An Investigation into the Basic Virus-Antibody Neutralization Reaction, with Special Regard to the Reaction in the Constant-Virus/Varying-Serum Neutralization Test^*

Abstract

A study of the basic reaction in neutralization of virus (V) by virus-neutralizing antibody (VNA) was performed with infectious bovine rhinotracheitis virus and serum collected from naturally and experimentally infected cattle after the primary immunization phase. In constant-virus/varying-serum neutralization tests a direct proportionality between VNA titer and length of preincubation was observed and found to be in accordance with basic laws of neutralization. A deviation from this direct proportionality, which was partly attributed to the presence of a dissociable V-VNA complex, was seen with relatively short preincubation. Expressing a relationship between VNA titer, length of preincubation, and virus dose under conditions where a dissociable V-VNA complex can be ignored, a log. VNA/log. V equivalence factor of neutralization was introduced. A linear relationship was found between VNA titer, taken logarithmically, and preincubation temperature. A rise in temperature by 10°C gave an increase in VNA titer of approx. 1.2 in log₂. Formulae are presented for the neutralization rate factor corrected for a demonstrated invalidity of the percentage law, and for the relation between the neutralization rate factor and VNA titer. It is concluded that the results presented have elucidated the possibilities of improving the sensitivity of neutralization tests.

Sammendrag

Den basale reaktion mellem virus (V) og virusneutraliserende antistoffer (VNA) er undersøgt ved anvendelse af infektiøst bovint rhinotracheitisvirus og serum af naturligt og eksperimentelt inficeret kvæg opsamlet lang tid efter smitte. I konstant-virus/varierendeserum-neutralisationstests fandtes ligefrem proportionalitet mellem VNA-titer og præinkubationstiden, hvilket kunne findes at være i overensstemmelse med basale love for virusneutralisation. Ved relativt korte præinkubationstider sås en afvigelse fra den fundne simple relation som delvis kunne tilskrives dissocierbare V-VN A-f orbin deiser. Relationen gældende under forhold, hvor sådanne forbindelser kan negligeres, mellem VNA-titer, præinkubationstiden og virusdosis gives. Herved introduceres en log.VNA/log.V-ækvivalensfaktor for neutralisationsforløbet. Der fandtes en lineær relation mellem den logaritmiske vær di for VNA-titer og præinkubationstemperaturen, idet en forhøjelse af temperaturen med 10°C modsvarede en forøgelse af VNA-titeren med en faktor på 2,3. Der gives formler for neutralisationshastighedsfaktoren korrigeret for en fundet begrænset gyldighed af „the percentage law” og for relationen mellem denne størrelse og VNA-titeren. Det konkluderes, at undersøgelsesresultaterne belyser mulighederne for forbedring af følsomheden af neutralisationstests.