Hemoglobin S and C affect biomechanical membrane properties of P. falciparum-infected erythrocytes.

During intraerythrocytic development, the human malaria parasite Plasmodium falciparum alters the mechanical deformability of its host cell. The underpinning biological processes involve gain in parasite mass, changes in the membrane protein compositions, reorganization of the cytoskeletons and its coupling to the plasma membrane, and formation of membrane protrusions, termed knobs. The hemoglobinopathies S and C are known to partially protect carriers from severe malaria, possibly through additional changes in the erythrocyte biomechanics, but a detailed quantification of cell mechanics is still missing. Here, we combined flicker spectroscopy and a mathematical model and demonstrated that knob formation strongly suppresses membrane fluctuations by increasing membrane-cytoskeleton coupling. We found that the confinement increased with hemoglobin S but decreases with hemoglobin C in spite of comparable knob densities and diameters. We further found that the membrane bending modulus strongly depends on the hemoglobinopathetic variant, suggesting increased amounts of irreversibly oxidized hemichromes bound to membranes.

Single-molecule imaging and quantification of the immune-variant adhesin VAR2CSA on knobs of Plasmodium falciparum-infected erythrocytes.

PfEMP1 (erythrocyte membrane protein 1) adhesins play a pivotal role in the pathophysiology of falciparum malaria, by mediating sequestration of Plasmodium falciparum-infected erythrocytes in the microvasculature. PfEMP1 variants are expressed by var genes and are presented on membrane elevations, termed knobs. However, the organization of PfEMP1 on knobs is largely unclear. Here, we use super-resolution microscopy and genetically altered parasites expressing a modified var2csa gene in which the coding sequence of the photoactivatable mEOS2 was inserted to determine the number and distribution of PfEMP1 on single knobs. The data were verified by quantitative fluorescence-activated cell sorting analysis and immuno-electron microscopy together with stereology methods. We show that knobs contain 3.3 ± 1.7 and 4.3 ± 2.5 PfEMP1 molecules, predominantly placed on the knob tip, in parasitized erythrocytes containing wild type and sickle haemoglobin, respectively. The ramifications of our findings for cytoadhesion and immune evasion are discussed.

The sickle cell trait affects contact dynamics and endothelial cell activation in Plasmodium falciparum-infected erythrocytes.

Sickle cell trait, a common hereditary blood disorder, protects carriers from severe disease in infections with the human malaria parasite Plasmodium falciparum. Protection is associated with a reduced capacity of parasitized erythrocytes to cytoadhere to the microvascular endothelium and cause vaso-occlusive events. However, the underpinning cellular and biomechanical processes are only partly understood and the impact on endothelial cell activation is unclear. Here, we show, by combining quantitative flow chamber experiments with multiscale computer simulations of deformable cells in hydrodynamic flow, that parasitized erythrocytes containing the sickle cell haemoglobin displayed altered adhesion dynamics, resulting in restricted contact footprints on the endothelium. Main determinants were cell shape, knob density and membrane bending. As a consequence, the extent of endothelial cell activation was decreased. Our findings provide a quantitative understanding of how the sickle cell trait affects the dynamic cytoadhesion behavior of parasitized erythrocytes and, in turn, endothelial cell activation.

Impact of the HIV-1 genetic background and HIV-1 population size on the evolution of raltegravir resistance.

