Youth Mental Health Outcomes up to Two Years After SARS-CoV-2 Infection Long-COVID or Long-Pandemic Syndrome: A Retrospective Cohort Study

PURPOSE

Youth mental distress has substantially increased during the COVID-19 pandemic. However, it is unclear if mental symptoms are directly related to SARS-CoV-2 infection or to social restrictions. We aimed to investigate mental health outcomes in infected versus uninfected adolescents, for up to two years after an index polymerase chain reaction (PCR) test.

METHODS

A retrospective cohort study, based on electronic health records from a large nationally representative Israeli health fund, among adolescents aged 12-17 years with a PCR test for SARS-CoV-2 between March 1, 2020 and March 1, 2021. Infected and uninfected individuals were matched by age, sex, test date, sector, and socioeconomic status. Cox regression was used to derive hazard ratios (HRs) for mental health outcomes within two years from PCR test for infected versus uninfected individuals, while accounting for pre-existing psychiatric history. External validation was performed on UK primary care data.

RESULTS

Among 146,067 PCR-tested adolescents, 24,009 were positive and 22,354 were matched with negative adolescents. SARS-CoV-2 infection was significantly associated with reduced risks for dispensation of antidepressants (HR 0.74, 95% confidence interval [CI] 0.66-0.83), diagnoses of anxiety (HR 0.82, 95% CI 0.71-0.95), depression (HR 0.65, 95% CI 0.53-0.80), and stress (HR 0.80, 95% CI 0.69-0.92). Similar results were obtained in the validation dataset.

DISCUSSION

This large, population-based study suggests that SARS-CoV-2 infection is not associated with elevated risk for mental distress in adolescents. Our findings highlight the importance of taking a holistic view on adolescents' mental health during the pandemic, with consideration of both SARS-CoV-2 infection and response measures.

Data-Driven Assessment of Adolescents' Mental Health During the COVID-19 Pandemic

OBJECTIVE

Adolescents' mental health was severely compromised during the COVID-19 pandemic. Longitudinal real-world studies on changes in the mental health of adolescents during the later phase of the pandemic are limited. We aimed to quantify the effect of COVID-19 pandemic on adolescents' mental health outcomes based on electronic health records.

METHOD

This was a retrospective cohort study using the computerized database of a 2.5 million members, state-mandated health organization in Israel. Rates of mental health diagnoses and psychiatric drug dispensations were measured among adolescents 12 to 17 years of age with and without pre-existing mental history, for the years 2017 to 2021. Relative risks were computed between the years, and interrupted time series (ITS) analyses evaluated changes in monthly incidence rates of psychiatric outcomes.

RESULTS

The average population size was 218,146 in 2021. During the COVID-19 period, a 36% increase was observed in the incidence of depression (95% CI = 25-47), 31% in anxiety (95% CI = 23-39), 20% in stress (95% CI = 13-27), 50% in eating disorders (95% CI = 35-67), 25% in antidepressant use (95% CI = 25-33), and 28% in antipsychotic use (95% CI = 18-40). A decreased rate of 26% (95% CI = 0.80-0.88) was observed in ADHD diagnoses. The increase of the examined outcomes was most prominent among youth without psychiatric history, female youth, general secular Jewish population, youth with medium-high socioeconomic status, and those 14 to 15 years of age. ITS analysis confirmed a significantly higher growth in the incidence of psychiatric outcomes during the COVID-19 period, compared to those in previous years.

CONCLUSION

This real-world study highlights the deterioration of adolescents' mental health during the COVID-19 pandemic and suggests that youth mental health should be considered during health policy decision making.

DIVERSITY & INCLUSION STATEMENT

We worked to ensure sex and gender balance in the recruitment of human participants. We worked to ensure race, ethnic, and/or other types of diversity in the recruitment of human participants. We actively worked to promote sex and gender balance in our author group. The author list of this paper includes contributors from the location and/or community where the research was conducted who participated in the data collection, design, analysis, and/or interpretation of the work.

