Human granulocytic ehrlichiosis--a clinical case in Scandinavia

A clinical case of human granulocytic ehrlichiosis in Scandinavia is presented. The patient developed high fever, myalgia, headache and dyspnoea. Doxycycline treatment resulted in a dramatic improvement. Laboratory confirmation included a fourfold change in anti-Ehrlichia equi IFA titre and a positive PCR confirmed by gene sequence analysis.

Expression and release of stable and active forms of murine granulocyte-macrophage colony-stimulating factor (mGM-CSF) targeted to different subcellular compartments

Cytokines have been used for several years as immunomodulators. However, one of the main drawbacks of systemically applied cytokines is their high toxicity. In addition, cytokines work in a paracrine form and frequently after cell-to-cell interaction. Therefore, a very restricted release of cytokines-in time and space-could be desired for most of their therapeutic applications. The murine granulocyte-macrophage colony-stimulating factor (mGM-CSF) is one of the most promising cytokine candidates for cancer immunotherapy and as an adjuvant of DNA vaccines. With the aim of improving the administration and release of cytokines in a very restricted area, we have designed vectors expressing the mGM-CSF cDNA with different localization signals. Using this strategy we have shown that cytokines can be expressed and targeted to different subcellular compartments (i.e. the cytoplasm, the endoplasmic reticulum and the nucleus), stored inside the cells and released after cell lysis as stable active proteins. Moreover, a plasma membrane targeted form of mGM-CSF displayed substantial amount of biological activity. These vectors could have potential applications in immunotherapy for tumours and DNA vaccination protocols.

Proximal promoter of the murine syndecan-1 gene is not sufficient for the developmental pattern of syndecan expression in B lineage cells

Syndecan-1 (CD138) is a cell membrane proteoglycan that binds extracellular matrix components and various growth factors. The role of syndecan-1 in the control of cell growth and morphology has been illustrated by its altered expression in hematological malignancies such as multiple myeloma as well as some solid tumors. It has been reported that the expression of syndecan-1 in cells of the B lineage is developmentally regulated such that pre-B cells and plasma cells express syndecan-1 while mature B cells do not. Thus, we investigated whether the proximal promoter region of the murine syndecan-1 promoter was able to confer the observed on-off-on expression of syndecan-1 in cells of the B lineage as they develop from pre-B cells to plasma cells. Experiments carried out using deletion mutants of the proximal promoter cloned upstream of the CAT reporter gene transfected into murine cell lines, representing the above stages of B-cell development, such as BA/F3 (pro-B cell), 70Z/3 (pre-B cell), 2PK3 (late mature B cell), and MPC-11 (plasma cell), showed detectable levels of CAT expression. The WEHI-231 (mature B cell) cell lines did not show detectable levels of CAT reporter activity. The strong levels of expression were observed with a fragment of the proximal promoter spanning the region from -365 to -95 (from the translation start point). However, Northern analysis of RNA obtained from the five murine B-cell lines, representing various stages of B-cell development, showed that the 70Z/3, MPC-11 but not BA/F3, and 2PK3 cells expressed detectable levels of syndecan-1 mRNA. By FACS analysis, using a rat anti mouse syndecan-1 antibody, syndecan-1 expression on the cell surface was found to correlate with the observed mRNA expression patterns in these cell lines. Our results indicate that the proximal promoter of the murine syndecan-1 promoter is not sufficient for the observed developmental pattern of syndecan expression in B cells.

Broad Spectrum of Time of Detection, Primary Symptoms and Disease Progression in Infants with HIV-1 Infection

The relationship between time of HIV-1 detection, appearance of symptoms and disease progression was studied in all 24 HIV-1-infected infants from a cohort of 117 children who were born to HIV-1-infected mothers and monitored from birth. HIV isolation from plasma and mononuclear cells, HIV-1 DNA PCR (polymerase chain reaction) and, retrospectively, a quantitative assay for HIV-1 RNA were used for virus detection. Two infants possibly exhibited a symptomatic primary HIV infection. More children with than without symptoms during the first year of life progressed to immunological class 3 (P=0.013) and to AIDS or death (P=0.003) during follow-up. HIV-1 was detected within 4 days of age in 4 of 16 infants: 3 of them became symptomatic within 1 year, as did 6 of the remaining 12 infants (not statistically significant). All four infants in whom virus was detected within 4 days of age progressed to severe immunosuppression, compared to 6 of 14 in whom the virus detection test was initially negative prior to the first positive result (n.s.). Two children with previous repeatedly negative HIV detection tests were diagnosed with HIV-1 infection at 8 and 9 months, respectively. Repeated blood sampling is needed for the diagnosis of HIV-1 infection in perinatally exposed infants, and virus detection tests for exclusion of HIV-1 infection must be used with caution.

