Rev-independent expression of synthetic gag-pol genes of human immunodeficiency virus type 1 and simian immunodeficiency virus: implications for the safety of lentiviral vectors

The safety of lentiviral vectors for clinical applications is still a major concern. The gag-pol expression plasmids and the lentiviral vectors used in previous studies contain homologous regions, which constitute a risk for recombination events. Synthetic gag-pol genes of human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV) were therefore constructed, in which the codon usage was optimized for expression in human cells without altering the amino acid sequences. The synthetic gag-pol genes allowed efficient expression of these genes in the absence of Rev and the 5' untranslated leader region. Both the HIV-1 and the SIV synthetic gag-pol expression plasmids could mediate transduction of an SIV vector into nondividing human cells with titers of about 10(6) transducing units/ml. Similar titers were obtained with a four-plasmid vector-packaging system based on HIV-1. Using a biological assay, homologous recombination events between the synthetic gag-pol expression plasmids and an SIV vector were undetectable and in comparison with a previously used gag-pol expression plasmid at least approximately 100-fold less frequent. By eliminating regions of homology and sequences involved in packaging, synthetic gag-pol genes should improve the safety profile of lentiviral vectors.

Low level of cross-resistance to amprenavir (141W94) in samples from patients pretreated with other protease inhibitors

The therapeutic success of an antiretroviral salvage regimen containing protease inhibitors (PI) is limited by PI-resistant viral strains exhibiting various degrees of resistance and cross-resistance. To evaluate the extent of cross-resistance to the new PI amprenavir, 155 samples from 132 human immunodeficiency virus type 1-infected patients were analyzed for viral genotype by direct sequencing of the protease gene. Concomitantly, drug sensitivity to indinavir, saquinavir, ritonavir, nelfinavir, and amprenavir was analyzed by a recombinant virus assay. A total of 111 patients had been pretreated with 1-4 PI, but all were naive to amprenavir. A total of 105 samples (67.7%) were sensitive to amprenavir; 25 samples (16.1%) were intermediately resistant, and another 25 samples were highly resistant (4- to 8-fold- and >8-fold-reduced sensitivity, respectively). The mutations 46I/L, 54L/V, 84V, and 90M showed the strongest association with amprenavir resistance (P < 0. 0001). The scoring system using 84V and/or any two of a number of mutations (10I/R/V/F, 46I/L, 54L/V, and 90M) predicted amprenavir resistance with a sensitivity of 86.0% and a specificity of 81.0% within the analyzed group of samples. Of 62 samples with resistance against 4 PI, 23 (37.1%) were still sensitive to amprenavir. In comparison, only 2 of 23 samples (8.7%) from nelfinavir-naive patients with resistance against indinavir, saquinavir, and ritonavir were still sensitive to nelfinavir. Amprenavir thus appears to be an interesting alternative for PI salvage therapy.

Simple algorithm derived from a geno-/phenotypic database to predict HIV-1 protease inhibitor resistance

BACKGROUND

Resistance against protease inhibitors (PI) can either be analysed genotypically or phenotypically. However, the interpretation of genotypic data is difficult, particularly for PI, because of the unknown contributions of several mutations to resistance and cross-resistance.

OBJECTIVE

Development of an algorithm to predict PI phenotype from genotypic data.

METHODS

Recombinant viruses containing patient-derived protease genes were analysed for sensitivity to indinavir, saquinavir, ritonavir and nelfinavir. Drug resistance-associated mutations were determined by direct sequencing. geno- and phenotypic data were compared for 119 samples from 97 HIV-1 infected patients.

RESULTS

Samples with one or two mutations in the gene for the protease were phenotypically sensitive in 74.3%, whereas 83.6% of samples with five or more mutations were resistant against all PI tested. Some mutations (361, 63P, 71V/T, 771) were frequent both in sensitive and resistant samples, whereas others (241, 30N, 461/L, 48V, 54V, 82A/F/T/S, 84V, 90M) were predominantly present in resistant samples. Therefore, the presence or absence of a single drug resistance-associated mutation predicted phenotypic PI resistance with high sensitivity (96.5-100%) but low specificity (13.3-57.4%). A more specific algorithm was obtained by taking into account the total number of drug resistance-associated mutations in the gene for the protease and restricting these to certain key positions for the PI. The algorithm was subsequently validated by analysis of 72 independent samples.

