Marked Increase in Avidity of SARS-CoV-2 Antibodies 7-8 Months After Infection Is Not Diminished in Old Age

The kinetics of immunoglobulin G (IgG) avidity maturation during severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection obtained from 217 participants of the Ischgl cohort, Austria, was studied 0.5-1.5 months (baseline) and 7-8 months (follow-up) after infection. The IgG avidity assay, using a modified IgG enzyme-linked immunosorbent assay (ELISA) and 5.5 M urea, revealed that old age does not diminish the increase in avidity, detected in all participants positive at both time points, from 18% to 42%. High avidity was associated with a marked residual neutralization capacity in 97.2.% of participants (211/217), which was even higher in the older age group, revealing an important role of avidity assays as easy and cheap surrogate tests for assessing the maturation of the immune system conveying potential protection against further SARS-CoV-2 infections without necessitating expensive and laborious neutralization assays

Third dose of COVID-19 mRNA vaccine closes the gap in immune response between naïve nursing home residents and healthy adults.

peer reviewed[en] BACKGROUND: Nursing home residents, a frail and old population group, respond poorly to primary mRNA COVID-19 vaccination. A third dose has been shown to boost protection against severe disease and death in this immunosenescent population, but limited data is available on the immune responses it induces. METHODS: In this observational cohort study, peak humoral and cellular immune responses were compared 28 days after the second and third doses of the BNT162b2 mRNA COVID-19 vaccine in residents and staff members of two Belgian nursing homes. Only individuals without evidence of previous SARS-CoV-2 infection at third dose administration were included in the study. In addition, an extended cohort of residents and staff members was tested for immune responses to a third vaccine dose and was monitored for vaccine breakthrough infections in the following six months. The trial is registered on ClinicalTrials.gov (NCT04527614). FINDINGS: All included residents (n = 85) and staff members (n = 88) were SARS-CoV-2 infection naïve at third dose administration. Historical blood samples from 28 days post second dose were available from 42 residents and 42 staff members. Magnitude and quality of humoral and cellular immune responses were strongly boosted in residents post third compared to post second dose. Increases were less pronounced in staff members than in residents. At 28 days post third dose, differences between residents and staff had become mostly insignificant. Humoral, but not cellular, responses induced by a third dose were predictive of subsequent incidence of vaccine breakthrough infection in the six months following vaccination. INTERPRETATION: These data show that a third dose of mRNA COVID-19 vaccine largely closes the gap in humoral and cellular immune response observed after primary vaccination between NH residents and staff members but suggest that further boosting might be needed to achieve optimal protection against variants of concern in this vulnerable population group

COVID-19 vaccines based on viral nanoparticles displaying a conserved B-cell epitope show potent immunogenicity and a long-lasting antibody response

The COVID-19 pandemic caused by SARS-CoV-2 sparked intensive research into the development of effective vaccines, 50 of which have been approved thus far, including the novel mRNA-based vaccines developed by Pfizer and Moderna. Although limiting the severity of the disease, the mRNA-based vaccines presented drawbacks, such as the cold chain requirement. Moreover, antibody levels generated by these vaccines decline significantly after 6 months. These vaccines deliver mRNA encoding the full-length spike (S) glycoprotein of SARS-CoV-2, but must be updated as new strains and variants of concern emerge, creating a demand for adjusted formulations and booster campaigns. To overcome these challenges, we have developed COVID-19 vaccine candidates based on the highly conserved SARS CoV-2, 809-826 B-cell peptide epitope (denoted 826) conjugated to cowpea mosaic virus (CPMV) nanoparticles and bacteriophage Qβ virus-like particles, both platforms have exceptional thermal stability and facilitate epitope delivery with inbuilt adjuvant activity. We evaluated two administration methods: subcutaneous injection and an implantable polymeric scaffold. Mice received a prime–boost regimen of 100 μg per dose (2 weeks apart) or a single dose of 200 μg administered as a liquid formulation, or a polymer implant. Antibody titers were evaluated longitudinally over 50 weeks. The vaccine candidates generally elicited an early Th2-biased immune response, which stimulates the production of SARS-CoV-2 neutralizing antibodies, followed by a switch to a Th1-biased response for most formulations. Exceptionally, vaccine candidate 826-CPMV (administered as prime-boost, soluble injection) elicited a balanced Th1/Th2 immune response, which is necessary to prevent pulmonary immunopathology associated with Th2 bias extremes. While the Qβ-based vaccine elicited overall higher antibody titers, the CPMV-induced antibodies had higher avidity. Regardless of the administration route and formulation, our vaccine candidates maintained high antibody titers for more than 50 weeks, confirming a potent and durable immune response against SARS-CoV-2 even after a single dose

