NEONATAL DISEASE INDUCED BY SIV INFECTION OF THE RHESUS-MONKEY (MACACA-MULATTA)

Seven 72-hr-old Indian origin rhesus monkeys (Macaca mulatta) were ino culated with 10 animal ID50 of SIV/DeltaB670. Nine age-matched animals were used as uninoculated controls. All seven inoculated animals beca me infected as verified by viral isolation and SIV p26 antigenemia. Fi ve of seven infected animals died within a mean of 31 days (range, 26- 41 days), with high levels of antigenemia beginning 1-2 weeks postinoc ulation (PI) that persisted until death. Absolute lymphocyte numbers w ere within normal limits in all animals in both groups throughout the study. Inoculated animals that died within a mean of 31 days (short-te rm survivors) had significantly lower numbers of CD4+CD29+ (helper/ind ucer) lymphocytes than did long-term surviving inoculated animals thro ugh 3 weeks PI. Numbers of CD4+ lymphocytes were no different when con trols were compared to all inoculated animals through 4-5 weeks PI. Th e two inoculated animals surviving 216 and 423 days PI (long-term surv ivors) did demonstrate declining CD4+ cells, but only late in disease. CD8+ lymphocytes were significantly lower in short-term survivors whe n compared to long-term survivors through 5 weeks PI. Antibody product ion against SIV viral proteins was detected only in long-term survivor s and was similar to results from past studies in juveniles. Clinical signs in the inoculated group were consistent with those seen in past studies on older animals. Persistent bacterial infections, primarily o f the GI and respiratory tracts, were seen in the infected group. Asid e from the lack of some opportunistic infections such as cytomegalovir us (CMV) and Pneumocystic carinii, necropsy findings were not differen t when compared to past studies on juvenile animals. We concluded from the experimental results that mean survival time after inoculation in 3-day-old infants is considerably shorter than in animals inoculated as juveniles and that a greater percentage of infected animals demonst rated persistent antigenemia and progressive disease. A decline in the CD4+CD29+ lymphocyte subset may be a more reliable early indicator of progressive disease and early death than declining CD4+ percentages i n the SIV-infected neonate.