Genotyping by PCR-ELISA of a complex polymorphic region that contains one to four copies of six highly homologous human VH3 genes

The Humhv3005 human VH gene is located in an intricate locus that encompasses for each haplotype a combination of one to four copies of six highly homologous VH3 genes. To assess the complexity of this region, we developed a polymerase chain reaction-enzyme-derived immunosorbent assay (PCR-ELISA) method capable of detecting each of the VH3 genes. The method consisted of amplification of selected germline VH3 genes with a biotinylated primer, covalent capture of the amplicons onto streptavidin-coated wells, and quantitative typing of the bound VH3 genes with diagnostic oligonucleotides. Pilot studies of two DNA samples with known presence or absence of hv3005 [according to a characteristic BamH1 restriction fragment-length polymorphism (RFLP)] yielded the expected results. Subsequent analysis of 100 additional DNA samples with the known EcoR1 RFLP of hv3005 showed a complete match between the absence of the 9.4-kb hybridizing band and lack of hv3005-like genes, as determined by PCR-ELISA. Importantly, the PCR-ELISA analyses of these 102 genomic DNA samples revealed two new haplotypes in the complex hv3005 region. Combined, these data demonstrate the usefulness and efficiency of this new technique to ascertain the presence or absence of six highly homologous genes in an unusually heterogeneous duplication-insertion-deletion region. In the future, a similar strategy may be used to dissect other similarly complex VH genetic loci.

Detection of p16 gene deletions in gliomas: a comparison of fluorescence in situ hybridization (FISH) versus quantitative PCR

The p16 protein plays a key role in cell cycle control by preventing CDK4 from inactivating the retinoblastoma protein (pRb). The corresponding tumor suppressor gene (p16/MTS1/CDKN2) has recently been implicated in malignant progression of astrocytomas and could potentially serve as an important marker for patient prognosis and for guiding specific therapeutic strategies. We have undertaken a study to evaluate 2 methods of detecting p16 deletion. Thirty diffuse gliomas were analyzed for p16 gene dosage. Dual color fluorescence in situ hybridization (FISH) was performed on cytologic preparations using paired centromeric (CEN) and locus-specific probes for CEN9/p16, CEN8/RB, and CEN12/CDK4. Quantitative PCR was performed using primers for p16, MTAP, and reference genes. Eleven cases were also studied using comparative genomic hybridization (CGH). Abnormalities of the p16-CDK4-RB pathway were identified in 21 (70%) cases by FISH and/or PCR. These included 15 (50%) with p16 deletion, 9 of which were detected by both techniques, 3 by FISH alone, and 3 by PCR alone (concordance rate = 81%). FISH analysis further revealed tetraploidy/aneuploidy in 14 (47%), RB deletion in 11 (37%) and CDK4 amplification in 1 (3.3%). There were 94% and 100% concordance rates between CGH and FISH or PCR, respectively. Quantitative PCR was noninformative in 4 cases. Although FISH and quantitative PCR are both reliable techniques, each has limitations. PCR is likely to miss p16 deletions when there is significant normal cell contamination or clonal heterogeneity, whereas the p16 YAC probe used for FISH analysis may miss small deletions. Replacement of the latter with a cosmid probe may improve the sensitivity of FISH in future experiments.

Genetic bias in immune responses to a cassette shared by different microorganisms in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease associated with HLA-DRbeta1 alleles which contain the QKRAA amino acid sequence in their third hypervariable region(s). The QKRAA sequence is also expressed by several human pathogens. We have shown previously that an Escherichia coli peptide encompassing QKRAA is a target of immune responses in RA patients. Here we address two questions: first, whether QKRAA may function as an "immunological cassette" with similar, RA-associated, immunogenic properties when expressed by other common human pathogens; and second, what is the influence of genetic background in the generation of these responses. We find that early RA patients have enhanced humoral and cellular immune responses to Epstein-Barr virus and Brucella ovis and Lactobacillus lactis antigens which contain the QKRAA sequence. These results suggest that the QKRAA sequence is an antigenic epitope on several different microbial proteins, and that RA patients recognize the immunological cassette on different backgrounds. ANOVA of immune responses to "shared epitope" antigens in monozygotic twin couples shows that, despite significantly elevated responses in affected individuals, a similarity between pairs is retained, thus suggesting a role played either by hereditary or shared environmental factors in the genesis or maintenance of these responses.

