Neuropathology and pathogenesis of HIV encephalopathies

The nervous system is frequently affected in patients with the acquired immune deficiency syndrome (AIDS). In addition to opportunistic CNS infections and cerebral lymphomas, approx. 20% of the patients develop HIV-associated encephalopathies. Two major histopathological manifestations are observed. HIV leukoencephalopathy (progressive diffuse leukoencephalopathy) is characterized by a diffuse loss of myelin in the deep white matter of the cerebral and cerebellar hemispheres, with scattered multinucleated giant cells and microglia but scarce or absent inflammatory reaction. HIV encephalitis (multinucleated giant cell encephalitis) is associated with accumulations of multinucleated giant cells, inflammatory reaction and often focal necroses. In some patients, both patterns may overlap. In order to identify the HIV genome in the CNS, brain tissue from 27 patients was analyzed for the presence of HIV gag sequences using the polymerase chain reaction (PCR) and primers encoding a 109 base pair segment of the gag gene. Amplification of HIV gag succeeded in all 5 patients with clinical and histopathological evidence for HIV encephalopathy but was negative in the 20 AIDS patients with opportunistic bacterial, parasitic and/or viral infections or with cerebral lymphomas. These results strongly suggest that the evolution of histopathologically recognizable HIV-encephalopathies closely correlates with the presence and/or tissue concentration of HIV. Since there were no cases with amplified HIV DNA in the absence of HIV-associated tissue lesions, we conclude that harboring and replication of HIV in the CNS rapidly causes corresponding clinical and morphological changes of HIV-associated encephalopathies. In two children with severe HIV encephalomyelitis, large amounts of HIV gag and env transcripts were detected in affected areas of the brain and spinal cord by in situ hybridization.(ABSTRACT TRUNCATED AT 250 WORDS)

HIV encephalopathy: incidence, definition and pathogenesis. Results of a Swiss collaborative study

The incidence of HIV encephalopathies was determined in an ongoing consecutive autopsy study. Among 345 patients who died from AIDS in Switzerland during 1981-1990, 68 (19%) showed morphological evidence of HIV encephalopathy. Two major histopathological manifestations were observed. Progressive diffuse leukoencephalopathy (PDL) was present in 33 cases and is characterized by a diffuse loss of myelin staining in the deep white matter of the cerebral and cerebellar hemispheres, with scattered multinucleated giant cells but little or no inflammatory reaction. Multinucleated giant cell encephalitis (MGCE) was diagnosed in 32 cases; it's hallmarks are accumulations of multinucleated giant cells with prominent inflammatory reaction and focal necroses. In 3 patients both types of lesions overlapped. Brain tissue from 27 patients was analyzed for the presence of HIV gag sequences using the polymerase chain reaction (PCR) with primers encoding a 109 base pair segment of the viral gene. Amplification succeeded in all patients with clinical and histopathological evidence for HIV encephalopathy but was absent in AIDS patients with opportunistic bacterial, parasitic and/or viral infections. Potential mechanisms by which HIV exerts it's adverse effects on the human CNS are discussed.

Genetic polymorphisms associated with the inflammatory response in bacterial meningitis.

BACKGROUND Bacterial meningitis (BM) is an infectious disease that results in high mortality and morbidity. Despite efficacious antibiotic therapy, neurological sequelae are often observed in patients after disease. Currently, the main challenge in BM treatment is to develop adjuvant therapies that reduce the occurrence of sequelae. In recent papers published by our group, we described the associations between the single nucleotide polymorphisms (SNPs) AADAT +401C > T, APEX1 Asn148Glu, OGG1 Ser326Cys and PARP1 Val762Ala and BM. In this study, we analyzed the associations between the SNPs TNF -308G > A, TNF -857C > T, IL-8 -251A > T and BM and investigated gene-gene interactions, including the SNPs that we published previously. METHODS The study was conducted with 54 BM patients and 110 healthy volunteers (as the control group). The genotypes were investigated via primer-introduced restriction analysis-polymerase chain reaction (PIRA-PCR) or polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) analysis. Allelic and genotypic frequencies were also associated with cytokine and chemokine levels, as measured with the x-MAP method, and cell counts. We analyzed gene-gene interactions among SNPs using the generalized multifactor dimensionality reduction (GMDR) method. RESULTS We did not find significant association between the SNPs TNF -857C > T and IL-8 -251A > T and the disease. However, a higher frequency of the variant allele TNF -308A was observed in the control group, associated with changes in cytokine levels compared to individuals with wild type genotypes, suggesting a possible protective role. In addition, combined inter-gene interaction analysis indicated a significant association between certain genotypes and BM, mainly involving the alleles APEX1 148Glu, IL8 -251 T and AADAT +401 T. These genotypic combinations were shown to affect cyto/chemokine levels and cell counts in CSF samples from BM patients. CONCLUSIONS In conclusion, this study revealed a significant association between genetic variability and altered inflammatory responses, involving important pathways that are activated during BM. This knowledge may be useful for a better understanding of BM pathogenesis and the development of new therapeutic approaches.