BACKGROUND: Emergence of resistance against integrase inhibitor raltegravir in human immunodeficiency virus type 1 (HIV-1) patients is generally associated with selection of one of three signature mutations: Y143C/R, Q148K/H/R or N155H, representing three distinct resistance pathways. The mechanisms that drive selection of a specific pathway are still poorly understood. We investigated the impact of the HIV-1 genetic background and population dynamics on the emergence of raltegravir resistance. Using deep sequencing we analyzed the integrase coding sequence (CDS) in longitudinal samples from five patients who initiated raltegravir plus optimized background therapy at viral loads > 5000 copies/ml. To investigate the role of the HIV-1 genetic background we created recombinant viruses containing the viral integrase coding region from pre-raltegravir samples from two patients in whom raltegravir resistance developed through different pathways. The in vitro selections performed with these recombinant viruses were designed to mimic natural population bottlenecks. RESULTS: Deep sequencing analysis of the viral integrase CDS revealed that the virological response to raltegravir containing therapy inversely correlated with the relative amount of unique sequence variants that emerged suggesting diversifying selection during drug pressure. In 4/5 patients multiple signature mutations representing different resistance pathways were observed. Interestingly, the resistant population can consist of a single resistant variant that completely dominates the population but also of multiple variants from different resistance pathways that coexist in the viral population. We also found evidence for increased diversification after stronger bottlenecks. In vitro selections with low viral titers, mimicking population bottlenecks, revealed that both recombinant viruses and HXB2 reference virus were able to select mutations from different resistance pathways, although typically only one resistance pathway emerged in each individual culture. CONCLUSIONS: The generation of a specific raltegravir resistant variant is not predisposed in the genetic background of the viral integrase CDS. Typically, in the early phases of therapy failure the sequence space is explored and multiple resistance pathways emerge and then compete for dominance which frequently results in a switch of the dominant population over time towards the fittest variant or even multiple variants of similar fitness that can coexist in the viral population.

High seroprevalence of antibodies against Kaposi's sarcoma-associated herpesvirus (KSHV) among HIV-1-infected children and adolescents in a non-endemic population.

Human herpesvirus-8 (HHV-8) is the etiological agent of Kaposi's sarcoma (KS), which primarily affects human immunodeficiency virus (HIV)-infected adults with advanced immunodeficiency. Currently, only limited prevalence data for HHV-8 infection in HIV-infected children living in non-endemic areas are available. This multicenter cross-sectional study was conducted in four university hospitals in Germany specializing in pediatric HIV care. Stored serum specimens obtained from 207 vertically HIV-1-infected children and adolescents were tested for antibodies against lytic and latent HHV-8 antigens. Logistic regression was used to assess independent risk factors associated with HHV-8 seropositivity. The overall HHV-8 seroprevalence was 24.6 % (n = 51/207) without significant differences related to sex, age, or ethnicity. In univariate analysis, HHV-8 seropositivity was significantly associated with a child having being born outside Germany, maternal origin from sub-Saharan Africa, a history of breastfeeding, CDC immunologic category 3, and deferred initiation of antiretroviral therapy (>24 months of age). In multivariate analysis, a child's birth outside Germany was the only significant risk factor for HHV-8 seropositivity (odds ratio 3.98; 95 % confidence interval 1.27-12.42). HHV-8-associated malignancies were uncommon; only one patient had a history of KS. Serum specimen of vertically HIV-infected children and adolescents living in Germany showed a high HHV-8 seroprevalence. These findings suggest that primary HHV-8 infection-a risk factor for KS and other HHV-8-associated malignancies-occurs early in life. Thus, management of perinatally HIV-infected children should include testing for HHV-8 coinfection and should consider future risks of HHV-8-associated malignancies.

Biochemical characterization of a multi-drug resistant HIV-1 subtype AG reverse transcriptase: antagonism of AZT discrimination and excision pathways and sensitivity to RNase H inhibitors.

We analyzed a multi-drug resistant (MR) HIV-1 reverse transcriptase (RT), subcloned from a patient-derived subtype CRF02_AG, harboring 45 amino acid exchanges, amongst them four thymidine analog mutations (TAMs) relevant for high-level AZT (azidothymidine) resistance by AZTMP excision (M41L, D67N, T215Y, K219E) as well as four substitutions of the AZTTP discrimination pathway (A62V, V75I, F116Y and Q151M). In addition, K65R, known to antagonize AZTMP excision in HIV-1 subtype B was present. Although MR-RT harbored the most significant amino acid exchanges T215Y and Q151M of each pathway, it exclusively used AZTTP discrimination, indicating that the two mechanisms are mutually exclusive and that the Q151M pathway is obviously preferred since it confers resistance to most nucleoside inhibitors. A derivative was created, additionally harboring the TAM K70R and the reversions M151Q as well as R65K since K65R antagonizes excision. MR-R65K-K70R-M151Q was competent of AZTMP excision, whereas other combinations thereof with only one or two exchanges still promoted discrimination. To tackle the multi-drug resistance problem, we tested if the MR-RTs could still be inhibited by RNase H inhibitors. All MR-RTs exhibited similar sensitivity toward RNase H inhibitors belonging to different inhibitor classes, indicating the importance of developing RNase H inhibitors further as anti-HIV drugs.