CONCLUSION

With an optimized algorithm, phenotypic PI resistance can be predicted by viral genotype with good sensitivity (89.1-93.0%) and specificity (82.6-93.3%). The reliability and relevance of this algorithm should be further evaluated in clinical practice.

Suppression of acute viremia by short-term postexposure prophylaxis of simian/human immunodeficiency virus SHIV-RT-infected monkeys with a novel reverse transcriptase inhibitor (GW420867) allows for development of potent antiviral immune responses resulting in efficient containment of infection

A nonnucleoside reverse transcriptase (RT) inhibitor, GW420867, was tested for postexposure prophylaxis (PEP) in rhesus macaques experimentally infected with 100 50% tissue culture infective doses of a chimeric simian/human immunodeficiency virus (SHIV) containing the RT gene of HIV-1 (SHIV-RT). Animals were either mock treated, or treated for 4 weeks starting at 8 or 24 h postinfection (p.i.) with GW420867. While such therapy led to undetectable plasma viremia in three of six monkeys, a transient plasma viremia was noted in the other three treated animals at 2 to 4 weeks following cessation of therapy. Following this transient viremia all drug-treated animals showed low or undetectable levels of plasma viremia up to the last sample examined at 90 weeks p.i. Despite low and/or undetectable viremia, virus-specific cytotoxic T lymphocyte and viral Env-specific proliferative responses were seen in the peripheral blood mononuclear cells of both mock- and drug-treated animals as early as 3 weeks p.i. Such virus-specific cellular responses, however, were better maintained in the drug-treated animals than the mock-treated animals. In contrast to the virus-specific cellular response, the magnitude and kinetics of virus specific humoral responses appeared to correlate with the detection of viremia. These data support the view that a short-term PEP with GW420867 permits the generation and maintenance of long-lasting virus-specific cell-mediated immune responses while markedly reducing viral loads to undetectable levels for a prolonged period of time (90 weeks) and leads to long-term disease protection. This model provides a unique means to define mechanisms and correlates of disease protection.

Evidence for recombination of live, attenuated immunodeficiency virus vaccine with challenge virus to a more virulent strain

Live, attenuated immunodeficiency virus vaccines, such as nef deletion mutants, are the most effective vaccines tested in the simian immunodeficiency virus (SIV) macaque model. In two independent studies designed to determine the breadth of protection induced by live, attenuated SIV vaccines, we noticed that three of the vaccinated macaques developed higher set point viral load levels than unvaccinated control monkeys. Two of these vaccinated monkeys developed AIDS, while the control monkeys infected in parallel remained asymptomatic. Concomitant with an increase in viral load, a recombinant of the vaccine virus and the challenge virus could be detected. Therefore, the emergence of more-virulent recombinants of live, attenuated immunodeficiency viruses and less-aggressive wild-type viruses seems to be an additional risk of live, attenuated immunodeficiency virus vaccines.

Development of a self-inactivating, minimal lentivirus vector based on simian immunodeficiency virus

In contrast to oncoviruses, lentiviruses do not require target cell division for integration into the host genome. Lentiviral vectors can therefore expand the spectrum of target cells susceptible to retroviral gene transfer. To analyze whether vectors based on simian immunodeficiency viruses (SIVs) could be used for gene transfer, a three-plasmid vector-packaging system was developed, in which Gag-Pol and the vector itself are of SIV origin, while Env is derived either from SIV, amphotropic murine leukemia virus (MuLV), or the G glycoprotein of vesicular stomatitis virus (VSV-G). To increase the safety of the SIV vector system, a self-inactivating SIV vector was constructed. After optimization of the SIV gag-pol expression plasmid, a minimal SIV vector, which contained only SIV sequences present on the multiply spliced nef transcript, could still be produced at titers of 2 x 10(5) infectious units/ml. Growth-arrested cells could be transduced with this vector even if vif, vpr, vpx, and nef had been deleted from the packaging construct and the vector.

