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Human leishmaniasis is facing important epidemiological changes in Southern Europe, driven by increased urbanization, climate changes, emerging of new animal reservoirs, shifts in human behavior and a growing population of immunocompromised and elderly individuals. In this evolving epidemiological landscape, we analyzed the clinical and epidemiological characteristics of human leishmaniasis in the Tuscany region of Central Italy. Through a multicentric retrospective analysis, we collected clinical and demographic data about all cases of leishmaniasis recorded between 2018 and 2023. We observed 176 cases of human leishmaniasis, with 128 (72.7%) visceral leishmaniasis (VL) and 47 (26.7%) cutaneous leishmaniasis (CL). Among these, 92.2% of VL and 85.1% of CL cases were autochthonous. The cumulative incidence of autochthonous human leishmaniasis was 0.22 cases per 100,000 inhabitants in 2018, but reached 1.81/100,000 in 2023. We identified three main areas of transmission: around the city of Florence (North-East Tuscany), around Grosseto city (South-West Tuscany) and Elba Island. Our findings confirm that the epidemiology of leishmaniasis is undergoing significant changes in Central Italy. Awareness towards this emerging health threat and surveillance strategies need to be improved in order to reliably assess the disease's burden. Further research is needed in a "One-Health" perspective, to clarify the epidemiological dynamics at the environmental, reservoir, vector and human levels. The role of climate change and specific climatic factors affecting the epidemiological patterns of human leishmaniasis should be assessed. Further knowledge in these fields would promote targeted control and prevention strategies at regional and national levels.

The severe acute respiratory syndrome coronavirus 2 variant JN.1 recently emerged as the dominant variant despite having only one amino acid change on the spike (S) protein receptor binding domain (RBD) compared with the ancestral BA.2.86, which never represented more than 5% of global variants. To define at the molecular level the JN.1 ability to spread globally, we interrogated a panel of 899 neutralizing human monoclonal antibodies. Our data show that the single leucine-455-to-serine mutation in the JN.1 spike protein RBD unleashed the global spread of JN.1, likely occurring by elimination of more than 70% of the neutralizing antibodies mediated by IGHV3-53/3-66 germlines. However, the resilience of class 3 antibodies with low neutralization potency but strong Fc functions may explain the absence of JN.1 severe disease.

Non-structural protein 1 (Nsp1) represents one of the most crucial SARS-CoV-2 virulence factors by inhibiting the translation of host mRNAs and promoting their degradation. We selected naturally occurring virus lineages with specific Nsp1 deletions located at both the N- and C-terminus of the protein. Our data provide new insights into how Nsp1 coordinates these functions on host and viral mRNA recognition. Residues 82-85 in the N-terminal part of Nsp1 likely play a role in docking the 40S mRNA entry channel, preserving the inhibition of host gene expression without affecting cellular mRNA decay. Furthermore, this domain prevents viral mRNAs containing the 5'-leader sequence to escape translational repression. These findings support the presence of distinct domains within the Nsp1 protein that differentially modulate mRNA recognition, translation and turnover. These insights have implications for the development of drugs targeting viral proteins and provides new evidences of how specific mutations in SARS-CoV-2 Nsp1 could attenuate the virus.

Monoclonal antibodies (mAbs) are one of the most important classes of biologics with high therapeutic and diagnostic value, but traditional methods for mAbs generation, such as hybridoma screening and phage display, have limitations, including low efficiency and loss of natural chain pairing. To overcome these challenges, novel single B cell antibody technologies have emerged, but they also have limitations such as in vitro differentiation of memory B cells and expensive cell sorters. In this study, we present a rapid and efficient workflow for obtaining human recombinant monoclonal antibodies directly from single antigen-specific antibody secreting cells (ASCs) in the peripheral blood of convalescent COVID-19 patients using ferrofluid technology. This process allows the identification and expression of recombinant antigen-specific mAbs in less than 10 days, using RT-PCR to generate linear Ig heavy and light chain gene expression cassettes, called "minigenes", for rapid expression of recombinant antibodies without cloning procedures. This approach has several advantages. First, it saves time and resources by eliminating the need for in vitro differentiation. It also allows individual antigen-specific ASCs to be screened for effector function prior to recombinant antibody cloning, enabling the selection of mAbs with desired characteristics and functional activity. In addition, the method allows comprehensive analysis of variable region repertoires in combination with functional assays to evaluate the specificity and function of the generated antigen-specific antibodies. Our approach, which rapidly generates recombinant monoclonal antibodies from single antigen-specific ASCs, could help to identify functional antibodies and deepen our understanding of antibody dynamics in the immune response through combined antibody repertoire sequence analysis and functional reactivity testing., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Strazza, Rossi, Avati, Tiseo, Falcone, Cusi, Menichetti, Ricciardi-Castagnoli, Tinti and Pileri.)