Human immune responses to influenza virus vaccines administered by systemic or mucosal routes

Pneumonic Plague Protection Induced by a Monophosphoryl Lipid A Decorated Yersinia Outer-Membrane-Vesicle Vaccine

A new Yersinia pseudotuberculosis mutant strain, YptbS46, carrying the lpxE insertion and pmrF-J deletion is constructed and shown to exclusively produce monophosphoryl lipid A (MPLA) having adjuvant properties. Outer membrane vesicles (OMVs) isolated from YptbS46 harboring an lcrV expression plasmid, pSMV13, are designated OMV46-LcrV, which contained MPLA and high amounts of LcrV (Low Calcium response V) and displayed low activation of Toll-like receptor 4 (TLR4). Intramuscular prime-boost immunization with 30 µg of of OMV46-LcrV exhibited substantially reduced reactogenicity than the parent OMV44-LcrV and conferred complete protection to mice against a high-dose of respiratory Y. pestis challenge. OMV46-LcrV immunization induced robust adaptive responses in both lung mucosal and systemic compartments and orchestrated innate immunity in the lung, which are correlated with rapid bacterial clearance and unremarkable lung damage during Y. pestis challenge. Additionally, OMV46-LcrV immunization conferred long-term protection. Moreover, immunization with reduced doses of OMV46-LcrV exhibited further lower reactogenicity and still provided great protection against pneumonic plague. The studies strongly demonstrate the feasibility of OMV46-LcrV as a new type of plague vaccine candidate.

Effect of Tezepelumab on the Humoral Immune Response to Seasonal Quadrivalent Influenza Vaccination in Patients with Moderate to Severe Asthma: The Phase 3b VECTOR Study

INTRODUCTION

Annual influenza vaccinations are recommended for adolescents and adults with moderate to severe asthma. This study investigated the effect of tezepelumab, a human monoclonal antibody that blocks the activity of thymic stromal lymphopoietin, on the humoral immune response to the quadrivalent seasonal influenza vaccine in patients with moderate to severe asthma.

METHODS

VECTOR was a phase 3b, randomized, multicenter, double-blind, parallel-group, placebo-controlled study. Adolescents (aged 12-17 years) and young adults (aged 18-21 years) with moderate to severe asthma were enrolled across 15 centers in the USA. Patients received tezepelumab 210 mg or placebo subcutaneously at weeks 0, 4, 8, and 12, and a single dose of inactivated quadrivalent seasonal influenza vaccine at week 12 before receiving study treatment. Immediately before vaccination and at 4 weeks postvaccination (week 16), strain-specific antibody responses were assessed for four influenza antigens by hemagglutination inhibition (HAI) and microneutralization (MN) assays. Safety was assessed.

RESULTS

Seventy patients were randomized to tezepelumab (n = 35) or placebo (n = 35). There were no meaningful differences in HAI or MN antibody responses between treatment groups at week 16. HAI assay geometric mean fold rises (GMFRs) for influenza strains were 1.76-7.34 for tezepelumab and 1.46-4.75 for placebo. MN assay GMFRs were 4.00-14.56 for tezepelumab and 3.56-10.62 for placebo. In the HAI assay, a fourfold or larger rise in antibody titer from weeks 12 to 16 occurred in 15.2-78.8% and 15.2-51.5% of tezepelumab and placebo recipients, respectively, and 97.0-100% of patients in both treatment groups achieved an antibody titer of at least 40 at week 16. No unexpected safety findings occurred.

CONCLUSION

There was no observed suppression of the humoral immune response after influenza vaccination in adolescents and young adults with moderate to severe asthma treated with tezepelumab. Therefore, the influenza vaccine can be administered to this patient population during tezepelumab treatment.

CLINICALTRIALS

GOV IDENTIFIER

NCT05062759.

Unmasking the potential of secretory IgA and its pivotal role in protection from respiratory viruses

Mucosal immunity has regained its spotlight amidst the ongoing Coronavirus disease 19 (COVID-19) pandemic, with numerous studies highlighting the crucial role of mucosal secretory IgA (SIgA) in protection against Severe acute respiratory syndrome coronavirus-2 or SARS-CoV-2 infections. The observed limitations in the efficacy of currently authorized COVID-19 vaccines in inducing effective mucosal immune responses remind us of the limitations of systemic vaccination in promoting protective mucosal immunity. This resurgence of interest has motivated the development of vaccine platforms capable of enhancing mucosal responses, specifically the SIgA response, and the development of IgA-based therapeutics. Recognizing viral respiratory infections as a global threat, we would like to comprehensively review the existing knowledge on mucosal immunity, with a particular emphasis on SIgA, in the context of SARS-CoV-2, influenza, and Respiratory Syncytial Virus (RSV) infections. This review aims to describe the structural and functional specificities of SIgA, along with its nuanced role in combating influenza, RSV, and SARS-CoV-2 infections. Subsequent sections further elaborate promising vaccine strategies, including mucosal vaccines against Influenza, RSV, and SARS-CoV-2 respiratory viruses, currently undergoing preclinical and clinical development. Additionally, we address the challenges associated with mucosal vaccine development, concluding with a discussion on IgA-based therapeutics as a promising platform for the treatment of viral respiratory infections. This comprehensive review not only synthesizes current insights into mucosal immunity but also identifies critical knowledge gaps, strengthening the way for further advancements in our current understanding and approaches to combat respiratory viral threats.

Role of Acacia catechu and Scutellaria baicalensis in Enhancing Immune Function Following Influenza Vaccination of Healthy Adults: A Randomized, Triple-Blind, Placebo-Controlled Clinical Trial

OBJECTIVE

The study aimed to examine the role of an Acacia catechu and Scutellaria baicalensis formulation, UP446, on supporting immune function in response to influenza vaccination.

METHODS

A randomized, triple-blind, placebo-controlled, parallel study consisted of a 56-day intervention period with a 28-day pre-vaccination period, an influenza vaccination on Day 28 and 28-day post-vaccination period. Fifty healthy adults 40-80 years of age who had not received their flu vaccine were randomized to either UP446 or Placebo. At baseline, Days 28 and 56, immune and oxidative stress markers were measured in blood and a quality of life questionnaire was administered. Participants completed the Wisconsin Upper Respiratory Symptom Survey (WURSS)-24 daily.

RESULTS

In the post-vaccination period, total IgA and IgG levels increased in participants supplemented with UP446 vs. those on Placebo (p ≤ 0.026). As well, influenza B-specific IgG increased 19.4% from Day 28 to 56 and 11.6% from baseline at Day 56 (p ≤ 0.0075). Serum glutathione peroxidase (GSH-Px) was increased in the pre-vaccination period and from baseline at Day 56 with UP446 supplementation (p ≤ 0.0270).

CONCLUSION

These results suggest a 56-day supplementation with UP446 was beneficial in mounting a robust humoral response following vaccination. Increasing GSH-Px in the pre-vaccination period may help improve antioxidant functions and potentially mitigate the oxidative stress induced following vaccination.

Pneumonic plague protection induced by a monophosphoryl lipid A decorated Yersinia outer-membrane-vesicle vaccine

A newly constructed Yersinia pseudotuberculosis mutant (YptbS46) carrying the lpxE insertion and pmrF-J deletion exclusively synthesized an adjuvant form of lipid A, monophosphoryl lipid A (MPLA). Outer membrane vesicles (OMVs) isolated from YptbS46 harboring an lcrV expression plasmid, pSMV13, were designated OMV 46 -LcrV, which contained MPLA and high amounts of LcrV and displayed low activation of Toll-like receptor 4 (TLR4). Similar to the previous OMV 44 -LcrV, intramuscular prime-boost immunization with 30 µg of OMV 46 -LcrV exhibited substantially reduced reactogenicity and conferred complete protection to mice against a high-dose of respiratory Y. pestis challenge. OMV 46 -LcrV immunization induced robust adaptive responses in both lung mucosal and systemic compartments and orchestrated innate immunity in the lung, which were correlated with rapid bacterial clearance and unremarkable lung damage during Y. pestis challenge. Additionally, OMV 46 -LcrV immunization conferred long-term protection. Moreover, immunization with reduced doses of OMV 46 -LcrV exhibited further lower reactogenicity and still provided great protection against pneumonic plague. Our studies strongly demonstrate the feasibility of OMV 46 -LcrV as a new type of plague vaccine candidate.

