ATP-P2X7R pathway activation limits the Tfh cell compartment during pediatric RSV infection.

Background: Follicular helper T cells (Tfh) are pivotal in B cell responses. Activation of the purinergic receptor P2X7 on Tfh cells regulates their activity. We investigated the ATP-P2X7R axis in circulating Tfh (cTfh) cells during Respiratory Syncytial Virus (RSV) infection. Methods: We analyzed two cohorts: children with RSV infection (moderate, n=30; severe, n=21) and healthy children (n=23). We utilized ELISA to quantify the levels of PreF RSV protein-specific IgG antibodies, IL-21 cytokine, and soluble P2X7R (sP2X7R) in both plasma and nasopharyngeal aspirates (NPA). Additionally, luminometry was employed to determine ATP levels in plasma, NPA and supernatant culture. The frequency of cTfh cells, P2X7R expression, and plasmablasts were assessed by flow cytometry. To evaluate apoptosis, proliferation, and IL-21 production by cTfh cells, we cultured PBMCs in the presence of Bz-ATP and/or P2X7R antagonist (KN-62) and a flow cytometry analysis was performed. Results: In children with severe RSV disease, we observed diminished titers of neutralizing anti-PreF IgG antibodies. Additionally, severe infections, compared to moderate cases, were associated with fewer cTfh cells and reduced plasma levels of IL-21. Our investigation revealed dysregulation in the ATP-P2X7R pathway during RSV infection. This was characterized by elevated ATP levels in both plasma and NPA samples, increased expression of P2X7R on cTfh cells, lower levels of sP2X7R, and heightened ATP release from PBMCs upon stimulation, particularly evident in severe cases. Importantly, ATP exposure decreased cTfh proliferative response and IL-21 production, while promoting their apoptosis. The P2X7R antagonist KN-62 mitigated these effects. Furthermore, disease severity positively correlated with ATP levels in plasma and NPA samples and inversely correlated with cTfh frequency. Conclusion: Our findings indicate that activation of the ATP-P2X7R pathway during RSV infection may contribute to limiting the cTfh cell compartment by promoting cell death and dysfunction, ultimately leading to increased disease severity.

Multilocus sequence typing of Treponema pallidum pallidum in children with acquired syphilis by nonsexual contact.

Background: There are scarce data of Treponema pallidum subsp. pallidum (TPA) characterization in children with syphilis. Nonsexually acquired transmission (NSAT) of TPA is possible in infants through close contact. Methods: A descriptive study in five families with NSAT of syphilis was conducted. Polymerase chain reaction detection of TPA in pediatric index cases (n = 6) and their relatives (n = 44) were conducted followed by multilocus sequence typing (MLST). Results: TPA was detected in swab samples in 16 cases and 12 were characterized by MLST. Nichols lineage was identified in two of five families and SS14-lineage in three of five. In four families, MLST profiles linked index cases to relatives. Conclusion: This is the first report of TPA characterization in children infected by NSAT.

Syphilis is a disease caused by the bacterium Treponema pallidum subsp. pallidum (TPA). Although it is considered a sexually transmitted disease, syphilis can also be transmitted by nonsexual close contact with active lesions. There are clinical reports of this route of transmissions in children; however, there are no molecular characterizations of TPA in this population. A multidisciplinary study (epidemiological, clinical, social and molecular) was performed in six children from five families with clinical diagnosis of nonsexually transmitted syphilis. As a result, 18 infected persons were detected. In 16 individuals the presence of the bacterium genetic material was confirmed by molecular biology techniques, and in 12, its strain was analyzed. When we compared the data, we observed that in four families, the child's strain coincided with the one found in close contact, while in one family, this could not be determined. To our knowledge, this is the first report of TPA characterization in children, which underscore the importance of including molecular biology techniques in complex clinical scenarios such as these.