The anti-gp41 virus neutralizing monoclonal antibody 2F5 was infused into chimpanzees, which were then given an intravenous challenge with a primary human immunodeficiency virus type 1 (HIV-1) isolate. In two control animals, the infection was established immediately, as evidenced by positive cell-associated DNA PCR and serum RNA PCR tests within 1 week, seroconversion by 4 weeks, and development of lymphadenopathy in this acute phase. Serum RNA PCR tests were negative in one of the two antibody-infused animals until week 8 and in the other antibody-infused animal until week 12; both animals seroconverted at week 14. The peak of measurable virus-specific serum RNA was delayed until week 16 in one antibody-infused animal. Virus-specific RNA in the other animal did not reach levels comparable to those in the other animals through 1 year of follow-up studies. Virus was isolated from the week 16 blood sample from one infused animal. Virus was not isolated from peripheral blood of the second animal but was isolated from lymph node cells taken at week 36. The infection of untreated chimpanzees with this primary isolate appears robust. Use of this isolate should widen the scope of possible experiments in the chimpanzee model. This antibody infusion study indicates that neutralizing antibody, when present at the time of challenge, affects the timing and level of infection and remains influential after it can no longer be detected in the peripheral circulation. It is possible that preexisting, neutralizing antibodies (passively administered or actively elicited) affect the course of acute-phase virus replication in humans. It remains to be established whether these immunologically mediated early effects will influence the course of HIV-1 disease.

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Background We report the causes of mortality for 4,350 captive baboons that died or were euthanized due to natural causes during a 23 year period at the Southwest National Primate Research Center. Methods Necropsy records were retrieved and reviewed to determine a primary cause of death or indication for euthanasia. Data was evaluated for morphological diagnosis, organ system and etiology. Results The 20 most common morphologic diagnoses accounted for 76% of the cases, including: stillborn (10.8%); colitis (8.6%); hemorrhage (8.4%); ulcer (5.2%); seizures (4.7%); pneumonia (4.2%); inanition (4.1%); dermatitis (3.8%); spondylosis (3.3%); and amyloidosis (3.0%). The digestive system was most frequently involved (21.3%), followed by the urogenital (20.3%), cardiovascular (12.2%), and multisystem disease (10.3%). An etiology was not identified in approximately one third of cases. The most common etiologies were trauma (14.8%), degenerative (9.5%), viral (8.7%), and neoplastic/proliferative (7.0%). Conclusion This information should be useful for individuals working with baboons.

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The absence of AIDS-like symptoms in HIV-infected chimpanzees and SIV-infected African Green monkeys (AGMs) may provide important clues about the pathogenic mechanism of AIDS and about mechanisms of resistance. HIV-infected persons and SIV-infected rhesus macaques have, on the average, markedly decreased cysteine, cystine, and glutathione levels and elevated plasma glutamate concentrations. Glutamate inhibits the membrane transport of cystine and a combination of low plasma glutamate and high cystine levels was found to be correlated with high CD4+ T cell numbers even in HIV-negative healthy human individuals. We have now found that glutamate and cystine levels are also correlated with CD4+ T cell numbers in chimpanzees. But infection of chimpanzees, AGMs, and goats with HIV-1, SIV, and caprine arthritis encephalitis virus (CAEV), respectively, does not induce significant changes in plasma cystine or glutamate levels, although infected AGMs and goats have, on the average, significantly elevated plasma levels of the biochemically related amino acid proline.