EVALUATION OF PATOGENICITY OF SEVERAL ARGENTINE EQUINE HERPESVIRUS-1 STRAIN USING AN EXPERIMENTAL MODEL.

MARTÍN OCAMPOS, GP; BARBEITO CG, EÖRY ML, SIMIOLI G, FUENTEALBA NA, CID DE LA PAZ V, GIMENO EJ, GALOSI CM

Aguas de Lindoia Brasil

Congreso; XIV ENAPAVE Encuentro de Patologia Veterinaria; 2009

Associao Brasileira de Patologia Veterinaria

Equine herpesvirus 1 (EHV-1) is one of the most prevalent viruses affecting equine populations worldwide. Infection with EHV-1 may result in rhinopneumonitis, neurological syndromes, abortion and neonatal disease. Working with horses is expensive and labor-intensive for that reason the development of a mouse model has successfully been useful for investigate the pathogenesis and immune responses of the EHV-1 infection. In this work, the virulence of 22 Argentine EHV-1 strains was evaluated studying the effect of viruses on lung and uterus of infected pregnant BALB/C mice. Six female mice of 8-9 days of pregnancy were intranasally infected with 100ul of each strain (106.5DICT50%/50ìl) under light anaesthesia. Six mice in the same pregnancy time served as uninfected controls. General condition and the presence of obvious clinical signs were recorder. The mice were sacrificed at 48 h posinfection (pi). Blood with heparine was collected for DNA detection by PCR and viral isolation (VI). Samples of lungs, uterus and placenta were used for histology. Some sections were processed for lectin and immunohistochemistry (IHC) techniques. The mice inoculated began to show signs of illness such as ruffled fur, hunched posture, depression and irregularities in breathing from 24 h pi. The blood samples resulted negative for DNA detection by PCR and VI. Histological evidences of infection in HE stained sections were found. Inflammatory infiltrate of the lungs and loss of the normal alveolar architecture indicative of acute inflammation were observed. The lesions included desquamation and necrosis of bronchiolar and alveolar epithelia and eosinophylic intranuclear inclusion bodies. The IHC was positive in areas of the apical region of the bronchiolar epithelium. The histological changes in uterus were heterogeneous and included mild or severe endometritis with congestion, edema, and polymorphonuclear and mononuclear cells. Some animals showed no detectable alterations. The more evident lesions were found with AR2, AR3 and AR8 strains. The uteri of mice inoculated with AR2 had many apoptotic cells in connective tissue and luminal and glandular epithelium. In some samples numerous macrophages, polimorphonuclear infiltration and necrotic foci were found. AR3 generated apoptosis and inflammation in uterus but not affected the extraembrionary membranes. Mice inoculated with A8 shown embryonic resortion and neutrophilic infiltrate. To analyze the intervention of mast and granular glandular metrial (GMG) cells in the pathogenesis of the herpesvirosis we selectionated AR2 (very pathogenic) and AR5 (Light pathogenic) strains. , The GMG were identified using PAS and lectinhistochemistry with DBA. These cells were observed only in pregnancy and could not found in the AR2 inoculated animals because all animals aborted. In the AR5 inoculated the number of GMGs was similar to the found in controls. The mast cells were identified with Giemsa and IHC anti-c-kit. The numbers of mast cells was similar in mesometrium and miometrium of all groups. This work demonstrate that different EHV-1 strains are pathogen for pregnancy mice, although the intensity of the lesions is dependent of the strains. In this preliminary study mast cells and GMG apparently not participate in the pathogenic mechanisms of the placental and embryonic lesions