Role of CD8(+) lymphocytes in control of simian immunodeficiency virus infection and resistance to rechallenge after transient early antiretroviral treatment.

Transient antiretroviral treatment with tenofovir, (R)-9-(2-phosphonylmethoxypropyl)adenine, begun shortly after inoculation of rhesus macaques with the highly pathogenic simian immunodeficiency virus (SIV) isolate SIVsmE660, facilitated the development of SIV-specific lymphoproliferative responses and sustained effective control of the infection following drug discontinuation. Animals that controlled plasma viremia following transient postinoculation treatment showed substantial resistance to subsequent intravenous rechallenge with homologous (SIVsmE660) and highly heterologous (SIVmac239) SIV isolates, up to more than 1 year later, despite the absence of measurable neutralizing antibody. In some instances, resistance to rechallenge was observed despite the absence of detectable SIV-specific binding antibody and in the face of SIV lymphoproliferative responses that were low or undetectable at the time of challenge. In vivo monoclonal antibody depletion experiments demonstrated a critical role for CD8(+) lymphocytes in the control of viral replication; plasma viremia rose by as much as five log units after depletion of CD8(+) cells and returned to predepletion levels (as low as <100 copy Eq/ml) as circulating CD8(+) cells were restored. The extent of host control of replication of highly pathogenic SIV strains and the level of resistance to heterologous rechallenge achieved following transient postinoculation treatment compared favorably to the results seen after SIVsmE660 and SIVmac239 challenge with many vaccine strategies. This impressive control of viral replication was observed despite comparatively modest measured immune responses, less than those often achieved with vaccination regimens. The results help establish the underlying feasibility of efforts to develop vaccines for the prevention of AIDS, although the exact nature of the protective host responses involved remains to be elucidated.

Protection of Macaca nemestrina from disease following pathogenic simian immunodeficiency virus (SIV) challenge: utilization of SIV nucleocapsid mutant DNA vaccines with and without an SIV protein boost.

Molecular clones were constructed that express nucleocapsid (NC) deletion mutant simian immunodeficiency viruses (SIVs) that are replication defective but capable of completing virtually all of the steps of a single viral infection cycle. These steps include production of particles that are viral RNA deficient yet contain a full complement of processed viral proteins. The mutant particles are ultrastructurally indistinguishable from wild-type virus. Similar to a live attenuated vaccine, this approach should allow immunological presentation of a full range of viral epitopes, without the safety risks of replicating virus. A total of 11 Macaca nemestrina macaques were inoculated with NC mutant SIV expressing DNA, intramuscularly (i.m.) in one study and i.m. and subcutaneously in another study. Six control animals received vector DNA lacking SIV sequences. Only modest and inconsistent humoral responses and no cellular immune responses were observed prior to challenge. Following intravenous challenge with 20 animal infectious doses of the pathogenic SIV(Mne) in a long-term study, all control animals became infected and three of four animals developed progressive SIV disease leading to death. All 11 NC mutant SIV DNA-immunized animals became infected following challenge but typically showed decreased initial peak plasma SIV RNA levels compared to those of control animals (P = 0.0007). In the long-term study, most of the immunized animals had low or undetectable postacute levels of plasma SIV RNA, and no CD4(+) T-cell depletion or clinical evidence of progressive disease, over more than 2 years of observation. Although a subset of immunized and control animals were boosted with SIV(Mne) proteins, no apparent protective benefit was observed. Immunization of macaques with DNA that codes for replication-defective but structurally complete virions appears to protect from or at least delay the onset of AIDS after infection with a pathogenic immunodeficiency virus. With further optimization, this may be a promising approach for vaccine development.

Mucosal challenge of Macaca nemestrina with simian immunodeficiency virus (SIV) following SIV nucleocapsid mutant DNA vaccination.

A simian immunodeficiency virus (SIV)(Mne) DNA clone was constructed that produces viruses containing a four amino acid deletion in the second zinc finger of the nucleocapsid (NC) domain of the Gag polyprotein. Viruses produced from this clone, although non-infectious both in vitro and in vivo, complete a majority of the steps in a single retroviral infection cycle. Eight pig-tailed macaques (Macaca nemestrina) were inoculated intramuscularly and subcutaneously three times over the course of 24 weeks with the NC mutant expressing DNA. These macaques, and four controls, were then challenged mucosally (intrarectally) with the homologous virus (SIV Mne CL E11S) and monitored for evidence of infection and clinical disease. Prior to challenge, a measurable humoral immune response was noted in four of eight immunized macaques. After challenge, all 12 macaques became infected, although four immunized animals greatly restricted their viral replication, and one immunized animal that controlled replication remains antibody negative. No disease has been evidence during the 46-week period of monitoring after challenge.

