Recombinant renewable polyclonal antibodies

Only a small fraction of the antibodies in a traditional polyclonal antibody mixture recognize the target of interest, frequently resulting in undesirable polyreactivity. Here, we show that high-quality recombinant polyclonals, in which hundreds of different antibodies are all directed toward a target of interest, can be easily generated in vitro by combining phage and yeast display. We show that, unlike traditional polyclonals, which are limited resources, recombinant polyclonal antibodies can be amplified over one hundred million-fold without losing representation or functionality. Our protocol was tested on 9 different targets to demonstrate how the strategy allows the selective amplification of antibodies directed toward desirable target specific epitopes, such as those found in one protein but not a closely related one, and the elimination of antibodies recognizing common epitopes, without significant loss of diversity. These recombinant renewable polyclonal antibodies are usable in different assays, and can be generated in high throughput. This approach could potentially be used to develop highly specific recombinant renewable antibodies against all human gene products.     

Comparison of different delivery systems of DNA vaccination for the induction of protection against tuberculosis in mice and guinea pigs

The great challenges for researchers working in the field of vaccinology are optimizing DNA vaccines for use in humans or large animals and creating effective single-dose vaccines using appropriated controlled delivery systems. Plasmid DNA encoding the heat-shock protein 65 (hsp65) (DNAhsp65) has been shown to induce protective and therapeutic immune responses in a murine model of tuberculosis (TB). Despite the success of naked DNAhsp65-based vaccine to protect mice against TB, it requires multiple doses of high amounts of DNA for effective immunization. In order to optimize this DNA vaccine and simplify the vaccination schedule, we coencapsulated DNAhsp65 and the adjuvant trehalose dimycolate (TDM) into biodegradable poly (DL-lactide-co-glycolide) (PLGA) microspheres for a single dose administration. Moreover, a single-shot prime-boost vaccine formulation based on a mixture of two different PLGA microspheres, presenting faster and slower release of, respectively, DNAhsp65 and the recombinant hsp65 protein was also developed. These formulations were tested in mice as well as in guinea pigs by comparison with the efficacy and toxicity induced by the naked DNA preparation or BCG. The single-shot prime-boost formulation clearly presented good efficacy and diminished lung pathology in both mice and guinea pigs.     

Antiviral Activity of TMC353121, a Respiratory Syncytial Virus (RSV) Fusion Inhibitor,in a Non-Human Primate Model

BackgroundThe study assessed the antiviral activity of TMC353121, a respiratory syncytial virus (RSV) fusion inhibitor, in a preclinical non-human primate challenge model with a viral shedding pattern similar to that seen in humans, following continuous infusion (CI).MethodsAfrican green monkeys were administered TMC353121 through CI, in 2 studies. Study 1 evaluated the prophylactic and therapeutic efficacy of TMC353121 at a target plasma level of 50 ng/mL (n=15; Group 1: prophylactic arm [Px50], 0.033 mg/mL TMC353121, flow rate 2.5 mL/kg/h from 24 hours pre-infection to 10 days; Group 2: therapeutic arm [Tx50], 0.033mg/mL TMC353121 from 24 hours postinfection to 8 days; Group 3: control [Vh1] vehicle, 24 hours post-infection to 8 days). Study 2 evaluated the prophylactic efficacy of TMC353121 at target plasma levels of 5 and 500 ng/mL (n=12; Group 1: prophylactic 5 arm [Px5], 0.0033 mg/mL TMC353121, flow rate 2.5 mL/kg/h from 72 hours pre-infection to 14 days; Group 2: prophylactic 500 arm [Px500], 0.33 mg/mL TMC353121; Group 3:control [Vh2] vehicle, 14 days). Bronchoalveolar lavage fluid and plasma were collected every 2 days from day 1 postinfection for pharmacokinetics and safety analysis.FindingsTMC353121 showed a dose-dependent antiviral activity, varying from 1log₁₀ reduction of peak viral load to complete inhibition of the RSV replication. Complete inhibition of RSV shedding was observed for a relatively low plasma exposure (0.39 μg/mL) and was associated with a dose-dependent reduction in INFγ, IL6 and MIP1α. TMC353121 administered as CI for 16 days was generally well-tolerated.ConclusionTMC353121 exerted dose-dependent antiviral effect ranging from full inhibition to absence of antiviral activity, in a preclinical model highly permissive for RSV replication. No new safety findings emerged from the study.     