Antiretroviral therapy during primary immunodeficiency virus infection can induce persistent suppression of virus load and protection from heterologous challenge in rhesus macaques

A limited period of chemotherapy during primary immunodeficiency virus infection might provide a long-term clinical benefit even if treatment is initiated at a time point when virus is already detectable in plasma. To evaluate this strategy, we infected rhesus macaques with the pathogenic simian/human immunodeficiency virus RT-SHIV and treated them with the antiretroviral drug (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA) for 8 weeks starting 7 or 14 days postinfection. PMPA treatment suppressed viral replication efficiently in all of the monkeys. After chemotherapy ended, virus replication rebounded and viral RNA in plasma reached levels comparable to that of the controls in four of the six monkeys. However, in the other two animals, virus loads peaked only moderately after withdrawal of the drug and then declined to low or even undetectable levels. These low levels of viremia remained stable for at least 31 weeks after cessation of therapy. At this time point, these two monkeys were challenged with SIV(8980) to evaluate whether the host responses which were able to keep RT-SHIV replication under control were also sufficient to protect against infection with a highly pathogenic heterologous virus. Both monkeys proved to be protected against the heterologous virus. In one of the two animals, low levels of SIV(8980) replication were detected. Thus, by chemotherapy during the acute phase of pathogenic virus replication, we could achieve not only persistent virus load suppression in two out of six monkeys but also protection from subsequent heterologous challenge. By this chemotherapeutic attenuation, the replication kinetics of attenuated viruses could be mimicked and a vaccination effect similar to that induced by live attenuated simian immunodeficiency virus vaccines was achieved.

Design elements for a computerized patient record

Computerized medical record systems have to present user- and problem-oriented views of a patient record to health-care professionals. Presentation and manipulation of data must be easily adaptable to current and future demands of medical specialties and specific settings. During the definition, development and evaluation of a prototype of a computerized patient record system, design elements were elaborated to support physicians and other health-care professionals. Our approach shows a high degree of flexibility and adaptability to specific needs, problem orientation and connectivity to other systems, via a hospital information network. The explicit description of the contents of a patient record allows to augment the number of items that can be recorded without modifying the data structure. New views on patient data can be added to the system without interfering with the routine use of the system. Application in several medical specialties proved the feasibility of our prototype.

An anti-HIV strategy combining chemotherapy and therapeutic vaccination

Combination chemotherapy using potent anti-retroviral agents has led to significant advances in the clinical management of human immunodeficiency virus (HIV) disease. However, the emergence of multiple drug-resistant mutants, the high need for compliance to adhere to demanding drug-dosing schemes, and the remaining toxic side-effects of drugs make the perspective of life-long treatment unattractive and possibly unrealistic. Therefore, means must be sought to shorten the time span during which treatment is necessary. Such means could be to stimulate an efficient immune response during the period of low virus load and restored CD4 + cell levels, which might be capable of keeping the virus under long-lasting control after treatment is stopped. Here we tested this concept of combined chemotherapy/ therapeutic vaccination in a non-human primate model. Rhesus macaques chronically infected with the chimeric simian/human immunodeficiency virus (SHIV) containing the HIV type 1 (HIV-1) HXBc2 gene for reverse transcriptase (RT) in the genomic background of simian immunodeficiency virus (SIV)(mac239) (RT-SHIV) were treated with (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA), a potent anti-HIV drug. When virus load had decreased significantly, we immunized with SIV genes env, gag/pol, rev, tat, and nef inserted in two different expression vector systems. Four weeks after the second immunization, drug treatment was stopped. Animals were monitored to determine if virus load stayed low or if it increased again to the original levels and if CD4+ T-cell levels remained stable. Humoral and cellular immune responses were also measured. This combined chemotherapy/ therapeutic vaccination regimen induced a significant reduction in the steady-state level of viremia in one out of two chronically infected rhesus macaques. Chemotherapeutic treatment alone did not achieve reduction of viremia in two chronically infected animals. The nature of the immune responses assumed to have been induced by vaccination in one out of the two monkeys remains to be elucidated.

Rapid, phenotypic HIV-1 drug sensitivity assay for protease and reverse transcriptase inhibitors

BACKGROUND

Development of drug resistance is one of the major reasons for the failure of antiretroviral therapy of HIV-1 infection. Knowing the drug sensitivity-resistance profile of viruses present in a patient prior to treatment or change in treatment could help to optimize therapy.

OBJECTIVE

Development of a rapid standardized phenotypic HIV-1 drug sensitivity assay for protease (PR) and reverse transcriptase (RT) inhibitors.

DESIGN

The PR gene (codons 1-99) and the 5' part of the RT gene (codons 1-300) of HIV-1 is amplified from the plasma of infected individuals by RT-PCR and ligated into a proviral clone of HIV-1 containing a deletion of the PR gene and the 5' part of the RT gene. Bacteria are transformed with the ligation product and plasmid DNA is prepared from a library of transformed bacteria. The plasmid DNA is transfected into 293 T cells and recombinant virus is harvested from the supernatant of the transfected cells 2 days after transfection. The sensitivity of the recombinant virus is determined with the help of a sensitive indicator cell line.

