Background Existing social relationships are a potential source of “social capital” that can enhance support for sustained retention in HIV care. A previous pilot study of a social network-based ‘microclinic’ intervention, including group health education and facilitated HIV status disclosure, reduced disengagement from HIV care. We conducted a pragmatic randomized trial to evaluate microclinic effectiveness. Methods In nine rural health facilities in western Kenya, we randomized HIV-positive adults with a recent missed clinic visit to either participation in a microclinic or usual care (NCT02474992). We collected visit data at all clinics where participants accessed care and evaluated intervention effect on disengagement from care (≥90-day absence from care after a missed visit) and the proportion of time patients were adherent to clinic visits (‘time-in-care’). We also evaluated changes in social support, HIV status disclosure, and HIV-associated stigma. Results Of 350 eligible patients, 304 (87%) enrolled, with 154 randomized to intervention and 150 to control. Over one year of follow-up, disengagement from care was similar in intervention and control (18% vs 17%, hazard ratio 1.03, 95% CI 0.61–1.75), as was time-in-care (risk difference -2.8%, 95% CI -10.0% to +4.5%). The intervention improved social support for attending clinic appointments (+0.4 units on 5-point scale, 95% CI 0.08–0.63), HIV status disclosure to close social supports (+0.3 persons, 95% CI 0.2–0.5), and reduced stigma (-0.3 units on 5-point scale, 95% CI -0.40 to -0.17). Conclusions The data from our pragmatic randomized trial in rural western Kenya are compatible with the null hypothesis of no difference in HIV care engagement between those who participated in a microclinic intervention and those who did not, despite improvements in proposed intervention mechanisms of action. However, some benefit or harm cannot be ruled out because the confidence intervals were wide. Results differ from a prior quasi-experimental pilot study, highlighting important implementation considerations when evaluating complex social interventions for HIV care. Trial registration Clinical trial number: NCT02474992.

We have characterized the structural determinants of phospholamban (PLB) and sarcolipin (SLN) self-association using site-directed mutagenesis, SDS-PAGE, and fluorescence resonance energy transfer (FRET) microscopy. PLB and SLN are single-pass transmembrane (TM) peptides that are critically involved in regulation of contractility in cardiac and skeletal muscle via reversible inhibition of calcium (Ca) transport by SERCA. PLB and SLN also exhibit ion channel activity in vitro, yet the physiological significance of these functions is unknown. Here we have determined that structural insights offered by the tetrameric PLB Cys41 to Leu (C41L) mutation, a mutant with four possible leucine/isoleucine zipper interactions for stabilizing PLB tetramers. Using scanning alanine mutagenesis and SDS-PAGE, we have determined the C41L-PLB tetramer is destabilized by mutation of Leu37 to Ala (L37A) or Ile40 to Ala (I40A), which are the same a-and d-arm residues stabilizing the PLB pentamer via leucine/isoleucine zippers, highlighting the importance of these two zippers in PLB higher-order oligomerization. The new possible zipper arm in C41L-PLB (N34, C41L, I48) did not contribute to tetramerization. On the other hand, we determined that tetramer conversion back to pentamer was induced by alanine mutation of Ile48, a residue located on the e-arm below C41L, implicating steric interaction and restriction are the stabilizing and destabilizing forces that control the distribution between pentamer and tetramer populations. We propose that the e-arm and hydrophobic residues in the adjacent b-arm act as secondary structural motifs that help control the stoichiometry of PLB oligomerization. FRET microscopy and alanine mutagenesis of SLN residues Val14 (V14A) or Leu21 (L21A) decreased the binding affinity of the SLN-SLN complex, demonstrating the importance of each residue in mediating self-association. Helical wheel analysis supports a heptad-repeat TM zipper mechanism of SLN oligomerization, similar to the 3.5 residue/turn Leu and Ile zippers found in PLB pentamers. Collectively, our studies add new insights on the conservation of homologous hydrophobic 3-4 pattern of residues in zipper motifs that mediate PLB and SLN self-assembly. We propose that the importance of these apolar, steric interactions in the TM domain are widespread in stabilizing higher-order oligomerization of membrane proteins.Structural determinants of SLN and PLB self-association 2 1 Abbreviations and Acronyms: Amp, ampicillin; Ca, calcium; CAT; chloramphenicol acetyltransferase; CFP, cyan fluorescent protein; Cl -, chloride; DOPC, dioleoylphosphatidylcholine; ER, endoplasmic reticulum; FRET, fluorescence resonance energy transfer; his-CAT, chloramphenicol transferase with a 6-residue histidine tag fused to the N-terminus; his-PLB, phospholamban with a 6-residue histidine tag fused to the N-terminus; his-SLN, sarcolipin with a 6-residue histidine tag fused to the N-terminus; IPTG, isopropyl β-D-1-

No abstract

No abstract