Staphylococcus aureus sortase mutants defective in the display of surface proteins and in the pathogenesis of animal infections

Many Gram-positive bacteria covalently tether their surface adhesins to the cell wall peptidoglycan. We find that surface proteins of Staphylococcus aureus are linked to the cell wall by sortase, an enzyme that cleaves polypeptides at a conserved LPXTG motif. S. aureus mutants lacking sortase fail to process and display surface proteins and are defective in the establishment of infections. Thus, the cell wall envelope of Gram-positive bacteria represents a surface organelle responsible for interactions with the host environment during the pathogenesis of bacterial infections.

Crossreactive recognition of viral, self, and bacterial peptide ligands by human class I-restricted cytotoxic T lymphocyte clonotypes: Implications for molecular mimicry in autoimmune disease

The immunodominant, CD8+ cytotoxic T lymphocyte (CTL) response to the HLA-B8-restricted peptide, RAKFKQLL, located in the Epstein–Barr virus immediate-early antigen, BZLF1, is characterized by a diverse T cell receptor (TCR) repertoire. Here, we show that this diversity can be partitioned on the basis of crossreactive cytotoxicity patterns involving the recognition of a self peptide—RSKFRQIV—located in a serine/threonine kinase and a bacterial peptide—RRKYKQII—located in Staphylococcus aureus replication initiation protein. Thus CTL clones that recognized the viral, self, and bacterial peptides expressed a highly restricted αβ TCR phenotype. The CTL clones that recognized viral and self peptides were more oligoclonal, whereas clones that strictly recognized the viral peptide displayed a diverse TCR profile. Interestingly, the self and bacterial peptides equally were substantially less effective than the cognate viral peptide in sensitizing target cell lysis, and also resulted only in a weak reactivation of memory CTLs in limiting dilution assays, whereas the cognate peptide was highly immunogenic. The described crossreactions show that human antiviral, CD8+ CTL responses can be shaped by peptide ligands derived from autoantigens and environmental bacterial antigens, thereby providing a firm structural basis for molecular mimicry involving class I-restricted CTLs in the pathogenesis of autoimmune disease.

Plants and animals share functionally common bacterial virulence factors

By exploiting the ability of Pseudomonas aeruginosa to infect a variety of vertebrate and nonvertebrate hosts, we have developed model systems that use plants and nematodes as adjuncts to mammalian models to help elucidate the molecular basis of P. aeruginosa pathogenesis. Our studies reveal a remarkable degree of conservation in the virulence mechanisms used by P. aeruginosa to infect hosts of divergent evolutionary origins.

Defining the Role of Host Cell Chromatin Traps in Chlamydia trachomatis Pathogenesis

Chlamydia trachomatis (CT) is the most common bacterial agent of sexually transmitted infection and can cause damaging inflammation of the female reproductive tract. As an obligate intracellular pathogen, CT must exit exhausted host cells in a manner that favors successful dissemination. Epithelial cells infected with CT expel decondensed nuclear chromatin at the conclusion of an infectious cycle, and these ensnare CT particles. Whether these chromatin traps benefit the host or the pathogen is not obvious. The overall goal of this work is to begin discerning between these possibilities by determining how chromatin traps impact CT survival following exit and how traps contribute to CT-induced inflammatory processes.

Bacterial diseases in marine bivalves

Bivalve aquaculture is seriously affected by many bacterial pathogens that cause high losses in hatcheries as well as in natural beds. A number of Vibrio species, but also members of the genera Nocardia and Roseovarius, are considered important pathogens in aquaculture. The present work provides an updated overview of main diseases and implicated bacterial species affecting bivalves. This review focuses on aetiological agents, their diversity and virulence factors, the diagnostic methods available as well as information on the dynamics of the host-parasite relationship.