Immunostimulatory DNA sequences function as T helper-1-promoting adjuvants

An adjuvant role for certain short bacterial immunostimulatory DNA sequences (ISSs) has recently been proposed on the basis of their ability to stimulate T helper-1 (Th1) responses in gene-vaccinated animals. We report here that noncoding, ISS-enriched plasmid DNAs or ISS oligonucleotides (ISS-ODNs) potently stimulate immune responses to coadministered antigens. The ISS-DNAs suppress IgE synthesis, but promote IgG and interferon-gamma (IFN-gamma) production. They furthermore initiate the production of IFN-gamma, IFN-alpha, IFN-beta, and interleukins 12 and 18, all of which foster Th1 responses and enhance cell-mediated immunity. Consideration should be given to adding noncoding DNA adjuvants to inactivated or subunit viral vaccines that, by themselves, provide only partial protection from infection.

Inhibition of IgE antibody formation by plasmid DNA immunization is mediated by both CD4+ and CD8+ T cells

BACKGROUND

We previously showed that immunization of mice with plasmid DNA (pDNA) encoding the Escherichia coli beta-galactosidase gene (pCMV-LacZ) induces a Th1 response, whereas beta-galactosidase (beta-gal) in saline or alum induces a Th2 response. Furthermore, the Th1 response dominates over the Th2 response and downregulates preexisiting IgE antibody formation. Here, we determined by passive transfer of CD4+ or CD8+ lymphocytes and by immunizing beta2-microglobulin knockout (beta2-M KO) mice whether CD4+ and/or CD8+ cells from pDNA-immunized mice suppress IgE antibody production.

METHODS

BALB/c mice were injected with either CD4+ or CD8+ lymphocytes from naive beta-gal-in-alum or pCMV-LacZ-immunized mice, then immunized with beta-gal in alum, and the IgE antibody formation was determined. Second, C57BL/6 wild-type (WT) or beta2-M KO mice were immunized with beta-gal orpCMV-LacZ, and the IgE antibody production was assessed.

RESULTS

Passive transfer of both CD4+ and CD8+ lymphocytes from pDNA-immunized mice suppressed the IgE antibody response by 90% compared to transfer of CD4+ T cells from naive or beta-galin-alum immunized mice. beta2-M KO mice produced 3 times more IgE than the WT control mice both in the primary and secondary response.

CONCLUSION

Both CD4+ and CD8+ subsets of T cells from pDNA-immunized mice can suppress IgE antibody production by affecting the primary response and/or by propagating the Th1 memory response in a passive cell transfer system. Immunization with pDNA-encoding allergens may be an effective new form of immunotherapy for atopic diseases.

Molecular cloning of the human methylthioadenosine phosphorylase processed pseudogene and localization to 3q28

Human methylthioadenosine phosphorylase (MTAP) is a purine and methionine metabolic enzyme present ubiquitously in all normal tissues, but often deleted in many types of cancer. The gene for this enzyme maps to chromosome 9 at band p21 where the cyclin-dependent kinase inhibitor genes for p16 and p15 also reside. During our efforts to clone this gene we also isolated a phage clone containing a processed pseudogene of MTAP. The sequence is 92% homologous to the MTAP cDNA, is flanked at its 3' end by a repetitive element, but does not possess a poly(A) stretch. We localized this processed pseudogene to band 28 on the long arm of chromosome 3 by fluorescence in situ hybridization. All 22 malignant cell lines with deletions at 9p21 screened possessed the pseudogene.

