Correlates of postnatal human cytomegalovirus transmission in term babies in the first year.

Postnatal human cytomegalovirus (HCMV) infection in newborns is well characterized for preterm infants but less so for term infants. We sought to analyze the rates and routes of HCMV transmission in full-term infants during the first year of life. A cohort of 120 HCMV seropositive mothers and their 122 newborns were tested after delivery for HCMV-DNA shedding in different bodily fluids. Postnatal HCMV infection was defined as the detection of >2.5 × 102 HCMV-DNA copies/mL in infants' saliva swabs. Maternal neutralizing antibody serum titer, HCMV-specific T-cell response, and HCMV glycoprotein B immunoglobulin G on breastmilk were analyzed. HCMV shedding was detected in 67 of 120 mothers (55.8%), and 20 of 122 infants (16.4%) developed HCMV infection within the first 3 months of life. Six additional infants were infected during the first year, for a postnatal infection rate of 21.3%. Viral shedding was more frequent in breastmilk than saliva, urine, and vaginal secretions, and the mothers of infected infants showed higher levels of HCMV-DNA in milk. No association was found between the antibody levels in serum or milk and maternal viral shedding, whereas a slightly lower frequency of HCMV-specific CD4+ T-cells with long-term memory phenotype was observed in women with HCM-DNA-positive milk. About one out of five infants develop HCMV infection within the first year of life. Breastmilk appears the major route of transmission of the infection, maternal saliva has a minor role whereas the role of vaginal secretions is negligible.

Impact of SARS-CoV-2 infection during pregnancy and persistence of antibody response.

BACKGROUND: Pregnant women may be at an increased risk of developing severe or critical disease associated with the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection causing severities during pregnancy. We performed a prospective study to describe the impact of SARS-CoV-2 infection on pregnancy outcomes and on the newborn, depending on the severity of the disease. The antibody response and persistence of SARS-CoV-2 anti-Spike (S) IgG, IgA and anti-Nu- cleocapsid (NCP) IgG, was investigated. METHODS: A total of 48 pregnant women with SARS-CoV-2 infection were enrolled, and sequential serum samples from 30 of them were collected until one year after infection. Outcomes of pregnan- cy and newborn parameters were evaluated in comparison with 200 uninfected controls. RESULTS: Asymptomatic infection was observed in 31/48 women (64.5%), mild COVID-19 in 12/48 women (25.0%), while 5/48 women (10.5%) developed pneumonia. Women with pneumonia mount- ed significantly higher levels of anti-S IgG, IgA and anti-NCP IgG between 1 and 3 months after onset of infection compared to asymptomatic women. Anti-S IgG persisted in the majority of women from 6 months to at least one year after infection, especially in those with symptomatic infection and pneumonia, while anti-S IgA and anti-NCP IgG declined earlier. Pregnancy complications and new- born parameters were not significantly different from those observed in uninfected controls. CONCLUSION: Anti-SARS-CoV-2 antibody development and persistence was not impaired in pregnant women, while SARS-CoV-2 infection did not cause major pregnancy or newborn complications in asymptomatic or symptomatic women, nor in women with pneumonia receiving prompt clinical care.

SARS-CoV-2-specific IgG and NCP in vulnerable patients without symptoms.

Patients with severe COVID-19 both seroconvert earlier and develop higher concentrations of SARS- CoV-2-specific IgG than patients with mild symptoms. In this retrospective study we considered different categories of patients defined as "vulnerable" because affected by other pathologies, such as patients with genetic and cardiovascular diseases; patients with autoimmune dermatological dis- ease; kidney and lung transplant patients, and pregnant women because the prevalence of Covid-19 infection during pregnancy is not known. This study was performed at IRCCS San Matteo Hospital in Pavia, North Italy, a zone considered at high risk during the COVID-19 pandemic from June to December 2020. None of the positive screened patients had symptoms of COVID-19 infection at the time of inclusion in this study.

Asymptomatic SARS-CoV-2 infection is not associated with miscarriage in early pregnancy: a retrospective analysis.

