Influence of MDR1 C1236T polymorphism on lopinavir plasma concentration and virological response in HIV-1-infected children

Background

Variability in MDR1 and PXR has been associated with differences in drug plasma levels and response to antiretroviral therapy. We investigated whether polymorphisms in MDR1 (T-129C, C1236T and C3435T) and PXR (C63396T) affect lopinavir plasma concentration and the virological or immunological response to HAART in HIV-1-infected children.

Methods

Genotypes were identified in 100 blood donors and 38 HIV-1-infected children. All children received HAART with lopinavir boosted with ritonavir (LPV/r) at the time of LPV plasma level quantification, before (C_trough) and between 1 and 2 h after (C_post-dose) the administration of the next dose of drug. CD4⁺ T-cell counts and plasma viral load were analyzed before and after the initiation of LPV/r.

Results

MDR1 1236T, MDR1 3435T and PXR 63396T alleles showed a frequency of ~ 50% while the MDR1 -129C allele only reached 5%. Children heterozygotes 1236CT showed a significantly lower LPV C_post-dose than homozygotes 1236TT (median C_post-dose = 3.04 μg/ml and 6.50 μg/ml, respectively; p = 0.016). Children heterozygotes 1236CT also had a lower decrease of viral load after 36 weeks of LPV/r exposure compared with homozygotes 1236CC (median viral load changes = − 0.50 log₁₀ copies/ml and − 2.08 log₁₀ copies/ml, respectively; p = 0.047). No effect on the immunological response was observed for polymorphisms of MDR1 or PXR.

Conclusions

Our results suggest that the MDR1 C1236T SNP significantly reduces LPV plasma concentration affecting the virological response to HAART. Heterozygotes 1236CT might have an altered level of P-gp expression/activity in enterocytes and CD4⁺ T lymphocytes that limits the absorption of LPV leading to an impaired virological suppression.     

Human T Lymphotropic Virus Type 1 SU Residue 195 Plays a Role in Determining the Preferential CD4+ T Cell Immortalization/Transformation Tropism

Human T lymphotropic virus type 1 (HTLV-1) mainly causes adult T cell leukemia and predominantly immortalizes/transforms CD4⁺ T cells in culture. HTLV-2 is aleukemic and predominantly immortalizes/transforms CD8⁺ T cells in culture. We have shown previously that the viral envelope is the genetic determinant of the differential T cell tropism in culture. The surface component (SU) of the HTLV-1 envelope is responsible for binding to the cellular receptors for entry. Here, we dissect the HTLV-1 SU further to identify key domains that are involved in determining the immortalization tropism. We generated HTLV-1 envelope recombinant virus containing the HTLV-2 SU domain. HTLV-1/SU2 was capable of infecting and immortalizing freshly isolated peripheral blood mononuclear cells in culture. HTLV-1/SU2 shifted the CD4⁺ T cell immortalization tropism of wild-type HTLV-1 (wtHTLV-1) to a CD8⁺ T cell preference. Furthermore, a single amino acid substitution, N195D, in HTLV-1 SU (Ach.195) resulted in a shift to a CD8⁺ T cell immortalization tropism preference. Longitudinal phenotyping analyses of the in vitro transformation process revealed that CD4⁺ T cells emerged as the predominant population by week 5 in wtHTLV-1 cultures, while CD8⁺ T cells emerged as the predominant population by weeks 4 and 7 in wtHTLV-2 and Ach.195 cultures, respectively. Our results indicate that SU domain independently influences the preferential T cell immortalization tropism irrespective of the envelope counterpart transmembrane (TM) domain. We further showed that asparagine at position 195 in HTLV-1 SU is involved in determining this CD4⁺ T cell immortalization tropism. The slower emergence of the CD8⁺ T cell predominance in Ach.195-infected cultures suggests that other residues/domains contribute to this tropism preference.     

Early Gag Immunodominance of the HIV-Specific T-Cell Response during Acute/Early Infection Is Associated with Higher CD8+ T-Cell Antiviral Activity and Correlates with Preservation of the CD4+ T-Cell Compartment

The important role of the CD8⁺ T-cell response on HIV control is well established. Moreover, the acute phase of infection represents a proper scenario to delineate the antiviral cellular functions that best correlate with control. Here, multiple functional aspects (specificity, ex vivo viral inhibitory activity [VIA] and polyfunctionality) of the HIV-specific CD8⁺ T-cell subset arising early after infection, and their association with disease progression markers, were examined. Blood samples from 44 subjects recruited within 6 months from infection (primary HIV infection [PHI] group), 16 chronically infected subjects, 11 elite controllers (EC), and 10 healthy donors were obtained. Results indicated that, although Nef dominated the anti-HIV response during acute/early infection, a higher proportion of early anti-Gag T cells correlated with delayed progression. Polyfunctional HIV-specific CD8⁺ T cells were detected at early time points but did not associate with virus control. Conversely, higher CD4⁺ T-cell set points were observed in PHI subjects with higher HIV-specific CD8⁺ T-cell VIA at baseline. Importantly, VIA levels correlated with the magnitude of the anti-Gag cellular response. The advantage of Gag-specific cells may result from their enhanced ability to mediate lysis of infected cells (evidenced by a higher capacity to degranulate and to mediate VIA) and to simultaneously produce IFN-γ. Finally, Gag immunodominance was associated with elevated plasma levels of interleukin 2 (IL-2) and macrophage inflammatory protein 1β (MIP-1β). All together, this study underscores the importance of CD8⁺ T-cell specificity in the improved control of disease progression, which was related to the capacity of Gag-specific cells to mediate both lytic and nonlytic antiviral mechanisms at early time points postinfection.     

