Ubiquitinated Hepatitis D Antigen-Loaded Microvesicles Induce a Potent Specific Cellular Immune Response to Inhibit HDV Replication in Vivo

Hepatitis D is the most severe viral hepatitis with accelerating the process of liver cirrhosis and increasing the risk of hepatocellular carcinoma. However, there are no effective antiviral drugs.

Serological and cellular non-responders in a long-term cross-sectional cohort of SARS-CoV-2-specific PCR-positive individuals

During the first pandemic wave, the dark figure of SARS-CoV-2 exposure was estimated to be high, however, an accelerated loss of antibodies was reported after about 6 months post infection. This study was performed to unveil the group of serological non-responders (NR) in PCR+ individuals 6-9 months after the first pandemic SARS-CoV-2 wave in spring 2020 and to evaluate their specific cellular immune response towards spike-molecule compared to PCR- and not PCR-tested (NT) household contact persons. SARS-CoV-2-specific antibodies were quantified using a commercial ELISA kit. The synergistic binding strength was assessed as relative avidity index (RAI) using ammonium-thiocyanate as chaotropic agent. The specific IFNγ-production in response to spike-protein was determined in spot-forming-units (SFU) by ELISPOT-assay. In PCR- 50.0%, in PCR+ 35.3% and in NT 20.7% had undetectable IgG-anti-SARS-CoV-2 and were considered non-responders (NR). All seropositive responders from the PCR-, 45.5% of PCR+ and 43.0% of NT developed high avidity (RAI>60%). In serological responders, cellular responses were detected in 75.0% PCR-, 75.8% PCR+ and 66.7% NT. In serological NR, positive SFU were found in 75.0% PCR-, 22.2% PCR+ and 17.4% NT. Significantly higher stimulation-indices were seen in PCR+ responders compared to PCR+ serological NR. Our findings showed that also PCR- and household contact persons who were not tested (NT) developed SARS-CoV-2-specific humoral and cellular immune responses. The relatively large proportion of serological non-responders but also the proportion of cellular non-responders within the group of IgG-positive individuals after PCR+ infection underlines the need for COVID-19 vaccinations in the reconvalescent group.

Highly functional virus-specific cellular immune response in asymptomatic SARS-CoV-2 infection

The efficacy of virus-specific T cells in clearing pathogens involves a fine balance between antiviral and inflammatory features. SARS-CoV-2–specific T cells in individuals who clear SARS-CoV-2 without symptoms could reveal nonpathological yet protective characteristics. We longitudinally studied SARS-CoV-2–specific T cells in a cohort of asymptomatic (n = 85) and symptomatic (n = 75) COVID-19 patients after seroconversion. We quantified T cells reactive to structural proteins (M, NP, and Spike) using ELISpot and cytokine secretion in whole blood. Frequencies of SARS-CoV-2–specific T cells were similar between asymptomatic and symptomatic individuals, but the former showed an increased IFN-γ and IL-2 production. This was associated with a proportional secretion of IL-10 and proinflammatory cytokines (IL-6, TNF-α, and IL-1β) only in asymptomatic infection, while a disproportionate secretion of inflammatory cytokines was triggered by SARS-CoV-2–specific T cell activation in symptomatic individuals. Thus, asymptomatic SARS-CoV-2–infected individuals are not characterized by weak antiviral immunity; on the contrary, they mount a highly functional virus-specific cellular immune response.

Highly functional virus-specific cellular immune response in asymptomatic SARS-CoV-2 infection

