[Effect of extended thymectomy in myasthenia gravis of pure ocular type]

The effect of extended thymectomy in myasthenia gravis of pure ocular type was investigated in 13 patients, who were divided into the surgical group of nine and the conservative group of four. In the surgical group, the onset was at 47 +/- 20 years old. The preoperative duration of symptoms was 4 +/- 6 years. The age at the time of operation was 51 +/- 16 years old. Three patients had thymomas, including one malignant thymoma. Acetylcholine receptor antibody titer was over normal range with 34.0 +/- 49.7 nmol/l. No postoperative crisis occurred. The palliation rate of the surgical group was more higher through the whole period than that of the conservative group, and increased with progress of the course. The remission occurred in the surgical group, but did not in the conservative group. It took 7 months to improve the symptom in the surgical group, while 18 months in the conservative group. We conclude extended thymectomy is reasonable for patients with myasthenia gravis of pure ocular type.

Cloning and sequencing of agaA, a unique agarase 0107 gene from a marine bacterium, Vibrio sp. strain JT0107

An agarase gene (agaA) was cloned from genomic DNA of Vibrio sp. strain JT0107. An open reading frame of 2,985 nucleotides gave a primary translation product composed of the mature protein, agarase 0107 (975 amino acid residues, with a molecular weight of 105,271) and a signal peptide of 20 amino acid residues at the N terminus. Comparison of the deduced amino acid sequence of agarase 0107 with those of Streptomyces coelicolor and Pseudomonas atlantica suggests that these enzymes share two regions in common. The AgaA protein which was expressed in Escherichia coli had the agarase activity. Agarase 0107 hydrolyzes not only agarose but also neoagarotetraose [O-3,6-anhydro-alpha-L-galactopyranosyl (1-->3)-O-beta-D-galactopyranosyl(1-->4)-O-3,6-anhydro-alpha-L-galact opy ranosyl (1-->3)-D-galactose] to yield neoagarobiose [O-3,6-anhydro-alpha-L-galactopyranosyl(1-->3)-D-galactose]. This is a quite unique characteristic for a beta-agarase.

Histochemical localization of copper in the intestine and kidney of macular mice: light and electron microscopic study

Menkes' disease is an X-linked recessive disorder characterized by accumulation of copper in various organs and cells, such as the intestine, kidney, and cultured fibroblasts. Light and electron microscopic localization of Cu was investigated in the intestine and kidney of macular mice, an animal model of Menkes' disease, by a modified sulfide-silver method. Cu was accumulated in the cytoplasm of the absorptive epithelial cells, the vascular endothelium, and secretory granules of the Paneth cells. In kidney the distal tubule cells and glomeruli of both macular and control mice stained faintly, whereas the organelle-free cytoplasm in the proximal tubule cells of macular mice stained more intensely than those of controls. The nuclei, mitochondria, and lysosomes of the cells of macular mice hardly stained at all. These findings indicate that Cu is concentrated in the organelle-free cytoplasm of the affected cells of macular mice. This suggests that the Menkes' mutation affects Cu transport from the cytosol to the organelles in the cell.

Characterization of inhibitory activities and binding mode of synthetic 6'-modified methyl N-acetyl-beta-lactosaminide toward rat liver CMP-D-Neu5Ac: D-galactoside-(2-->6)-alpha-D-sialyltransferase

6'-Deoxy (12), 6'-thio (13), and 6'-O-tetrahydropyranosyl (14) analogues of methyl N-acetyl-beta-lactosaminide (3), were synthesized from lactose. NOE experiments proved that they adopt the same conformation as that of 3. Inhibition studies using these synthetic analogues, including the disulfide dimer 15, toward (2-->6)-alpha-sialytransferase (EC 2.4.99.1) revealed that the 6'-deoxy analogue 12 had remarkable inhibitory activity as the first acceptor-analogue inhibitor for this enzyme. It is noteworthy that the disulfide 15 also behaves as an inhibitor. The results indicated that chemical modification at the 6'-position of 3 did not cause much decrease in the binding affinity to the sialytransferase. Further, a novel possibility that the acceptor and the acceptor-analogue inhibitor can bind simultaneously to the sialytransferase was proposed based on the inhibition studies with 12 and CMP.