RESULTS

Recombinant viruses were generated with high efficiency. Determination of the drug sensitivity of the recombinant viruses with an indicator cell line was highly reproducible. The recombinant viruses accurately reflected the sensitivity-resistance profile of the parental viruses. The phenotypic drug sensitivity determined by this assay correlated well with the treatment history of patients.

CONCLUSION

This assay system should allow rapid, high-throughput analyses of phenotypic HIV-1 drug sensitivity for PR and RT inhibitors. Due to the efficient generation of recombinant viruses, propagation of the recombinant viruses in cell culture is not required prior to the determination of the sensitivity of the recombinant viruses. The risk of selecting fitter non-resistant viruses due to culture conditions is minimized.

A pathogenic threshold of virus load defined in simian immunodeficiency virus- or simian-human immunodeficiency virus-infected macaques

To determine if a specific pathogenic threshold of plasma viral RNA could be defined irrespective of virus strain, RNA levels in the plasma of more than 50 infected rhesus macaques (Macaca mulatta) were measured. Animals were inoculated intravenously with either simian immunodeficiency virus (SIV) or simian-human immunodeficiency virus (SHIV) strains of known pathogenic potential (SIV8980, SIVsmm-3, SIVmac32H/J5, SIVmac32H/1XC, reverse transcriptase-SHIV, SHIV89.6p) or with attenuated strains (SHIVW6.1D, SHIVsf13, SHIVhan-2, SIVmacDeltanef, SHIVsf33). In animals inoculated with nonpathogenic strains, shortly after the primary peak of viremia viral RNA levels declined and remained below 10(4) RNA equivalents/ml of plasma between 6 and 12 weeks postinoculation. Animals infected with documented pathogenic strains maintained viral RNA levels higher than 10(5) RNA equivalents/ml of plasma. In animals infected with strains with low virulence, a decline in plasma RNA levels was observed, but with notable individual variation. Our results demonstrate that the disease-causing potential was predicted and determined by a threshold plasma virus load which remained greater than 10(5) RNA equivalents/ml of plasma 6 to 12 weeks after inoculation. A threshold virus load value which remained below 10(4) RNA equivalents/ml of plasma was indicative of a nonpathogenic course of infection.

Env-independent protection induced by live, attenuated simian immunodeficiency virus vaccines

Live attenuated simian immunodeficiency viruses (SIV), such as nef deletion mutants, are the most effective vaccines tested in the SIV-macaque model so far. To modulate the antiviral immune response induced by live attenuated SIV vaccines, we had previously infected rhesus monkeys with a nef deletion mutant of SIV expressing interleukin 2 (SIV-IL2) (B. R. Gundlach, H. Linhart, U. Dittmer, S. Sopper, S. Reiprich, D. Fuchs, B. Fleckenstein, G. Hunsmann, S. Stahl-Hennig, and K. Uberla, J. Virol. 71:2225-2232, 1997). In the present study, SIV-IL2-infected macaques and macaques infected with the nef deletion mutant SIVDeltaNU were challenged with pathogenic SIV 9 to 11 months postvaccination. In contrast to the results with naive control monkeys, no challenge virus could be isolated from the SIV-IL2- and SIVDeltaNU-infected macaques. However, challenge virus sequences could be detected by nested PCR in some of the vaccinated macaques. To determine the role of immune responses directed against Env of SIV, four vaccinated macaques were rechallenged with an SIV-murine leukemia virus (MLV) hybrid in which the env gene of SIV had been functionally replaced by the env gene of amphotropic MLV. All vaccinated macaques were protected from productive infection with the SIV-MLV hybrid in the absence of measurable neutralizing antibodies, while two naive control monkeys were readily infected. Since the SIV-MLV hybrid uses the MLV Env receptor Pit2 and not CD4 and a coreceptor for virus entry, chemokine inhibition and receptor interference phenomena were not involved in protection. These results indicate that the protective responses induced by live attenuated SIV vaccines can be independent of host immune reactions directed against Env.