Evaluation of Anti-S1 IgA Response to Different COVID-19 Vaccination Regimens

IgA plays a crucial role in early virus neutralization. To identify the IgA stimulation by COVID-19 vaccine, this study aimed to evaluate the level of anti-S1 IgA in the serum of participants immunized with different COVID-19 vaccination regimens. Sera from 567 eligible participants vaccinated with two, three, or four doses of different types of COVID-19 vaccine were recruited. Post-vaccine anti-S1 IgA responses significantly varied according to vaccine type and regimen. The finding showed that heterologous boosters, especially after priming with an inactivated vaccine, elicited higher IgA levels than homologous boosters. Vaccination with SV/SV/PF produced the highest IgA level among all the immunization regimens after either two, three, or four doses. The different routes and amounts of vaccine used for vaccination showed non-significant differences in IgA levels. After the third dose of immunization for 4 months, the level of IgA decreased significantly from the level found on day 28 in both SV/SV/AZ and SV/SV/PF groups. In conclusion, our study showed that heterologous booster regimens for COVID-19 elicited higher anti-S1 IgA levels in serum, especially after priming with inactivated vaccine. The presented anti-S1 IgA may have advantages in preventing SARS-CoV-2 infection and severe disease.

Opportunities and challenges of leveraging COVID-19 vaccine innovation and technologies for developing sustainable vaccine manufacturing capabilities in Africa

The COVID-19 pandemic heralded unprecedented resource mobilisation and global scientific collaboration to rapidly develop effective vaccines. Regrettably, vaccine distribution has been inequitable, particularly in Africa where manufacturing capacity remains nominal. To address this, several initiatives are underway to develop and manufacture COVID-19 vaccines in Africa. Nevertheless, diminishing demand for COVID-19 vaccines, the cost competitiveness of producing goods locally, intellectual property rights issues, and complex regulatory environments among other challenges can undermine these ventures. We outline how extending COVID-19 vaccine manufacturing in Africa to include diverse products, multiple vaccine platforms, and advanced delivery systems will ensure sustainability. Possible models, including leveraging public-academic-private partnerships to enhance success of vaccine manufacturing capacity in Africa are also discussed. Intensifying research in vaccine discovery on the continent could yield vaccines that further bolster sustainability of local production, ensuring greater pandemic preparedness in resource-constrained environments, and long-term health systems security.

Long-term systemic and mucosal SARS-CoV-2 IgA response and its association with persistent smell and taste disorders

Introduction

Current approved COVID-19 vaccines, notably mRNA and adenoviral vectored technologies, still fail to fully protect against infection and transmission of various SARS-CoV-2 variants. The mucosal immunity at the upper respiratory tract represents the first line of defense against respiratory viruses such as SARS-CoV-2 and is thus critical to develop vaccine blocking human-to-human transmission.

Methods

We measured systemic and mucosal Immunoglobulin A (IgA) response in serum and saliva from 133 healthcare workers from Percy teaching military hospital following a mild infection (SARS-CoV-2 Wuhan strain, n=58) or not infected (n=75), and after SARS-CoV-2 vaccination (Vaxzevria®/Astrazeneca and/or Comirnaty®/Pfizer).

Results

While serum anti-SARS-CoV-2 Spike IgA response lasted up to 16 months post-infection, IgA response in saliva had mostly fallen to baseline level at 6 months post-infection. Vaccination could reactivate the mucosal response generated by prior infection, but failed to induce a significant mucosal IgA response by itself. Early post-COVID-19 serum anti-Spike-NTD IgA titer correlated with seroneutralization titers. Interestingly, its saliva counterpart positively correlated with persistent smell and taste disorders more than one year after mild COVID-19.

Discussion

As breakthrough infections have been correlated with IgA levels, other vaccine platforms inducing a better mucosal immunity are needed to control COVID-19 infection in the future. Our results encourage further studies to explore the prognosis potential of anti-Spike-NTD IgA in saliva at predicting persistent smell and taste disorders.

Mucosal vaccination: onward and upward

INTRODUCTION

The unique mucosal immune system allows the generation of robust protective immune responses at the front line of pathogen encounters. The needle-free delivery route and cold chain-free logistic requirements also provide additional advantages in ease and economy. However, the development of mucosal vaccines faces several challenges, and only a handful of mucosal vaccines are currently licensed. These vaccines are all in the form of live attenuated or inactivated whole organisms, whereas no subunit-based mucosal vaccine is available.

AREAS COVERED

The selection of antigen, delivery vehicle, route and adjuvants for mucosal vaccination are highly important. This is particularly crucial for subunit vaccines, as they often fail to elicit strong immune responses. Emerging research is providing new insights into the biological and immunological uniqueness of mucosal tissues. However, many aspects of the mucosal immunology still await to be investigated.

EXPERT OPINION

This article provides an overview of the current understanding of mucosal vaccination and discusses the remaining knowledge gaps. We emphasize that because of the potential benefits mucosal vaccines can bring from the biomedical, social and economic standpoints, the unmet goal to achieve mucosal vaccine success is worth the effort.

SARS-CoV-2-specific nasal IgA wanes 9 months after hospitalisation with COVID-19 and is not induced by subsequent vaccination

BACKGROUND

Most studies of immunity to SARS-CoV-2 focus on circulating antibody, giving limited insights into mucosal defences that prevent viral replication and onward transmission. We studied nasal and plasma antibody responses one year after hospitalisation for COVID-19, including a period when SARS-CoV-2 vaccination was introduced.

METHODS

In this follow up study, plasma and nasosorption samples were prospectively collected from 446 adults hospitalised for COVID-19 between February 2020 and March 2021 via the ISARIC4C and PHOSP-COVID consortia. IgA and IgG responses to NP and S of ancestral SARS-CoV-2, Delta and Omicron (BA.1) variants were measured by electrochemiluminescence and compared with plasma neutralisation data.

FINDINGS

Strong and consistent nasal anti-NP and anti-S IgA responses were demonstrated, which remained elevated for nine months (p < 0.0001). Nasal and plasma anti-S IgG remained elevated for at least 12 months (p < 0.0001) with plasma neutralising titres that were raised against all variants compared to controls (p < 0.0001). Of 323 with complete data, 307 were vaccinated between 6 and 12 months; coinciding with rises in nasal and plasma IgA and IgG anti-S titres for all SARS-CoV-2 variants, although the change in nasal IgA was minimal (1.46-fold change after 10 months, p = 0.011) and the median remained below the positive threshold determined by pre-pandemic controls. Samples 12 months after admission showed no association between nasal IgA and plasma IgG anti-S responses (R = 0.05, p = 0.18), indicating that nasal IgA responses are distinct from those in plasma and minimally boosted by vaccination.

INTERPRETATION

The decline in nasal IgA responses 9 months after infection and minimal impact of subsequent vaccination may explain the lack of long-lasting nasal defence against reinfection and the limited effects of vaccination on transmission. These findings highlight the need to develop vaccines that enhance nasal immunity.

FUNDING

This study has been supported by ISARIC4C and PHOSP-COVID consortia. ISARIC4C is supported by grants from the National Institute for Health and Care Research and the Medical Research Council. Liverpool Experimental Cancer Medicine Centre provided infrastructure support for this research. The PHOSP-COVD study is jointly funded by UK Research and Innovation and National Institute of Health and Care Research. The funders were not involved in the study design, interpretation of data or the writing of this manuscript.

