Transient Immune Activation in BCG-Vaccinated Infant Rhesus Macaques Is Not Sufficient to Influence Oral Simian Immunodeficiency Virus Infection.

BCG vaccination has been demonstrated to increase levels of activated CD4+ T cells, thus potentially influencing mother-to-child transmission of human immunodeficiency virus (HIV). To assess the risk of BCG vaccination in HIV infection, we randomly assigned newborn rhesus macaques to receive BCG vaccine or remain unvaccinated and then undergo oral simian immunodeficiency virus (SIV) challenges 3 weeks later. We observed elevated levels of activated peripheral CD4+ T cells (ie, HLA-DR+CD38+CCR5+ CD4+ T cells) by week 3 after vaccination. BCG was also associated with an altered immune gene expression profile, as well as with monocyte activation in both peripheral blood and the draining axillary lymph node, indicating significant BCG vaccine-induced immune activation. Despite these effects, BCG vaccination did not increase the rate of SIV oral transmission or disease progression. Our findings therefore identify patterns of T-cell and monocyte activation that occur after BCG vaccination but do not support the hypothesis that BCG vaccination is a risk factor for postnatal HIV transmission or increased pathogenesis in infants.

Comprehensive in vitro analysis of simian retrovirus type 4 susceptibility to antiretroviral agents.

Simian retrovirus type 4 (SRV-4), a simian type D retrovirus, naturally infects cynomolgus monkeys, usually without apparent symptoms. However, some infected monkeys presented with an immunosuppressive syndrome resembling that induced by simian immunodeficiency virus infection. Antiretrovirals with inhibitory activity against SRV-4 are considered to be promising agents to combat SRV-4 infection. However, although some antiretrovirals have been reported to have inhibitory activity against SRV-1 and SRV-2, inhibitors with anti-SRV-4 activity have not yet been studied. In this study, we identified antiretroviral agents with anti-SRV-4 activity from a panel of anti-human immunodeficiency virus (HIV) drugs using a robust in vitro luciferase reporter assay. Among these, two HIV reverse transcriptase inhibitors, zidovudine (AZT) and tenofovir disoproxil fumarate (TDF), potently inhibited SRV-4 infection within a submicromolar to nanomolar range, which was similar to or higher than the activities against HIV-1, Moloney murine leukemia virus, and feline immunodeficiency virus. In contrast, nonnucleoside reverse transcriptase inhibitors and protease inhibitors did not exhibit any activities against SRV-4. Although both AZT and TDF effectively inhibited cell-free SRV-4 transmission, they exhibited only partial inhibitory activities against cell-to-cell transmission. Importantly, one HIV integrase strand transfer inhibitor, raltegravir (RAL), potently inhibited single-round infection as well as cell-free and cell-to-cell SRV-4 transmission. These findings indicate that viral expansion routes impact the inhibitory activity of antiretrovirals against SRV-4, while only RAL is effective in suppressing both the initial SRV-4 infection and subsequent SRV-4 replication.

Design, biologic evaluation, and SAR of novel pseudo-peptide incorporating benzheterocycles as HIV-1 protease inhibitors.

A series of novel HIV-1 protease inhibitors based on the (hydroxyethylamino)-sulfonamide isostere incorporating substituted phenyls and benzheterocycle derivatives bearing rich hydrogen bonding acceptors as P(2) ligands were synthesized. Prolonged chain linking the benzhereocycle to the carbonyl group resulted in partial loss of binding affinities. Introduction of a small alkyl substituent with appropriate size to the -CH2- of P(1)-P(2) linkage as a side chain resulted in improved inhibitory potency, and in this study, isopropyl was the best side chain. Replacement of the isobutyl substituent at P(1)'group with phenyl substituent decreased the inhibitory potency. One of the most potent inhibitor, compound 23 showing high affinity to HIV-1 protease with an IC(50) value of 5 nM, also exhibited good anti-SIV activity (EC(50) = 0.8 microM) with low toxicity (TC(50) > 100 microM). The flexible docking of inhibitor 23 to HIV-1 protease active site rationalized the interactions with protease.

Antiretroviral drug studies in nonhuman primates: a valid animal model for innovative drug efficacy and pathogenesis experiments.

Several nonhuman primate models are used in HIV and AIDS research. In contrast to HIV-1 infection of chimpanzees, infection of macaque species with simian immunodeficiency virus (SIV) isolates results in a disease (simian AIDS) that shares many similarities with HIV infection and AIDS in humans. Although each animal model has its limitations and can never completely mimic HIV infection of humans, a carefully designed study allows experimental approaches, such as the control of certain variables, that are not feasible in humans, but that are often the most direct way to gain better insights in disease pathogenesis and provide proof-of-concept for novel intervention strategies. In the early days of the HIV pandemic, nonhuman primate models played a relatively minor role in the anti-HIV drug development process. During the past decade, however, the development of better virologic and immunologic assays, a better understanding of disease pathogenesis, and the availability of better drugs have made these animal models more practical for drug studies. In particular, nonhuman primate models have played an important role in demonstrating: (i) preclinical efficacy of novel drugs such as tenofovir; (ii) the benefits of chemoprophylaxis, early treatment and immunotherapeutic strategies; (iii) the virulence and clinical significance of drug-resistant viral mutants; and (iv) the role of antiviral immune responses during drug therapy. Comparison of results obtained in primate models with those observed in human studies will lead to further validation and improvement of these animal models. Accordingly, well-designed drug studies in nonhuman primates can continue to provide a solid scientific basis to advance our scientific knowledge and to guide future clinical trials.