Specificity of helper T-cells generated from macaques infected with attenuated simian immunodeficiency virus

Deletion of the simian immunodeficiency virus (SIV) nef gene leads to an attenuated virus phenotype in vivo. We have previously shown that these viruses induce a potent cellular immune response in macaques. To extend these studies, we established virus-specific short-term T-cell lines from four rhesus macaques infected with a nef deletion mutant of SIV. These T-cell lines proliferated upon restimulation with whole SIV or SIV gp140 antigen in vitro. The proliferating cells were characterized as CD4+ helper T-cells (TH) and their antigen recognition was MHC class II DR-restricted. After antigenic stimulation, they transcribed mRNA for various TH1- and TH2-like cytokines. Using these SIV-specific cell lines, a variety of helper T-cell epitopes in the SIV Env protein were determined with overlapping peptides. TH epitopes were identified throughout the whole SIV Env including both constant and variable regions. Although the recognition of TH epitopes was heterogeneous among different animals, five more broadly reactive T-cell epitopes were identified. As expected, recognition was associated with the MHC class II DRB background of the animals. This is the first report on helper T-cell epitopes in SIV-infected monkeys. Such studies should be of considerable significance for AIDS/ vaccine research.

Simian immunodeficiency virus variants with differential T-cell and macrophage tropism use CCR5 and an unidentified cofactor expressed in CEMx174 cells for efficient entry

The recent identification of coreceptors that mediate efficient entry of human immunodeficiency virus type 1 (HIV-1) suggests new therapeutic and preventive strategies. We analyzed simian immunodeficiency virus (SIV) entry cofactors to investigate whether the macaque SIV model can be used as an experimental model to evaluate these strategies. Similar to primary HIV-1 isolates, a well-characterized molecular clone, SIVmac239, which replicates poorly but efficiently enters into rhesus alveolar macrophages and an envelope variant, SIVmac239/316Env, with an approximately 1,000-fold-higher replicative capacity in macrophages used the beta-chemokine receptor CCR5 for efficient entry. The transmembrane portion of 316Env allowed low-level entry into cells expressing CCR1, CCR2B, and CCR3. A single amino acid substitution in the V3 loop of SIVmac239/316Env, 321P-->S, impaired the ability to enter into the T-B hybrid cell line CEMx174 but had relatively little effect on entry into primary cells and HOS.CD4 cells expressing CCR5. Although CEMx174 cells do not express CCR5, most SIVmac variants entered this hybrid cell line efficiently but did not enter the parental T-cell line CEM. It seems likely that CEMx174 cells express an as-yet-unidentified, perhaps B-cell-derived cofactor which allows efficient entry of SIVmac.

Live attenuated SIV vaccines are not effective in a postexposure vaccination model

Live attenuated simian immunodeficiency virus (SIV) vaccines, like nef deletion mutants, have been the most effective vaccines tested in the SIV/macaque model so far. The efficacy of live attenuated SIV vaccines in therapeutic vaccination and postexposure prophylaxis has not been determined. Inoculation of macaques with a pathogenic challenge virus and an attenuated SIV vaccine at the same time mimics postexposure vaccination, whereby vaccination with the attenuated virus is performed as rapidly as possible after exposure to pathogenic SIV. In the study presented here, four rhesus macaques were coinfected with pathogenic SIV and a nearly 3000-fold excess of a nef deletion mutant of SIV. Four macaques received pathogenic SIV and an approximately 200-fold excess of a nef deletion mutant expressing interleukin 2 (IL-2). The IL-2-expressing SIV had been previously constructed to enhance the immunogenicity of live attenuated SIV vaccines. All coinfected macaques had a high viral load, and some of them developed AIDS-like symptoms and pathological alterations rapidly. In the presence of pathogenic SIV, both live attenuated SIV vaccines did not protect from disease in this postexposure vaccination model.

SIV/HIV-1 hybrid virus expressing the reverse transcriptase gene of HIV-1 remains sensitive to HIV-1-specific reverse transcriptase inhibitors after passage in rhesus macaques