High-dose chemotherapy and APSCT as a potential cure for relapsing hemolysing AILD

Angioimmunoblastic lymphadenopathy with dysproteinemia (or dysgammaglobulinemia) (AILD) is a lymphoproliferative disorder with cytogenetic and molecular abnormalities characteristic of malignant T-cell lymphoma (angioimmunoblastic T-cell lymphoma -- AITL). We report the clinical course of a 58-year-old male patient with unusually aggressive AILD, including severe hemolysis and Guillain-Barré syndrome, who entered complete remission after CHOP therapy, but had a full relapse after 2 months. At relapse, treatment with high-dose chemotherapy followed by autologous peripheral stem cell transplantation (APSCT) with CD34 selected cells was shown to be successful. The patient is alive and disease-free 3 years after diagnosis and 32 months after APSCT. Considering the poor prognosis of the majority of patients with AILD, intensive treatment followed by APSCT, may be a subject for further studies.

Activation of T cells in the blood of patients with acute malaria: proliferative activity as indicated by Ki-67 expression

The expression of the proliferation-associated nuclear antigen Ki-67 in peripheral blood mononuclear cells was studied in 30 patients with acute malarial illness and 11 healthy controls from Addis Ababa or Nazareth in Ethiopia. Seventeen patients had Plasmodium falciparum infections and 13 had Plasmodium vivax. Two-colour immunoenzymatic staining was developed in order to simultaneously detect the expression of the nuclear antigen Ki-67 and determine the surface phenotype of the cell. The median percentage of proliferating, Ki-67 positive lymphocytes was significantly higher in patients with acute P. falciparum (11.8%) and P. vivax (15.6%) illnesses compared to the controls (4.3%). The majority of Ki-67 positive cells were T cells (CD3+) while the relative increase of Ki-67 expressing cells was similar for both the CD4+ and CD8+ T-cell subsets. Our data show an increased number of activated cells driven to proliferation in the peripheral blood of patients during acute malaria illness.

Apoptosis in refractory anaemia with ringed sideroblasts is initiated at the stem cell level and associated with increased activation of caspases

Treatment with granulocyte colony-stimulating factor plus erythropoietin may improve haemoglobin levels in patients with ringsideroblastic anaemia (RARS) and reduce bone marrow apoptosis. We studied bone marrow from 10 RARS patients, two of whom were also investigated after successful treatment. Mononuclear, erythroid and CD34+ cells were analysed with regard to proliferation, apoptosis, clonogenic capacity and oncoprotein expression, in the presence or absence of Fas-agonist, Fas-blocking antibody 2 and caspase-3 inhibitor. During culture, RARS bone marrow cells showed higher spontaneous apoptosis (P < 0.05) and caspase activity (P < 0.05)) than bone marrow cells from healthy donors. Eight out of nine patients had reduced growth of erythroid colony-forming units (CFU-E) (< 10% of control) and granulocyte-macrophage CFU (CFU-GM) (< 50% of control) from CD34+ cells. Fas ligation increased apoptosis and decreased colony growth equally in RARS and controls, but caused significantly more caspase activation in RARS (P < 0.01). Fas-blocking antibody showed no significant inhibitory effect on spontaneous apoptosis or ineffective haematopoiesis, as measured using phosphatidylserine exposure, the terminal deoxynucleotide transferase-mediated dUTP-biotin nick-end labelling technique, caspase activity or clonogenic growth. Caspase inhibition reduced apoptosis, increased proliferation and enhanced erythroid colony growth from CD34+ cells in RARS, but showed no effect on normal cells. CFU-E improved > 1000% after successful treatment. Thus, erythroid apoptosis in RARS is initiated at the CD34+ level and growth factor treatment may improve stem cell function. Enhanced caspase activation at the stem cell level, albeit not mediated through endogenous activation of the Fas receptor, contributes to the erythroid apoptosis in RARS.