Peripheral deletion of rheumatoid factor B cells after abortive activation by IgG

Rheumatoid factor (RF) B cells proliferate during secondary immune responses to immune complexed antigen and antigen specific T cells, but higher affinity RFs are not detected except in patients with rheumatoid arthritis and other autoimmune diseases. Consequently, there must exist highly efficient mechanisms for inactivation of these higher-affinity RF B cell clones under normal circumstances. Exposure of transgenic mice expressing a human IgM RF to soluble human IgG in the absence of T cell help causes antigen specific B cell deletion in 2-3 days. The deletion is independent of the Fas/Fas ligand (FasL) pathway of apoptosis and is preceded by a phase of partial activation involving increase in cell size and expression of B7 and ICAM-1, and transient release of low levels of immunoglobulin. Complete B cell activation involving the formation of germinal centers and sustained high level RF secretion only occurs if T cell help is provided simultaneously. RF B cells exposed to tolerogen remain competent to secrete RF in vitro if provided with an appropriate antigenic stimulus and T cell help. Consequently, death of these cells is not preceded by anergy. Abortive activation/deletion of B cells by antigen in the absence of T cell-derived survival signals may represent the major mechanism for maintaining peripheral tolerance in B cells expressing higher affinity RF. The lack of anergy, and the potential for reactivation before death, provide a means for maintaining RF production under pathologic circumstances, such as may occur in the inflamed rheumatoid synovium.

IgG rheumatoid factors isolated by the surface-displaying phage library technique

Our analysis of IgG rheumatoid factors (RFs) from three patients with rheumatoid arthritis (RA) revealed that most contained significant numbers of skewed mutations per V region, suggesting that these RFs arose from antigen-driven responses. To further study IgG RFs in RA, we used pComb3 vector to construct an IgG1,lambda combinatorial antibody library from a synovial fluid sample. After panning against human IgG, Fab fragments from 71/96 phage clones bound to Fc-coated wells. Sequence analysis of 20 randomly chosen Fc-binders showed that 17 (85%) clones had identical heavy (H) and light (L) chain V regions, represented by Humha311 and Humla211, respectively. Of the remaining three clones, two had the same Humla211 L chain, but each with a different H chain V region. All the putative germline V genes for these RFs also encode RF in RA patients. However, none of these RF V regions are similar to those of the two IgG RFs derived by the hybridoma technique from the same synovial fluid. The Humha311 H chain has two frameshifts: a one-base insertion upstream of the JH region and a four-base deletion near the end of the CH1 region, resulting in a mainly unconventional amino acid sequence in the CH1 region. In the future, it will be important to study the presence of IgG molecules with such unconventional CH1 amino acid sequences, and the effects of these amino acid sequences on the structures and immunological properties of the IgG molecules.

The human immunoglobulin V(H) gene repertoire is genetically controlled and unaltered by chronic autoimmune stimulation

The factors controlling immunoglobulin (Ig) gene repertoire formation are poorly understood. Studies on monozygotic twins have helped discern the contributions of genetic versus environmental factors on expressed traits. In the present experiments, we applied a novel anchored PCR-ELISA system to compare the heavy chain V gene (V(H)) subgroup repertoires of mu and gamma expressing B lymphocytes from ten pairs of adult monozygotic twins, including eight pairs who are concordant or discordant for rheumatoid arthritis. The results disclosed that the relative expression of each Ig V(H) gene subgroup is not precisely proportional to its relative genomic size. The monozygotic twins had more similar IgM V(H) gene repertoires than did unrelated subjects. Moreover, monozygotic twins who are discordant for RA also use highly similar IgM V(H) gene-subgroup repertoires. Finally, the V(H) gene repertoire remained stable over time. Collectively, these data reveal that genetic factors predominantly control V(H) gene repertoire formation.

Methylthioadenosine phosphorylase cDNA transfection alters sensitivity to depletion of purine and methionine in A549 lung cancer cells