Long covid outcomes at one year after mild SARS-CoV-2 infection: nationwide cohort study

OBJECTIVES

To determine the clinical sequelae of long covid for a year after infection in patients with mild disease and to evaluate its association with age, sex, SARS-CoV-2 variants, and vaccination status.

DESIGN

Retrospective nationwide cohort study.

SETTING

Electronic medical records from an Israeli nationwide healthcare organisation.

POPULATION

1 913 234 Maccabi Healthcare Services members of all ages who did a polymerase chain reaction test for SARS-CoV-2 between 1 March 2020 and 1 October 2021.

MAIN OUTCOME MEASURES

Risk of an evidence based list of 70 reported long covid outcomes in unvaccinated patients infected with SARS-CoV-2 matched to uninfected people, adjusted for age and sex and stratified by SARS-CoV-2 variants, and risk in patients with a breakthrough SARS-CoV-2 infection compared with unvaccinated infected controls. Risks were compared using hazard ratios and risk differences per 10 000 patients measured during the early (30-180 days) and late (180-360 days) time periods after infection.

RESULTS

Covid-19 infection was significantly associated with increased risks in early and late periods for anosmia and dysgeusia (hazard ratio 4.59 (95% confidence interval 3.63 to 5.80), risk difference 19.6 (95% confidence interval 16.9 to 22.4) in early period; 2.96 (2.29 to 3.82), 11.0 (8.5 to 13.6) in late period), cognitive impairment (1.85 (1.58 to 2.17), 12.8, (9.6 to 16.1); 1.69 (1.45 to 1.96), 13.3 (9.4 to 17.3)), dyspnoea (1.79 (1.68 to 1.90), 85.7 (76.9 to 94.5); 1.30 (1.22 to 1.38), 35.4 (26.3 to 44.6)), weakness (1.78 (1.69 to 1.88), 108.5, 98.4 to 118.6; 1.30 (1.22 to 1.37), 50.2 (39.4 to 61.1)), and palpitations (1.49 (1.35 to 1.64), 22.1 (16.8 to 27.4); 1.16 (1.05 to 1.27), 8.3 (2.4 to 14.1)) and with significant but lower excess risk for streptococcal tonsillitis and dizziness. Hair loss, chest pain, cough, myalgia, and respiratory disorders were significantly increased only during the early phase. Male and female patients showed minor differences, and children had fewer outcomes than adults during the early phase of covid-19, which mostly resolved in the late period. Findings remained consistent across SARS-CoV-2 variants. Vaccinated patients with a breakthrough SARS-CoV-2 infection had a lower risk for dyspnoea and similar risk for other outcomes compared with unvaccinated infected patients.

CONCLUSIONS

This nationwide study suggests that patients with mild covid-19 are at risk for a small number of health outcomes, most of which are resolved within a year from diagnosis.

Estimating the effect of cesarean delivery on long-term childhood health across two countries

Assessing the impact of cesarean delivery (CD) on long-term childhood outcomes is challenging as conducting a randomized controlled trial is rarely feasible and inferring it from observational data may be confounded. Utilizing data from electronic health records of 737,904 births, we defined and emulated a target trial to estimate the effect of CD on predefined long-term pediatric outcomes. Causal effects were estimated using pooled logistic regression and standardized survival curves, leveraging data breadth to account for potential confounders. Diverse sensitivity analyses were performed including replication of results in an external validation set from the UK including 625,044 births. Children born in CD had an increased risk to develop asthma (10-year risk differences (95% CI) 0.64% (0.31, 0.98)), an average treatment effect of 0.10 (0.07-0.12) on body mass index (BMI) z-scores at age 5 years old and 0.92 (0.68-1.14) on the number of respiratory infection events until 5 years of age. A positive 10-year risk difference was also observed for atopy (10-year risk differences (95% CI) 0.74% (-0.06, 1.52)) and allergy 0.47% (-0.32, 1.28)). Increased risk for these outcomes was also observed in the UK cohort. Our findings add to a growing body of evidence on the long-term effects of CD on pediatric morbidity, may assist in the decision to perform CD when not medically indicated and paves the way to future research on the mechanisms underlying these effects and intervention strategies targeting them.