The prevalence of SARS-CoV-2 infection during pregnancy is relatively unknown. In this study we report the potential impact of undiagnosed SARS-CoV-2 infection on pregnancy loss in the first half of pregnancy by comparing the prevalence of the infection in a retrospective group of pregnant women with miscarriage (n=62) and a prospective control group with no pregnancy loss in the first trimester (n=218). Of 62 women who had miscarriage, 2 (3.2%) resulted IgM for SARS-CoV-2 negative and IgG seropositive, while of 218 pregnant women, 5 (2.3 %) resulted IgM for negative and IgG seropositive. The SARS-CoV-2 seroprevalence was not significantly different in the two groups of women, therefore excluding a significant role of SARS-CoV-2 infection in pregnancy loss. Therefore, our data show that SARS-CoV-2 infection within the first trimester does not seem to predispose to early pregnancy loss and that the impact of asymptomatic or mildly symptomatic SARS-CoV-2 infection on pregnancy appears limited.

Kidney transplant rejection rate in screened patients for anti-SARS-CoV-2 antibodies, during COVID-19 pandemic in Northern Italy.

Coronavirus is a high-risk pathogen for kidney transplant recipients receiving immunosuppressive therapy; Coronavirus disease 2019 (COVID-19) is an infection causing severe acute respiratory syndrome (SARS-CoV2), and progressive withdrawal of immunosuppressive drugs has been suggested in transplanted patients. At IRCCS San Matteo Hospital in Pavia, Northern Italy, during the pandemic we performed a screening and all transplanted patients were evaluated for IgG anti SARS-CoV-2; 12 of 201 kidney transplant recipients (6%) screened for IgG anti SARS-CoV-2 (s) developed kidney transplant rejection; 10 (83%) were negative and 2 (17%) resulted positive for SARS-CoV-2 IgG, while among 189 patients without rejection, 162 (86%) resulted negative and 27 (14%) positive (P=0.69). COVID 19 course may be more severe in kidney transplant recipients but it does not significantly increase risk of kidney rejection.

Human cytomegalovirus (HCMV)-specific T cell but not neutralizing or IgG binding antibody responses to glycoprotein complexes gB, gHgLgO, and pUL128L correlate with protection against high HCMV viral load reactivation in solid-organ transplant recipients.

Immune correlates of protection against human cytomegalovirus (HCMV) infection are still debated. This study aimed to investigate which arm of the immune response plays a major role in protection against HCMV infection in kidney transplant recipients (n = 40) and heart transplant recipients (n = 12). Overall, patients were divided into 2 groups: one including 37 patients with low viral load (LVL), and the other including 15 patients with high viral load (HVL). All LVL patients resolved the infection spontaneously, whereas HVL patients were all treated with one or more courses of antivirals. In HVL patients, viral DNAemia, which was more than 100 times higher than LVL, appeared and peaked at significantly earlier times, but disappeared much later than in LVL patients. During a 1-year follow-up, all LVL patients had levels of HCMV-specific CD4+ (and CD8+ ) T cells significantly higher than HVL patients. On the contrary, titers of neutralizing antibodies and enzyme-linked immunosorbent assay-IgG antibodies to gB, gHgLgO, and pentamer gHgLpUL128L were overlapping in the 2 patient groups. In conclusion, while a valid HCMV-specific T-cell response was detected in more than 90% of LVL patients, >90% of HVL patients lacked an adequate T-cell response. Antibody responses did not appear to be associated directly or indirectly with protection.

Comparison of the T-cell response to human cytomegalovirus (HCMV) as detected by cytokine flow cytometry and QuantiFERON-CMV assay in HCMV-seropositive kidney transplant recipients.

