Immunologic studies of specific mucosal and systemic immune responses in Mexican school children after booster aerosol or subcutaneous immunization with measles vaccine

Inhaled vaccine delivery in the combat against respiratory viruses: a 2021 overview of recent developments and implications for COVID-19

INTRODUCTION

As underlined by the late 2019 outbreak of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), vaccination remains the cornerstone of global health-care. Although vaccines for SARS-CoV-2 are being developed at a record-breaking pace, the majority of those that are licensed or currently registered in clinical trials are formulated as an injectable product, requiring a tightly regulated cold-chain infrastructure, and primarily inducing systemic immune responses.

AREAS COVERED

Here, we shed light on the status of inhaled vaccines against viral pathogens, providing background to the role of the mucosal immune system and elucidating what factors determine an inhalable vaccine's efficacy. We also discuss whether the development of an inhalable powder vaccine formulation against SARS-CoV-2 could be feasible. The review was conducted using relevant studies from PubMed, Web of Science and Google Scholar.

EXPERT OPINION

We believe that the scope of vaccine research should be broadened toward inhalable dry powder formulations since dry vaccines bear several advantages. Firstly, their dry state can tremendously increase vaccine stability and shelf-life. Secondly, they can be inhaled using disposable inhalers, omitting the need for trained health-care personnel and, therefore, facilitating mass-vaccination campaigns. Thirdly, inhalable vaccines may provide improved protection since they can induce an IgA-mediated mucosal immune response.

Nanogel-based nasal vaccines for infectious and lifestyle-related diseases

Because the mucosa is the major entry route for most pathogens, the development of mucosal vaccines is a rational approach for protecting against these undesired agents. Mucosal administration of vaccine antigen is useful for non-infectious chronic diseases as well, because of its advantages over injection routes, including comparable efficacy in the induction of systemic immune responses, less pain, and no risk of adverse events at the injection site. However, because it is difficult to effectively induce and regulate antigen-specific mucosal and systemic immune responses when antigen alone is mucosally administered, an appropriate form of mucosal delivery vehicle must be used. Antigen delivery systems involving nanogels, which act as artificial chaperones and mucosal adhesives, are a promising approach to overcoming this problem. Here, we introduce current perspectives regarding the development of nanogel-based nasal vaccines for both infectious and lifestyle-related diseases.

Needle-free delivery of measles virus vaccine to the lower respiratory tract of non-human primates elicits optimal immunity and protection

Needle-free measles virus vaccination by aerosol inhalation has many potential benefits. The current standard route of vaccination is subcutaneous injection, whereas measles virus is an airborne pathogen. However, the target cells that support replication of live-attenuated measles virus vaccines in the respiratory tract are largely unknown. The aims of this study were to assess the in vivo tropism of live-attenuated measles virus and determine whether respiratory measles virus vaccination should target the upper or lower respiratory tract. Four groups of twelve cynomolgus macaques were immunized with 10⁴ TCID₅₀ of recombinant measles virus vaccine strain Edmonston-Zagreb expressing enhanced green fluorescent protein. The vaccine virus was grown in MRC-5 cells and formulated with identical stabilizers and excipients as used in the commercial MV^EZ vaccine produced by the Serum Institute of India. Animals were immunized by hypodermic injection, intra-tracheal inoculation, intra-nasal instillation, or aerosol inhalation. In each group six animals were euthanized at early time points post-vaccination, whereas the other six were followed for 14 months to assess immunogenicity and protection from challenge infection with wild-type measles virus. At early time-points, enhanced green fluorescent protein-positive measles virus-infected cells were detected locally in the muscle, nasal tissues, lungs, and draining lymph nodes. Systemic vaccine virus replication and viremia were virtually absent. Infected macrophages, dendritic cells and tissue-resident lymphocytes predominated. Exclusive delivery of vaccine virus to the lower respiratory tract resulted in highest immunogenicity and protection. This study sheds light on the tropism of a live-attenuated measles virus vaccine and identifies the alveolar spaces as the optimal site for respiratory delivery of measles virus vaccine.

