Backround. Recent advances in gene transfer technology render gene therapy an attractive treatment of disseminated liver metastases for which other treatments remain disappointing. In this setting, total vascular exclusion of the liver could improve gene transfer to cancer cells and prevent extrahepatic vector spreading during portal infusion of therapeutic genes. We evaluate the efficiency of combined herpes simplex virus type-1 thymidine kinase (HSV1-TK) and interleukin-2 retrovirus-mediated gene transfer through the portal vein, under total vascular exclusion of the liver, in a model of macroscopic multiple liver metastases in rats. Methods. Multifocal liver metastases were established in BDIX rats with intraportal injection of DHDK12 colon cancer cells. On randomization, rats received either vector-producing cells or saline solution under total vascular exclusion of the liver. Vector-producing cells released retroviral vectors encoding Lac-Z in marking studies or HSV1-TK or interleukin-2 in therapeutic studies. Rats were either killed for pathologic studies, or followed for survival. Results. Total vascular exclusion of the liver markedly improved gene transfer efficacy in marking studies. In therapeutic studies we observed a significant reduction in tumor volume of treated rats compared with untreated controls (2170 ± 310 mm3). Although singular HSV1-TK or interleukin-2 gene transfer showed significant efficacy, the greatest tumor volume regression was observed in rats treated with combined HSV1-TK + interleukin-2 gene therapy (145 ± 60 mm3; P =.0001 vs control). This translated into an increased median survival rate compared with either control rats (P =.006) or rats treated with single gene therapy. Conclusion. In a rat model, a significant antitumoral effect against macroscopic multifocal liver metastases can be observed after retrovirus-mediated HSV1-TK and interleukin-2 gene transfer through the portal vein under total vascular exclusion of the liver, followed by ganciclovir administration. We believe that this well-tolerated and efficient therapeutic approach deserves clinical evaluation in patients with disseminated colorectal liver metastases. (Surgery 2003;133:669-77)

The autosomal dominant mutation causing myotonic dystrophy (DM1) is a CTG repeat expansion in the 3'-UTR of the DM protein kinase (DMPK) gene. This multisystemic disorder includes myotonia, progressive weakness and wasting of skeletal muscle and extramuscular symptoms such as cataracts, testicular atrophy, endocrine and cognitive dysfunction. The mechanisms underlying its pathogenesis are complex. Recent reports have revealed that DMPK gene haploinsufficiency may account for cardiac conduction defects whereas cataracts may be due to haploinsufficiency of the neighboring gene, the DM-associated homeobox protein (DMAHP or SIX5) gene. Furthermore, mice expressing the CUG expansion in an unrelated mRNA develop myotonia and myopathy, consistent with an RNA gain of function. We demonstrated that transgenic mice carrying the CTG expansion in its human DM1 context (>45 kb) and producing abnormal DMPK mRNA with at least 300 CUG repeats, displayed clinical, histological, molecular and electrophysiological abnormalities in skeletal muscle consistent with those observed in DM1 patients. Like DM1 patients, these transgenic mice show abnormal tau expression in the brain. These results provide further evidence for the RNA trans-dominant effect of the CUG expansion, not only in muscle, but also in brain.

The herpes simplex virus type 1 thymidine kinase suicide gene (HSV1tk) together with ganciclovir (GCV) have been successfully used for in vivo treatment of various experimental tumors, and many clinical trials using this system have been launched. With the aim to improve this therapeutic system, we compared the potential efficacy of different herpes virus derived thymidine kinases (HSV1, varicella-zoster virus, equine herpes virus type-4 and Epstein–Barr virus) as suicide genes in association with the nucleoside analogs acyclovir, ganciclovir and bromovinyldeoxyur- idine. Using various murine and human cell lines expressing these viral tk, we show that HSV1- and EHV4tk are the more efficient suicide genes for the different nucleoside analogs tested. Moreover, EHV4tk expressing murine and human cells were three- to 12-fold more sensitive to GCV than HSV1tk expressing cells. This was correlated with the presence of five-fold higher amounts of the toxic triphosphated-GCV in EHV4- versus HSV1tk expressing cells. Altogether, these experiments underline the potential advantages of the EHV4tk as a suicide gene.

