Carrier-induced epitopic suppression, a major issue for future synthetic vaccines

Synthetic antigens have been shown, in experimental models, to induce protective immunity against a variety of pathogens. These studies have demonstrated that, due to their low immunogenicity, these synthetic antigens required conjugation to carrier molecules. Therefore, the choice of appropriate carriers for human immunization by future synthetic vaccines is a major issue. Tetanus toxoid is generally considered to be an effective potential carrier devoid of side-effects. However, the present study performed in mice with two synthetic vaccine models demonstrates that the immune response against the synthetic epitopes conjugated to tetanus toxoid can be suppressed by pre-existing immunity against this same carrier. Because most humans have been exposed to this antigen, this effect may have important implications for the development of synthetic vaccines.     

Carrier-induced epitopic suppression is initiated through clonal dominance

Injection of mice with an immunogenic dose of carrier followed by immunization with hapten-carrier conjugate selectively suppresses anti-hapten antibody response. Previous studies have proposed that this epitopic suppression is related to the induction of carrier-specific Ts cells which in turn could inhibit selectively anti-hapten response. In the present study, we propose that the epitopic suppression is in fact due to clonal dominance. Immunization with a carrier such as tetanus toxoid induces a clonal expansion of carrier-specific B cells, thus decreasing the probability of hapten-specific B cells to react with the Ag. Increasing the density of the TNP-hapten on the conjugate has totally prevented the induction of the epitopic suppression. Moreover, using low hapten-carrier concentrations to challenge carrier-primed mice has enhanced the induction of the suppression. Finally, priming hapten-specific B cells before carrier/hapten-carrier immunization has also abrogated the suppression. The results of these experiments support the view that epitopic suppression is induced through the expansion of the clones specific for the carrier epitopes and resulted from intra-molecular antigenic competition between hapten and carrier epitopes. Based on these findings a regulatory role is proposed for B cells, where through their capacity to process and present antigen, they would exercise a strong influence on the selection of immune responses.     

Colonization factors of diarrheagenicE. coli and their intestinal receptors

WhileEscherichia coli is common as a commensal organism in the distal ileum and colon, the presence of colonization factors (CF) on pathogenic strains ofE. coli facilitates attachment of the organism to intestinal receptor molecules in a species- and tissue-specific fashion. After the initial adherence, colonization occurs, and the involvement of additional virulence determinants leads to illness. EnterotoxigenicE. coli (ETEC) is the most extensively studied of the five categories ofE. coli that cause diarrheal disease, and has the greatest impact on health worldwide. ETEC can be isolated from domestic animals and humans. The biochemistry, genetics, epidemiology, antigenic characteristics, and cell and receptor binding properties of ETEC have been extensively described. Another major category, enteropathogenicE. coli (EPEC), has virulence mechanisms, primarily effacement and cytoskeletal rearrangement of intestinal brush borders, that are distinct from ETEC. An EPEC CF receptor has been purified and characterized as a sialidated transmembrane glycoprotein complex directly attached to actin, thereby associating CF-binding with host-cell response. Three, additional categories ofE. coli diarrheal disease, their colonization factors and their host cell receptors are discussed. It appears that biofilms exist in the intestine in a manner similar to oral bacterial biofilms, and thatE. coli is part of these biofilms as both commensals and pathogens.Abbreviations CF colonization factor - CFA Colonization Factor Antigen - CS coli-surface-associated antigen - EAggEC enteroaggregativeE. coli - ECDD E. coli diarrheal disease - EHEC enterohemorrhagicE. coli - EIEC enteroinvasiveE. coli - EPEC enteropathogenicE. coli - ETEC enterotoxigenicE. coli - Gal galactose - GalNAc N-acetyl galactosamine - LT heat-labile toxin - NeuAc N-acetyl neuraminic acid - PCF Putative colonization factor - RBC red blood cells - SLT Shiga-like toxin - ST heat-stable toxin     

Determination of acid α-naphthyl acetate esterase enzyme activity in peripheral blood leukocytes of gazelles (Gazella subgutturosa)

We examined gazelle peripheral blood leucocytes using the α-Naphthyl acetate esterase (ANAE) staining technique (pH 5.8). Our purpose was to determine the percentage of ANAE positive lymphocytes. The proportion of ANAE positive T-lymphocytes was 72%. T-lymphocytes showed an ANAE positive reaction, but eosinophilic granulocytes and monocytes also showed a positive reaction. By contrast, no reaction was detected in B-lymphocytes, neutrophil granulocytes or platelets. The reaction observed in T-lymphocytes was a red-brown coloration, usually 1–2 granules, but enough granules to fill the cytoplasm were detected rarely. As a result of ANAE enzyme staining, we concluded that the staining technique can be used as a cytochemical marker for gazelle T-lymphocytes.     

Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) is not invasive through Asia: It's been there all along

Oriental fruit fly, Bactrocera dorsalis (Hendel), is a highly polyphagous fruit fly which, in the last 15 years, has invaded (with or without establishment) Africa, Europe and North America. As a direct result of these invasions, there is increasing research interest in the invasion history and spread patterns of this fly. A statement being repeatedly used in the B. dorsalis invasion literature is that the species was first identified from Taiwan in 1912 and that it subsequently spread through South‐East and South Asia during the 20th century. This assumption is incorrect and stems from: (a) an incomplete knowledge of B. dorsalis taxonomic history; and (b) a confounding of first taxonomic record with first invasion record. Rather than being first detected in Taiwan in 1912, the first record of oriental fruit fly was from “East India” (India orientali) under the synonymous name of Musca ferruginea by Fabricius in 1794, and in the 1910s, it was known not only from Taiwan, but widely across tropical Asia with records from India, Burma, Bengal, Sri Lanka (as Ceylon), Singapore and Indonesia (multiple islands). The taxonomic literature is very clear that oriental fruit fly has not invaded the rest of Asia from Taiwan since 1912, and this error should not continue to be repeated in the literature.     