Downregulation of bactericidal peptides in enteric infections: a novel immune escape mechanism with bacterial DNA as a potential regulator

Antibacterial peptides are active defense components of innate immunity. Several studies confirm their importance at epithelial surfaces as immediate barrier effectors in preventing infection. Here we report that early in Shigella spp. infections, expression of the antibacterial peptides LL-37 and human beta-defensin-1 is reduced or turned off. The downregulation is detected in biopsies from patients with bacillary dysenteries and in Shigella- infected cell cultures of epithelial and monocyte origin. This downregulation of immediate defense effectors might promote bacterial adherence and invasion into host epithelium and could be an important virulence parameter. Analyses of bacterial molecules causing the downregulation indicate Shigella plasmid DNA as one mediator.

In vivo nuclear delivery of oligonucleotides via hybridizing bifunctional peptides

Linking proteins directly to nucleic acids has been a complex task. By hybridizing a bifunctional peptide nucleic acid (PNA) consisting of a nucleic acid binding moiety and a nuclear localization signal (NLS) we have previously demonstrated that it is possible to link protein functions directly to nucleic acids containing a PNA target site. By hybridizing fluorescently labeled oligonucleotides to PNA-NLS molecules and subsequently transfecting different organs in vivo we demonstrate an active nuclear translocation of the PNA-NLS/oligonucleotide complex in different mouse organs.

Nucleocytoplasmic shuttling of Bruton's tyrosine kinase

Bruton's tyrosine kinase (Btk), a nonreceptor cytoplasmic tyrosine kinase belonging to the Tec family of kinases, has been shown to be critical for B cell proliferation, differentiation, and signaling. Loss-of-function mutations in the Btk gene lead to X-linked agammaglobulinemia (XLA), a primary immunodeficiency in humans, and the less severe condition xid in mice. Although Btk is mainly localized in the cytoplasm under steady state conditions, it translocates to the plasma membrane upon growth factor stimulation and cross-linking of the B cell receptor. Nevertheless, in ectopically as well as endogenously Btk-expressing cells, it can also translocate to the nucleus. Deletion of the pleckstrin homology (PH) domain (DeltaPH1) leads, however, to an even redistribution of Btk within the nucleus and cytoplasm in the majority of transfected cells. In contrast, an SH3-deleted (DeltaSH3) mutant of Btk has been found to be predominantly nuclear. We also demonstrate that the nuclear accumulation of DeltaPH1 is dependent on Src expression. This nucleocytoplasmic shuttling is sensitive to the exportin 1/CRM1-inactivating drug, leptomycin B, indicating that Btk utilizes functional nuclear export signals. In addition, while the DeltaPH1 mutant of Btk was found to be active and tyrosine-phosphorylated in vivo, DeltaSH3 displayed decreased autokinase activity and was not phosphorylated. Our findings indicate that the nucleocytoplasmic shuttling of Btk has implications regarding potential targets inside the nucleus, which may be critical in gene regulation during B cell development and differentiation.

T cell activation in patients with ANCA-associated vasculitis: inefficient immune suppression by therapy

BACKGROUND AND AIMS

Patients with vasculitic disease and autoantibodies to neutrophil cytoplasmic antigens (ANCA) generally respond to immunosuppressive therapy with a reduction of the inflammation and lowering of the ANCA titre. However, most patients experience relapses, sometimes after years of quiescence. In the present study we addressed the question whether the relapsing nature of this disease could be dependent on an underlying T cell activation. Patients were analyzed at disease onset, in remission while on treatment, and in quiescence.

PATIENTS AND METHODS

Blood lymphocyte subsets and the expression of molecules associated with T cell activation were analyzed by flow cytometry and soluble interleukin-2 receptor (sIL2r) levels in serum by ELISA. Three patient categories (la, 1b and 2) were studied and compared with age-matched healthy controls (1a: 16 patients at onset of the disease before therapy, 1b: 10 patients from group 1a, re-analyzed after first remission, 2: 11 other patients in quiescence, 2-10 years after debut).