Human cytomegalovirus (HCMV)-specific T-cell response in kidney transplant recipients (KTR) helps to identify patients at risk for severe infection. To assess the T-cell response, this study compared our in-house developed reference test, based on T-cell (both CD4+ and CD8+) stimulation by autologous HCMV-infected dendritic cells (iDC) and subsequent detection by cytokine flow cytometry (CFC-iDC), with the Quanti-FERON-CMV (QF-CMV) assay. Fifty-three HCMV-seropositive KTR were enrolled. At the DNAemia peak, 33 (62%) had low viral load (LVL, <3x105 DNA copies/mL) self-resolving infection, 19 (36%) high viral load (HVL, >3x105 DNA copies/mL) infection treated with antivirals, and one LVL patient (2%) tissue-invasive disease alone. Both assays showed a delayed recovery of HCMV-specific T-cell immunity in HVL vs LVL patients. Immune reconstitution kinetics did not significantly differ between the two assays in HVL patients. QF-CMV and CFC-iDC showed comparable sensitivities, but QF-CMV had a lower (although not significantly) specificity. Indeed, 7/19 HVL patients (37%) were erroneously considered protected from severe infection by QF-CMV, whereas CFC-iDC misidentified only 3/19 (16%) patients as protected. Although our reference test takes longer to complete, it appears slightly better at predicting patients at risk for severe HCMV infection. Moreover, QF-CMV may provide false negative results with some HLA types.

Follicular helper T-cells and virus-specific antibody response in primary and reactivated human cytomegalovirus infections of the immunocompetent and immunocompromised transplant patients.

Analysis of human cytomegalovirus (HCMV) primary infection in immunocompetent (n=40) and immunocompromised transplant patients (n=20) revealed that the median peak antibody titre neutralizing infection of epithelial cells was 16-fold higher in immunocompromised patients. The mechanism of this finding was investigated by measuring: (i) HCMV DNAemia; (ii) HCMV neutralizing antibodies; (iii) ELISA IgG antibody titre to HCMV glycoprotein complexes gHgLpUL128L, gHgLgO and gB; and (iv) HCMV-specific (IFN-γ+) CD4+ and CD8+ T-cells. Circulating CXCR5+ CD4+ (memory T follicular helper - TFH-cells) were identified as activated TFH (ICOS+PD-1++CCR7lo) and quiescent cells. In the early stages of primary infection, activated TFH cells increased in number. Concomitantly, both neutralizing and IgG antibodies to HCMV glycoproteins reached a peak, followed by a plateau. A stop in antibody rise occurred upon appearance of HCMV-specific CD4+ T-cells, HCMV clearance and progressive reduction in activated TFH cells. The main differences between healthy and transplant patients were that the latter had a delayed DNA peak, a much higher DNA load and delayed activated TFH cells and antibody peaks. Similar events were observed in clinically severe HCMV reactivations of transplant patients. A preliminary analysis of the specificity of the activated TFH cell response to viral proteins showed a major response to the pentamer gHgLpUL128L and gB. In conclusion, in the absence of T-cell immunity, one of the first lines of defence, during primary infection, is conferred by antibodies produced through the interaction of TFH cells and B-cells of germinal centres, resulting in differentiation of B-cells into antibody producing plasma cells.

Predictive value of human cytomegalovirus (HCMV) T-cell response in the control of HCMV infection by seropositive solid-organ transplant recipients according to different assays and stimuli.

Human cytomegalovirus (HCMV) is still the most common viral infection in solid-organ transplant recipients (SOTR). Our study aimed to identify the predictive values of the T-cell response able to protect from HCMV disease, according to different assays. Viral DNA was determined by real-time PCR. The T-cell immune response to HCMV infection was investigated in SOTR according to the following assays and stimuli: cytokine flow cytometry (CFC) after peripheral blood mononuclear cell (PBMC) stimulation with autologous HCMV-infected dendritic cells (iDC) vs three ELISPOT assays using PBMCs stimulated with: 1. HCMV-infected cell lysate (iCL); 2. a pool of 34 epitopic peptides (PP) from different HCMV proteins; 3. a commercial pp65 peptide pool (CPM). ELISPOT results were normalized to T-cell counts. Overall, 51 SOTR were enrolled: 29 (57%) had low viral load (LVL) self-resolving infections, 19 (37%) high viral load (HVL) infections treated with antiviral drugs, and 3 (6%) tissue-invasive disease (TID). At DNAemia peak, ROC analysis showed that CFC-iDC CD4+ and the ELISPOT-iCL assays yielded overlapping area under the curve (AUC) results. The time needed to reconstitute protective T-cell immunity in SOTR with HVL infections was significantly longer with each assay compared to LVL infections. Using the CFC-iDC assay as a reference test (requiring 7 days to complete), the 24h ELISPOT-iCL assay provides similar results in terms of protection prediction from HCMV infection.