Targeting cholesterol esterification as a novel immune checkpoint in viral infections and cancer

Identifying metabolic targets that constrain tumours and viruses while boosting exhausted, dysfunctional T cells can provide novel therapeutic checkpoints. Modulating cholesterol esterification by inhibiting the enzyme acyl-CoA:cholesterol acyltransferase (ACAT) has a direct antitumour and antiviral effect and enhances murine anti-tumour CD8+ T cells. In this thesis, I showed that reduced formation of cholesterol-rich microdomains within the cell membrane (lipid rafts) was a feature of PD-1hi exhausted CD8+ T cells. I therefore investigated the potential for rescuing exhausted human T cells by modulating cholesterol esterification and lipid raft formation. Inhibiting ACAT enhanced the expansion of functional virus- and tumour-specific T cells from donors with chronic hepatitis B virus (HBV) infection, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, and hepatocellular carcinoma. The immune-boosting effect was not limited to circulating T cells but could also enhance the function of T cells directly ex vivo from the immunosuppressive liver and tumour microenvironment in the majority of donors. ACAT inhibition led to a redistribution of intracellular cholesterol with reduced neutral lipid droplets and increased lipid raft formation, resulting in enhanced T cell receptor (TCR) signalling and T cell effector function. Additionally, ACAT inhibition induced TCR-independent bioenergetic rewiring with a skewing towards utilization of oxidative phosphorylation. ACAT inhibition had a complementary effect with other immunotherapies, with increased responsiveness to PD-1 blockade and enhanced functional avidity of TCR-engineered T cells recognizing HBV and tumour cells. Taken together, reduced lipid rafts are a feature of exhausted T cells and modulating cholesterol esterification by ACAT inhibition is a promising novel immunotherapeutic approach to boost exhausted antiviral and antitumour T cells in acute and chronic infection and in cancer

