A functional human IgM response to HIV-1 Env after immunization with NYVAC HIV C.

Env-specific IgG and IgM were detected in 25 and 60%, respectively, of volunteers immunized with NYVAC expressing clade C gp120. The serum sample with the highest IgM titre but undetectable IgG neutralized the homologous isolate with a reciprocal IC90 titre of 7.8 in the absence of complement, and 24.