Results of an early second PCR test performed on SARS-CoV-2 positive patients may support risk assessment for severe COVID-19

Identifying patients at increased risk for severe COVID-19 is of high priority during the pandemic as it could affect clinical management and shape public health guidelines. In this study we assessed whether a second PCR test conducted 2–7 days after a SARS-CoV-2 positive test could identify patients at risk for severe illness. Analysis of a nationwide electronic health records data of 1683 SARS-CoV-2 positive individuals indicated that a second negative PCR test result was associated with lower risk for severe illness compared to a positive result. This association was seen across different age groups and clinical settings. More importantly, it was not limited to recovering patients but also observed in patients who still had evidence of COVID-19 as determined by a subsequent positive PCR test. Our study suggests that an early second PCR test may be used as a supportive risk-assessment tool to improve disease management and patient care.

Remote allergen exposure elicits eosinophil infiltration into allergen nonexposed mucosal organs and primes for allergic inflammation

The natural history of allergic diseases suggests bidirectional and progressive relationships between allergic disorders of the skin, lung, and gut indicative of mucosal organ crosstalk. However, impacts of local allergic inflammation on the cellular landscape of remote mucosal organs along the skin:lung:gut axis are not yet known. Eosinophils are tissue-dwelling innate immune leukocytes associated with allergic diseases. Emerging data suggest heterogeneous phenotypes of tissue-dwelling eosinophils contribute to multifaceted roles that favor homeostasis or disease. This study investigated the impact of acute local allergen exposure on the frequency and phenotype of tissue eosinophils within remote mucosal organs. Our findings demonstrate allergen challenge to skin, lung, or gut elicited not only local eosinophilic inflammation, but also increased the number and frequency of eosinophils within remote, allergen nonexposed lung, and intestine. Remote allergen-elicited lung eosinophils exhibited an inflammatory phenotype and their presence associated with enhanced susceptibility to airway inflammation induced upon subsequent inhalation of a different allergen. These data demonstrate, for the first time, a direct effect of acute allergic inflammation on the phenotype and frequency of tissue eosinophils within antigen nonexposed remote mucosal tissues associated with remote organ priming for allergic inflammation.

Creating the real-world medical record: Using digital patient-generated data to create an updated picture of patients outcomes

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Background: Value-based healthcare requires integration of real-world data (RWD) generated by patients in parallel to clinical documentation. This gives a holistic perspective of the patients’ health and care and could lead to reduced costs and better patient care and safety. Belong digital patient-powered network (PPN) is a social network for cancer patients and caregivers providing them access to other patients, healthcare professionals and disease management tools. In this study we compared the clinical data generated by Belong users with classical clinical documentation. Furthermore we explored the additional information generated in the PPN and its value. Methods: RWD collected from users of the Belong PPN was retrospectively analyzed. We evaluated patient-reported outcomes in parallel to medical records provided voluntarily and anonymously. Data of patient journeys was extracted and mapped from medical records and social engagement in our platform using artificial intelligence (AI) engines. Data was further validated manually by the research team to assure accuracy. Results: We compared 40 treatment journeys reported by patients in Belong to their doctor summary. The data showed that patients can accurately describe their cancer diagnosis and treatment, mentioning 85% and 90% of their diagnosis and treatment, respectively. In 38% of the cases, patients’ engagement data provided additional insights in the categories of OTC drugs, supplements, diet, alternative treatments, lifestyle changes and emotional health. Complementary information from patients with possible clinical consequences (changes in sugar levels, blood pressure, body minerals levels etc.) was also reported and could affect patients’ treatment and well-being. Conclusions: RWD collected in the Belong PPN recreated a comparable clinical description of standard medical documents and provided additional insights that created a more comprehensive picture of patients’ health. Superimposing the social data layer onto the clinical one could provide significant advancement of how we treat patients and result in better cost-efficiency, improved healthcare services and patients’ outcomes.

