The extended N-terminal region of SphS is required for detection of external phosphate levels in Synechocystis sp. PCC 6803

A novel 47 amino acid extension at the N-terminus of the SphS histidine kinase has been identified in the cyanobacterium Synechocystis sp. PCC 6803. Here, we demonstrate this region is required for activation of the SphS-SphR phosphate-sensing two-component system under phosphate-limiting conditions and mutants lacking this extension do not show constitutive alkaline phosphatase activity when the negative regulator SphU is inactivated. We have also identified a putative membrane-associated domain within this region involved in control of the Pho regulon. In addition, there are two high-affinity ABC-type phosphate uptake systems in this organism. Our results demonstrate that the Pst1 system, but not the Pst2 system, is required for suppression of the Pho regulon under phosphate-sufficient conditions. Deletion of the pst1 operon and disruption of the membrane-spanning domain may both target the same control mechanism since constitutive alkaline phosphatase activity is similar in the double and single mutants.     

Towards a Science of Community Stakeholder Engagement in Biomedical HIV Prevention Trials: An Embedded Four-Country Case Study

Objectives

Broad international guidelines and studies in the context of individual clinical trials highlight the centrality of community stakeholder engagement in conducting ethically rigorous HIV prevention trials. We explored and identified challenges and facilitators for community stakeholder engagement in biomedical HIV prevention trials in diverse global settings. Our aim was to assess and deepen the empirical foundation for priorities included in the GPP guidelines and to highlight challenges in implementation that may merit further attention in subsequent GPP iterations.

Methods

From 2008–2012 we conducted an embedded, multiple case study centered in Thailand, India, South Africa and Canada. We conducted in-depth interviews and focus groups with respondents from different trial-related subsystems: civil society organization representatives, community advocates, service providers, clinical trialists/researchers, former trial participants, and key HIV risk populations. Interviews/focus groups were recorded, and coded using thematic content analysis. After intra-case analyses, we conducted cross-case analysis to contrast and synthesize themes and sub-themes across cases. Lastly, we applied the case study findings to explore and assess UNAIDS/AVAC GPP guidelines and the GPP Blueprint for Stakeholder Engagement.

Results

Across settings, we identified three cross-cutting themes as essential to community stakeholder engagement: trial literacy, including lexicon challenges and misconceptions that imperil sound communication; mistrust due to historical exploitation; and participatory processes: engaging early; considering the breadth of “community”; and, developing appropriate stakeholder roles. Site-specific challenges arose in resource-limited settings and settings where trials were halted.

Conclusions

This multiple case study revealed common themes underlying community stakeholder engagement across four country settings that largely mirror GPP goals and the GPP Blueprint, as well as highlighting challenges in the implementation of important guidelines. GPP guidance documents could be strengthened through greater focus on: identifying and addressing the community-specific roots of mistrust and its impact on trial literacy activities; achieving and evaluating representativeness in community stakeholder groups; and addressing the impact of power and funding streams on meaningful engagement and independent decision-making.     

Antibody germline characterization of cross-neutralizing human IgGs against 4 serotypes of dengue virus

Dengue virus (DENV), a re-emerging virus, constitutes the largest vector-borne disease virus, with 50–100 million cases reported every year. Although DENV infection induces lifelong immunity against viruses of the same serotypes, the subsequent infection with the heterologous serotypes can cause more severe form of the disease, such as Dengue Haemorrhagic Fever (DHF) or Dengue Shock Syndrome (DSS). However, there is neither approved vaccine nor specific drugs available to treat this disease. In this study, previously developed 19 human monoclonal antibodies (HuMAbs) showing strong to moderate cross neutralizing activity were selected. Most of them (13/19) were targeted to domain II of envelop glycoprotein. To understand and clarify the recognition properties, the maturation mechanisms comprising Variable/Diversity/Joining (VDJ) recombination, Variable Heavy (VH)/Variable Light (VL) chain pairing, variability at junctional site, and somatic hypermutation (SHM) of those antibodies were studied and compared with their predecessor germline sequences. IMGT/V-QUEST database was applied to analyze the isolated VH and VL sequences. To confirm the correction of isolated VH/VL, 3 HuMAbs (1A10H7, 1B3B9, 1G7C2) was transiently expressed in HEK293T cell. All three clones of the expressed recombinant IgG (rIgG) showed the same binding and neutralizing activity as same as those from hybridomas. The data obtained in this study will elucidate the properties of those HuMAbs for further genetic modification, and its binding epitopes.