RESULTS

All patient groups, 1a, 1b and 2, showed signs of T cell activation such as reduced CD28 on CD3+ and increased of the early T cell activation marker CD69 on CD3+, as well as of CD38 on CD8+ T cells. The sIL2r levels were significantly raised in all patient categories (la: 4280, 1b: 1844, 2: 2882 ng/ml) compared with the controls (923 ng/ml).

CONCLUSION

Patients with ANCA-positive vasculitis show an increased expression of T cell activation markers irrespective of immunosuppressive therapy or disease phase. Such memory cells may form the basis for the remitting course of vasculitides and would be a rational target for new strategies of therapy.

Ex vivo T lymphocyte expansion for retroviral transduction: influence of serum-free media on variations in cell expansion rates and lymphocyte subset distribution

OBJECTIVE

In the setting of allogeneic stem cell transplantation, suicide gene-manipulated donor T cells that can be selectively inactivated in vivo would potentially allow optimal control of the GVL (graft-vs-leukemia)/GVHD (graft-vs-host disease) balance. Retroviral T-cell transduction requires ex vivo cell expansion, which is often achieved by IL-2 and anti-CD3 stimulation. Traditionally, culture media for cell expansion are supplemented with fetal bovine serum (FBS) or human serum. While these sera promote cell growth and viability, they contain uncharacterized elements that may yield inconsistent results from batch to batch. Cell expansion in serum-free media would therefore be preferable.

MATERIALS AND METHODS

We compared T-cell expansion rates in three commercially available serum-free culture media (X-VIVO 15, AIM-V, and Cellgro SCGM), with or without the addition of human serum (HS, 5%). We also aimed to evaluate how the in vitro expansion affected the composition of the various T-cell subsets. Buffy-coats from four healthy donors were expanded for 21 days. The media were compared to standard RPMI 1640 medium, supplemented with HS (5%) or FBS (10%). For retroviral transductions, the LN vector carrying the neomycin- resistance gene was used in four additional donors.

RESULTS

In our hands, X-VIVO 15 gave the highest rate of serum-free expansion (a median of 79-fold expansion, range 20-117). For serum-free expansion, activation with OKT3 for 21 days gave slightly higher expansion rates than a 5-day course (however, without statistical significance). When serum was added, this discrepancy was not seen. Cytokine analysis (IFN-gamma, IL-10, and IL-4) showed a distinct type1 cytokine pattern with elevated IFN-gamma levels during the whole period of culture. Flow cytometric analyses showed substantial inter-media, but also some inter-donor, variability in T-cell subset compositions. Transduction of cells with the LN vector and G418 selection resulted in a 14-fold increase (range 3-18) for serum-free X-VIVO 15 based cultures. Cell phenotypes remained unchanged by the transduction procedure as compared to nontransduced cells.

CONCLUSION

Among the tested serum-free media, X-VIVO 15 has shown to best support the in vitro expansion of T cells, resulting in equal percentages of CD4(+) and CD8(+) cells. These cells can easily be transduced and selected. There seem to be no significant benefits, regarding absolute cell numbers or T-cell subset compositions, with OKT3-stimulation for more than five days. The addition of low levels of HS increases the consistencies in the cell expansion rates for all media.

Urine D-arabinitol/L-arabinitol ratio in diagnosis of invasive candidiasis in newborn infants

Infants treated in neonatal intensive care units suffer an increased risk for invasive candidiasis, but the diagnosis is sometimes difficult. D-arabinitol is a metabolite of most pathogenic Candida species. An elevated urine D-arabinitol/L-arabinitol (DA/LA) ratio is a sensitive sign of invasive candidiasis in children with cancer, but the method has not been previously evaluated for newborn infants. We therefore enrolled 117 infants in a neonatal intensive care unit, and 411 urine samples were obtained on filter paper. The DA/LA ratio was measured by gas chromatography-mass spectrometry. For 81 infants with no suspicion of superficial or invasive candidiasis, the urine DA/LA ratio was 2.7 +/- 0.7 (mean +/- standard deviation [SD]). The upper cutoff level was set at 4.8 (mean plus 3 SD). Of 22 infants with mucocutaneous candidiasis and not given systemic antifungal treatment, two had elevated DA/LA ratios, which normalized after removal of intravascular catheters. Eight other infants were given empiric antifungal treatment but had negative cultures; five of these had repeatedly elevated DA/LA ratios. Six infants with culture-positive invasive candidiasis all had one or more samples with elevated ratios. For seven infants, three with suspected and four with confirmed invasive candidiasis (for which follow-up samples were available), ratios normalized during antifungal treatment. In conclusion, urine DA/LA ratio determination is a rapid test and can be used for newborns. It is possibly more sensitive than fungal blood cultures in the diagnosis of invasive candidiasis and can also be used for monitoring the effect of antifungal treatment.