Unveiling the real-world outcomes of breast cancer (BC) patients with taxanes-induced neuropathy using a digital patient-powered network (PPN)

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Background: Taxanes-induced neuropathy is common in BC patients receiving taxanes, forcing dose reductions and treatment delays and posing serious challenges for the long-term patient QoL. Discovering neuropathy predictors in patients could guide better treatment decisions, improved QoL and reduce healthcare costs. Belong digital PPN is a social network for cancer patients and caregivers that supports disease management. In this study we used our artificial intelligence (AI) engine to classify the prevalence, characteristics and taxanes-induced neuropathy status of BC patients. Methods: We analyzed real-world patient-reported outcomes provided voluntarily and anonymously from users on the Belong PPN. Data from BC patients reporting treatment with taxanes was extracted and additional analysis segmented the data to those who experienced neuropathy and those who did not. Further validation of the data was performed by our research team to assure accuracy. Results: We evaluated 169 BC cancer patients from the US treated with taxanes. In the cohort 72% were Paclitaxel-treated and 28% Docetaxel-treated at various disease stages: 68% at early stage BC (0-2) and 32% at the advanced/metastatic stages (3-4). 83% of Paclitaxel-treated patients and 67% of Docetaxel-treated patients reported experiencing neuropathy in the Belong platform. These real-world reports indicated significantly higher incidence of taxane-induced neuropathy in comparison to literature summarizing data from clinical trials, suggesting neuropathy incidence of 27% for paclitaxel and 16% for docetaxel (grades 2-4). Conclusions: Real-world patient-reported outcomes from the Belong PPN captured the prevalence of taxanes-induced neuropathy in BC patients and correlated it to the specific drug in use. Evidence for higher incidence of taxanes-induced neuropathy may lead to lower patient QoL and higher healthcare costs and should stimulate better treatment decisions. Further exploration of the gap between controlled clinical studies and real-world evidence is urgently needed to understand the true patient outcomes and optimize healthcare accordingly.

Airway CD8(+) T cells induced by pulmonary DNA immunization mediate protective anti-viral immunity

Vaccination strategies for protection against a number of respiratory pathogens must induce T-cell populations in both the pulmonary airways and peripheral lymphoid organs. In this study, we show that pulmonary immunization using plasmid DNA formulated with the polymer polyethyleneimine (PEI-DNA) induced antigen-specific CD8(+) T cells in the airways that persisted long after antigen local clearance. The persistence of the cells was not mediated by local lymphocyte proliferation or persistent antigen presentation within the lung or airways. These vaccine-induced CD8(+) T cells effectively mediated protective immunity against respiratory challenges with vaccinia virus and influenza virus. Moreover, this protection was not dependent upon the recruitment of T cells from peripheral sites. These findings demonstrate that pulmonary immunization with PEI-DNA is an efficient approach for inducing robust pulmonary CD8(+) T-cell populations that are effective at protecting against respiratory pathogens.

CCL11 elicits secretion of RNases from mouse eosinophils and their cell-free granules

Rapid secretion of eosinophil-associated RNases (EARs), such as the human eosinophilic cationic protein (ECP), from intracellular granules is central to the role of eosinophils in allergic diseases and host immunity. Our knowledge regarding allergic inflammation has advanced based on mouse experimental models. However, unlike human eosinophils, capacities of mouse eosinophils to secrete granule proteins have been controversial. To study mechanisms of mouse eosinophil secretion and EAR release, we combined an RNase assay of mouse EARs with ultrastructural studies. In vitro, mouse eosinophils stimulated with the chemokine eotaxin-1 (CCL11) secreted enzymatically active EARs (EC(50) 5 nM) by piecemeal degranulation. In vivo, in a mouse model of allergic airway inflammation, increased airway eosinophil infiltration (24-fold) correlated with secretion of active RNases (3-fold). Moreover, we found that eosinophilic inflammation in mice can involve eosinophil cytolysis and release of cell-free granules. Cell-free mouse eosinophil granules expressed functional CCR3 receptors and secreted their granule proteins, including EAR and eosinophil peroxidase in response to CCL11. Collectively, these data demonstrate chemokine-dependent secretion of EARs from both intact mouse eosinophils and their cell-free granules, findings pertinent to understanding the pathogenesis of eosinophil-associated diseases, in which EARs are key factors.

