A Comparative Study of the RAPINA and the Virus-Neutralizing Test (RFFIT) for the Estimation of Antirabies-Neutralizing Antibody Levels in Dog Samples

The mass vaccination of dogs against rabies is a highly rational strategy for interrupting the natural transmission of urban rabies. According to the World Organization for Animal Health (OIE) and the World Health Organization (WHO), the immunization of at least 70% of the total dog population minimizes the risk of endemic rabies. Knowledge of the virus-neutralizing antibody (VNA) level against the rabies virus (RABV) is required to evaluate protective immunity and vaccine coverage of dogs in the field. The rapid focus fluorescent inhibition test (RFFIT) and the fluorescent antibody virus neutralization (FAVN) test are recommended by OIE and WHO to determine the VNA levels in serum. However, these tests are cell culture based and require the use of live viruses and specialized equipment. The rapid neutralizing antibody test (RAPINA) is a novel, immunochromatographic test that uses inactivated virus to estimate the VNA level qualitatively. It is a simple, rapid and inexpensive, although indirect, assay for the detection of VNA levels. The RAPINA has shown good positive and negative predictive values and a high concordance with the RFFIT results. In this study, we compared the performance of the two tests for evaluating the vaccination status of dogs in the Philippines, Thailand and Japan. A total of 1135 dog sera were analysed by the RAPINA and compared to the VNA levels determined by the RFFIT. The overall positive and negative predictive values of the RAPINA were 96.2-99.3% and 84.5-94.8%, respectively, with a concordance (kappa) of 0.946-0.97 among the three countries. The RAPINA results were highly homologous and reproducible among different laboratories. These results suggest that this test is appropriate to survey vaccination coverage in countries with limited resources.

Bufavirus genotype 3 in Turkish children with severe diarrhoea

Recently a parvovirus called bufavirus (BuV) has been implicated as a causative agent of diarrhoea. To further reveal the epidemiology and genetic characteristics of BuV, this study was performed in Turkish children with diarrhoea. BuV was detected in 1.4% (8/583) of stool samples. All stool samples from healthy children (n = 148) were negative for BuV. Diarrhoea in BuV-positive patients was severe and occurred mainly during the colder months of the year. Complete genome sequences were generated from four BuVs. Only BuV3 was found, which was genetically and phylogenetically similar to Bhutanese BuV3, indicating that BuV3 is prevalent in Asian countries.

Neurogenic cardiomyopathy in rabbits with experimentally induced rabies

Cardiomyopathies have been rarely described in rabbits. Here we report myocardial necrosis of the ventricular wall in rabbits with experimentally induced rabies. Myocardial lesions were found only in rabbits with brain lesions, and the severity of the cardiac lesions was proportional to that of the brain lesions. Neither the frequency nor the cumulative dose of anesthesia was related to the incidence or the severity of the myocardial lesions. The myocardial lesions were characterized by degeneration and/or necrosis of myocardial cells and were accompanied by contraction band necrosis, interstitial fibrosis, and infiltration of inflammatory cells. The brain lesions due to rabies virus infection were most prominent in the cerebral cortex, thalamus, hypothalamus, brainstem, and medulla. Rabies virus antigen was not found in the hearts of any rabbits. Based on these findings, the myocardial lesions were classified as neurogenic cardiomyopathy.

Oral administration of an HSP90 inhibitor, 17-DMAG, intervenes tumor-cell infiltration into multiple organs and improves survival period for ATL model mice

In the peripheral blood leukocytes (PBLs) from the carriers of the human T-lymphotropic virus type-1 (HTLV-1) or the patients with adult T-cell leukemia (ATL), nuclear factor kappaB (NF-κB)-mediated antiapoptotic signals are constitutively activated primarily by the HTLV-1-encoded oncoprotein Tax. Tax interacts with the I κB kinase regulatory subunit NEMO (NF-κB essential modulator) to activate NF-κB, and this interaction is maintained in part by a molecular chaperone, heat-shock protein 90 (HSP90), and its co-chaperone cell division cycle 37 (CDC37). The antibiotic geldanamycin (GA) inhibits HSP90's ATP binding for its proper interaction with client proteins. Administration of a novel water-soluble and less toxic GA derivative, 17-dimethylaminoethylamino-17-demethoxygeldanamycin hydrochloride (17-DMAG), to Tax-expressing ATL-transformed cell lines, C8166 and MT4, induced significant degradation of Tax. 17-DMAG also facilitated growth arrest and cellular apoptosis to C8166 and MT4 and other ATL cell lines, although this treatment has no apparent effects on normal PBLs. 17-DMAG also downregulated Tax-mediated intracellular signals including the activation of NF-κB, activator protein 1 or HTLV-1 long terminal repeat in Tax-transfected HEK293 cells. Oral administration of 17-DMAG to ATL model mice xenografted with lymphomatous transgenic Lck-Tax (Lck proximal promoter-driven Tax transgene) cells or HTLV-1-producing tumor cells dramatically attenuated aggressive infiltration into multiple organs, inhibited de novo viral production and improved survival period. These observations identified 17-DMAG as a promising candidate for the prevention of ATL progression.

