Higher plasma levels of thymosin-α1 are associated with a lower waning of humoral response after COVID-19 vaccination: an eight months follow-up study in a nursing home.

BACKGROUND: Older people achieve lower levels of antibody titers than younger populations after Covid-19 vaccination and show a marked waning humoral immunity over time, likely due to the senescence of the immune system. Nevertheless, age-related predictive factors of the waning humoral immune response to the vaccine have been scarcely explored. In a cohort of residents and healthcare workers from a nursing home that had received two doses of the BNT162b2 vaccine, we measured specific anti-S antibodies one (T1), four (T4), and eight (T8) months after receiving the second dose. Thymic-related functional markers, including thymic output, relative telomere length, and plasma thymosin-α1 levels, as well as immune cellular subsets, and biochemical and inflammatory biomarkers, were determined at T1, and tested for their associations with the magnitude of the vaccine response (T1) and the durability of such response both, at the short- (T1-T4) and the long-term (T1-T8). We aimed to identify age-related factors potentially associated with the magnitude and persistence of specific anti-S immunoglobulin G (IgG)-antibodies after COVID-19 vaccination in older people. RESULTS: Participants (100% men, n = 98), were subdivided into three groups: young (< 50 years-old), middle-age (50-65 years-old), and older (≥65 years-old). Older participants achieved lower antibody titers at T1 and experienced higher decreases in both the short- and long-term. In the entire cohort, while the magnitude of the initial response was mainly associated with the levels of homocysteine [ß (95% CI); - 0.155 (- 0.241 to - 0.068); p = 0.001], the durability of such response at both, the short-term and the long-term were predicted by the levels of thymosin-α1 [- 0.168 (- 0.305 to - 0.031); p = 0.017, and - 0.123 (- 0.212 to - 0.034); p = 0.008, respectively]. CONCLUSIONS: Higher plasma levels of thymosin-α1 were associated with a lower waning of anti-S IgG antibodies along the time. Our results suggest that plasma levels of thymosin-α1 could be used as a biomarker for predicting the durability of the responses after COVID-19 vaccination, possibly allowing to personalize the administration of vaccine boosters.

Factors associated with the humoral response after three doses of COVID-19 vaccination in kidney transplant recipients.

Introduction: Kidney transplant recipients showed a weak humoral response to the mRNA COVID-19 vaccine despite receiving three cumulative doses of the vaccine. New approaches are still needed to raise protective immunity conferred by the vaccine administration within this group of high-risk patients. Methods: To analyze the humoral response and identify any predictive factors within these patients, we designed a prospective monocentric longitudinal study of Kidney transplant recipients (KTR) who received three doses of mRNA-1273 COVID-19 vaccine. Specific antibody levels were measured by chemiluminescence. Parameters related to clinical status such as kidney function, immunosuppressive therapy, inflammatory status and thymic function were analyzed as potential predictors of the humoral response. Results: Seventy-four KTR and sixteen healthy controls were included. One month after the administration of the third dose of the COVID-19 vaccine, 64.8% of KTR showed a positive humoral response. As predictive factors of seroconversion and specific antibody titer, we found that immunosuppressive therapy, worse kidney function, higher inflammatory status and age were related to a lower response in KTR while immune cell counts, thymosin-a1 plasma concentration and thymic output were related to a higher humoral response. Furthermore, baseline thymosin-a1 concentration was independently associated with the seroconversion after three vaccine doses. Discussion: In addition to the immunosuppression therapy, condition of kidney function and age before vaccination, specific immune factors could also be relevant in light of optimization of the COVID-19 vaccination protocol in KTR. Therefore, thymosin-a1, an immunomodulatory hormone, deserves further research as a potential adjuvant for the next vaccine boosters.

Dysregulation of iron metabolism modulators in virologically suppressed HIV-infected patients.

