Effect of neonatal thymectomy on the experimental enteric infection of germfree mice with a mouse adenovirus (author's transl)

Abstract

The enteric infection and the appearance of antibodies and immunoglobulins were examined in neonatally thymectomized germfree ICR mice.Mouse adenovirus (MAD), strain K-87, was used in this study. Thymectomy was done within 24 hours after birth. MAD was inoculated orally to 4-to 6-week-old mice through a metal tube inserted into the stomach. The infectivity titer of the virus and the titer of neutralizing antibodies were determined in DKI mouse kindey tissue culture. Titration of the 3 classes of immunoglobulin was performed by the precipitation in agarose gel.In unoperated control mice, no viral growth was seen 3 weeks after challenge. In the thymectomized mice, however, a clear prolongation of viral growth was observed.Neutralizing antibodies in the serum began to increase in titer in the control mice 2 weeks after challenge. In the operated mice, the appearance of neutralizing antibodies was retarded. These antibodies in the intestinal wall and contents began to increase in titer in the control mice 3 weeks after challenge, but their appearance was retarded in the thymectomized mice.Immunoglobulin examinations were carried out to clarify the status of IgA, IgG, and IgM.The titers of IgA both in the serum and in the intestinal wall and contents were significantly lower in the thymectomized mice than in the control mice. IgG in the serum increased a little within the uninfected germfree mouse level in the control mice, but decreased in the thymectomized mice. IgM in the serum was within the uninfected germfree mouse level both in the control and in the thymectomized mice.IgG and IgM in the intestinal wall and contents were undetectable both in the operated and in the unoperated mice.Thus, prolonged growth of the virus was observed in the neonatally thymectomized germfree mice.At the same time, the appearance of neutralizing antibodies both in the serum and in the intestinal wall and contents was retarded. As there was no correlation between viral growth and the presence of serum antibody, it seemed that the delayed appearance of local neutralizing antibody might have prolonged viral growth in the thymectomized mice.Retardation of the appearance of IgA in the intestinal tract, which was undetectable in the uninfected germfree mice, was also observed in the thymectomized mice. This finding lends support to the presumption that the neutralizing antibody may belong to the IgG class of immunoglobulin.