Protection from SARS coronavirus conferred by live measles vaccine expressing the spike glycoprotein

The recent identification of a novel human coronavirus responsible of a SARS-like illness in the Middle-East a decade after the SARS pandemic, demonstrates that reemergence of a SARS-like coronavirus from an animal reservoir remains a credible threat. Because SARS is contracted by aerosolized contamination of the respiratory tract, a vaccine inducing mucosal long-term protection would be an asset to control new epidemics. To this aim, we generated live attenuated recombinant measles vaccine (MV) candidates expressing either the membrane-anchored SARS-CoV spike (S) protein or its secreted soluble ectodomain (Ssol). In mice susceptible to measles virus, recombinant MV expressing the anchored full-length S induced the highest titers of neutralizing antibodies and fully protected immunized animals from intranasal infectious challenge with SARS-CoV. As compared to immunization with adjuvanted recombinant Ssol protein, recombinant MV induced stronger and Th1-biased responses, a hallmark of live attenuated viruses and a highly desirable feature for an antiviral vaccine.

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Generation of live recombinant measles vaccine expressing SARS-CoV spike protein.

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Induction of high titers anti-SARS-CoV neutralizing antibodies in mice.

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Protection of immunized mice from intranasal infectious challenge with SARS-CoV.

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Induction of Th1-biased responses and IgA.

Development of protective anti-Mycoplasma pneumoniae antibodies after immunization of guinea pigs with the combination of a P1-P30 chimeric recombinant protein and chitosan

The attachment organelle of the human respiratory tract pathogen Mycoplasma pneumoniae is essential for colonization of the host mucosa. Furthermore, adherence-related proteins such as the major adhesin P1 and protein P30 represent vaccine candidates. Using the chimeric recombinant protein HP14/30, which combines surface-localized and adherence-involved regions of both proteins, we developed an optimized strategy to immunize guinea pigs. The vaccination protocol includes subcutaneous prime immunization followed by presentation of the antigen directly to the respiratory mucosa by two intranasal (i.n.) administrations and combination of antigen with the mucosal adjuvant chitosan. The immunization scheme induced high, consistent and long-lasting IgA levels in respiratory tract samples (BAL, nasal and throat washing fluid) from the animals. In comparison with a preimmune serum, incubation of M. pneumoniae cells with sera from these animals reduced the mean adhesion of bacteria to HeLa cells to 6%. After i.n. infection, immunized animals showed significantly decreased numbers of M. pneumoniae-specific genome copies, especially in the upper respiratory tract, in comparison with the control group. The results demonstrated that optimized immunization with the chimeric protein HP14/30 is promising for further vaccination efforts to prevent host colonization with M. pneumoniae.

The status of live viral vaccination in early life

The need for neonatal vaccines is supported by the high disease burden during the first year of life particularly in the first month. Two-thirds of childhood deaths are attributable to infectious diseases of which viruses represent key pathogens. Many infectious diseases have the highest incidence, severity and mortality in the first months of life, and therefore early life vaccination would provide significant protection and life savings. For some childhood viral diseases successful vaccines exist, such as against measles, mumps, rubella, varicella, influenza poliovirus, and rotavirus, but their use in the first year particularly at birth is not yet practiced. Vaccines against other key pathogens continue to elude scientists such as against respiratory syncytial virus. The obstacles for early and neonatal vaccination are complex and include host factors, such as a developing immune system and the interference of passively acquired antibodies, as well vaccine-specific issues, such as optimal route of administration, titer and dosing requirements. Importantly, additional host and infrastructure barriers also present obstacles to neonatal vaccination in the developing world where morbidity and mortality rates are highest. This review will highlight the current live viral vaccines and their use in the first year of life, focusing on efficacy and entertaining the barriers that exist. It is important to understand the successes of current vaccines and use this knowledge to determine strategies that are successful in young infants and for the development of new vaccines for use in early life.