Thy1+ NK [corrected] cells from vaccinia virus-primed mice confer protection against vaccinia virus challenge in the absence of adaptive lymphocytes

While immunological memory has long been considered the province of T- and B- lymphocytes, it has recently been reported that innate cell populations are capable of mediating memory responses. We now show that an innate memory immune response is generated in mice following infection with vaccinia virus, a poxvirus for which no cognate germline-encoded receptor has been identified. This immune response results in viral clearance in the absence of classical adaptive T and B lymphocyte populations, and is mediated by a Thy1⁺ subset of natural killer (NK) cells. We demonstrate that immune protection against infection from a lethal dose of virus can be adoptively transferred with memory hepatic Thy1⁺ NK cells that were primed with live virus. Our results also indicate that, like classical immunological memory, stronger innate memory responses form in response to priming with live virus than a highly attenuated vector. These results demonstrate that a defined innate memory cell population alone can provide host protection against a lethal systemic infection through viral clearance.

Immunological memory is a hallmark of adaptive immunity and provides the basis for our ability to become ‘immune’ to pathogens to which we have previously been exposed, and provides the basis for vaccination. For decades, the paradigm held that only the classical adaptive lymphocytes were capable of forming and maintaining protective immunological memory. Recently, several papers have shown the capacity of an innate cell population, a subset of natural killer (NK) cells, to exhibit certain aspects of immunological memory. Here we show that innate memory forms in response to infection with vaccinia virus and resides in a discrete subset of NK cells. We further demonstrate that this innate memory provides significant host protection against a subsequent systemic infection with a lethal dose of vaccinia virus, in some cases resulting in the complete clearance of detectable virus. We also demonstrate that priming with live, replicating virus stimulates innate memory more robustly than a highly attenuated vector. These findings shed new light on this emergent area of immunology, and hold significant implications for harnessing innate memory as part of creating novel vaccination strategies.

A matter of timing: unsynchronized antigen expression and antigen presentation diminish secondary T cell responses

Despite the low and short expression of secondary Ag, prime-boost immunizations using homologous or heterologous vectors are capable of amplifying memory CD8(+) T cells. This is mainly attributed to the rapid presentation of Ag by APCs and the high proliferative capacity of memory CD8(+) T cells. Nevertheless, certain viruses and vectors often require prolonged Ag presentation for optimal T cell priming, and the influence of such a prolonged presentation during secondary immune induction is not clear. To address this issue, we primed and boosted mice intradermally (i.d.) with plasmid DNA that was recently reported to require prolonged Ag presentation for maximal CD8(+) T cell priming. Although functional memory CD8(+) T cells were present in the mice after i.d. priming, the secondary CD8(+) T cell response elicited was limited and reached a similar level of that observed during priming. The initial levels of secondary Ag expressed in the boosted mice were sufficient to prime CD8(+) T cell response in naive hosts, suggesting that lower Ag load alone does not explain the limited secondary immune responses observed. Removal of the injection site 5 or 10 days after i.d. boosting immunization resulted in diminished Ag presentation and no expansion of memory CD8(+) T cells. In fact, Ag-presenting activity following boost occurred mainly two weeks postimmunization, a time when the Ag was no longer expressed in situ. These findings suggest that when the boosting vector triggers prolonged Ag presentation, the lack of synchronicity between Ag accessibility and Ag presentation limits secondary immune responses.