Unmistakable Morphology? Infantile Malignant Osteopetrosis Resembling Juvenile Myelomonocytic Leukemia in Infants.

The initial clinical and hematologic presentation of infantile malignant osteopetrosis may be indistinguishable from that of juvenile myelomonocytic leukemia in infants. Timely radiographic imaging, however, allows straightforward delineation of these 2 severe diseases and facilitates immediate initiation of appropriate therapy.

The impact of prehydration on the clearance and toxicity of high-dose methotrexate for pediatric patients.

Abstract High-dose methotrexate (HD-MTX) is an important chemotherapy for various pediatric malignancies. However, in contrast to precise recommendations on supportive care following the start of HD-MTX infusion, studies on the hydration regimen prior to HD-MTX infusion are lacking, and the local standard differs between pediatric oncology centers. Therefore, we prospectively evaluated the relevance of two common prehydration regimens on the clearance and toxicity of MTX in a randomized crossover study. There was no impact of the prehydration regimen on plasma levels and toxicity of MTX, but most parents preferred a fast prehydration regimen due to a significantly shorter inpatient treatment (mean duration 3.39 ± 0.79 days vs. 4.36 ± 0.70 days, p < 0.001). Based on our results, short prehydration seems safe, and may be recommended prior to the start of HD-MTX infusions instead of initiating hydration the preceding day.

HIV-1 seroreversion in HIV-1-infected children: do genetic determinants play a role?

BACKGROUND: HIV-1 seroreversion in infants with vertically transmitted HIV-1 infection who started ART in the first months of life has been reported in only a subset of patients. However, the reason why most infants remain seropositive despite similar treatment response is not understood. Here, we assessed whether HIV-1 seroreversion in maternally infected infants is associated with genetic determinants. METHODS: HIV-1-infected infants with a history of documented HIV-1 seroreversion were identified throughout Germany using a standardized questionnaire. At study entry immune reconstitution and anti-HIV-1 antibody expression were monitored as clinical parameters. To search for genetic determinants high-resolution HLA genotyping was performed. In addition, the coding sequence of the chemokine receptor CCR5 was analyzed by Sanger sequencing regarding potential mutations. RESULTS: Patients showed normal numbers and frequencies of lymphocyte subpopulations. Five out of eight patients still had seronegative HIV-1 antibody status at study entry. HLA genotyping revealed the enrichment of HLA-DQB1*03 and DQB1*06 alleles within the patient cohort. Only one patient was found to carry a 32 bp-deletion within the CCR5 gene. CONCLUSION: Our results indicate that the phenotype of HIV-1 seroreversion in infants might correlate with the presence of HLA class II alleles DQB1*03 and DQB1*06. This finding supports the idea of genetic predisposition determining HIV-1 seroreversion in vertically infected infants effectively treated with ART.

Mutations in HIV-1 gag and pol compensate for the loss of viral fitness caused by a highly mutated protease.

During the last few decades, the treatment of HIV-infected patients by highly active antiretroviral therapy, including protease inhibitors (PIs), has become standard. Here, we present results of analysis of a patient-derived, multiresistant HIV-1 CRF02_AG recombinant strain with a highly mutated protease (PR) coding sequence, where up to 19 coding mutations have accumulated in the PR. The results of biochemical analysis in vitro showed that the patient-derived PR is highly resistant to most of the currently used PIs and that it also exhibits very poor catalytic activity. Determination of the crystal structure revealed prominent changes in the flap elbow region and S1/S1' active site subsites. While viral loads in the patient were found to be high, the insertion of the patient-derived PR into a HIV-1 subtype B backbone resulted in reduction of infectivity by 3 orders of magnitude. Fitness compensation was not achieved by elevated polymerase (Pol) expression, but the introduction of patient-derived gag and pol sequences in a CRF02_AG backbone rescued viral infectivity to near wild-type (wt) levels. The mutations that accumulated in the vicinity of the processing sites spanning the p2/NC, NC/p1, and p6pol/PR proteins lead to much more efficient hydrolysis of corresponding peptides by patient-derived PR in comparison to the wt enzyme. This indicates a very efficient coevolution of enzyme and substrate maintaining high viral loads in vivo under constant drug pressure.