Reconstitution of Human Cytomegalovirus-Specific CD4+ T Cells is Critical for Control of Virus Reactivation in Hematopoietic Stem Cell Transplant Recipients but Does Not Prevent Organ Infection.

The relative contribution of human cytomegalovirus (HMCV)-specific CD4(+) and CD8(+) T cells to the control of HCMV infection in hematopoietic stem cell transplant (HSCT) recipients is still controversial. HCMV reactivation and HCMV-specific CD4(+) and CD8(+) T cell reconstitution were monitored for 1 year in 63 HCMV-seropositive patients receiving HSCT. HCMV reactivation was detected in all but 2 patients. In 20 of 63 (31.7%) patients (group 1) HCMV infection resolved spontaneously, whereas 32 of 63 (50.8%) patients (group 2) controlled the infection after a single short-course of pre-emptive therapy and the remaining 9 (14.3%) patients (group 3) suffered from relapsing episodes of HCMV infection, requiring multiple courses of antiviral therapy. The kinetics and magnitude of HCMV-specific CD8(+) T cell reconstitution were comparable among the 3 groups, but HCMV-specific CD4(+) T cells were lower in number in patients requiring antiviral treatment. HCMV-seronegative donors, as well as unrelated donors (receiving antithymocyte globulin) and acute graft-versus-host disease (GVHD) were associated with both delayed HCMV-specific CD4(+) T cell reconstitution and severity of infection. Conversely, these risk factors had no impact on HCMV-specific CD8(+) T cells. Eight patients with previous GVHD suffered from HCMV gastrointestinal disease, although in the presence of HCMV-specific CD4(+) and CD8(+) systemic immunity and undetectable HCMV DNA in blood. Reconstitution of systemic HCMV-specific CD4(+) T cell immunity is required for control of HCMV reactivation in adult HSCT recipients, but it may not be sufficient to prevent late-onset organ localization in patients with GVHD. HCMV-specific CD8(+) T cells contribute to control of HCMV infection, but only after HCMV-specific CD4(+) T cell reconstitution.

Yet another in vitro evidence that natural compounds introduced by diet have anti-amyloidogenic activities and can counteract neurodegenerative disease depending on aging.

A major issue in Alzheimer's disease (AD) research is to find some new therapeutic drug which decrease Amyloid-beta (Aß) aggregation. From a therapeutic point of view the major question is whether pharmacological inhibition of inflammation pathways will be able to safely reverse or slow the course of disease. Natural compounds are capable of binding to different targets implicated in AD and exert neuroprotective effects. Aim of this study was to evaluate the in vitro inhibition of Aß1-42 fibrillogenesis in presence of Gallic acid, Rutin, Melatonin and ProvinolsTM . We performed the analysis with Transmission and Scanning Electron Microscopy, and with X-ray microanalysis. Samples treated with Rutin, that arises from phenylalanine via the phenylpropanoid pathway, show the best effective result obtained because a significantly fibril inhibition activity is detectable compared to the other compounds. Melatonin shows a better inhibitory activity than ProvinolsTM and Gallic acid at the considered concentrations.

Detection of Epstein-Barr virus-specific memory CD4+ T cells using a peptide-based cultured enzyme-linked immunospot assay.