Pulmonary delivery of DNA encoding Mycobacterium tuberculosis latency antigen Rv1733c associated to PLGA-PEI nanoparticles enhances T cell responses in a DNA prime/protein boost vaccination regimen in mice

During persistent infection and hypoxic-stress, Mycobacterium tuberculosis (Mtb) expresses a series of Mtb latency antigens. The aim of this study was to evaluate the immunogenicity of a DNA vaccine encoding the Mtb latency antigen Rv1733c and to explore the effect of pulmonary delivery and co-formulation with poly (d,l-lactide-co-glycolide) (PLGA)-polyethyleneimine (PEI) nanoparticles (np) on host immunity. Characterization studies indicated that PLGA-PEI np kept their nanometer size after concentration and were positively charged. The np were able to mature human dendritic cells and stimulated them to secrete IL-12 and TNF-alpha comparable to levels observed after lipopolysaccharide (LPS) stimulation. Mtb latency antigen Rv1733c DNA prime combined with Rv1733c protein boost enhanced T cell proliferation and IFN-gamma secretion in mice in response to Rv1733c and Mtb hypoxic lysate. Rv1733c DNA adsorbed to PLGA-PEI np and applied to the lungs increased T cell proliferation and IFN-gamma production more potently compared to the same vaccinations given intramuscularly. The strongest immunogenicity was obtained by pulmonary priming with np-adsorbed Rv1733c DNA followed by boosting with Rv1733c protein. These results confirm that PLGA-PEI np are an efficient DNA vaccine delivery system to enhance T cell responses through pulmonary delivery in a DNA prime/protein boost vaccine regimen.

Pulmonary DNA vaccination: concepts, possibilities and perspectives

Mucosal immunity establishes the first line of defence against pathogens entering the body via mucosal surfaces. Besides eliciting both local and systemic immunity, mucosal vaccination strategies that are non-invasive in nature may increase patient compliance and reduce the need for vaccine application by trained personnel. A relatively new concept is mucosal immunization using DNA vaccines. The advantages of DNA vaccines, such as the opportunity to combine the genetic information of various antigen epitopes and stimulatory cytokines, the enhanced stability and ease of production make this class of vaccines attractive and suitable for mucosal application. In contrast to the area of intranasal vaccination, only a few recent studies have focused on pulmonary immunization and the involvement of the pulmonary immune system in eliciting protective immune responses against inhaled pathogens. This review focuses on DNA vaccine delivery to the lung as a promising approach to prevent pulmonary-associated diseases caused by inhaled pathogens. Attractive immunological features of the lung as a site for immunization, the mechanisms of action of DNA vaccines and the pulmonary application of such vaccines using novel delivery systems will be discussed. We also examine pulmonary diseases prone to prevention or therapeutical intervention by application of DNA vaccines.

Non-invasive pulmonary aerosol delivery in mice by the endotracheal route

In this report we present in detail a non-invasive pulmonary application method that can be a useful tool in studying drug and vaccine delivery to the lower airways. In this method the formulation is sprayed directly into the lungs of mice via the endotracheal route using a MicroSprayer aerolizer. Mean droplet size produced was 8 microm, appropriate for deposition in the large airways. Endotracheal application of suspension of fluorescent nanospheres, 200 nm in size, by this method resulted in nanoparticle deposition in the smaller airways (bronchi and bronchioles). Mice showed full recovery one day after administration of 50 microl of formulation. Furthermore, no mortality was observed as a result of the technique. We conclude that this endotracheal application is a useful tool for studying pulmonary drug delivery in mice. The technique is especially useful for the pulmonary application of vaccines, since it enables multiple administrations without a need for analgesics.

PLGA-PEI nanoparticles for gene delivery to pulmonary epithelium

Pulmonary gene delivery is thought to play an important role in treating genetically related diseases and may induce immunity towards pathogens entering the body via the airways. In this study we prepared poly (d,l-lactide-co-glycolide) (PLGA) nanoparticles bearing polyethyleneimine (PEI) on their surface and characterized them for their potential in serving as non-viral gene carriers to the pulmonary epithelium. Particles that were synthesized at different PLGA–PEI ratios and loaded with DNA in several PEI–DNA ratios, exhibited narrow size distribution in all formulations, with mean particle sizes ranging between 207 and 231 nm. Zeta potential was strongly positive (above 30 mV) for all the PEI–DNA ratios examined and the loading efficiency exceeded 99% for all formulations. Internalization of the DNA-loaded PLGA–PEI nanoparticles was studied in the human airway submucosal epithelial cell line, Calu-3, and DNA was detected in the endo-lysosomal compartment 6 h after particles were applied. Cytotoxicity of these nanoparticles was dependent on the PEI–DNA ratio and best cell viability was achieved by PEI–DNA ratios 1:1 and 0.5:1. These findings demonstrate that PLGA–PEI nanoparticles are a potential new delivery system to carry genes to the lung epithelium.