Intrapleural adaptive immunotherapy for breast cancer patients with cytologically-confirmed malignant pleural effusions: an analysis of 67 patients in Kyoto and Shiga Prefecture, Japan

Sixty-seven breast cancer patients with cytologically-confirmed malignant pleural effusion, who required intrapleural treatment, were analyzed retrospectively. The patients received their first thoracentesis between 1980 and 1990. Among them, 29 patients received intrapleural administration of OK-432, a streptococcal preparation, followed by the transfer of autologous pleural effusion lymphocytes cultured with interleukin-2. Other intrapleural treatments consisted of OK-432 alone (12 patients), chemotherapeutic agents alone (n = 9), a combination of OK-432 and chemotherapy (n = 16), or others (n = 1). Twenty-six of the 29 patients given OK-432 plus cultured effusion lymphocytes responded, while only 15 of the 38 patients who received other treatments did (p < 0.01). Median survival time and 5-year survival rate of patients who received OK-432 and cultured lymphocytes was 12 months and 36%, while those of the patients who received other treatments was 3 months and 0%, a significant (p < 0.001) difference in survival. Multivariate analysis using Cox's proportional hazard model revealed that the treatment (adoptive immunotherapy) was the most significant (p < 0.005) factor to prolong the survival of the patients among several prognostic factors. Thus, OK-432 and adoptive immunotherapy is a promising therapy that should be further evaluated in a prospective study.

Identification of new cystathionine mono-oxo acids, S-(3-oxo-3-carboxy-n-propyl) cysteine and S-(2-oxo-2-carboxyethyl) homocysteine, in the urine of a patient with cystathioninuria

Novel cystathionine mono-oxo acids, S-(3-oxo-3-carboxy-n-propyl) cysteine and S-(2-oxo-2-carboxyethyl) homocysteine, and cyclic amino acid, cystathionine ketimine, have been detected in the urine of a patient with cystathioninuria using liquid chromatography-mass spectrometry with an atmospheric pressure ionization interface system and an amino acid analyzer. To determine these cystathionine mono-oxo acids and cystathionine ketimine we took advantage of the selective absorbance at 380 nm of the phenylisothiocyanate-ketimine interaction product. The total concentrations of these compounds found in the urine samples of a cystathioninuric patient and six healthy subjects were respectively 3611.3 and 148.4 micrograms +/- 35.9/g of creatinine. The cystathioninuric patient excreted 20 times more cystathionine mono-oxo acids in the urine than healthy subjects.

In vivo determinations of carbamazepine and carbamazepine-10, 11-epoxide binding parameters to serum proteins in monotherapy patients

The in vivo serum protein binding parameters of carbamazepine (CBZ) and carbamazepine-10, 11-epoxide (CBZ-E), which was the main metabolite of CBZ in plasma, were determined in sera from 27 patients on CBZ monotherapy. Based on the results by recent studies, the authors assumed that CBZ and CBZ-E binding to serum proteins were composed of specific binding sites on alpha 1-acid glycoprotein (AAG) and albumin. Therefore, the authors determined the binding parameters of each compound by specific binding equation for two proteins. Association constants for drug-AAG binding were .071 L/mumol for CBZ and .016 L/mumol for CBZ-E. Conversely, those for drug-albumin binding were .00052 L/mumol for CBZ and .00072 L/mumol for CBZ-E. Within the investigated total concentration ranges in each compound, the AAG binding contributes largely to the drug-serum protein interactions. Furthermore, our results indicate that the albumin binding contributes to the nonsaturable serum protein binding of these compounds in the therapeutic range.