Approaches to evaluate T-cell responses to Epstein-Barr virus (EBV) include enzyme-linked immunospot (ELISPOT), which quantifies cells capable of immediate interferon-γ secretion upon antigen stimulation. However, evaluation of expandable EBV-specific memory T cells in an ELISPOT format has not been described previously. We quantified EBV-specific T-cell precursors with high proliferative capacity by using a peptide-based cultured interferon-γ ELISPOT assay. Standard and cultured ELISPOT responses to overlapping peptide pools (15-mers overlapping by 11 amino acids) covering the lytic (BZLF1 and BMRF1) and latent (EBNA1, EBNA3a, EBNA3b, EBNA3c, LMP1 and LMP2) EBV proteins were evaluated in 20 healthy subjects with remote EBV infection and, for comparison, in four solid organ transplant recipients. Cultured ELISPOT responses to both lytic and latent EBV antigens were significantly higher than standard ELISPOT responses. The distribution of EBV-specific T-cell responses detected in healthy virus carriers showed more consistent cultured ELISPOT responses compared with standard ELISPOT responses. T-cell responses quantified by cultured ELISPOT were mainly mediated by CD4+ T cells and a marked pattern of immunodominance to latent-phase antigens (EBNA1 > EBNA3 family antigens > LMP2 > LMP1) was shown. Both the magnitude and distribution of EBV-specific T-cell responses were altered in solid organ transplant recipients; in particular, cultured ELISPOT responses were almost undetectable in a lung-transplanted patient with EBV-associated diseases. Analysis of T-cell responses to EBV by ELISPOT assays might provide new insights into the pathogenesis of EBV-related diseases and serve as new tools in the monitoring of EBV infection in immunocompromised patients.

Inflammatory and Immune Responses during SARS-CoV-2 Infection in Vaccinated and Non-Vaccinated Pregnant Women and Their Newborns.

BACKGROUND: Pregnant women are more susceptible to severe disease associated with SARS-CoV-2 infection. We performed a prospective study to analyze the inflammatory and immune profile after SARS-CoV-2 infection occurring in vaccinated or non-vaccinated pregnant women and their newborns. METHODS: Twenty-five pregnant women with SARS-CoV-2 infection were enrolled, and sixteen cord blood samples were obtained at delivery. RESULTS: We observed that IL-1ß, TNF-α, Eotaxin, MIB-1ß, VEGF, IL-15, IL-2, IL-5, IL-9, IL-10 and IL-1ra levels were significantly higher in vaccinated than non-vaccinated mothers. Furthermore, the newborns of the vaccinated mothers produced higher levels of IL-7, IL-5 and IL-12 compared to the newborns of non-vaccinated mothers. Anti-Spike (S) IgG levels were significantly higher in all vaccinated mothers and their newborns compared to the non-vaccinated group. We found that 87.5% of vaccinated women and 66.6% of non-vaccinated women mounted an S-specific T-cell response quantified by ELISpot assay. Moreover, 75.0% of vaccinated mothers and 38.4% of non-vaccinated mothers showed S-specific CD4+ T-cell proliferative response. The T-helper subset response was restricted to CD4+ Th1 in both vaccinated and non-vaccinated women. CONCLUSION: A higher level of cytokines, IgG antibodies and memory T cells was noted in the vaccinated women. Furthermore, the maternal IgG antibody trans-placental transfer occurred more frequently in vaccinated mothers and may protect the newborn.

Immunological Aspects of Human Papilloma Virus-Related Cancers Always Says, "I Am like a Box of Complexity, You Never Know What You Are Gonna Get".

The human papillomavirus (HPV) can cause different cancers in both men and women. The virus interferes with functions of the cervix, vulva, vagina, anus in the anogenital area, breast, and head and neck cancer due to the local lesions. The tumors lead to death if not treated as a result of distant metastasis to internal organs and brain. Moreover, HPV attenuates the immune system during chronic infection and releases viral antigens into the tumor microenvironment. The tumors know how difficult is to win the battle with a strong united army of immune cells that are equipped with cytokines and enzymes. They confuse the immune cells with secreting viral antigens. The immune system is equipped with cytokines, a complement system, antibodies, and other secretory proteins to overcome the foreign invaders and viral antigens. However, the majority of the time, tumors win the battle without having all the equipment of the immune cells. Thus, in this review, we describe the recent progression in cellular and humoral immunity studies during the progression of HPV-related cancers. First of all, we describe the role of B, plasmoid cells, and B regulatory cells (Breg) in their functions in the tumor microenvironment. Then, different subtypes of T cells such as T CD8, CD4, T regulatory (Treg) cells were studied in recently published papers. Furthermore, NK cells and their role in tumor progression and prevention were studied. Finally, we indicate the breakthroughs in immunotherapy techniques for HPV-related cancers.

