IFITM3 restricts virus-induced inflammatory cytokine production by limiting Nogo-B mediated TLR responses.

Interferon-induced transmembrane protein 3 (IFITM3) is a restriction factor that limits viral pathogenesis and exerts poorly understood immunoregulatory functions. Here, using human and mouse models, we demonstrate that IFITM3 promotes MyD88-dependent, TLR-mediated IL-6 production following exposure to cytomegalovirus (CMV). IFITM3 also restricts IL-6 production in response to influenza and SARS-CoV-2. In dendritic cells, IFITM3 binds to the reticulon 4 isoform Nogo-B and promotes its proteasomal degradation. We reveal that Nogo-B mediates TLR-dependent pro-inflammatory cytokine production and promotes viral pathogenesis in vivo, and in the case of TLR2 responses, this process involves alteration of TLR2 cellular localization. Nogo-B deletion abrogates inflammatory cytokine responses and associated disease in virus-infected IFITM3-deficient mice. Thus, we uncover Nogo-B as a driver of viral pathogenesis and highlight an immunoregulatory pathway in which IFITM3 fine-tunes the responsiveness of myeloid cells to viral stimulation.

Natural polymorphisms of HIV-1 subtype-C integrase coding region in a large group of ARV-naïve infected individuals.

PURPOSE: Integrase (IN) is an enzyme produced by human immunodeficiency virus (HIV)-1 that enables its genetic material to be integrated into the DNA of the infected cell. Still now, few data are available with detailed analysis of the natural IN polymorphisms of HIV-1 subtype-C in datasets retrieved from antiretroviral-naïve patients; this study focuses on these polymorphisms. METHODS: The analysis included 335 HIV-1 subtype-C IN sequences (one per patient). Multi-alignment of IN sequences was performed, and for the definition of a polymorphism, only amino acid changes with prevalence ≥3 % among treatment-naïve patients were considered. RESULTS: Seventy IN amino acid positions were fully conserved. Differently, forty-six IN amino acid polymorphic positions were observed, 12 within the N-terminal domain and 13 within the C-terminal domain. In the DDE-catalytic motif, only one mutation per site (D64G/D116G/E152K) was found, while a low variability (<1 %) was observed for IN positions interacting with LEDGF/p75. A major drug resistance mutation for raltegravir (RAL) and elvitegravir (EVG), Q148H, was retrieved from one patient and another RAL primary resistance mutation, Y143H, was also retrieved from another patient. CONCLUSIONS: The results from the IN sequences analyzed underlined that some unexpected baseline substitutions affecting the susceptibility to RAL/EVG could be detected in drug-naïve individuals, and, therefore, it should be genotyped before the consideration of HIV-1 IN inhibitors (INIs). The impact of these mutations on the baseline drug susceptibility of HIV-1 subtype-C to INIs may need to be addressed prior to the introduction of these drugs in some Asiatic and African countries.

Molecular analysis based on mtLSU-rRNA and DHPS sequences of Pneumocystis jirovecii from immunocompromised and immunocompetent patients in Italy.

Pneumocystis jirovecii is an opportunistic fungus predominantly reported in immunocompromised individuals, who develop severe interstitial pneumonia (PcP). However, it is known that asymptomatic or mild pulmonary infections, defined as colonization, are widely observed in the general adult population. So far, genetic and epidemiological data of P. jirovecii infections in Italy are rather scarce and limited to defined geographical regions, mainly regarding isolates from HIV-infected patients. The aim of this study was to evaluate the polymorphisms at the mtLSU-rRNA and the DHPS loci by the screening and genotyping of a cohort of patients from two major hospitals in Rome (Italy). The study included 263 patients divided into two groups, all enrolled consecutively from January 2006 to December 2010: (i) 38 immunocompromised subjects including 25 HIV-infected; (ii) 225 immunocompetent patients. Sixty-seven out of 263 patients (25.5%) were found positive after PCR amplification of the mtLSU-rRNA gene. Overall, genotyping at mtLSU-rRNA locus revealed that the genotype 2 was the most frequent. Sequences of the DHPS gene were obtained from 21 patients, 9 from immunocompromised patients (6 from HIV infected individuals), 12 from immunocompetent ones. Considering the most common DHPS mutations usually detected at amino acid positions 55 and 57 and potentially related to drug resistance, all samples analyzed showed the wild-type signatures. These are the first data in Italy on prevalence and genotypes of P. jirovecii regarding colonized immunocompetent adults. Further multicenter analyses on P. jirovecii infection will be necessary to better define the specific epidemiology of the disease in the Italian populations.