Serum antibody titres to Shigella lipopolysaccharides and invasion plasmid antigens in healthy Costa Rican and Swedish women

Highly homogenous tri-acylated S-LPS acts as a novel clinically applicable vaccine against Shigella flexneri 2a infection

Shigellosis, a major cause of diarrhea worldwide, exhibits high morbidity and mortality in children. Specificity of Shigella immunity is determined by the structure of the main protective O-antigen polysaccharide component incorporated into the lipopolysaccharide (LPS) molecule. Endotoxicity, however, precludes LPS clinical use. Thus, there is still no vaccine against the most prevalent shigellosis species (serotype S. flexneri 2a), despite ongoing efforts focused on inducing serotype-specific immunity. As LPS is highly heterogenous, we hypothesized that more homogenous pools of LPS might be less toxic. We developed a method to generate a homogenous S. flexneri 2a LPS subfraction, Ac₃-S-LPS, containing long chain O-specific polysaccharide (S-LPS) and mainly tri-acylated lipid A, with no penta- and hexa-acylated, and rare tetra-acylated lipid A. Ac₃-S-LPS had dramatically reduced pyrogenicity and protected guinea pigs from shigellosis. In volunteers, 50 µg of injected Ac₃-S-LPS vaccine was safe, with low pyrogenicity, no severe and few minor adverse events, and did not induce pro-inflammatory cytokines. In spite of the profound lipid A modification, the vaccine induced a prevalence of IgG and IgA antibodies. Thus, we have developed the first safe immunogenic LPS-based vaccine candidate for human administration. Homogenous underacetylated LPSs may also be useful for treating other LPS-driven human diseases. Clinical trial registry: http://grls.rosminzdrav.ru/.

The impact of socioeconomic status on foodborne illness in high-income countries: a systematic review

Foodborne illness is a major cause of morbidity and loss of productivity in developed nations. Although low socioeconomic status (SES) is generally associated with negative health outcomes, its impact on foodborne illness is poorly understood. We conducted a systematic review to examine the association between SES and laboratory-confirmed illness caused by eight important foodborne pathogens. We completed this systematic review using PubMed for all papers published between 1 January 1980 and 1 January 2013 that measured the association between foodborne illness and SES in highly developed countries and identified 16 studies covering four pathogens. The effect of SES varied across pathogens: the majority of identified studies for Campylobacter, salmonellosis, and E. coli infection showed an association between high SES and illness. The single study of listeriosis showed illness was associated with low SES. A reporting bias by SES could not be excluded. SES should be considered when targeting consumer-level public health interventions for foodborne pathogens.

Socioeconomic correlates of antibody levels to enteric pathogens among Israeli adolescents

We examined the association between socioeconomic status and the level of serum antibodies to selected faeco-orally transmitted pathogens among Israeli adolescents. Random samples of eighty volunteers aged 12-15 years from high (HSL), medium (MSL) and low (LSL) standard of living towns were included in the study. Serum samples were examined by radioimmunoassay for HAV and by in-house-developed ELISA systems for IgA and IgG antibody levels against Shigella sonnei, S. flexneri, E. coli O157:H7 lipopolysacchride and Cryptosporidium parvum antigens. Seropositivity to HAV was highest (98.8%) in the LSL towns and lowest (25%) in the HSL towns, showing a statistically significant linear trend. Antibody levels to the other enteropathogens had gender variation, with higher titres in females. Significantly lower titres in the HSL towns were found for: IgA anti-S. sonnei in females (P<0.001); IgG anti-S. sonnei in females (P=0.024) and males (P=0.033); IgG anti-S. flexneri in females (P=0.016). Inverse linear association with socioeconomic status was found for IgA anti-C. parvum in females (P<0.001); IgA anti-E. coli O157:H7 in females (P<0.001) and males (P=0.024). A statistically significant association between HAV seropositivity and higher titres of IgA anti-S. sonnei and E. coli O157:H7 was shown. In conclusion, exposure to enteropathogens transmitted via the faecal-oral route in communities of lower socioeconomic status is reflected in a higher prevalence of lifelong lasting antibodies to HAV, and higher levels of antibodies to bacterial and protozoan enteropathogens. Among females, the levels of specific serum antibodies are higher and more strongly associated with low socioeconomic status.

Immunomagnetic separation and PCR detection show Shigellae to be common faecal agents in children from urban marginal communities of Costa Rica

Culture and immunomagnetic separation-polymerase chain reaction assays (IMS-PCR) were used to isolate and identify Shigella flexneri, S. dysenteriae type I and S. sonnei in faeces from 250 children up to 5 years and from their mothers (n = 143) selected at random from a large urban marginal community of Costa Rica. Children hospitalized because of severe diarrhoea (n = 110) were also studied. Only S. flexneri, mainly serotype 2a, and S. sonnei were found by culture. All specimens in which Shigella was cultured were also positive by the corresponding IMS-PCR. S. flexneri was isolated by culture from 1 (0.7%) mother and 4 (1.6%) community children. S. sonnei was found in 2 (0.8%) children. An additional 12 S. flexneri and four S. sonnei in the community children were found by IMS-PCR. In total, Shigella was cultured from 0.7% of mothers and 2.4% of children. By the IMS-PCR 2% of mothers and 8% of children were positive. S. flexneri was isolated by culture from 14 (12.7%) hospitalized children and S. sonnei from 1 (0.9%). An additional 11 S. flexneri and three S. sonnei were found by IMS-PCR. In total, Shigella was cultured from 13.6% of hospitalized children. By the IMS-PCR 26% of them were Shigella positive. Thus IMS-PCR was more than twice as effective in diagnosing shigellae as culture. Twelve (60%) Shigella positive community children were above 3-years-old and 25% of them were under one year. Seven (35%) of the Shigella positive children had dysenteric and 9 (45%) normal stools. Half of the Shigella infected community children had been weaned before the 3 months of age. By the age of 5 months, 90% of them were already weaned. Seventeen (59%) of the hospitalized Shigella positive children were under 1 year of age. The stools were watery or semiliquid in 13 (45%) and dysenteric in 12 (41%) of them. We conclude that shigellosis is common in Costa Rica and represents an important cause of severe infant diarrhoea requiring hospitalization.