Profiling Of The Dominant Epitopes Of Neutralizing Antibodies Against Human Adenovirus Type 14 And 55

1.BackgroundHuman adenovirus type 14(Ad14)and 55(Ad55),both belonging to Species B,have been reported to cause outbreaks in recent years.Ad14 or Ad55 infection usually leads to sever respiratory diseases and even deaths.Althouthg the Fiber and Penton base of Ad14 and Ad55 share greatly similar sequenc,the hyper-viable-regions(HVR)of their Hexon are heterologous.Our previous results revealed a low level of herd immunity to Ad14 and Ad55 in general populations from Southern China.Drugs or vaccines against Ad14 and Ad55 are still unavailable.We proposed that clarification of the dominant epitopes of neutralizing antibodies(n Abs)against these two adenoviruses would facilitate the development of therapeutic monoclonal n Abs and prophylactic vaccines.2.ObjectiveTo generate chimeric Ad14 reporter viruses harboring each single or the entire HVR from Ad55,and identify the dominant epitopes of n Abs against Ad14 and Ad55.3.MethodsChimeric Ad14 reporter viruses harboring each single or the entire hyper-variable-region(HVR)from Ad55 hexon were constructed using homologous recombination.The epitopes of hexon-specific n Abs were analyzed through assessing the neutralizing capacity of Ad14 neutralzing serums and Ad55 neutralizing serums to these chimeric Ad14 viruses.Fiber-specific antibodies were evaluated using Western-blot analysis,and the neutralizing capacity of these antibodies was assessed through absorption with fiber knob and neutralizing assays.Penton-specific antibodies were examined using Western-blot analysis.Murine immune sera were prepared by immunizing Balb/C mice with inactivated Ad14 or Ad55 viral particals,and the epitope recognition profiles were also analyzed.Finally,mice were repeatedly immunized with fiber knobs and the n Ab responses were analyzed.4.ResultsWe successfully generated 8 chimeric Ad14 reporter viruses which carried each single or the entire hyper-variable-region(HVR)from Ad55 hexon,and revealed that the hexon-specific huaman n Abs predominantly recognized HVR2,5,and 7.Fiber-specific n Abs only appear in Ad14,Ad55 dcross-neutralizing serums,but contribute substantially to cross-neutralization.Although cross-reactive penton-binding antibodies were frequently detected,they showed no significant neutralizing activity.The recognition profile of mouse n Abs primarily recognize HVR1,2 and 7 of Ad14,and HVR1 and 2 of Ad55,respectively.Importantly,repeated immunization with purified fiber knob elicits n Abs neutralizing both Ad14 and Ad55,and Ad55 fiber knob possesses stronger immunogenicity than Ad14 fiber knob.5.ConclusionsWe clarified the epitope recogniation profile of n Abs induced by natural infection and adenovirus immunization,and found that fiber-specific n Abs cross-neutralizing both Ad14 and Ad55.These results not only expand our understanding about n Ab response against Ad14 and Ad55 in human and in animal models,but have significant implications in monoclonal n Ab and vaccine development.