Influence of age and duration of infection on bacterial load and immune responses to Helicobacter pylori infection in a murine model

Using a murine model, we previously showed that Helicobacter pylori infects and colonizes offspring via maternal transmission during the nursing period. The aim of this study was to investigate the influence of age and duration of infection on inflammatory and immune responses to H. pylori in infant and adult mice. During the breast-feeding period, the number of bacteria was significantly suppressed in 1-week-old mice infected with H. pylori at an early stage of nursing, compared with adult mice, suggesting that breast-milk induces such low colonization. In addition, these mice had weaker gastric inflammation, especially Th1 cytokine and humoral responses than in mice infected with H. pylori after weaning in spite of elevated levels of Th1 cytokines. Although infant mice showed low inflammatory responses against H. pylori, they produced H. pylori-specific antibodies following vaccination with oral or parenteral adjuvant. Our results suggest the importance of age at the time of primary infection on bacterial load, gastric inflammation and humoral responses in a murine model of H. pylori infection.

CTLA-4 blockade inhibits induction of Helicobacter pylori-associated gastritis in mice

The balance between Th1 and Th2 response determines the outcome of Helicobacter pylori infection. Interferon (IFN)-gamma plays an inductive role in gastric inflammation, whereas interleukin (IL)-4 counterbalances Th1 response and suppresses the development of gastritis. Th cell response is regulated by co-stimulatory factors. A co-stimulatory molecule, cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), plays an inhibitory role in IL-2-dependent cell growth and mediates an optimal inhibitory signal to Th1 and Th2 cells. We administered anti-CTLA-4 monoclonal antibody (MoAb), which blocks CTLA-4 signalling, to examine the relative role for this signalling during maturation of Th1 and Th2 cells in H. pylori infection in mice. Mice treated by anti-CTLA-4 MoAb within the first week of infection showed an inhibition of gastric inflammation, accompanied by an increasing ratio of H. pylori-specific IgG1/IgG2a in serum following infection. Furthermore, the treatment resulted in the higher ratio of IL-4/IFN-gamma by splenocytes in response to H. pylori antigen at 6 weeks after infection, compared with untreated mice. These results suggest that the predominance of Th2 response by CTLA-4 blockade leads to an inhibition of the development of gastric inflammation. CTLA-4 signalling could contribute to the regulation of Th subsets and the development of gastric inflammation in H. pylori infection.

Childhood Helicobacter pylori infection in a murine model: maternal transmission and eradication by systemic immunization using bacterial antigen-aluminium hydroxide

In humans, transmission of Helicobacter pylori is thought to occur largely during childhood. Infected mothers are generally considered to be the main source of the pathogen. However, little is known about when and how often maternal transmission of H. pylori occurs during childhood. In the present study, we examined these issues in an experimental murine model. Pregnant C57BL/6 mice, infected experimentally with H. pylori, delivered and nursed their litters. The stomachs of the infants were isolated and assessed for transmission of H. pylori. We also investigated the effect of systemic immunization using H. pylori antigen-aluminium hydroxide (AlOH) with regard to providing anti-H. pylori immunity and eradicating the maternally transmitted bacteria in infants. Polymerase chain reaction (PCR) was used to examine the presence of transmitted bacteria and their eradication. Maternal transmission of H. pylori varied widely during the nursing period, but almost all litters showed bacterial transmission at 2 weeks postpartum. Systemic immunization with bacterial antigen-AlOH eradicated the bacteria in most litters; this immunization induced a local decrease of Th2 cytokines and a local increase of Th1 cytokines in the gastric tissue, as determined by ELISA. Our results indicate that our H. pylori vaccine provides not only protection, but also eradication of the already transmitted H. pylori.

Hepatitis B virus harboring nucleotide deletions in the core promoter region and genotype B correlate with low viral replication activity in anti-HBe positive carriers

BACKGROUND

Emergence of anti-HBe following seroconversion of HBe antigen indicates reduced hepatitis B virus (HBV) replication in the liver and low infectivity in the natural course of infection. However, some patients show continued replication or reactivation even in the presence of anti-HBe.

OBJECTIVE

To clarify the cause of HBV replication, we investigated genotype differences and mutations in the core promoter and precore region in relation to virus titer.

STUDY DESIGN

Using quantification of HBV DNA, nucleotide sequencing of the core promoter and precore region, and genotyping with the S gene by restriction fragment length polymorphism (RFLP), we analyzed sera of 26 anti-HBe positive carriers (28 serum samples).

RESULTS

Various mutations were detected including C to T point mutation at nt 1653, A to T and G to A contiguous point mutations at nt 1762 and 1764 in the core promoter region, and G to A point mutation at nt 1896 in the precore region, but no common mutations were detected that were directly related to the virus titer from earlier reported mutations. In contrast, the mean titer of genotype B virus was 1.5 x 10(5) copies per ml and that of mutant HBV of genotype C having 8 base pairs (8-bp) deletion (nt 1768-1775) in the core promoter region was 7.9 x 10(4) copies per ml (mean titer). These titers showed commonly lower than that of genotype C virus without 8-bp deletion (median titer 5.0 x 10(6) copies per ml). Transition of genotype from C to B after viral reactivation and reduction of proportion of 8-bp deletion mutant at reactivation period was observed in a patient who demonstrated exacerbation of liver dysfunction due to immunosuppressive therapy and increased viral replication.

CONCLUSIONS

These results confirm those of our earlier study describing low replication ability of 8-bp deletion mutant HBV in vitro, and also indicate that the presence of genotype B correlates with reduced titer of HBV.

