Oral Immunotherapy With Human Secretory Immunoglobulin A Improves Survival in the Hamster Model of Clostridioides difficile Infection.

Coadministration of human secretory IgA (sIgA) together with subtherapeutic vancomycin enhanced survival in the Clostridioides difficile infection (CDI) hamster model. Vancomycin (5 or 10 mg/kg × 5 days) plus healthy donor plasma sIgA/monomeric IgA (TID × 21 days) or hyperimmune sIgA/monomeric IgA (BID × 13 days) enhanced survival. Survival was improved compared to vancomycin alone, P = .018 and .039 by log-rank Mantel-Cox, for healthy and hyperimmune sIgA, respectively. Passive immunization with sIgA (recombinant human secretory component plus IgA dimer/polymer from pooled human plasma) can be administered orally and prevents death in a partially treated CDI hamster model.

Treatment and Prevention of Recurrent Clostridium difficile Infection with Functionalized Bovine Antibody-Enriched Whey in a Hamster Primary Infection Model.

Toxin-induced Clostridium difficile infection (CDI) is a major disease characterized by severe diarrhea and high morbidity rates. The aim with this study was to develop an alternative drug for the treatment of CDI. Cows were repeatedly immunized to establish specific immunoglobulin G and A titers against toxins A (TcdA) and B (TcdB) and against C. difficile cells in mature milk or colostrum. The effect of three different concentrations of anti-C. difficile whey protein isolates (anti-CD-WPI) and the standard of care antibiotic vancomycin were investigated in an animal model of CD infected hamsters (6 groups, with 10 hamsters each). WPI obtained from the milk of exactly the same cows pre-immunization and a vehicle group served as negative controls. The survival of hamsters receiving anti-CD-WPI was 50, 80 and 100% compared to 10 and 0% for the control groups, respectively. Vancomycin suppressed the growth of C. difficile and thus protected the hamsters at the time of administration, but 90% of these hamsters nevertheless died shortly after discontinuation of treatment. In contrast, the surviving hamsters of the anti-CD-WPI groups survived the entire study period, although they were treated for only 75 h. The specific antibodies not only inactivated the toxins for initial suppression of CDI, but also provoked the inhibition of C. difficile growth after discontinuation, thus preventing recurrence. Oral administration of anti-CD-WPI is a functional therapy of CDI in infected hamsters for both primary treatment and prevention of recurrence. Thus, anti-CD-WPI could address the urgent unmet medical need for treating and preventing recurrent CDI in humans.

Induction of antitoxin responses in Clostridium-difficile-infected patients compared to healthy blood donors.

According to the literature Clostridium difficile antitoxins are present in up to 66% of humans. In a survey of ∼400 plasma samples from healthy blood donors we found that less than 6% were positive for anti-TcdA or anti-TcdB antitoxins. Using the same standard immunoassay protocol, we looked for IgG and IgA antitoxins in the blood and stool samples from 25 patients with C. difficile infection (CDI). Some patients with CDI had no antitoxin detected at all, while others had high levels of specific IgG- and IgA-antitoxins against both TcdA and TcdB in blood and IgA-anti-TcdA and -anti-TcdB antibodies in stool. Systemic responses to TcdB and mucosal responses to TcdA predominated. Among patients infected with the NAP1/027/BI strain, systemic IgG-anti-TcdB responses were particularly elevated. In contrast, patients infected with non-027 strains had more elevated mucosal IgA-anti-TcdA responses. Furthermore, high titer sera did not correlate with high neutralizing potential. We hypothesize that paradoxical killing of primed B-cells by antibody-mediated endosomal uptake of the Large Clostridial Toxins, TcdA and TcdB leads to clonal elimination of the fittest B-cells. If this hypothesis is confirmed, immune suppression rather than protective humoral immunity might be the consequence in some patients infected with toxigenic C. difficile.

Formalin-fixed Staphylococcus aureus particles prevent allergic sensitization in a murine model of type I allergy.

BACKGROUND: Bacterial infections are supposed to act counterregulatory to the development of allergen-specific Th2 immune responses. We analyzed whether administration of extracellular Staphylococcus aureus inhibited experimental sensitization against allergens. METHODS: BALB/c mice were immunized with alum-adsorbed ovalbumin (OVA) together with formalin-fixed Staphylococcus particles. OVA-specific antibody production and cytokine synthesis by spleen cells was analyzed. Airway reactivity and cellular infiltration into the airways was assessed after intranasal challenge of mice with OVA. In addition, the capacity of Staphylococcus particles to modulate cytokine production by bone marrow-derived dendritic cells was analyzed in vitro. RESULTS: Simultaneous application of OVA and Staphylococcus particles very efficiently inhibited production of specific IgE and IgG1 as well as secretion of IL-4 and IL-5 by splenocytes, while enhancing IgG2a formation and production of IFN-gamma, indicating a shift from a Th2 response towards a Th1-biased response. This effect was not dependent on the expression of protein A by Staphylococcus. An enhanced frequency or activity of regulatory T cells after administration of Staphylococcus particles was not apparent. Treatment of mice with Staphylococcus particles during the sensitization phase prevented lung inflammation (airway hyperreactivity, eosinophilia) after local challenge with OVA. Culture of bone marrow-derived dendritic cells with Staphylococcus particles induced IL-12p35 and p40 mRNA expression as well as secretion of IL-12p70, and increased production of IL-10 mRNA and protein. CONCLUSIONS: Administration of formalin-fixed Staphylococcus particles induced Th1-biased immune responses and prevented allergic sensitization.

Cytotoxic T cells with reciprocal antigenic peptide presentation function are not generally resistant to mutual lysis.

Cytotoxic T cells normally express major histocompatibility complex class I molecules, to which their T cell antigen receptors are restricted. Therefore, a single cytotoxic T cell can not only act as a cytolytic effector cell, but also as an antigen-presenting cell for other cytotoxic T cells of the same or a different clone. In the present paper, we used a murine cytotoxic T cell clone, 10BK.1, recognizing the ovalbumin-derived peptide OVA257-264 in combination with H-2Kb to investigate the consequences of reciprocal antigen presentation by these cytotoxic T cells. These cells proliferate after incubation with the relevant peptide in the absence of added accessory cells, indicating reciprocal antigenic peptide presentation by the cytotoxic T cell. We found that reciprocal lysis of these cells was dependent on the time point of incubation with antigen. We did not observe reciprocal lysis of cytotoxic T cells used 30 days after the last restimulation with antigen. In contrast, 10BK.1 cells used two days after the last restimulation showed an increased capacity for reciprocal lysis. The lytic capacity decreased with time after restimulation. Reciprocal lysis of 10BK.1 cells depended on reciprocal peptide presentation by at least two 10BK.1 cells. Recognition of the antigenic peptide, together with class I molecules on the surface of classical syngeneic target cells did not induce lysis of freshly stimulated 10BK.1 cells, suggesting that reciprocal lysis was not just a consequence of re-activation of the cytotoxic T cells. Reciprocal destruction of freshly activated 10BK.1 cells proceeded independent of CD95/CD95 ligand. Despite an increased secretion of tumour necrosis factor-alpha by 10BK.1 cells on day 2 after antigen stimulation, compared with cells on day 30 after stimulation, tumour necrosis factor-alpha was not responsible for the reciprocal destruction of freshly stimulated 10BK.1 cells. Lysis of preactivated 10BK.1 cells was independent of autocrine interleukin-2 production by the cytotoxic T cells, but interleukin-2 was required for optimal priming of cytotoxic T cells for reciprocal lysis.