Prevalence of hepatitis B, hepatitis C, and GB virus C/hepatitis G virus infections in liver disease patients and inhabitants in Ho Chi Minh, Vietnam

The prevalence of hepatitis B virus (HBV), hepatitis C virus (HCV), and GB virus C or hepatitis G virus (GBV-C/HGV) infections was determined in 289 patients with liver disease in Ho Chi Minh City and 890 healthy inhabitants of its rural area, Dalat City, Vietnam, respectively. Serum HCV RNA and GBV-C/HGV RNA were detected by reverse transcription-polymerase chain reaction (RT-PCR). HBsAg, HCV antibodies, and GBV-C/HGV RNA were detected in 139 (47%), 69 (23%), and ten (3%) subjects, respectively, often accompanied by elevated serum levels of alanine aminotransferase. HBsAg and HCV antibodies or HCV antibodies and GBV-C/HGV RNA were detectable simultaneously in 8% and 2% of the patients, respectively. In the inhabitants, HBsAg, HCV antibodies, and GBV-C/HGV RNA were found in 51 (5.7%), nine (1.0%), and 11 (1.2%) subjects, respectively. Thus, the prevalence of HBsAg, HCV antibodies, and GBV-C/HGV RNA was significantly higher in liver disease patients than those in the general population. In the samples from 69 patients and nine inhabitants who were seropositive for HCV antibodies, HCV RNA was detectable in 42 (61%) and 4 (44%), respectively. In patients with liver disease, ten belonged to HCV genotype 1a, ten to HCV 1b, three to HCV 2a, four to HCV 2b, and two to HCV 3a by PCR with genotype-specific primers. Nine patients had mixed genotypes, and the remaining four were not classified. Of the GBV-C/HGV RNA-positive individuals, two patients and two inhabitants were positive for HBsAg, while none of the residents had HCV antibodies, although six HCV antibodies (60%) and four HCV RNA (40%) were found in patients. When a phylogenetic tree of GBV-C/HGV was constructed based on the nucleotide sequences, the 21 isolates were classified into at least two genotypes; four isolates belonged to G2, and 17 to G3. The results indicate that in Ho Chi Minh HCV infection prevails with broad distribution of genotypes together with HBV infection among patients with liver disease. This study suggests that GBV-C/HGV infection occurs independently in the two different districts in association with HCV infection.

Cellular basis of skin allograft rejection in mice: specific lysis of allogeneic skin components by non-T cells

BACKGROUND

It has been generally assumed that CD8+ T cells mediate direct lysis of allografts and that their growth, differentiation, and activation are dependent upon cytokine production by CD4+ T cells. However, both the generation of CD4- or CD8-deficient mice and adoptive transfer experiments with CD4+ T cells from CD8-deficient mice demonstrate that noncytotoxic CD4+ T cells alone are sufficient to induce skin or organ allograft rejection. Furthermore, we have reported that the major effector cells responsible for allografted-tumor (e.g., Meth A) rejection are allograft-induced macrophages (AIM) with MHC haplotype specificity.

METHODS

We characterized the macrophages migrating into the rejection site of allografted skin by immunohistochemical and in situ hybridization analyses using an antibody (K16.5) specific for AIM and a cDNA (pK30) encoding the antigen. To determine the in situ effector cells responsible for the rejection, we prepared both effector cells and target cells from the graft-graft bed border.

RESULTS

The macrophages seemed to be morphologically (monocytic), phenotypically (K16.5+/pK30+), and functionally (cytotoxic against Meth A cells) AIM. The AIM population in bulk infiltrates taken from the rejection site was cytotoxic against allografted, but not self, skin components (e.g., fibroblasts, myocytes, endothelial cells, and epithelial cells). In contrast, other types of infiltrating cells including lymphocytes and granulocytes were virtually inactive toward these targets, and NK-1.1+ cells hardly infiltrated into the rejection site.

CONCLUSIONS

These data suggest that the major effector cells mediating allografted skin rejection are AIM and not T cells.

Effects of intranasal administration of recombinant murine interferon-gamma on murine acute myocarditis caused by encephalomyocarditis virus

BACKGROUND

Viral myocarditis has been strongly implicated in the pathogenesis of dilated cardiomyopathy as well as acute myocarditis. Among the antiviral therapies, interferons (IFNs) have been widely studied and become very important in clinical practice.