Background: Iron metabolism plays an essential role in cellular functions. Since virologically suppressed chronic HIV-infected subjects under effective antiretroviral treatment (ART) exhibit a persistent immune dysfunction that leads to comorbidities, iron homeostasis may be relevant in this context. We aimed to explore iron metabolism in virologically suppressed chronic HIV infected subjects under a successful ART. Methods: In this retrospective study, traditional iron metabolism biomarkers (total iron, ferritin, transferrin, and transferrin saturation index), as well as soluble transferrin receptor (sTfR), hepcidin, and inflammatory markers were determined in virologically suppressed chronic HIV-infected subjects under at least 2 years of ART (HIV) who also had >350 CD4-T-cells/mm3 (N=92) from Spain. As controls, we collected non-HIV age-matched healthy donors (Young, N=25) and elderly subjects (>65 years old; Elderly; N=25). Additionally, an external group of non-HIV patients with ferritin<50 ng/mL diagnosed with absolute iron deficiency (Ferropenic group; N=84) was included. Comparisons between groups were performed using Kruskal-Wallis or Mann-Whitney U-tests, while associations between variables were explored by Spearman's rho correlation coefficient. Results: We selected samples from HIV-infected subjects (aged 42[34-47], 95% males), young age-matched (aged 40[30-58], 60% males), and elderly controls (aged 82[78-88], 100% males). Compared to both healthy (Young and Elderly) groups, HIV exhibited decreased iron, transferrin saturation, and sTfR, and increased ferritin, but similar hepcidin levels. Notably, associations between sTfR and iron (Young, r=-0.587, p=0.002; Elderly, r=-0.496, p=0.012) or transferrin saturation index (Young, r=-0.581, p=0.002; Elderly, r=-0.489, p=0.013) were negative in both controls while positive in HIV (r=0.464, p<0.0001 and r=0.421, p<0.0001, respectively). Moreover, the expected negative correlation between hepcidin and sTfR, observed in controls (Young, r=-0.533, p=0.006; Elderly, r=-0.473, p=0.017), was absent in HIV (r=0.082; p=0.438). Interestingly, the HIV inflammatory profile differed from the Elderly one, who despite their inflammaging-related profile, succeed in maintaining these associations. Furthermore, subjects from the ferropenic group (aged 42[32-51], 5% males), showing significantly lower levels of hepcidin and higher sTfR, as expected, reflected similar correlations as those Young and Elderly, in contrast to HIV. Conclusions: Virologically suppressed chronic HIV-infected patients under successful ART exhibit altered levels of iron metabolism modulators suggesting a complex functional iron deficiency.

TRIM5α Restriction of HIV-1-N74D Viruses in Lymphocytes Is Caused by a Loss of Cyclophilin A Protection.

The core of HIV-1 viruses bearing the capsid change N74D (HIV-1-N74D) do not bind the human protein CPSF6. In primary human CD4+ T cells, HIV-1-N74D viruses exhibit an infectivity defect when compared to wild-type. We first investigated whether loss of CPSF6 binding accounts for the loss of infectivity. Depletion of CPSF6 in human CD4+ T cells did not affect the early stages of wild-type HIV-1 replication, suggesting that defective infectivity in the case of HIV-1-N74D viruses is not due to the loss of CPSF6 binding. Based on our previous result that cyclophilin A (Cyp A) protected HIV-1 from human tripartite motif-containing protein 5α (TRIM5αhu) restriction in CD4+ T cells, we found that depletion of TRIM5αhu in CD4+ T cells rescued the infectivity of HIV-1-N74D, suggesting that HIV-1-N74D cores interacted with TRIM5αhu. Accordingly, TRIM5αhu binding to HIV-1-N74D cores was increased compared with that of wild-type cores, and consistently, HIV-1-N74D cores lost their ability to bind Cyp A. In agreement with the notion that N74D capsids are defective in their ability to bind Cyp A, we found that HIV-1-N74D viruses were 20-fold less sensitive to TRIMCyp restriction when compared to wild-type viruses in OMK cells. Structural analysis revealed that N74D hexameric capsid protein in complex with PF74 is different from wild-type hexameric capsid protein in complex with PF74, which explains the defect of N74D capsids to interact with Cyp A. In conclusion, we showed that the decreased infectivity of HIV-1-N74D in CD4+ T cells is due to a loss of Cyp A protection from TRIM5αhu restriction activity.

Immunological features beyond CD4/CD8 ratio values in older individuals.

