A prospective humoral immune monitoring study of kidney transplant recipients receiving three doses of SARS-CoV-2 mRNA vaccine.

Kidney transplant recipients (KTRs), like other solid organ transplant recipients display a suboptimal response to mRNA vaccines, with only about half achieving seroconversion after two doses. However, the effectiveness of a booster dose, particularly in generating neutralizing antibodies (NAbs), remains poorly understood, as most studies have mainly focused on non-neutralizing antibodies. Here, we have longitudinally assessed the humoral response to the SARS-CoV-2 mRNA vaccine in 40 KTRs over a year, examining changes in both anti-spike IgG and NAbs following a booster dose administered about 5 months post-second dose. We found a significant humoral response increase 5 months post-booster, a stark contrast to the attenuated response observed after the second dose. Of note, nearly a quarter of participants did not achieve protective plasma levels even after the booster dose. We also found that the higher estimated glomerular filtration rate (eGFR) correlated with a more robust humoral response postvaccination. Altogether, these findings underscore the effectiveness of the booster dose in enhancing durable humoral immunity in KTRs, as evidenced by the protective level of NAbs found in 65% of the patients 5 months post- booster, especially those with higher eGFR rates.

Clodronate Reduces ATP-Containing Microvesicle Releasing Induced by Nociceptive Stimuli in Human Keratinocytes.

Clodronate (Clod), a first-generation bisphosphonate, acts as a natural analgesic inhibiting vesicular storage of the nociception mediator ATP by vesicular nucleotide transporter (VNUT). Epidermal keratinocytes participate in cutaneous nociception, accumulating ATP within vesicles, which are released following different stimulations. Under stress conditions, keratinocytes produce microvesicles (MVs) by shedding from plasma membrane evagination. MV secretion has been identified as a novel and universal mode of intercellular communication between cells. The aim of this project was to evaluate if two nociceptive stimuli, Capsaicin and Potassium Hydroxide (KOH), could stimulate MV shedding from human keratinocytes, if these MVs could contain ATP, and if Clod could inhibit this phenomenon. In our cellular model, the HaCaT keratinocyte monolayer, both Capsaicin and KOH stimulated MV release after 3 h incubation, and the released MVs contained ATP. Moreover, Clod (5 µM) was able to reduce Caps-induced MV release and abolish the one KOH induced, while the Dansylcadaverine, an endocytosis inhibitor of Clod uptake, partially failed to block the bisphosphonate activity. Based on these new data and given the role of the activation of ATP release by keratinocytes as a vehicle for nociception and pain, the "old" bisphosphonate Clodronate could provide the pharmacological basis to develop new local analgesic drugs.

Human cytomegalovirus infection triggers a paracrine senescence loop in renal epithelial cells.

Human cytomegalovirus (HCMV) is an opportunistic pathogen causing severe diseases in immunosuppressed individuals. To replicate its double-stranded DNA genome, HCMV induces profound changes in cellular homeostasis that may resemble senescence. However, it remains to be determined whether HCMV-induced senescence contributes to organ-specific pathogenesis. Here, we show a direct cytopathic effect of HCMV on primary renal proximal tubular epithelial cells (RPTECs), a natural setting of HCMV disease. We find that RPTECs are fully permissive for HCMV replication, which endows them with an inflammatory gene signature resembling the senescence-associated secretory phenotype (SASP), as confirmed by the presence of the recently established SenMayo gene set, which is not observed in retina-derived epithelial (ARPE-19) cells. Although HCMV-induced senescence is not cell-type specific, as it can be observed in both RPTECs and human fibroblasts (HFFs), only infected RPTECs show downregulation of LAMINB1 and KI67 mRNAs, and enhanced secretion of IL-6 and IL-8, which are well-established hallmarks of senescence. Finally, HCMV-infected RPTECs have the ability to trigger a senescence/inflammatory loop in an IL-6-dependent manner, leading to the development of a similar senescence/inflammatory phenotype in neighboring uninfected cells. Overall, our findings raise the intriguing possibility that this unique inflammatory loop contributes to HCMV-related pathogenesis in the kidney.