Serum and breastmilk SARS-CoV-2 specific antibodies following BNT162b2 vaccine: prolonged protection from SARS-CoV-2 in newborns and older children.

OBJECTIVES: Vaccination is the best strategy against COVID-19. We aimed to determine antibodies against SARS-CoV-2 in breastmilk and serum of mothers vaccinated with the mRNA vaccine. METHODS: This prospective study included 18 lactating women vaccinated with the BNT162b2 vaccine. Serum and breastmilk were collected before the first dose (T0), at the second dose (T1), 3 weeks after the second dose (T2), and 6 months after the first dose (T3). Serum anti-SARS-CoV-2 Spike (S) Immunoglobulin G (IgG) and Immunoglobulin A (IgA) were measured using a semi-quantitative enzyme-linked immunosorbent assay (ELISA) and secretory antibody (s) IgG and IgA in breastmilk using quantitative analysis. RESULTS: We detected serum anti-S IgG and IgA in all women after vaccination. Specific IgG and IgA were higher at T1, T2, and T3 compared with T0 (P <0.0001). Higher antibody levels were observed at T2 and lower values at T3 versus T2 (P = 0.007). After 6 months, all patients had serum IgG, but three of 18 (16%) had serum IgA. In breastmilk, sIgA was present at T1 and T2 and decreased after 6 months at T3 (P = 0.002). Breastmilk sIgG levels increased at T1 and T2 and peaked at T3 (P = 0.008). CONCLUSION: Secretory antibodies were transmitted through breastmilk until 6 months after anti-COVID-19 mRNA vaccination. Protection of the newborn through breastfeeding needs to be addressed.

Human cytomegalovirus non-primary infection during pregnancy: antibody response, risk factors and newborn outcome.

OBJECTIVES: Human cytomegalovirus (HCMV) non-primary infections can occur in pregnant women and may result in congenital infection. Comprehensive studies investigating the frequency, characteristics, risk factors and immune response of non-primary infection in pregnancy are missing, while the rate of vertical transmission is not known. METHODS: HCMV non-primary infection was investigated prospectively in 250 pregnant women. Blood and urine samples as well as saliva and vaginal swabs were collected at 13, 21 and 31 weeks of gestation and at delivery. HCMV-DNA and specific IgG and IgM levels were determined. RESULTS: Overall, 105/250 pregnant women (42.0%) developed non-primary infection. HCMV-DNA was detected more frequently in vaginal secretions (84/250 of the women, 33.6%) than in urine (35/250, 14.0%), saliva (26/250, 10.4%) and blood (7/250, 3.0%). The rate of HCMV non-primary infection increased significantly with the progression of pregnancy (from 12.9% in the first trimesters of gestation to 21.9% at delivery, p < 0.01). IgM was detected in 25/250 of the women (10.0%), with no association with non-primary infection, while anti-gB IgG was significantly higher (p < 0.01) in women with non-primary infection. Age and close contact with children were not associated with non-primary infection. No woman with non-primary infection transmitted the infection to the fetus (95% confidence interval of transmission rate: 0-3.5%). DISCUSSION: Although HCMV non-primary infection is frequent during pregnancy, the rate of congenital infection as a consequence of non-primary infection is likely to be ≤ 3.5%.

Association between Vitamin D Serum Levels and Immune Response to the BNT162b2 Vaccine for SARS-CoV-2.