Study of bacterial agents on external lesions of cultured Sturgeons in Sngar zone of Gilan Province

This study was carried out to isolate and determine bacterial agents in outer lesions of sturgeons in Shahid Dr. Beheshti sturgeon propagation and rearing center in Gilan province. Five species of sturgeons were studied from viewpoint of lesions. A number of 167 specimens of Beluga, 76 specimens of Persian sturgeon, 27 specimens of Russian sturgeon, 42 specimens of stellate and finally 23 specimens of ship had bacterial lesions in different outer parts of their bodies. After sampling and purification, bacterial cultures and biochemical tests were done. After the isolation of bacteria from lesions, Edwardsiella tarda was selected by means of PCR. To obtain molecular acceptance, a pair of E. tarda special primer, forward primer ETa2-351 and reverse primer (Edwsp-780r) were reproduced. A number of 12 E. tarda DNA sample were identified by PCR. After molecular diagnosis, Persian sturgeon challenged with E. tarda for determination of pathogenesis. Challenge method was done by means of injection of different dilutes of E. tarda into dorsal muscle. Sampling of hematopoietic organs (kidney, spleen and liver) were carried out and located in Boin's fixator to perform pathology survey. Also, in order to survey of existence and effect of E. tarda, sampling of kidney for bacterial culture was done by molecular and biochemical methods. Results showed that the most lesions in all five species belonged to abdominal surface. Skin and scutes of this part were involved in comparison with other parts. Also, It was removed some samples from lesions to pathological survey. Microscopic observations showed some levels of destruction of epidermis layers, necrosis of dermis cells and destruction of muscular layer of skin. On the other hand, invasion of inflammatory cells and haemorrhagic in dermis were clear. Based on biochemical results, Aeromonas sobria, A cavia . A. hydrophila , Acinetobacter lowffii , A.baumanni , A.cakoaceticus, Pseudomonas putida , P fluorescens , P.aeruginosa , Serratia marcescens , Escherichia coli , Enterobacter aerogenes , Edwardsiella tarda , Proteus mirabilis , kelebsiella oxytoca and Staphylococcus sp. were isolated from outer lesions. Results of PCR confirmed that E. tarda was before and after challenge in 200 bp range. LD50, 96h was determined 1.2 x 10^5 (CFU/ml). Pathological experiments showed lesions in the kidney, including hemorrhages, degeneration of glumeruli and tubular epithelia, degeneration and necrosis of interestitium tissue, accumulation of protein casts in the tubular lumen. It was observed haemorhages, engorged blood vessels, congestion of sinusoids, increased of melanine, melano macrophage centers, degeneration and necrosis of hepatocytes in the liver. In the spleen, it was recorded congestion, degeneration, necrosis changes in the white and red pulpa, blood engorged and detachment of ellipsoid wall.

Role of Aeromonas hydrophila in bacterial septicemia of cultured carps in Khouzestan Province and investigation on protectivity of bacterin (s) prepared from acute isolate(s) of it

Motile Aeromonas are the most common bacteria of freshwater in the world that cause disease in fish and other cold-blooded and warm-blooded hosts. Among this group of bacteria, Aeromonas hydrophila is important in causing complications such as fin rot, skin ulcers and lethal hemorrhagic septicemia in fish. Several virulence factors involved in the pathogenesis of Aeromonas hydrophila, including extracellular enzymes (protease, lipase, elastase, gelatinase and nuclease) and toxins. From the exotoxins, hemolysin, aerolysin and cytolytic enterotoxin play an important role in pathogenesis. Detection of virulence markers by PCR as a key component of determining the pathogenesis of the bacteria and using indigenous vaccines for better immunization against this disease is important. In this study, a total of 200 fanned carps (126 common carp. 39 silver carp and 35 of grass carp) with symptoms suspected aeromonas septicemia were isolated from Khouzestan province farms. 125 bacteria belong to Aeromonas genus detected by biochemical and PCR methods. 31 of all isolates recognized as Aeromonas hydrophila with biochemical methods, I6srRNA detection and Lipase genes. Results showed that the role of Aeromonas sp. and Aeromonas hydrophila in fish with disease symptoms were 62.5% and 15.5% respectively. By using specific primers, three virulence genes including hemolysin, aerolysine and cytolytic enterotoxin were detected in these confirmed isolates, that 18 isolates (58/06%) hemolysin positive (hlyA +), 16 isolates (51/61%) aerolysine positive (aerA+) and 23 isolates (74/19%) for cytolytic enterotoxin gene (act+) were positive. The result of present study showed that most of the confirmed isolates genotype was hlyA+ act- with frequency equal to 51/61%. For investigating the protection effect of acut strain of bacteria, UV inactivated bacterin was used.

