Apoptotic vesicles crossprime CD8 T cells and protect against tuberculosis

CD8 T lymphocytes are important effectors in protective immunity against Mycobacterium tuberculosis. We recently characterized the detour pathway of CD8 T cell activation in tuberculosis mediated by apoptotic vesicles from infected cells that transport mycobacterial antigens to dendritic cells (DCs). Here we demonstrate that apoptotic vesicles from mycobacteria-infected macrophages stimulate CD8 T cells in vivo. Homing of DCs to draining lymph nodes was critically required for effective crosspriming. Subsequent fate of vesicle-associated antigens in recipient DCs was characterized by endosomal mechanisms predominating over proteasomal processing. In addition, vesicle processing depended on the presence of saposins to disintegrate apoptotic membranes. Apoptotic vesicles displayed potent adjuvant activity by stimulating through Toll-like receptors (TLR). Ultimately, vaccination with vesicles from infected cells induced protection against M. tuberculosis infection. Taken together, we propose the detour pathway to represent a genuine immunological mechanism mediating crosspriming of CD8 T cells in vivo and protection against tuberculosis.     

Serogroup-reactive and type-specific detection of bluetongue virus antibodies using chicken scFvs in inhibition ELISAs

Two bluetongue virus (BTV) serotype 10-specific single-chain Fv chicken antibody fragments (scFvs) were evaluated in a competitive ELISA. The binding of one (F3) to purified BTV was only inhibited by antibodies against the homologous serotype. The binding of the other (F10) was blocked by antisera to each of the 24 BTV serotypes. F10 recognised VP7, a major structural protein of the BTV core, but not if the protein was directly adsorbed to a plastic surface. It did, however, bind to recombinant VP7 that had been captured from suspension by rabbit IgG. This made it possible to develop an scFv based inhibition ELISA for BTV antibodies using recombinant VP7 without prior purification. The resulting immunoassay detected antibodies to 24 BTV serotypes, but not those directed against three serotypes of the related epizootic haemorrhagic disease virus. A phage library displaying fusion peptides expressed by fragments of the BTV genome segment 7 cDNA was constructed and screened using F10. Comparing selected peptides with the amino acid sequence of VP7 showed that recognition by the scFv required at least 131 residues representing the protein's upper domain. By providing well-characterised immunological reagents, recombinant antibody technology can contribute to the development of improved immunoassays for BTV diagnosis.     

Azithromycin resistance and its molecular characteristics in Neisseria gonorrhoeae isolates from a tertiary care centre in North India

Treatment guidelines for management of uncomplicated gonorrhoeae have been recently modified owing to alarming upsurge in azithromycin resistance. This study investigated the prevalence and genetic determinants of gonococcal azithromycin resistance in India. Four (5.7%) of 70 gonococcal isolates were resistant to azithromycin. Of 16 isolates investigated for molecular mechanisms of resistance, 13 (81.3%) and 6 (37.5%) isolates exhibited mutations in coding and promoter regions of mtrR gene, respectively. However, ermA, ermB and ermC genes or mutations in rrl gene were absent in all isolates. Azithromycin resistance is low in India posing no immediate threat to use of dual-therapy for syndromic management.     

NADPH oxidase drives cytokine and neurotoxin release from microglia and macrophages in response to HIV-Tat

Previous reports have shown that the human immunodeficiency virus (HIV) regulatory protein Tat has both pro-oxidant and pro-inflammatory properties, suggesting that Tat might contribute to the neurological complications of HIV. However, the intracellular mechanisms whereby Tat triggers free radical production and inflammation, and the relationship between Tat-induced free radicals and inflammatory reactions, are still subject to debate. The present study was undertaken to evaluate the specific effects of Tat on NADPH oxidase in microglia and macrophages, and to determine the specific role of NADPH oxidase in Tat-induced cytokine/chemokine release and neurotoxicity. Application of Tat to microglia or macrophages caused dose- and time-dependent increases in superoxide formation that were prevented by both pharmacologic NADPH oxidase inhibitors and by specific decoy peptides (gp91ds). Furthermore, inhibition of NADPH oxidase attenuated Tat-induced release of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF), and monocyte chemoattractant protein 1 (MCP-1), and decreased microglial-mediated neurotoxicity. Finally, macrophages derived from NADPH oxidase-deficient mice displayed reduced superoxide production, released lower levels of cytokines/chemokines, and induced less neurotoxicity in response to Tat compared to wild-type macrophages. Together, these data describe a specific and biologically significant signaling component of the macrophage/microglial response to Tat, and suggest the neuropathology associated with HIV infection might originate in part with Tat-induced activation of NADPH oxidase.     

Cystic Mass in Interventricular Septum; A Rare Presentation of Sinus of Valsalva Aneurysm

A young male presented with progressively increasing breathlessness for one year. Echocardiography showed a cystic echolucent cavity in interventricular septum communicating with sinus of Valsalva. A diagnosis of unruptured aneurysm of Valsalva dissecting into the interventricular septum was made. This complication is extremely rare and early recognition may prevent a potential catastrophe. (Echocardiography 2010;27:E117‐E118)