Containment of simian immunodeficiency virus infection: cellular immune responses and protection from rechallenge following transient postinoculation antiretroviral treatment.

To better understand the viral and host factors involved in the establishment of persistent productive infection by primate lentiviruses, we varied the time of initiation and duration of postinoculation antiretroviral treatment with tenofovir (9-[2-(R)-(phosphonomethoxy)propyl]adenine) while performing intensive virologic and immunologic monitoring in rhesus macaques, inoculated intravenously with simian immunodeficiency virus SIVsmE660. Postinoculation treatment did not block the initial infection, but we identified treatment regimens that prevented the establishment of persistent productive infection, as judged by the absence of measurable plasma viremia following drug discontinuation. While immune responses were heterogeneous, animals in which treatment resulted in prevention of persistent productive infection showed a higher frequency and higher levels of SIV-specific lymphocyte proliferative responses during the treatment period compared to control animals, despite the absence of either detectable plasma viremia or seroconversion. Animals protected from the initial establishment of persistent productive infection were also relatively or completely protected from subsequent homologous rechallenge. Even postinoculation treatment regimens that did not prevent establishment of persistent infection resulted in downmodulation of the level of plasma viremia following treatment cessation, compared to the viremia seen in untreated control animals, animals treated with regimens known to be ineffective, or the cumulative experience with the natural history of plasma viremia following infection with SIVsmE660. The results suggest that the host may be able to effectively control SIV infection if the initial exposure occurs under favorable conditions of low viral burden and in the absence of ongoing high level cytopathic infection of responding cells. These findings may be particularly important in relation to prospects for control of primate lentiviruses in the settings of both prophylactic and therapeutic vaccination for prevention of AIDS.

Isolated hepatic perfusion for lapine liver metastases: impact of hyperthermia on permeability of tumor neovasculature.

BACKGROUND: Hyperthermic isolated hepatic perfusion (IHP) has been shown to cause significant regression of advanced unresectable liver metastases in patients. Although there are different agents and treatment modalities used in IHP, the contribution of perfusion hyperthermia is unknown. PURPOSE: A large animal model of unresectable liver metastases and a technical standard for IHP in this model were established. This model was used to assess the effects of hyperthermia on vascular permeability of tumors and normal liver tissue during IHP. METHODS: Sixty-five New Zealand White rabbits were used in a series of experiments. Disseminated liver tumors were established by direct injection of 1 x 10(6) VX-2 cells into the portal vein by laparotomy in anesthetized animals. Several surgical perfusion techniques were explored to determine a reliable and reproducible IHP model. Vascular permeability in tumor versus liver was then assessed with Evan's Blue labeled bovine albumin under normothermic (tissue temperature 36.5 degrees C +/- 0.5 degree C), moderate hyperthermic (39 degrees C +/- 0.5 degree C), or severe hyperthermic (41 degrees C +/- 0.5 degree C) conditions. RESULTS: Tumor model and perfusion techniques were successfully established with inflow through the portal vein and outflow through an isolated segment of the inferior vena cava. A gravity driven perfusion circuit with stable perfusion parameters and complete vascular isolation was used. Vascular permeability was higher in tumor than in normal tissues (P = .03) at all time points during IHP. Hyperthermia resulted in a significant (up to 5-fold) increase in permeability of neovasculature; when severe hyperthermia was used, tumor vascular permeability was increased even more than normal liver permeability (P = .01). CONCLUSIONS: The VX-2/New Zealand White rabbit system can be used as a reproducible large-animal model for IHP of unresectable liver metastases. It can be used to characterize the contribution and mechanism of action of different treatment parameters used in IHP. Hyperthermia preferentially increases vascular permeability in tumors compared with liver tissue in a dose-dependent fashion, thus providing a mechanism for its presumed benefit during isolated organ perfusion.

Management of a measles outbreak among Old World nonhuman primates.