METHODS AND RESULTS

To investigate the possibilities of IFN therapy in viral myocarditis, we analyzed the effects of recombinant murine interferon (mIFN)-gamma and natural mIFN-alpha/beta by the intranasal and intramuscular routes on the development of acute murine myocarditis caused by encephalomyocarditis virus. Both mIFN-gamma and mIFN-alpha/beta treatment by either route significantly increased the survival rate; none of the mIFN-gamma-treated mice died. The effect of mIFN-gamma was significantly greater than that of mIFN-alpha/beta. Furthermore, intranasal administration of mIFN-gamma significantly suppressed virus replication and inflammation in the heart.

CONCLUSIONS

Our data demonstrate that IFN therapy, especially intranasal administration of IFN-gamma, dramatically improved the prognosis of acute murine viral myocarditis by suppressing virus replication and raises the possibility of antiviral therapy with IFN-gamma in patients with acute myocarditis.

Telencephalic ascending gustatory system in a cichlid fish, Oreochromis (Tilapia) niloticus

Central fiber connections of the gustatory system were examined in a percomorph fish Oreochromis (Tilapia) niloticus by means of the horseradish peroxidase (HRP), biocytin, and carbocyanine dye tracing methods. The primary gustatory areas in tilapia are the facial, glossopharyngeal, and vagal lobes of the medulla. The secondary gustatory nucleus (SGN) is a dumb-bell-shaped structure located in the isthmic region. In the SGN, there are two or three layers of neurons lining the ventromedial periphery of the nucleus and a molecular layer constituting of the major part of the nucleus. The SGN receives bilateral projections from the facial lobes and ipsilateral projections from the glossopharyngeal and vagal lobes. Ascending fibers originating from the SGN form the ipsilateral tertiary gustatory tract. A major part of the tract courses rostrally and terminates ipsilaterally in several diencephalic nuclei: the preglomerular tertiary gustatory nucleus (pTGN), the posterior thalamic nucleus, the nucleus diffusus lobi inferioris, the nucleus centralis of inferior lobe, and the nucleus recessus lateralis. The remaining small fiber bundle enters the medial and lateral forebrain bundles and terminates directly in two telencephalic regions; the area ventralis pars intermedia (Vi) and the area dorsalis pars posterior (Dp). Ascending fibers from the pTGN pass through the lateral forebrain bundle and terminate ipsilaterally in the dorsal region of area dorsalis pars medialis (dDm) of the telencephalon. Following biocytin injections into the dDm, small, round cells were labeled in the pTGN. After biocytin injections into the Vi and Dp of the telencephalon, retrogradely labeled cells were found in the ipsilateral SGN. The results show that the ascending fiber connections of the central gustatory system in the percomorph teleost tilapia are essentially similar to those of mammals. That is, the pathway from the primary gustatory areas (facial, glossopharyngeal, and vagal lobes) through the SGN and pTGN to the dDm in tilapia corresponds with the mammalian gustatory pathway from the solitary nucleus through the pontine taste areas (nucleus parabrachialis) and the thalamic relay nucleus (ventral posteromedial nucleus) to gustatory neocortices. In addition, the pathway from the primary gustatory areas through the SGN to the Vi and Dp in tilapia corresponds with the pathway from the solitary nucleus through the pontine taste areas to the amygdala in mammals.

The value of serum alpha-N-acetylgalactosaminidase measurement for the assessment of tumour response to radio- and photodynamic therapy

Serum activity of alpha-N-acetylgalactosaminidase (NaGalase), the extracellular matrix-degrading enzyme that appears to be produced exclusively by cancer cells, was measured in mice bearing SCCVII tumours (squamous cell carcinoma). The NaGalase levels in these mice increased with time of tumour growth and were directly proportional to tumour burden. After exposure of SCCVII tumours to a single X-ray dose of 20 Gy, the serum NaGalase levels gradually decreased during the first 10 days after treatment (to approximately one-third of the initial value) and then began to increase. The decrease in serum NaGalase activity was more rapid after the treatment of SCCVII and EMT6 tumours by photodynamic therapy (PDT) and was dependent on the PDT dose. The treatments (based on photosensitizers Photofrin or mTHPC) that were fully curative resulted in the reduction of NaGalase activity to background levels within 2 or 3 days after PDT. A slower decrease in NaGalase activity was found after PDT treatments that attain an initial tumour ablation but are not fully curative. The regrowth of PDT-treated SCCVII tumours was preceded by an increase in serum NaGalase levels, which was detected as early as 8 days before the visible tumour reappearance. These findings ascertain the validity of serum NaGalase measurement for the assessment of tumour response to different treatments and support the concept that the NaGalase measurement could serve as a diagnostic and prognostic index that might allow oncologists to design the dosage or nature of treatment.