Aerosolized MMR vaccine: evaluating potential transmission of components to vaccine administrators and contacts of vaccinees

Although numerous operative and immunological advantages accompany aerosol immunization, potential vaccine virus transmission from the aerosol device to vaccine administrators or from aerosol vaccinees to their contacts requires further study. We conducted a clinical and serological follow-up study of vaccine administrators and matched classroom or household contacts of young adults who received the MMR vaccines by aerosol or injection. Differences in incidence of clinical adverse events between vaccinees and contacts were not statistically significant. No seroresponses to any components of MMR vaccine were noted among 25 matched contacts of persons receiving injected vaccines, and only one equivocal seroresponse was noted among 25 matched contacts of aerosol recipients. No seroresponses were observed in 3 persons who administered aerosol vaccine. The composite findings of this study provide additional evidence of the safety of this approach.

New insights in mucosal vaccine development

Mucosal surfaces are the major entrance for infectious pathogens and therefore mucosal immune responses serve as a first line of defence. Most current immunization procedures are obtained by parenteral injection and only few vaccines are administered by mucosal route, because of its low efficiency. However, targeting of mucosal compartments to induce protective immunity at both mucosal sites and systemic level represents a great challenge. Major efforts are made to develop new mucosal candidate vaccines by selecting appropriate antigens with high immunogenicity, designing new mucosal routes of administration and selecting immune-stimulatory adjuvant molecules. The aim of mucosal vaccines is to induce broad potent protective immunity by specific neutralizing antibodies at mucosal surfaces and by induction of cellular immunity. Moreover, an efficient mucosal vaccine would make immunization procedures easier and be better suited for mass administration. This review focuses on contemporary developments of mucosal vaccination approaches using different routes of administration.

An evaluation of respiratory administration of measles vaccine for prevention of acute lower respiratory infections in children

Background

Measles was responsible for an estimated 100,000 deaths worldwide in 2008. Despite being a vaccine-preventable disease, measles remains a major cause of morbidity and mortality in young children. Although a safe and effective injectable measles vaccine has been available for over 50 years it has not been possible to achieve the uniformly high levels of coverage (required to achieve measles eradication) in most parts of the developing world. Aerosolised measles vaccines are now under development with the hope of challenging the delivery factors currently limiting the coverage of the existing vaccine.

Methods

We used a modified CHNRI methodology for setting priorities in health research investments to assess the strengths and weaknesses of this emerging intervention to decrease the burden of childhood pneumonia. This was done in two stages. In Stage I, we systematically reviewed the literature related to emerging aerosol vaccines against measles relevant to several criteria of interest. Although there are a number of different aerosol vaccine approaches under development, for the purpose of this exercise, all were considered as one intervention. The criteria of interest were: answerability; cost of development, production and implementation; efficacy and effectiveness; deliverability, affordability and sustainability; maximum potential impact on disease burden reduction; acceptability to the end users and health workers; and effect on equity. In Stage II, we conducted an expert opinion exercise by inviting 20 experts (leading basic scientists, international public health researchers, international policy makers and representatives of pharmaceutical companies). The policy makers and industry representatives accepted our invitation on the condition of anonymity, due to the sensitive nature of their involvement in such exercises. They answered questions from the CHNRI framework and their “collective optimism” towards each criterion was documented on a scale from 0 to 100%.

Results

The panel of experts expressed mixed feelings about an aerosol measles vaccine. The group expressed low levels of optimism regarding the criteria of likelihood of efficacy and low cost of development (scores around 50%); moderate levels of optimism regarding answerability, low cost of production, low cost of implementation and affordability (score around 60%); and high levels of optimism regarding deliverability, impact on equity and acceptability to health workers and end-users (scores over 80%). Finally, the experts felt that this intervention will have a modest but nevertheless important impact on reduction of burden of disease due to childhood pneumonia (median: 5%, interquartile range 1-15%, minimum 0%, maximum 45%).

Conclusion

Aerosol measles vaccine is at an advanced stage of development, with evidence of good immunogenicity. This new intervention will be presented as a feasible candidate strategy in the campaign for global elimination of measles. It also presents an unique opportunity to decrease the overall burden of disease due to severe pneumonia in young children.