The CD4/CD8 T-cell ratio is emerging as a relevant marker of evolution for many pathologies and therapies. We aimed to explore immunological features beyond CD4/CD8 ratio values in older subjects (>65 years old) who were classified as having lower (<1.4), intermediate (1.4-2), or higher (>2) ratio values. The lower group showed a lower thymic output (sj/ß-TREC ratio) and frequency of naïve T-cells, concomitant with increased mature T-cells. In these subjects, the CD4 T-cell subset was enriched in CD95+ but depleted of CD98+ cells. The regulatory T-cell (Treg) compartment was enriched in CTLA-4+ cells. The CD8 T-cell pool exhibited increased frequencies of CD95+ cells but decreased frequencies of integrin-ß7+ cells. Interestingly, in the intermediate group, the CD4 pool showed greater differences than the CD8 pool, mostly for cellular senescence. Regarding inflammation, only hsCRP was elevated in the lower group; however, negative correlations between the CD4/CD8 ratio and ß2-microglobulin and sCD163 were detected. These subjects displayed trends of more comorbidities and less independence in daily activities. Altogether, our data reveal different thymic output and immune profiles for T-cells across CD4/CD8 ratio values that can define immune capabilities, affecting health status in older individuals. Thus, the CD4/CD8 ratio may be used as an integrative marker of biological age.

Nucleic acid binding by SAMHD1 contributes to the antiretroviral activity and is enhanced by the GpsN modification.

SAMHD1 impedes infection of myeloid cells and resting T lymphocytes by retroviruses, and the enzymatic activity of the protein-dephosphorylation of deoxynucleotide triphosphates (dNTPs)-implicates enzymatic dNTP depletion in innate antiviral immunity. Here we show that the allosteric binding sites of the enzyme are plastic and can accommodate oligonucleotides in place of the allosteric activators, GTP and dNTP. SAMHD1 displays a preference for oligonucleotides containing phosphorothioate bonds in the Rp configuration located 3' to G nucleotides (GpsN), the modification pattern that occurs in a mechanism of antiviral defense in prokaryotes. In the presence of GTP and dNTPs, binding of GpsN-containing oligonucleotides promotes formation of a distinct tetramer with mixed occupancy of the allosteric sites. Mutations that impair formation of the mixed-occupancy complex abolish the antiretroviral activity of SAMHD1, but not its ability to deplete dNTPs. The findings link nucleic acid binding to the antiretroviral activity of SAMHD1, shed light on the immunomodulatory effects of synthetic phosphorothioated oligonucleotides and raise questions about the role of nucleic acid phosphorothioation in human innate immunity.

Effect of Influenza Vaccination Inducing Antibody Mediated Rejection in Solid Organ Transplant Recipients.

Introduction: Our goal was to study whether influenza vaccination induced antibody mediated rejection in a large cohort of solid organ transplant recipients (SOTR). Methods: Serum anti-Human Leukocyte Antigen (HLA) antibodies were determined using class I and class II antibody-coated latex beads (FlowPRATM Screening Test) by flow cytometry. Anti-HLA antibody specificity was determined using the single-antigen bead flow cytometry (SAFC) assay and assignation of donor specific antibodies (DSA) was performed by virtual-crossmatch. Results: We studied a cohort of 490 SOTR that received an influenza vaccination from 2009 to 2013: 110 (22.4%) received the pandemic adjuvanted vaccine, 59 (12%) within the first 6 months post-transplantation, 185 (37.7%) more than 6 months after transplantation and 136 (27.7%) received two vaccination doses. Overall, no differences of anti-HLA antibodies were found after immunization in patients that received the adjuvanted vaccine, within the first 6 months post-transplantation, or based on the type of organ transplanted. However, the second immunization dose increased the percentage of patients positive for anti-HLA class I significantly compared with patients with one dose (14.6% vs. 3.8%; P = 0.003). Patients with pre-existing antibodies before vaccination (15.7% for anti-HLA class I and 15.9% for class II) did not increase reactivity after immunization. A group of 75 (14.4%) patients developed de novo anti-HLA antibodies, however, only 5 (1.02%) of them were DSA, and none experienced allograft rejection. Only two (0.4%) patients were diagnosed with graft rejection with favorable outcomes and neither of them developed DSA. Conclusion: Our results suggest that influenza vaccination is not associated with graft rejection in this cohort of SOTR.

Cyclophilin A Prevents HIV-1 Restriction in Lymphocytes by Blocking Human TRIM5α Binding to the Viral Core.

