with biliary cryptosporidiosis.

Animals↗

PubMed1999

Human herpesvirus 6.

Human herpesvirus (HHV) 6 is a beta-herpes, DNA virus. This virus shows closest homology with cytomegalovirus and HHV-7. Infection usually occurs in infants 6 to 24 months of age, and primary infection may result in roseola. HHV-6 infection in infants is the commonest cause of fever-induced seizures. Infection in adults is seen primarily in immunocompromised hosts with solid organ transplants or in those with human immunodeficiency virus infection. The virus is capable of pronounced interaction in vitro with cytomegalovirus and human immunodeficiency virus and induces immunosuppression and apoptosis. The importance of these interactions in vivo necessitates further investigation. HHV-6 infection may contribute to the pathogenesis of multiple sclerosis. HHV-6 may be diagnosed by viral culture, serology, or polymerase chain reaction.

Herpesviridae Infections↗

PubMed1999

Indirect effects of CMV in the solid organ transplant patient.

Recent research has led to the identification of risk factors for cytomegalovirus (CMV) infection and disease in the solid organ transplant patient, leading to increasingly effective prophylactic regimens. These strategies have led to a decreased incidence of CMV infection and disease and a decrease in what has become known as the "direct" effects of CMV. Accumulating evidence, however, suggests that there are several "indirect" effects of CMV infection, which significantly impact management and outcome of transplant recipients. Some of the postulated indirect effects of CMV infection in this population include various opportunistic infections and graft rejection, as well as the attendant increased cost and resource utilization by transplant programs. An evaluation of such indirect effects may allow us to improve our care of the transplant population while reducing cost and resource use.

Cytomegalovirus Infections↗

PubMed1998

In vivo analysis of Fas/FasL interactions in HIV-infected patients.

Recent insights into the pharmacological control of HIV replication and the molecular mechanisms of peripheral T cells homeostasis allowed us to investigate in vivo the mechanisms mediating T cell depletion in HIV-infected patients. Before the initiation of highly active antiretroviral therapy (HAART), a high degree of lymphoid tissue apoptosis is present, which is reduced upon HAART initiation (P < 0.001) and directly correlates with reduction of viral load and increases of peripheral T lymphocytes (P < 0.01). Because Fas/FasL interactions play a key role in peripheral T lymphocyte homeostasis, we investigated the susceptibility to Fas-mediated apoptosis in peripheral T lymphocytes and of FasL expression in lymphoid tissue before and during HAART. High levels of Fas-susceptibility found in peripheral CD4 T lymphocytes before HAART were significantly reduced after HAART, coinciding with decreases in viral load (P = 0.018) and increases in peripheral CD4 T lymphocyte counts (P < 0.01). However, the increased FasL expression in the lymphoid tissue of HIV-infected individuals was not reduced after HAART. These results demonstrate that lymphoid tissue apoptosis directly correlates with viral load and peripheral T lymphocyte numbers, and suggest that HIV-induced susceptibility to Fas-dependent apoptosis may play a key role in the regulation of T cell homeostasis in HIV-infected individuals.

Anti-HIV Agents↗

PubMed1998

Clinical significance of viral load in the diagnosis of cytomegalovirus disease after liver transplantation.

In a cohort of 43 liver transplant recipients who did not receive antiviral prophylaxis, qualitative and quantitative polymerase chain reactions (PCRs) from peripheral blood were prospectively compared to determine their value in the diagnosis of established cytomegalovirus (CMV) disease and for the early detection of CMV replication as a marker for preemptive antiviral therapy. Using a cutoff of 7000 copies of CMV DNA per sample, the specificity and positive predictive values of qualitative PCR for the diagnosis of established CMV disease increased from 33% to 89% and from 54% to 82%, respectively, without reducing the 100% sensitivity and negative predictive value. By contrast, quantification of viral load provided no additional advantage to qualitative PCR for the early diagnosis of CMV infection before development of disease.

Blood↗

PubMed1998

The expression of Fas Ligand by macrophages and its upregulation by human immunodeficiency virus infection.