Mucosal IgA responses in healthy adult volunteers following intranasal spray delivery of a live attenuated measles vaccine

Measles remains an important cause of morbidity and mortality among children in the developing world. The goal of this study was to examine measles virus-specific mucosal immune responses in healthy immune (n = 24; plaque reduction neutralization [PRN] titers of ≥200 mIU/ml) and nonimmune (n = 24) young adult volunteers who received the monovalent Moraten measles vaccine via intranasal (spray delivery) or subcutaneous immunization. Serum, oral fluid, and nasal wash samples were examined for measles virus-specific and total IgG and IgA on day 0 (prior to vaccination) and on days 14, 28, and 90 after vaccination. Nonimmune subjects vaccinated subcutaneously developed high levels of measles virus PRN, IgG, and IgA antibodies in serum, oral fluid, and nasal washes. Total IgG and secretory IgA (sIgA) titers were increased in nasal washes, and total IgG was increased in oral fluid specimens. There was a strong correlation between PRN and measles virus-specific IgG titers measured in serum, oral fluid, and nasal washes, whereas a weak correlation was found between PRN and measles virus-specific IgA titers. Notably, intranasal measles vaccination resulted in increased production of measles virus-specific sIgA in oral fluid and nasal washes in nonimmune individuals, without evidence of a systemic immune response. In contrast, no significant vaccine-induced responses were observed in immune subjects, regardless of the route of immunization. These results demonstrate that (i) intranasal measles immunization can elicit a mucosal response independent of the induction of serum antibodies and (ii) both mucosal and systemic antibody responses following nasal or subcutaneous immunization are blunted by preexisting measles immunity.

Successful seroresponses to measles and rubella following aerosolized Triviraten vaccine, but poor response to aerosolized mumps (Rubini) component: comparisons with injected MMR

Seroresponses to measles, rubella and mumps were evaluated following the injection of MMR II and injection or aerosol administration of Triviraten in young adults. Response to aerosolized Rubini mumps strain was a focus of interest, given robust responses to aerosolized mumps vaccine (Leningrad-Zagreb strain) in a prior study using aerosolized MMR vaccine. The aerosolized Edmonston-Zagreb (EZ) measles vaccine was significantly more immunogenic than injected EZ vaccine, and comparable to results following injected Moraten measles vaccine having twice the dosage. Responses to rubella were comparable in the three MMR study groups. Aerosolized Rubini vaccine was very highly and unexpectedly less immunogenic than either injected Rubini or Jeryl-Lyn strains. The high attenuation of Rubini vaccine appears to have limited its affinity for respiratory tract receptors, which may underlie its lack of clinical effectiveness.

Measles vaccination: new strategies and formulations

Measles is a highly contagious viral disease. With 1 million deaths reported in 1996, measles was the leading cause of vaccine-preventable deaths. However, in recent years, significant progress has been made in measles control, reducing deaths attributed to measles to 454,000 in 2004 and 242,000 in 2006. The main strategy behind this reduction has been the improvement of vaccination coverage and implementation of a second opportunity for immunization with the live-attenuated measles vaccine. The Measles Initiative, a partnership between the American Red Cross, CDC, UNICEF, WHO and UN Foundation, has had a significant role in this achievement. Here, we provide an overview of old and new vaccination strategies, and discuss changes in the route of administration of the existing live-attenuated vaccine, the development of new-generation nonreplicating measles virus vaccine candidates and attempts to use recombinant measles virus as a vector for vaccination against other pathogens.

The delivery site of a monovalent influenza vaccine within the respiratory tract impacts on the immune response

Pulmonary vaccination is a promising immunization route. However, there still remains a crucial need to characterize the different parameters affecting the efficacy of inhaled vaccination. This study aimed at assessing the impact of antigen distribution within the respiratory tract on the immune response to a monovalent A/Panama/2007/99 H3N2 influenza split virus vaccine administered to BALB/c mice. Varying the administration technique allowed the targeting of the vaccine to different sites of the mouse respiratory tract, i.e. the nasal cavity, the upper or central airways, or the deep lung. This targeting was verified by using ovalbumin as a tracer compound. The immune responses generated following influenza vaccine administration to the different respiratory tract sites were compared to each other and to those elicited by intramuscular and peroral intragastric immunization. Delivery of the vaccine to the different respiratory regions generated systemic, local and cellular virus-specific immune responses, which increased with the depth of vaccine deposition, culminating in deep-lung vaccination. The latter induced virus-specific serum immunoglobulin G and neutralizing antibody titres as elevated as intramuscular vaccination, whereas the production of mucosal secretory immunoglobulin A was significantly superior in deep-lung-vaccinated animals. The analysis of cytokines secreted by mononuclear cells during an in vitro recall response indicated that deep-lung vaccination induced a local shift of the cellular immune response towards a T helper type 1 phenotype as compared to intramuscular vaccination. In conclusion, antigen distribution within the respiratory tract has a major effect on the immune response, with the deep lung as the best target for inhaled influenza vaccination.

