Humoral and cellular immune responses in fully vaccinated individuals with or without SARS-CoV-2 breakthrough infection: Results from the CoV-ADAPT cohort

Despite recent advances in prophylactic vaccination, SARS-CoV-2 infections continue to cause significant morbidity. A better understanding of immune response differences between vaccinated individuals with and without later SARS-CoV-2 breakthrough infection is urgently needed. CoV-ADAPT is a prospective long-term study comparing humoral (anti-spike-RBD-IgG, neutralization capacity, avidity) and cellular (spike-induced T-cell interferon-γ [IFN-γ] release) immune responses in individuals vaccinated against SARS-CoV-2 at four different time points (three before and one after third vaccination). In this cohort study, 62 fully vaccinated individuals presented with SARS-CoV-2 breakthrough infections vs 151 without infection 3-7 months following third vaccination. Breakthrough infections significantly increased anti-spike-RBD-IgG (p < 0.01), but not spike-directed T-cell IFN-γ release (TC) or antibody avidity. Despite comparable surrogate neutralization indices, the functional neutralization capacity against SARS-CoV-2-assessed via a tissue culture-based assay-was significantly higher following breakthrough vs no breakthrough infection. Anti-spike-RBD-IgG and antibody avidity decreased with age (p < 0.01) and females showed higher anti-spike-RBD-IgG (p < 0.01), and a tendency towards higher antibody avidity (p = 0.051). The association between humoral and cellular immune responses previously reported at various time points was lost in subjects after breakthrough infections (p = 0.807). Finally, a machine-learning approach based on our large immunological dataset (a total of 49 variables) from different time points was unable to predict breakthrough infections (area under the curve: 0.55). In conclusion, distinct differences in humoral vs cellular immune responses in fully vaccinated individuals with or without breakthrough infection could be demonstrated. Breakthrough infections predominantly drive the humoral response without boosting the cellular component. Breakthrough infections could not be predicted based on immunological data, which indicates a superior role of environmental factors (e.g., virus exposure) in individualized risk assessment.

The adjuvant effect of polymuramil, a NOD1 and NOD2 agonist, differs when immunizing mice of different inbred lines with nonstructural hepatitis C virus (Flaviviridae: Hepacivirus)proteins and is synergistically enhanced in combination with pyrogenalum, a TLR4 agonist

INTRODUCTION

Hepatitis C is a liver disease with high chronicity, the cause of cirrhosis and hepatocarcinoma. The main obstacle to controlling hepatitis C is the lack of vaccines. The aim of the work was to compare the immunogenic activity of nonstructural recombinant proteins NS3, NS4 and NS5B of hepatitis C virus (HCV) as components of a subunit candidate vaccine and to analyze the adjuvant properties of two available commercial drugs, polymuramil and pyrogenalum.

MATERIALS AND METHODS

BALB/c, DBA/2J and C57BL/6 mice were immunized with nonstructural proteins without adjuvants or with polymuramyl (NOD1 and NOD2 agonist) and pyrogenalum (TLR-4 agonist). The activity of antibodies was determined in ELISA, the cellular response - by antigen-specific lymphocyte proliferation and by production of IFN-γ in vitro.

RESULTS

Recombinant proteins showed different immunogenicity. NS4 induced antibodies more efficiently than NS3 and NS5B. Significant differences were found in the immune response of three inbred lines mice: the level of IFN-γ in BALB/c and DBA/2J mice induced by NS5B protein was 30 times higher than in C57Bl/6 mice. In contrast, the induction of antibodies in BALB/c mice was lower than in C57Bl/6 and DBA/2J. Polymuramil did not increase the humoral response to NS5B and enhanced the cellular response only in C57BL/6 mice. The combined use of polymuramil with pyrogenalum significantly increased both the humoral and cellular response of mice to all recombinant HCV proteins.

CONCLUSION

Different immunogenic properties and different functions of recombinant non-structural HCV proteins indicate the feasibility of their combined inclusion in subunit vaccines. It was established for the first time that immunization with HCV proteins with a complex adjuvant (polymuramyl + pyrogenalum) has a synergistic effect, significantly exceeding the effect of each of them separately.