Developing Multivalent Nanoparticle Vaccines Against Current and Future Viruses

The 1918-1919 flu pandemic resulted in an estimated 50 to 100 million deaths worldwide, making it the deadliest pandemic in modern history. It was caused by a new influenza virus that likely spilled over from birds and reassorted with a human influenza virus. Since the human population was immunologically naïve to this virus, transmission and lethality was much higher than for seasonal influenza outbreaks. Numerous pandemic influenza viruses emerged within the next century, with none causing the same amount of carnage. There is likely to be future influenza pandemics, with wild migratory birds being carriers of a wide swath of different influenza A viruses. Zoonotic transmission of Avian influenza has taken place with limited human to human transmission. There is evidence showing that the barrier of human transmissibility by some of these avian viruses is not very high, and therefore emergence into humans is possible, with most if not all of the population immunologically naïve. The humoral immune response to influenza is defined by the imprinting of the antibody response to immunodominant epitopes. Such responses can impair immunity, providing less adequate protection against seasonal and pandemic infections, as well as poorer immunity induced by seasonal vaccines. There are instances where imprinting can be advantageous and even offer protection against pandemic or avian viruses, particularly when conserved epitopes to the HA stalk are exploited. Manipulating the antibody response to recognizing conserved stalk epitopes on influenza HA is therefore a strategy being used for universal influenza vaccines. In the second Chapter of this thesis, a mosaic nanoparticle immunization strategy for inducing breadth of antibody responses against HA will be described. This strategy involves the co-display of HAs from up to eight different strains on a particle platform. Although the breadth of antibody responses elicited by immunization of these particles was limited, this work provides insight into the antigenicity of such particles, and a possible alternative to current influenza vaccines. Approximately 100 years after the 1918-1919 flu pandemic, a deadly SARS-like coronavirus, known as SARS-CoV-2, emerged in the human population resulting in a currently ongoing pandemic. This came less than two decades after the small but deadly SARS outbreak, essentially a warning call for this class of coronaviruses. Other SARS-like coronavirus strains in bats have been identified and shown to be human tropic, though resulting in an attenuated infection. Some of these viruses can infect via hACE2 but there are others that may use an unknown receptor for entry into VERO cells as well as human cell lines. There is evidence that the major barrier to zoonosis is protease compatibility, which could be gained through recombination events or errors during replication. Therefore, future SARS-like coronaviruses (sarbecovirus) may emerge in humans, seeding future outbreaks. The antibody response to SARS-CoV-2 is robust and protective. Furthermore, there is the presence of conserved epitopes particularly on the RBD that can be targeted by antibodies that are cross-neutralizing against many SARS-like coronaviruses. Exploiting these cross-reactive epitopes is one strategy that can be used for developing a universal coronavirus vaccine. In Chapter 3 of this thesis, a similar mosaic nanoparticle immunization strategy will be described, that attempts to elicit cross-reactive antibodies against the SARS-like coronavirus family. The mosaic nanoparticles co-display the RBDs of eight different sarbecovirus strains including SARS-CoV-2. Immunization with these mosaic-RBD nanoparticles elicited polyclonal antibody responses that were cross-reactive as well as cross-neutralizing against sarbecoviruses strains both present and not present on the particles.</p

Viral and host factors mediate influenza vaccine-induced immunity in humans and mouse models

Influenza viruses infect and cause disease in millions of people worldwide every year. Available seasonal influenza vaccines significantly decrease infectivity, transmission, and disease. Most influenza vaccines are inactivated vaccines which generate an antibody-mediated immune response to the influenza hemagglutinin (HA) attachment protein. While HA is immunodominant, the HA antigenic sequence changes each season due to antigenic drift and after each pandemic due to antigenic shift, making vaccine preparedness and protection an immunological moving target and overall vaccine efficacy highly variable. This dissertation explores the various viral and host elements that affect influenza vaccine-induced immunity and protection in two ways: 1) by utilizing human clinical samples and human H3N2 virus isolates from 2017-18 influenza season surveillance to determine the impact that biological sex, age, and vaccination status have on the quality of antibodies generated towards the H3N2 vaccine and circulating viruses, and 2) by utilizing a mouse model and reverse-engineered mouse-adapted H1N1 viruses to assess the relationship between antigenic variation in the influenza HA head and the corresponding antibody response and protection. My thesis research has shown that among H3N2 positive patients, vaccination, younger age, and female sex were associated with greater neutralizing antibody (nAb) responses to the egg-adapted vaccine H3N2 virus, but not to the cell-grown vaccine or circulating viruses. We concluded that for the 2017-18 circulating viruses, mutations introduced by egg-adaptation decreased vaccine efficacy. No increased protection was afforded by vaccination, younger age, or female sex against 2017-18 circulating H3N2 viruses. Additionally, I have shown that female mice benefit from the production of highly class-switched, somatically hyper-mutated antibody by germinal center B cells to recognize diverse H1N1 antigens and be protected against influenza, but that there are limits to the female-biased immunity and protection that are dependent on mutations in the head of H1 HA. This dissertation and its contents serve to further our understanding of the extent of female-biased immunity and protection to influenza viruses after vaccination and help explain why female humans and mice consistently produce greater quality and quantity of vaccine-induced antibodies that mediate protection from influenza virus