Measles aerosol vaccination

Measles ranks fifth among the five major childhood conditions which are responsible for 21% of all deaths in low and middle-income countries. Measles immunization is considered the most cost-effective public health intervention in the world. In recent years, there has been a critical need to identify alternative routes of measles immunization, which are rapid, reliable, cost-effective, needle-free, and suitable for use in mass campaigns. Aerosol administration of measles vaccines in mass campaigns was first proposed by Dr. Albert Sabin. We review the different clinical trials that have been conducted using the classic Mexican device as well as issues regarding vaccine strain, presentation, and manufacturer. Results of clinical trials indicate that the method is safe and immunogenic in infants and school age children. The viral inoculum will probably need to be increased when administered to infants. From the logistical point of view, the use of the aerosol method has not been evaluated in routine immunization although feasibility of its routine implementation was proved in mass campaigns in Mexico. Cost savings will probably be demonstrated. As to licensure, its compliance with the appropriate international regulatory requirements for medical aerosol delivery devices is in process.

Measles vaccination of macaques by dry powder inhalation

Measles vaccination via the aerosol route has proven effective under field conditions, using vaccine reconstituted prior to nebulization. Inhalation of a dry powder aerosol vaccine would have additional benefits, including easier logistics of administration, reduced cold chain dependence and the potential of single dose administration. We have evaluated two candidate dry powder measles vaccine formulations in macaques. Specific immune responses were demonstrated, but levels of immunity were lower than in animals vaccinated by injection or by nebulized aerosol. These studies provide proof of principle that dry powder inhalation is a possible route for measles vaccination, but suggest that either the vaccine formulation or the method of delivery need to be improved for a better immune response.

Aerosol measles vaccination in macaques: preclinical studies of immune responses and safety

The comparative efficacy and safety of measles vaccination via the aerosol route versus subcutaneous injection has not been fully resolved. We vaccinated cynomolgus monkeys (Macaca fascicularis) with the live-attenuated Edmonston-Zagreb measles virus (MV) vaccine and compared different routes of administration in the immunocompetent and the immunocompromised host. Immunogenicity and protective efficacy of aerosol vaccination using devices similar to those previously used in humans were comparable to those in animals vaccinated by injection. No evidence for a safety hazard associated with the route of vaccination was detected. The results of this study support further clinical evaluation of aerosol vaccination for measles.

Robust HIV-specific immune responses were induced by DNA vaccine prime followed by attenuated recombinant vaccinia virus (LC16m8 strain) boost

Recombinant vaccinia virus-based vaccine combined with DNA vaccine has produced a protective immune response against HIV infection in non-human primates. In this study, we explored the immunogenicity of a recombinant vaccinia virus (LC16m8 strain), which has been used in children without severe side effects. The vaccinia virus expressing an HIV(89.6)env gene (vLC-Env) alone or combined with a DNA vaccine expressing the HIV(89.6)env gene (pCAG-Env) was characterized in BALB/c mice. Vaccination of vLC-Env induced much higher HIV-specific humoral and cell-mediated immune responses than that of pCAG-Env. Priming with pCAG-Env further enhanced vLC-Env induced immune responses, especially cell-mediated immune response. Moreover, efficient expression of Env protein was achieved following infection of bone marrow dendritic cells by vLC-Env in vitro. Administration of vLC-Env-infected dendritic cells to mice generated a high cell-mediated immune response. These results demonstrate that priming with pCAG-Env and boosting with vLC-Env represents a logical candidate for vaccination against HIV infection.