Species status and population structure of the Australian Eucalyptus pest Paropsis atomaria Olivier (Coleoptera: Chrysomelidae)

1 Paropsis atomaria Olivier represents an emergent pest of Eucalyptus plantations in Queensland and New South Wales, Australia. Most prior studies on the biology and control of P. atomaria have centred on populations from Canberra in the Australian Capital Territory, but the biological relationship between beetles from Canberra and those from up to 1500 km further north are unknown. 2 DNA markers were used to determine whether P. atomaria from Canberra are the same biological species as those from Eucalyptus forestry plantations in northern New South Wales and Queensland, where the beetle has become an important pest. Using the mitochondrial gene, cytochrome c oxidase I (COI), individuals collected from across the distribution of P. atomaria were investigated for haplotype diversity and levels of mitochondrial divergence. 3 Within P. atomaria, genetic distance averaged 0.5% across 23 unique haplotypes for 93 individuals, with an average of 14% difference between P. atomaria and the outgroup species, Paropsis obsoleta. Significant genetic structure was observed relative to geographical distribution, but not with respect to host plant species of origin. Greatest divergence was between the southern‐most sample site (Canberra) and northern sites in New South Wales and Queensland, indicating reduced gene flow between these regions. 4 Individuals from across eastern Australia belong to the same genetic species with population substructuring evident. Consequently, there is no evidence to suggest cryptic species complexes exist within the currently defined taxon. Continued implementation of control strategies for P. atomaria across its distribution is appropriate.     

Phosphoproteomic screening identifies Rab GTPases as novel downstream targets of PINK1

Mutations in the PTEN‐induced kinase 1 (PINK1) are causative of autosomal recessive Parkinson''s disease (PD). We have previously reported that PINK1 is activated by mitochondrial depolarisation and phosphorylates serine 65 (Ser⁶⁵) of the ubiquitin ligase Parkin and ubiquitin to stimulate Parkin E3 ligase activity. Here, we have employed quantitative phosphoproteomics to search for novel PINK1‐dependent phosphorylation targets in HEK (human embryonic kidney) 293 cells stimulated by mitochondrial depolarisation. This led to the identification of 14,213 phosphosites from 4,499 gene products. Whilst most phosphosites were unaffected, we strikingly observed three members of a sub‐family of Rab GTPases namely Rab8A, 8B and 13 that are all phosphorylated at the highly conserved residue of serine 111 (Ser¹¹¹) in response to PINK1 activation. Using phospho‐specific antibodies raised against Ser¹¹¹ of each of the Rabs, we demonstrate that Rab Ser¹¹¹ phosphorylation occurs specifically in response to PINK1 activation and is abolished in HeLa PINK1 knockout cells and mutant PINK1 PD patient‐derived fibroblasts stimulated by mitochondrial depolarisation. We provide evidence that Rab8A GTPase Ser¹¹¹ phosphorylation is not directly regulated by PINK1 in vitro and demonstrate in cells the time course of Ser¹¹¹ phosphorylation of Rab8A, 8B and 13 is markedly delayed compared to phosphorylation of Parkin at Ser⁶⁵. We further show mechanistically that phosphorylation at Ser¹¹¹ significantly impairs Rab8A activation by its cognate guanine nucleotide exchange factor (GEF), Rabin8 (by using the Ser111Glu phosphorylation mimic). These findings provide the first evidence that PINK1 is able to regulate the phosphorylation of Rab GTPases and indicate that monitoring phosphorylation of Rab8A/8B/13 at Ser¹¹¹ may represent novel biomarkers of PINK1 activity in vivo. Our findings also suggest that disruption of Rab GTPase‐mediated signalling may represent a major mechanism in the neurodegenerative cascade of Parkinson''s disease.     

Airway cellularity, lipid laden macrophages and microbiology of gastric juice and airways in children with reflux oesophagitis

Background and methods

Human metapneumovirus (hMPV) is a recently discovered respiratory virus associated with bronchiolitis, pneumonia, croup and exacerbations of asthma. Since respiratory viruses are frequently detected in patients with acute exacerbations of COPD (AE-COPD) it was our aim to investigate the frequency of hMPV detection in a prospective cohort of hospitalized patients with AE-COPD compared to patients with stable COPD and to smokers without by means of quantitative real-time RT-PCR.

Results

We analysed nasal lavage and induced sputum of 130 patients with AE-COPD, 65 patients with stable COPD and 34 smokers without COPD. HMPV was detected in 3/130 (2.3%) AE-COPD patients with a mean of 6.5 × 10⁵ viral copies/ml in nasal lavage and 1.88 × 10⁵ viral copies/ml in induced sputum. It was not found in patients with stable COPD or smokers without COPD.

Conclusion

HMPV is only found in a very small number of patients with AE-COPD. However it should be considered as a further possible viral trigger of AE-COPD because asymptomatic carriage is unlikely.