Systemic and intestinal antibody responses to NSP4 enterotoxin of Wa human rotavirus in a gnotobiotic pig model of human rotavirus disease

• Published in: Journal of medical virology 2002-09, Vol.68 (1), p.119-128
• Main Authors: Iosef, Cristiana, Chang, Kyeong-Ok, Azevedo, Marli S.P., Saif, Linda J.
• Format: Article
• Language: English
• Subjects: Animals; Antibodies, Viral - blood; Antibodies, Viral - immunology; antibody responses; Antigens, Viral - genetics; Antigens, Viral - immunology; Biological and medical sciences; Cell Line; Diarrhea - blood; Diarrhea - immunology; Diarrhea - prevention & control; Disease Models, Animal; enterotoxin; Enterotoxins - genetics; Enterotoxins - immunology; Enzyme-Linked Immunosorbent Assay - methods; Experimental viral diseases and models; Germ-Free Life; Glycoproteins - genetics; Glycoproteins - immunology; gnotobiotic pigs; Humans; Immunoglobulin A - blood; Immunoglobulin A - immunology; Immunoglobulin G - blood; Immunoglobulin G - immunology; Immunoglobulin Isotypes; Immunoglobulin M - blood; Immunoglobulin M - immunology; Infectious diseases; Intestines - immunology; Kinetics; Medical sciences; NSP4; Rotavirus - immunology; Rotavirus Infections - blood; Rotavirus Infections - immunology; Rotavirus Infections - prevention & control; Swine; Toxins, Biological; Viral diseases; Viral Nonstructural Proteins - genetics; Viral Nonstructural Proteins - immunology
• ISSN: 0146-6615; 1096-9071
• DOI: 10.1002/jmv.10178

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 105 fluorescent focus units (FFU) of virulent Wa HRV (HRV‐V), to mimic natural infection, or with three doses of 5 × 107 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 106 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. J. Med. Virol. 68:119–128, 2002. © 2002 Wiley