Heterologous Systemic Prime–Intranasal Boosting Using a Spore SARS-CoV-2 Vaccine Confers Mucosal Immunity and Cross-Reactive Antibodies in Mice as well as Protection in Hamsters

Background: Current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines are administered systemically and typically result in poor immunogenicity at the mucosa. As a result, vaccination is unable to reduce viral shedding and transmission, ultimately failing to prevent infection. One possible solution is that of boosting a systemic vaccine via the nasal route resulting in mucosal immunity. Here, we have evaluated the potential of bacterial spores as an intranasal boost. Method: Spores engineered to express SARS-CoV-2 antigens were administered as an intranasal boost following a prime with either recombinant Spike protein or the Oxford AZD1222 vaccine. Results: In mice, intranasal boosting following a prime of either Spike or vaccine produced antigen-specific sIgA at the mucosa together with the increased production of Th1 and Th2 cytokines. In a hamster model of infection, the clinical and virological outcomes resulting from a SARS-CoV-2 challenge were ameliorated. Wuhan-specific sIgA were shown to cross-react with Omicron antigens, suggesting that this strategy might offer protection against SARS-CoV-2 variants of concern. Conclusions: Despite being a genetically modified organism, the spore vaccine platform is attractive since it offers biological containment, the rapid and cost-efficient production of vaccines together with heat stability. As such, employed in a heterologous systemic prime–mucosal boost regimen, spore vaccines might have utility for current and future emerging diseases.

Mucosal immunity: The missing link in comprehending SARS-CoV-2 infection and transmission

SARS-CoV-2 is primarily an airborne infection of the upper respiratory tract, which on reaching the lungs causes the severe acute respiratory disease, COVID-19. Its first contact with the immune system, likely through the nasal passages and Waldeyer's ring of tonsils and adenoids, induces mucosal immune responses revealed by the production of secretory IgA (SIgA) antibodies in saliva, nasal fluid, tears, and other secretions within 4 days of infection. Evidence is accumulating that these responses might limit the virus to the upper respiratory tract resulting in asymptomatic infection or only mild disease. The injectable systemic vaccines that have been successfully developed to prevent serious disease and its consequences do not induce antibodies in mucosal secretions of naïve subjects, but they may recall SIgA antibody responses in secretions of previously infected subjects, thereby helping to explain enhanced resistance to repeated (breakthrough) infection. While many intranasally administered COVID vaccines have been found to induce potentially protective immune responses in experimental animals such as mice, few have demonstrated similar success in humans. Intranasal vaccines should have advantage over injectable vaccines in inducing SIgA antibodies in upper respiratory and oral secretions that would not only prevent initial acquisition of the virus, but also suppress community spread via aerosols and droplets generated from these secretions.

Sublingual Vaccination with Live Influenza Virus Induces Better Protection Than Oral Immunization in Mice

Both sublingual (SL) and oral vaccine administration modalities are convenient, easy, and safe. Here, we have investigated the differences in vaccine efficacy that are induced by oral and sublingual immunization with live influenza virus (A/Hong Kong/1/1968, H3N2) in mice. Intranasally administering a lethal dose of the influenza virus resulted in the deaths of the mice, whereas viral replication in the lungs did not occur upon SL or oral administration. At 30 days post-immunization through the SL or oral route, the mice were intranasally challenge-infected with the lethal dose of the homologous influenza virus. Both SL and oral immunizations with the influenza virus elicited significantly higher levels of virus-specific IgG and IgA antibody responses, as well as HAI titers in the sera. Upon challenge infection, the SL immunization elicited higher levels of pulmonary IgG antibody and CD8⁺ T cell responses than the oral immunization. Enhanced splenic germinal center B (GC B) and B cell proliferation were also detected from the SL immunization, both of which were significantly greater than those of the oral immunization. Importantly, compared to oral immunization, significantly lessened lung viral loads and bodyweight reductions were observed from the SL immunization and these parameters contributed to prolonging the survival of the immunized mice. These results indicate that both SL and oral administration could be effective routes in inducing protective immunity against influenza virus infection, with SL immunization being the better of the two delivery routes.

Intramuscular mRNA BNT162b2 vaccine against SARS-CoV-2 induces neutralizing salivary IgA

Intramuscularly administered vaccines stimulate robust serum neutralizing antibodies, yet they are often less competent in eliciting sustainable "sterilizing immunity" at the mucosal level. Our study uncovers a strong temporary neutralizing mucosal component of immunity, emanating from intramuscular administration of an mRNA vaccine. We show that saliva of BNT162b2 vaccinees contains temporary IgA targeting the receptor-binding domain (RBD) of severe acute respiratory syndrome coronavirus-2 spike protein and demonstrate that these IgAs mediate neutralization. RBD-targeting IgAs were found to associate with the secretory component, indicating their bona fide transcytotic origin and their polymeric multivalent nature. The mechanistic understanding of the high neutralizing activity provided by mucosal IgA, acting at the first line of defense, will advance vaccination design and surveillance principles and may point to novel treatment approaches and new routes of vaccine administration and boosting.

Elderly Subjects Supplemented with L-Glutamine Shows an Improvement of Mucosal Immunity in the Upper Airways in Response to Influenza Virus Vaccination

BACKGROUND

Although glutamine is able to improve the immune response, its action in the upper airway immunity against the influenza virus vaccine remains unclear. Therefore, we aimed to evaluate the L-glutamine supplementation effect on the mucosal immune/inflammatory response of elderly subjects vaccinated against the influenza virus.

METHODS

Saliva sampling from 83 physically active elderly volunteers were collected pre- and 30 days after influenza virus vaccination and supplementation with L-glutamine (Gln, n = 42) or placebo (PL, n = 41).

RESULTS

Gln group showed higher salivary levels of interleukin (IL)-17, total secretory immunoglobulin A (SIgA), and specific-SIgA post-vaccination than values found pre-vaccination and in the PL group post-vaccination. Whereas higher salivary levels of IL-6 and IL-10 were observed post-vaccination in the Gln group, IL-37 levels were lower post-vaccination in both groups than the values pre-vaccination. Tumor necrosis factor (TNF)-α levels were unchanged. Positive correlations between IL-6 and IL-10 were found in all volunteer groups pre- and post-vaccination and also between IL-17 and IL-6 or IL-10 in the Gln group post-vaccination. A negative correlation between IL-37 and IL-10 was found pre- and post-vaccination in the PL group.

CONCLUSION

Gln supplementation was able to modulate salivary cytokine profile and increase SIgA levels, both total and specific to the influenza virus vaccine, in physically active elderly subjects.

Mucosal Immunity in COVID-19: A Neglected but Critical Aspect of SARS-CoV-2 Infection

The mucosal immune system is the largest component of the entire immune system, having evolved to provide protection at the main sites of infectious threat: the mucosae. As SARS-CoV-2 initially infects the upper respiratory tract, its first interactions with the immune system must occur predominantly at the respiratory mucosal surfaces, during both inductive and effector phases of the response. However, almost all studies of the immune response in COVID-19 have focused exclusively on serum antibodies and systemic cell-mediated immunity including innate responses. This article proposes that there is a significant role for mucosal immunity and for secretory as well as circulating IgA antibodies in COVID-19, and that it is important to elucidate this in order to comprehend especially the asymptomatic and mild states of the infection, which appear to account for the majority of cases. Moreover, it is possible that mucosal immunity can be exploited for beneficial diagnostic, therapeutic, or prophylactic purposes.

Salivary anti-SARS-CoV-2 IgA as an accessible biomarker of mucosal immunity against COVID-19

Background

Mucosal immunity, including secretory IgA (sIgA), plays an important role in early defenses against respiratory pathogens. Salivary testing, the most convenient way to measure sIgA, has been used to characterize mucosal immune responses to many viral infections including SARS, MERS, influenza, HIV, and RSV. However, its role has not yet been characterized in the COVID-19 pandemic. Here, we report development and validation of a rapid immunoassay for measuring salivary IgA against the SARS-CoV-2 virus, and report quantitative results in both pre-COVID-19 and muco-converted subjects.