[Drug delivery system (DDS) for the use of antisense oligodeoxynucleotide phosphorothioate in controlling gene expression]

Synthetic antisense oligodeoxynucleotide phosphorothioates (ODNs) are widely used as therapeutic tools in various in vitro and in vivo systems. Here, we applied ODNs to inhibit viral gene expression. Human T-cell leukemia virus type I (HTLV-I) is a retrovirus, and is closely linked to adult T-cell leukemia (ATL), HTLV-I-associated myelopathy/tropical spastic paraparesis(HAM/TSP), and other HTLV-I-associated diseases. With an attempt to control viral replication in vitro, ODNs to HTLV-I tax gene were synthesized and applied. In addition, 1,2-dioleoyloxy-3-(trimethylammonio) propane, DOTAP as a drug delivery system, was exploited to increase the cellular uptake of ODNs. Combination of ODNs and DOTAP was more effective to suppress viral antigen expression than ODNs only. Therefore this combination method may be useful in clinical trials for HTLV-I-associated diseases.

Factors that influence the eligibility of cases for inclusion in clinical trials. The Lung Cancer Chemotherapy Study Group of the Japan Clinical Oncology Group

BACKGROUND

It is important to minimize the incidence of ineligible cases to improve the quality of clinical trials. To determine factors which may influence the incidence of ineligible cases, the incidence of and reasons for ineligibility in clinical trials were retrospectively analyzed.

METHODS

We retrospectively examined the incidence of and reasons for ineligibility for inclusion in eight clinical trials conducted by the Lung Cancer Chemotherapy Study Group of the Japan Clinical Oncology Group and four trials financed by trust funds from a pharmaceutical company.

RESULTS

In these 12 clinical studies, the incidence of ineligibility was 4.2% (32/762) (range 0-10.6%). Specific factors that might influence the incidence of ineligible cases were then analyzed. There was a significant difference in the incidence of ineligibility between the methods of registration (P < 0.05). The incidences using a central registration and without using a central registration system were 2.8% (9/322) and 5.2% (23/440) respectively. We also analyzed ineligible cases in clinical studies published in the Journal of Clinical Oncology. In clinical studies published in the Journal of Clinical Oncology recently and 10 years ago, the incidences of ineligible cases were 5.0% (942/18 878) and 4.1% (206/4995) respectively. In clinical studies on lung cancer published in the Journal of Clinical Oncology from 1984 to 1995, the incidence of ineligible cases was 4.7% (900/19,116). There was no significant difference in the incidence of ineligible cases between our 12 studies and the Journal of Clinical Oncology clinical studies by the chi 2 test (P > 0.05).

CONCLUSIONS

We conclude that the incidence of ineligible cases in our studies is similar to that in clinical trials published in the Journal of Clinical Oncology. Central registration systems are useful for checking for ineligibility, and to increase the quality of clinical trials.

Human T-cell leukemia virus type 1 Tax protein induces the expression of lymphocyte chemoattractant SDF-1/PBSF

We investigated the mechanism of lymphocyte infiltration into tissues infected with human T-cell leukemia virus type 1 (HTLV-1). The cytokine SDF-1/PBSF is a highly efficient chemoattractant for lymphocytes. Reverse transcription-PCR analysis showed that among various human T-cell lines, those infected with HTLV-1 selectively expressed the SDF-1 gene. Expression of the viral protein Tax in a human T-cell line induced the expression of the SDF-1 gene, indicating that the constitutive expression of SDF-1 in virus-infected cell lines is at least in part mediated by Tax. HTLV-1-infected T-cell lines also expressed CXCR-4, a receptor for SDF-1. Moreover, chemotaxis assay showed that a HTLV-1-infected cell line migrated toward synthetic SDF-1. Thus, HTLV-1-infected cells are themselves responders for SDF-1. Our results suggest that SDF-1 induced by Tax may alter the distribution of HTLV-1-infected cells in vivo; hence it may contribute to their infiltration into affected tissues in HTLV-1-associated inflammatory diseases.

