Efficacy of a 3C-like protease inhibitor in treating various forms of acquired feline infectious peritonitis

Pedersen, Niels C; Kim, Yunjeong; Liu, Hongwei; Galasiti Kankanamalage, Anushka C; Eckstrand, Chrissy; Groutas, William C; Bannasch, Michael; Meadows, Juliana M; Chang, Kyeong-Ok

Treatment failures may also result from an inability of the host to mount a protective immune response during the period when virus replication is being suppressed. Such a failure has been observed for HCV infection of people. 2 T-cell-mediated immunity plays an important role in protective immunity, which occurs for about 20% in acute infection of HCV, 26 and an equal or greater proportion of FIPV infection. [15] [16] [17] The possible synergism of T-cell-mediated viral clearance and antiviral drug therapy in cats with FIP remains to be investigated. There may also be merit in combining antiviral drugs and stimulants of T-cell immunity for FIP treatment, such as the combination of interferons and ribavirin for the treatment of HCV infection. 2 The sustained remission in 6/7 cats that were treated for 12 weeks or longer was somewhat predictable. These cats were 3.3-4.4 months of age when presented for acute signs of either abdominal (C15, C17, C18, CT21, CT23) or thoracic effusive FIP (CT20). This made them younger than all but three (CT8, CT16, CT21 ) other cats in the trial and more closely resembling the 16-week-old laboratory cats with acute-onset effusive FIP that responded well to GC376. 6 The disease, being more acute, may allow less time for virus to spread to the brain or eyes. The acuteness of their disease may have also allowed less time for the infection to permanently compromise any protective immune response. The seventh cat, CT04, was an extreme to these six younger cats. CT04 was the oldest cat in the study at 6.8 years that presented with substantial weight loss (30%) and disease limited to mesenteric lymph nodes. CT04 suffered disease relapses requiring reinstitution of treatment, but all relapses were identical to the presenting condition and did not involve the CNS. Cats with this form of FIP have been known to undergo spontaneous remissions, indicating that there is a tipping point between immunity and disease. 13, 27, 28 Cats CT04 and CT21 demonstrated the wisdom of re-instituting treatment when relapses occurred, providing that those relapses do not involve the eyes or nervous system and are still drug responsive.