Modulation of antibody-forming cell and mitogen-driven lymphoproliferative responses by dietary nucleotides in mice

Several studies have demonstrated that dietary nucleotides play a role in maintaining T-cell dependent immunity. In this work, we investigated the effects of nucleotide supplementation of a nucleotide-free diet (NFD) on some immunity parameters in BALB/c mice. Twenty day old mice were maintained on diets for 30 days prior to use in experiments. The addition of nucleotide mixtures to NFD resulted in an increase in the response of hemolytic IgG-forming cells induced by previous immunization with sheep erythrocytes. When NFD was supplemented with single nucleotides, AMP, GMP, or UMP increased the IgG response, whereas CMP and IMP were without effect. GMP was the only nucleotide that increased the hemolytic IgM-forming cell response. Neither the contact hypersensitivity response to dinitrofluorobenzene nor the time of death after transplantation of a syngenic lymphoma was modified by nucleotide addition to NFD. The in vitro proliferative response of splenocytes to LPS was not affected by nucleotide supplementation of NFD, but the ConA-driven proliferative response was increased in mice fed NFD supplemented with nucleotide mixtures or with UMP. These data show that dietary mononucleotides stimulated at least some T-cell dependent immunity mechanisms. Moreover, these stimulatory effects may be obtained by supplementing a nucleotide-free diet with a mixture in which mononucleotides are at the same levels as in murine breast milk.

Relationship of virologic, immunologic, and clinical parameters in infants with vertically acquired human immunodeficiency virus type 1 infection

We have investigated the relationship among the HIV-1 biologic phenotype, replicative capacity of virus isolates, HIV-RNA copy number in plasma, p24 antigenemia, CD4+ T lymphocyte counts in peripheral blood, and the clinical status in a cohort of 13 HIV-infected children younger than 12 mo of age, born of HIV-1 seropositive mothers. Six out of 13 HIV-1 isolates from these patients were classified as rapid/high and seven as slow/low. We have found a significantly positive correlation between the replication rate of HIV isolates and their capacity to induce syncytia in vitro. Most of the serial HIV-1 isolates obtained from infants with AIDS had the rapid/high phenotype and induced syncytia, whereas only two out of 23 HIV-1 isolates obtained from infants without AIDS showed these properties. In sequential analysis of HIV-1 isolates from infants with AIDS, the presence of viral isolates with rapid/high and SI phenotype was associated with higher levels of HIV-1 RNA in plasma, CD4+ T cell depletion, and clinical progression. By contrast, infants whose viruses exhibited nonsyncytium-inducing phenotype throughout the follow-up showed lower levels of HIV RNA, stable CD4+ T cell counts, and mild symptomatic HIV infection. Our findings indicate that infants who carried viruses with more cytopathic biologic phenotype and who had higher viral RNA coy numbers in blood were more likely to have lower CD4+ T cell counts and more likely to have AIDS.

Characterization of tumorigenic sub-lines from a poorly tumorigenic human colon-adenocarcinoma cell line

The interaction of tumor cells with extracellular-matrix components is suspected to play an important role in tumorigenesis induction. The tumorigenicity of a poorly tumorigenic human colon-adenocarcinoma cell line (BCS-TC2) was induced by co-injection with Matrigel. A new cell sub-line, BCS-TC2.1, was isolated and established from these tumors. Implantation of these cells in nude mice in the absence of Matrigel-generated tumors which allowed the establishment of another tumorigenic cell sub-line, BCS-TC2.2. Matrigel and laminin, but not collagens, promote the tumorigenicity of BCS-TC2 cells, probably due to specific interactions of a pre-existing minor cell sub-population with laminin, which facilitate the initial growth of these cells in vivo. Cytogenetic analysis reveals that both sub-lines originate from the parental one, but a new marker in chromosome 9 is observed. These sub-lines present a lower degree of differentiation, as deduced from the lower CEA content, 5'-nucleotidase and alkaline-phosphatase activities. No variation is observed in the mRNA and protein expression of the 67-kDa laminin-binding protein. However, an increase in beta1 integrins and a parallel decrease in beta4 integrin were detected. Thus, the new sub-lines, compared to the parental cells, present karyotypic and phenotypic differences such as the expression of a distinctive integrin pattern. This system represents a useful model for understanding the development and progression of tumorigenicity in cancer cells.