Innate and adaptive immunity during SARS-CoV-2 infection: Biomolecular cellular markers and mechanisms

The coronavirus 2019 (COVID-19) pandemic was caused by a positive sense single-stranded RNA (ssRNA) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, other human coronaviruses (hCoVs) exist. Historical pandemics include smallpox and influenza, with efficacious therapeutics utilized to reduce overall disease burden through effectively targeting a competent host immune system response. The immune system is composed of primary/secondary lymphoid structures with initially eight types of immune cell types, and many other subtypes, traversing cell membranes utilizing cell signaling cascades that contribute towards clearance of pathogenic proteins. Other proteins discussed include cluster of differentiation (CD) markers, major histocompatibility complexes (MHC), pleiotropic interleukins (IL), and chemokines (CXC). The historical concepts of host immunity are the innate and adaptive immune systems. The adaptive immune system is represented by T cells, B cells, and antibodies. The innate immune system is represented by macrophages, neutrophils, dendritic cells, and the complement system. Other viruses can affect and regulate cell cycle progression for example, in cancers that include human papillomavirus (HPV: cervical carcinoma), Epstein-Barr virus (EBV: lymphoma), Hepatitis B and C (HB/HC: hepatocellular carcinoma) and human T cell Leukemia Virus-1 (T cell leukemia). Bacterial infections also increase the risk of developing cancer (e.g., Helicobacter pylori). Viral and bacterial factors can cause both morbidity and mortality alongside being transmitted within clinical and community settings through affecting a host immune response. Therefore, it is appropriate to contextualize advances in single cell sequencing in conjunction with other laboratory techniques allowing insights into immune cell characterization. These developments offer improved clarity and understanding that overlap with autoimmune conditions that could be affected by innate B cells (B1(+) or marginal zone cells) or adaptive T cell responses to SARS-CoV-2 infection and other pathologies. Thus, this review starts with an introduction into host respiratory infection before examining invaluable cellular messenger proteins and then individual immune cell markers.Biochem123 Ltd

HCMV carriage in the elderly diminishes anti-viral functionality of the adaptive immune response resulting in virus replication at peripheral sites.

Human cytomegalovirus (HCMV) infection and periodic reactivation is, generally, well controlled by adaptative immune responses in the healthy. In older people, overt HCMV disease is rarely seen despite the association of HCMV with increased risk of mortality; evidence from studies of unwell aged populations suggest that HCMV seropositivity is an important co-morbidity factor. HCMV genomes have been detected in urine from older donors, suggesting that the immune response prevents systemic disease but possibly immunomodulation due to lifelong viral carriage may alter its efficacy at peripheral tissue sites. Previously we have demonstrated that there were no age-related expansions of T cell responses to HCMV or increase in latent viral carriage with age and these T cells produced anti-viral cytokines and viremia was very rarely detected. To investigate the efficacy of anti-HCMV responses with increasing age, we used an in vitro Viral Dissemination Assay (VDA) using autologous dermal fibroblasts to determine the anti-viral effector capacity of total PBMC, as well as important subsets (T cells, NK cells). In parallel we assessed components of the humoral response (antibody neutralization) and combined this with qPCR detection of HCMV in blood, saliva and urine in a cohort of young and old donors. Consistent with previous studies, we again show HCMV specific cIL-10, IFNγ and TNFα T cell responses to peptides did not show an age-related defect. However, assessment of direct anti-viral cellular and antibody-mediated adaptive immune responses using the VDA shows that older donors are significantly less able to control viral dissemination in an in vitro assay compared to young donors. Corroborating this observation, we detected viral genomes in saliva samples only from older donors, these donors had a defect in cellular control of viral spread in our in vitro assay. Phenotyping of fibroblasts used in this study shows expression of a number of checkpoint inhibitor ligands which may contribute to the defects observed. The potential to therapeutically intervene in checkpoint inhibitor pathways to prevent HCMV reactivation in the unwell aged is an exciting avenue to explore