A Study of Antigenic Relationships Between Trichinella Spiralis and Salmonella Typhi

Summary and Conclusions

Normal rabbits were immunized with a Trichinella spiralis larval antigen and Salmonella typhi respectively. Since the pre-immunization serum samples contained antibody against neither S. typhi nor T. spiralis, any antibody present in the immune serum samples was the result of contact with the respective immunizing agents. Thus, the fact that the anti-trichinella rabbit serum was able to react to a titer of 1:100 with typhoid “O” and 1:1000 with typhoid “H” antigens and that the anti-typhoid rabbit serum reacted with the trichinella larval antigen to a titer of 1:800 is highly significant and indicative of a heterogenetic type reaction.

That a true heterogenetic reaction exists between the two organisms was proven by the results of absorption studies. The typhoid reactivity could be completely removed from anti-trichinella rabbit serum by one absorption tion with S. typhi. This resulted in an antiserum whose trichinella titer was somewhat reduced (from 1:40,000 to 1:16,000) by the absorption process. The reciprocal absorption was performed with equally conclusive results. Absorption of anti-typhoid rabbit serum with groud dried larvae completely removed the trichinella reactivity with a concomitant reduction of anti-typhoid “O” titer from 1:20,000 to 1:800 and of anti-typhoid “H” titer from 1:20,000 to 1:10,000.

The present study also indicates that the ability of anti-trichinella serum to cross-react is not limited to S. typhi since this serum also agglutinated Salmonella paratyphi A, B and C as well as Klebsiella pneumoniae. The positive reactions obtained with the paratyphoid species is not surprising since they have antigenic components in common with S. typhi. For instance, S. paratyphi A and B and S. typhi all contain somatic antigen XII while S. paratyphi C and S. typhi each contain the Vi antigen. The positive reaction with Kl. pneumoniae cannot be explained on the basis of the known antigens cited and may indicate that there is a relationship between this organism and still another trichinella larval component.

The reliability of data obtained from studies on clinical serum samples is in some instances questionable since control serum specimens and/or adequate histories were not always available. In the case of patient J. Y., however, where a complete history was available, it is felt that an interesting and valuable finding was made. This child was diagnosed as having typhoid fever. Since there was no history of trichinosis in the child (or her parents) and no specific symptoms referable to trichinosis, the appearance of antitrichinella antibodies in this serum may be the result of the active typhoid infection. To our knowledge this is the first report of such a finding.

Those data obtained from tests with the paratyphoid organisms suggest that only the somatic antigens of S. typhi are involved in the observed cross-reactions. However, since the anti-trichinella rabbit serum reacted with both “O” and “H” antigens this may not be the case. Current studies with highly specific “O” and “H” antisera and with purified larval components are in progress in an effort to obtain definitive knowledge of the actual antigens involved in this heterogenetic reaction.