Defective anti-polysaccharide IgG vaccine responses in IgA deficient mice

IgG antibody response to pneumococcal-conjugated vaccine (Prevenar®13) in children with immunodeficiency disorders

Measurement of anti-pneumococcal capsular polysaccharides (anti-PnPs) IgG titers is an important tool in the immunologic assessment of patients with suspected immunodeficiency disorders (ID) to reduce the morbi-mortality and minimize severe infections. Retrospectively, we studied the relationship among anti-PnPs IgG response to 3 doses of Prevenar®13, levels of immune system components, leukocyte populations, and clinical data in children with ID. Serum samples were collected at least 4 weeks post vaccination. Subsequently, multi-serotype enzyme-linked immunosorbent assay (ELISA) was performed. Eighty-seven children (under 12 years) were enrolled. Primary immunodeficiency disorder (PID) was the most common disorder (45) followed by possible immunodeficiency disorder (POID) (19), secondary immunodeficiency disorder (SID) (15), and mixed immunodeficiency disorder (MID) (8). The median age was 3 (1.50-5.33) years, 65% of patients were male. Deficient production of anti-PnPs IgG (titer ≤ 50 mg/L) was detected in 47 patients (54%), especially in the MID group, all of them under immunosuppressive therapy. In PCV13 responders, the mean of leukocyte population levels was higher with statistically significance differences in CD4 + /CD8 + T lymphocytes (p = 0.372, p = 0.014) and CD56 + /CD16 + NK (p = 0.016). Patients with previous bone marrow transplantation were the worst PCV13 responders. Pneumococcal IgG antibody titers (post-vaccination) along with clinical and analytical markers represented.

The Interleukin-33-Group 2 Innate Lymphoid Cell Axis Represents a Potential Adjuvant Target To Increase the Cross-Protective Efficacy of Influenza Vaccine

Interleukin-33 (IL-33) is a multifunctional cytokine that mediates type 2-dominated immune responses. In contrast, the role of IL-33 during viral vaccination, which often aims to induce type 1 immunity, has not been fully investigated. Here, we examined the effects of IL-33 on influenza vaccine responses. We found that intranasal coadministration of IL-33 with an inactivated influenza virus vaccine increases vaccine efficacy against influenza virus infection, not only with the homologous strain but also with heterologous strains, including the 2009 H1N1 influenza virus pandemic strain. Cross-protection was dependent on group 2 innate lymphoid cells (ILC2s), as the beneficial effect of IL-33 on vaccine efficacy was abrogated in ILC2-deficient C57BL/6 Il7r^Cre/+ Rora^fl/fl mice. Furthermore, mechanistic studies revealed that IL-33-activated ILC2s potentiate vaccine efficacy by enhancing mucosal humoral immunity, particularly IgA responses, potentially in a Th2 cytokine-dependent manner. Our results demonstrate that IL-33-mediated activation of ILC2s is a critical early event that is important for the induction of mucosal humoral immunity, which in turn is responsible for cross-strain protection against influenza. Thus, we reveal a previously unrecognized role for the IL-33-ILC2 axis in establishing broadly protective and long-lasting humoral mucosal immunity against influenza, knowledge that may help in the development of a universal influenza vaccine. IMPORTANCE Current influenza vaccines, although capable of protecting against predicted viruses/strains included in the vaccine, are inept at providing cross-protection against emerging/novel strains. Thus, we are in critical need of a universal vaccine that can protect against a wide range of influenza viruses. Our novel findings show that a mucosal vaccination strategy involving the activation of lung ILC2s is highly effective in eliciting cross-protective humoral immunity in the lungs. This suggests that the biology of lung ILC2s can be exploited to increase the cross-reactivity of commercially available influenza subunit vaccines.

Francisella and Antibodies

Immune responses to intracellular pathogens depend largely upon the activation of T helper type 1-dependent mechanisms. The contribution of B cells to establishing protective immunity has long been underestimated. Francisella tularensis, including a number of subspecies, provides a suitable model for the study of immune responses against intracellular bacterial pathogens. We previously demonstrated that Francisella infects B cells and activates B-cell subtypes to produce a number of cytokines and express the activation markers. Recently, we documented the early production of natural antibodies as a consequence of Francisella infection in mice. Here, we summarize current knowledge on the innate and acquired humoral immune responses initiated by Francisella infection and their relationships with the immune defense systems.

