HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Trautman, R. Articles by Bennett, C. E. Search for Related Content PubMed PubMed Citation Articles by Trautman, R. Articles by Bennett, C. E. Agricola Articles by Trautman, R. Articles by Bennett, C. E.

Relationship Between Virus Neutralization and Serum Protection Bioassays for IgG and IgM Antibodies to Foot-and-Mouth Disease Virus

Plum Island Animal Disease Center, Science and Education Administration, U.S. Department of Agriculture, Greenport, NY 11944, U.S.A.

The time interval between administering the serum and the virus was found to influence the results of the in vivo mouse protection test for foot-and-mouth disease antibodies. In particular, for both IgG and IgM antibodies to strain A₁₂ virus, the mouse protection index increased from zero to a maximum at about 6 h and remained high for at least five days.

Variations in the antiserum concentration, on a log scale, had a proportional effect on the mouse protection index, if between 1 and 3. The constant of proportionality was unity for IgM and 2 for IgG antibody. Comparison with in vitro neutralization tests revealed essentially parallel neutralization curves. The lower serum titre in the protection test, if computed for less than 10³ LD₅₀/dose, was accounted for by the simple dilution of the inoculated serum into the volume of the mouse. Consequently, in the low titre range, the same virus-antibody reaction and its effect are operable in each of the two tests. Analysis of literature data in which both the in vivo protection test and the in vitro neutralization test results were available on the same sera showed consistency with the above conclusions for both cattle and swine sera.

The protection test had a highly atypical survival pattern occurring at antibody concentrations expected to neutralize more than 10³ LD₅₀/dose. The resulting in vivo dampening effect on virus titre is postulated to be caused by the excess antibody of the passive immunity test interfering with the spread of infection. The effect is analogous to an anomaly caused by not removing the inoculum in quantal tissue culture assays and it prevents quantification of antibody levels in strong sera.

Received 23 February 1978; accepted 30 August 1978.