Methods

We developed and refined a specific test for salivary IgA against SARS-CoV-2 on the Brevitest platform, a rapid immunoassay system designed for point-of-care use. A qualitative test was validated as per FDA guidelines with saliva obtained from subjects prior to the emergence of COVID-19, and from PCR-confirmed COVID-19 patients. We also generated a quantitative measure of anti-SARS-CoV-2 salivary IgA. Time taken for saliva self-collection was measured and its ease-of-use assessed.

Results

We successfully validated a qualitative salivary assay for SARS-CoV-2 IgA antibodies, with positive and negative predictive values of 92% and 97%, respectively, and no observable cross-reactivity with any of seven potential confounders. Pre-COVID-19 saliva samples showed an 8-fold range of IgA concentrations, suggesting a broad continuum of natural antibody resistance against the novel virus, though at levels lower than that observed in COVID-19 PCR-confirmed subjects. Samples from muco-positive subjects also shown a ~9-fold variation in salivary IgA levels, with elevated salivary IgA observed beyond three months after onset of symptoms. We observed a correlation (r=0.4405) between salivary IgA levels and COVID-19 disease severity. In anecdotal observations, we observed individuals who exhibited antibodies early in the course of their disease, contemporaneously with a positive PCR test, as well as individuals who muco-converted despite no known direct exposure to a COVID-19 patient, no symptoms, and negative molecular and/or serum antibody tests. Salivary collection took 5-10 minutes, and was reported as being easy (mean of 1.1 on a scale of 1 to 10).

Implications

Mucosal immunity, including secretory IgA, plays an important role in host defense against respiratory pathogens, and our early data suggest it may do so in COVID-19. Salivary IgA, an accessible marker of mucosal immunity, may be a useful indicator of several key parameters including individual and community immune response, disease severity, clinical risk, and herd immunity. The non-invasive nature and ease of saliva collection facilitates its potential use as a biomarker for ongoing patient assessment and management, as well as a community surveillance tool. By measuring mucosal immune responses directly and systemic immune responses indirectly, salivary IgA could be useful in developing and deploying a vaccine(s) against COVID-19. Quantitative IgA assessment could also potentially serve as a tool to segment the population into different risk categories and inform individual and collective decisions relating to appropriate activities and vaccine prioritization/delivery. These data reinforce the importance of further investigation into the role of mucosal immunity and IgA in host responses against COVID-19.

On the influenza vaccination policy through mathematical modeling

OBJECTIVES

Aimed at mitigating influenza transmission, this study assessed the timing of the vaccination program and took vaccine capacity, strain mismatch and priority group into consideration.

METHODS

An age-structured dynamic transmission model was fitted to the laboratory data of the national influenza surveillance system to reconstruct a baseline scenario with which the vaccination scenarios of interest could be compared. Outcome measures were defined as the impacts on the seasonal epidemic: decompression of the epidemic peak, reduction of the epidemic burden and change of the epidemic peak time.

RESULTS

It was found that vaccine capacity building, although indispensable, could not guarantee substantial impact on the seasonal influenza epidemic. Vaccine mismatch might greatly offset vaccine capacity building. Notably, advance vaccine distribution could compensate for some vaccine underperformance. In the case of a well-matched vaccine, advance vaccine distribution could even exploit its utility.

CONCLUSIONS

This study indicated that timely vaccine distribution should be put high on the agenda of seasonal influenza control policies. It provided a tangible platform for the policymakers to evaluate health policy impacts and to enhance risk communication with the public through mathematical modeling.

Immune surveillance for vaccine-preventable diseases

INTRODUCTION

Immunesurveillance is an important tool to monitor the protection of the population against vaccine-preventable diseases, which is currently mostly based on the detection of specific serum antibodies. However, the landscape of immune surveillance is changing, driven by emerging and evolving pathogens, changes in the age distribution of the population and scientific understanding of protective immunity, necessitating a comprehensive review.

AREAS COVERED

To anticipate these changes, reliable and high-throughput detection of antibody levels is desired to enable screening in larger population settings. Antibody levels alone do not always equate with protection and may require additional functional testing of the antibodies or immune cell-based assays. In addition, the location (systemic or locally mucosal) of the infection and whether the antibodies are induced through infection or vaccination have implications for both immune protection and assessing immune status.

EXPERT COMMENTARY

In order to perform multicenter studies on many samples for multiple antigens, more validated reference materials and wider adoption of high-throughput techniques are needed. The field of serosurveillance will also benefit from better correlates of protection and understanding of (local) mechanisms of protection. Here we give an overview of the current state-of-the-art of serosurveillance and how the field could move forward.

Adjuvants and delivery systems based on polymeric nanoparticles for mucosal vaccines

Most pathogens enter the body through mucosal surfaces. Therefore, vaccination through the mucosal route can greatly enhance the mucosal immune response. Vaccination via the mucosal surface is the most effective way to trigger a protective mucosal immune response, but the vast majority of vaccines used are administered by injection. Strategies to enhance the mucosal immunity have been developed by using vaccine adjuvants, delivery systems, bacterial or viral vectors, and DNA vaccines. Appropriate vaccine adjuvants and drug delivery systems can improve the immunogenicity of antigens, induce a stronger immune response, and reduce the vaccine dose and production cost. In recent years, many studies have focused on finding safe and effective vaccine adjuvants and drug delivery systems to formulate the mucosal vaccines for solving the above problems. Great progress has also been made in vaccine adjuvants and drug delivery systems based on biodegradable polymer nanoparticles. In this paper, the research progress of the mucosal vaccine and its related adjuvants and drug delivery systems in recent years was reviewed, and the application of polymers as adjuvants and drug delivery system in vaccine was prospected. This review provides a fundamental knowledge for the application of biodegradable polymer nanoparticles as adjuvants and carriers in mucosal vaccines and shows great application prospects.

Recent Approaches for Solid Dose Vaccine Delivery

Recent studies on vaccine delivery systems are exploring the possibility of replacing liquid vaccines with solid dose vaccines due to the many advantages that solid dose vaccines can offer. These include the prospect of a needle-free vaccine delivery system leading to better patient compliance, cold chain storage, less-trained vaccinators and fewer chances for needle stick injury hazards. Some studies also indicate that vaccines in a solid dosage form can result in a higher level of immunogenicity compared to the liquid form, thus providing a dose-sparing effect. This review outlines the different approaches in solid vaccine delivery using various routes of administration including, oral, pulmonary, intranasal, buccal, sublingual, and transdermal routes. The various techniques and their current advancements will provide a knowledge base for future work to be carried out in this arena.

Remembrance of Things Past: Long-Term B Cell Memory After Infection and Vaccination

The success of vaccines is dependent on the generation and maintenance of immunological memory. The immune system can remember previously encountered pathogens, and memory B and T cells are critical in secondary responses to infection. Studies in mice have helped to understand how different memory B cell populations are generated following antigen exposure and how affinity for the antigen is determinant to B cell fate. Additionally, such studies were fundamental in defining memory B cell niches and how B cells respond following subsequent exposure with the same antigen. On the other hand, human studies are essential to the development of better, newer vaccines but sometimes limited by the difficulty to access primary and secondary lymphoid organs. However, work using human influenza and HIV virus infection and/or immunization in particular has significantly advanced today's understanding of memory B cells. This review will focus on the generation, function, and longevity of B-cell mediated immunological memory (memory B cells and plasma cells) in response to infection and vaccination both in mice and in humans.

