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The aim of the present work was to clarify if a PCV2 subclinical infection could affect the development of specific immunity against an Aujeszky’s disease virus (ADV) vaccination. For this purpose, 21 two week–old conventional piglets, seropositive to PCV2 and negative to PCV2 PCR, were used. At six weeks of age, piglets were randomly distributed into four separated groups and were inoculated with PCV2 or placebo. Fourteen days later, pigs were vaccinated with a gE- tk- attenuated ADV vaccine (Bartha K61). Clinical course and weight gains (ADWG) were measured from 0 to 35 days post-inoculation (dpi). At 35 dpi pigs were necropsied and histopathological studies as well as in situ hybridization (ISH) were performed. Blood samples were taken weekly and used to determine PCV2 viral load by means of a quantitative PCR (qPCR), anti-PCV2 antibodies (IPMA), total anti-ADV antibodies and ADV-neutralizing antibodies (NA). Cell mediated immunity against PCV2 and ADV was measured by means of the IFN-γ ELISPOT.
No relevant clinical signs or gross and microscopic lesions were observed in PCV2-inoculated pigs. Although all PCV2-inoculated pigs developed viremia, only one animal (IC group) was still positive for PCV2 by ISH at 35 dpi. ADWG from 0 to 14 dpi and from 21 to 28 dpi were lower in PCV2- inoculated pigs compared with non-inoculated ones. Also, PCV2-inoculated pigs seroconverted by 14 dpi, reaching an average IPMA titer of 13log2 at 35 dpi. PCV2-specific IFN-γ ELISPOT responses were noticeable from 21 dpi onwards in PCV2-inoculated pigs compared to non-inoculated ones. No differences between inoculated groups (IC and IV) were observed for IPMA titers or IFN-γ ELISPOT. All pigs had no ADV antibodies at the starting of the experiment. By 35 dpi (3 weeks post-ADV vaccination) ADV NA were found in all vaccinated animals but one from group IV; no significant differences in ADV NA between CV and IV were observed. Both groups showed significant ADV-specific IFN-γ responses in ELISPOT as early as 21 dpi (7 days postvaccination). No differences were observed in ADV-specific IFN-γ responses between CV and IV.
In the purpose of this latter point, the effect of a PCV2 subclinical infection upon ADV vaccination in pigs was assessed. In the present study, immune responses after ADV vaccination (measured by NA and interferon responses) were not significantly affected by a subclinical PCV2 infection.
I. Díaz, M. Cortey, M. Sibila, L. Darwich, E. Mateu, J. Segalés. Effects of a Porcine Circovirus type 2 (PCV2) sublinical infection upon immunological parameters following an Aujeszky?s disease virus vaccination. 6th International Symposium on Emerging and Re-emerging Pig Diseases.
