Incidence and isolation of bluetongue virus infection in cattle of the Santo Tomé Department, Corrientes Province, Argentina

Sentinel herds were monitored for the detection of bluetongue (BT)-specific antibodies and virus over two periods, namely: June 1999 to August 2000 and September 2000 to April 2001. Herds were located in Santo Tomé (Herds 1 and 2) where BTV activity was known to occur. From June 1999 to August 2000, the cumulative incidence (CI) of bluetongue virus (BTV) infection was 0% and 35% in Herds 1 and 2, respectively. In the second period, the CI of BTV infection was 10% and 97% in Herds 1 and 2, respectively. The virus was isolated from red blood cells of animals that seroconverted and was identified as serotype 4. Averages of the monthly maximal temperatures were always above 19 degrees C. However, averages of the monthly median temperatures were below 19 degrees C and averages of the monthly minimal temperatures were below 15 degrees C from May 2000 to August 2000. There was no viral activity detected at that time. Culicoides insignis was identified as the predominant potential vector species (99%) trapped near sentinel herds. Although clinical disease has never been reported in Argentina, viral activity was detected and the virus has been isolated in sentinel herds.

Gene expression profile in Neisseria meningitidis and Neisseria lactamica upon host-cell contact: from basic research to vaccine development

Differential gene regulation in the human pathogen Neisseria meningitidis group B (MenB) and in Neisseria lactamica, a human commensal species, was studied by whole genome microarray after bacterial interaction with epithelial cells. Host-cell contact induced changes in the expression of 347 and 285 genes in MenB and N. lactamica, respectively. Of these, only 167 were common to MenB and N. lactamica, suggesting that a different subset of genes is activated by pathogens and commensals. Change in gene expression was stable over time in N. lactamica, but short-lived in MenB. A large part (greater than 30%) of the regulated genes encoded proteins with unknown function. Among the known genes, those coding for pili, capsule, protein synthesis, nucleotide synthesis, cell wall metabolism, ATP synthesis, and protein folding were down-regulated in MenB. Transporters for iron, chloride and sulfate, some known virulence factors, GAPDH and the entire pathway of selenocysteine biosynthesis were upregulated. Gene expression profiling indicates that approximately 40% of the regulated genes encode putative surface-associated proteins, suggesting that upon cell contact Neisseria undergoes substantial surface remodeling. This was confirmed by FACS analysis of adhering bacteria using mouse sera against a subset of recombinant proteins. Finally, a few surface-located, adhesion-activated antigens were capable of inducing bactericidal antibodies, indicating that microarray technology can be exploited for the identification of new vaccine candidates.

Serum leptin levels are not influenced by arginine and insulin infusion and by acute changes of GH

The aim of this study was to evaluate the relationship between GH and leptin in a group of short children and adolescents. Leptin and GH serum levels were measured before and during pharmacological stimulation tests (arginine and insulin) in a group of 45 children (30 male, 15 female), mean age 8.6+/-3.9 yr, affected by idiopathic isolated GH deficiency (GHD), and in a group of 27 children (15 male, 12 female), age 10.9+/-3.3 yr, with constitutional growth delay. Results showed that basal and peak leptin levels as well as the AUC were significantly higher in GHD patients compared to controls (p<0.05) and correlated with BMI SDS (p<0.0001) in GHD patients. No change in leptin serum levels was observed during either stimulation test. No correlation was found, however, between basal leptin serum levels and basal, peak and the AUC of GH during the tests. Moreover, no correlation was found between the acute changes of serum GH concentration during both stimulation tests and leptin serum levels. The results suggest that leptin and GH secretion is not correlated and that leptin serum levels mainly reflect the amount of fat tissue, which is higher in GHD patients.

The level of bioavailable growth hormone (GH) after the first GH injection predicts the first year's growth response in GH-deficient children

Serum GH levels were measured in 9 prepubertal children with growth hormone (GH) deficiency using an immunofluorometric assay (IFMA) and a Nb2 cell bioassay, prior to and 2, 4, 6 and 12 hours after the first hGH subcutaneous injection (sc) (0.1 IU/Kg). After this first acute phase, hGH treatment was continued regularly at a dose of 0.1 IU/kg per day at bedtime. The acute pharmacokinetic profile was similar in the patients irrespectively of the assay used: serum GH usually starts to rise after 2 hours, peaks by 4 or 6 hours and drops back to near baseline levels 12 hours after s.c. GH administration. A great variation in the amplitude of peak levels was observed among the patients. The assays significantly (p<0.0001) correlate with each other in all subjects. An increase in serum GH values as evaluated by the Nb2 bioassay was observed in most children after s.c. GH injection, suggesting that the administered hormone preserves its biological activity. The individual variations in GH bioactivity in our GH-deficient children could be due to different mechanisms of the drug's degradation at the site of injection or in circulation. Pre-treatment height velocity calculated as standard deviation scores (SDS) significantly increased (p<0.001) from -2.77+/-0.42 to 1.22+/-0.87 SDS after a 12-month period of GH treatment in 8 patients who had already completed the first year of therapy, although it varied considerably among subjects. A higher serum GH peak value evaluated by both assays corresponded to a higher growth response during the 1st year, but not in the 2nd year of GH therapy. In conclusion, the degree of GH bioactivity released into circulation after sc GH injection may vary considerably among GHD patients and correlates with the growth response observed during the 1st year of GH therapy.

Multi-plasmid DNA vaccination avoids antigenic competition and enhances immunogenicity of a poorly immunogenic plasmid

DNA immunization is a very promising approach to the formulation of multivalent vaccines. However, little information is currently available on the immunogenicity of multi-plasmid formulations. To address this issue, we immunized mice with a combination of four plasmids encoding malarial antigens and we compared antibody responses with those obtained with single-plasmid injections. We found that when four plasmids encoding Plasmodium falciparum circumsporozoite protein, thrombospondin-related anonymous protein, major merozoite surface protein (MSP)1 and Pfs25 are co-injected into mice, Ab responses against each antigen are elicited at levels at least as high as the level obtained with single-plasmid injection. The quality of antibody production, as determined by isotype analysis, was similar when single- and multi-plasmid administrations were compared, indicating the priming of the same cytokine profile for CD4+ T helper cells. The sera from mice immunized with the four-plasmid formulation specifically recognized sporozoites, blood stage schizonts and gametes, indicating that DNA immunization induced antibody responses relevant to the native conformation. Finally and of particular interest, in the case of MSP1, the antibody response appears to be strongly potentiated by the presence of additional plasmids, indicating an adjuvant effect of DNA.