Expression of FAP-1 (Fas-associated phosphatase) and resistance to Fas-mediated apoptosis in T cell lines derived from human T cell leukemia virus type 1-associated myelopathy/tropical spastic paraparesis patients

Human T cell leukemia virus type 1 (HTLV-I) is the etiologic agent of HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) with an autoimmune condition. We examined the sensitivity of HTLV-I-infected T cell lines to Fas-mediated apoptosis, which plays a critical role in the elimination of self-reactive T cells. Among 13 human T-cell lines, all 4 HAM-derived T cell lines and 4 of 6 non-HAM/HTLV-I T cell lines were resistant to apoptosis induced by anti-Fas antibody, whereas only 1 of 3 uninfected cell lines was resistant to apoptosis. The cell lines resistant to apoptosis expressed the viral tax gene and/or the cellular FAP-1 (Fas-associated phosphatase) gene, both of which inhibit Fas-mediated apoptosis in T cell lines. Although Tax is a transcriptional activator of a number of cellular genes, the expression of Tax in a T cell line did not induce the expression of FAP-1, suggesting that these two antiapoptotic proteins independently function in HTLV-I-infected cells. Seven of 10 HTLV-I-infected cell lines, compared with only 1 of 3 virus-negative cell lines, expressed FAP-1. All four HAM cell lines expressed the FAP-1 gene, and its level in these cells was higher than in other T cell lines. Our results suggest that virus-infected T cells escape Fas-mediated immune surveillance by the function of Tax and FAP-1, and this escape may be involved in the autoimmune condition observed in HAM/TSP patients.

Inhibition of human T-cell leukemia virus type 1 replication by antisense env oligodeoxynucleotide

Human T-cell leukemia virus type 1 (HTLV-1) infection is associated with adult T-cell leukemia and HTLV-associated myelopathy/tropical spastic paraparesis. Inhibition of HTLV-1 transmission is important to prevent the above HTLV-1-associated diseases. We used the antisense oligodeoxynucleotides (oligos) complementary to the first splice junction, rex responsive site, gag, env, tax, rex, and p21 and evaluated the effects on the syncytium formation between HTLV-1 producing human T-cell line, C9/PL cells, and HTLV-1-uninfected human glioma cell line, U251-MG cells. The syncytium formation was significantly inhibited the virion production assayed by antisense oligos to env, tax, gag, p21, and rex, with antisense oligo to env being the most inhibitory. Antisense oligos to env and tax also inhibited reverse transcriptase activity. Antisense oligo to env may have a potential as a preventive measure of HTLV-1 replication and transmission in vivo.

Gonadotropin-releasing hormone (GnRH) innervation of the pituitary in a cichlid fish, Oreochromis niloticus: a brain lesion study

In most vertebrates, multiple gonadotropin-releasing hormone (GnRH) neuronal groups have been reported. In tilapia three GnRH neuronal groups (terminal nerve, preoptic, midbrain) have been reported. Which of the three GnRH cell groups regulate the pituitary is not well known. We performed brain lesions of each neuronal group and studied immunocytochemically the changes of GnRH fiber distribution in the pituitary. Lesions of the preoptic cell group resulted in almost complete absence of GnRH fibers in the neurohypophysis of the proximal pars distalis. After lesions of the terminal nerve GnRH cell group, no changes were observed in the distribution of GnRH fibers in the pituitary. Lesions of the midbrain cell group were unsuccessful because of high mortality. The present study indicates that the preoptic GnRH cell group is the main contributor of the pituitary innervation.

Effective lowly cytotoxic analogs of an HIV-cell fusion inhibitor, T22 ([Tyr5,12, Lys7]-polyphemusin II)

A tachyplesin peptide analog, T22 ([Tyr5,12, Lys7]-polyphemusin II), and its shortened congener, TW70 (des-[Cys8,13, Tyr9,12]-[D-Lys10, Pro11]-T22) have strong anti-human immunodeficiency virus (HIV) activity, comparable to that of 3'-azido-2', 3'-dideoxythymidine (AZT). T22 and TW70 are extremely basic peptides, containing 5 Arg residues and 3 Lys residues. The number of positive charges might be related in part to high collateral cytotoxicities of T22 and TW70. Here we have synthesized several analogs, in which the number of positive charges has been reduced through amino acid substitutions using Glu or L-citrulline. As a result, several effective compounds have been found which possess higher selectivity indexes (SIs, 50% cytotoxic concentration/50% effective concentration) than those of T22 and TW70. Higher SIs were attributed mainly to a decrease in cytotoxicity.