Disease-dependent changes in T-cell populations in patients with shigellosis

In shigellosis, bacterial infection is associated with an extensive inflammation of the rectal mucosa, resulting in bloody dysentery. The role of T-cell-mediated pro-inflammatory mechanisms has been implicated in this process, but the specific role of T-cell subsets is still not well understood. In this study we attempted to identify the changes in T-cell populations in patients with shigellosis during the disease course. The T-cell subset distribution was analyzed by immunohistochemistry in the rectal mucosa and by immuno-flow cytometry in the peripheral blood. Blood and rectal biopsies were studied from patients with Shigella dysenteriae 1 (n= 11) and S. flexneri (n= 11) infection and 20 healthy age-matched controls. We found an expansion of gammadelta+T cells in the rectal mucosa, but a decrease in the percentage of gammadelta+T cells in the blood in acute shigellosis. There was also a preferential increase in CD8+ T cells in the surface epithelium of rectal tissue in patients infected with S. dysenteriae 1, but not in patients infected with S. flexneri. Our findings suggest that the rectal mucosal inflammation in shigellosis is associated with an expansion of T cells, in particular CD8+ and gammadelta+T-cell subsets in the gut mucosa, which may be of importance for the pathogenesis of shigellosis.

Augmentation of leukocyte infiltration in murine tumors expressing B-cell derived but not nasopharyngeal carcinoma derived EBV membrane protein LMP1

The Epstein-Barr virus (EBV) encoded latent membrane protein of B cell origin, B-LMP1 (B95-8 prototype) and nasopharyngeal carcinoma (NPC) derived C-LMP1 (CAO prototype) were transfected individually in S6C adenocarcinoma cells of ACA (H-2f) origin. We have shown previously that inoculation of B-LMP1 expressing S6C cells led to tumor rejection in pre-immunized, immunocompetent syngeneic ACA mice, whereas the C-LMP1 transfectants were not immunogenic. Furthermore, B-LMP1 but not C-LMP1 expressing S6C cells grew with necrosis and extensive skin damage in non-immunized mice. A study was carried out to determine whether the in vivo growth pattern of S6C cells expressing two different LMP1 isolates could be correlated to any immunomodulatory mechanism. An increased infiltration of CD45+ leukocytes was found in B-LMP1 expressing S6C tumors originating in non-immunized, syngeneic ACA mice. The C-LMP1 expressors, vector transfectants and untransfected parental tumors had significantly lower number of infiltrating leukocytes. The immunoaccessory molecules ICAM-1, B7-1 and MHC Class I and II expression was unaltered in both B- and C-LMP1 transfectants. The data suggest that B-LMP1 but not C-LMP1 induce anti-tumor immune response.

Interferon-alpha and ribavirin treatment of hepatitis C in children with malignancy in remission

Twenty-eight cases of hepatitis C virus (HCV) infection were identified in children in a pediatric oncology ward during 2 nosocomial outbreaks. HCV infection spontaneously cleared in 6 patients (21%). Eleven patients with persistent HCV viremia who had malignant diseases in remission after treatment were given a 48-week course of combined therapy with interferon-alpha (5x106 U 3 times weekly) and oral ribavirin (15 mg/kg/d). Seven (64%) of the 11 patients had sustained virological responses 6 and 12 months after cessation of therapy. Side effects were common but generally were mild or moderate.