German-Austrian recommendations for HIV1-therapy in pregnancy and in HIV1-exposed newborn, update 2008.

In Germany during the last years about 200-250 HIV1-infected pregnant women delivered a baby each year, a number that is currently increasing. To determine the HIV-status early in pregnancy voluntary HIV-testing of all pregnant women is recommended in Germany and Austria as part of prenatal care. In those cases, where HIV1-infection was known during pregnancy, since 1995 the rate of vertical transmission of HIV1 was reduced to 1-2%. - This low transmission rate has been achieved by the combination of anti-retroviral therapy of pregnant women, caesarean section scheduled before onset of labour, anti-retroviral post exposition prophylaxis in the newborn and refraining from breast-feeding by the HIV1-infected mother. To keep pace with new results in research, approval of new anti-retroviral drugs and changes in the general treatment recommendations for HIV1-infected adults, in 1998, 2001, 2003 and 2005 an interdisciplinary consensus meeting was held. Gynaecologists, infectious disease specialists, paediatricians, pharmacologists, virologists and members of the German AIDS Hilfe (NGO) were participating in this conference to update the prevention strategies. A fifth update became necessary in 2008. The updating process was started in January 2008 and was terminated in September 2008. The guidelines provide new recommendations on the indication and the starting point for HIV-therapy in pregnancies without complications, drugs and drug combinations to be used preferably in these pregnancies and updated information on adverse effects of anti-retroviral drugs. Also the procedures for different scenarios and risk constellations in pregnancy have been specified again. - With these current guidelines in Germany and Austria the low rate of vertical HIV1-transmission should be further maintained.

German-Austrian recommendations for HIV-therapy in pregnancy and in HIV-exposed newborn - update 2005.

In Germany during the last years about 200-250 HIV infected pregnant women delivered a baby each year, a number that is currently increasing. To determine the HIV-status early in pregnancy voluntary HIV-testing of all pregnant women is recommended in Germany and Austria as part of prenatal care. In those cases, where HIV infection was known during pregnancy, since 1995 the rate of vertical transmission of HIV was reduced to 1-2%. - This low transmission rate has been achieved by the combination of anti-retroviral therapy of pregnant women, caesarean section scheduled before onset of labour, anti-retroviral post exposition prophylaxis in the newborn and refraining from breast-feeding by the HIV infected mother. To keep pace with new results in research, approval of new anti-retroviral drugs and changes in the general treatment recommendations for HIV infected adults, in 1998, 2001 and 2003 an interdisciplinary consensus meeting was held. Gynaecologists, infectious disease specialists, paediatricians, pharmacologists, virologists and members of the German AIDS Hilfe (NGO) were participating in this conference to update the prevention strategies. A third update became necessary in 2005. The updating process was started in January 2005 and was terminated in September 2005. The guidelines provide new recommendations on the indication and the starting point for therapy in pregnancies without complications, drugs and drug combinations to be used preferably in these pregnancies and updated information on adverse effects of anti-retroviral drugs. Also the procedures for different scenarios and risk constellations in pregnancy have been specified again. With these current guidelines in Germany and Austria the low rate of vertical HIV-transmission should be further maintained.

German-Austrian recommendations for HIV-therapy in pregnancy: update May 2003.