We have previously described an animal model for the therapy of human immunodeficiency virus type 1 (HIV-1) infection with HIV-1-specific reverse transcriptase (RT) inhibitors based on a simian immunodeficiency virus (SIV), in which the RT gene of SIV was replaced by the RT gene of HIV-1. In vitro, replication of the hybrid virus, RT-SHIV, was delayed compared with parental SIV. RT-SHIV could induce AIDS-like symptoms and pathologic alterations in rhesus macaques. Characterization of re-isolates recovered from RT-SHIV-infected macaques one-half year after infection revealed that the re-isolates replicated with kinetics similar to those of SIV. Inefficient processing of the Gag-Pol precursor of RT-SHIV may be one reason for the retarded growth of RT-SHIV, because the protease cleavage site between the protease gene and the RT gene was frequently mutated in the RT-SHIV re-isolates. Adaptation of RT-SHIV to the growth in macaques did not result in a relevant loss of sensitivity to nonnucleoside RT inhibitors (NNRTIs). However, because a minor sub-population of the RT-SHIV re-isolates contained a mutation conferring low-level resistance to ddI and ddC, the RT-SHIV/macaque model may underestimate the efficacy of these drugs. Nevertheless, this report further supports the suitability, reliability, and usefulness of the RT-SHIV/macaque model to investigate the antiviral properties of most RT inhibitors in an in vivo setting.

Maternal smoking during pregnancy and lactation increases the risk for atopic eczema in the offspring

BACKGROUND

Maternal smoking during pregnancy has been shown to lead to immunologic changes in the offspring. However, little is known about the influence of this exposure on atopic manifestations.

OBJECTIVE

Our purpose was to investigate the influence of air pollutants on manifestations of atopy in preschool children.

METHODS

Unselected cohorts of a total of 678 5- to 6-year-old preschool children (350 boys, 328 girls) were investigated in areas with different degrees of air pollution in Bavaria. Data on the history of atopic diseases and other relevant factors were obtained by questionnaire. A skin-prick test was performed with common aeroallergens. Manifestation of atopy was defined as personal history of atopic disease or positive prick test to either grass pollen, house dust mite, or cat and analyzed multivariately.

RESULTS

Of all children, 38.9% exhibited at least one manifestation of atopy. Atopic eczema was reported in 7.9% to 15.5%, hayfever in 4.1% to 25.6%, and asthma in 3.0% to 8.1%. Of the mothers, 12.6% smoked during pregnancy or lactation or both. Analysis of the manifestation of atopy including sex, location, nitrogen oxide and sulfur dioxide exposure and maternal smoking as covariates revealed an influence of the maternal smoking during pregnancy/lactation. Of children whose mothers had smoked during pregnancy/lactation, 52.2% exhibited manifestations of atopy in contrast to 35.7% of children of nonsmoking mothers (p < 0.044). A history of atopic eczema was the only component of the variable "manifestation of atopy" that was significantly associated with maternal smoking during pregnancy and lactation. A causal interpretation of this finding, however, was not supported by a follow-up study.

CONCLUSION

Maternal smoking during pregnancy or lactation or both might play a role in the development of atopic eczema and should be avoided.

Replication-competent chimeric lenti-oncovirus with expanded host cell tropism

Baboon bone marrow was grafted into human immunodeficiency virus type 1-infected patients in the course of recent trials for AIDS treatment. Since the baboon genome harbors multiple copies of an endogenous oncovirus, chimeric lenti-oncoviruses could emerge in the xenotransplant recipient. To analyze the potential replication competence of hybrid viruses between different genera of retroviruses, we replaced most of the env gene of simian immunodeficiency virus with the env gene of an amphotropic murine leukemia virus. The hybrid virus could be propagated in human T-cell lines, in peripheral blood mononuclear cells of rhesus macaques, and in CD4- B-cell lines. Because of the expanded cell tropism, the hybrid virus might have a selective advantage in comparison to parental viruses. Therefore, emerging chimeric viruses may be considered a serious risk of xenotransplantation. A note of caution is also suggested for the use of pseudotyped lentiviral vectors for human gene therapy.

Construction, replication, and immunogenic properties of a simian immunodeficiency virus expressing interleukin-2

