Influenza Superinfection in Murine Filariasis

Female BALB/c mice were purchased from Charles River and maintained under specific pathogen free conditions at the University of Edinburgh. Mice were used at 6–8 weeks of age. To maintain the L. sigmodontis lifecycle, L. sigmodontis infected jirds (Meriones unguiculatus) were used to infect haematophagous tick parasites (Ornithonyssus bacoti) in order to generate L3 stage larvae (23 ). Mice were infected s.c. on the upper back with 30 L. sigmodontis L3 stage larvae. L. sigmodontis larvae or adults were recovered from the pleural cavity by lavage and counted using a dissection microscope. To quantify blood Mf, 30 μL of tail blood was collected in FACS lysing solution (Becton-Dickinson) and the Mf counted using a haemocytometer. IAV infections were performed intranasally with 5x10³ PFU A/WSN/33, a mouse H1N1 influenza A strain (Dr D. Jackson, University of St Andrews, St Andrews, UK), either 12, 34 or 68 days (d) post L. sigmodontis or mock infection. A/WSN/33 was grown in MDCK cells as described previously (24 (link)). Mice were weighed daily and assessed for visual signs of clinical disease as described previously (25 (link), 26 (link)). Briefly, signs of infection were scored as follows, reduced mobility/activity (0-3), ruffled fur/piloerection (0-3), hunched posture (0-3) and increased or laboured breathing (0-3). The severity score presented is a sum of these criteria.