Malnutrition and vaccination in developing countries

Malnutrition contributes to an estimated 45% of deaths among children under 5 years of age in developing countries, predominantly due to infections. Malnourished children therefore stand to benefit hugely from vaccination, but malnutrition has been described as the most common immunodeficiency globally, suggesting that they may not be able to respond effectively to vaccines. The immunology of malnutrition remains poorly characterized, but is associated with impairments in mucosal barrier integrity, and innate and adaptive immune dysfunction. Despite this, the majority of malnourished children can mount a protective immune response following vaccination, although the timing, quality and duration of responses may be impaired. This paper reviews the evidence for vaccine immunogenicity in malnourished children, discusses the importance of vaccination in prevention of malnutrition and highlights evidence gaps in our current knowledge.     

Oral vaccination against Helicobacter pylori with recombinant cholera toxin B-subunit

BACKGROUND: The innocuous pure recombinant cholera toxin B-subunit (rCTB) is very attractive as a strong adjuvant for host immunization, but little is known about rCTB's gastric mucosal immunoadjuvanticity against Helicobacter pylori. The immunoadjuvanticity of rCTB against H. pylori was tested. MATERIAL AND METHODS: Mice were immunized with sonicated H. pylori and rCTB orally or intranasally and sacrificed on day 42 after immunization. Passive cutaneous anaphylaxis (PCA) test was performed to evaluate IgE-mediated anaphylaxis with serum from mice to which H. pylori-antigen with rCTB had been administered. Immunoglobulin titer specific to H. pylori in serum, lavation of the gastrointestinal tracts and feces were examined. Gastritis in vaccinated mice after a challenge was assessed with the scoring defined from grading of gastric inflammation. H. pylori proliferation after immunization was investigated by counting colony forming units (CFU) per gram of stomach tissue. RESULTS: PCA test exhibited no reactions against the serum from mice immunized with H. pylori-antigen with rCTB administered orally and intranasally. Oral and nasal coadministrations of rCTB significantly raised systemic and mucosal immunities against H. pylori and suppressed proliferation of H. pylori in gastric mucosa. The score of gastritis in mice immunized orally was significantly higher than that of mice immunized nasally due to postimmunization gastritis. Only oral administration of rCTB suppressed H. pylori proliferation as compared with intranasal administration and without rCTB. CONCLUSIONS: The present study indicated that rCTB has systemic and mucosal immunoadjuvanticities against H. pylori and that oral vaccination with rCTB might additively support antibiotic eradication.     

A Salmonella Typhi homologue of bacteriophage muramidases controls typhoid toxin secretion

Unlike other Salmonella , which can infect a broad range of hosts causing self‐limiting infection , Salmonella Typhi is an exclusively human pathogen that causes typhoid fever, a life‐threatening systemic disease. Typhoid toxin is a unique virulence factor of Salmonella Typhi, which is expressed when the bacteria are within mammalian cells. Here, we report that an N ‐acetyl‐β‐D ‐muramidase similar to phage endolysins encoded within the same pathogenicity islet as the toxin is required for typhoid toxin secretion. Genetic and functional analysis of TtsA revealed unique amino acids at its predicted peptidoglycan‐binding domain that are essential for protein secretion and that distinguishes this protein from other homologues. We propose that TtsA defines a new protein secretion mechanism recently evolved from the machine that mediates phage release.     

DNA vaccination against tumors

DNA vaccines have been used to generate protective immunity against tumors in a variety of experimental models. The favorite target antigens have been those that are frequently expressed by human tumors, such as carcinoembryonic antigen (CEA), ErbB2/neu, and melanoma-associated antigens. DNA vaccines have the advantage of being simple to construct, produce and deliver. They can activate all arms of the immune system, and allow substantial flexibility in modifying the type of immune response generated through codelivery of cytokine genes. DNA vaccines can be applied by intramuscular, dermal/epidermal, oral, respiratory and other routes, and pose relatively few safety concerns. Compared to other nucleic acid vectors, they are usually devoid of viral or bacterial antigens and can be designed to deliver only the target tumor antigen(s). This is likely to be important when priming a response against weak tumor antigens. DNA vaccines have been more effective in rodents than in larger mammals or humans. However, a large number of methods that might be applied clinically have been shown to ameliorate these vaccines. This includes in vivo electroporation, and/or inclusion of various immunostimulatory molecules, xenoantigens (or their epitopes), antigen-cytokine fusion genes, agents that improve antigen uptake or presentation, and molecules that activate innate immunity mechanisms. In addition, CpG motifs carried by plasmids can overcome the negative effects of regulatory T cells. There have been few studies in humans, but recent clinical trials suggest that plasmid/virus, or plasmid/antigen-adjuvant, prime-boost strategies generate strong immune responses, and confirm the usefulness of plasmid-based vaccination.     

Neutralising antibodies against ricin toxin

The Centers for Disease Control and Prevention have listed the potential bioweapon ricin as a Category B Agent. Ricin is a so-called A/B toxin produced by plants and is one of the deadliest molecules known. It is easy to prepare and no curative treatment is available. An immunotherapeutic approach could be of interest to attenuate or neutralise the effects of the toxin. We sought to characterise neutralising monoclonal antibodies against ricin and to develop an effective therapy. For this purpose, mouse monoclonal antibodies (mAbs) were produced against the two chains of ricin toxin (RTA and RTB). Seven mAbs were selected for their capacity to neutralise the cytotoxic effects of ricin in vitro. Three of these, two anti-RTB (RB34 and RB37) and one anti-RTA (RA36), when used in combination improved neutralising capacity in vitro with an IC(50) of 31 ng/ml. Passive administration of association of these three mixed mAbs (4.7 μg) protected mice from intranasal challenges with ricin (5 LD(50)). Among those three antibodies, anti-RTB antibodies protected mice more efficiently than the anti-RTA antibody. The combination of the three antibodies protected mice up to 7.5 hours after ricin challenge. The strong in vivo neutralising capacity of this three mAbs combination makes it potentially useful for immunotherapeutic purposes in the case of ricin poisoning or possibly for prevention.