Diet, microbes and gut immune responses in the pathogenesis of experimental type 1 diabetes

Type 1diabetes (T1D) is an autoimmune disease, which is influenced by a variety of environmental factors including diet and microbes. These factors affect the homeostasis and the immune system of the gut. This thesis explored the altered regulation of the immune system and the development of diabetes in non-obese diabetic (NOD) mice. Inflammation in the entire intestine of diabetes-prone NOD mice was studied using a novel ex-vivo imaging system of reactive oxygen and nitrogen species (RONS), in relation to two feeding regimens. In parallel, gut barrier integrity and intestinal T-cell activation were assessed. Extra-intestinal manifestations of inflammation and decreased barrier integrity were sought for by studying peritoneal leukocytes. In addition, the role of pectin and xylan as dietary factors involved in diabetes development in NOD mice was explored. NOD mice showed expression of RONS especially in the distal small intestine, which coincided with T-cell activation and increased permeability to macromolecules. The introduction of a casein hydrolysate (hydrolysed milk protein) diet reduced these phenomena, altered the gut microbiota and reduced the incidence of T1D. Extra-intestinally, macrophages appeared in large numbers in the peritoneum of NOD mice after weaning. Peritoneal macrophages (PM) expressed high levels of interleukin-1 receptor associated kinase M (IRAK-M), which was indicative of exposure to ligands of toll-like receptor 4 (TLR-4) such as bacterial lipopolysaccharide (LPS). Intraperitoneal LPS injections activated T cells in the pancreatic lymph nodes (PaLN) and thus, therefore potentially could activate islet-specific T cells. Addition of pectin and xylan to an otherwise diabetes-retarding semisynthetic diet affected microbial colonization of newly-weaned NOD mice, disturbed gut homeostasis and promoted diabetes development. These results help us to understand how diet and microbiota impact the regulation of the gut immune system in a way that might promote T1D in NOD mice.

Prevalence and occurrence of zoonotic bacterial pathogens in surface waters determined by quantitative PCR

The prevalence and concentrations of Campylobacter jejuni, Salmonella spp. and enterohaemorrhagic E. coli (EHEC) were investigated in surface waters in Brisbane, Australia using quantitative PCR (qPCR) based methodologies. Water samples were collected from Brisbane City Botanic Gardens (CBG) Pond, and two urban tidal creeks (i.e., Oxley Creek and Blunder Creek). Of the 32 water samples collected, 8 (25%), 1 (3%), 9 (28%), 14 (44%), and 15 (47%) were positive for C. jejuni mapA, Salmonella invA, EHEC O157 LPS, EHEC VT1, and EHEC VT2 genes, respectively. The presence/absence of the potential pathogens did not correlate with either E. coli or enterococci concentrations as determined by binary logistic regression. In conclusion, the high prevalence, and concentrations of potential zoonotic pathogens along with the concentrations of one or more fecal indicators in surface water samples indicate a poor level of microbial quality of surface water, and could represent a significant health risk to users. The results from the current study would provide valuable information to the water quality managers in terms of minimizing the risk from pathogens in surface waters.

Bacterial proteases from the intracellular vacuole niche ; protease conservation and adaptation for pathogenic advantage

Proteases with important roles for bacterial pathogens which specifically reside within intracellular vacuoles are frequently homologous to those which have important virulence functions for other bacteria. Research has identified that some of these conserved proteases have evolved specialised functions for intracellular vacuole residing bacteria. Unique proteases with pathogenic functions have also been described from Chlamydia, Mycobacteria, and Legionella. These findings suggest that there are further novel functions for proteases from these bacteria which remain to be described. This review summarises recent findings of novel protease functions from the intracellular human pathogenic bacteria which reside exclusively in vacuoles.