Comparison of genomic structures and antigenic reactivities of orthologous 29-kilodalton outer membrane proteins of Helicobacter pylori

We purified a 29-kDa Helicobacter pylori outer membrane protein (Omp29 protein) and cloned the gene encoding the protein from H. pylori strain ATCC 43504. The Omp29 gene corresponded to the reported JHP73 and the HP78-79 genes of H. pylori strains. A corresponding nucleotide fragment was detected in all 150 tested H. pylori clinical isolates by PCR or Southern blotting. The amplified Omp29-corresponding fragments were categorized into a ca. 770-bp-long group and a larger-fragment group. Sequence analysis indicated that the larger fragments were likely synthesized from the 770-bp fragments by insertion of an irrelevant fragment via 17-bp-long repeat sequences. Immunoblot analysis implies that the ca. 770-bp fragment is responsible for the protein homologous to Omp29, whereas the larger fragments are not responsible for those proteins or encoding antigenically distinct proteins. We postulate that the H. pylori outer membrane protein Omp29 can alter its antigenicity through gene modifications mediated by nucleotide transfer.

Immunoglobulin G and M hepatitis C virus core antibody (JCC.2) response in chimpanzees infected experimentally with hepatitis C virus

OBJECTIVE

To evaluate changes in serum immunoglobulin M (IgM) and G (IgG) hepatitis C virus (HCV) core antibodies after HCV infection in acute hepatitis C.

METHODS

Serum HCV RNA and IgM and IgG HCV core antibodies were investigated using sera sequentially sampled from three chimpanzees experimentally infected with HCV. Serum IgG HCV core antibody titer was measured using a JCC.2 enzyme-linked immunosorbent assay (ELISA) kit (Chemo-Sera-Therapeutic Research Center, Kumamoto, Japan). IgM core antibody titer was measured using horseradish peroxidase-labeled monoclonal anti-human IgM as the secondary antibody for the JCC.2 ELISA kit. Serum HCV RNA was detected using the 5' noncoding region as the primer according to the reverse transcriptase (RT) nested polymerase chain reaction (PCR) and competitive RT-PCR method.

RESULTS

IgM JCC.2 antibody was detected when alanine aminotransferase (ALT) peaked, showing the closest correlation with the changes in ALT. A period during which IgM JCC.2 antibody was positive but HCV RNA as determined by RT-nested PCR was negative was observed after the elevation of ALT level.

CONCLUSION

These results indicate the usefulness of detection of serum IgM JCC.2 antibody in making a definitive diagnosis of acute hepatitis C and the follow-up observation of hepatitis C.

Effects of zinc acetate on splenocytes of endotoxemic mice: enhanced immune response, reduced apoptosis, and increased expression of heat shock protein 70

Immune function is markedly attenuated in endotoxemia. Zinc is involved in the regulation of cellular functions and maintenance of immune function, and its level in the serum is low in endotoxemia. We mainly investigated the effects of zinc acetate (ZA) on splenocytes in mice with endotoxemia. After we confirmed increased plasma zinc level by ZA treatment, C57BL/6 mice were randomly divided into four groups: 10 control mice received 500 microL saline solution as vehicle; 10 control mice received ZA at 3 mg/kg body weight; 20 endotoxemic mice received a 40 mg/kg lethal dose of lipopolysaccharide (LPS); 20 mice received ZA followed by LPS as the above dose. In vivo, we confirmed that ZA pretreatment did not significantly affect the plasma cytokine level in endotoxemic mice. In vitro, splenocytes from ZA-plus-LPS mice showed drastic effects, in that ZA abrogated LPS-induced suppression of cellular proliferation and production of interleukin-2 and interferon-gamma. The percentage of apoptotic splenocytes was significantly reduced in ZA-plus-LPS mice (23.4%) as compared with LPS mice (41.6%). Furthermore, the expression of HSP-70 mRNA in splenocytes was strongly enhanced in both ZA and ZA-plus-LPS mice, especially in the latter group. Finally, studies monitoring survival rates for 6 days showed that LPS caused 100% mortality while ZA-plus-LPS mice showed 75% survival. Our results suggest that zinc normalized the immune response and reduced apoptosis of splenocytes. These changes were probably caused by increased synthesis of HSP-70 by splenocytes, which might enhance survival of mice with LPS-induced endotoxemia.

Reduced transcription and progeny virus production of hepatitis B virus containing an 8-bp deletion in basic core promoter

We have demonstrated previously the presence of an 8-bp deletion mutant, spanning from nt. 1768 to nt. 1775 in the basic core promoter region of hepatitis B virus (HBV) in patients with anti-HBe positive asymptomatic phase before developing acute exacerbation after immunosuppressive treatment. The transcription and progeny virus production activities of the mutant were examined by transfection of the recombinant plasmid [pUC Del(2)] containing the head-to-tail dimer DNA of the mutant into HepG2 cells. The amounts of hepatitis B surface antigen (HBsAg) and HBe antigens secreted into the culture medium were markedly reduced. Southern blotting of DNAs extracted from the culture medium also showed reduced mutant activity to produce progeny virus. Northern blotting and RNase protection assay of RNAs extracted from transfected cells demonstrated that the transcription of both precore mRNA and pregenome RNA was reduced significantly compared to that of wild-type HBV. The promoter activity examined by transfection of the CAT plasmid containing deletion mutant DNA was much lower than that of wild type. Co-transfection experiments, however, of the CAT plasmid containing wild-type DNA with pUC Del(2) reduced CAT activity induced by wild-type, suggesting that truncated X protein produced by the mutant does not possess a sufficient transactivating activity. Gel shift assay using HepG2 nuclear extract and a probe containing four TA-rich regions in CP and various competitors suggested that the lack of the third TA-rich region was responsible for the transcription reduction of precore mRNA and pregenome RNA. The possible mechanisms are discussed.