The use of micronutrients such as vitamin D could improve the response to viral vaccines, particularly in immunosuppressed and immunosenescent subjects. Here, we analysed the association between serum 25-hydroxyvitamin D (25OHD) levels and the immune response elicited by the BNT162b2 vaccine in a cohort of 101 healthcare workers naïve for SARS-CoV-2 infection. We observed no significant differences in anti-spike (S) IgG and T-cell responses according to the 25OHD status at baseline. However, significant correlations between the 25OHD concentration at baseline and (i) the anti-S response (p < 0.020) and (ii) the neutralizing antibody (NT) titre (p = 0.040) at six months after the second dose were detected. We concluded that adequate levels of vitamin D may improve the immune response to mRNA vaccines such as BNT162b2, and that further larger studies are warranted in order to confirm these preliminary observations.

Differential Kinetics of Effector and Memory Responses Induced by Three Doses of SARS-CoV-2 mRNA Vaccine in a Cohort of Healthcare Workers.

We reported the long-term kinetics of immune response after vaccination and evaluated the immunogenicity after a third dose of mRNA vaccine in 86 healthcare workers. Humoral response was analyzed by measuring anti-spike IgG and SARS-CoV-2 NTAbs titer; cell-mediated response was measured as frequency of IFN-γ producing T-cells and cell proliferation. Memory B cells secreting SARS-CoV-2 RBD-IgG were measured by B-spot assay. At three weeks after the third dose (T4), the frequency of subjects showing NT-Abs titer at the upper detection limit (≥640) was significantly higher than that observed at three weeks after the second dose (26/77; 33.7% vs. 9/77; 11.6%; p = 0.0018). Additionally, at T4, all the subjects reached positive levels of T-cell mediated response (median 110 SFU/106 PBMC, IQR 73-231). While the number of IFNγ-producing T-cells decreased between second and third dose administration, the T-cell proliferative response did not decrease but was sustained during the follow-up. Among T-cell subsets, a higher proliferative response was observed in CD4+ than in CD8+ population. Moreover, even if a decline in antibody response was observed between the second and third dose, a sustained persistence of memory B cells was observed. Subsequently, the third dose did not affect the frequency of memory B cells, while it restored or increased the peak antibody levels detected after the second dose.

Humoral and cell-mediated response against SARS-CoV-2 variants elicited by mRNA vaccine BNT162b2 in healthcare workers: a longitudinal observational study.

OBJECTIVES: To assess the humoral and cell-mediated response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) elicited by the mRNA BNT162b2 vaccine in SARS-CoV-2-experienced and -naive subjects against a reference strain and SARS-CoV-2 variants. METHODS: The humoral response (including neutralizing antibodies) and T-cell-mediated response elicited by BNT162b2 vaccine in 145 healthcare workers (both naive and positive for previous SARS-CoV-2 infection) were evaluated. In a subset of subjects, the effect of SARS-CoV-2 variants on antibody level and cell-mediated response was also investigated. RESULTS: Overall, 125/127 naive subjects (98.4%) developed both neutralizing antibodies and specific T cells after the second dose of vaccine. Moreover, the antibody and T-cell responses were effective against viral variants since SARS-CoV-2 NT Abs were still detectable in 55/68 (80.9%) and 25/29 (86.2%) naive subjects when sera were challenged against ß and δ variants, respectively. T-cell response was less affected, with no significant difference in the frequency of responders (p 0.369). Of note, two doses of vaccine were able to elicit sustained neutralizing antibody activity against all the SARS-CoV-2 variants tested in SARS-CoV-2-experienced subjects. CONCLUSIONS: BNT162b2 vaccine elicited a sustained humoral and cell-mediated response in immunocompetent subjects after two-dose administration of the vaccine, and the response seemed to be less affected by SARS-CoV-2 variants, the only exceptions being the ß and δ variants. Increased immunogenicity, also against SARS-CoV-2 variant strains, was observed in SARS-CoV-2-experienced subjects. These results suggest that triple exposure to SARS-CoV-2 antigens might be proposed as valuable strategy for vaccination campaigns.