To study the effect of interleukin-2 (IL-2) on simian immunodeficiency virus (SIV) replication, pathogenesis, and immunogenicity, we replaced the nef gene of SIVmac239 by the IL-2 coding region. The virus, designated SIV-IL2, stably expressed high levels of IL-2 in cell culture. In comparison to SIVmac239, SIV-IL2 replicated more efficiently in peripheral blood mononuclear cells in the absence of exogenously added IL-2. To determine whether this growth advantage would be of relevance in vivo, four juvenile rhesus monkeys were infected with SIV-IL2 and four monkeys were infected with a nef deletion mutant of SIV (SIVdeltaNU). After a peak in the cell-associated viral load 2 weeks postinfection, the viruses could barely be isolated 3 to 7 months postinfection. Mean capsid antigen levels were higher in the SIV-IL2 group than in the nef deletion group 2 weeks postinfection. Viruses reisolated from the SIV-IL2-infected animals expressed high levels of IL-2 during the acute phase of infection. Deletions in the IL-2 coding region of SIV-IL2 were observed in two of the SIV-IL2-infected macaques 3 months postinfection. Urinary neopterin levels, a marker for unspecific immune stimulation, were higher in the SIV-IL2-infected macaques than in SIVdeltaNU-infected animals during the acute phase of infection. The SIV-specific T-cell-proliferative response and antibody titers were similar in both groups. Cytotoxic T cells directed against viral antigens were detected in all SIV-IL2-infected macaques and in two of the SIVdeltaNU-infected animals. Expression of IL-2 did not seem to alter the attenuated phenotype of nef deletion mutants fundamentally, although there might have been a slight increase in virus replication and immune stimulation during the acute phase of infection. Deletion of the viral IL-2 gene 3 months postinfection could be a consequence of a selective disadvantage due to local coexpression of viral antigen and IL-2 in the presence of an antiviral immune response.

Early institution of bromocriptine in Parkinson's disease inhibits the emergence of levodopa-associated motor side effects. Long-term results of the PRADO study

Long-term levodopa treatment in Parkinson's disease is typically associated with "motor side effects" consisting in dyskinesias and/or fluctuations in motility referred to as the on-off phenomena. The main objective of this prospective, randomized, multi-centre study was to determine to what extent the development of such complications could be prevented by partial substitution of levodopa monotherapy (L-DOPA/benserazide) by bromocriptine in patients with early symptoms of the disease. The basic trial population included 674 newly diagnosed Parkinsonian patients that were randomly allocated to monotherapy with levodopa or a combination therapy based upon a nearly 40% replacement of levodopa by bromocriptine. The two target regimens had to be consistently maintained for 42 months. Parkinsonian symptoms were assessed by means of the Webster rating scale, the Hoehn and Yahr scale, and the Zung Self-Rating Depression scale. Motor side effects and adverse events were recorded at each regular clinic visit. Neurological symptoms improved and stabilized in a similar manner during treatment with both regimens throughout the study period. Motor side effects were observed in more patients on levodopa alone than on combination therapy (28.8 vs 20%; p = 0.008). According to Kaplan-Meier estimates the cumulative probability of experiencing motor side effects was 0.43 on monotherapy, compared to 0.28 on combination therapy, which was equal to a one third reduction of risk (p = 0.025). In regard to motor side effects, the degree of substitution of levodopa proved relevant: patients with > 50% substitution by bromocriptine exhibited half the risk observed in those with < 30% (p = 0.045). The overall burden of motor side effects, as reflected by a sum score based upon the relevance, the severity and the extent of motor dysfunction, was also significantly less on combination therapy (p = 0.046). In conclusion, partial substitution of levodopa by bromocriptine (> 30%) as first-line treatment of Parkinson's disease proves active in the prophylaxis of levodopa associated motor side effects. Early combination therapy therefore extends the period of optimal disease control.