Methylthioadenosine phosphorylase (MTAP), an enzyme involved in purine and methionine metabolism, is present in all normal tissues but is frequently deficient in a variety of cancers. It has been suggested that this metabolic difference between normal and cancer cells may be exploited to selectively treat MTAP-negative cancers by inhibiting de novo purine synthesis and by depleting L-methionine. However, these therapeutic strategies have only been tested in naturally occurring MTAP-positive and -negative cell lines, which might have additional genetic alterations that affect chemotherapeutic sensitivity. Therefore, it is of importance to examine the feasibility of enzyme-selective treatment using paired cell lines that have an identical genotype except for MTAP status. MTAP-negative A549 lung cancer cells were transfected with eukaryotic expression vectors encoding MTAP cDNA in sense and antisense orientations. The resultant stable transfectomas were treated with inhibitors of de novo purine synthesis such as methotrexate, 5,10-dideazatetrahydrofolate, and L-alanosine and by methionine depletion. The A549 cells transfected with an antisense construct (antisense transfectoma) expressed no MTAP protein and were more sensitive to both purine and methionine depletion than were cells expressing MTAP protein (sense transfectoma). Methylthioadenosine was able to completely rescue the sense transfectoma but not the antisense transfectoma from growth inhibition by depletion of purine and methionine. These results prove that MTAP deficiency contributes directly to the sensitivity of cancer cells to purine or methionine depletion. Inhibition of de novo purine synthesis, combined with methionine depletion in the presence of methylthioadenosine, is a highly selective treatment for MTAP-negative cancers.

Genetic control of T cell receptor BJ gene expression in peripheral lymphocytes of normal and rheumatoid arthritis monozygotic twins

The amino acids encoded at the junctions of T cell receptor (TCR) V and J genes directly interact with MHC bound peptides. However, the regulation of the human TCRBJ gene repertoire has been difficult to analyze, because of the potentially complex number of BJ gene rearrangements. To overcome this problem, we developed a PCR-ELISA method to study BJ gene expression, and compared peripheral T lymphocytes from 12 pairs of monozygotic twins, including 6 rheumatoid arthritis (RA) discordant pairs, and 5 normals. Analyses of the TCRBV5, 13 and 17 gene families, which have been reported to be increased in RA patients, showed: (a) the three TCRBV transcripts have common features of BJ gene usage; (b) TCR transcripts from each TCRBV family display a distinctive BJ gene profile, which is displayed better by CD4+ than CD8+ lymphocytes; (c) the BJ gene repertoires of monozygotic twins are more similar than those of unrelated individuals; and (d) the inflammation of RA does not induce specific changes in the genetically determined pattern of BJ expression. These results indicate that the frequency of expression particular TCRBV-TCRBJ recombinants in human lymphocytes is controlled genetically, and is maintained despite the presence of a chronic inflammatory disease.

Gene vaccination with naked plasmid DNA: mechanism of CTL priming

The injection of naked plasmid DNA directly into the muscle cells of mice has been shown to induce potent humoral and cellular immune responses. The generation of a cytotoxic T lymphocyte (CTL) response after plasmid DNA injection may involve the presentation of the expressed antigen in the context of the injected myocytes' endogenous major histocompatibility (MHC)-encoded class I molecules or may use the MHC molecules of bone marrow-derived antigen presenting cells (APC) which are capable of providing co-stimulation as well. To resolve which cell type provides the specific restricting element for this method of vaccination we generated parent-->F1 bone marrow chimeras in which H-2bxd recipient mice received bone marrow that expressed only H-2b or H-2d MHC molecules. These mice were injected intramuscularly with naked plasmid DNA that encoded the nucleoprotein from the A/PR/8/34 influenza strain, which as a single antigen has epitopes for both H-2Db and H-2Kd. The resulting CTL responses were restricted to the MHC haplotype of the bone marrow alone and not to the second haplotype expressed by the recipient's myocytes. The role of somatic tissues that express protein from injected plasmids may be to serve as a reservoir for that antigen which is then transferred to the APC. Consequently, our data show that the mechanism of priming in this novel method for vaccination uses the MHC from bone marrow-derived APC, which are efficient at providing all of the necessary signals for priming the T cell.

Identification of human tumour suppressor genes by monochromosome transfer: rapid growth-arrest response mapped to 9p21 is mediated solely by the cyclin-D-dependent kinase inhibitor gene, CDKN2A (p16INK4A)

