Construção e caracterização de um recombinante do Alphaherpesvirus caprino 1 com deleção no gene da Timidina Kinase

Abstract

Caprine alphaherpesvirus 1 (CpHV-1) is a pathogen of goats distributed worldwide, associated with systemic infections and respiratory disease in kids and subclinical infection or reproductive disease and abortions in adult animals. The losses associated with CpHV-1 infection could be prevented by vaccination, however, commercial vaccines are not available. Thus, the present study aimed to construct and characterize a recombinant of the CpHV-1 with a deletion in the thymidine kinase (TK) gene for potential use in vaccines. A recombinant with a total deletion in the tk gene was constructed by homologous recombination, by replacing the tk with the enhanced green fluorescent protein (eGFP) gene for the selection of recombinants. In vitro characterization showed that the recombinant CpHV-1TK replicated to similar titers and produced plaques of similar size to the parental virus in cell cultures, demonstrating that the deletion of the tk gene did not affect the replicative ability of the virus in vitro. After intranasal inoculation of five kids per virus (107 TCID50), the parental virus replicated more efficiently and for a longer period of time than the recombinant virus. In addition, the parental virus produced moderate systemic and respiratory signs, whereas the kids inoculated with the recombinant virus remained healthy and seroconverted to lower titers. The administration of dexamethasone on days 35 to 39 post-infection (pi) did not result in viral excretion in nasal secretions, indicating the absence of viral reactivation. However, viral DNA was detected in the trigeminal ganglia of 4 animals from the parental group (4/5) and 3 animals from the recombinant group (3/5), euthanized at day 14 pDx, indicating that both viruses established latent infection. These results demonstrated that the recombinant CpHV-1TK shows an attenuated phenotype in kids compared to the parental virus and, thus, may be a suitable strain for use as a CpHV-1 vaccine.