How to assess the effectiveness of nasal influenza vaccines? Role and measurement of sIgA in mucosal secretions

Secretory IgAs (sIgA) constitute the principal isotype of antibodies present in nasal and mucosal secretions. They are secreted by plasma cells adjacent to the mucosal epithelial cells, the site where infection occurs, and are the main humoral mediator of mucosal immunity. Mucosally delivered vaccines, such as live attenuated influenza vaccine (LAIV), are able to mimic natural infection without causing disease or virus transmission and mainly elicit a local immune response. The measurement of sIgA concentrations in nasal swab/wash and saliva samples is therefore a valuable tool for evaluating their role in the effectiveness of such vaccines. Here, we describe two standardized assays (enzyme‐linked immunosorbent assay and microneutralization) available for the quantification of sIgA and discuss the advantages and limitations of their use.

Differential transcriptome and development of human peripheral plasma cell subsets

Human antibody-secreting cells (ASCs) triggered by immunization are globally recognized as CD19loCD38hiCD27hi. Yet, different vaccines give rise to antibody responses of different longevity, suggesting ASC populations are heterogeneous. We define circulating-ASC heterogeneity in vaccine responses using multicolor flow cytometry, morphology, VH repertoire, and RNA transcriptome analysis. We also tested differential survival using a human cell-free system that mimics the bone marrow (BM) microniche. In peripheral blood, we identified 3 CD19+ and 2 CD19- ASC subsets. All subsets contributed to the vaccine-specific responses and were characterized by in vivo proliferation and activation. The VH repertoire demonstrated strong oligoclonality with extensive interconnectivity among the 5 subsets and switched memory B cells. Transcriptome analysis showed separation of CD19+ and CD19- subsets that included pathways such as cell cycle, hypoxia, TNF-α, and unfolded protein response. They also demonstrated similar long-term in vitro survival after 48 days. In summary, vaccine-induced ASCs with different surface markers (CD19 and CD138) are derived from shared proliferative precursors yet express distinctive transcriptomes. Equal survival indicates that all ASC compartments are endowed with long-lived potential. Accordingly, in vivo survival of peripheral long-lived plasma cells may be determined in part by their homing and residence in the BM microniche.

Spec-seq unveils transcriptional subpopulations of antibody-secreting cells following influenza vaccination

Vaccines are among the most effective public health tools for combating certain infectious diseases such as influenza. The role of the humoral immune system in vaccine-induced protection is widely appreciated; however, our understanding of how antibody specificities relate to B cell function remains limited due to the complexity of polyclonal antibody responses. To address this, we developed the Spec-seq framework, which allows for simultaneous monoclonal antibody (mAb) characterization and transcriptional profiling from the same single cell. Here, we present the first application of the Spec-seq framework, which we applied to human plasmablasts after influenza vaccination in order to characterize transcriptional differences governed by B cell receptor (BCR) isotype and vaccine reactivity. Our analysis did not find evidence of long-term transcriptional specialization between plasmablasts of different isotypes. However, we did find enhanced transcriptional similarity between clonally related B cells, as well as distinct transcriptional signatures ascribed by BCR vaccine recognition. These data suggest IgG and IgA vaccine-positive plasmablasts are largely similar, whereas IgA vaccine-negative cells appear to be transcriptionally distinct from conventional, terminally differentiated, antigen-induced peripheral blood plasmablasts.

Activation and Induction of Antigen-Specific T Follicular Helper Cells Play a Critical Role in Live-Attenuated Influenza Vaccine-Induced Human Mucosal Anti-influenza Antibody Response

There is increasing interest recently in developing intranasal vaccines against respiratory tract infections. The antibody response is critical for vaccine-induced protection, and T follicular helper cells (T_FH) are considered important for mediating the antibody response. Most data supporting the role for T_FH in the antibody response are from animal studies, and direct evidence from humans is limited, apart from the presence of T_FH-like cells in blood. We studied the activation and induction of T_FH and their role in the anti-influenza antibody response induced by a live-attenuated influenza vaccine (LAIV) in human nasopharynx-associated lymphoid tissue (NALT). T_FH activation in adenotonsillar tissues was analyzed by flow cytometry, and anti-hemagglutinin (anti-HA) antibodies were examined following LAIV stimulation of tonsillar mononuclear cells (MNC). Induction of antigen-specific T_FH by LAIV was studied by flow cytometry analysis of induced T_FH and CD154 expression. LAIV induced T_FH proliferation, which correlated with anti-HA antibody production, and T_FH were shown to be critical for the antibody response. Induction of T_FH from naive T cells by LAIV was shown in newly induced T_FH expressing BCL6 and CD21, followed by the detection of anti-HA antibodies. Antigen specificity of LAIV-induced T_FH was demonstrated by expression of the antigen-specific T cell activation marker CD154 upon challenge by H1N1 virus antigen or HA. LAIV-induced T_FH differentiation was inhibited by BCL6, interleukin-21 (IL-21), ICOS, and CD40 signaling blocking, and that diminished anti-HA antibody production. In conclusion, we demonstrated the induction by LAIV of antigen-specific T_FH in human NALT that provide critical support for the anti-influenza antibody response. Promoting antigen-specific T_FH in NALT by use of intranasal vaccines may provide an effective vaccination strategy against respiratory infections in humans.

IMPORTANCE Airway infections, such as influenza, are common in humans. Intranasal vaccination has been considered a biologically relevant and effective way of immunization against airway infection. The vaccine-induced antibody response is crucial for protection against infection. Recent data from animal studies suggest that one type of T cells, T_FH, are important for the antibody response. However, data on whether T_FH-mediated help for antibody production operates in humans are limited due to the lack of access to human immune tissue containing T_FH. In this study, we demonstrate the induction of T_FH in human immune tissue, providing critical support for the anti-influenza antibody response, by use of an intranasal influenza vaccine. Our findings provide direct evidence that T_FH play a critical role in vaccine-induced immunity in humans and suggest a novel strategy for promoting such cells by use of intranasal vaccines against respiratory infections.

Parenterally Administered Norovirus GII.4 Virus-Like Particle Vaccine Formulated with Aluminum Hydroxide or Monophosphoryl Lipid A Adjuvants Induces Systemic but Not Mucosal Immune Responses in Mice

Norovirus (NoV) is a main cause of acute gastroenteritis across all ages worldwide. NoV vaccine candidates currently in clinical trials are based on noninfectious highly immunogenic virus-like particles (VLPs) delivered intramuscularly (IM). Since NoV is an enteric pathogen, it is likely that mucosal immunity has a significant role in protection from infection in the intestine. Due to the fact that IM delivery of NoV VLPs does not generate mucosal immunity, we investigated whether NoV genotype GII.4 VLPs coadministered with aluminum hydroxide (Al(OH)₃) or monophosphoryl lipid A (MPLA) would induce mucosal antibodies in mice. Systemic as well as mucosal IgG and IgA antibodies in serum and intestinal and nasal secretions were measured. As expected, strong serum IgG, IgG1, and IgG2a antibodies as well as a dose sparing effect were induced by both Al(OH)₃ and MPLA, but no mucosal IgA antibodies were detected. In contrast, IN immunization with GII.4 VLPs without an adjuvant induced systemic as well as mucosal IgA antibody response. These results indicate that mucosal delivery of NoV VLPs is needed for induction of mucosal responses.

Development of a nanogel-based nasal vaccine as a novel antigen delivery system

INTRODUCTION

Nasal vaccination is one of the most effective immunization methods because it can induce effective antigen-specific immune responses not only at the mucosal site of administration but also at distant mucosal surfaces, as well as in the systemic compartment. Based on this advantage, many nasal vaccines are being developed and some have been licensed and marketed for clinical use. However, some have been withdrawn because of unacceptable adverse events such as inactivated influenza vaccine administrated with a heat-labile enterotoxin of Escherichia coli as an adjuvant. Thus, it is important to consider both the efficacy and safety of nasal vaccines. Areas covered: This review describes the benefits of cholesteryl group-bearing pullulan (CHP) nanogels for nasal vaccine delivery and vaccine development identified on Pubmed database with the term 'Nanogel-based nasal vaccine'. Expert commentary: CHP nanogels have been developed as novel drug delivery system, and a cationic CHP nanogels have been demonstrated to induce effective immunity as a nasal vaccine antigen carrier. Since vaccine antigens incorporated into CHP nanogels have exhibited no brain deposition after nasal administration in mice and nonhuman primates, the vaccine seems safe, and could be a promising new delivery system.

