Improvement of Magnetic Saturation in Fe3O4@Y2O3:Eu3+ Nanocomposites Through the Manipulation of Eu3+ Activators.

Fe3O4@Y2O3:Eu3+ nanocomposites and Y2O3:Eu3+ nanophosphors were synthesized using the hydrothermal method. Nanocomposites were analyzed using X-ray diffraction (XRD), Rietveld refinements, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, photoluminescence (PL), vibrating sample magnetometer (VSM), and high-resolution transmission electron microscopy (HRTEM). Nanocomposites exhibit superparamagnetic behavior that improves with Eu3+, resulting in increased magnetic saturation. In contrast to Y2O3:Eu3+ nanophosphors, the Fe3O4@Y2O3:Eu3+ nanocomposites display a distinctive characteristic whereby the photoluminescence intensity increases with a reduced concentration of Eu3+. The requirement of increasing the thickness of the Y2O3:Eu3+ outer layer to achieve improved light emission can be circumvented by solely manipulating the concentration of activators, without compromising the magnetic saturation of the nanocomposites. The luminescent and magnetic characteristics of Fe3O4@Y2O3:Eu3+ nanocomposites can be readily optimized using straightforward synthesis parameters, making them promising candidates for potential applications in theranostic medicine.

Tissue tropism of avian reoviruses is genetically determined.

Two genome segments, M2 and S1, were preferentially selected in reassortants isolated in Vero cells. Analysis with monoclonal antibodies (MAbs) against RAM-1 strain showed that the 39-kDa protein encoded by the genome segment S1 contained epitopes involved in neutralisation of virus infectivity for both Vero and chicken kidney (CK) cells. The 39-kDa protein appeared to have two major epitopes that are attachment sites for cell receptors, one interacting only with CK cell receptors and the other with both CK and Vero cell receptors but principally Vero cell receptors. These results suggest that the strain RAM-1 may have developed an epitope for Vero cell receptors owing to mutation in the S1 genome segment, but still retained the epitope responsible for infection of CK cells.

Association between the sigma C protein of avian reovirus and virus-induced fusion of cells.

Monoclonal antibodies (MAbs) against a 39 kDa (sigma C) protein of the avian reovirus RAM-1 strain inhibited virus-induced fusion of cells and the protein was expressed on the surface of infected cells. The fusion-inhibiting activity of the three MAbs reacting with the sigma C protein suggest two putative epitopes were involved: one epitope recognised by antibody 6H1 and involved in fusion of both Vero and CK cells and a second epitope recognised by antibody 1G1 involved in fusion of Vero cells but not CK cells. The activity of the MAb 6E2 was intermediate, suggesting it may have been located in an intermediate position between the two putative epitopes and inhibited fusion by steric hindrance.

Immune response to avian reovirus in chickens and protection against experimental infection.

OBJECTIVES: To assess the efficacy of the vaccination procedure and the effect of the transfer of maternal antibodies to progeny chickens on reovirus pathogenicity. DESIGN: To vaccinate chickens and challenge progeny chickens with high doses of homologous and heterologous viruses. PROCEDURE: High doses of reovirus strains RAM-1, 1091 and 724 were used to induce tenosynovitis lesions. High doses were produced by concentration of viruses grown in cell culture. Then similar doses of viruses were used to challenge immunised chickens progeny. RESULT: Vaccination of breeding hens with the RAM-1 strain of avian reovirus, which resulted in the passive transfer of neutralising antibody to progeny chickens, completely prevented the development of tenosynovitis in 80% of progeny chickens infected with the homologous virus. Even though multiple injections of hens resulted in broadening of the normal type-specificity of the neutralising antibody response against heterologous serotypes of avian reovirus, only marginal protection against strains of two heterologous serotypes of avian reovirus was obtained. CONCLUSIONS: A model for assessing the efficacy of vaccination against avian reovirus strains on clinical sign such as tenosynovitis was developed that overcome the normal low virulence of Australian strains of avian reovirus. Breeding hens can be immunised with Australian strain of avian reovirus with passive transfer of antibody via the yolk to the progeny chickens. Although the neutralising antibody response to three injections of inactivated virus decreased the specificity of the neutralising antibody response against antigenically heterologous strains of avian reovirus, the protective immunity appeared to retain type-specificity.

Type-specific antigenicity of avian reoviruses.

The type-specificity of the neutralizing activity in chicken antiserum to avian reoviruses was affected by the method of antiserum production. The neutralizing activity produced in response to virus infection had higher type-specificity than that produced by immunization with inactivated virus emulsified in adjuvant. By using reassortant viruses the induction of type-specific neutralizing activity was shown to be associated with the sigma C (sigmaC) virion protein. Antigenic classification of virus strains based on immunoprecipitation of the sigmaC protein by chicken antiserum was attempted and the results were similar to those obtained by reciprocal serum neutralization tests. One-way immunoprecipitation of the sigmaC protein by antisera to some heterologous viruses, similar to that reported in reciprocal neutralization tests, made it difficult to assign individual viruses to serogroups and showed that the type-specificity of the sigmaC protein was not absolute. The neutralization activity of monoclonal antibodies to the sigmaC protein of the RAM1 strain of avian reovirus suggested there were separate type- and group-specific antigenic domains on the sigmaC protein, and that the group-specific domains may be associated with the induction of antibody against heterologous viruses.

Avian reovirus proteins associated with neutralization of virus infectivity.

Monoclonal antibodies against two virion proteins of the RAM-1 strain of avian reovirus neutralized virus infectivity; antibody against a 124-kDa (lambda B) protein caused broadly specific neutralization and antibody against a 39-kDa (sigma C) protein caused neutralization of greater type-specificity. The neutralizing activity of the monoclonals also exhibited host cell specificity: antibodies against the lambda B protein inhibited virus infectivity in Vero cells and not chicken kidney cells; one monoclonal antibody against the sigma C protein neutralized virus in only chicken kidney cells, whereas two other monoclonals against the sigma C protein neutralized virus in both Vero and chicken kidney cells but had greater neutralizing activity in Vero cells.