Changes in cystathionine gamma-lyase levels in rat liver during lactation

Rat liver cystathionine gamma-lyase activity increased rapidly with the onset of lactation, reaching a maximum value at week 2 and slowly decreasing thereafter. In non-lactating rats, from which the litters had been removed on the day of birth, the activity of this enzyme increased only minimally. The enzyme activity in the presence and absence of pyridoxal 5'-phosphate (PLP) did not differ significantly, indicating that the cystathionine gamma-lyase in lactating rat liver was also saturated with PLP as control rat. We then investigated whether the increased activity was caused by increases in the enzyme concentration. An antibody, prepared form purified rat liver cystathionine gamma-lyase was utilized for the detection of enzyme content by immunoblot analysis and enzyme immunoassay. On immunoblot analysis, this antibody stained purified cystathionine gamma-lyase, as well as staining a single polypeptide from liver cytosolic proteins that co-migrated with the purified enzyme at about 40 kDa. Changes in the staining intensity of the antibody paralleled the activity of the enzyme. The enzyme immunoassay showed that the content of liver cystathionine gamma-lyase at weeks 0, 1, 2 and 5 of lactation was 1.67, 2.33, 5.19, and 2.17 mg per g of liver, respectively, whereas in the non-lactating rats, the enzyme concentration at week 2 was found to be 2.20 mg per g of liver. The changes in enzyme concentration detected by enzyme immunoassay were also consistent with enzyme activity. We concluded that the increased cystathionine gamma-lyase activity in the lactating rat liver was a result of an increase in enzyme concentration.

[Surgical treatment of elderly patients with primary lung cancer]

Fourteen patients with lung cancer over the age of 70 years had the standard operation with mediastinal lymph node dissection. Their postoperative complications and prognoses were compared with those of 47 patients under the age of 70 years with the same operation. The propriety of the standard operation with mediastinal lymph node dissection for lung cancer in elderly patients was studied. A program of respiratory training was arranged preoperatively for the patients. Preoperative complications was more common in elderly than in younger patients, but postoperative complications were less frequent. The prognosis in elderly patients was also satisfactory. We conclude that the standard operation with mediastinal lymph node dissection for lung cancer can be performed as well in elderly as in younger patients.

[Transarterial immuno-chemotherapy including adoptive transfer of autologous cultured lymphocytes for stage IV breast cancer patients with locally-advanced tumor]

Immuno-chemotherapy via a catheter in the subclavian artery using sequential treatment with OK-432, chemotherapeutic agents (ADM, 5-FU), and cultured autologous lymphocytes, was performed for 9 Stage IV breast cancer patients with locally-advanced primary tumor. Tumor reduction of more than 50% was observed in 8 patients including 4 whose breast tumors had disappeared. Among 11 evaluable distant metastatic lesions, 7 (1 pleural effusion, 2 lung, 2 liver, 2 bone metastases) regressed after local immunotherapy of breast or additional regional immunotherapy (1 lung, 1 liver, 1 pleural effusion). Median survival time to date is 56 months. Five patients are currently alive, although 3 of them did not undergo mastectomy. Local immuno-chemotherapy may be useful because (a) toxicity is limited, (b) low doses of anti-cancer agents during the therapy (median dose of ADM, 60 mg) do not limit subsequent systemic chemotherapy, and (c) distant metastases often regress concomitantly with the primary lesions.

[Surgical treatment of pulmonary arteriovenous fistula: report of two cases]

Two patients with surgical intervention for pulmonary arteriovenous fistula were presented. Lobectomy was performed in a cyanotic patient and fistula excision in another. To prevent the unsatisfactory prognosis of pulmonary arteriovenous fistula, surgical treatment is preferable to drug therapy when the diagnosis of this disease is established. The operative method should be selected according to the size, shape and localization of pulmonary arteriovenous fistula.

The use of liquid chromatography-mass spectrometry for the identification and quantification of urinary iminodipeptides in prolidase deficiency

It has been reported that the urine of patients with prolidase deficiency contains various iminodipeptides with a carboxyl-terminal proline (hydroxyproline). These iminodipeptides have hitherto been detected indirectly by acid hydrolysis or enzymatic digestion, followed by amino acid analysis. In the present study, it was shown that X-Pro could be distinguished from Pro-X when the iminodipeptides were analysed directly by liquid chromatography coupled with atmospheric pressure ionization mass spectrometry (LC/API-MS), with scanning of the protonated molecule ions ([M+H]+). The same procedure also successfully quantified urinary iminodipeptides from patients with prolidase deficiency. A quantitative investigation of two siblings with prolidase deficiency revealed that the patient with severe clinical symptoms excreted more iminodipeptides than the other who did not have serious symptoms. LC/API-MS also revealed iminodipeptides (Gly-Hyp and Pro-Hyp) in the urine of the mother of the patients and in normal volunteers. Patients excreted much more Pro-Hyp than normal volunteers, whereas no quantitative differences were found between the mother and controls. In patients, the excretion of large quantities of X-Pro is due to their very low prolidase activity towards this type of substrate. In the erythrocytes of patients, prolidase activity towards X-Hyp was extremely low; even in the mother and normal volunteers, it was remarkably low in comparison with the activity against X-Pro.