Pilot investigation into the sickness response to influenza vaccination in adults: Effect of depression and anxiety

OBJECTIVE

To determine whether depressed or anxious patients experience greater affective change than mentally healthy individuals following influenza vaccination.

METHODS

Participants (n=112) completed the Positive and Negative Affect Schedule (PANAS) before influenza vaccination and 1-2days post-vaccination (M=32.3h). Pre- and post-vaccination PANAS scores were compared using two-tailed, paired-samples t-tests. Change in positive affect between participants with depression or anxiety and those without was compared using two-way ANOVA. Follow up positive affect was further examined using multiple linear regression.

RESULTS

Positive affect decreased following vaccination (M=2.18, 95% CI [1.07, 3.29], t(111)=3.89, p<0.001) for all participants and was more pronounced for those with anxiety or depression (F(1, 110)=7.51, p=0.009). Similarly, predicted follow up affect score was higher for those without a mental health conditions (β=3.67, 95% CI [1.18, 6.16], t(103)=2.92, p=0.004).

CONCLUSIONS

These data suggest that influenza vaccine has a greater effect on affect in patients with depression and anxiety than in mentally healthy individuals. This effect was focused on positive affect, suggesting that influenza vaccine induced inflammation may be best suited to examine alterations in positive affect and positive valence systems.

A novel whole-bacterial enzyme linked-immunosorbant assay to quantify Chlamydia trachomatis specific antibodies reveals distinct differences between systemic and genital compartments

Chlamydia trachomatis (CT) is the leading sexually transmitted bacterial infection. The continued global burden of CT infection strongly predicates the need for a vaccine to supplement current chlamydial control programs. The correlates of protection against CT are currently unknown, but they must be carefully defined to guide vaccine design. The localized nature of chlamydial infection in columnar epithelial cells of the genital tract necessitates investigation of immunity at the site of infection. The purpose of this study was to develop a sensitive whole bacterial enzyme-linked immunosorbent assay (ELISA) to quantify and compare CT-specific IgG and IgA in sera and genital secretions from CT-infected women. To achieve this, elementary bodies (EBs) from two of the most common genital serovars (D and E) were attached to poly-L-lysine-coated microtiter plates with glutaraldehyde. EB attachment and integrity were verified by the presence of outer membrane antigens and the absence of bacterial cytoplasmic antigens. EB-specific IgG and IgA standards were developed by pooling sera with high titers of CT-specific antibodies from infected women. Serum, endocervical and vaginal secretions, and endocervical cytobrush specimens from CT-infected women were used to quantify CT-specific IgG and IgA which were then normalized to total IgG and IgA, respectively. Analyses of paired serum and genital samples revealed significantly higher proportions of EB-specific antibodies in genital secretions compared to sera. Cervical and vaginal secretions and cytobrush specimens had similar proportions of EB-specific antibodies, suggesting any one of these genital sampling techniques could be used to quantify CT-specific antibodies when appropriate normalization methodologies are implemented. Overall, these results illustrate the need to investigate genital tract CT antibody responses, and our assay provides a useful quantitative tool to assess natural immunity in defined clinical groups and CT vaccine trials.

Data-driven interdisciplinary mathematical modelling quantitatively unveils competition dynamics of co-circulating influenza strains

BACKGROUND

Co-circulation of influenza strains is common to seasonal epidemics and pandemic emergence. Competition was considered involved in the vicissitudes of co-circulating influenza strains but never quantitatively studied at the human population level. The main purpose of the study was to explore the competition dynamics of co-circulating influenza strains in a quantitative way.

METHODS

We constructed a heterogeneous dynamic transmission model and ran the model to fit the weekly A/H1N1 influenza virus isolation rate through an influenza season. The construction process started on the 2007-2008 single-clade influenza season and, with the contribution from the clade-based A/H1N1 epidemiological curves, advanced to the 2008-2009 two-clade influenza season. Pearson method was used to estimate the correlation coefficient between the simulated epidemic curve and the observed weekly A/H1N1 influenza virus isolation rate curve.

RESULTS

The model found the potentially best-fit simulation with correlation coefficient up to 96% and all the successful simulations converging to the best-fit. The annual effective reproductive number of each co-circulating influenza strain was estimated. We found that, during the 2008-2009 influenza season, the annual effective reproductive number of the succeeding A/H1N1 clade 2B-2, carrying H275Y mutation in the neuraminidase, was estimated around 1.65. As to the preceding A/H1N1 clade 2C-2, the annual effective reproductive number would originally be equivalent to 1.65 but finally took on around 0.75 after the emergence of clade 2B-2. The model reported that clade 2B-2 outcompeted for the 2008-2009 influenza season mainly because clade 2C-2 suffered from a reduction of transmission fitness of around 71% on encountering the former.

CONCLUSIONS

We conclude that interdisciplinary data-driven mathematical modelling could bring to light the transmission dynamics of the A/H1N1 H275Y strains during the 2007-2009 influenza seasons worldwide and may inspire us to tackle the continually emerging drug-resistant A/H1N1pdm09 strains. Furthermore, we provide a prospective approach through mathematical modelling to solving a seemingly unintelligible problem at the human population level and look forward to its application at molecular level through bridging the resolution capacities of related disciplines.

Comparisons of the Humoral and Cellular Immune Responses Induced by Live Attenuated Influenza Vaccine and Inactivated Influenza Vaccine in Adults

Both live attenuated influenza vaccines (LAIV) and inactivated influenza vaccines (IIV) induce protective immunity against influenza. There is evidence that LAIV induces superior protection in children, whereas IIV may induce superior protection in adults. The immune mechanisms responsible for these differences have not been identified. We previously compared LAIV and IIV in young children of 6 to 36 months of age, and we demonstrated that while both induced similar hemagglutination inhibition (HAI) antibody responses, only LAIV induced significant increases in T cell responses. In the present study, 37 healthy adult subjects of 18 to 49 years of age were randomized to receive seasonal influenza vaccination with LAIV or IIV. Influenza virus-specific HAI, T cell, and secretory IgA (sIgA) responses were studied pre- and postvaccination. In contrast to the responses seen in young children, LAIV induced only minimal increases in serum HAI responses in adults, which were significantly lower than the responses induced by IIV. Both LAIV and IIV similarly induced only transient T cell responses to replication-competent whole virus in adults. In contrast, influenza virus-specific sIgA responses were induced more strongly by LAIV than by IIV. Our previous studies suggest that LAIV may be more protective than IIV in young children not previously exposed to influenza virus or influenza vaccines due to increased vaccine-induced T cell and/or sIgA responses. Our current work suggests that in adults with extensive and partially cross-reactive preexisting influenza immunity, LAIV boosting of sIgA responses to hemagglutinin (HA) and non-HA antigenic targets expressed by circulating influenza virus strains may be an important additional mechanism of vaccine-induced immunity.

Microfabrication for Drug Delivery

This review is devoted to discussing the application of microfabrication technologies to target challenges encountered in life processes by the development of drug delivery systems. Recently, microfabrication has been largely applied to solve health and pharmaceutical science issues. In particular, fabrication methods along with compatible materials have been successfully designed to produce multifunctional, highly effective drug delivery systems. Microfabrication offers unique tools that can tackle problems in this field, such as ease of mass production with high quality control and low cost, complexity of architecture design and a broad range of materials. Presented is an overview of silicon- and polymer-based fabrication methods that are key in the production of microfabricated drug delivery systems. Moreover, the efforts focused on studying the biocompatibility of materials used in microfabrication are analyzed. Finally, this review discusses representative ways microfabrication has been employed to develop systems delivering drugs through the transdermal and oral route, and to improve drug eluting implants. Additionally, microfabricated vaccine delivery systems are presented due to the great impact they can have in obtaining a cold chain-free vaccine, with long-term stability. Microfabrication will continue to offer new, alternative solutions for the development of smart, advanced drug delivery systems.