Redistribution of Bruton's tyrosine kinase by activation of phosphatidylinositol 3-kinase and Rho-family GTPases

Bruton's tyrosine kinase (Btk) is a member of the Tec family of protein tyrosine kinases (PTK) characterized by an N-terminal pleckstrin homology domain (PH) thought to directly interact with phosphoinositides. We report here that wild-type (wt) and also a gain-of-function mutant of Btk are redistributed following a wide range of receptor-mediated stimuli through phosphatidylinositol 3-kinase (PI 3-K) activation. Employing chimeric Btk with green fluorescent protein in transient transfections resulted in Btk translocation to the cytoplasmic membrane of live cells through various forms of upstream PI 3-K activation. The redistribution was blocked by pharmacological and biological inhibitors of PI 3-K. A gain-of-function mutant of Btk was found to be a potent inducer of lamellipodia and/or membrane ruffle formation. In the presence of constitutively active forms of Rac1 and Cdc42, Btk is co-localized with actin in these regions. Formation of the membrane structures was blocked by the dominant negative form of N17-Rac1. Therefore, Btk forms a link between a vast number of cell surface receptors activating PI 3-K and certain members of the Rho-family of small GTPases. In the chicken B cell line, DT40, cells lacking Btk differed from wt cells in the actin pattern and showed decreased capacity to form aggregates, further suggesting that cytoskeletal regulation mediated by Btk may be of physiological relevance.

Candida tropicalis vertebral osteomyelitis complicating epidural catheterisation with disease paralleled by elevated D-arabinitol/L-arabinitol ratios

Deep-seated Candida infections are challenging to diagnose by noninvasive means, and new modalities are needed to improve the yield of such investigations. Reported here is a case of Candida tropicalis vertebral osteomyelitis complicating epidural catheterisation in a diabetic patient with complicated abdominal sepsis. The diagnosis was supported by detection of increased D-arabinitol/L-arabinitol ratios in urine samples, and failure of medical management was indicated by elevated D-arabinitol/L-arabinitol ratios, which later decreased to baseline with successful surgical debridement and prolonged antifungal therapy.

D-arabinitol--a marker for invasive candidiasis

The five-carbon sugar alcohol D-arabinitol (DA) is a metabolite of most pathogenic Candida species, in vitro as well as in vivo, and can be determined by gas chromatography or enzymatic analysis. Endogenous DA and L-arabinitol (LA) are present in human body fluids, and serum DA and LA increase in renal dysfunction. In prospective clinical studies, elevated DA/LA or DA/creatine ratios in serum or urine have been found in immunocompromised, usually neutropenic, patients with invasive candidiasis. In addition, positive DA results have been obtained several days to weeks before positive blood cultures, and the normalization of DA levels has been correlated with therapeutic response in both humans and animals. However, to date, only a few prospective studies have been conducted in which adequate analytical methods were used. Thus, further investigation of various patient groups is needed to establish the applicability of the 'arabinitol method' in the diagnostic battery for invasive Candida infections.

SPECT with 99mTc-HMPAO in subjects with HIV infection: cognitive dysfunction correlates with high uptake

We prospectively studied a cohort of 25 HIV-1 infected individuals with no clinical signs of encephalopathy with 99mTc-HMPAO-SPECT. The findings were correlated with magnetic resonance imaging (MRI), neuropsychological testing and clinical staging aiming at the early diagnosis of HIV encephalopathy by single photon emission computed tomography (SPECT). A total of 25 matched seronegative controls were subject to neuropsychological testing only. A total of 24 patients and controls were monitored for 6-46 months (mean and median 26 months). No patients developed AIDS dementia complex during the study; 3 patients developed minimal symptoms (MSK classification stage 0.5). There was a significant decline in 99mTc-HMPAO uptake over time and neuropsychological abnormalities progressed. Unexpectedly, there was a correlation of high cortical and subcortical 99mTc-HMPAO uptake and low performance in cognitive dysfunction tests, indicating a possible inflammatory reaction in the brain with increased blood flow due to HIV infection. We conclude that, in non-demented HIV-infected individuals, both the 99mTc-HMPAO uptake and functional level slowly decrease over time, but the regional cerebral blood flow decrease could be masked by a direct HIV-induced inflammatory reaction in the brain, which gives a 99mTc-HMPAO hyperfixation.

