THE RELATIONSHIP BETWEEN THE INTERFERON-ALPHA RESPONSE AND VIRAL BURDEN IN PRIMARY SIV INFECTION

The interferon alpha (IFN-alpha) response of rhesus macaques was inves tigated during primary infection with pathogenic and attenuated simian immunodeficiency viruses (SIV), IFN-alpha was detected in the serum o f animals as early as day 4 after inoculation of SIV mac 251, but rema ined barely detected in animals infected with the attenuated virus SIV mac 251 Delta nef, The peak of IFN-alpha, secretion preceded that of antigenemia in animals infected with pathogenic virus, indicating that the IFN-alpha response did mot prevent viral spread, In addition, ele vated levels of IFN-alpha in the serum after the acute stage of infect ion was associated with persisting antigenemia, The analysis of lymph nodes (LNs) by in situ hybridization showed that, similar to the resul ts obtained with peripheral blood, the induction of IFN-alpha in lymph oid organs was rapidly detected in animals infected with the pathogeni c virus, but remained very limited in animals infected with the attenu ated virus, Quantitation of the hybridization signal indicated that IF N-alpha-producing cells were more numerous in the LNs of animals that had a high viral burden, Taken together, these findings indicate that the IFN-alpha response is unable to contain the initial burst of SIV r eplication.