Parenteral Vaccination Can Be an Effective Means of Inducing Protective Mucosal Responses

The current paradigm in vaccine development is that nonreplicating vaccines delivered parenterally fail to induce immune responses in mucosal tissues. However, both clinical and experimental data have challenged this concept, and numerous studies have shown that induction of mucosal immune responses after parenteral vaccination is not a rare occurrence and might, in fact, significantly contribute to the protection against mucosal infections afforded by parenteral vaccines. While the mechanisms underlying this phenomenon are not well understood, the realization that parenteral vaccination can be an effective means of inducing protective mucosal responses is paradigm-shifting and has potential to transform the way vaccines are designed and delivered.

A critical role of T follicular helper cells in human mucosal anti-influenza response that can be enhanced by immunological adjuvant CpG-DNA

T Follicular helper cells (TFH) are considered critical for B cell antibody response, and recent efforts have focused on promoting TFH in order to enhance vaccine efficacy. We studied the frequency and function of TFH in nasopharynx-associated lymphoid tissues (NALT) from children and adults, and its role in anti-influenza antibody response following stimulation by a live-attenuated influenza vaccine (LAIV) or an inactivated seasonal virus antigen (sH1N1). We further studied whether CpG-DNA promotes TFH and by which enhances anti-influenza response. We showed NALT from children aged 1.5-10 years contained abundant TFH, suggesting efficient priming of TFH during early childhood. Stimulation by LAIV induced a marked increase in TFH that correlated with a strong production of anti-hemagglutinin (HA) IgA/IgG/IgM antibodies in tonsillar cells. Stimulation by the inactivated sH1N1 antigen induced a small increase in TFH which was markedly enhanced by CpG-DNA, accompanied by enhanced anti-HA antibody responses. In B cell co-culture experiment, anti-HA responses were only seen in the presence of TFH, and addition of plasmacytoid dendritic cell to TFH-B cell co-culture enhanced the TFH-mediated antibody production following CpG-DNA and sH1N1 antigen stimulation. Induction of TFH differentiation from naïve T cells was also shown following the stimulation. Our results support a critical role of TFH in human mucosal anti-influenza antibody response. Use of an adjuvant such as CpG-DNA that has the capacity to promote TFH by which to enhance antigen-induced antibody responses in NALT tissue may have important implications for future vaccination strategies against respiratory pathogens.

Co-delivery of GPI-anchored CCL28 and influenza HA in chimeric virus-like particles induces cross-protective immunity against H3N2 viruses

Influenza infection typically initiates at respiratory mucosal surfaces. Induction of immune responses at the sites where pathogens initiate replication is crucial for the prevention of infection. We studied the adjuvanticity of GPI-anchored CCL28 co-incorporated with influenza HA-antigens in chimeric virus-like particles (cVLPs), in boosting strong protective immune responses through an intranasal (i.n.) route in mice. We compared the immune responses to that from influenza VLPs without CCL28, or physically mixed with soluble CCL28 at systemic and various mucosal compartments. The cVLPs containing GPI-CCL28 showed in-vitro chemotactic activity towards spleen and lung cells expressing CCR3/CCR10 chemokine receptors. The cVLPs induced antigen specific endpoint titers and avidity indices of IgG in sera and IgA in tracheal, lung, and intestinal secretions, significantly higher (4-6 fold) than other formulations. Significantly higher (3-5 fold) hemagglutination inhibition titers and high serum neutralization against H3N2 viruses were also detected with CCL28-containing VLPs compared to other groups. The CCL28-containing VLPs showed complete and 80% protection, when vaccinated animals were challenged with A/Aichi/2/1968/H3N2 (homologous) and A/Philippines/2/1982/H3N2 (heterologous) viruses, respectively. Thus, GPI-anchored CCL28 in influenza VLPs act as a strong immunostimulator at both systemic and mucosal sites, boosting significant cross-protection in animals against heterologous viruses across a large distance.

Immune Defense in Upper Airways: A Single-Cell Study of Pathogen-Specific Plasmablasts and Their Migratory Potentials in Acute Sinusitis and Tonsillitis

Background

Despite the high frequency of upper respiratory tract (URT) infections and use of the nasal mucosa as route for vaccination, the local immune mechanism and dissemination of effector lymphocytes from the URT have been insufficiently characterized. To devise a single-cell approach for studying the mucosal immune response in the URT, we explored URT-originating B effector lymphocytes in the circulation of patients with one of two common respiratory infections, acute sinusitis or tonsillitis.

Methods

Patients with acute sinusitis (n = 13) or tonsillitis (n = 11) were investigated by ELISPOT for circulating pathogen-specific antibody-secreting cells (ASCs) of IgA, IgG and IgM isotypes approximately one week after the onset of symptoms. These cells’ potential to home into tissues was explored by assessing their expression of tissue-specific homing receptors α₄β₇, L-selectin, and cutaneous lymphocyte antigen (CLA).

Results

Pathogen-specific ASCs were detected in the circulation of all patients, with a geometric mean of 115 (95% CI 46–282) /10⁶ PBMC in sinusitis, and 48 (27–88) in tonsillitis. These responses were mainly dominated by IgG. In sinusitis α₄β₇ integrin was expressed by 24% of the ASCs, L-selectin by 82%, and CLA by 21%. The proportions for tonsillitis were 15%, 80%, and 23%, respectively. Healthy individuals had no ASCs.

Conclusions

URT infections–acute sinusitis and tonsillitis–both elicited a response of circulating pathogen-specific plasmablasts. The magnitude of the response was greater in sinusitis than tonsillitis, but the homing receptor profiles were similar. Human nasopharynx-associated lymphoid structures were found to disseminate immune effector cells with a distinct homing profile.

Human papillomavirus vaccination induces neutralising antibodies in oral mucosal fluids

Background:

Mucosal human papillomaviruses (HPV) are a major cause of cancers and papillomas of the anogenital and oropharyngeal tract. HPV-vaccination elicits neutralising antibodies in sera and cervicovaginal secretions and protects uninfected individuals from persistent anogenital infection and associated diseases caused by the vaccine-targeted HPV types. Whether immunisation can prevent oropharyngeal infection and diseases and whether neutralising antibodies represent the correlate of protection, is still unclear.

Methods:

We determined IgG and neutralising antibodies against low-risk HPV6 and high-risk HPV16/18 in sera and oral fluids from healthy females (n=20) before and after quadrivalent HPV-vaccination and compared the results with non-vaccinated controls.

Results:

HPV-vaccination induced type-specific antibodies in sera and oral fluids of the vaccinees. Importantly, the antibodies in oral fluids were capable of neutralising HPV pseudovirions in vitro, indicating protection from infection. The increased neutralising antibody levels against HPV16/18 in sera and oral fluids post-vaccination correlated significantly within an individual.

Conclusions:

We provide experimental proof that HPV-vaccination elicits neutralising antibodies to the vaccine-targeted types in oral fluids. Hence, immunisation may confer direct protection against type-specific HPV infection and associated diseases of the oropharyngeal tract. Measurement of antibodies in oral fluids represents a suitable tool to assess vaccine-induced protection within the mucosal milieu of the orophayrynx.