Improved intranasal immunization with live-attenuated measles virus after co-inoculation of the lipopeptide MALP-2

The macrophage-activating lipopeptide with a molecular weight of 2kDa (MALP-2) activates antigen presenting cells of human, mouse and rat origin in vitro and in vivo. Here, we demonstrate that MALP-2 induces MIP1alpha and beta, MIP-2, Gro, TNFalpha, IL1alpha and IL6 in cells of cotton rats (Sigmodon hispidus) in vitro. Intranasal inoculation into cotton rats leads to migration of neutrophils and other leucocytes into the lung lumen and lung tissue. After intranasal co-inoculation of MALP-2 with live-attenuated measles vaccine virus, higher titers of neutralizing antibodies are induced but the proliferative T cell response did not increase. Immunization leads to protective immunity in the absence, but not in the presence of passively transferred measles virus (MV) specific antibodies.

Measles

PURPOSE OF REVIEW

The purpose of this review is to summarize important papers concerning measles disease and measles-containing vaccines published in 2004.

RECENT FINDINGS

Endemic measles has been successfully controlled in the Americas and, to a lesser extent, in Europe. This has been achieved with a high uptake of two doses of a measles-containing vaccine. Even in industrialized countries, where vaccine uptake is poor, for example Japan, the disease is still a significant cause of morbidity and mortality. Vaccine failure is predominantly due to primary vaccine failure, which may, in part, be genetic in origin and related to HLA type. Measles-containing vaccines have been shown to be associated with febrile convulsions, but there is no strong evidence of a link with atopy. There is considerable evidence that there is no causal relationship with autistic disorders. In spite of this, many parents and some professionals have concerns about the safety of the vaccines, which may lead to their underuse.

SUMMARY

It is possible to eliminate measles with a high uptake of two doses of measles-containing vaccine, but concerns about safety persist and need to be tackled. More research is required into how to do this effectively and also to elucidate the causes of vaccine failure.

The development of a plant-based vaccine for measles

Plant-based vaccination strategies have the potential to overcome the limitations of the current measles vaccine. The measles virus hemagglutinin (MV-H) protein has been expressed in tobacco. Oral immunisation of mice with plant-derived MV-H protein resulted in MV-specific antibodies and secretory IgA, indicative of humoral and mucosal immune responses. In addition, boosting with oral plant-derived MV-H protein following a MV-H DNA prime, resulted in a greater response than could be induced with either vaccine alone. Collectively, this research represents a significant step towards an effective oral measles vaccine that would be temperature-stable, easy to administer and amenable to inexpensive manufacture.

Gastrointestinal immunopathology and food allergy

OBJECTIVE

To review the current data that support the pivotal function of the gastrointestinal immune system in health and disease and its critical role in the pathogenesis of a wide variety of clinical disorders associated with food allergy (FA).

DATA SOURCES

Internet-based literature search and our own data.

STUDY SELECTION

The studies included in this review were selected based on the expert opinion of the authors.

RESULTS

In contrast to the beneficial expressions of gastrointestinal-associated lymphoid tissue, which are seen with relevance to newer methods of delivery of vaccines directly applied to the gastrointestinal mucosal surfaces (eg, oral poliovirus, rotavirus, Salmonella typhi vaccines), the adverse consequences of a mucosal immune response gone astray are evidenced in many diseases such as FA. A classification of clinical disorders associated with FA based on classic mechanisms of immunologic injury is presented, which includes the following: (1) IgE-mediated, (2) non-IgE-mediated, and (3) mixed IgE- and non-IgE-mediated disorders. Our study of immunologic disturbance in patients with non-IgE FA revealed a pattern of increased CD4+ and decreased TH1 cell counts in peripheral blood mononuclear cells in contrast to patients with celiac disease, where a pattern of increased CD8+ and TH1 cell counts in peripheral blood mononuclear cells and increased CD8+ cell counts was seen.

CONCLUSIONS

The gastrointestinal immune response thus plays a pivotal role in maintaining protective immunity in health and a critical role in the pathogenesis of a wide variety of clinical disorders associated with FA.