Large-scale patterns in morphological diversity and species assemblages in Neotropical Triatominae (Heteroptera: Reduviidae)

We analysed the spatial variation in morphological diversity (MDiv) and species richness (SR) for 91 species of Neotropical Triatominae to determine the ecological relationships between SR and MDiv and to explore the roles that climate, productivity, environmental heterogeneity and the presence of biomes and rivers may play in the structuring of species assemblages. For each 110 km x 110 km-cell on a grid map of America, we determined the number of species (SR) and estimated the mean Gower index (MDiv) based on 12 morphological attributes. We performed bootstrapping analyses of species assemblages to identify whether those assemblages were more similar or dissimilar in their morphology than expected by chance. We applied a multi-model selection procedure and spatial explicit analyses to account for the association of diversity-environment relationships. MDiv and SR both showed a latitudinal gradient, although each peaked at different locations and were thus not strictly spatially congruent. SR decreased with temperature variability and MDiv increased with mean temperature, suggesting a predominant role for ambient energy in determining Triatominae diversity. Species that were more similar than expected by chance co-occurred near the limits of the Triatominae distribution in association with changes in environmental variables. Environmental filtering may underlie the structuring of species assemblages near their distributional limits.     

Different nest predator guild associated with egg size in the Patagonian temperate forest

Capsule: Studies of nest predation using artificial nests need to consider the effect of egg size on the types of predator that are detected.

Aims: To estimate the nest predation rate in the Patagonian temperate forest and evaluate the influence of egg size on predator guild.

Methods: On different plant species, we placed 108 nests each containing eggs of either Atlantic Canary Serinus canaria or Common Quail Coturnix coturnix, and a model clay egg of equal size to the real egg. Nest predators were identified from the marks left on the clay eggs or by videos recorded using camera traps.

Results: 86% of the nests were predated. Birds, mainly Chimango Caracara Milvago chimango, were the main nest predators. A marsupial, the Monito del Monte Dromiciops gliroides, and rodents also contributed to nest predation. Nest predation rates were similar for both egg sizes but the nest predator guild was different. Birds and rodents preyed on both eggs but the Monito del Monte consumed mainly small eggs.

Conclusion: Egg size did not influence the rate of nest predation but, instead, affected the nest predator guild. Consequently, in order to avoid underestimating the impacts of small predators, egg size should be considered in studies of nest predation.     

Chromosomal Integrity after UV Irradiation Requires FANCD2-Mediated Repair of Double Strand Breaks

Fanconi Anemia (FA) is a rare autosomal recessive disorder characterized by hypersensitivity to inter-strand crosslinks (ICLs). FANCD2, a central factor of the FA pathway, is essential for the repair of double strand breaks (DSBs) generated during fork collapse at ICLs. While lesions different from ICLs can also trigger fork collapse, the contribution of FANCD2 to the resolution of replication-coupled DSBs generated independently from ICLs is unknown. Intriguingly, FANCD2 is readily activated after UV irradiation, a DNA-damaging agent that generates predominantly intra-strand crosslinks but not ICLs. Hence, UV irradiation is an ideal tool to explore the contribution of FANCD2 to the DNA damage response triggered by DNA lesions other than ICL repair. Here we show that, in contrast to ICL-causing agents, UV radiation compromises cell survival independently from FANCD2. In agreement, FANCD2 depletion does not increase the amount of DSBs generated during the replication of UV-damaged DNA and is dispensable for UV-induced checkpoint activation. Remarkably however, FANCD2 protects UV-dependent, replication-coupled DSBs from aberrant processing by non-homologous end joining, preventing the accumulation of micronuclei and chromatid aberrations including non-homologous chromatid exchanges. Hence, while dispensable for cell survival, FANCD2 selectively safeguards chromosomal stability after UV-triggered replication stress.     

Spatiotemporal Clustering of Mycobacterium tuberculosis Complex Genotypes in Florida: Genetic Diversity Segregated by Country of Birth

BackgroundTuberculosis (TB) is caused by members of the Mycobacterium tuberculosis complex (MTBC). Although the MTBC is highly clonal, between-strain genetic diversity has been observed. In low TB incidence settings, immigration may facilitate the importation of MTBC strains with a potential to complicate TB control efforts.MethodsWe investigated the genetic diversity and spatiotemporal clustering of 2,510 MTBC strains isolated in Florida, United States, between 2009 and 2013 and genotyped using spoligotyping and 24-locus MIRU-VNTR. We mapped the genetic diversity to the centroid of patient residential zip codes using a geographic information system (GIS). We assessed transmission dynamics and the influence of immigration on genotype clustering using space-time permutation models adjusted for foreign-born population density and county-level HIV risk and multinomial models stratified by country of birth and timing of immigration in SaTScan.Conclusions/SignificanceAlmost five percent of TB cases reported in Florida during 2009–2013 were potentially due to recent transmission. Improvements to TB screening practices among the prison population and recent immigrants are likely to impact TB control. Due to the monomorphic nature of available markers, whole genome sequencing is needed to conclusively delineate recent transmission events between U.S. and foreign-born persons.