[Morphological studies on liver in septic state by mice with E. coli injection into the abdominal cavity]

The purpose of this study is to elucidate morphological changes in septicemic mice induced by an injection of E. coli into the abdominal cavity and to discuss the relationship between the clinical findings and morphological ones. The liver of septicemic mice was morphologically demonstrated, a) Kupffer cells entrapped bacteria and erythrocytes, and large lysosomes were found in Kupffer cells, b) hepatocytes with low dense cytosol increased, and in the hepatocytes, many conglomerations of lysosome and cytolysome, and degeneration of rER, sER and mitochondria were identified, c) intercellular bile canaliculus became narrow. The conclusion is as follows: 1) the increase of the serum level of T. bili is caused by the increase of the phagocyte of erythrocytes by Kupffer cells and by the dysfunction of bile transformation and transportation in hepatocytes, 2) the increase of the serum level of GOT, GPT and LDH is caused by the degeneration of mitochondria in hepatocytes, 3) the decrease of the capacity to synthesize protein and lipid is due to the degeneration of cell organelles in hepatocytes.

[Role of surface tension lowering substances in the function of normal and diseased eustachian tubes of guinea pigs]

To examine the role of surface tension lowering substances (STLSs), we measured changes in passive opening pressure (OP) and closing pressure (CP) in eustachian tubes of guinea pigs before and after washing the tubes with various solutions (saline solution, artificial pulmonary surfactant, synthetic phospholipids, and detergent)). The percent decreases in OP and CP in tubes washed with artificial surfactant were significantly higher than those washed with saline solution. Those washed with synthetic phospholipids or detergent (Triton X-100) did not differ from those washed with saline solution. In guinea pigs with experimental otitis media produced by inoculation of formalin-killed Haemophilus influenzae into the middle ear cavity, the percent decreases in OP and CP in tubes washed with artificial pulmonary surfactant were significantly higher than in those washed with saline solution. Artificial pulmonary surfactant was injected into the middle ear cavity of the guinea pigs with otitis media. At 5 days after inoculation, the inflammatory changes of the middle ear were much milder in animals with intratemporal application of artificial pulmonary surfactant than in those with saline application. These results suggest the possible efficacy of treatment with artificial pulmonary surfactant for otitis media.

Sibling cases of a degenerative neurological disease associated with hypocupraemia and hypobetalipoproteinaemia

We describe two siblings, a boy and his younger sister, with degenerative neurological disturbances, hypocupraemia and hypobetalipoproteinaemia. The neurological features in both cases were developmental delay, dysarthria, hyperkinetics with an attention deficit, dysdiadochokinesis, night blindness, myoclonic jerks and convulsions. Their serum cooper levels did not increase despite administration of copper sulphate both orally or intravenously. The copper contents of the cultured fibroblasts in the patients were 1.5-fold that of controls. Although neurological disorders associated with abnormal copper metabolism and inherited in an X-linked manner have been previously reported, this is the first report of a neurodegenerative disease concurrent with abnormal copper metabolism and hypobetalipoproteinaemia.

In vivo binding characteristics of carbamazepine and carbamazepine-10,11-epoxide to serum proteins in paediatric patients with epilepsy

The in vivo serum protein binding characteristics of carbamazepine (CBZ) and carbamazepine-10,11-epoxide (CBZ-E) were assessed in sera from 23 paediatric patients on CBZ monotherapy. We assumed that CBZ and CBZ-E binding to serum proteins comprised specific binding sites on alpha 1-acid glycoprotein (AAG) and non-specific binding sites on serum albumin. Therefore, the binding characteristics of each compound were analysed according to specific and nonspecific binding equations. Association constants for drug-AAG binding were 0.096 l.mumol-1 for CBZ and 0.023 l.mumol-1 for CBZ-E. Within the concentration ranges investigated the specific binding of each compound contributes to the drug-serum protein interactions. Age did not show a significant correlation with the serum unbound fraction of each compound.