Cationic submicron emulsions for pulmonary DNA immunization

Pulmonary immunization against inhaled pathogens such as Mycobacterium tuberculosis would induce local and systemic immune responses and protect from entry and dissemination of the pathogen. The aim of this study was to evaluate cationic submicron emulsion as a potential carrier for DNA vaccines to the lung. DNA loaded emulsions were 128-152 nm in size and retained positive zeta potential above +40 mV during 3 months of storage. Loading efficiency was above 99%, DNA was protected from DNase I degradation up to 60 min and was stable in presence of 75% fetal calf serum (FCS). The plasmid DNA was detected in the endo-lysosomal compartment of the human bronchial cell line, Calu-3, 6 h after application. No cytotoxic effect on these cells was observed. Human dendritic cells were matured in presence of DNA loaded emulsion, although to a lesser extent than DNA solution indicating slower release and lower exposure to unmethylated CpG sequences. These results indicate that cationic submicron emulsions are potential DNA vaccine carriers to the lung since they are able to transfect pulmonary epithelial cells, which possibly induce cross priming of antigen presenting cells and directly activate dendritic cells, resulting in stimulation of antigen specific T-cells.

Pulmonary delivery of chitosan-DNA nanoparticles enhances the immunogenicity of a DNA vaccine encoding HLA-A*0201-restricted T-cell epitopes of Mycobacterium tuberculosis

In this study, we used an HLA-A2 transgenic mouse model to investigate the effects of pulmonary delivery of a new DNA plasmid encoding eight HLA-A*0201-restricted T-cell epitopes from Mycobacterium tuberculosis formulated in chitosan nanoparticles. It was shown that the chitosan-DNA formulation was able to induce the maturation of dendritic cells (DCs) while chitosan solution alone could not, indicating the DNA was released from the particles and able to stimulate DCs. Pulmonary administration of the DNA plasmid incorporated in chitosan nanoparticles was shown to induce increased levels of IFN-gamma secretion compared to pulmonary delivery of plasmid in solution or the more frequently used intramuscular immunization route. These results indicate that pulmonary delivery of DNA vaccines against tuberculosis may provide an advantageous delivery route compared to intramuscular immunization, and that increased immunogenicity can be achieved by delivery of this DNA encapsulated in chitosan nanoparticles.

Generation of Toxoplasma gondii GRA1 protein and DNA vaccine loaded chitosan particles: preparation, characterization, and preliminary in vivo studies

Chitosan microparticles as carriers for GRA-1 protein vaccine were prepared and characterized with respect to loading efficiency and GRA-1 stability after short-term storage. Chitosan nanoparticles as carriers for GRA-1 pDNA vaccine were prepared and characterized with respect to size, zeta potential, and protection of the pDNA vaccine against degradation by DNase I. Both protein and pDNA vaccine preparations were tested with regard to their potential to elicit GRA-1-specific immune response after intragastric administration using different prime/boost regimen. The immune response was measured by determination of IgG2a and IgG1 antibody titers. It was shown that priming with GRA1 protein vaccine loaded chitosan particles and boosting with GRA1 pDNA vaccine resulted in high anti-GRA1 antibodies, characterized by a mixed IgG2a/IgG1 ratio. These results showed that oral delivery of vaccines using chitosan as a carrier material appears to be beneficial for inducing an immune response against Toxoplasma gondii. The type of immune response, however, will largely depend on the prime/boost regimen and the type of vaccine used.