In vivo effect on pig chromosomes of high dosage vaccine against classic swine fever

Comparison of mitotic cell death by chromosome fragmentation to premature chromosome condensation

Mitotic cell death is an important form of cell death, particularly in cancer. Chromosome fragmentation is a major form of mitotic cell death which is identifiable during common cytogenetic analysis by its unique phenotype of progressively degraded chromosomes. This morphology however, can appear similar to the morphology of premature chromosome condensation (PCC) and thus, PCC has been at times confused with chromosome fragmentation. In this analysis the phenomena of chromosome fragmentation and PCC are reviewed and their similarities and differences are discussed in order to facilitate differentiation of the similar morphologies. Furthermore, chromosome pulverization, which has been used almost synonymously with PCC, is re-examined. Interestingly, many past reports of chromosome pulverization are identified here as chromosome fragmentation and not PCC. These reports describe broad ranging mechanisms of pulverization induction and agree with recent evidence showing chromosome fragmentation is a cellular response to stress. Finally, biological aspects of chromosome fragmentation are discussed, including its application as one form of non-clonal chromosome aberration (NCCA), the driving force of cancer evolution.

Marker vaccine strategies and candidate CSFV marker vaccines

Classical swine fever (CSF) is an economically important highly contagious disease of swine worldwide. Classical swine fever virus (CSFV) is its etiological agent, and the only natural hosts are domestic pigs and wild boars. Although field CSFV strains vary in the virulence, they all result in serious losses in pig industry. Highly virulent field strains generally cause acute disease and high mortality; moderately virulent field strains raise subacute or chronic infections; postnatal infection by low virulent field strains produces subclinical infection and mortality in the new-born piglets. CSFV can cross the placental barrier, and this transplacental transmission usually results in mortality of fetuses and birth of congenitally infected pigs with a late-onset disease and death. Two main strategies to control CSF epidemic are systematic prophylactic vaccination with live attenuated vaccines (such as C-strain) and non-vaccination stamping-out policy. But neither of them is satisfying enough. Marker vaccine and companion serological diagnostic test is thought to be a promising strategy for future control and eradication of CSF. During the past 15 years, various candidate marker vaccines were constructed and evaluated in the animal experiments, including recombinant chimeric vaccines, recombinant deletion vaccines, DNA vaccines, subunit vaccines and peptide vaccines. Among them, two subunit vaccines entered the large scale marker vaccine trial of EU in 1999. Although they failed to fulfil all the demands of the Scientific Veterinary Committee, they successfully induced solid immunity against CSFV in the vaccinated pigs. It can be expected that new potent marker vaccines might be commercially available and used in systematic prophylactic vaccination campaign or emergency vaccination in the next 15 years. Here, we summarized current strategies and candidate CSFV marker vaccines. These strategies and methods are also helpful for the development of new-generation vaccines against other diseases.

Determination of genotoxicity of classical swine fever vaccine in vitro by cytogenetic and comet tests

Chromosome damage in lymphocyte cultures induced by live virus vaccine against classical swine fever (CSF) has been observed in previous studies. In vivo cytogenetic tests were made with several doses of vaccines used in Argentina to control the disease. These studies have shown that genotoxic effects increased with dose. In the present study, two different in vitro assays were performed by recording the frequency of cells with chromosome alterations and by assessing the ability of the vaccine to damage DNA, using the single cell gel microelectrophoretic assay (comet test). Frequencies of cells with chromosomal alterations increased significantly when compared with controls and were dose (microl/ml) dependent: 0 = 1.23, 5 = 2.29, 10 = 5.42 and 20 = 11.71%. In the comet assay the variables measured, tail length (TL) and tail moment (TM), also increased. For control cultures TL was 2.32 microm, whereas with concentrations of 20 and 100 microl/ml TL were 12.47 and 42.3 microm, respectively. TM of control cultures was 0.18, whereas with vaccine concentrations of 20 and 100 microl/ml TM were 5.52 and 24.52, respectively. Comet frequency distributions differed significantly among treatments. These results agree with previous in vivo observations. Regarding CSF pathogeny, our results support a direct effect of CSF vaccinal virus on lymphocyte DNA. Genotoxicity of CSF vaccine was corroborated in vitro at the cytogenetic and molecular levels.