The effect of chronic binge ethanol consumption on the primary stage of SIV infection in rhesus macaques.

BACKGROUND: Alcohol abuse and infection with HIV individually compromise immune function, but the consequence of both conditions together is poorly understood owing to the difficulties of performing appropriate studies in human subjects. Simian immunodeficiency virus (SIV) infection of rhesus macaques is considered to closely model HIV disease in that the virus infects CD4+ cells and this infection leads to a similar AIDS state. This study was initiated to study the combined effects of chronic binge alcohol consumption on the primary stage of SIV infection. METHODS: Rhesus macaques were administered alcohol or isocaloric sucrose via a permanently indwelling intragastric catheter 4 consecutive days per week for the duration of the study. Doses were individualized to achieve plasma alcohol concentrations of 50-60 mM over a 5-hr period. After 3 months, animals were inoculated intravenously with 10,000 times the ID(50) (50% infective dose) of SIV(DeltaB670) at the conclusion of an alcohol session and followed for 2 months postinoculation. RESULTS: At 1 week, plasma SIV RNA was greater than 60-fold higher in alcohol-consuming animals compared with sucrose controls. Likewise, alcohol consumption enhanced the SIV-induced increase in cell cycling T lymphocytes (i.e., cells expressing Ki67 protein) in blood. These differences between alcohol- and sucrose-treated animals were not sustained during the observation period. Peak viral load occurred 2 weeks post-SIV inoculation at 7.6 +/- 4.2 and 5.2 +/- 3.1 x 106 copies/ml in alcohol- versus sucrose-consuming animals, respectively. Blood CD4+ lymphocyte numbers were decreased 1 and 2 months after SIV inoculation to a similar degree in both sucrose-control and alcohol-treated animals. CONCLUSIONS: The consequence of the early rise in viral load and increase in lymphocyte turnover seen with excess alcohol consumption is unknown. We hypothesize that alcohol intoxication may increase the susceptibility of the host to HIV/SIV infection. This possibility needs to be explored further.

Inhibitors of retrovirus infection are secreted by several hamster cell lines and are also present in hamster sera.

We have previously shown that Chinese hamster ovary (CHO) cells are resistant to infection by gibbon ape leukemia virus and amphotropic pseudotype retroviral vectors because of the secretion of factors that inhibit retrovirus infection. Such factors were not secreted by any mouse or human cell lines tested. Secretion of the inhibitors and resistance to infection are abrogated by treatment of CHO cells with the glycosylation inhibitor tunicamycin. Here we show that the inhibitory activities against gibbon ape leukemia virus and amphotropic viruses are partially separable and that glycosylation mutations in CHO cells mimic the effects of tunicamycin treatment. We find that several hamster cell lines derived from both Chinese and Syrian hamsters secrete inhibitors of retrovirus infection, showing that these inhibitors are not unique to the CHO cell line. Inhibitory factors are also present in the sera of Chinese and Syrian hamsters but were not detected in bovine serum. These results suggest the presence of specific factors that function to inhibit retrovirus infection in hamsters.

The effects of poly(I).poly(C12U) and interferon on the multiplication of a mammalian type C retrovirus in human cells.

Poly(I).poly(C12U) or interferon treatment inhibited multiplication of the xenotropic baboon type C endogenous retrovirus M7 in chronically infected human AV3-M7 cells, as determined by a reverse transcriptase (RT) assay and electron microscopy. Furthermore, this polynucleotide induced 2'5' oligoadenylate (2'5'A) synthetase activity. In contrast to interferon (IFN), poly(I).poly(C12U) did not give rise to the appearance of a trapping phenomenon observable by electron microscopy. When AV3-M7 cells were treated simultaneously with poly(I).poly(C12U) and anti-IFN-beta/alpha antibodies, the induction of 2'5'A synthetase was abolished without any alteration of the inhibitory effect of RT activity. Taken together, these results suggest that different mechanisms are used by poly(I).poly(C12U) and IFN in blocking type C retrovirus multiplication.

Toxicity and efficacy of 2',3'-dideoxycytidine in clinical trials of pigtailed macaques infected with simian retrovirus type 2.

Four dosing regimens of 2',3'-dideoxycytidine (ddC) were administered intravenously for 10 to 28 days to 18 pigtailed macaques with simian acquired immunodeficiency syndrome. Ten macaques naturally infected with simian acquired immunodeficiency syndrome retrovirus serotype 2 (SRV-2), the etiologic agent of simian acquired immunodeficiency syndrome, received ddC by continuous intravenous infusion or by a daily bolus injection for 10 to 12 days. Another eight macaques that were negative for SRV-2 and antibody received ddC prophylaxis prior to challenge with virus and continued to receive ddC therapy for up to 28 days postchallenge. All monkeys treated with a continuous intravenous dose of ddC, which maintained plasma concentrations of ddC at levels known to inhibit SRV-2 in vitro, developed dose-related toxic effects, including leukopenia, anemia, lethargy, and decreased appetite. Monkeys treated with a daily bolus injection of ddC experienced more severe toxic effects than those on the continuous intravenous regimen, including exfoliative dermatitis and peripheral neuropathy. At the concentrations of ddC administered, no significant inhibition of SRV-2 replication was detected in naturally infected macaques. However, a prophylactic regimen of ddC did have an inhibitory effect on SRV-2. Our findings suggest that ddC may be valuable as a short-term prophylactic treatment rather than as a long-term therapy.