Diabetic foot ulcers (DFUs) are major complications of Diabetes mellitus being responsible for significant morbidity and mortality. DFUs frequently become chronically infected by a complex community of bacteria, including multidrug-resistant and biofilm-producing strains of Staphylococcus aureus and Pseudomonas aeruginosa. Diabetic foot infections (DFI) are often recalcitrant to conventional antibiotics and alternative treatment strategies are urgently needed. Antimicrobial Peptides (AMPs), such as pexiganan and nisin, have been increasingly investigated and reported as effective antimicrobial agents. Here, we evaluated the antibacterial potential of pexiganan and nisin used in combination (dual-AMP) to control the growth of planktonic and biofilm co-cultures of S. aureus and P. aeruginosa clinical strains, co-isolated from a DFU. A DFU collagen three-dimensional (3D) model was used to evaluate the distribution and efficacy of AMPs locally delivered into the model. The concentration of pexiganan required to inhibit and eradicate both planktonic and biofilm-based bacterial cells was substantially reduced when used in combination with nisin. Moreover, incorporation of both AMPs in a guar gum delivery system (dual-AMP biogel) did not affect the dual-AMP antimicrobial activity. Importantly, the application of the dual-AMP biogel resulted in the eradication of the S. aureus strain from the model. In conclusion, data suggest that the local application of the dual-AMPs biogel constitutes a potential complementary therapy for the treatment of infected DFU.

Viremia is significantly lower in HIV-2 than in HIV-1 infection, irrespective of disease stage. Nevertheless, the comparable proviral DNA burdens observed for these two infections indicate similar numbers of infected cells. Here we investigated this apparent paradox by assessing cell-associated viral replication. We found that untreated HIV-1-positive (HIV-1⁺) and HIV-2⁺individuals, matched for CD4 T cell depletion, exhibited similargagmRNA levels, indicating that significant viral transcription is occurring in untreated HIV-2⁺patients, despite the reduced viremia (undetectable to 2.6 × 10⁴RNA copies/ml). However,tatmRNA transcripts were observed at significantly lower levels in HIV-2⁺patients, suggesting that the rate ofde novoinfection is decreased in these patients. Our data also reveal a direct relationship ofgagandtattranscripts with CD4 and CD8 T cell activation, respectively. Antiretroviral therapy (ART)-treated HIV-2⁺patients showed persistent viral replication, irrespective of plasma viremia, possibly contributing to the emergence of drug resistance mutations, persistent hyperimmune activation, and poor CD4 T cell recovery that we observed with these individuals. In conclusion, we provide here evidence of significant ongoing viral replication in HIV-2⁺patients, further emphasizing the dichotomy between amount of plasma virus and cell-associated viral burden and stressing the need for antiretroviral trials and the definition of therapeutic guidelines for HIV-2 infection.

Plasmacytoid dendritic cells (pDC) provide an important link between innate and acquired immunity, mediating their action mainly through IFN-α production. pDC suppress HIV-1 replication, but there is increasing evidence suggesting they may also contribute to the increased levels of cell apoptosis and pan-immune activation associated with disease progression. Although having the same clinical spectrum, HIV-2 infection is characterized by a strikingly lower viremia and a much slower rate of CD4 decline and AIDS progression than HIV-1, irrespective of disease stage. We report here a similar marked reduction in circulating pDC levels in untreated HIV-1 and HIV-2 infections in association with CD4 depletion and T cell activation, in spite of the undetectable viremia found in the majority of HIV-2 patients. Moreover, the same overexpression of CD86 and PD-L1 on circulating pDC was found in both infections irrespective of disease stage or viremia status. Our observation that pDC depletion occurs in HIV-2 infected patients with undetectable viremia indicates that mechanisms other than direct viral infection determine the pDC depletion during persistent infections. However, viremia was associated with an impairment of IFN-α production on a per pDC basis upon TLR9 stimulation. These data support the possibility that diminished function in vitro may relate to prior activation by HIV virions in vivo, in agreement with our finding of higher expression levels of the IFN-α inducible gene, MxA, in HIV-1 than in HIV-2 individuals. Importantly, serum IFN-α levels were not elevated in HIV-2 infected individuals. In conclusion, our data in this unique natural model of “attenuated” HIV immunodeficiency contribute to the understanding of pDC biology in HIV/AIDS pathogenesis, showing that in the absence of detectable viremia a major depletion of circulating pDC in association with a relatively preserved IFN-α production does occur. Infection by HIV-2, the second AIDS-associated virus, is considered a unique natural model of attenuated HIV disease. HIV-2 infected individuals exhibit much lower levels of circulating virus (viremia) and progress to AIDS at slower rates than HIV-1 infected patients. In this study, we characterized for the first time blood plasmacytoid dendritic cells (pDC), important mediators between innate and acquired immunity, in HIV-2 infection. We observed a profound reduction in circulating pDC levels in HIV-2 infected patients, even in those with undetectable viremia, to levels similar to those found in HIV-1 infection. Moreover, we documented a more differentiated pDC phenotype in both infected cohorts relative to healthy individuals. Despite these similarities between HIV-1 and HIV-2 infections, pDC from HIV-2 patients with undetectable viremia exhibited, upon in vitro stimulation, a better-preserved ability to produce interferon-α (IFN-α), an important anti-viral cytokine with potential to stimulate other immune cells. Overall, our data suggest that the presence of virus in circulation, although not critical for the reduction in pDC number, appears to be central for the impairment of their function. This study of pDC in HIV-2 infection fills a gap in the understanding of their potential role in HIV/AIDS pathogenesis.

Haploidentical hematopoietic stem cell transplantation (HSCT) constitutes an important alternative for patients lacking a human leukocyte antigen (HLA)-matched donor. Although the use of haploidentical donors is increasingly common, the long-term impact of generating a donor-derived immune system in the context of an HLA-mismatched thymic environment remains poorly characterized. We performed an in-depth assessment of immune reconstitution in a group of haploidentical HSCT recipients 4 to 6 years posttransplantation, in parallel with the respective parental donors and age-matched healthy control subjects. Our data show that the proportion of naive and memory subsets in the recipients, both within CD8(+) and CD4(+) T cells, more closely resembled that observed in age-matched control subjects than in the donors. HSCT recipients displayed relatively high signal-joint T cell-receptor excision circle levels and a high frequency of the recent thymic emigrant-enriched CD31(+) subset within naive CD4(+) and naive regulatory T cells. Moreover, CD8(+), CD4(+), and regulatory T cells from HSCT recipients displayed a diverse T cell repertoire. These results support a key role for thymic output in T cell reconstitution. Nevertheless, HSCT recipients had significantly shorter telomeres within a naive-enriched CD4(+) T cell population than age-matched control subjects, despite the similar telomere length observed within the most differentiated CD8(+) and CD4(+) T cell subsets. Overall, our data suggest that long-term immune reconstitution was successfully achieved after haploidentical HSCT, a process that appears to have largely relied on de novo T cell production.