Reduced transcription and progeny virus production of hepatitis B virus containing an 8-bp deletion in basic core promoter

We have demonstrated previously the presence of an 8-bp deletion mutant, spanning from nt. 1768 to nt. 1775 in the basic core promoter region of hepatitis B virus (HBV) in patients with anti-HBe positive asymptomatic phase before developing acute exacerbation after immunosuppressive treatment. The transcription and progeny virus production activities of the mutant were examined by transfection of the recombinant plasmid [pUC Del(2)] containing the head-to-tail dimer DNA of the mutant into HepG2 cells. The amounts of hepatitis B surface antigen (HBsAg) and HBe antigens secreted into the culture medium were markedly reduced. Southern blotting of DNAs extracted from the culture medium also showed reduced mutant activity to produce progeny virus. Northern blotting and RNase protection assay of RNAs extracted from transfected cells demonstrated that the transcription of both precore mRNA and pregenome RNA was reduced significantly compared to that of wild-type HBV. The promoter activity examined by transfection of the CAT plasmid containing deletion mutant DNA was much lower than that of wild type. Co-transfection experiments, however, of the CAT plasmid containing wild-type DNA with pUC Del(2) reduced CAT activity induced by wild-type, suggesting that truncated X protein produced by the mutant does not possess a sufficient transactivating activity. Gel shift assay using HepG2 nuclear extract and a probe containing four TA-rich regions in CP and various competitors suggested that the lack of the third TA-rich region was responsible for the transcription reduction of precore mRNA and pregenome RNA. The possible mechanisms are discussed.

Therapeutic oral vaccination induces mucosal immune response sufficient to eliminate long-term Helicobacter pylori infection

We examined the efficacy of therapeutic oral vaccination using Helicobacter pylori-whole cell sonicate and cholera toxin (CT) in mice persistently infected with H. pylori. Efficacy was determined by bacterial culture and microscopic examination of gastric tissues for the persistence of bacteria at 6 weeks after the last vaccination. Vaccination of H. pylori-whole cell sonicate combined with CT eradicated bacteria in 10/16 mice (62.5%). Interestingly, oral vaccination with CT alone also eliminated the bacteria in 8/17 mice (47.1%). However, a therapeutic intraperitoneally administered vaccine failed to eradicate H. pylori from the stomach (1/17 mice, 5.9%). Identification of the type of immunity involved in the eradication process showed that oral vaccination enhanced the antigen-specific IgA in the feces and saliva. The efficacy of eradication of H. pylori correlated well with increases in IgA secretion in mucosal tissue and a higher labeling index of IgA-positive lumina of pyloric glands. Moreover, the expression of IL-4 mRNA in the stomach of mice with eradicated bacteria was higher than in the uneradicated group. Our results suggest that the efficacy of vaccination depends on the mucosal IgA response in the gastrointestinal tract against H. pylori via Th2 cell activation and that therapeutic oral vaccination induces a mucosal immune response sufficient to eradicate long-term infection with H. pylori.

Divergence of virulence factors of Helicobacter pylori among clinical isolates does not correlate with disease specificity

The aim of this study was to examine the relation between disease specificity and the virulence factors of Helicobacter pylori isolated from patients with gastric cancer (GC), duodenal ulcer (DU), and gastritis (GS). Altogether 18 isolates obtained from patients with GC, 28 isolates from DU patients, and 13 isolates from GS patients were analyzed. All isolates were tested for the presence of the cagA gene, and genotyping of the vacA gene was done by the polymerase chain reaction. Production of VacA protein and expression of vacuolating cytotoxic activity in the H. pylori culture supernatant were examined. The serum antibody titers against purified VacA and CagA proteins were determined by enzyme-linked immunosorbent assay (ELISA). Interleukin-8 (IL-8) production by AGS cells in response to H. pylori isolates was measured by an hIL-8 ELISA kit. Genetic analysis of vacA revealed that most of the clinical isolates were classified into the S1a type by signal sequence typing. There were no differences in cagA detection rates, vacuolating cytotoxin activity, or mean antibody titers against VacA and CagA protein among the three groups. The mean IL-8 concentrations in the supernatants of AGS cells were similar in the three groups. In this study, there was no difference in virulence factors of H. pylori among isolates from GC, DU, and GS.

Analysis of p53 gene mutations in Helicobacter pylori-associated gastritis mucosa in endoscopic biopsy specimens

BACKGROUND

No previous report has shown the relationship between Helicobacter pylori infection and a direct sequence analysis of p53 gene mutation in a biopsy sample of human gastric mucosa.

METHODS

A total of 60 endoscopic biopsies samples (21 patients with H. pylori-positive gastritis and 9 patients with H. pylori-negative gastritis), including antral mucosa and corpus mucosa, were used in this study. Direct DNA sequencing of exons 5, 6, 7, and 8 of the p53 gene was performed by the dyedeoxy terminator method.