Interaction between IgA and gut microbiota and its role in controlling metabolic syndrome

Immunoglobulin A (IgA) is the most abundant immunoglobulin isotype secreted into the mucosal tissues, mainly intestinal mucus. Humans can produce several grams of IgA every day, accounting for three quarters of the body's total immunoglobulin content. IgA, together with mucus and antimicrobial peptides, forms the first line of defence for intestinal epithelial cells, protecting them from a significant number of intestinal antigens. IgA also plays a principal role in controlling the gut microbiota (GM), and disruption in IgA can result in dysbiosis, such as the enrichment of Proteobacteria, which are generally bound by IgA. Proteobacteria overexpansion is also usually seen in obesity and colitis. Consistent with this, IgA dysfunction frequently results in metabolic syndrome (MetS), including conditions such as obesity, adiposity, insulin resistance, and inflammation. In contrast, enhanced IgA function can improve, and even prevent, MetS. Interactions among IgA, GM, and metabolism provide a promising avenue to combat MetS.

Specialization of mucosal immunoglobulins in pathogen control and microbiota homeostasis occurred early in vertebrate evolution

Although mammalian secretory immunoglobulin A (sIgA) targets mucosal pathogens for elimination, its interaction with the microbiota also enables commensal colonization and homeostasis. This paradoxical requirement in the control of pathogens versus microbiota raised the question of whether mucosal (secretory) Igs (sIgs) evolved primarily to protect mucosal surfaces from pathogens or to maintain microbiome homeostasis. To address this central question, we used a primitive vertebrate species (rainbow trout) in which we temporarily depleted its mucosal Ig (sIgT). Fish devoid of sIgT became highly susceptible to a mucosal parasite and failed to develop compensatory IgM responses against it. IgT depletion also induced a profound dysbiosis marked by the loss of sIgT-coated beneficial taxa, expansion of pathobionts, tissue damage, and inflammation. Restitution of sIgT levels in IgT-depleted fish led to a reversal of microbial translocation and tissue damage, as well as to restoration of microbiome homeostasis. Our findings indicate that specialization of sIgs in pathogen and microbiota control occurred concurrently early in evolution, thus revealing primordially conserved principles under which primitive and modern sIgs operate in the control of microbes at mucosal surfaces.

Effectiveness of Haemophilus influenzae type b vaccination after splenectomy - impact on selected immunological parameters

Splenectomy is a surgery indicated in case of splenic rupture after injury, when there are tumors in the spleen, or as a treatment for certain diseases, such as idiopathic thrombocytopenic purpura and spherocytosis. The aims of the study were to assess the immunological response to the Haemophilus influenzae type b (Hib) vaccine and the post-vaccination changes in lymphocyte subsets and cell activation markers in splenectomized patients and healthy volunteers. Blood samples were collected from 25 patients that had undergone splenectomy and from 15 healthy, non-splenectomized volunteers. All participants received a single dose of Hib vaccine. The concentration of specific Hib antibodies was assessed by an enzyme-linked immunosorbent assay. Selected immune cell populations were evaluated using flow cytometry. The analysis of the antibody titers against Hib showed statistically significant differences in both groups. There was a significantly higher percentage (p = 0.0012) and absolute value (p = 0.0003) of natural killer T (NKT)-like cells (CD3+/CD16+ CD56+) in the study group, compared to the control group. The levels of natural killer (NK) and NKT cells did not change relative to the cause and age of splenectomy. The quantity and percentage of regulatory T (Treg) cells were higher in the study group compared to the control group (p < 0.0001). No significant correlations were found between the time elapsed since splenectomy, the age of the patients, and the Treg levels. Our study showed that spleen resection results in an important deterioration of Treg cells and Th17 cell balance which may contribute to an incomplete immunological response.

Influenza Vaccination Protects Against Pandemic H1N1 Infection in Sickle Cell Disease Mice

Influenza infection is associated with enhanced pathology in individuals with sickle cell disease (SCD). Despite being a high priority group for annual influenza vaccination, little is known about long-term responses to influenza vaccination in this patient population. To model flu vaccination, we inoculated SCD and wild type (WT) littermate mice with the seasonal flu vaccine [containing pandemic H1N1 (pH1N1) antigen], bled the mice before and after vaccination, and intranasally challenged them with a high dose (400 PFU) of pH1N1 12 weeks later. Both WT and SCD mice were fully protected from infection, and anti-influenza immunoglobulin G titers were significantly elevated in both groups after vaccination. It appears that flu vaccination is effective in SCD mice and our data support the clinical practice of regular flu vaccination in SCD patients.