Role of the C terminus of the interleukin 8 receptor in signal transduction and internalization

Interleukin 8 (IL-8) is a potent neutrophil chemoattractant and activator. Two IL-8 receptor subtypes, A and B, are expressed in neutrophils. In this work, we analyzed the role of the C terminus domain of the IL-8 receptor on the signal transduction and receptor internalization mechanisms. The IL-8 receptor A was tagged with an epitope corresponding to the monoclonal antibody 1D4 to monitor the localization of the IL-8 receptor. We demonstrated IL-8-dependent receptor internalization by monitoring the density of surface 125I-labeled IL-8 binding sites and by immunofluorescence microscopy. Truncation of the last 27 amino acids of the IL-8 receptor A severely impaired the IL-8-induced internalization of the receptor. Of importance was the observation that binding of IL-8 to receptors A and B triggered a dramatically faster rate of internalization of receptor B than receptor A, suggesting that the heterologous C termini among receptor subtypes modulate the rate of internalization of IL-8 receptors. However, substitution of the C terminus of the receptor subtype A for the C terminus of receptor B reduced the internalization rate of receptor A. Furthermore, we found that the rate of internalization of IL-8 receptor B triggered by IL-8 was faster than the one induced by the IL-8-related peptide, melanoma growth stimulatory activity. Studies with human neutrophils pretreated with 100 nM IL-8 for 5 min revealed a positive and a negative calcium response mediated by receptors A and B, respectively. In contrast, neutrophils pretreated with melanoma growth stimulatory activity showed positive calcium responses to both receptors A and B. These data suggest that the neutrophil responses mediated by IL-8 are modulated by the rate of internalization of receptors.

Resting energy expenditure before and after surgical resection of gut lesions in pediatric Crohn's disease

In pediatric Crohn's disease (CD), resection of gut lesions is necessary to remove stenoses and when frequent relapses occur despite nutritional support and medical treatment. After surgery, improved nutritional status and accelerated growth usually follow increased nutritional intake and lower doses of steroids. The aim of this study was to compare energy balance before and after surgery while nutritional intake and steroid therapy were unchanged. Eleven patients, aged 14.5 +/- 2.5 years and with mildly active CD, were explored 1 week before and 1 month after gut resection for stenosis (n = 7) and medical treatment failure (n = 4). Eleven matched children participated in the study as controls. Disease activity was assessed by the Pediatric Crohn's Disease Activity Index and serum orosomucoid concentration. Resting energy expenditure (REE) was measured by indirect calorimetry, and fat-free body mass (FFM) was measured by anthropometry. The patients' mean REE decreased from 46.6 +/- 10.5 kcal/kg FFM/day before surgery to 42.6 +/- 10.3 kcal/kg FFM/day after surgery, while the controls' mean REE was 39 +/- 7 kcal/kg FFM/day (analysis of variance, p = 0.02). After surgery, body weights were not significantly different, but the mean protein oxidation rate was reduced and arm muscle area was increased. Changes in REE per kilogram of FFM per day were not correlated with changes in orosomucoid serum concentrations (r2 = 0.35; p = 0.4). In conclusion, in children with mildly active CD, while nutritional intake and steroid therapy were maintained at preoperative levels, a significant decrease in REE and improved nitrogen utilisation were observed 1 month after resection of the CD gut lesion. This finding suggests better use of energy substrates when CD lesions are removed.

In situ management and molecular analysis of candidaemia related to a totally implantable vascular access in a cystic fibrosis patient

We describe a case of candidaemia in a paediatric cystic fibrosis (CF) patient with a totally implantable vascular access (TIVA). Serial quantitative blood cultures during therapy with amphotericin B delivered via the catheter suggested that the patient was responding to therapy. The TIVA was finally removed because of persistent fever, but its culture remained sterile. Randomly amplified polymorphic DNA (RAPD) analysis of Candida albicans from various anatomical sites showed that the patient's sputum was the most likely source of TIVA contamination. Investigation of TIVA-related candidaemia by molecular analysis could guide rational antifungal chemoprophylaxis of TIVA-related candidaemia.

[Sleeping position, prevention of sudden death syndrome and gastroesophageal reflux]

Based on results of epidemiological studies, dorsal or lateral sleeping positions are now recommanded in the prevention of sudden infant death syndrome (SIDS). This raises an ethical question about the attitude towards the ventral positioning therapy for gastroesophageal reflux (GOR). The consensus conference considers that the ventral position should only be recommanded in GOR when the benefit appears to outweigh the risk of SIDS that it induces. The conference proposes that for infants with simple uncomplicated reflux, sleeping in the prone position should not be introduced in the first line treatment. Prone positioning should be restricted to complicated cases resistant to dietary and medical measures.