RESULTS

Mutations in the p53 gene were identified in non-hot spot codons in exon 7 and 8 in 11 of 21 samples (52.4%) from H. pylori-positive gastritis patients. There was no mutation in H. pylori-negative gastritis patients.

CONCLUSIONS

This finding shows that H. pylori infection can induce p53 point mutations and appears to be involved in the pathway leading to dysplasia or carcinoma.

Local secretory immunoglobulin A and postimmunization gastritis correlate with protection against Helicobacter pylori infection after oral vaccination of mice

C57BL/6 mice were orally immunized with five weekly doses of 2 mg, 200 microgram, or 2 microgram of Helicobacter pylori (Sydney strain) whole-cell sonicate combined with cholera toxin. One week after the last vaccination, mice were challenged with 5 x 10(7) CFU of live H. pylori three times at 2-day intervals. At 6 or 18 weeks after the challenge, mice were sacrificed and bacterial cultures and histological studies of the stomach were performed. Vaccination with 2 mg/session or 200 microgram/session inhibited H. pylori colonization by 90 and 100%, respectively. These mice were considered protected. Lower levels of H. pylori-specific immunoglobulin A (IgA) were detected in fecal and saliva samples before challenge. However, a significant increase in IgA secretion in mucosal tissue and a higher labeling index for IgA-positive lumina of pyloric glands were noted in these mice in response to challenge and in a vaccine dose-dependent manner. In protected mice, however, severe gastritis characterized by marked infiltration of inflammation mononuclear cells was noted at 6 weeks after challenge, compared with the gastritis seen in unprotected mice or nonvaccinated, ordinarily infected mice. Marked expression of gamma interferon mRNA was detected in the stomach of all protected mice, and 50% of these mice expressed interleukin 4 (IL-4) or IL-5 mRNA. Our findings suggest that local secretory IgA antibody and severe postimmunization gastritis correlate well with protection of mice against H. pylori infection.

Serological assessment of the early response to eradication therapy using an immunodominant outer membrane protein of Helicobacter pylori

Eradication of Helicobacter pylori infection cures gastritis and prevents recurrence of peptic ulcers. Endoscopy is usually used to evaluate the effectiveness of eradication therapy. We designed a new noninvasive assay system for the early evaluation of eradication of H. pylori infection in which a crude H. pylori outer membrane protein preparation (HPOmp) is used as an antigen, and we determined the sensitivity and specificity of the serological assay system. Immunoblot analysis showed that anti-HPOmp antibodies reacted to a protein with a molecular mass of approximately 29 kDa. In those patients who responded to therapy, the anti-HPOmp immunoglobulin G (IgG) titers measured by enzyme-linked immunosorbent assay (ELISA) at 1 month after the end of therapy were significantly lower than those before treatment (34.8% reduction; P < 0.001), and the posttreatment reduction in the antibody titer was significantly greater than that of the titer measured with a commercially available anti-H. pylori IgG ELISA (34.8% versus 16.1%; P < 0.001). When a 25% reduction of anti-HPOmp IgG titer at 1 month after the end of treatment was taken as the cutoff value for H. pylori eradication, the sensitivity and specificity of our new assay were 75% (51 of 68 treatment responders) and 96% (22 of 23 nonresponders), respectively. Our results indicate that the novel serological test with HPOmp might be a clinically useful tool for assessment of eradication of H. pylori.

Diversity in protein synthesis and viability of Helicobacter pylori coccoid forms in response to various stimuli

The viability of the coccoid forms of Helicobacter pylori was evaluated by assessing protein synthesis. Metabolic labeling studies showed the synthesis of proteins and the specific protein profiles of H. pylori coccoids produced under various conditions. Harsh conditions such as aerobiosis and starvation (lack of horse serum) in the culture did not affect the synthesis of proteins in the coccoids. Lowering of the pH to that of gastric secretions induced expression of several proteins in the coccoids. However, the coccoids produced under prolonged microaerobic conditions exhibited a profile of acid stress-induced protein expression different from that induced by aerobiosis or starvation. Our data suggest that coccoid H. pylori exhibits diversity in viability following exposure to different stresses and that the response to acid stress of coccoid H. pylori could be involved in infection of the host stomach.

Development of Helicobacter pylori-induced gastric carcinoma in Mongolian gerbils

Helicobacter pylori is classified by IARC/WHO as a definite human gastric carcinogen, despite "inadequate experimental evidence." To obtain direct evidence concerning this relationship, we investigated the histopathological findings of gastric mucosa using a model of H. pylori infection in Mongolian gerbils. The animals were challenged p.o. with H. pylori ATCC-43504 and sacrificed at 6, 12, and 18 months after inoculation for histological examination. All inoculated animals were infected with H. pylori. Severe infiltration of the lamina propria by polymorphonuclear and mononuclear cells appeared in the lesser curvature of the antrum, with an increase in epithelial cell proliferation, and the infiltration extended to the body. Atrophic gastritis and focal intestinal metaplasia also appeared in the lesser curvature of the antral mucosa at 6 months after inoculation. Intestinal metaplasia became severe, with dysplasia, after that. At 18 months after H. pylori inoculation, two of five infected animals showed three well-differentiated gastric cancers. The uninfected control animals showed no abnormal findings throughout the entire observation period. Here, it was confirmed that H. pylori infection alone causes gastric cancer in an animal model.