Biodegradable polymeric microsphere-based vaccines and their applications in infectious diseases

Vaccination, which provides effective, safe infectious disease protection, is among the most important recent public health and immunological achievements. However, infectious disease remains the leading cause of death in developing countries because several vaccines require repeated administrations and children are often incompletely immunized. Microsphere-based systems, providing controlled release delivery, can obviate the need for repeat immunizations. Here, we review the function of sustained and pulsatile release of biodegradable polymeric microspheres in parenteral and mucosal single-dose vaccine administration. We also review the active-targeting function of polymeric particles. With their shield and co-delivery functions, polymeric particles are applied to develop single-dose and mucosally administered vaccines as well as to improve subunit vaccines. Because polymeric particles are easily surface-modified, they have been recently used in vaccine development for cancers and many infectious diseases without effective vaccines (e.g., human immunodeficiency virus infection). These polymeric particle functions yield important vaccine carriers and multiple benefits.

New approaches to understanding the immune response to vaccination and infection

The immune system is a network of specialized cell types and tissues that communicates via cytokines and direct contact, to orchestrate specific types of defensive responses. Until recently, we could only study immune responses in a piecemeal, highly focused fashion, on major components like antibodies to the pathogen. But recent advances in technology and in our understanding of the many components of the system, innate and adaptive, have made possible a broader approach, where both the multiple responding cells and cytokines in the blood are measured. This systems immunology approach to a vaccine response or an infection gives us a more holistic picture of the different parts of the immune system that are mobilized and should allow us a much better understanding of the pathways and mechanisms of such responses, as well as to predict vaccine efficacy in different populations well in advance of efficacy studies. Here we summarize the different technologies and methods and discuss how they can inform us about the differences between diseases and vaccines, and how they can greatly accelerate vaccine development.

Connective Tissue Disease-related Thoracic Disease

Pulmonary involvement is a frequent manifestation of connective tissue disease (CTD)-related thoracic disease. It is important to characterize the underlying pattern when pulmonary involvement occurs in a patient with CTD, and to exclude other causes. A systematic approach, evaluating each compartment of the lung (airway, interstitium, pleura, pulmonary vasculature) may be helpful. In complex cases, a multidisciplinary approach should be considered, potentially including the pulmonologist, rheumatologist, radiologist, pathologist, and sometimes the infectious disease specialist or oncologist. New techniques, such as quantitative computed tomography and MRI, are expected to be helpful for evaluation and management of CTD-associated thoracic disease.

The mucosal immune system: From dentistry to vaccine development

The oral cavity is the beginning of the aero-digestive tract, which is covered by mucosal epithelium continuously under the threat of invasion of pathogens, it is thus protected by the mucosal immune system. In the early phase of our scientific efforts for the demonstration of mucosal immune system, dental science was one of major driving forces due to their foreseeability to use oral immunity for the control of oral diseases. The mucosal immune system is divided functionally into, but interconnected inductive and effector sites. Intestinal Peyer's patches (PPs) are an inductive site containing antigen-sampling M cells and immunocompetent cells required to initiate antigen-specific immune responses. At effector sites, PP-originated antigen-specific IgA B cells become plasma cells to produce polymeric IgA and form secretory IgA by binding to poly-Ig receptor expressed on epithelial cells for protective immunity. The development of new-generation mucosal vaccines, including the rice-based oral vaccine MucoRice, on the basis of the coordinated mucosal immune system is a promising strategy for the control of mucosal infectious diseases.

Hard, harder, hardest: principal stratification, statistical identifiability, and the inherent difficulty of finding surrogate endpoints

In many areas of clinical investigation there is great interest in identifying and validating surrogate endpoints, biomarkers that can be measured a relatively short time after a treatment has been administered and that can reliably predict the effect of treatment on the clinical outcome of interest. However, despite dramatic advances in the ability to measure biomarkers, the recent history of clinical research is littered with failed surrogates. In this paper, we present a statistical perspective on why identifying surrogate endpoints is so difficult. We view the problem from the framework of causal inference, with a particular focus on the technique of principal stratification (PS), an approach which is appealing because the resulting estimands are not biased by unmeasured confounding. In many settings, PS estimands are not statistically identifiable and their degree of non-identifiability can be thought of as representing the statistical difficulty of assessing the surrogate value of a biomarker. In this work, we examine the identifiability issue and present key simplifying assumptions and enhanced study designs that enable the partial or full identification of PS estimands. We also present example situations where these assumptions and designs may or may not be feasible, providing insight into the problem characteristics which make the statistical evaluation of surrogate endpoints so challenging.

Gut-Homing Conventional Plasmablasts and CD27(-) Plasmablasts Elicited after a Short Time of Exposure to an Oral Live-Attenuated Shigella Vaccine Candidate in Humans

Currently, there is no licensed Shigella vaccine; however, various promising live-attenuated vaccine candidates have emerged, including CVD1208S (ΔguaBA, Δset, Δsen S. flexneri 2a), which was shown to be safe and immunogenic in Phase 1 clinical trials. Here, we report the immune responses elicited in an outpatient Phase 2 clinical trial in which subjects were vaccinated with CVD 1208S. Oral immunization with CVD 1208S elicited high anti-S. flexneri 2a LPS and IpaB antibody responses as well as an acute plasmablast (PB) infiltration in peripheral blood 7 days after immunization. PB sorted based on their expression of homing molecules confirmed that cells expressing integrin α4β7 alone or in combination with CD62L were responsible for antibody production (as measured by ELISpot). Furthermore, using high-color flow-cytometry, on day 7 after immunization, we observed the appearance of conventional PB (CPB, CD19^dim CD20⁻ CD27^+high CD38^+high CD3⁻), as well as a PB population that did not express CD27 (CD27⁻ PB; pre-plasmablasts). The pattern of individual or simultaneous expression of homing markers (integrin α4β7, CD62L, CXCR3, and CXCR4) suggested that CPB cells homed preferentially to the inflamed gut mucosa. In contrast, ~50% CD27⁻ PB cells appear to home to yet to be identified peripheral lymphoid organs or were in a transition state preceding integrin α4β7 upregulation. In sum, these observations demonstrate that strong immune responses, including distinct PB subsets with the potential to home to the gut and other secondary lymphoid organs, can be elicited after a short time of exposure to a shigella oral vaccine.

Intranasal DNA Vaccine for Protection against Respiratory Infectious Diseases: The Delivery Perspectives

Intranasal delivery of DNA vaccines has become a popular research area recently. It offers some distinguished advantages over parenteral and other routes of vaccine administration. Nasal mucosa as site of vaccine administration can stimulate respiratory mucosal immunity by interacting with the nasopharyngeal-associated lymphoid tissues (NALT). Different kinds of DNA vaccines are investigated to provide protection against respiratory infectious diseases including tuberculosis, coronavirus, influenza and respiratory syncytial virus (RSV) etc. DNA vaccines have several attractive development potential, such as producing cross-protection towards different virus subtypes, enabling the possibility of mass manufacture in a relatively short time and a better safety profile. The biggest obstacle to DNA vaccines is low immunogenicity. One of the approaches to enhance the efficacy of DNA vaccine is to improve DNA delivery efficiency. This review provides insight on the development of intranasal DNA vaccine for respiratory infections, with special attention paid to the strategies to improve the delivery of DNA vaccines using non-viral delivery agents.

The lung may play a role in the pathogenesis of rheumatoid arthritis

Multiple studies have identified strong associations between the lung and rheumatoid arthritis (RA). Such studies identify a high prevalence of lung disease, both airways and parenchymal disease, in subjects with clinically classifiable RA. It has been suggested that lung disease in RA results from targeting of the lung from circulating autoimmunity or other factors such as medications. However, findings that lung disease, specifically inflammatory airways disease, and lung generation of autoimmunity can be present before the onset of joint symptoms suggest that immune reactions in the lung may be involved in the initial development of RA-related autoimmunity. Herein we review these issues in detail, as well as outline a potential research agenda to understand the natural history of lung involvement in RA and its relation to the overall pathogenesis of RA.