Magnetic phase diagram of clathrate compound Ce3Pd20Si6 with quadrupolar ordering.

We present results of specific heat measurements on a Ce3Pd20Si6 single crystal and construct the magnetic phase diagram for the three cubic principal directions [100], [110] and [111]. The highly anisotropic phase diagram is discussed and can be qualitatively explained by the Zeeman splitting at the 8c-site. For B â€– [100], the present study found two different quadrupolar ordered phases, which meet the paramagnetic phase at a tri-critical point and establish the new phase boundaries.

An approach to a cold chain free oral cholera vaccine: in vitro and in vivo characterization of Vibrio cholerae gastro-resistant microparticles.

The present work describes the formulation of Eudragit(®) L30 D-55 microparticles (MP) alone or with mucoadhesive agents, alginate or Carbopol(®), as an approach for the development of an oral cholera vaccine. In the first part, a spray drying technique was optimized for microparticle elaboration, obtaining a microparticle size ranging from 7 to 9 µm with high encapsulation efficiencies. Moreover, gastro resistant properties and Vibrio cholerae (VC) antigenicity were maintained, but for Eudragit(®)-Carbopol(®) microparticles which showed low antigenicity values, ≈25%. Next, a stability study was performed following ICH Q1 A (R2) guidelines, i.e. 25°C-60% relative humidity (RH) for 12 months, and 30°C-65% RH and 40°C-75% RH for 6 months. Upon storage, microparticle size changed slightly, 1 µm for Eudragit(®)-alginate MPs and 0.36 µm for Eudragit(®)MP. However, gastro resistance and antigenicity values were kept in an acceptance range. In the third stage of this work, in vivo experiments were performed. The immune response evoked was measured by means of vibriocidal titer quantification, observing that Eudragit(®)-alginate MPs were able to induce stronger immune responses, comparable to the free VC. Therefore, microencapsulation of VC by spray drying could be proposed as an approach to a cold chain free and effective oral cholera vaccine.

Formulation in tablets of a cholera whole cells inactivated vaccine candidate.

Licensed as well as candidate cholera vaccines available at the present requires the dose preparation (included buffer) at the moment of application. The aim of this work was to evaluate the presentation in oral tablets of an inactivated cholera vaccine to avoid that inconveniences during application. We have therefore compared inactivated cultures of Vibrio cholerae with tablets formulation vaccine. We obtained that antigenic activity (ELISA) and immunogenicity in animal model (ELISA and vibriocidal tests) of V. cholerae inactivated cell remained unaltered in the final tablet formulation. The results suggest that the oral tablet formulation could be a useful pharmaceutical form in order to produce a new and affordable cholera vaccine.

Process development for a Cuban cholera vaccine based on the attenuated strain Vibrio cholerae 638.

Genetically modified Vibrio cholerae strain 638 (biotype El Tor, serotype Ogawa) has previously been shown to be immunogenic in animal models and in human trials. Our objective in the work reported herein was to describe the process development methods for the production of the 638 attenuated cholera vaccine. Cell seed bank, culture of biomass, lyophilization and final formulation were processes were developed. The results show kinetics of culture that fulfils a logistical model. The microbiological properties, colonizing capability, immunogenicity and non-toxigenicity of the final product were indistinguishable from the properties of the working seed lot. We conclude that the non-reactogenic, immunogenic and protective strain 638 is robust and can withstand the fermentation processes required for large-scale production of a vaccine.

Passive protection of serum from volunteers inoculated with attenuated strain 638 of Vibrio cholerae O1 in animal models.

As part of the studies to obtain an oral vaccine against cholera disease, the protective effect of serum from volunteers inoculated in a controlled trial with a candidate live attenuated vaccine of Vibrio cholerae O1, El Tor Ogawa (638; CTXφ mutant, hap::celA), was tested. It was confirmed that the serum, as well as the purified IgG and IgA from the volunteers had a protective effect in both of the animal models used, although the purified antibodies needed the presence of complement to be protective. These results emphasize the expectations about the protective potential of the candidate in challenge studies in humans to be conducted very soon.

Occurrence of a Strain of Potato Yellow Mosaic Geminivirus Infecting Tomato in the Eastern Caribbean.

Viruslike symptoms were observed in epidemic proportions in tomato, Lycopersicon esculentum Mill., in Guadeloupe and Martinique each year since 1992 and 1993, respectively, and in Puerto Rico since 1994 (1,3). Many tomato fields in Guadeloupe and Martinique had more than 70% of plants expressing symptoms of chlorotic mottling, leaf distortion, leaf rolling, and stunting in 1995 and 1996. The B biotype of Bemisia tabaci (aka B. argentifolii) was associated with all these epidemics. Ninety-three samples of tomato were collected from multiple locations from each island (65 samples from Guadeloupe, 11 from Martinique, and 17 from Puerto Rico) and assayed for the presence of geminivirus by polymerase chain reaction (PCR) with broad spectrum primers, PAL1v1978 and PAR1c496 for the A component, and PBL1v2040 and PCRc154 for the B component (4). Most samples tested positive for geminivirus (98% from Guadeloupe, 100% from Martinique, and 82% from Puerto Rico). Restriction analyses of amplified A component fragment with SacI, EcoRI, and AluI, and amplified B component fragment with EcoRI, AluI, VspI, PstI, and HaeIII were conducted on 34 samples (25 from Guadeloupe, six from Martinique, and three from Puerto Rico). All samples produced very similar restriction patterns, suggesting that they were infected by the same virus. One to three clones of amplified fragments of A and B components, obtained from one plant sample from each location, were at least 98.7% identical in sequence to each other and were 89.6% and 75.2 to 75.7% identical to equivalent regions in potato yellow mosaic virus (PYMV) A and B DNA, respectively (GenBank accession nos. D00940 and D00941). This isolate of PYMV was collected from potato in Venezuela in 1985 (2). Infectious full-length genomic clones of A and B component DNA from Guadeloupe were derived from the same tissue as the PCR-generated clones, and nucleotide sequences were found to be 99.1 and 99% identical to the PCR-generated fragments of A and B DNA, respectively. Nucleotide sequences of these full-length clones were 92.6 and 89.4% identical to full-length sequences of PYMV A and B DNA, respectively. The DNA sequence identity of the common regions of the A and B components between the Guadeloupe virus and PYMV was 95.1 and 91.6%, respectively. There was a nucleotide identity of 93% in the first 125 nucleotides of the coat protein gene. The virus found in Guadeloupe, Martinique, and Puerto Rico appears to be a strain of PYMV reported from Venezuela. This strain of PYMV is at least partially responsible for the epidemics in tomato in Guadeloupe, Martinique, and Puerto Rico. The similarity among geminivirus sequences at distant locations (Puerto Rico to Martinique is approximately 600 km) is unexpected and could be due to recent introductions. References: (1) J. K. Brown et al. Plant Dis. 79:1250, 1995. (2) R. H. A. Coutts et al. J. Gen. Virol. 72:1515, 1991. (3) B. Hostachy et al. Phytoma 456:24, 1993. (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.