Opportunities and challenges to implementing mRNA-based vaccines and medicines: lessons from COVID-19.

The messenger RNA (mRNA) platform emerged at the forefront of vaccine development during the COVID-19 pandemic, with two mRNA COVID-19 vaccines being among the first authorized globally. These vaccines were developed rapidly. Informed by decades of laboratory research, and proved to be safe and efficacious tools for mitigating the global impact of the COVID-19 pandemic. The mRNA platform holds promise for a broader medical application beyond COVID-19. Herein, we provide an overview of this platform and describe lessons learned from the COVID-19 pandemic to help formulate strategies toward enhancing uptake of future mRNA-based interventions. We identify several strategies as vital for acceptance of an expanding array of mRNA-based vaccines and therapeutics, including education, accurate and transparent information sharing, targeted engagement campaigns, continued investment in vaccine safety surveillance, inclusion of diverse participant pools in clinical trials, and addressing deep-rooted inequalities in access to healthcare. We present findings from the Global Listening Project (GLP) initiative, which draws on quantitative and qualitative approaches to capture perceptions and experiences during the COVID-19 pandemic to help design concrete action plans for improving societal preparedness for future emergencies. The GLP survey (>70,000 respondents in 70 countries) revealed tremendous disparities across countries and sociodemographic groups regarding willingness to accept novel mRNA vaccines and medicines. The comfort in innovations in mRNA medicines was generally low (35%) and was marginally lower among women (33%). The GLP survey and lessons learnt from the COVID-19 pandemic provide actionable insights into designing effective strategies to enhance uptake of future mRNA-based medicines.

Immunoglobulin-specific responses to Chlamydia elementary bodies in individuals with and at risk for genital chlamydial infection.

Renewed interest in chlamydia vaccination has revealed the need for a greater understanding of the seroprevalence of chlamydial infection in US populations. We used a Chlamydia trachomatis elementary body (EB)-based enzyme-linked immunosorbent assay to define the characteristics of the humoral immune response and to determine seroprevalence. Two groups were analyzed: one consisting of patients with current, laboratory confirmed, genital chlamydial infection (n = 98) and one group of individuals whose chlamydia infection history was unknown (n = 367). C. trachomatis seropositivity was detected in 90% of the infected group and in 31% of the chlamydia-unknown group. IgG1 and IgG3 comprised the predominant anti-Chlamydia serum antibody responses. Serum IgA1 responses were variably positive, and individuals were rarely positive for anti-chlamydia IgG2, IgG4 or IgA2. The magnitude of the IgG1 and IgG3 responses was greatest in female and African American individuals and was sustained for at least 6 months. Antibody responses were not serovar restricted or confounded by Chlamydia pneumoniae cross-reactivity.

A systematic literature review and network meta-analysis feasibility study to assess the comparative efficacy and comparative effectiveness of pneumococcal conjugate vaccines.

Background: No head-to-head studies are currently available comparing pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) with 13-valent pneumococcal conjugate vaccine (PCV-13). This study explored the feasibility of using network meta-analysis (NMA) to conduct an indirect comparison of the relative efficacy or effectiveness of the two vaccines.Methods: A systematic literature search was conducted for published randomized controlled trials (RCTs) and non-RCT studies reporting data on vaccine efficacy or effectiveness against invasive pneumococcal disease in children aged <5 years receiving 7-valent pneumococcal conjugate vaccine (PCV-7), PHiD-CV or PCV-13. Study quality was evaluated using published scales. NMA feasibility was assessed by considering whether a connected network could be constructed by examining published studies for differences in study or patient characteristics that could act as potential treatment effect modifiers or confounding variables.Results: A total of 26 publications were included; 2 RCTs (4 publications), 7 indirect cohort studies, and 14 case-control studies (15 publications). Study quality was generally good. The RCTs could not be connected in a network as there was no common comparator. The studies differed considerably in design, dose number, administration schedules, and subgroups analyzed. Reporting of exposure status and subject characteristics was inconsistent.Conclusion: NMA to compare the relative efficacy or effectiveness of PHiD-CV and PCV-13 is not feasible on the current evidence base, due to the absence of a connected network across the two RCTs and major heterogeneity between studies. NMA may be possible in future if sufficient RCTs become available to construct a connected network.

IL-4 primes human endothelial cells for secondary responses to histamine.

Interleukin-4 (IL-4) is a multifunctional cytokine, which is involved in numerous disease states, including atopic asthma. IL-4 not only induces direct responses in cells but can also prime for secondary responses to stimuli. Little is known about the priming effects of IL-4 on endothelial cells; therefore, we chose to examine the ability of IL-4 to prime endothelial cells for platelet-activating factor (PAF) synthesis and prostaglandin E(2) (PGE(2)) release. IL-4 alone did not enhance PAF synthesis or PGE(2) release; however, pretreatment with IL-4 primed for PAF synthesis and PGE(2) release in response to subsequent stimulation with histamine. In contrast, tumor necrosis factor alpha (TNF-alpha), oncostatin M (OSM), and IL-1beta did not prime endothelial cells for PAF synthesis in response to histamine. The priming effects of IL-4 occurred without any detectable changes in the requirement for signaling pathways upstream of PGE(2) release. IL-4 treatment increased the expression of mRNA for histamine receptor 1 (HR1) and shifted the inhibition curve for pyrilamine, a specific HR1 antagonist. In addition, the dose-response curve for histamine-induced elevations in intracellular calcium was shifted following IL-4 stimulation. Together, these data indicate that HR1 is up-regulated in IL-4-stimulated human umbilical vein endothelial cells (HUVEC) and suggest that this up-regulation may contribute to the enhanced responsiveness of IL-4-stimulated HUVEC to histamine.