Long-term pattern of HIV-1 RNA load in perinatally infected children

The objective of this study was to describe the natural history of HIV-1 RNA load in vertically HIV-1-infected children. HIV-1 RNA in 156 plasma or serum samples (1-14, median 4 from each child) from 32 vertically HIV-1-infected children was detected with the NASBA technique (Organon Teknika, The Netherlands). Twenty-one children were prospectively followed from birth, and 11 were identified and included at the age of 7-89 (median 61) months. The highest numbers of HIV-1 RNA copies were seen at 1.5-3 months of age. A quadratic curve model showed a reduction of HIV-1 RNA with increasing age up to approximately 8 years, and thereafter increasing numbers, p(age) = 0.002, p(age2) = 0.008. This pattern was not typical for individual children in whom a great variation in HIV-1 RNA numbers was seen over time. The interval from birth to the first HIV-1 RNA peak ranged from 1.5 months to more than 2 years. The HIV-1 RNA levels remained relatively high and fluctuating over the years in symptomatic as well as in long-term asymptomatic children. This makes HIV-1 RNA determination in children more difficult to use than in adults, as the only tool for prediction of disease progression and for initiation of therapy.

Human natural antibodies cytotoxic to pig embryonic brain cells recognize novel non-Galalpha1,3Gal-based xenoantigens

Transplantation of porcine embryonic brain cells, including dopaminergic neurons, from ventral mesencephalon (VM) is considered a potential treatment for patients with Parkinson's disease. In the present study, we characterized the distribution among VM cells of the major porcine endothelial xenoantigen, the Galalpha1,3Gal epitope, and evaluated the cytotoxic effect of anti-Galalpha1,3Gal antibody-depleted and nondepleted human AB serum on VM cells. Overall levels of Galalpha1,3Gal-epitope expression was very low on the VM cell population using Bandeiraea simplicifolia IB(4) lectin staining of resuspended VM cells in flow cytometric analyses or staining of SDS-PAGE-separated, solubilized VM cell membrane proteins in Western blot analyses. Lectin-histochemical staining of sections of pig embryonal VM regions with BSA IB(4) lectin showed staining restricted to endothelial cells and microglia. In the presence of complement, both nondepleted and anti-Galalpha1,3Gal antibody-depleted AB sera were shown to be cytotoxic to VM cells as assessed in microcytotoxicity- and flow cytometry-based cytotoxicity assays. Purified IgM and IgG were both cytotoxic in the presence of complement. Three major VM cell membrane antigens of approximately 210, 105, and 50 kDa were reactive with natural IgM antibodies present in pooled human AB sera. Thus, antibody-dependent cytotoxicity may contribute to pig to human brain cell xenorejection, necessitating donor tissue modifications prior to a more widespread utilization of neural tissue xenografting.

Comparative studies on neutralisation of primary HIV-1 isolates by human sera and rabbit anti-V3 peptide sera

IgG binding to V3 peptides and serum neutralising responses were studied in four HIV-1 infected individuals with progressive disease over a period of 31-70 months. The 18-20 mer peptides comprised residues 299-317 (numbering of HIV1 MN) in the N-terminal half of the V3 loop of the envelope glycoprotein gp120 and were derived from the sequences of autologous, as well as heterologous isolates. All four individuals studied lacked anti-V3 IgG binding to at least one autologous V3 sequence. V3 peptides to which autologous sera lacked binding IgG were all immunogenic in rabbits and induced antisera that were broadly cross-reactive by EIA and broadly cross-neutralising to primary HIV-1 isolates. This indicates that the peptides are immunogenic per se and that the respective human hosts have selective defects in recognising the corresponding V3 sequences. Despite the absence of antibody binding to autologous V3 peptides, the human sera had neutralising antibodies to autologous (three out of four cases), as well as heterologous isolates (all cases). Moreover, in vitro exposure of the patients' isolates to autologous neutralising serum or the homologous rabbit antiserum selected for variants with amino acid substitutions close to the crown of the V3 loop or in regions outside the sequence corresponding to peptides used for immunisation. The amino acid exchanges affected V3 positions known to be antigenic and which are also prone to change successively in infected persons. It is likely that neutralising antibodies recognise both linear and conformational epitopes in the V3 loop. Apparently, there are several, but restricted, numbers of ways for this structure to change its conformation and thereby give rise to neutralisation resistant viruses.