Microcell transfer of intact normal human chromosomes into immortal mouse and hamster fibroblast cell lines has revealed growth suppressive activity associated with a small sub-set of the human complement. Here, we describe the results of a detailed study aimed at identifying the gene or genes responsible for the rapid growth-arrest response obtained with human chromosome-9. Initially, STS-PCR deletion mapping of segregants arising in monochromosome transfer experiments was used successfully to localize the active sub-chromosomal region to 9p21. Subsequent fine-structure deletion mapping of previously uniformative hybrid segregants, employing additional markers between D9S162 and D9S171, provided strong evidence that the cyclin-dependent kinase (cdk) inhibitor gene CDKN2A (p16INK4A) was solely responsible for the chromosome-9 effect; 9p21 microdeletions in a significant proportion of segregant clones were restricted to a single CDKN2A exon. Transfection experiments with CDKN2A and CDKN2B cDNA expression vectors, using mouse A9 cells and three human malignant melanoma cell lines as recipients, provided further evidence in support of this hypothesis. Collectively, our results indicate that expression of human CDKN2A (controlled either by its natural regulatory elements, or by a cytomegalovirus promoter) is incompatible with in vitro proliferation in immortalized rodent cells and in human melanoma cell lines. The rapidity of the growth inhibitory effects of CDKN2A was inconsistent with a mode of action involving induction of replicative cell senescence via telomerase repression, but was consistent with a mechanism based on cell cycle arrest through cdk inhibition. The study described here has generated a panel of microdeleted monochromosome-9 donor hybrids which may prove valuable in functional investigations aimed at identifying other important tumour suppressor genes located on human chromosome-9.

Immunostimulatory DNA sequences necessary for effective intradermal gene immunization

Vaccination with naked DNA elicits cellular and humoral immune responses that have a T helper cell type 1 bias. However, plasmid vectors expressing large amounts of gene product do not necessarily induce immune responses to the encoded antigens. Instead, the immunogenicity of plasmid DNA (pDNA) requires short immunostimulatory DNA sequences (ISS) that contain a CpG dinucleotide in a particular base context. Human monocytes transfected with pDNA or double-stranded oligonucleotides containing the ISS, but not those transfected with ISS-deficient pDNA or oligonucleotides, transcribed large amounts of interferon-alpha, interferon-beta, and interleukin-12. Although ISS are necessary for gene vaccination, they down-regulate gene expression and thus may interfere with gene replacement therapy by inducing proinflammatory cytokines.

Influence of the rheumatoid arthritis-associated shared epitope on T-cell receptor repertoire formation

Rheumatoid arthritis is associated with several human leukocyte antigen DRB1 types that express a common five-amino acid sequence called the shared epitope. Here we show that the human leukocyte antigen DRB1 shared epitope expands naive T lymphocytes that express the same T-cell-receptor variable region-joining region combinations that are prevalent in the synovia of rheumatoid arthritis patients. Thus, the shared epitope could affect rheumatoid arthritis disease susceptibility by selecting in the premorbid state specific T-cell subsets that contribute to synovial inflammation.

Purification and characterization of recombinant human 5'-methylthioadenosine phosphorylase: definite identification of coding cDNA

5'-Methylthioadenosine phosphorylase gene maps on the 9p21 chromosome, strictly linked to the important tumor suppressor gene p16INK4A. Chromosomal deletions encompassing both the phosphorylase and p16INK4A genes cause the complete absence of the enzymatic activity in a large number of tumors, thus resulting in well-defined metabolic differences between malignant and normal cells. Recently, the cloning of the phosphorylase gene has been reported on the basis of indirect evidence. In order to demonstrate definitely the identification of 5'-methylthioadenosine phosphorylase gene, we have cloned the putative enzyme coding sequence in a prokaryotic expression vector and expressed the protein in bacteria. The recombinant phosphorylase has been purified to homogeneity and its physicochemical, immunological and kinetic features have been characterized. The results obtained allowed the conclusive demonstration of 5'-methylthioadenosine phosphorylase gene cloning and the use of recombinant protein for further characterization.