Chronic effects of nitric oxide and prostaglandin inhibition on pressure diuresis and natriuresis in rats

The long-term interaction between nitric oxide (NO) and prostaglandins (PGs) in the pressure diuresis and natriuresis response has been studied. Experiments were performed in rats with chronic (8 weeks) inhibition of NO (NG-nitro L-arginine methyl Ester, L-NAME, 40 mg/kg/day) with or without simultaneous PGs synthesis blockade (indomethacin, 1 mg/kg/day). A time control group with no treatment was studied in parallel. At the end of this period, the animals were anesthetized and renal hemodynamics and excretion were studied at three levels of renal perfusion pressure (RPP; 100, 125 and 150 mm Hg). Renal blood flow, glomerular filtration rate, diuresis and natriuresis were lower at the three RPP levels in both L-NAME-treated groups than in the control or indomethacin-treated animals. Simultaneous administration of indomethacin plus L-NAME did not further modify the hemodynamic or excretory responses observed in the L-NAME-treated animals. These results show that chronic NO inhibition impairs the renal excretory response to changes in renal perfusion pressure, and simultaneous NO and prostaglandin synthesis inhibition does not reduce those responses further. It is concluded that, on a long-term basis, a preserved NO production, but not prostaglandin production, is critical for a normal pressure diuretic and natriuretic mechanism.

Pentoxifylline inhibits acute HIV-1 replication in human T cells by a mechanism not involving inhibition of tumour necrosis factor synthesis or nuclear factor-kappa B activation

OBJECTIVE AND DESIGN

To study the in vitro activity of pentoxifylline (PTX), which may be of benefit in AIDS, on cell proliferation, tumour necrosis factor (TNF)-alpha, interferon (IFN)-gamma (a type 1 cytokine) and interleukin (IL)-10 (a type 2 cytokine) production, viral replication and CD4+ depletion in acutely HIV-1-infected human T cells.

METHODS

T cells were stimulated with anti-CD3 antibody or phytohaemagglutinin (PHA) and infected with HIV-1 in presence or absence of PTX. Cell proliferation, CD4+ cell number, nuclear factor (NF)-kappa B activation, p24 antigen release or lymphokine content of the supernatants were evaluated by [3H]-thymidine incorporation, cytofluorimetry, electrophoretic mobility shift assays and specific enzyme-linked immunosorbent assay, respectively.

RESULTS

In HIV-1-infected T cells, PTX inhibited cell proliferation and p24 release and prevented CD4+ depletion associated with HIV replication. Moreover, PTX reduced TNF-alpha, IFN-gamma and IL-10 production and NF-kappa B activation. PTX inhibited with similar potency IFN-gamma, TNF-alpha and cell proliferation. However, the inhibition of p24 release and specially of IL-10 production required significantly lower doses of PTX. Exogenous addition of IL-2 or TNF-alpha in presence of PTX restore T-cell proliferation and NF-kappa B activation respectively, but did not affect p24 inhibition.

CONCLUSIONS

Our data suggest that the inhibitory effect of PTX on HIV replication cannot be satisfactorily explained by the inhibition of NF-kappa B or TNF-alpha. Moreover, PTX cannot be primarily considered as a TNF-alpha inhibitor and has several immunomodulatory and antiviral properties which could be of benefit against HIV-1 at various levels.

Quantification of low levels of human immunodeficiency virus (HIV) type 1 RNA in P24 antigen-negative, asymptomatic, HIV-positive patients by PCR

A nested PCR was used to quantify small numbers of human immunodeficiency virus (HIV) type 1 (HIV-1) RNA particles in the serum specimens of 26 p24 antigen-negative, asymptomatic, HIV-positive patients undergoing antiretroviral therapy. Fifteen patients received zidovudine (ZDV) and alpha interferon, and 11 patients received ZDV monotherapy. After PCR, the amounts of RNA were quantified by comparing the endpoint dilutions of serum samples with a standard curve with known amounts of viral particles. Before the beginning of the antiviral therapy, HIV-1 RNA was detected in 92% of the patients. After treatment, a fall in the number of viral particles was detected in patients receiving combination therapy (mean titers +/- standard errors of the means, 3,617 +/- 756 pretherapy versus 1,800 +/- 845 posttherapy; P < 0.05) and in patients receiving monotherapy (3,763 +/- 642 pretherapy versus 1,353 +/- 394 posttherapy; P < 0.05). Our results indicate that PCR with nested primers may be useful for assessing the changes in viremia in HIV-positive patients with low viral load undergoing antiviral therapy.