The efficacy of virus-specific T cells in clearing pathogens involves a fine balance between their antiviral and inflammatory features. SARS-CoV-2-specific T cells in individuals who clear SARS-CoV-2 infection without symptoms or disease could reveal non-pathological yet protective characteristics. We therefore compared the quantity and function of SARS-CoV-2-specific T cells in a cohort of asymptomatic individuals (n=85) with that of symptomatic COVID-19 patients (n=76), at different time points after antibody seroconversion. We quantified T cells reactive to structural proteins (M, NP and Spike) using ELISpot assays, and measured the magnitude of cytokine secretion (IL-2, IFN-γ, IL-4, IL-6, IL-1β, TNF-α and IL-10) in whole blood following T cell activation with SARS-CoV-2 peptide pools as a functional readout. Frequencies of T cells specific for the different SARS-CoV-2 proteins in the early phases of recovery were similar between asymptomatic and symptomatic individuals. However, we detected an increased IFN-γ and IL-2 production in asymptomatic compared to symptomatic individuals after activation of SARS-CoV-2-specific T cells in blood. This was associated with a proportional secretion of IL-10 and pro-inflammatory cytokines (IL-6, TNF-α and IL-1β) only in asymptomatic infection, while a disproportionate secretion of inflammatory cytokines was triggered by SARS-CoV-2-specific T cell activation in symptomatic individuals. Thus, asymptomatic SARS-CoV-2 infected individuals are not characterized by a weak antiviral immunity; on the contrary, they mount a robust and highly functional virus-specific cellular immune response. Their ability to induce a proportionate production of IL-10 might help to reduce inflammatory events during viral clearance.

Humoral and cellular immunity to measles and rubella virus antigens in healthy subjects

An issue of eradicating measles and rubella virus-induced infections currently remains unresolved, despite existing effective methods for specific prophylaxis and WHO’s commitment to a mass vaccination policy. While improving epidemic situation, analysis of new challenges, such as measles incidence in adults, especially in adults vaccinated in childhood, is of particular interest. The aim of the study was to analyze serum measles and rubella virus-specific IgG antibodies in young healthy people and estimate antigen-specific cellular immune response in seronegative subjects. There were examined 100 healthy adults aged 18–30 years old. Level of serum specific IgG was measured by ELISA (Vector-Best, Russia). Antigen-specific cellular immune response was assessed by magnitude of surface CD107a expression on CD8hi T cells challenged by measles and rubella virus-derived antigens. It was found that average level of antibodies against rubella virus comprised 175.5 IU/ml, 49% of which recovered after rubella, 46% were vaccinated, whereas 5% subjects contained no virus-specific antibodies. In addition, mean level of anti-measles virus antibodies was below protective magnitude, among which 1% subjects recovered after measles, 31% displayed post-vaccination immunity, 55% subjects were seronegative, and 13% had equivocal levels of specific antibodies. Thus, 68% subjects were unprotected against measles virus based on the level of serum virus-specific antibodies. Moreover, 40 out of 68 subjects were vaccinated against measles in childhood. Additional screening adult subjects for intensity of measles and rubella virus-specific cellular immunity demonstrated that 57.37% of them contained peripheral blood CD8 T cells against measles virus and 59.01% — against rubella virus. Further analysis allowed to identify 4 subgroups displaying: 1) high level of virus-specific antibodies and T cells; 2) neither antibodies nor specific T-cells reaching as low as 20% of baseline group; 3) high antibody level combined with low amount of specific T cells; and 4) low antibody level combined with high level of specific T cells. thus, it may be assumed that cellular and humoral immune arms are maintained independently and being active for a long term after vaccination. Preserving a specific T-cell immunity seems to provide protection against infection, thereby accounting for the lack of measles manifestation in all seronegative subjects.

Cellular Immune Responses 6 Years Following 1, 2, or 3 Doses of Quadrivalent HPV Vaccine in Fijian Girls and Subsequent Responses to a Dose of Bivalent HPV Vaccine