Genomic cloning of methylthioadenosine phosphorylase: a purine metabolic enzyme deficient in multiple different cancers

5'-Deoxy-5'-methylthioadenosine phosphorylase (methylthioadeno-sine: ortho-phosphate methylthioribosyltransferase, EC 24.2.28; MTAP) plays a role in purine and polyamine metabolism and in the regulation of transmethylation reactions. MTAP is abundant in normal cells but is deficient in many cancers. Recently, the genes for the cyclin-dependent kinase inhibitors p16 and p15 have been localized to the short arm of human chromosome 9 at band p21, where MTAP and interferon alpha genes (IFNA) also map. Homozygous deletions of p16 and p15 are frequent malignant cell lines. However, the order of the MTAP, p16, p15, and IFNA genes on chromosome 9p is uncertain, and the molecular basis for MTAP deficiency in cancer is unknown. We have cloned the MTAP gene, and have constructed a topologic map of the 9p21 region using yeast artificial chromosome clones, pulse-field gel electrophoresis, and sequence-tagged-site PCR. The MTAP gene consists of eight exons and seven introns. Of 23 malignant cell lines deficient in MTAP protein, all but one had complete or partial deletions. Partial or total deletions of the MTAP gene were found in primary T-cell acute lymphoblastic leukemias (T-ALL). A deletion breakpoint of partial deletions found in cell lines and primary T-ALL was in intron 4. Starting from the centromeric end, the gene order on chromosome 9p2l is p15, p16, MTAP, IFNA, and interferon beta gene (IFNB). These results indicate that MTAP deficiency in cancer is primarily due to codeletion of the MTAP and p16 genes.

Preferential induction of a Th1 immune response and inhibition of specific IgE antibody formation by plasmid DNA immunization

We compared the antigen-specific antibody isotypes and lymphokine secretion by CD4+ T cells in BALB/c mice immunized intradermally with either Escherichia coli beta-galactosidase (beta-gal) or plasmid DNA (pDNA) encoding beta-gal in a cytomegalovirus-based expression vector (pCMV-LacZ). pCMV-LacZ induced mainly IgG2a, whereas beta-gal in saline or alum induced IgG1 and IgE beta-gal-specific antibodies. In addition, splenic CD4+ T helper (Th) cells isolated from pDNA-immunized mice secreted interferon-gamma but not interleukin (IL)-4 and IL-5, whereas Th cells from beta-gal-injected mice secreted IL-4 and IL-5 but not interferon-gamma after in vitro stimulation with antigen. Together these data demonstrate that pDNA immunization induced a T helper type 1 (Th1) response, whereas protein immunization induced a T helper type 2 (Th2) response to the same antigen. Interestingly, priming of mice with pCMV-LacZ prevented IgE antibody formation to a subsequent i.p. beta-gal in alum injection. This effect was antigen-specific, because priming with pCMV-LacZ did not inhibit IgE anti-ovalbumin antibody formation. Most importantly, intradermal immunization with pCMV-LacZ (but not pCMV-OVA) of beta-gal in alum-primed mice caused a 66-75% reduction of the IgE anti-beta-gal titer in 6 weeks. Also, pCMV-LacZ induced specific IgG2a antibody titers and interferon-gamma secretion by Th cells in the beta-gal in alum-primed mice. The data demonstrate that gene immunization induces a Th1 response that dominates over an ongoing protein-induced Th2 response in an antigen-specific manner. This suggests that immunization with pDNA encoding for allergens may provide a novel type of immunotherapy for allergic diseases.

Gene cloning and characterization of Pseudomonas putida L-methionine-alpha-deamino-gamma-mercaptomethane-lyase

Methionine dependency has been reported in cancer cell lines and primary tumors. Thus, L-methionine deprivation might have potential value for the treatment of human cancers with a methionine requirement. L-Methionine-alpha-deamino-gamma-mercaptomethane-lyase has been reported to decrease plasma methionine levels and to inhibit tumor growth in experimental animals but has not been studied extensively because sufficient homogeneous enzyme was not available. In this study, we cloned the L-methioninase gene from Pseudomonas putida and isolated pure and abundant recombinant enzyme. Both L-methionine and L-cysteine in culture medium were completely degraded by 1 unit/ml purified enzyme. Two hundred and fifty units/kg L-methioninase administered i.v. to mice yielded 0.7 unit/ml of plasma concentration and lowered total plasma sulfur-containing amino acids by more than 75%. Although sensitivity to enzymatic methionine depletion differed among cell lines, leukemia cell lines were generally more sensitive than solid tumor cell lines. The availability of pure recombinant L-methioninase will allow in vivo studies on the antitumor activity and the potential toxicity of enzymatic methionine depletion.