Improved outcome in adult B-cell acute lymphoblastic leukemia

A total of 68 adult patients with B-cell acute lymphoblastic leukemia (B-ALL) were treated in three consecutive adult multicenter ALL studies. The diagnosis of B-ALL was confirmed by L3 morphology and/or by surface immunoglobulin (Slg) expression with > 25% blast cell infiltration in the bone marrow (BM). They were characterized by male predominance (78%) and a median age of 34 years (15 to 65 y) with only 9% adolescents (15 to 20 y), but 28% elderly patients (50 to 65 y). The patients received either a conventional (N = 9) ALL treatment regimen (ALL study 01/81) or protocols adapted from childhood B-ALL with six short, intensive 5-day cycles, alternately A and B. In study B-NHL83 (N = 24) cycle A consisted of fractionated doses of cyclophosphamide 200 mg/m2 for 5 days, intermediate-dose methotrexate (IdM) 500 mg/m2 (24 hours), in addition to cytarabine (AraC), teniposide (VM26) and prednisone. Cycle B was similar except that AraC and VM26 were replaced by doxorubicin. Major changes in study B-NHL86 (N = 35) were replacement of cyclophosphamide by ifosphamide 800 mg/m2 for 5 days, an increase of IdM to high-dose, 1,500 mg/m2 (HdM) and the addition of vincristine. A cytoreductive pretreatment with cyclophosphamide 200 mg/m2, and prednisone 60 mg/m2, each for 5 days was recommended in study B-NHL83 for patients with high white blood cell (WBC) count (> 2,500/m2) or large tumor burden and was obligatory for all patients in study B-NHL86. Central nervous system (CNS) prophylaxis/treatment consisted of intrathecal methotrexate (MTX) therapy, later extended to the triple combination of MTX, AraC, and dexamethasone, and a CNS irradiation (24 Gy) after the second cycle. Compared with the ALL 01/81 study where all the patients died, results obtained with the pediatric protocols B-NHL83 and B-NHL86 were greatly improved. The complete remission (CR) rates increased from 44% to 63% and 74%, the probability of leukemia free survival (LFS) from 0% to 50% and 71% (P = .04), and the overall survival rates from 0% to 49% and 51% (P = .001). Toxicity, mostly hematotoxicity and mucositis, was severe but manageable. In both studies B-NHL83 and B-NHL86, almost all relapses occurred within 1 year. The time to relapse was different for BM, 92 days, and for isolated CNS and combined BM and CNS relapses, 190 days (P = .08). The overall CNS relapses changed from 50% to 57% and 17%, most probably attributable to the high-dose MTX and the triple intrathecal therapy. LFS in studies B-NHL83 and B-NHL86 was significantly influenced by the initial WBC count < or > 50,000/microL, LFS 71% versus 29% (P = .003) and hemoglobin value > or < 8 g/dL, LFS 67% versus 27% (P = .02). Initial CNS involvement had no adverse impact on the outcome. Elderly B-ALL patients (> 50 years) also benefited from this treatment with a CR rate of 56% and a LFS of 56%. It is concluded that this short intensive therapy with six cycles is effective in adult B-ALL. HdM and fractionated higher doses of cyclophosphamide or ifosphamide seem the two major components of treatment.

Animal model for the therapy of acquired immunodeficiency syndrome with reverse transcriptase inhibitors

The reverse transcriptase (RT) of the human immunodeficiency virus type 1 (HIV-1) is the major target for antiretroviral therapy of the acquired immunodeficiency syndrome (AIDS). While some inhibitors exhibit activity against most retroviral RTs, others are specific for the HIV-1 enzyme. To develop an animal model for the therapy of the HIV-1 infection with RT inhibitors, the RT of the simian immunodeficiency virus (SIV) was replaced by the RT of HIV-1. Macaques infected with this SIV/HIV-1 hybrid virus developed AIDS-like symptoms and pathology. The HIV-1-specific RT inhibitor LY300046.HCl, but not zidovudine [3'-azido-3'-deoxythymidine (AZT)] delayed the appearance of plasma antigenemia in macaques infected with a high dose of the chimeric virus. Infection of macaques with the chimeric virus seems to be a valuable model to study the in vivo efficacy of new RT inhibitors, the emergence and reversal of drug resistance, the therapy of infections with drug-resistant viruses, and the efficacy of combination therapy.

Sensitivity/resistance profile of a simian immunodeficiency virus containing the reverse transcriptase gene of human immunodeficiency virus type 1 (HIV-1) toward the HIV-1-specific non-nucleoside reverse transcriptase inhibitors

To develop an animal model for the therapy of AIDS with human immunodeficiency virus type 1 (HIV-1)-specific reverse transcriptase (RT) inhibitors, we recently constructed a hybrid simian immunodeficiency virus (SIV)/HIV-1 in which the RT gene of SIV was replaced by the RT gene of HIV-1. This chimaeric virus, designated RT-SHIV, was found to be markedly sensitive to the inhibitory effects of both nucleoside (ddN) and non-nucleoside RT inhibitors (NNRTIs). In contrast, SIV was inhibited only by ddNs (i.e., 3TC and AZT), but not NNRTIs. When RT-SHIV was grown in the presence of 3TC, nevirapine, TSAO-m3T or the thiocarboxanilide UC-42 drug-resistant mutant virus strains emerged in cell culture as rapid as for HIV-1(IIIB). The antiviral sensitivity/resistance spectrum of the mutant RT-SHIV strains against NNRTIs and ddNs, and the nature of the mutations that appeared in their RT were similar to those of the mutant HIV-1 strains that were selected under identical experimental conditions. Infection of macaques with RT-SHIV may be a useful tool for studying the mechanism of NNRTI-resistance development and the therapy of NNRTI-resistant viruses in an animal model.