Background This study examined the cellular immunity of 0, 1, 2, and 3 doses of Gardasil vaccine (4vHPV) in girls after 6 years and their responses to a subsequent dose of Cervarix vaccine (2vHPV). Methods A subset of girls (n = 59) who previously received 0, 1, 2, or 3 doses of 4vHPV 6 years earlier were randomly selected from a cohort study of Fijian girls (age 15–19 years). Blood was collected before and 28 days after a dose of 2vHPV. The HPV16- and HPV18-specific cellular immune response was determined by IFNγ-ELISPOT and by measurement of cytokines in peripheral blood mononuclear cell supernatants. Results Six years after 4vHPV vaccination, HPV18-specific responses were significantly lower in the 1- (1D) or 2-dose (2D) recipients compared with 3-dose recipients (2D: IFNγ-ELISPOT: P = .008; cytokines, IFNγ: P = .002; IL-2: P = .022; TNFα: P = .016; IL-10: P = .018; 1D: IL-2: P = .031; IL-10: P = .014). These differences were no longer significant post-2vHPV. No significant differences in HPV16 responses (except IL-2, P < .05) were observed between the 2- or 1-dose recipients and 3-dose recipients. Conclusions These data suggest that cellular immunity following reduced-dose schedules was detectable after 6 years, although the responses were variable between HPV types and dosage groups. The clinical significance of this is unknown. Further studies on the impact of reduced dose schedules are needed, particularly in high–disease burden settings.

Safety, and Humoral and Cell-mediated Immune Responses to Herpes Zoster Vaccine in Patients with Rheumatoid Arthritis

Objective.To examine humoral and cellular immune responses induced by a live attenuated herpes zoster (HZ) vaccine in patients with rheumatoid arthritis (RA) compared with osteoarthritis (OA) patients.Methods.This was an observational study of a live attenuated HZ vaccine in 41 patients with RA receiving conventional disease-modifying antirheumatic drugs (cDMARD) and/or low-dose glucocorticoids (GC) and in 28 patients with OA. Blood samples were obtained before and at 12 weeks after HZ vaccination. Immunogenicity was assessed using varicella zoster virus (VZV)-specific interferon gamma ELISA and an in-house ELISA. Clinical outcomes, including adverse events, HZ occurrence, and RA flares, were analyzed.Results.No patients developed vaccination-induced HZ during the followup period (median = 1.6 yrs). The HZ vaccine induced a significant increase in the VZV-specific enzyme-linked immunospot spot-forming units and anti-VZV immunoglobulin G antibodies in patients with RA and OA. The number of spot-forming units was lower in patients with RA than in patients with OA both at baseline and at 12 weeks after vaccination. The disease activity index for patients with RA was similar at baseline and at 12 weeks after vaccination. However, 6 patients with RA (14.6%) experienced a flare during the 12 weeks. Overall, 17 (24.6%) participants reported a mild adverse event such as an injection site reaction (11.6%).Conclusion.The HZ vaccine induced VZV-specific cellular and humoral responses in patients with RA. Although patients with RA showed a weaker vaccine-induced VZV-specific cellular immune response than patients with OA, the vaccine may be considered in patients with RA receiving cDMARD and/or low dose GC.

Flow Cytometry Assessment of Bacterial and Yeast Induced Oxidative Burst in Peripheral Blood Phagocytes

Objective: The aim of this study was to verify in our laboratory conditions the performance criteria of a commercial kit (PhagoburstTM, Glycotope Biotechnology) as described by the producers. We have also partially altered the use of the available kit by introducing a non-opsonized Candida albicans stimulus, in addition to the opsonized Escherichia coli stimulus provided by the manufacturer. Material and methods: The peripheral blood samples of 6 clinically healthy adults were tested in triplicate according to the manufacturer recommendations. The intraassay imprecision as well as the ranges of neutrophil and monocyte burst activation triggered by various stimuli were assessed. Results: The activation range of granulocytes and monocytes was similar to the one described by the producer in the presence of E. coli (granulocytes: 78.45-99.43% versus 99.6-99.95%, average %CV of 1.53% versus 0.1%, monocytes: 54.63-92.33% versus 81.80-96.67, average %CV 6.92% versus 1.1%). The leukocyte range of activation in the presence of non-opsonized C. albicans was comparable to the one triggered by the fMLP (N-formyl-methionyl-leucyl-phenylalanine) stimulus. Conclusion: The intra-assay precision obtained in our laboratory conditions, as well as the ranges of activated leukocytes, are comparable to the ones described by the producer when using E. coli as a stimulus. The present study shows that introducing an extra fungal stimulus for burst oxidation assessment could provide additional information regarding the non-specific cellular immune response, particularly in patients at risk for candidemia.