Effect of immune globulin on the prevention of experimental hepatitis C virus infection

The efficacy of postexposure prophylaxis for the prevention of hepatitis C virus (HCV) infection was studied in experimentally infected chimpanzees. Three chimpanzees were inoculated with HCV: Two were treated 1 h later with anti-HCV--negative intravenous immune globulin (IGIV) or hepatitis C immune globulin (HCIG), and a third animal was not treated. HCV infection was detected in all 3 animals within a few days of inoculation. Once passively transferred anti-HCV declined in the HCIG-treated animal, there was an increase of HCV antigen (Ag)--positive hepatocytes followed by reappearance of anti-HCV; HCV Ag disappeared concordant with the development of acute hepatitis. Acute hepatitis C developed in both the IGIV-treated and untreated chimpanzees, with peak liver enzyme activity on day 59, but was delayed in the HCIG-treated animal until day 146. Postexposure HCIG treatment markedly prolonged the incubation period of acute hepatitis C but did not prevent or delay HCV infection. IGIV had no effect on the course of HCV infection.

Substituted xanthines, pteridinediones, and related compounds as potential antiinflammatory agents. Synthesis and biological evaluation of inhibitors of tumor necrosis factor alpha

A series of analogues of pentoxifylline metabolites were prepared in the purine, pteridine, [1,2,5]-thiadiazolo[3,4-d]pyrimidine, and quinazoline ring systems and evaluated for their ability to inhibit the production of tumor necrosis factor-alpha (TNF alpha) in human peripheral blood monocytes stimulated with bacterial lipopolysaccharide (LPS). The more active compounds were also tested for inhibition of cyclic AMP phosphodiesterase type IV (PDE IV) from human neutrophils in order to help determine their mechanism of action. Selected compounds which showed good activity in the in vitro TNF alpha assay were evaluated in an in vivo LPS-induced leukopenia model in mice. The most potent compounds in the TNF alpha assay, 6, 31, and 58, inhibited TNF alpha production at an IC50 of approximately 5 microM for each. Compound 58 was a very poor inhibitor of PDE IV but was the most active at preventing the leukopenia induced by TNF alpha in mice, providing more than 60% protection at 50 mg/kg. Thus, compounds such as 58, which are good inhibitors of TNF alpha production but are devoid of PDE IV inhibitory properties, may have potential as new antiinflammatory agents.

Oral 2-chlorodeoxyadenosine in psoriatic arthritis. A preliminary report

OBJECTIVE

To determine if weekly oral 2-chlorodeoxyadenosine (2-CdA) can induce selective lymphocytopenia, and reduce inflammation, in patients with refractory psoriatic arthritis.

METHODS

Seven patients with psoriatic arthritis were treated with oral 2-CdA at weekly dosages of 0.3 mg/kg to 0.45 mg/kg for 12 weeks, followed by monthly maintenance therapy. The patients were evaluated after 6 months.

RESULTS

The drug treatment produced selective lymphocytopenia, and reduced lymphocyte infiltration into involved skin. One patient did not complete 12 weeks of therapy because of perceived lack of efficacy. Four of the 6 remaining patients had improved joint disease, and 5 of 6 had improved psoriasis.

CONCLUSION

Weekly oral 2-CdA appears to be a well-tolerated regimen for the inducement of peripheral lymphocytopenia in patients with psoriatic arthritis. Larger-scale, controlled trials may be warranted.

Cancer progression and p53

In a complex organism, somatic cells are under intermittent selection pressure for the emergence of mutants that can survive environmental insults and that can grow autonomously despite adverse conditions. Repeated rounds of mutation, selection, and proliferation may lead to cancer. The organism prevents malignant transformation by assuring accurate DNA repair before cell division, by forcing the death of cells with excessive DNA damage, and by placing limits on the replicative lifespans of most somatic cells. The p53 gene is a "guardian of the genome"--it regulates multiple components of the DNA damage control response and promotes cellular senescence. Disabling mutations and deletions of p53 occur in 50% of human tumours. p53-deficient cancers are often unstable, aggressive, and resistant to therapy.