Large‐sized rare tree species contribute disproportionately to functional diversity in resource acquisition in African tropical forest

Increasing evidence is available for a positive effect of biodiversity on ecosystem productivity and standing biomass, also in highly diverse systems as tropical forests. Biodiversity conservation could therefore be a critical aspect of climate mitigation policies. There is, however, limited understanding of the role of individual species for this relationship, which could aid in focusing conservation efforts and forest management planning. This study characterizes the functional specialization and redundancy for 95% of all tree species (basal area weighted percentage) in a diverse tropical forest in the central Congo Basin and relates this to species' abundance, contribution to aboveground carbon, and maximum size. Functional characterization is based on a set of traits related to resource acquisition (wood density, specific leaf area, leaf carbon, nitrogen and phosphorus content, and leaf stable carbon isotope composition). We show that within both mixed and monodominant tropical forest ecosystems, the highest functional specialization and lowest functional redundancy are solely found in rare tree species and significantly more in rare species holding large‐sized individuals. Rare species cover the entire range of low and high functional redundancy, contributing both unique and redundant functions. Loss of species supporting functional redundancy could be buffered by other species in the community, including more abundant species. This is not the case for species supporting high functional specialization and low functional redundancy, which would need specific conservation attention. In terms of tropical forest management planning, we argue that specific conservation of large‐sized trees is imperative for long‐term maintenance of ecosystem functioning.     

Telomere length homeostasis and telomere position effect on a linear human artificial chromosome are dictated by the genetic background

Telomere position effect (TPE) is the influence of telomeres on subtelomeric epigenetic marks and gene expression. Previous studies suggested that TPE depends on genetic background. As these analyses were performed on different chromosomes, cell types and species, it remains unclear whether TPE represents a chromosome—rather than genetic background-specific regulation. We describe the development of a Linear Human Artificial Chromosome (L-HAC) as a new tool for telomere studies. The L-HAC was generated through the Cre-loxP-mediated addition of telomere ends to an existing circular HAC (C-HAC). As it can be transferred to genetically distinct cell lines and animal models the L-HAC enables the study of TPE in an unprecedented manner. The HAC was relocated to four telomerase-positive cell lines via microcell-mediated chromosome transfer and subsequently to mice via blastocyst injection of L-HAC⁺-ES-cells. We could show consistent genetic background-dependent adaptation of telomere length and telomere-associated de novo subtelomeric DNA methylation in mouse ES-R1 cells as well as in mice. Expression of the subtelomeric neomycin gene was inversely correlated with telomere length and subtelomeric methylation. We thus provide a new tool for functional telomere studies and provide strong evidence that telomere length, subtelomeric chromatin marks and expression of subtelomeric genes are genetic background dependent.     

Long‐term recovery of the functional community assembly and carbon pools in an African tropical forest succession

On the African continent, the population is expected to expand fourfold in the next century, which will increasingly impact the global carbon cycle and biodiversity conservation. Therefore, it is of vital importance to understand how carbon stocks and community assembly recover after slash‐and‐burn events in tropical second growth forests. We inventoried a chronosequence of 15 1‐ha plots in lowland tropical forest of the central Congo Basin and evaluated changes in aboveground and soil organic carbon stocks and in tree species diversity, functional composition, and community‐weighted functional traits with succession. We aimed to track long‐term recovery trajectories of species and carbon stocks in secondary forests, comparing 5 to 200 + year old secondary forest with reference primary forest. Along the successional gradient, the functional composition followed a trajectory from resource acquisition to resource conservation, except for nitrogen‐related leaf traits. Despite a fast, initial recovery of species diversity and functional composition, there were still important structural and carbon stock differences between old growth secondary and pristine forest, which suggests that a full recovery of secondary forests might take much longer than currently shown. As such, the aboveground carbon stocks of 200 + year old forest were only 57% of those in the pristine reference forest, which suggests a slow recovery of aboveground carbon stocks, although more research is needed to confirm this observation. The results of this study highlight the need for more in‐depth studies on forest recovery in Central Africa, to gain insight into the processes that control biodiversity and carbon stock recovery.     

