Kinetics of single and dual simultaneous infection of pigs with swine influenza A virus and porcine reproductive and respiratory syndrome virus

Abstract

Background: Simultaneous viral infections exhibit the phenomenon of viral interference, but understanding of the effect of one virus on another is limited. Objective: Evaluate and compare clinical characteristics, immune and acute phase response, viral shedding and viral load in pigs singly and doubly inoculated with swine influenza A virus (swIAV) and porcine reproductive and respiratory syndrome virus (PRRSV). Animals: Fifty-four 7-week-old piglets. Methods: Clinical status and gross lung lesions were scored. Titration of swIAV was carried out in Madin-Darby canine kidney cells. The PRRSV RNA was quantified using a commercial qPCR kit. Antibodies were detected by hemagglutination inhibition assay and commercial ELISA. A lymphocyte proliferation assay was used to measure antigen-specific T-cell responses. Acute phase proteins were determined using ELISA. Results: No differences were found between mean clinical scores, swIAV and PRRSV shedding, and magnitude of the humoral and T-cell response between single-inoculated and dual-inoculated groups. Concentrations of C-reactive protein and haptoglobin increased in PRRSV-inoculated and coinoculated groups, whereas serum amyloid A concentration was increased in groups inoculated or coinoculated with swIAV. Mean swIAV TCID 50 titers in the lungs did not differ significantly between coinoculated and swIAV single-inoculated pigs. A significantly higher mean copy number of PRRSV was found in the lungs of PRRSV only-inoculated pigs at 2 day postinoculation (DPI). From 4 DPI, no significant differences in PRRSV load were identified. Conclusions and Clinical Importance: Coinfection of pigs with swIAV and PRRSV did not potentiate clinical signs, lung lesions, immune response, and replication of the viruses in the respiratory tract.

Respiratory viral infections drive different lung cytokine profiles in pigs

“…The lung samples used in the study were collected during an animal challenge experiment described elsewhere [ 27 ].…”

“…Pigs were inoculated intranasally with IAV (avian-like H1N1, isolated from the pig suffering from acute swine influenza (A/Poland/Swine/14,131/2014; SwH1N1) and/or PRRSV (strain PL15-33, subtype 1 PRRSV, isolated from a lung obtained from a pig with respiratory clinical signs from a Polish herd). Virus propagation was carried out as previously described [ 27 ].…”

“…Individual pigs were subjected to daily clinical examination and measurement of rectal body temperature (from day 7 pre inoculation until day 21 post inoculation (DPI) or until euthanasia (at 2, 4 and 10 DPI). The severity of clinical lesions was assessed based on a scoring system adapted to PRRS and SI [ 27 ]. A clinical scoring system with predefined humane endpoints was used to prevent undue suffering.…”

“…Gross lung lesions were scored according to method described by Halbur et al [ 28 ] and adapted by Pomorska-Mól et al [ 27 ]. The observed lesions were described in details in Pomorska-Mól et al [ 27 ].…”

“…Gross lung lesions were scored according to method described by Halbur et al [ 28 ] and adapted by Pomorska-Mól et al [ 27 ]. The observed lesions were described in details in Pomorska-Mól et al [ 27 ]. In summary, each lung lobe was assigned a number to reflect the approximate volume percentage of the entire lung represented by that lobe, to reach the total of 100 possible points.…”