Ag-ELISA and PCR for monitoring the vaccination of cattle against Taenia saginata cysticercosis using an oncospheral adhesion protein (HP6) with surface and secreted localization.

A Taenia saginata oncosphere-derived adhesion protein (HP6) with surface and secreted localization was used to successfully vaccinate calves against oral challenge with T. saginata eggs. In contrast, vaccination using a combination of T. saginata oncosphere-derived peptides, selected on the basis of their antigenic index, and including three derived from the HP6 molecule (HP6-1, HP6-2 and HP6-3), was unsuccessful. This either indicated that the wrong peptides were selected or, in the case of the HP6 protein, that the protective epitope is conformational in nature. The protection experiments were monitored using a parasite antigen detection ELISA (HP10 Ag-ELISA), which allowed the early determination of the success of the vaccination protocol, subsequently confirmed at autopsy. PCR assays were used for the first time to confirm the presence of T. saginata DNA in lesions recovered at autopsy and thus verify the parasite origin of the lesions.

Taenia saginata derived synthetic peptides with potential for the diagnosis of bovine cysticercosis.

Immunity in Taeniids is predominantly antibody mediated and thus many serological immuno-determinants will have potential in both protection and diagnosis. The antigenicity of six peptides derived from four potentially protective molecules cloned from a Taenia saginata oncospheres cDNA library have been evaluated as targets for the specific diagnosis of bovine cysticercosis. The six peptides consist of: two peptides (HP6-2 and HP6-3) derived from the sequence of the 18 kDa surface/secreted oncospheral adhesion antigen identified by McAb-HP6, two peptides (Ts45W-1 and Ts45W-5) derived from the sequence of the T. saginata homologue of the T. ovis 45W protective gene family, one peptide (TS45S-10) derived from a T. saginata sequence with significant similarity to the T. ovis 45S protective antigen, and one peptide (TEG-1) derived from the sequence of the T. saginata homologue of Echinococcus spp. main surface protein. Longitudinal studies indicate that T. saginata infected cattle respond to all six peptides by 3-4 weeks post-infection and that the antibody levels remain high for at least 12 weeks post-infection. As protection against Taeniid parasites is predominantly antibody mediated, some of these six peptides may be of value as immuno-prophylactic tools and hence also in assays to determine resistance to infection with the parasite. For diagnosis, on the other hand, only three peptides (HP6-2, TEG-1 and Ts45S-10) performed with the necessary sensitivity and specificity to determine exposure to infection with T. saginata, and now merit an exhaustive evaluation prior to employment as routine diagnostic tools.

Serological evidence for recent exposure to Taenia solium in Venezuelan Amerindians.

This study examined the seroprevalence and serum antibody isotype profile for Taenia solium cysticercosis in an Amerindian community in the Amazonas state of Venezuela. An antigen-trapping enzyme-linked immunosorbent assay (Ag-ELISA) was used to detect viable cysticercosis. Indirect ELISA (Ab-ELISA) and enzyme-linked immunoelectrotransfer blot (EITB) was performed by using antigens prepared from T. solium metacestodes to detect anti-parasite antibodies. The Ag-ELISA and Ab-ELISAs revealed 64.7% and 79.0% seropositivity, respectively, in the Amerindian population. Immunoglobulin (Ig) M was the predominant antibody class, suggesting recent infection. In comparison sera from, clinically defined, hospital neurocysticercosis cases revealed only 27% seropositivity by Ag-ELISA, compared with 86-92% seropositivity by Ab-ELISA, and IgG4 was the predominant antibody subclass detected. The EITB antigen recognition patterns of the hospitalized patients were very similar to that of the Amerindians, confirming exposure to the parasite. These results, combined with the predominance of IgM antibody responses and the marked detection of secreted products of viable parasites, strongly suggest that recent exposure to T. solium had occurred in the Amerindian population.

Identification of the principal serological immunodeterminants of African swine fever virus by screening a virus cDNA library with antibody.

Protective immunity to African swine fever virus (ASFV) may involve a combination of both serological and cellular mechanisms. This work is focused on the identification of the possible relevant serological immunodeterminants of immunity. Thus, 14 serological immunodeterminants of ASFV have been characterized by exhaustive screening of a representative lambda phage cDNA expression library of the tissue culture-adapted Ba71V strain of ASFV. The library was constructed using RNA extracted from Vero cells infected for 3, 6, 9 and 12 h. A total of 150 clones was selected arbitrarily by antibody screening of the library with a polyclonal antiserum from a domestic pig surviving infection with the virulent Malta isolate of ASFV. Sequencing of these clones permitted identification of 14 independent viral proteins that stimulated an antibody response. These included six proteins encoded by previously unassigned open reading frames (ORFs) (B602L, C44L, CP312R, E184L, K145R and K205R) as well as some of the more well-studied structural (A104R, p10, p32, p54 and p73) and non-structural proteins (RNA reductase, DNA ligase and thymidine kinase). Immunogenicity of these proteins was confirmed by demonstrating the corresponding antibodies in sera from pigs infected either with the Malta isolate or with the OURT88/3-OURT88/1 isolate combination. Furthermore, the majority of these ORFs were also recognized by immune antiserum from the natural host, the bush pig, following secondary challenge with the virulent Malawi (SINT90/1) isolate of ASFV. Thus, it is possible that some of these determinants may be important in protection against virus infection.

Demonstration of bovine CD8+ T-cell responses to foot-and-mouth disease virus.

The aim of this study was to investigate the importance of cellular immunity in foot-and-mouth disease in cattle, in particular to determine whether a CD8+ T-cell response could be detected, as these cells may play a role in both immunity and virus persistence. As attempts to characterize classical cytotoxic T cells had yielded non-reproducible results, largely due to high backgrounds in control cultures, a proliferation assay was developed that was demonstrated to detect antigen-specific, MHC class I-restricted bovine CD8+ cells responding to foot-and-mouth disease virus (FMDV). Proliferative CD8+ T-cell responses were detected consistently from 10 to 14 days following infection with FMDV and typically lasted 3-4 weeks. The role of CD8+ T cells in control of the disease, in particular their relevance for the establishment of persistence, may now be investigated.

Anti-Thy-1 treated and irradiated spleen cells from (BALB/c x C57Bl/6) F1 mice infected with Plasmodium chabaudi chabaudi can transfer protection into irradiated hosts.

The transfer of spleen cells from (BALB/c x C57Bl/6) F1 mice recovered from a Plasmodium chabaudi chabaudi AS infection into irradiated syngeneic recipients conferred protection. Neither elimination of Thy-1+ cells nor in vitro irradiation of immune cells before transfer affected protection while both anti-Thy-1 treatment and irradiation abolished the appearance of anti-P. c. chabaudi antibodies in the recipients. Superinfection of immune spleen cell donors did not improve their capability to transfer protection which was also unaffected by anti-Thy-1 treatment. The serum of mice after one infection was only marginally protective when transferred into irradiated recipients and a second infection improved the protective activity of serum which was not further improved by six infections. The co-transfer of immune serum and immune cells did not result in any synergistic effect. On the other hand, when P. c. chabaudi AS (BALB/c x C57Bl/6) F1 infected mice were challenged with a high dose of Plasmodium yoelii 17XL at crisis, the mice were unable to control the heterologous parasite. When mice were challenged with P. yoelii 17XL several weeks after infection with P. c. chabaudi AS, a good degree of cross-protection was observed.