Copy-Number Gains of HUWE1 Due to Replication- and Recombination-Based Rearrangements

We previously reported on nonrecurrent overlapping duplications at Xp11.22 in individuals with nonsyndromic intellectual disability (ID) harboring HSD17B10, HUWE1, and the microRNAs miR-98 and let-7f-2 in the smallest region of overlap. Here, we describe six additional individuals with nonsyndromic ID and overlapping microduplications that segregate in the families. High-resolution mapping of the 12 copy-number gains reduced the minimal duplicated region to the HUWE1 locus only. Consequently, increased mRNA levels were detected for HUWE1, but not HSD17B10. Marker and SNP analysis, together with identification of two de novo events, suggested a paternally derived intrachromosomal duplication event. In four independent families, we report on a polymorphic 70 kb recurrent copy-number gain, which harbors part of HUWE1 (exon 28 to 3′ untranslated region), including miR-98 and let-7f-2. Our findings thus demonstrate that HUWE1 is the only remaining dosage-sensitive gene associated with the ID phenotype. Junction and in silico analysis of breakpoint regions demonstrated simple microhomology-mediated rearrangements suggestive of replication-based duplication events. Intriguingly, in a single family, the duplication was generated through nonallelic homologous recombination (NAHR) with the use of HUWE1-flanking imperfect low-copy repeats, which drive this infrequent NAHR event. The recurrent partial HUWE1 copy-number gain was also generated through NAHR, but here, the homologous sequences used were identified as TcMAR-Tigger DNA elements, a template that has not yet been reported for NAHR. In summary, we showed that an increased dosage of HUWE1 causes nonsyndromic ID and demonstrated that the Xp11.22 region is prone to recombination- and replication-based rearrangements.     

High photosynthetic capacity of Sahelian C3 and C4 plants

Photosynthesis Research - The semi-arid ecosystems of the African Sahel play an important role in the global carbon cycle and are among the most sensitive ecosystems to future environmental...     

Cytotoxic T lymphocyte lysis of HTLV-1 infected cells is limited by weak HBZ protein expression,but non-specifically enhanced on induction of Tax expression

Background

Immunogenetic evidence indicates that cytotoxic T lymphocytes (CTLs) specific for the weak CTL antigen HBZ limit HTLV-1 proviral load in vivo, whereas there is no clear relationship between the proviral load and the frequency of CTLs specific for the immunodominant antigen Tax. In vivo, circulating HTLV-1-infected cells express HBZ mRNA in contrast, Tax expression is typically low or undetectable. To elucidate the virus-suppressing potential of CTLs targeting HBZ, we compared the ability of HBZ- and Tax-specific CTLs to lyse naturally-infected cells, by co-incubating HBZ- and Tax-specific CTL clones with primary CD4⁺ T cells from HLA-matched HTLV-1-infected donors. We quantified lysis of infected cells, and tested whether specific virus-induced host cell surface molecules determine the susceptibility of infected cells to CTL-mediated lysis.

Results

Primary infected cells upregulated HLA-A*02, ICAM-1, Fas and TRAIL-R1/2 in concert with Tax expression, forming efficient targets for both HTLV-1-specific CTLs and CTLs specific for an unrelated virus. We detected expression of HBZ mRNA (spliced isoform) in both Tax-expressing and non-expressing infected cells, and the HBZ_26–34 epitope was processed and presented by cells transfected with an HBZ expression plasmid. However, when coincubated with primary cells, a high-avidity HBZ-specific CTL clone killed significantly fewer infected cells than were killed by a Tax-specific CTL clone. Finally, incubation with Tax- or HBZ-specific CTLs resulted in a significant decrease in the frequency of cells expressing high levels of HLA-A*02.

Conclusions

HTLV-1 gene expression in primary CD4⁺ T cells non-specifically increases susceptibility to CTL lysis. Despite the presence of HBZ spliced-isoform mRNA, HBZ epitope presentation by primary cells is significantly less efficient than that of Tax.