We have designed a self-assembling multimeric soluble CD4 molecule by inserting the C-terminal fragment of the alpha chain of human C4-binding protein (C4bpα) at the C-terminal end of human soluble CD4 genes. This CD4-C4bpa fusion protein (sMulti-CD4) and two other reference molecules, a fusion protein of human serum albumin (HSA) and the first two domains of CD4 (HSA-CD4) and monomeric soluble CD4 (sMono-CD4), were delivered in vivo by genetically modified 293 cells. These cells were implanted in mice as organoids and also encapsulated in HSA alginate-coated beads. sMulti-CD4 showed an apparent molecular weight of about 300–350 kDa, in accordance with a possible heptamer formula. sMulti-CD4 produced either in cell culture or in vivo in mice appeared to be a better in vitro inhibitor of HIV infection than sMono-CD4. Plasma levels of sMulti-CD4, HS A-CD4, and sMono-CD4 reached approximately 2,300, 2,700, and 170 ng/mL, respectively, 13 weeks after in-vivo organoid implantation, which had formed tumours at that time. This suggests that the plasma half-life of sMulti-CD4 is much longer than that of sMono-CD4. The 293 xenogeneic cells encapsulated in HSA alginatecoated beads remained alive and kept secreting sMono-CD4 or HSA-CD4 continuously at significant levels for 18 weeks in nude mice, without tumour formation. When implanted in immunocompetent Balb/c mice, they were rejected two to three weeks after implantation. In contrast, encapsulated BL4 hybridoma cells remained alive and kept secreting BL4 anti-CD4 mAb for at least four weeks in Balb/c mice. These results suggest the clinical potential of the C4bp-multimerizing system, which could improve both the biological activity and the poor in-vivo pharmacokinetic performance of a monomeric functional protein like soluble CD4. These data also show that a systemic delivery of therapeutic proteins, including immunoglobulins, can be obtained by the in-vivo implantation of engineered allogeneic cells encapsulated in HSA alginate-coated beads.

Many antiviral drugs must be metabolized to their active form by cellular enzymes. Their antiviral activity may therefore be limited by an inefficient metabolism, leading to low intracellular concentration of the active form or to the accumulation of toxic intermediate metabolites. Gene transfer might be used to overcome such limitations by transducing a gene able to increase intracellular drug metabolism. To prove such a concept, we chose the well-studied paradigm of zidovudine (AZT) metabolism and anti-HIV activity. AZT-triphosphate is the active form of AZT, acting through inhibition of HIV reverse transcription. In human cells, the rate-limiting step for AZT phosphorylation is catalyzed by the thymidylate kinase. We thus tested the capacity of herpes simplex virus type 1 thymidine kinase, which possesses a thymidylate kinase activity, to improve AZT metabolism and antiviral activity. Our results show enhanced AZT phosphorylation in HSV-1 TK-expressing lymphoid and monoblastoid cells, which correlated with significantly improved antiviral activity against different strains of HIV-1. The antiviral activity of Foscarnet, another reverse transcriptase inhibitor that does not require phosphorylation, remained unchanged. These results suggest that gene transfer might be envisioned for genetic pharmacomodulation of antiviral drugs.

Cellular expression of the herpes simplex virus type 1 thymidine kinase (HSV1-TK) gene promotes cell death in the presence of specific nucleoside analog substrates such as acyclovir (ACV). We have reported that lymphoid CD4+ cells harboring an HSV1-TK gene, under the transcriptional control of the HIV-1 long terminal repeat (HUT-TK), are completely protected from HIV-1 spread in the presence of 10 μM ACV. In this report we clarify the efficiency, generality, and mechanism of this protective effect. We show that the protection from HIV-1 spread in HUT-TK cells obtains from both an inhibition of HIV reverse transcription by ACV metabolites and an HIV-induced and ACV-dependent cell killing. We also demonstrate that monocytic cells harboring the HIV-1-inducible HSV1-TK gene are protected from HIV spread in the presence of ACV. These observations facilitate the design of therapeutic strategies to limit HIV replication based on HSV1-TK expression.

Using mAbs and genomic probe to the CD4 molecule, the HIV receptor, we demonstrated that HIV replication induces the disappearance of its functional receptor from the cell surface by two distinct mechanisms. First, after being expressed onto the cell surface, HIV envelope gp110 will complex CD4, efficiently masking the CD4 epitope used by the virus to bind its receptor. This phenomenon occurs on the surface of each infected cell and is not due to the release of soluble gp110; infection with recombinant HIV/vaccinia viruses expressing a mutated HIV env gene designed to prevent gp110 release from the cell surface induces a similar gp/CD4 complexes formation. Second, virus replication induces a dramatic and rapid loss of CD4 mRNA transcripts, preventing new CD4 molecules from being synthesized. These two mechanisms of receptor modulation could have been developed to avoid reinfection of cells replicating the virus as well as to produce more infectious particles. These results suggest that the classical virus interference documented for other retroviruses might not only be due to receptor/envelope interaction, but might also depend on receptor gene expression.

The Human Immunodeficiency Virus (HIV) displays a selective tropism for cells expressing the CD4 molecule which, by itself, represents at least part of the specific receptor for this virus. However, modification of the activation state of each individual cell seems critical not only for virus replication but also for its binding and subsequent penetration into its target. We demonstrate here that Cyclosporin-A (CSA), a drug which inhibits IL-2 dependent T-lymphocyte proliferation and differentiation and which is known for its immunosuppressive activity, can prevent subsequent virus binding to cells otherwise susceptible to HIV. Normal T-lymphocytes were preincubated in vitro with CSA at concentrations that were in the same range than those reached in the serum of treated patients. This resulted in the complete disappearance of HIV receptors (HIV-R), as assessed by the direct measure of specific binding of fluoresceinated HIV (HIV-FITC), and in the subsequent inhibition of HIV replication in cultured cells. Moreover CSA pretreatment of IL-2 independent transformed cells derived from the CEM line, before their infection, strongly inhibited HIV adsorption as well as further virus replication. These results provide a new experimental basis for the potential application of CSA in the treatment of HIV-related diseases.

