Ben E. Sheffy

Reactivation of a bovine herpesvirus after corticosteroid treatment.

Summary Consistent recrudescence of IBR virus from latently infected cattle following a series of inoculations of a synthetic corticosteroid has been demonstrated. In addition IBR virus was frequently recovered from the tissues of the upper respiratory tract, and irregularly in a number of other organs by organ culture techniques. While IBR virus was recovered from all treated animals it was never recovered from nasal and conjunctival secretions of control animals or from treated animals until after 3 days of steroid inoculations and was recovered from tissues of only 1/9 untreated animals. We are grateful to Miss Susan Rodman and Mrs. Pamela Natowsky for their excellent technical assistance.

Propagation of hog cholera virus in tissue culture.

Summary A strain of hog cholera virus has been procured that produced CPE in tissue cultures of pig kidney cells. This tissue-cultured virus produced typical hog cholera when inoculated into susceptible swine and it was neutralized by immune sera.

A Persistent Hog Cholera Viremia in Young Pigs.

Summary A persistent hog cholera viremia was produced in pigs from non-immune mothers that were 6 weeks of age, but not in pigs that were 3 months of age or in pigs from immune mothers that were 6 weeks of age. Although a similar condition of immunological tolerance has been reported for other animals, it was produced either in utero or shortly after birth. These pigs, therefore, appear unusual because persistence of virus was established at an older age. Pigs with persistent viremia failed to grow and showed elevated temperatures but survived for periods from 6 to 17 weeks. During this interval, persistent virus reverted to a fully virulent state. When they became moribund, virus titers of spleens from stunted pigs ranged from 107 to 109 in contrast to 105 found in spleens from moribund pigs infected with virulent virus in the usual manner. The ability of hog cholera virus to transmit in utero and to persist in pigs after birth may have epidemiological implications.

Relationship between hog cholera virus and virus diarrhea virus of cattle.

Summary Pigs inoculated with VD (virus diarrhea) virus survived inoculations of virulent HC (hog cholera) virus that killed littermates that had not received VD virus. Survival was signalized by accelerated antibody production both to HC and VD viruses. In reciprocal tests, HC virus produced secondary response in calves. Reciprocal neutralization tests between VD virus and HC virus showed they did not share a common antibody. Protection appeared related to accelerated antibody production that resembled the secondary response induced by inactivated viral antigen.