In vitro cytotoxic effects of vacuolating cytotoxin produced by clinical isolates of Helicobacter pylori

The vacuolating cytotoxin produced by Helicobacter pylori is considered to be one virulence factor causing peptic ulceration. In this study, we examined the activity of vacuolating cytotoxin in induction of intracellular vacuolation of rabbit gastric epithelial cells (RGECs). We used culture supernatants of H. pylori as a source of vacuolating cytotoxin and quantitated cytotoxic activity by the MTT method. Intracellular vacuolation of RGECs was observed in the presence of 36 of 57 (63%) clinically isolated H. pylori strains. However, there were no differences in the incidence of H. pylori strains with positive vacuolating cytotoxin (Tox+) among patients with gastritis, gastric ulcers or duodenal ulcers. The MTT assay showed that the cytotoxic activity of H. pylori supernatants obtained from patients with gastric ulcers was significantly higher than in patients with gastritis (p < 0.01), but was not different to duodenal ulcer patient supernatants. Similar results were also observed in Tox+ isolates, however, there were no significant differences between patients with regard to the incidence of vacuolating cytotoxin-negative isolates. Although our data may not indicate a clear correlation between prevalence of vacuolating cytotoxin and clinical manifestations, they suggest that H. pylori harboring vacuolating cytotoxin may particularly induce damage to the gastric epithelium in patients with gastric ulcers.

Gastric ulcer, atrophic gastritis, and intestinal metaplasia caused by Helicobacter pylori infection in Mongolian gerbils

BACKGROUND

Helicobacter pylori infection is associated with gastroduodenal disease in humans. In this study we aimed to show this relationship directly in Mongolian gerbils.

METHODS

The animals were challenged orally with H. pylori and killed 1, 2, 3, and 6 months after inoculation for histologic and anti-H. pylori antibody titer examination.

RESULTS

The spiral bacteria were observed in the mucus and gastric pits of all infected animals. A severe infiltration of the lamina propria by polymorphonuclear and mononuclear cells was seen 1 month after H. pylori inoculation. The submucosa was infiltrated by mainly mononuclear cells with formation of lymphoid follicles. Erosion of the gastric mucosa appeared soon after inoculation, whereas gastric ulcers, gastritis cystica profunda, and atrophy with goblet cell metaplasia occurred between 3 and 6 months after inoculation. In the duodenal mucosa a mild inflammatory cell infiltration with ballooning and diminished number of duodenal glands was seen. The IgG anti-H. pylori antibody titer increased gradually after 2 months of inoculation.

CONCLUSIONS

Since the gastritis, gastric ulcers, atrophic gastritis, and intestinal metaplasia that developed in Mongolian gerbils were similar to those observed in humans, this model may be useful to study the therapy of gastric ulcer and, with a longer observation period, to confirm a possible relationship between H. pylori and malignancy.

Long-term sequelae of experimental gastritis with Helicobacter pylori: a 5-year follow-up study

To investigate the long-term effects of Helicobacter pylori gastritis on the gastric mucosa, 13 wild Japanese monkeys (six H. pylori-infected and seven controls) were monitored for 5 years. Colonization with H. pylori, the presence of macroscopic and histological gastritis, pyloric glandular height, and epithelial cell kinetics were investigated, using Ki-67 immunostaining in the gastric mucosa. In the infected group, persistent colonization with H. pylori was demonstrated by culture and histopathologic examination. In this group, the gastritis scores were significantly higher than in controls. Simultaneously, a significant decrease in the height of antral glands and a significant increase in the length of Ki-67-positive cells between the highest and lowest cells were also demonstrated in the infected animals. These experimental results directly demonstrate the effect of H. pylori infection on the gastric mucosa and may explain the potential mechanism for its causal role in the chain of events leading to gastric carcinoma.

Sequential analyses of the mutations in the core upstream and precore regions of hepatitis B virus genome in anti-HBe positive-carriers developing acute exacerbation

The nucleotide sequences of the core upstream and precore regions (371 nucleotide length, nt. 1604-1974) of hepatitis B virus (HBV) were analysed sequentially in three subjects who were positive serologically for anti-HBe and had acute clinical exacerbation after immunosuppressive treatment. These patients were asymptomatic HBV carriers before therapy. The results revealed that the mutant with an 8-bp deletion (nt. 1768-1775) located in the basic core promoter region was dominant in the asymptomatic HBV carrier phase in two of three subjects. After exacerbation, however, such mutant clones possessing 8-bp deletion disappeared or decreased in number and were replaced by the clones possessing a precore stop codon mutation G to A (nt. 1896) or by the clones possessing additional contiguous point mutations A to T (nt. 1762) and G to A (nt. 1764) and a new point mutation C to T (nt. 1653). Possible relationships between acute exacerbation of liver function accompanied by mutation and the transition of the dominant clones were discussed.