We have investigated the respective role of quantitative T lymphocyte subset abnormalities, interleukin-2 (IL-2) production and responsiveness to IL-2, in the proliferative deficiency that is observed in acquired immune deficiency syndrome (AIDS) and Lymphadenopathy syndrome (LAS) patients or even in some apparently healthy male homosexuals. 83 subjects were evaluated: 35 symptom free male homosexuals (HC), 24 LAS and 24 AIDS patients. As expected, many HC and most patients presented with T lymphocyte subset imbalance. These quantitative defects were associated with decreased reactivity to PHA and reduced production of IL-2 by PHA stimulated lymphocytes. No correlation however could be found between these two functions and variations in the T lymphocyte subset distribution. On the other hand, PHA responsiveness appeared to closely depend on IL-2 activity. Addition of exogenous IL-2 to lymphocytes from patients with low proliferative responses, stimulated with suboptimal PHA concentration, enhanced proliferation in some but not all the cases. In most instances this increase never reached the levels observed with similarly treated cells from normal individuals. In these patients, the limited number of lymphocytes which express IL-2 receptors upon PHA stimulation may explain both low PHA reactivity and reduced IL-2 responsiveness. These data indicate some possible mechanisms of immunodeficiency in AIDS and LAS.

Lymphocytes (A) sensitized in vitro by cells from a HLA-identical sibling (B) for 8 days showed inhibiting effects when added to fresh mixed lymphocyte cultures (MLC) where A responders were stimulated by cells from other family members in a ratio of 1:1:1. In 23 of 31 such pairs tested in 15 families, proliferative activities in these 6-day second-step MLC were inhibited by 54 ± 18% in the presence of A′B sensitized cells as compared to control cultures with modulating A′ cells similarly preincubated but in the absence of B stimulators. In addition, A′B could also suppress MLC responses of B in 12 of the 17 pairs in which this was tested. Inhibition was not due to cytotoxic elimination of stimulators and it was radiation sensitive. Suppression appeared to be specific but it did not seem to be restricted by HLA-A, -B, or -DR determinants. Hence, these results indicate that suppressor cells generated after priming by HLA-identical cells can regulate allogeneic proliferative responses even when they are directed to HLA differences.

In order to assess the actual value of the in vitro tests of cellular immunity performed to provide diagnostic evidence for acquired immune deficiency syndrome (AIDS) or related syndromes, we have evaluated T-lymphocyte subsets and in vitro proliferative responses. The respective profiles of 44 symptom-free homosexual men, 30 patients with AIDS and 42 patients with lymphadenopathy were compared with each other and with profiles of blood bank volunteers, using stepwise discriminant analysis. At first investigation, control homosexuals, AIDS patients and lymphadenopathy patients displayed varying degrees of the same type of immunological abnormalities. The percentage of OKT4+ cells was the most discriminant variable between blood donors and control homosexuals, AIDS or lymphadenopathy patients. The latter differed from homosexuals by a higher percent of OKT8+ cells and from AIDS patients by a lesser reduction in T-lymphocyte counts. OKT4+ cell counts differentiated AIDS patients from control homosexuals. However, none of these major discriminant variables could classify correctly more than 70% of subjects in the homosexual and in the two patient groups. Thus, a single investigation of T-lymphocyte immune parameters does not provide substantial diagnostic and prognostic evidence.

In order to determine whether there exists a distinct immunological profile that discriminates between healthy homosexual men and those expressing persistent generalized hyperplastic lympadenopathy GHL and which of the observed abnormalities in GHL would be most indicative of patients who would eventually develop AIDS, we evaluated T lymphocyte subset and in vitro proliferative responses. The respective profiles of 44 symptom free homosexual men (HC), 42 patients with GHL and 30 cases of AIDS were compared to that of blood bank volunteers (BBV) and to each other, using stepwise discrimination analysis. HC, GHL and AIDS patients demonstrated upon their first investigation varying degrees of the same type of abnormal immunological characteristics. The percentage of OKT4+ cells was the most discriminant variable between BBV and HC, GHL or AIDS. GHL was distinguished from HC primarily by a higher percentage of OKT8+ cells and from AIDS by higher T lymphocyte counts, while the OKT4+ cell count discriminated between AIDS and HC. However, none of these major discriminant variables could classify correctly more than 71% within the HC and the two patient groups. Thus, there exists a continuity between GHL and AIDS in the range of observed immunological abnormalities without clearcut boundaries. This, together with the existence of abnormal background values in HC will not permit a single investigation of T lymphocyte immune parameters to provide substantial diagnostic and prognostic evidence.