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BACKGROUND: Little is known about the kinetics of anti-H5 neutralizing antibodies in naturally H5N1-infected patients with severe clinical illness or asymptomatic infection. METHODS: Using H5N1 microneutralisation (MN) and H5-pseudotype particle-based microneutralisation assays (H5pp) we analyzed sera sequentially obtained from 11 severely ill patients diagnosed by RT-PCR (follow-up range 1-139 weeks of disease onset) and 31 asymptomatically infected individuals detected in a sero-epidemiological study after exposure to H5N1 virus (follow-up range: 1-2 month-11 months after exposure). RESULTS: Of 44 sera from 11 patients with H5N1 disease, 70% tested positive by MN (antibody titre > or = 80) after 2 weeks and 100% were positive by 3 weeks after disease onset. The geometric mean MN titers in severely ill patients were 540 at 1-2 months and 173 at 10-12 months and thus were higher than the titers from asymptomatic individuals (149 at 1-2 months, 62.2 at 10-12 months). Fractional polynomial regression analysis demonstrated that in all severely ill patients, positive titers persisted beyond 2 years of disease onset, while 10 of 23 sera collected 10-11 months after exposure in asymptomatically infected individuals tested negative. CONCLUSIONS: Our results indicate that people with asymptomatic H5N1 infection have lower H5N1 antibody titres compared to those with severe illness and that in many asymptomatically infected patients the antibody titer decreased to levels below the threshold of positivity within one year. These data are essential for the design and interpretation of sero-epidemiological studies.

Axin is a multidomain scaffold protein that exerts a dual function in the Wnt signaling and MEKK1/JNK pathways. This raises a critical question as to whether Axin-based differential molecular assemblies exist and how these may act to coordinate the two separate pathways. Here we show that both wild-type glycogen synthase kinase-3 beta (GSK-3 beta) and kinase-dead GSK-3 beta -Y216F (capable of binding to Axin), but not GSK-3 beta -K85M (incapable of binding to Axin in mammalian cells), prevented MEKK1 binding to the Axin complex, thereby inhibiting JNK activation. We further show that casein kinase le also inhibited Axin-mediated JNK activation by competing against MEKK1 binding. In contrast,. beta -catenin and adenomatous polyposis coli binding did not affect MEKK1 binding to the same Axin complex. This suggests that even when Axin is "switched" to activate the JNK pathway, it is still capable of sequestering free beta -catenin, which is a critical aspect for cellular homeostasis. Our results clearly demonstrate that differential molecular assemblies underlie the duality of Axin functions in the negative regulation of Wnt signaling and activation of the JNK MAPK pathway.

Axin is a multidomain scaffold protein that exerts a dual function in the Wnt signaling and MEKK1/JNK pathways. This raises a critical question as to whether Axin-based differential molecular assemblies exist and how these may act to coordinate the two separate pathways. Here we show that both wild-type glycogen synthase kinase-3 beta (GSK-3 beta) and kinase-dead GSK-3 beta -Y216F (capable of binding to Axin), but not GSK-3 beta -K85M (incapable of binding to Axin in mammalian cells), prevented MEKK1 binding to the Axin complex, thereby inhibiting JNK activation. We further show that casein kinase le also inhibited Axin-mediated JNK activation by competing against MEKK1 binding. In contrast,. beta -catenin and adenomatous polyposis coli binding did not affect MEKK1 binding to the same Axin complex. This suggests that even when Axin is "switched" to activate the JNK pathway, it is still capable of sequestering free beta -catenin, which is a critical aspect for cellular homeostasis. Our results clearly demonstrate that differential molecular assemblies underlie the duality of Axin functions in the negative regulation of Wnt signaling and activation of the JNK MAPK pathway.

Axin is a multidomain scaffold protein that exerts a dual function in the Wnt signaling and MEKK1/JNK pathways. This raises a critical question as to whether Axin-based differential molecular assemblies exist and how these may act to coordinate the two separate pathways. Here we show that both wild-type glycogen synthase kinase-3 beta (GSK-3 beta) and kinase-dead GSK-3 beta -Y216F (capable of binding to Axin), but not GSK-3 beta -K85M (incapable of binding to Axin in mammalian cells), prevented MEKK1 binding to the Axin complex, thereby inhibiting JNK activation. We further show that casein kinase le also inhibited Axin-mediated JNK activation by competing against MEKK1 binding. In contrast,. beta -catenin and adenomatous polyposis coli binding did not affect MEKK1 binding to the same Axin complex. This suggests that even when Axin is "switched" to activate the JNK pathway, it is still capable of sequestering free beta -catenin, which is a critical aspect for cellular homeostasis. Our results clearly demonstrate that differential molecular assemblies underlie the duality of Axin functions in the negative regulation of Wnt signaling and activation of the JNK MAPK pathway.