Asy2/Mer2: an evolutionarily conserved mediator of meiotic recombination, pairing, and global chromosome compaction.

Meiosis is the cellular program by which a diploid cell gives rise to haploid gametes for sexual reproduction. Meiotic progression depends on tight physical and functional coupling of recombination steps at the DNA level with specific organizational features of meiotic-prophase chromosomes. The present study reveals that every step of this coupling is mediated by a single molecule: Asy2/Mer2. We show that Mer2, identified so far only in budding and fission yeasts, is in fact evolutionarily conserved from fungi (Mer2/Rec15/Asy2/Bad42) to plants (PRD3/PAIR1) and mammals (IHO1). In yeasts, Mer2 mediates assembly of recombination-initiation complexes and double-strand breaks (DSBs). This role is conserved in the fungus Sordaria However, functional analysis of 13 mer2 mutants and successive localization of Mer2 to axis, synaptonemal complex (SC), and chromatin revealed, in addition, three further important functions. First, after DSB formation, Mer2 is required for pairing by mediating homolog spatial juxtaposition, with implications for crossover (CO) patterning/interference. Second, Mer2 participates in the transfer/maintenance and release of recombination complexes to/from the SC central region. Third, after completion of recombination, potentially dependent on SUMOylation, Mer2 mediates global chromosome compaction and post-recombination chiasma development. Thus, beyond its role as a recombinosome-axis/SC linker molecule, Mer2 has important functions in relation to basic chromosome structure.

Association of soluble CD14 and inflammatory biomarkers with HIV-2 disease progression.

BACKGROUND: Human immunodeficiency virus type 2 (HIV-2) infection is characterized by a slower progression than HIV type 1. It is not known whether markers of inflammation such as high-sensitivity C-reactive protein (hsCRP), interleukin 6 (IL-6), and soluble CD14 (sCD14) may predict disease progression among HIV-2 patients. METHODS: We performed longitudinal retrospective analysis using 384 samples from 71 patients included in the HIV-2 French cohort ANRS CO5 and followed for a median of 8 years. Baseline was the time of the first available measurement. Disease progression was defined by the occurrence of death, Centers for Disease Control and Prevention B/C stage HIV-related event, drop in CD4 <350 cells/µL, and HIV-2 RNA detection. Cox regression models and mixed models were used for statistical analyses. RESULTS: At baseline, 75% of patients were asymptomatic, 34% were treated; 30% had detectable HIV-2 RNA load, and median CD4 cell count was 415/µL. The 3 biomarkers were positively related to each other. In adjusted analyses, sCD14 was the main factor explaining variation of hsCRP and IL-6 (P < .001). Lower CD4, older age, and advanced clinical stage were associated with higher sCD14. The biomarkers were correlated with HIV-2 RNA in unadjusted analyses only. Patients with baseline levels above either the median values (hsCRP = 1.38 mg/L; IL-6 = 1.97 pg/mL) or the highest quartile (sCD14 = 1.74 µg/mL) had a higher risk of disease progression (all P < .003). After adjustment for CD4 count, only sCD14 remained significantly associated with disease progression (hazard ratio, 3.59; P = .004). CONCLUSIONS: In this cohort of HIV-2-infected patients, sCD14 represents a better predictive biomarker of disease progression than hsCRP or IL-6, independent of CD4.

In vitro phenotypic susceptibility of HIV-2 clinical isolates to CCR5 inhibitors.

HIV-2 is naturally resistant to nonnucleoside reverse transcriptase inhibitors, to a fusion inhibitor, and to some of the protease inhibitors. Maraviroc is the first drug of the new anti-CCR5 drug class and is effective only on CCR5-tropic (R5) HIV-1. No previous studies concerning HIV-2 susceptibility to maraviroc have been reported yet. We developed a phenotypic maraviroc susceptibility test using a peripheral blood mononuclear cell (PBMC) model. We analyzed the maraviroc susceptibility of 13 R5 HIV-2, 2 X4R5 (dual) HIV-2, and 2 CXCR4-tropic (X4) HIV-2 clinical isolates. We also tested, with the same protocol, 1 X4 HIV-1 and 4 R5 HIV-1 clinical isolates. For the R5 HIV-2 clinical isolates, the 50% effective concentration (EC(50)) for maraviroc was 0.80 nM (interquartile range [IQR], 0.48 to 1.39 nM), similar to that observed for the R5 HIV-1 isolates. The median maximum percentage of inhibition in the R5 HIV-2 isolates was 93% (IQR, 84 to 98%), similar to that observed in the R5 HIV-1 isolates. As expected, both X4 HIV-1 and HIV-2 were highly resistant to maraviroc. Our study showed for the first time that maraviroc is active in vitro against R5 HIV-2. The new tools we developed will allow identification of HIV-2-infected patients eligible for CCR5 inhibitor use and management of virological failure when receiving a maraviroc-based regimen.