Sequential analyses of the mutations in the core upstream and precore regions of hepatitis B virus genome in anti-HBe positive-carriers developing acute exacerbation

The nucleotide sequences of the core upstream and precore regions (371 nucleotide length, nt. 1604-1974) of hepatitis B virus (HBV) were analysed sequentially in three subjects who were positive serologically for anti-HBe and had acute clinical exacerbation after immunosuppressive treatment. These patients were asymptomatic HBV carriers before therapy. The results revealed that the mutant with an 8-bp deletion (nt. 1768-1775) located in the basic core promoter region was dominant in the asymptomatic HBV carrier phase in two of three subjects. After exacerbation, however, such mutant clones possessing 8-bp deletion disappeared or decreased in number and were replaced by the clones possessing a precore stop codon mutation G to A (nt. 1896) or by the clones possessing additional contiguous point mutations A to T (nt. 1762) and G to A (nt. 1764) and a new point mutation C to T (nt. 1653). Possible relationships between acute exacerbation of liver function accompanied by mutation and the transition of the dominant clones were discussed.

Sensitive detection of Helicobacter pylori in gastric aspirates by polymerase chain reaction

The detection of Helicobacter pylori in gastric aspirate was examined by using the polymerase chain reaction (PCR) method for amplifying a specific fragment of the urease gene A. The ability of PCR to amplify H. pylori-specific DNA was analyzed by Southern hybridization with an internal oligonucleotide probe. Twenty-two H. pylori strains from clinical isolates and reference strains were studied, and all H. pylori strains yielded a 356-bp product that hybridized with the oligonucleotide probe, whereas no amplification was evident with 18 non-H. pylori strains. This could detect as little as 50 CFU of H. pylori in pure culture and 0.1 pg of purified chromosomal DNA. A total of 50 dyspeptic patients were examined for the presence of H. pylori by culture, the rapid urease test and histological examination of antral biopsy samples as well as by PCR in gastric juice aspirate samples. The gold standard for the presence of H. pylori was established by minimum concordance of two of three tests performed on biopsy specimens. With this gold standard, 34 of the 50 patients were considered to harbor H. pylori infection. PCR correctly identified 32 (94.1%) of these 34 infected patients. PCR had the best combination of sensitivity and specificity in assessing the correct diagnosis of H. pylori as compared with those of the rapid urease test and culture. Moreover, we established a fast and simple method for use by improvement of DNA extraction. PCR of the gastric aspirate was shown to be a sensitive and specific procedure which may be an attractive alternative to methods currently used for diagnosis of H. pylori infection.

Genotyping of hepatitis C virus in the Dominican Republic

Genotyping of hepatitis C virus (HCV) of liver disease patients in the Dominican Republic was performed. Eighty-four samples positive for HCV antibody, which were confirmed by ELISA, particle agglutination, and recombinant immunoblot assay III tests, were subjected to HCV genotyping by polymerase chain reaction using type-specific primers located in the nonstructural protein 5 region. Of the 84 samples tested, 50 (59%) were found to have genotype 1a/I and this genotype was the most frequent type detected in the present study. The numbers of isolates of genotypes 1b/II, 2a/III, 2b/IV, and 3a/V were three (3.6%) six (7.1%), two (2.4%), and two 2.4%), respectively. The number of samples having mixed genotype populations was 16 (19%). The possible causes of the high prevalence of genotype 1a/I in the Dominican Republic compared with other countries and of the high detection ratio of samples having mixed genotypes are discussed.

Virulence-associated genes as markers of strain diversity in Helicobacter pylori infection

To establish a marker of strain diversity of Helicobacter pylori, a genetic examination was performed based on the detection rates by PCR of cagA and vacA, which are known to be virulence-associated genes. The test strains were obtained from 70 patients suffering from gastric ulcer (GU), 82 patients with duodenal ulcer (DU) and 48 patients with gastritis (GS). Fragments located in the three different regions of vacA were amplified; V1 being the upstream portion, V2 the mid-portion and V3 the downstream portion. For cagA, the detection rates were 70% for GU, 79% for DU and 50% for GS, showing a significantly higher rate for DU than for GS (P = 0.0005). With V1, the detection rates were 90% for GU, 90% for DU and 69% for GS, giving a significantly higher rate for GU than for GS (P = 0.0036) and also giving a significantly higher rate for DU than for GS (P = 0.0019). With V2, the detection rates were 60% for GU, 70% for DU and 44% for GS, giving a significantly higher rate for DU than for GS (P = 0.0024). The differences in vacA gene polymorphism were closely related to the evidence of gastroduodenal ulcers in H. pylori infection. Furthermore, the detection rates of cagA and polymorphisms of vacA by PCR could be used as markers of strain diversity in H. pylori-induced gastroduodenal ulcer.

Atopic dermatitis successfully treated by eradication of Helicobacter pylori

A relationship between allergic diseases and Helicobacter pylori infection has recently been noted. We report a case of atopic dermatitis and H. pylori infection in a 14-year-old girl. She had had widespread diffuse skin erythema with erosions and pigmentation since the age of 3 years. Endoscopically, there was chronic antral gastritis with H. pylori infection and histological eosinophilic infiltration. A high titer of H. pylori-specific IgG was present in serum. She was treated with a proton pump inhibitor (lansoprazole 60 mg), an antibiotic (clarithromycin 800 mg), and plaunotol (a mucosal protective agent, 480 mg) for 2 weeks to eliminate the infection. After 10 days of treatment, erythema and itching were more widespread and vesicle formation was seen on the foot. Generalized skin lesions abated a few days later. After eradication of the bacterium by the treatment, eosinophils decreased from 38.8% to 19.0%, and the clinical signs of atopic dermatitis almost disappeared. Serum gastrin level and the pepsinogen I/II ratio were normalized and histological findings of gastric mucosa showed improvement. H. pylori-specific IgE antibody, analyzed by the Western blot method, gradually decreased with the eradication treatment.

