Introduction: Several studies reported on the humoral response in subjects having received the BNT162b2 mRNA COVID-19 vaccine. However, data on the kinetics of antibodies 3 months postvaccination are currently lacking and are important to drive the future vaccination strategy. Methods:The CRO-VAX HCP study is an ongoing multicenter, prospective and interventional study designed to assess the antibody response in a population of healthcare professionals who had received two doses of the BNT162b2 mRNA COVID-19 vaccine. Two-hundred individuals underwent a blood drawn within 2 days before the first vaccine dose. One-hundred and forty-two persons (71%)were categorized as seronegative at baseline while 58 (29%) were seropositive. Samples were then collected after 14, 28, 42, 56, and 90 days. Antibodies against the SARS-CoV-2 nucleocapsid and the receptor binding domain of the S1 subunit of the spike protein were measured in all individuals at different time points.Results: Using a one-compartment kinetics model, the time to maximum concentration was estimated at 36 ± 3 days after the first dose and the estimated half-life of antibodies was 55 days (95% CI: 37-107 days) in seronegative participants. In seropositive participants, the time to maximum concentration was estimated at 24 ± 4 days and the estimated half-life was 80 days (95% CI: 46-303 days). The antibody response was higher in seropositive compared to seronegative participants. Conclusion:In both seropositive and seronegative subjects, a significant antibody decline was observed at 3 months compared to the peak response. Nevertheless, the humoral response remained robust in all participants.

SummaryPhagocytosis of human cells is a crucial activity for the virulence of the human parasite Entamoeba histolytica . This protozoan invades and destroys the intestine by killing and phagocytosing epithelial cells, erythrocytes and cells from the immune system. In this study, we used magnetic beads covered with proteins from human serum as a model system to study the early events involved in phagocytosis by E. histolytica . We validated the system showing that the beads uptake triggered the activation of the actinmyosin cytoskeleton and involved a PI3-kinase as previously described for erythrophagocytosis. We purified early phagosomes from wild-type (WT) amoeba and from parasites that overproduced myosin IB (MyoIB + + + + ), the unique unconventional myosin of E. histolytica . The MyoIB + + + + cells exhibit a slower and more synchronized uptake process than the WT strain. Proteomic analysis by liquid chromatography and tandem mass spectroscopy (LC-MS/MS) of the WT and MyoIB + + + + phagosomes allowed us to identify, for the first time, molecular actors involved in the early step of the uptake process. These include proteins involved in cytoskeleton activity, signalling, endocytosis, lytic activity and cell surface proteins. Interestingly, the proteins that we found specifically recruited on the phagosomes from the MyoIB + + + + strain were previously described in other eukarytotic cells, as involved in the regulation of cortical F-actin dynamics, such as a a a a -actinin and formins. This proteomics approach allows a step further towards the understanding of the molecular mechanisms involved in phagocytosis in E. histolytica that revealed some interesting differences compared with phagocytosis in macrophages or Dictyostelium discoideum , and allowed to identify putative candidates for proteins linked to myosin IB activity during the phagocytic process

Data about the long-term duration of antibodies after SARS-CoV-2 vaccination are still scarce and are important to design vaccination strategies. In this study, 231 healthcare professionals received the two-dose regimen of BNT162b2. Of these, 158 were seronegative and 73 were seropositive at baseline. Samples were collected at several time points. The neutralizing antibodies (NAbs) and antibodies against the nucleocapsid and the spike protein of SARS-CoV-2 were measured. At day 180, a significant antibody decline was observed in seronegative (−55.4% with total antibody assay; −89.6% with IgG assay) and seropositive individuals (−74.8% with total antibody assay; −79.4% with IgG assay). The estimated half-life of IgG from the peak humoral response was 21 days (95% CI: 13–65) in seronegative and 53 days (95% CI: 40–79) in seropositive individuals. The estimated half-life of total antibodies was longer and ranged from 68 days (95% CI: 54–90) to 114 days (95% CI: 87–167) in seropositive and seronegative individuals, respectively. The decline of NAbs was more pronounced (−98.6%) and around 45% of the subjects tested were negative at day 180. Whether this decrease correlates with an equivalent drop in the clinical effectiveness against the virus would require appropriate clinical studies.

Following transmission to the vertebrate host, the protozoan parasite Leishmania donovani differentiates into the pathogenic amastigote stage that is adapted for intracellular survival. This developmental transition is induced by environmental factors including elevated temperature and acidic pH and is likely transduced by signaling cascades involving protein kinases and their downstream phosphoprotein substrates. These signaling networks are highly adapted to the specific nutritional and physiological requirements of the organism and thus studying Leishmania phosphorylation may allow important insight into the parasite-specific biology. We used a gel-based approach to investigate qualitative and quantitative changes of the phosphoproteome of the major L. donovani life cycle stages. Phosphoproteins were purified by immobilized metal affinity chromatography (IMAC), separated by IEF and SDS-PAGE using pH 4-7 IPG immobiline strips, revealed by fluorescent multiplex staining, and identified by MALDI-MS and MS/MS. Our analysis allowed us to establish a first repertoire of the Leishmania phosphoproteome and to identify phosphoproteins implicated in stress- and heat shock response, RNA/protein turnover, metabolism, and signaling.

The separation of the 2 ESX-1-connected phenotypes (ie, EsxA/B secretion and virulence) indicates that EsxA/B secretion is not the only readout for a functional ESX-1 system and suggests that other processes involving EspF/G(1) also play important roles in ESX-1-mediated pathogenicity.