Canine parvovirus (CPV) is a major pathogen in canines, with a high mortality rate in unvaccinated puppies. CPV is traditionally classified into three antigenic variants (CPV-2a, CPV-2b and CPV-2c) based on the amino acid sequence of the VP2 protein. Currently, various mutations are described in the receptor-binding area or in the regions of greatest antigenicity of the VP2 protein, giving rise to new viral variants that are capable of immunological escape, affecting the protective immunity of traditional vaccines. In the present study, a molecular characterization of the VP2 gene was performed, which included phylogenetic analysis, amino acid characterization and determination of selection pressures. Blood samples were initially collected from canine patients with clinical signs of gastrointestinal infection, of which 69 were positive for CPV as measured by means of PCR and 18 samples were selected for the amplification of the complete VP2 gene. The analysis revealed a higher rate of CPV-2c-positive patients compared to CPV-2b. Furthermore, the amino acid characterization of VP2 indicated mutations in the regions of highest antigenicity previously described in the literature (CPV-2b: 297 and 324; CPV-2c: 440), as well as others not previously documented (CPV-2b: 514; CPV-2c: 188, 322, 379, 427 and 463). Our analysis of selection pressure showed that the VP2 gene is under negative selection. However, positive selection point sites were identified, both in CPV-2c (324, 426 and 440) and CPV-2b (297 and 324), at sites that have been associated with evasion of the immune response via antigenic drift, which possibly has implications for the protective immunity generated by traditional vaccines.

Canine immunocastration development has been of interest for many years as a complementary strategy to surgical castration. The purpose of this paper was to verify the effect of a recombinant vaccine for dog immunocastration. Two tests were done, one under controlled conditions and a second under field conditions. Animals were injected with 1 mL of 500 µg GnRXG/Q recombinant protein; 500 µg of low molecular weight chitosan as adjuvant; 1 mL NaCl 0.9% q.s. In the first trial, eight Beagle male dogs between the ages of 1 and 3 comprised the sample, randomly divided into two groups: vaccinated group (n = 7) and control group (n = 2). The second trial had 32 dogs with owners. In the first controlled conditions trial, the vaccine produced specific antibodies that remained until the end of the trial (day 270), inducing reduced testosterone and spermiogram changes in the immunized animals. In a second trial, on the field, specific immunity was induced, which remained high up to day 150. The vaccine also reduced sexual agonistic and marking behaviors. This new vaccine proved to be safe, immunogenic, capable of reducing gonadal functionality, and had a positive effect on inducing reduced sexual, agonistic, and marking behavior of the animals.