Activation of rainbow trout (Oncorhynchus mykiss) phagocytes by muramyl dipeptide

Immunoenhancing activity of synthetic muramyl dipeptide (MDP) was investigated in relation to the activation of rainbow trout (Oncorhynchus mykiss) phagocytes and to nonspecific protection against challenge with the fish pathogen Aeromonas salmonicida. Head kidney phagocytes collected from MDP-injected fish showed significant chemotactic activity against zymosan-activated normal rainbow trout serum, and phagocytic activities against both A. salmonicida and plastic beads. The MDP-activated phagocytes also showed enhanced superoxide generation. When normal phagocytes were exposed to supernatants of phagocyte or peripheral blood lymphocyte cultures of MDP-injected fish, the cells showed significant chemotactic activity, indicating that the MDP-activated cells produced phagocyte-activating factor. Injection of MDP to fish provided protection against challenge with virulent A. salmonicida.

Expression and function of c-Kit in fetal hemopoietic progenitor cells: transition from the early c-Kit-independent to the late c-Kit-dependent wave of hemopoiesis in the murine embryo

The protooncogene c-kit encodes a receptor type tyrosine kinase and is allelic with the W locus of mice. SLF, the c-Kit ligand which is encoded by the Sl locus, has growth promoting activity for hemopoietic stem cells. Previous studies demonstrated that c-Kit is functionally required for the proliferation of hemopoietic progenitor cells at various differentiation stages in adult bone marrow. However, the absence of functional SLF and c-Kit in fetuses with mutant alleles of Sl and W loci produces only minor effects on the myeloid and early erythroid progenitor cells in the fetal liver, although the level of the late erythroid progenitor cells is significantly affected. We used an anti-c-Kit monoclonal antibody to investigate the expression and function of c-Kit in murine fetal hemopoietic progenitor cells. Flow-cytometric analysis showed that hemopoiesis in the yolk sac and fetal liver started from cells that express c-Kit. The c-Kit expression decreased upon maturation into erythrocytes in each organ. By fluorescence activated cell sorting, the c-Kit+ cell population was enriched with the hemopoietic progenitor cells clonable in vitro (CFU-E, BFU-E and GM-CFC). To elucidate whether c-Kit functions in these progenitor cells in vivo, we took advantage of the antagonistic anti-c-Kit monoclonal antibody, ACK2, which can block the function of c-Kit. Administration of ACK2 after 12.5 days of gestation rapidly eliminated BFU-E and GM-CFC as well as CFU-E from the fetal liver. However, the number of these progenitor cells in the yolk sac and fetal liver was less affected when the fetuses were given ACK2 before 12.5 days of gestation. Our results provide evidence that there are two waves of hemopoiesis in murine embryos relative to c-Kit dependency. The c-Kit has an essential role on the growth of hemopoietic progenitor cells in the fetal liver after 12.5 days of gestation, whereas the progenitor cells in the liver and yolk sac of the earlier embryo do not depend on c-Kit and its ligand SLF.

Cell surface C-reactive protein of rainbow trout lymphocytes

C-reactive protein (CRP) expressed on rainbow trout (Oncorhynchus mykiss) lymphocytes was investigated to determine what role CRP might have on lymphocyte function. C-reactive protein was detected on the surface (S-CRP) of 25% of peripheral blood lymphocytes (PBL) and 4% of head kidney lymphocytes (HKL) by flow cytometry of cells labelled with biotinylated rabbit anti-rainbow trout CRP IgG and fluorescent-coupled avidin. Purified CRP, when added to cells in culture, bound to both PBL and HKL. Stimulation of PBL and HKL by concanavalin A, phytohemagglutinin, or lipopolysaccharide increased the percentage of S-CRP-positive cells, which suggests the production of CRP by lymphocytes. Treatment of lymphocytes with anti-rainbow trout CRP IgG and complement decreased the number of S-CRP-positive cells.

Identification of N-acetyl-alpha-aminoadipic acid in the urine of a patient with alpha-aminoadipic and alpha-ketoadipic aciduria

A 3.5-year-old Japanese boy with a mild speech disturbance excreted a large amount of alpha-aminoadipic acid into the urine. The amino acid analysis using an amino acid analyser confirmed the presence of alpha-aminoadipic acid in both urine and plasma. We detected alpha-aminoadipic acid in the hydrolysate of the effluent and washwater fraction through cation exchange resin. This suggested the presence of acetylated derivatives and we identified N-acetyl-alpha-aminoadipic acid using liquid chromatography-atmospheric pressure ionization mass spectrometry (LC-API-MS). The concentrations of alpha-aminoadipic acid and N-acetyl-alpha-aminoadipic acid in the urine of a patient with alpha-aminoadipic aciduria were 376.9 nmol/mg creatinine and 18.1 nmol/mg creatinine, respectively. We also detected alpha-ketoadipic acid in the urine of this patient using LC-API-MS.

