PROS1 and infection: ,33, 34, 35 These changes have been observed previously, particularly in immunocompromised individuals with prolonged infection and treatment with CCP or monoclonal S-protein antibodies, suggesting that escape mutations are selected in vivo and passive immunisation of immunocompromised patients might promote selection of new variants.33, 34, 35, 36 This possibility has not been studied so far in the context of a controlled trial.