Disruption of cyclophilin A (CypA)-capsid interactions affects HIV-1 replication in human lymphocytes. To understand this mechanism, we utilize human Jurkat cells, peripheral blood mononuclear cells (PBMCs), and CD4+ T cells. Our results show that inhibition of HIV-1 infection caused by disrupting CypA-capsid interactions is dependent on human tripartite motif 5α (TRIM5αhu), showing that TRIM5αhu restricts HIV-1 in CD4+ T cells. Accordingly, depletion of TRIM5αhu in CD4+ T cells rescues HIV-1 that fail to interact with CypA, such as HIV-1-P90A. We found that TRIM5αhu binds to the HIV-1 core. Disruption of CypA-capsid interactions fail to affect HIV-1-A92E/G94D infection, correlating with the loss of TRIM5αhu binding to HIV-1-A92E/G94D cores. Disruption of CypA-capsid interactions in primary cells has a greater inhibitory effect on HIV-1 when compared to Jurkat cells. Consistent with TRIM5α restriction, disruption of CypA-capsid interactions in CD4+ T cells inhibits reverse transcription. Overall, our results reveal that CypA binding to the core protects HIV-1 from TRIM5αhu restriction.

Binding of host factors to stabilized HIV-1 capsid tubes.

The capsid-binding assay is an in vitro experiment used to determine whether cellular proteins interact with the HIV-1 core. In vitro assembled HIV-1 capsids recapitulate the surface of the HIV-1 core. The assay involves the incubation of in vitro assembled HIV-1 capsid-nucleocapsid (CA-NC) complexes with the protein in question. Subsequently, the mixture is spun through a sucrose cushion using an ultracentrifuge, and the pellet is analyzed for the presence of the protein in question. Although this binding assay is reliable, it is labor intensive and does not contain washing steps. Here we have developed a simpler and faster assay to measure whether a cellular protein is binding to capsid. More importantly, this novel capsid-binding assay contains washing steps. In this assay, we took advantage of the HIV-1 capsid mutant A14C/E45C protein, which is stabilized by disulfide bonds, and is resistant to washing steps. We validated the reliability and specificity of this novel assay by testing the capsid binding ability of TRIMCyp, CPSF6 and MxB with their corresponding controls. Overall, this novel assay provides a reliable and fast methodology to search for novel capsid binders.

Two Doses of Inactivated Influenza Vaccine Improve Immune Response in Solid Organ Transplant Recipients: Results of TRANSGRIPE 1-2, a Randomized Controlled Clinical Trial.

BACKGROUND: Influenza vaccine effectiveness is not optimal in solid organ transplant recipients (SOTR). We hypothesized that a booster dose might increase it. METHODS: TRANSGRIPE 1-2 is a phase 3, randomized, controlled, multicenter, open-label clinical trial. Patients were randomly assigned (1:1 stratified by study site, type of organ, and time since transplantation) to receive 1 dose (control group) or 2 doses (booster group) of the influenza vaccine 5 weeks apart. RESULTS: A total of 499 SOTR were enrolled. Although seroconversion at 10 weeks did not meet significance in the modified intention-to-treat population, seroconversion rates were significantly higher in the booster arm for the per-protocol population (53.8% vs 37.6% for influenza A(H1N1)pdm; 48.1% vs 32.3% for influenza A(H3N2); and 90.7% vs 75% for influenza B; P < .05). Furthermore, seroprotection at 10 weeks was higher in the booster group: 54% vs 43.2% for A(H1N1)pdm; 56.9% vs 45.5% for A(H3N2); and 83.4% vs 71.8% for influenza B (P < .05). The number needed to treat to seroprotect 1 patient was <10. The clinical efficacy (99.2% vs 98.8%) and serious adverse events (6.4% vs 7.5%) were similar for both groups. CONCLUSIONS: In SOTR, a booster strategy 5 weeks after standard influenza vaccination is safe and effective and induces an increased antibody response compared with standard influenza vaccination consisting of a single dose. CLINICAL TRIALS REGISTRATION: EudraCT (2011-003243-21).

Applying lessons learned from cytomegalovirus infection in transplant patients to vaccine design.

Studies in transplant recipients over the past decade aiming to characterize the immune response to cytomegalovirus (CMV) replication have provided insights that can be used to guide CMV vaccine development. These studies have characterized multiple aspects of the immune response to virus infection in humans, and have identified immunologic variables that correlate with the ability to control virus replication. These findings can be used to guide vaccine development by informing decisions regarding antigen selection and the type of immune response that must be elicited by these antigens to promote protective immunity. In addition, these studies have provided information that could aid in the identification of immunologic endpoints in vaccine clinical trials, thus facilitating their design and implementation.