Recent developments in Menkes disease

Recent studies on Menkes disease are reviewed, focusing especially on copper transport in the cells. A large amount of copper accumulated in the organelle-free cytoplasm, whereas mitochondria were in a state of copper deficiency, indicating that Menkes mutation probably affects copper transport from the cytosol to the organelles in the cells. Microscopic observation of the brain of the macular mouse showed that copper accumulates in the blood vessels. Observation of the brain tissue of the macular mouse after intraventricular administration of copper revealed that copper accumulates in the glia as well as the blood vessels. Copper accumulation was also observed in cultured astrocytes, a type of glial cell, indicating that the affected astrocytes accumulate blood-borne copper and release little of it in the patients with Menkes disease. Thus the effective treatment of Menkes disease could possibly be to release trapped copper from the blood vessels and glia into the neurons.

Cellular interaction against autologous tumor cells between IL-2-cultured lymphocytes and fresh peripheral blood lymphocytes in patients with breast cancer given immuno-chemotherapy

In patients with Stage II or III breast cancer and in patients with liver metastases from breast cancer, we examined cellular interaction in the cytotoxicity against autologous tumor cells by interleukin-2(IL-2)-cultured lymphocytes (CL) and fresh peripheral blood lymphocytes (FPBL) treated with immunochemotherapy including OK-432 and cyclophosphamide. In flow cytometric analysis, CD8+CD11b+ and CD16+ cells significantly decreased after immuno-chemotherapy in both groups of patients. A protocol study in Stage II or III breast cancer patients showed suppressive activity of FPBL on the cytotoxic activity of CL in 3/9 of the non-treatment group but no suppressive activity and enhancing activity in 3/7 in the immuno-chemotherapy group. Moreover, in 19 patients with liver metastases from breast cancer treated with immuno-chemotherapy including adoptive immunotherapy, FPBL in 6/19 showed enhancing activity, and in 8/19 suppressive activity in the lysis of autologous tumor cells. In assays in vitro using autologous and allogeneic tumor cells, FPBL showed a partial specificity in cellular interaction against autologous tumor cells. CD4-depleted FPBL inhibited cytotoxicity of CL, while CD8-depleted FPBL enhanced cytotoxicity of CL in patients with liver metastases. These results suggest that immuno-chemotherapy eliminates the suppressive population in FPBL and may induce tumor regression if combined with adoptive immunotherapy using CL.

Central nervous system involvement of adult T-cell leukemia-lymphoma with multinucleated giant cells in the brain, skin, and kidney

BACKGROUND

A case of central nervous system (CNS) involvement in a patient with adult T-cell leukemia-lymphoma (ATLL) with multinucleated giant cells (MNGC) is presented.

METHODS

A 48-year-old woman with human T-lymphotropic virus type I (HTLV-I) antibody titer had multiple focal brain symptoms and skin eruptions without lymphadenopathy, hepatosplenomegaly, or increased abnormal lymphocytes in the peripheral blood. No spastic paraparesis of the lower limbs was found. The encephalopathy was progressive, and she died 5 months later despite repeated intrathecal administration of methotrexate, cytosine arabinoside, and prednisolone and monthly systemic chemotherapy with doxorubicin, cyclophosphamide, vincristine, and prednisolone.

RESULTS

Postmortem examinations identified unusual ATLL lesions composed of marked infiltrations of atypical mononuclear cells and bizarre MNGC with histiocytic granulomatous reactions in the leptomeninges, brain tissues along the Virchow-Robin spaces, skin, and kidney. Immunohistochemical stains confirmed the T-cell nature of such mononuclear cells and partially T-cell and partially macrophage nature of the MNGC, although no evidence of HTLV-I expression was found.

CONCLUSIONS

ATLL presenting with CNS symptoms is rare. It was assumed that the direct cytopathic effects of HTLV-I were responsible for the formation of the MNGC after considering the similarity with MNGC in encephalopathy caused by the human immunodeficiency virus.