Overexpression of O-polysaccharide chain length regulators in Gram-negative bacteria using the Wzx-/Wzy-dependent pathway enhances production of defined modal length O-polysaccharide polymers for use as haptens in glycoconjugate vaccines

Aims

O‐polysaccharide (OPS) molecules are protective antigens for several bacterial pathogens, and have broad utility as components of glycoconjugate vaccines. Variability in the OPS chain length is one obstacle towards further development of these vaccines. Introduction of sizing steps during purification of OPS molecules of suboptimal or of mixed lengths introduces additional costs and complexity while decreasing the final yield. The overall goal of this study was to demonstrate the utility of engineering Gram‐negative bacteria to produce homogenous O‐polysaccharide populations that can be used as the basis of carbohydrate vaccines by overexpressing O‐polysaccharide chain length regulators of the Wzx‐/Wzy‐dependent pathway.

Method and Results

The O‐polysaccharide chain length regulators wzzB and fepE from Salmonella Typhimurium I77 and wzz2 from Pseudomonas aeruginosa PAO1 were cloned and expressed in the homologous organism or in other Gram‐negative bacteria. Overexpression of these Wzz proteins in the homologous organism significantly increased the proportion of long or very long chain O‐polysaccharides. The same observation was made when wzzB was overexpressed in Salmonella Paratyphi A and Shigella flexneri, and wzz2 was overexpressed in two other strains of P. aeruginosa.

Conclusions

Overexpression of Wzz proteins in Gram‐negative bacteria using the Wzx/Wzy‐dependant pathway for lipopolysaccharide synthesis provides a genetic method to increase the production of an O‐polysaccharide population of a defined size.

Significance and Impact of the Study

The methods presented herein represent a cost‐effective and improved strategy for isolating preferred OPS vaccine haptens, and could facilitate the further use of O‐polysaccharides in glycoconjugate vaccine development.

Magnesium alleviates plant toxicity of aluminium and heavy metals

Magnesium (Mg) is an essential nutrient that can alleviate soilborne toxicity of many ions. This review paper critically assesses the literature on interactions and mechanisms influencing Mg alleviation of aluminium (Al) and heavy metal toxicity. Hydrated radii of Mg2+ and Al3+ are similar; therefore, these two ions compete for binding to ion transporters and other important biological molecules. In monocotyledonous species such as rice and wheat, millimolar concentrations of Mg alleviate Al toxicity, mainly by decreasing Al saturation and activity at cell wall and plasma membrane binding sites. In dicotyledonous legume species such as soybean (Glycine max), rice bean (Vigna umbellata) and broad bean (Vicia faba), micromolar concentrations of Mg may enhance biosynthesis of organic ligands and thus underpin alleviation of Al toxicity. Resistance to Al may be enhanced by increased expression of the genes coding for Mg transporters, as well as by upregulation of activity of Mg-transport proteins; intracellular Mg2+ activity may thus be increased under Al stress, which may increase the activity of H+-ATPases. In Vicia faba, Mg-related enhancement in the activity of plasma membrane H+-ATPase under Al stress was found to be due to post-translational modification (increased phosphorylation of the penultimate threonine as well as association with regulatory 14-3-3 proteins), resulting in increased resistance to Al stress. Magnesium can alleviate heavy metal stress by decreasing negative electrical potential and thus metal ion activities at the plasma membrane surface (physico-chemical competition), by enhancing activities of enzymes involved in biosynthesis of organic ligands, and by increasing vacuolar sequestration of heavy metals via increasing H+-pumping activity at the tonoplast. Future work should concentrate on characterising the role of intracellular Mg2+ homeostasis and Mg transporters in alleviating metal stress as well as in transcriptional, translational and post-translational regulation of H+-pumps and enzymes involved in biosynthesis and exudation of organic ligands.

Clinicopathologic study of lupus nephritis

Needle biopsies of kidney were done in 35 cases of systemic lupus erythematosus (SLE) with renal lesions. The lupus nephritis were classified according to WHO classification and were correlated with response to therapy and prognosis. Detailed clinical features, routine haematological, biochemical tests (e.g., serum urea, creatinine, total protein and albumin, cholesterol, etc), examination of urine (degree of proteinuria and cells) and occurrence of various auto-antibodies e.g., antinuclear antibody (ANA), anti double stranded DNA (anti DsDNA) by enzyme immunoassay (EIA) method, LE cells and rheumatoid factor (RF) were studied in all cases. Clinically hypertension was present in 19 (54.3%) cases and nephrotic range of proteinuria was detected in 20 (57.2%) cases. ANA was found in 31 (88.5%) cases, anti DsDNA 24 (68.5%) and LE cells were detected in 25 (71.5%) cases. RF was detected in 2 (5.7%) cases. Histologically the most frequent lesions were class IV occurring in 15 cases (42.8%) with initial complete remission achieved only 4 cases by immunosuppressive therapy. Active lesions were also most frequent in this class. Class III lesions were found in 8 (22.8%) cases with 6 cases had complete remission. The best prognosis was noted in class II cases with 4 out of 5 (14.3%) cases had complete remission. Class V lesions were found in 6 (17.2%) cases with complete remission achieved in 3 cases. Only one patient presented with class VI lesion. RF positive cases had milder renal lesions.

Psychiatric disorder in essential dyspepsia

We wanted to examine the prevalence of psychiatric morbidity in patients diagnosed as having essential dyspepsia, as well as the short-term course of dyspeptic symptoms, following drug treatment of the psychiatric condition. Seventy-four patients with essential dyspepsia presenting to the gastroenterology outpatient department of a medical college were investigated for the presence of psychiatric disorder. The response to an open trial of pharmacotherapy in 50 patients with a psychiatric disorder and no other demonstrable pathology was assessed. These patients met the criteria for a DSM-III-R diagnosis, most commonly major depressive disorder (26) or generalized anxiety disorder (10). The mean age of those with a psychiatric disorder alone was significantly higher than that of those with another demonstrable pathology. With treatment, 16 patients with no demonstrable pathology other than psychiatric disorder (depression: 12; anxiety: 4) showed improvement over a period of 6 weeks in psychiatric as well as dyspepsia ratings. The difference was however statistically significant only for the group with major depressive disorder. We concluded that, despite differences in the characteristics of the population studied, a psychiatric diagnosis is associated with at least a proportion of cases with essential dyspepsia and emerges as a likely explanation.

Bishnupur achromats and their relatives (an exploratory study with six colour vision tests)

Thirteen subjects from the 'Sankhabaniks' of Bishnupur and two new similar cases were given six colour vision tests. All had photophobia, fixation nystagmus, low visual acuity and marked, though not complete, loss of colour sense. Forty other males and 24 females related to the defectives were also tested with at least five of the tests, for comparison. The tests were Ishihara, HRR test, Sloan's Achromatopsia test, the Dichotomous (D 15) test, Hundred Hue test and the Pickford-Nicolson Anomaloscope. The present research confirmed the provisional conclusion of Bose et al. (1968) that the achromatopsia in Bishnupur is an autosomal recessive character. That women relatives of the achromats showed greater average error scores with the Dichotomous test, the Hundred Hue test and the Sloan's test than male relatives, suggests that the defect is more readily manifested in males, and that the female relatives would include a number of genetic defectives with incomplete manifestation due to sex control. The defectives were clearly distinguished from the relatives as a group.