Fetal and neonatal exposure to the mycotoxin zearalenone induces phenotypic alterations in adult rat mammary gland.

Zearalenone is a mycotoxin that is widespread in cereal food. We questioned whether this mycotoxin, administered during known critical exposure periods such as the fetal period and the first days of life, at doses compatible with mean daily intake in humans, could have an effect on mammary gland development in rodents. Wistar female rats were exposed to zearalenone (0.2 µg/kg to 5mg/kg) during the last 14 days of fetal life and the first 5 post-natal days (PND). The mammary tissue was examined for development and maturation by morphologic analyses and immunochemistry. At PND 30, the mean length of terminal buds was significantly enhanced in all of the zearalenone-exposed females (p<0.05). The mammary tissue, as evaluated by scoring of tissue slides, was significantly more differentiated in the 1mg/kg treated group than in controls (p<0.05). At PND 180, mammary tissue was more differentiated in all of the zearalenone treated groups (p<0.05). At six months, 4 of 18 females exposed to 5mg/kg of zearalenone presented mammary hyperplasia lesions. The induction of phenotypic alterations by zearalenone administered in utero and in the neonatal period at doses as low as 0.2 µg/kg suggests that zearalenone could contribute to the induction of breast endocrine disorders.

Clearance of a productive lentivirus infection in calves experimentally inoculated with caprine arthritis-encephalitis virus.

Lentiviruses have long been considered host-specific pathogens, but several recent observations demonstrated their capacity to conquer new hosts from different species, genera, and families. From these cross-species infections emerged new animal and human infectious diseases. The successful colonization and adaptation of a lentivirus to a nonnatural host depends on unspecific and specific host barriers. Some of those barriers exert a relative control of viral replication (i.e., cytotoxic T-lymphocyte response, viral inhibitory factors), but none of them was found able to totally clear the infection once the retrovirus is fully adapted in its host. In this study we examined the evolution of the host-lentivirus interactions occurring in an experimental animal model of cross-species infection in order to analyze the efficiency of those barriers in preventing the establishment of a persistent infection. Five newborn calves were inoculated with caprine arthritis-encephalitis virus (CAEV), and the evolution of infection was studied for more than 12 months. All the animals seroconverted in the first 0.75 to 1 month following the inoculation and remained seropositive for the remaining time of the experiment. Viral infection was productive during 4 months with isolation of replication competent virus from the blood cells and organs of the early euthanized animals. After 4 months of infection, neither replication-competent virus nor virus genome could be detected in blood cells or in the classical target organs, even after an experimental immunosuppression. No evidence of in vitro restriction of CAEV replication was observed in cells from tissues explanted from organs of these calves. These data provide the demonstration of a natural clearance of lentivirus infection following experimental inoculation of a nonnatural host, enabling perspectives of development of new potential vaccine strategies to fight against lentivirus infections.

Specific G2 arrest of caprine cells infected with a caprine arthritis encephalitis virus expressing vpr and vpx genes from simian immunodeficiency virus.

Primate lentivirus (HIV and SIV) vpr accessory genes encode 12- to 14-kDa proteins which induce cell cycle arrest at the G2 phase of infected cells, preventing them from going through mitosis. Members of the HIV-2/SIVmac/SIVsmm group also encode a second closely related accessory protein called Vpx. Vpx and HIV Vpr are critical for virus replication in nondividing cells due to their participation in nuclear import of the preintegration complex. Caprine arthritis encephalitis virus (CAEV) and maedi visna virus are the natural lentiviruses of domestic goat and sheep, respectively, and their genomes do not carry vpr and vpx genes. In this study, we generated chimeric CAEV-based genomes carrying vpr and vpx genes from SIVmac239 and tested their ability to induce G2 cell cycle arrest in infected caprine cells. CAEV-pBSCAvpxvpr is the chimeric genome that was shown to be infectious and replication competent. Our data demonstrated that CAEV-pBSCAvpxvpr-infected goat synovial membrane cell monolayer developed more cytopathic effects and a high proportion of cells remained in the G2 phase of cell cycle. This G2 arrest was observed both at the early and at the late stages of infection, while minimal effect was observed with the parental CAEV-pBSCA. These results, described for the first time in mammalian cells other than those of primates, indicate that Vpr-induced G2 cell cycle arrest is not restricted to only primate cells. Thus, conservation of Vpx/Vpr protein functions in caprine cells suggests a possible role for these proteins in the virus life cycle and its ability to adapt to new hosts. The data presented here thus raise a pertinent question about the biological significance of the conservation of Vpr and Vpx functions in caprine cells despite the high phylogenic distance between primates and small ruminants.