Volpe, E. | bioRxiv Science

bioRxiv2022

A short ERAP2 that binds IRAP is expressed in macrophages independently from gene variation

The M1 zinc metalloproteases ERAP1, ERAP2 and IRAP play a role in HLA-I antigen presentation by refining the peptidome either in the ER (ERAP1 and ERAP2) or in the endosomes (IRAP). They have been also entrusted with other, although less defined, functions such as the regulation of the angiotensin system and blood pressure. In humans, ERAP1 and IRAP are commonly expressed. ERAP2 instead has evolved under balancing selection that maintains two haplotypes one of which undergoing RNA splicing leading to nonsense-mediated decay and loss of protein. Hence, likewise in rodents in which the ERAP2 gene is missing, about a quarter of the human population does not express ERAP2. We report here that macrophages, but not monocytes or other mononuclear blood cells, express and secrete an ERAP2 shorter form independently from the haplotype. The generation of this "short" ERAP2 is due to an autocatalytic cleavage within a distinctive structural motif and requires an acidic microenvironment. Remarkably, ERAP2 "short" binds IRAP and the two molecules are co-expressed in the endosomes as well as in the cell membrane. Of note, the same phenomenon could be observed in some cancer cells. These data prompt to reconsider the role of ERAP2 which might have been maintained in humans because fulfilling a relevant function as "short" form in specialized cells.

biochemistry↗

bioRxiv2021

Preserved T cell reactivity to the SARS-CoV-2 Omicron variant indicates continued protection in vaccinated individuals.

ImportanceThe emergence of the highly contagious Omicron variant of SARS-CoV-2 and the findings of a significantly reduced neutralizing potency of sera from convalescent or vaccinated individuals imposes the study of cellular immunity to predict the degree of immune protection to the yet again new coronavirus. DesignProspective monocentric observational study. SettingConducted between December 20-21 at the Santa Lucia Foundation IRCCS. Participants61 volunteers (Mean age 41.62, range 21-62; 38F/23M) with different vaccination and SARS-CoV-2 infection backgrounds donated 15 ml of blood. Of these donors, one had recently completed chemotherapy, and one was undergoing treatment with monoclonal antibodies; the others reported no known health issue. Main Outcome(s) and Measure(s)The outcomes were the measurement of T cell reactivity to the mutated regions of the Spike protein of the Omicron SARS-CoV-2 variant and the assessment of remaining T cell immunity to the spike protein by stimulation with peptide libraries. ResultsLymphocytes from freshly drawn blood samples were isolated and immediately tested for reactivity to the Spike protein of SARS-CoV-2. T cell responses to peptides covering the mutated regions in the Omicron variant were decreased by over 47% compared to the same regions of the ancestral vaccine strain. However, overall reactivity to the peptide library of the full-length protein was largely maintained (estimated 83%). No significant differences in loss of immune recognition were identified between groups of donors with different vaccination and/or infection histories. Conclusions and RelevanceWe conclude that despite the mutations in the Spike protein, the SARS-CoV-2 Omicron variant is nonetheless recognized by the cellular component of the immune system. It is reasonable to assume that protection from hospitalization and severe disease is maintained. Key PointsO_ST_ABSQuestionC_ST_ABSDoes the Omicron variant of SARS-CoV-2 escape cellular immunity? FindingsThis observational study was performed on 61 vaccinated donors with established immunity to SARS-CoV-2. Cellular responses to the mutated regions of the Omicron Spike protein were detected in 80% of donors. The mutations reduced T cell recognition by 47% compared to the vaccine strain. Reactivity to the whole Spike protein, however, was present in 100% of donors, and the fraction of remaining immunity to SARS-CoV-2 was estimated to be 83%. MeaningCellular immunity to the Omicron variant is maintained despite the mutations in its Spike protein, and may thus confer protection from severe COVID-19 in vaccinated individuals.

immunology↗