Biocompatible Lipid Polymer Cationic Nanoparticles for Antigen Presentation

Biocompatible lipid polymer nanoparticles (NPs) previously used as antimicrobial agents are explored here as immuno-adjuvants. Poly (methyl methacrylate) (PMMA)/dioctadecyldimethylammonium bromide (DODAB)/poly (diallyldimethylammonium chloride) (PDDA) nanoparticles (NPs) were prepared by emulsion polymerization of methyl methacrylate (MMA) in the presence of DODAB and PDDA, with azobisisobutyronitrile (AIBN) as the initiator. NPs characterization after dialysis by dynamic light-scattering yielded 225 ± 2 nm hydrodynamic diameter (Dz), 73 ± 1 mV zeta-potential (ζ), and 0.10 ± 0.01 polydispersity (P). Ovalbumin (OVA) adsorption reduced ζ to 45 ± 2 mV. Balb/c mice immunized with NPs/OVA produced enhanced OVA-specific IgG1 and IgG2a, exhibited moderate delayed type hypersensitivity reaction, and enhanced cytokines production (IL-4, IL-10, IL-2, IFN-γ) by cultured spleen cells. There was no cytotoxicity against cultured macrophages and fibroblasts. Advantages of the PMMA/DODAB/PDDA NPs were high biocompatibility, zeta-potential, colloidal stability, and antigen adsorption. Both humoral and cellular antigen-specific immune responses were obtained.

Viral Vector Vaccines against Bluetongue Virus

Bluetongue virus (BTV), the prototype member of the genus Orbivirus (family Reoviridae), is the causative agent of an important livestock disease, bluetongue (BT), which is transmitted via biting midges of the genus Culicoides. To date, up to 29 serotypes of BTV have been described, which are classified as classical (BTV 1–24) or atypical (serotypes 25–27), and its distribution has been expanding since 1998, with important outbreaks in the Mediterranean Basin and devastating incursions in Northern and Western Europe. Classical vaccine approaches, such as live-attenuated and inactivated vaccines, have been used as prophylactic measures to control BT through the years. However, these vaccine approaches fail to address important matters like vaccine safety profile, effectiveness, induction of a cross-protective immune response among serotypes, and implementation of a DIVA (differentiation of infected from vaccinated animals) strategy. In this context, a wide range of recombinant vaccine prototypes against BTV, ranging from subunit vaccines to recombinant viral vector vaccines, have been investigated. This article offers a comprehensive outline of the live viral vectors used against BTV.

Engineering an effective immune adjuvant by designed control of shape and crystallinity of aluminum oxyhydroxide nanoparticles

Adjuvants based on aluminum salts (Alum) are commonly used in vaccines to boost the immune response against infectious agents. However, the detailed mechanism of how Alum enhances adaptive immunity and exerts its adjuvant immune effect remains unclear. Other than being comprised of micrometer-sized aggregates that include nanoscale particulates, Alum lacks specific physicochemical properties to explain activation of the innate immune system, including the mechanism by which aluminum-based adjuvants engage the NLRP3 inflammasome and IL-1β production. This is putatively one of the major mechanisms required for an adjuvant effect. Because we know that long aspect ratio nanomaterials trigger the NLRP3 inflammasome, we synthesized a library of aluminum oxyhydroxide (AlOOH) nanorods to determine whether control of the material shape and crystalline properties could be used to quantitatively assess NLRP3 inflammasome activation and linkage of the cellular response to the material's adjuvant activities in vivo. Using comparison to commercial Alum, we demonstrate that the crystallinity and surface hydroxyl group display of AlOOH nanoparticles quantitatively impact the activation of the NLRP3 inflammasome in human THP-1 myeloid cells or murine bone marrow-derived dendritic cells (BMDCs). Moreover, these in vitro effects were correlated with the immunopotentiation capabilities of the AlOOH nanorods in a murine OVA immunization model. These results demonstrate that shape, crystallinity, and hydroxyl content play an important role in NLRP3 inflammasome activation and are therefore useful for quantitative boosting of antigen-specific immune responses. These results show that the engineered design of aluminum-based adjuvants in combination with dendritic cell property-activity analysis can be used to design more potent aluminum-based adjuvants.

Evaluation of the humoral and cellular immune responses elicited by the live attenuated and inactivated influenza vaccines and their roles in heterologous protection in ferrets

The humoral and cellular immune responses elicited by the trivalent live attenuated influenza vaccine (LAIV) and the trivalent inactivated influenza vaccine (TIV) were evaluated in the ferret model, using newly developed ferret immunological reagents and assays. In contrast to the TIV, which only induced immune responses in primed animals, LAIV induced strong influenza virus-specific serum antibody and T-cell responses in both naive and influenza-seropositive animals. The LAIV offered significant protection against a heterologous H1N1 virus challenge infection in the upper respiratory tract. Influenza virus-specific immunoglobulin A (IgA) and immunoglobulin G (IgG) antibody-secreting cells (ASCs) and influenza virus-specific CD4(+) and CD8(+) T cells were detected in the circulation and local paratracheal draining lymph nodes. The frequency of the influenza-specific ASCs in the local lymph nodes appeared to correlate with the degree of protection in the upper respiratory tract. The protection conferred by the LAIV could be attributed not only to the antibody response but also to the cell-mediated and local mucosal immune responses, particularly in naive ferrets. These findings may explain why the LAIV is immunologically superior and offers immediate protection after a single dose in children.