Gonadotropin-releasing hormone neurons in the gourami midbrain: a double labeling study by immunocytochemistry and tracer injection

There are three groups of gonadotropin-releasing hormone (GnRH) neurons in the teleost brain. Midbrain GnRH neurons in the dwarf gourami send axons to various areas of the central nervous system. However, it is not clear whether midbrain GnRH neurons form a cell cluster separate from the nucleus of the medial longitudinal fasciculus (nMLF), which has been reported to project to the spinal cord. Thus, we performed a double labeling study. GnRH neurons were immunostained but were very faintly labeled with biocytin injected into the spinal cord. In contrast, nMLF neurons were strongly labeled with biocytin but were GnRH-immunonegative. GnRH neurons are distributed at almost the same rostrocaudal levels as nMLF neurons, but they constitute a separate cell group dorsocaudal to nMLF neurons.

Caffeine-assisted chemotherapy and minimized tumor excision for nonmetastatic osteosarcoma

Osteosarcoma is usually treated with intensive preoperative and postoperative chemotherapy and wide tumor resection, resulting in a 60% to 70% 5-year survival rate. Caffeine has a DNA-repair inhibiting effect. We therefore investigated the impact of caffeine given in conjunction with chemotherapy and limb-sparing surgery on survival and local tumor control in patients with nonmetastatic, high-grade osteosarcoma. Twenty-two patients were given 3 to 5 preoperative courses of intra-arterial cisplatin (120 mg/m2, 1 to 2 hours) and caffeine (1.5 g/m2/day x 3 days) with or without doxorubicin (30 mg/m2/day x 2 days). Following this treatment, limb-sparing surgery was performed by means of intentional marginal excision aiming at preservation of important structures such as major neurovascular bundles, tendons, ligaments and the epiphysis. Three courses of cisplatin and doxorubicin combined with caffeine, and high-dose methotrexate with vincristine and citrovorum factor rescue were given intravenously as postoperative chemotherapy for 21 patients and three courses of high-dose methotrexate and combination of ifosfamide, etoposide and methotrexate for 1 patient. Following the preoperative chemotherapy, there were no viable tumor cells in 19 patients, only scattered foci of viable cells in 2 patients, and some areas of viable tumor cells in 1. The 21 patients with a good chemotherapeutic response on radiographs underwent minimized marginal excision. Functional evaluation of the affected limbs was excellent for 17 patients, good for 3, fair for 1, and poor for 1. No local tumor recurrence was seen in this series. Eighteen patients remain disease-free with a mean follow-up of 61 months. Two patients died of metastatic disease, 1 died of chemotherapy-related complications, and 1 died of unknown causes. The overall 5-year cumulative survival rate was 90%, and the 5-year event-free survival rate was 75%. Chemotherapeutic caffeine enhanced tumor necrosis and improved the success rate of limb-sparing surgery using marginal procedure without any adverse impact on survival. The results of our limited clinical trial appear to justify further prospective, multicenter randomized trials of the benefits of caffeine combined with chemotherapy for nonmetastatic osteosarcoma and other malignant neoplasms.

[Renal hemangiopericytoma: report of a case]

A 34-year-old house wife presented with a right renal mass detected by work-up for epigastralgia. The mass located in the right renal sinus was round and approximately 3 cm in diameter. Although the tumor was well enhanced with contrast medium on CT scan, it was hypovascular on the early arterial phase of renal angiography. Translumbar radical nephrectomy was performed on suspicion of the right renal cell carcinoma. The tumor was solid and hard and, the cut surface of the tumor was homogenously colored pale pink. Microscopically it was hemangiopericytoma arising in the renal sinus, composed of well-developed pericytes and capillaries with so-called staghorn configuration, with invasion of hilar renal vein. Immunohistochemically, the hemangiopericytes were strongly positive for CD34, but negative for factor VIII associated antibodies. To our knowledge, the present patient is the 6th case in the Japanese literature and the first case with incidentally detected renal hemangiopericytoma.