Fas/Fas Ligand (FasL) interactions play a significant role in peripheral T lymphocyte homeostasis and in certain pathological states characterized by T cell depletion. In this study, we demonstrate that antigen-presenting cells such as monocyte-derived human macrophages (MDM) but not monocyte-derived dendritic cells express basal levels of FasL. HIV infection of MDM increases FasL protein expression independent of posttranslational mechanisms, thus highlighting the virus-induced transcriptional upregulation of FasL. The in vitro relevance of these observations is confirmed in human lymphoid tissue. FasL protein expression is constitutive and restricted to tissue macrophages and not dendritic cells. Moreover, a significant increase in macrophage-associated FasL is observed in lymphoid tissue from HIV (+) individuals (P < 0.001), which is further supported by increased levels of FasL mRNA using in situ hybridization. The degree of FasL protein expression in vivo correlates with the degree of tissue apoptosis (r = 0.761, P < 0. 001), which is significantly increased in tissue from HIV-infected patients (P < 0.001). These results identify human tissue macrophages as a relevant source for FasL expression in vitro and in vivo and highlight the potential role of FasL expression in the immunopathogenesis of HIV infection.

Apoptosis↗

PubMed1998

CD4 regulates susceptibility to Fas ligand- and tumor necrosis factor-mediated apoptosis.

The current knowledge of CD4 function is limited to its role as a necessary coreceptor in TCR-initiated signaling. We have investigated whether CD4 regulates additional T cell functions. Using human primary resting CD4+ T cells, we demonstrate that CD4 activation is sufficient to induce lymphocyte death. Immediately after CD4 cross-linking, CD4+ T cells are rendered susceptible to apoptosis mediated by TNF or FasL. This, together with the concomitant induction of FasL within the same population, results in significant CD4+ T cell death in vitro. The CD4-dependent induction of susceptibility to apoptosis that is mediated by TNF or FasL is protein synthesis independent but phosphorylation dependent. After CD4 activation, PKC regulates susceptibility to apoptosis mediated by FasL but not the induction of susceptibility to TNF-dependent apoptosis. Moreover, significant differences between CD3 and CD4 activation were observed with regards to the kinetics of induction of CD4+ T cell susceptibility to FasL- and TNF-mediated apoptosis. Altogether, these results provide a model with which to study the molecular mechanisms regulating lymphocyte survival after CD4 activation, and highlight the potential role of CD4 in controlling lymphocyte apoptosis under physiological conditions or in disease states such as HIV infection.

Apoptosis↗

PubMed1998

Transcriptional regulation of the human FasL promoter-enhancer region.

The human FasL enhancer region was cloned and functionally characterized in transformed and primary T cells. Within the 2.3 kilobase pairs of the FasL untranslated region, the distal 3' 300-base pair portion contains a single transcription initiation site and confers basal and inducible transcriptional activity. Stimuli that increase [Ca2+]i such as CD3 cross-linking or ionomycin, but not activation of protein kinase C, were found to induce FasL enhancer transcription in a cyclosporin-sensitive manner. Moreover, calcineurin and NFAT, but not AP1, were identified as necessary and sufficient effectors in driving FasL transcription through an NFAT cis-acting motif (GGAAA). Additional modes of T cell activation such as CD4 cross-linking were also found to induce NFAT binding to the FasL enhancer region and to functionally transactivate its transcription. These results indicate that the induction of FasL gene transcription in T cells after CD3 or CD4 activation is selectively mediated by calcineurin and NFAT.

Base Sequence↗

PubMed1998

Infectious complications following renal transplantation.

Despite significant advancements in renal transplantation, infectious disease complications remain an important cause of morbidity and mortality in the transplant recipient. The prevention and treatment of these infections remain a major challenge.

Bacterial Infections↗

PubMed1998

Epstein-Barr virus-induced T cell lymphoma in solid organ transplant recipients.