In Germany during the past years about 200-250 HIV infected pregnant women delivered a baby per year, a number that is currently increasing. To determine the HIV-status early in pregnancy voluntary HIV-testing of all pregnant women is recommended in Germany and Austria as part of prenatal care. In those cases, where HIV infection was known during pregnancy, since 1995 the rate of vertical transmission of HIV was reduced to 1-2%. - This low transmission rate has been achieved by the combination of anti-retroviral treatment of pregnant women, elective caesarean section before onset of labor, anti-retroviral post exposition prophylaxis in the newborn and refraining from breast-feeding by the HIV infected mother. To keep pace with new results in research, approval of new anti-retroviral drugs and changes in the general treatment recommendations for HIV infected adults, in 1998 and 2001 an interdisciplinary consensus meeting was held. Gynaecologists, infectious disease specialists, pediatricians, pharmacologists, virologists and members of the German AIDS Hilfe (NGO) were participating in this conference to update the prevention strategies. A third update became necessary in 2003. The updating process was started in January 2003 and was terminated in July 2003. The guidelines provide new recommendations on the indication and the starting point for HIV-therapy in pregnancies without complications, drugs and drug combinations to be used preferably in these pregnancies and updated information on adverse effects of anti-retroviral drugs. Also the procedures for different scenarios and risk constellations in pregnancy have been specified again. - With these current guidelines in Germany and Austria the low rate of vertical HIV-transmission should be further maintained or even further lowered.

German-Austrian recommendations for HIV-therapy in pregnancy--common declaration of The German AIDS-society (DAIG), The Austrian AIDS-society (OEAG) as well as The Robert-Koch Institute Berlin (RKI), The German Association of Physicians specialized in HIV Care (DAGNAE), The German Society of Pediatric and Youth Medicine (DGKJ), The German AIDS Pediatric Association (PAAD), The German Society of Obstetrics and Gynecology (DGGG), The National Reference Center for Retroviruses (NRZ), German AIDS Assistance (DAH).

Anti-retroviral therapy during pregnancy--The German/Austrian recommendations to optimise prevention of vertical transmission of HIV and to minimise adverse drug effects. In Germany during the last years about 200 HIV infected pregnant women delivered a baby each year, a number that is currently increasing. To determine the HIV-status early in pregnancy voluntary HIV-testing of all pregnant women is recommended in Germany and Austria as part of prenatal care. In those cases, where HIV infection was known during pregnancy, since 1995 the rate of vertical transmission of HIV was reduced to 1-2%. This low transmission rate has been achieved by the combination of anti-retroviral therapy of pregnant women, cesarean section scheduled before onset of labor, anti-retroviral prophylaxis in the newborn and refraining from breast-feeding by the HIV infected mother. In 1998 an interdisciplinary consensus meeting consisting of gynaecologists, infectious disease specialists, paediatricians, pharmacologists, virologists and members of the German AIDS Hilfe (NGO) updated this combined strategy for the first time. A second update became necessary because of new results in research, approval of new anti-retroviral drugs and changes in the general treatment recommendations for HIV infected adults, which are referred to in the pregnancy guidelines. The updating process was started in July 2000 and was finalized in May 2001. In the updated guidelines recommendations for monitoring of HIV infected pregnant women in prenatal care and for preventive procedures for the newborn in delivery room have been included. The guidelines provide new recommendations on the indication and the starting point for anti-retroviral therapy in pregnancies without complications, drugs and drug combinations to be used preferably in these pregnancies and updated information on adverse effects of anti-retroviral drugs. Also the procedures for different scenarios and risk constellations in pregnancy have been specified. With these current guidelines in Germany and Austria the low rate of vertical HIV-transmission should be further maintained.

The Analysis of Bacterial Results in the Kidney Perfusion Fluid and Bone Allografts in Human Multiorgan Donors.

In 19 young human multiorgan donors, we simultaneously analyzed the bacterial contamination of the kidney perfusion fluid and all retrieved bone allografts. Donor exclusion criteria were done according to the American and European Association of Tissue Banks excluding all patients with perforating wounds. The kidney perfusate revealed a contamination in 17 of 19 (89.5%) donors. Allograft testing demonstrated positive bacterial growth in 34 of 76 allografts (44.7%). Microorganisms originated from the normal skin flora and could be related to contamination during the harvesting procedure. In 5 cases we cultured identical bacterial subspecies in both cultures as a possible sign for systemic bacterial spreading during the multiorgan harvesting procedure.