Effect of FR143430, a novel cytokine suppressive agent, on adenocarcinoma colon26-induced cachexia in mice

Cancer cachexia, characterized by weight loss and progressive tissue wasting, has been postulated to be mediated by cytokines. In this study the effect of FR143430, (2-(4-fluorophenyl)-4, 5, 6, 7-tetrahydro-3-(4-pyridyl)pyrazolo[1, 5-a]pyrimidine monohydrochloride), an inhibitor of Interleukin-1 and Tumor necrosis factor-a (TNF- a), on adenocarcinoma colon26-induced cachexia was investigated in mice. Tumor growth was not affected. Nevertheless, treatment with FR143430 (0.1 to lmg) into the tumor resulted in the attenuation of the reduction in body weight, food intake, epididymal fat and carcass weight, the decrease in the circulating levels of triglyceride and glucose, and the increase in the circulating levels of total cholesterol, non esterified free fatty acid (NEFA) and total protein, which were induced by the presence of the tumor. However, oral treatment with FR143430 failed to show an inhibitory effect on cachexia induction. Overall, this study demonstrated that the cachexia induced by colon26 was alleviated by the injection of FR143430 into the tumor in sufficient quantity, without any effect on tumor growth, suggesting the potential utility of cytokine suppressive agents e for the treatment of cancer cachexia.

Regioselective syntheses of sulfated polysaccharides: specific anti-HIV-1 activity of novel chitin sulfates

A novel and convenient method for the regioselective syntheses of sulfated analogs of chitin and chitosan is described in relation to studies on structure-biological activity. Fully protected, soluble derivatives of chitosan were found to be useful intermediates for the syntheses of a novel class of sulfated polysaccharides, 2-acetamido-2-deoxy-3-O-sulfo-(1-->4)-beta-D-glucopyranan (3-sulfate, 3S, 4) and (1-->4)-2-deoxy-2-sulfoamido-3-O-sulfo-(1-->4)-beta-D-glucopyranan (2,3-disulfate, 23-S, 3). These compounds were tested for their activities in (i) inhibiting HIV-1 replication in vitro and (ii) inhibiting blood coagulation. The results reveal that the selective sulfation at O-2 and/or O-3 affords potent antiretroviral agents showing a much higher inhibitory effect on the infection of AIDS virus in vitro than that by the known 6-O-sulfated derivative (6-sulfate, 6S). Moreover, the 23-S product completely inhibited the infection of AIDS virus to T lymphocytes at concentrations as low as 0.28 microgram/mL without significant cytotoxicity. The regioselective introduction of sulfate group(s) at O-2 and/or O-3 had little effect on generating anticoagulant activity, whereas 6-O-sulfated chitin strongly inhibits blood coagulation. These results suggest that the specific interaction of these new types of chitin sulfates with gp 120 of the AIDS virus depends significantly on the sites of sulfation rather than on the total degree of substitution on sugar residues.

Induction of chronic inflammatory arthropathy and mesenchymal tumors in rats infected with HTLV-I

To compare the pathogenicity of HTLV-I derived from patients with HTLV-I-associated myelopathy (HAM)/tropical spastic paraparesis (TSP) and that from patients with adult T-cell leukemia (ATL), neonatal WKA rats were inoculated with either an HTLV-I-infected T-cell line (Fuk line) newly established from a HAM/TSP patient or MT-2 derived from a patient with ATL. Of 38 rats, 34 developed mesenchymal tumors (89%) only after 14 months of age, irrespective of the cell lines used. The rats inoculated with the Fuk line developed severe arthritis (27%) and anti-type II collagen antibody (64%), and less frequently, paraparesis (7%). Those inoculated with MT-2 developed paraparesis (23%), but not arthritis. Cyclophosphamide (CY) administration to induce immunosuppression in the Fuk line-inoculated rats increased the frequency of paraparesis (70%), but decreased the frequency of tumors (20%). HTLV-I proviral DNA was found in the spinal cord, sciatic nerves, tumors, and joints, whereas pX mRNA was detected in the sciatic nerves and tumors, but not in the spinal cord and joints. As a result, HTLV-I is considered to facilitate development of both chronic inflammatory arthropathy associated with autoimmunity and mesenchymal tumors in rats by experimental infection, and its pathogenicity is likely to be greatly influenced by the host immune state.