Epstein-Barr virus (EBV) infection in transplant recipients can lead to lymphomas termed posttransplantation lymphoproliferative disorders (PTLDs). Most PTLDs are malignancies of B lymphocytes and are linked to EBV infection, but the rare T lymphocyte PTLDs have been inconsistently linked to EBV infection. Although the B lymphocyte is the main host cell of EBV, it has been suggested that T lymphocytes may also become infected by EBV. A review of EBV-induced PTLDs at our institution identified one of 61 cases that was restricted to T lymphocytes. Of 36 cases of T cell PTLD identified through a literature review, 21 were investigated for the presence of EBV, and eight (38%) were documented to be EBV-induced. We compared the features of EBV-positive and EBV-negative T cell PTLDs and concluded that cases of EBV-positive T cell PTLD have some distinctive clinical features.

Heart Transplantation↗

PubMed1998

Evaluation of PCR primers for early diagnosis of cytomegalovirus infection following liver transplantation.

The availability of microbiologic methods that detect early replication of cytomegalovirus (CMV) posttransplantation will enhance the process of initiating preemptive antiviral therapy prior to the appearance of CMV disease. Using PCR techniques we sought to determine which region of the CMV genome present in peripheral blood leukocytes (PBLs) or serum provides the highest sensitivity for the detection of CMV posttransplantation. Blood samples were prospectively collected weekly for at least 8 weeks from a cohort of 21 consecutive liver transplant recipients not receiving anti-CMV prophylaxis. Results of PCR assays were correlated with recovery of CMV in cell cultures and histopathological findings from biopsy specimens of infected organs to assess clinical symptomatic infection. Of 148 specimens, primer pairs directed to the HindIII-X fragment region of CMV detected target DNA with a 94% sensitivity, compared to an 87% sensitivity with primer pairs directed to EcoRI fragment D, 32% sensitivity with primer pairs directed to the immediate-early antigen 1 gene (IEA1 gene), and 20% sensitivity with primer pairs directed to the major immediate-early (MIE) gene. The performance characteristics in terms of the sensitivity of primers for amplifying CMV DNA associated with symptomatic infection ranged from 100% (HindIII-X) to 20% (MIE gene); however, specificity was inversely related (HindIII-X, 45%; MIE gene, 91%) to primers directed to these gene targets. When HindIII-X and EcoRI-D primer sets were used, CMV DNA from PBLs was a more sensitive target than CMV DNA from serum for the early detection of symptomatic CMV infection (17 versus 12 days). Importantly, CMV DNA was not detected in five patients with no evidence of this viral infection. In conclusion, primers directed to the HindIII-X fragment region were the most optimal for the early detection of CMV DNA in PBLs and sera from symptomatic liver transplant recipients.

Antibodies, Viral↗

PubMed1998

Detection and semiquantitative analysis of human herpesvirus 8 DNA in specimens from patients with Kaposi's sarcoma.

Kaposi's sarcoma (KS) is the most common neoplasm in patients with AIDS. Epidemiologic evidence and the recent identification of herpesvirus-like DNA sequences in patients with KS have suggested a role for viral agents in the etiopathogenesis of this disease. It is unclear if these sequences are present in all types of KS and if the copy number of these sequences has a correlation with disease severity (staging). In order to clarify these issues, we retrospectively analyzed, by PCR and Southern blotting, formalin-fixed, paraffin-embedded biopsy specimens from 12 patients previously diagnosed with KS by histopathologic examination of these specimens between the years of 1977 and 1996. We also analyzed tissue samples from these patients taken from dermal sites without KS lesions and control tissues from healthy subjects. Of the 12 patients, 6 had classic KS, 5 had AIDS-associated KS, and 1 had the endemic type of KS. We tested the specimens for other herpesviruses, including cytomegalovirus, human herpesvirus 6 (HHV-6), HHV-7, HHV-8, and Epstein-Barr virus. Of 20 biopsy specimens from patients previously diagnosed with KS, 19 were positive for HHV-8 sequences (95%), while PCR for the DNAs of other herpesvirus agents was negative. Uninvolved tissue from these patients and control tissue from healthy subjects gave negative results for all viruses. Semiquantitative analysis of Southern blots showed higher levels of HHV-8 DNA in those patients with multicentric and visceral involvement than in those patients with localized involvement. In addition, in patients with localized skin disease, the nodular stage had higher levels of HHV-8 DNA than the patch or plaque stages. Our data confirmed that HHV-8 is involved in the etiopathogenesis of all types of KS and that there is a correlation between HHV-8 DNA load and the severity and staging of this disease.