BACKGROUND AND PURPOSE: A measles outbreak in a facility housing Old World nonhuman primates developed over a 2-month period in 1996, providing an opportunity to study the epidemiology of this highly infectious disease in an animal-handling setting. METHODS: Serum and urine specimens were collected from monkeys housed in the room where the initial measles cases were identified, other monkeys with suspicious measles-like signs, and employees working in the affected areas. Serum specimens were tested for measles virus-specific IgG and IgM antibodies, and urine specimens were tested for measles virus by virus isolation or reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: A total of 94 monkeys in two separate facilities had evidence of an acute measles infection. The outbreak was caused by a wild-type virus that had been associated with recent human cases of acute measles in the United States; however, an investigation was unable to identify the original source of the outbreak. Quarantine and massive vaccination helped to control further spread of infection. CONCLUSIONS: Results emphasize the value of having a measles control plan in place that includes a preventive measles vaccination program involving human and nonhuman primates to decrease the likelihood of a facility outbreak.

The effects of low dietary levels of polyunsaturates on alcohol-induced liver disease in rhesus monkeys.

Rhesus monkeys that were maintained on a diet containing low, yet adequate, amounts of vitamins C and E and in which linoleate and linolenate represented 1.4% and 0.08% of the total caloric intake, respectively, developed liver fibrosis after consuming alcohol (mean, 2.6 g kg(-1) d[-1]) over a period of 3 years. In the liver, several polyunsaturated fatty acids including 18:2n6, 20:4n6, and 22:6n3 decreased compared with dietary controls, and similar findings were also observed in plasma lipoproteins and erythrocytes. The amount of alcohol consumed correlated positively with plasma lipid peroxidation products, 4-hydroxynonenal (4-HNE) and 8-isoprostane F2alpha, and negatively with 20:4n6 and 22:6n3 levels. These findings imply that alcoholics who also have a marginal intake of essential fatty acids and antioxidants in their diets may be at an increased risk of developing liver disease.

Hepatic hemosiderosis in common marmosets, Callithrix jacchus: effect of diet on incidence and severity.

We examined the effect of dietary iron concentration on the incidence of hepatic hemosiderosis in common marmosets (Callithrix jacchus) and assessed the impact of hemosiderosis on animal health. Thirteen young adult common marmosets were fed nutritionally balanced natural-ingredient diets formulated to contain either 100 or 500 ppm of iron. Six were fed the low-iron and seven received the high-iron diet. Baseline blood values and liver iron content were determined for each animal. Animals were weighted monthly, blood work (hematologic analysis, serum iron concentration, total iron-binding capacity, percent of transferrin saturation) was performed semi-annually, and liver biopsies for iron analysis were obtained after marmosets had consumed the test diets for 13 months or at necropsy. Midway in study, the high-iron diet was reformulated to contain 350 ppm of iron because of the death of a male which had consumed that diet for 7 months. Four of seven marmosets fed the high-iron diet died during the first year of the study, compared with one death in the low-iron cohort. The mean increase in liver iron content of the marmosets fed the high-iron diet was 6,371 micrograms/g, dry weight analysis. In contrast the low-iron cohort had a mean decrease of 621.5 micrograms/g. These results indicate that liver iron content can be affected by dietary iron intake. The increased mortality in the marmosets fed the high-iron diet also suggests that hepatic hemosiderosis can be detrimental to marmoset health.

Diffuse hepatic uptake of technetium-99m methylene diphosphonate in a patient receiving high dose methotrexate.

A child with diffuse accumulation of [99mTc]MDP in the liver on a bone scan, at the time of study the patient had a severe, but reversible, hepatic dysfunction on the basis of methotrexate toxicity. Visualization of the liver on skeletal scintigrams can be a consequence of high-dose methotrexate therapy, as there was no other explanation for this unusual finding.

Radionuclide cisternography in the diagnosis and management of cerebrospinal fluid leaks: the test of choice.

While leakage of cerebrospinal fluid is an intermittent and usually short-lived phenomenon, it may be fatal. The difficulty of making this diagnosis has led to the adoption of many diagnostic procedures. Fifteen patients have been studied by radionuclide cisternography with the concomitant use of nasal pledgets. Six of the studies showed cerebrospinal fluid leakage; the sensitivity of the technique was 100%. The site of leakage was confirmed surgically in three of the patients. No other technique offers comparable sensitivity with high patient acceptance and low morbidity.