Systemic and intestinal antibody responses to NSP4 enterotoxin of Wa human rotavirus in a gnotobiotic pig model of human rotavirus disease.
Antibody responses to the Wa human rotavirus (HRV) nonstructural protein NSP4, a viral enterotoxin, were evaluated in neonatal gnotobiotic (Gn) pigs. Gn pigs were inoculated orally with one dose of 10(5) fluorescent focus units (FFU) of virulent Wa HRV (HRV-V), to mimic natural infection, or with three doses of 5 x 10(7) FFU attenuated Wa HRV (HRV-A) at 10-day intervals, to mimic oral attenuated rotavirus vaccines, or they were mock inoculated (mock). Subsets of pigs were challenged with 10(6) FFU of virulent Wa HRV at post-inoculation day 28 (PID 28). Post-challenge, the HRV-V pigs were completely protected against diarrhea and virus shedding, whereas the HRV-A pigs had a 50% protection rate against diarrhea and a 67% protection rate against virus shedding. All mock-inoculated pigs shed virus and had diarrhea post-challenge. Isotype antibody titers to NSP4 were compared in serum and intestinal contents, at post-inoculation day (PID) 28 and at post-challenge day 7 (PCD 7/PID 35) by indirect ELISA, using purified recombinant NH2-6xHis-tagged NSP4 of virulent Wa HRV. Pre-challenge, both the HRV-V and HRV-A-inoculated pigs had similar moderate titers of serum IgG antibodies to NSP4. However, only the HRV-V-inoculated pigs developed detectable serum and intestinal IgA antibody titers to NSP4 pre-challenge, compared with the HRV-A-inoculated pigs. The mock-inoculated pigs had no IgM, IgA, or IgG antibodies to NSP4 pre-challenge. All Wa HRV-inoculated pigs developed low to moderate titers of serum IgM, IgG, and IgA antibodies to NSP4 post-challenge, but the mock-inoculated pigs had only IgM antibodies post-challenge. Both Wa HRV-inoculated groups developed low titers of IgA antibody to NSP4 in the small intestinal contents post-challenge, but titers were 5.8-fold higher in the HRV-V pigs. Our results concur with findings that both rotavirus vaccinated and naturally infected children seroconvert with modest IgG antibodies to NSP4 [Johansen et al. (1999) J Med Virol 59:369-367]. These data suggest that Gn pigs could be a useful model to evaluate serum and intestinal IgA antibodies to NSP4 and their role in protection against HRV infection. Further experiments may clarify whether (1) the NSP4 antibodies detected pre-challenge in the HRV-V pigs contribute to the higher protection rates observed, or (2) the reduced or delayed NSP4 antibody responses of the HRV-A pigs are associated with the lower protection rates in these pigs.
Iosef
Cristiana
C
Department of Veterinary Preventive Medicine, Food Animal Health Research Program, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio, 44691-4096, USA.
Chang
Kyeong-Ok
KO
Azevedo
Marli S P
MS
Saif
Linda J
LJ
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology*; D000956:Antigens, Viral / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D003967:Diarrhea / Q000097:blood / Q000276:immunology* / Q000517:prevention & control; D004195:Disease Models, Animal; D004768:Enterotoxins / Q000235:genetics / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005856:Germ-Free Life; D006023:Glycoproteins / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood / Q000276:immunology; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D007132:Immunoglobulin Isotypes; D007075:Immunoglobulin M / Q000097:blood / Q000276:immunology; D007422:Intestines / Q000276:immunology*; D007700:Kinetics; D012401:Rotavirus / Q000276:immunology; D012400:Rotavirus Infections / Q000097:blood / Q000276:immunology* / Q000517:prevention & control; D013552:Swine; D014118:Toxins, Biological; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000276:immunology*
D000914:Antibodies, Viral; D000956:Antigens, Viral; D004768:Enterotoxins; D006023:Glycoproteins; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D007075:Immunoglobulin M; C081369:NS28 protein, rotavirus; D014118:Toxins, Biological; D017361:Viral Nonstructural Proteins