AIDS-Related Opportunistic Infections↗

PubMed1998

Is cytomegalovirus infection related to mycophenolate mofetil after kidney transplantation? A case-control study.

Three multicenter studies have shown that the addition of mycophenolate mofetil (MMF) to an immunosuppressive regime consisting of cyclosporin A (CSA) and prednisone (PRED) decreases the incidence of acute rejection episodes when compared with azathioprine (AZA) or placebo (1-3). In those patients receiving 3 g/d of MMF, the highest dose used in the studies, there was a trend towards an increased incidence of cytomegaloviral sepsis (CMV). We postulated therefore that MMF may represent an independent risk factor for the development of CMV infection in patients receiving renal allografts and MMF at our institution. Having altered the triple drug regime from CSA, AZA (2-2.5 mg/kg/d) and PRED to CSA, MMF (2 g/d) and PRED in July 1995, we elected to study all patients undergoing kidney transplantation for the 33-month period January 1994-September 1996, by undertaking a case control analysis to determine independent risk factors for the development of CMV infection, as defined by CMV viremia or tissue-invasive CMV. Three CMV disease-free control patients were matched to each case, these patients having been randomly selected from the entire pool of patients in the observation period. There were 31 CMV case patients and 102 control patients. Univariate analysis indicated that gender, a concomitant pancreas transplant, acute rejection and CMV seropositivity in the donor were risk factors. However, multivariate analysis indicated that only acute rejection and donor CMV seropositivity were independently linked (p < 0.05) to CMV disease in this sample. Specifically, the odds ratio (OR) for CMV disease between MMF and AZA was 1.0 (95% confidence interval (CI): 0.46-2.18). Therefore, in this case control study we find no evidence that MMF at a dose of 2 g/d is an independent risk factor for primary CMV viremia or tissue invasion in renal allograft recipients.

Adult↗

PubMed1997

Prophylaxis of cytomegalovirus infection in liver transplantation: a randomized trial comparing a combination of ganciclovir and acyclovir to acyclovir. NIDDK Liver Transplantation Database.

BACKGROUND: The optimal prophylactic regimen to prevent cytomegalovirus (CMV) infection and disease in orthotopic liver-transplant patients remains to be established. We tested whether a combination of intravenous ganciclovir (GCV) followed by high dosages of oral acyclovir (ACV) for 4 months provided a higher degree of protection from CMV than oral ACV alone. METHODS: One hundred sixty-seven liver-transplant recipients were randomized to receive 120 days of antiviral treatment starting at the time of transplantation consisting of either ACV 800 mg orally four times daily (n=84) or 14 days of GCV 5 mg/kg intravenously every 12 hr followed by oral ACV 800 mg four times daily (n=83). Prospective laboratory and clinical surveillance was performed to determine primary endpoints (onset of CMV infection and CMV disease) and secondary endpoints (rates of fungal and bacterial infection, allograft rejection, and survival after transplantation). One-year event rates are presented as cumulative percentages. RESULTS: During the first year after transplantation, CMV infection developed in 57% of patients treated with ACV and in 37% of patients treated with GCV + ACV (P=0.001). CMV disease developed in 23% of patients treated with ACV and in 11% of patients treated with GCV + ACV (P=0.03). In seronegative recipients of allografts from CMV-seropositive donors (D+/R-), CMV disease developed in 58% of patients treated with ACV and in 25% of patients treated with GCV + ACV (P=0.04). In the D+/R- group, 54% of patients treated with ACV and 17% of patients treated with GCV + ACV developed infection with Candida albicans (P=0.05). CONCLUSIONS: Prophylaxis of CMV infection in liver-transplant patients with 14 days of intravenous GCV followed by high-dosage oral ACV is more effective than high-dosage oral ACV alone at reducing CMV infection and disease, even for patients in the D+/R- CMV serological group.

Acyclovir↗