Design and preclinical characterization of a novel vaccine adjuvant formulation consisting of a synthetic TLR4 agonist in a thermoreversible squalene emulsion.

We describe the development, analytical characterization, stability and preclinical efficacy of AF04, a combination adjuvant comprising the synthetic toll-like receptor 4 (TLR4) agonist, E6020, formulated in AF03, a thermoreversible squalene emulsion. By using AF04 with the recombinant major outer membrane protein of Chlamydia trachomatis (Ct-MOMP) and with the recombinant surface glycoprotein gB from human cytomegalovirus (CMV-gB) as model antigens, we show that AF03 and E6020 can synergize to augment specific antibody and Th-1 cellular immune responses in mice. In terms of formulation, we observe that the method used to incorporate E6020 into AF03 affects its partition between the oil and water phases of the emulsion which in turn has a significant impact on the tolerability (IV pyrogenicity test in rabbits) of this novel adjuvant combination.

Elevated elafin/trappin-2 in the female genital tract is associated with protection against HIV acquisition.

OBJECTIVES: Globally, heterosexual intercourse is the primary route of HIV-1 (HIV) transmission. It follows that mechanisms that protect against HIV infection are likely operative at the genital mucosa. In HIV-resistant Kenyan sex workers who are highly exposed to HIV infection yet remain uninfected, protection correlates with HIV-specific immune responses and genetic factors. However, these factors do not entirely explain this model of natural immunity to HIV. We hypothesized that protection may be mediated by innate immune proteins in the genital tract of HIV-resistant sex workers. DESIGN AND METHODS: The genital proteome of mucosal secretions from HIV-resistant women was examined using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. Cervical lavage samples were collected from 315 HIV-resistant, HIV-uninfected and HIV-infected commercial sex workers. RESULTS: Univariate analysis identified a 6 kDa biomarker of HIV resistance in genital secretions from these women. This protein was identified by tandem mass spectrometry as elafin and was found to be overexpressed in HIV-resistant women compared with HIV-uninfected (P = 0.001) and infected (P = 0.002) women. The elevated levels of elafin/trappin-2 in HIV-resistant women were confirmed using ELISA. The prospective association of elevated cervicovaginal elafin/trappin-2 levels with protection from HIV acquisition was then confirmed in an independent cohort of high-risk female sex workers. CONCLUSION: Using a unique proteomics approach in a large scale, cross-sectional cohort study, we identified elafin/trappin-2 as a novel innate immune factor, which is highly associated with resistance. This association was confirmed within an independent, prospective cohort study. Genital tract elafin/trappin-2 levels constitute a natural correlate of HIV protection in humans.

Mucosal innate immunity as a determinant of HIV susceptibility.

Most human immunodeficiency virus (HIV) is acquired during sex, across a mucosal membrane. Despite many advances in our understanding of HIV pathogenesis, the initial events during mucosal transmission have been poorly characterized, and a better understanding of these events will probably be a key to the development of successful microbicide(s) and/or a preventative HIV vaccine. While a vast majority of mucosal HIV exposures do not result in productive infection, implying that innate mucosal immune defenses are highly protective, failure of these mucosal defenses resulted in over 3 million new HIV infections in 2006. We review recent findings regarding HIV mucosal immunopathogenesis, emphasizing the importance of innate immunity in natural protection from infection, and examine how natural or induced perturbations in the mucosal innate system may underpin HIV transmission. Given the great challenges to the development of HIV microbicides and vaccines, identification and enhancement of 'natural' innate immune defenses present attractive avenues for development of safe, non-toxic microbicides.

Elevated T cell counts and RANTES expression in the genital mucosa of HIV-1-resistant Kenyan commercial sex workers.

The initial site of exposure to human immunodeficiency virus (HIV)-1 during heterosexual transmission occurs in the genital tract. Although the majority of immunological studies have focused on the immune response to HIV-1 at the systemic level, our understanding of tissue-specific immunity is deficient. The goal of the present study was to characterize T cell populations found in the cervix of women shown to be resistant to infection by HIV-1. Levels of both systemic and cervical mucosal lymphocytes were compared between HIV-1-resistant, HIV-1-uninfected, and HIV-1-infected commercial sex workers (CSWs) as well as HIV-1-uninfected non-CSW control subjects at low risk for exposure. The HIV-1-resistant CSWs had increased cervical CD4+ and CD8+ T cell counts, compared with the HIV-1-uninfected CSWs; importantly, these increases were not reflected in the systemic lymphocyte compartment. There was a 2-fold increase in CD4+ T cell counts in the HIV-1-resistant CSWs, compared with both the HIV-1-infected and the HIV-1-uninfected CSWs. Expression of the HIV-1 coreceptors CCR5 and CXCR4 was also determined, and cytokine and beta chemokine levels in the genital mucosa were assessed. The HIV-1-resistant CSWs had a 10-fold increase in RANTES expression, compared with the HIV-1-uninfected CSWs. This is the first study to show elevated levels of beta chemokines and CD4+ T cells in the genital tracts of women who are exposed to HIV-1 and yet are uninfected.