Rabies virus M protein expressed in Escherichia coli and its regulatory role in virion-associated transcriptase activity

Rabies virus M protein was expressed in Escherichia coli in the form of a fusion protein with maltose binding protein (MBP) and purified by amylose affinity column chromatography after extraction. In order to investigate the possible regulatory role of M protein in viral transcription, an assay system for rabies virion-associated transcriptase activity was established by using the ribonucleoprotein (RNP) cores prepared from purified virions. Analysis of the products of the transcription assay system showed that the products are sensitive to RNase and are positive-strand RNA. Addition of the fusion protein to the system after cleavage with a proteinase Factor Xa (FXa), which cleaves the fusion protein into the M protein and MBP, resulted in an efficient and dose-dependent inhibition of the transcription. Furthermore, addition to the system of anti-M protein monoclonal antibody significantly restored the transcription. Control experiments with the same transcription assaying system using rabies virus nucleoprotein expressed as a fusion protein with MBP and cleaved with FXa did not result in an inhibition of the transcription. These results suggest that the M protein of rabies virus has the property to down-regulate virion-associated transcription.

Rapid desensitization of serotonin 5-HT2C receptor-stimulated intracellular calcium mobilization in CHO cells transfected with cloned human 5-HT2C receptors

Serotonin 5-HT2C receptor-mediated intracellular Ca2+ mobilization was investigated in Chinese hamster ovary (CHO) cells transfected with 5-HT2C receptors. Fura-2 acetoxymethyl ester was used to investigate the regulation of 5-HT2C receptor function. CHO cells, transfected with a cDNA clone for the 5-HT2C receptor, expressed 287 fmol/mg of the receptor protein as determined by mianserin-sensitive [3H]mesulergine binding (KD = 0.49 nM). The addition of 5-HT mobilized intracellular Ca2+ in a dose-dependent fashion, ranging from a basal level of 99 +/- 1.8 up to 379 +/- 18 nM, with an EC50 value for 5-HT of 0.029 microM. Exposure to 5-HT, 1-(3-chlorophenyl)piperazine dihydrochloride (a 5-HT2C agonist), and 1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane (a 5-HT2C and 5-HT2A agonist) resulted in increased intracellular Ca2+ levels. Mianserin, mesulergine, ritanserin, and ketanserin each blocked 5-HT-mediated intracellular Ca2+ mobilization more effectively than spiperone. The receptor was rapidly desensitized by preexposure to 5-HT in a time- and concentration-dependent manner. Mezerein and phorbol 12-myristate 13-acetate, protein kinase C activators, weakly inhibited the intracellular Ca2+ mobilization induced by 10 microM 5-HT. Furthermore, the protein kinase C inhibitor H-7 partially prevented the protein kinase C activator-induced inhibition of the 5-HT-mediated increase in intracellular Ca2+ concentration. The desensitization induced by pretreatment with 5-HT was blocked by W-7, added in conjunction with 5-HT, and partially inhibited by W-5, a nonselective inhibitor of protein kinases and weak analogue of W-7.(ABSTRACT TRUNCATED AT 250 WORDS)

Mutations in the core promoter/enhancer II regions of naturally occurring hepatitis B virus variants and analysis of the effects on transcription activities

The regulatory regions for transcription and replication of several hepatitis B virus (HBV) genomes from 19 patients having various forms of HBV infection were sequenced. Predominant mutations were found to occur naturally in nucleotide positions 1762 (A to T) and 1764 (G to A) in chronic hepatitis patients and in asymptomatic carriers after seroconversion, but were not observed in HBeAg-positive healthy carriers. Since these positions were located in the basic core promoter and the overlapping enhancer II regions situated within the core upstream region, transcriptional activity was examined by chloramphenicol acetyltransferase assay to determine if there was a possible difference between the mutant and wild-type HBV. However, no significant difference was detected upon comparison of the promoter and enhancer activities between mutant and wild-type HBV.

[Summary and evaluation of genome and antibody diagnosis in hepatitis C virus infection]

Hepatitis C virus (HCV) infection can be diagnosed by antibody assay systems using recombinant antigens since the HCV genome has been identified. It is still impossible to detect viral antigens associated with HCV. Therefore, the polymerase chain reaction (PCR) has been widely used in practical laboratory examinations. Because HCV is an RNA virus and the reverse transcription process is required prior to the PCR reaction, the process of HCV RNA detection has a risk of contamination and the detection rate may differ with the PCR condition. There are several genome diagnostic methods for HCV infection; that is, genome detection by nested PCR, HCV subtyping using mixed primer, quantitation of HCV genome using competitive PCR, Quant-Amp and branched DNA probe. To clarify what factors are responsible, the efficacy of interferon therapy against chronic hepatitis C was examined. The normalization rate of serum ALT level and clearance rate of HCV RNA in serum at six months after the end of the treatment were correlated to the titer of HCV RNA genome and the HCV subtype. The patients with HCV RNA titers of less than 10(4) copies/50 microliters and with subtype group III showed a high response to interferon administration. On the other hand, the results of quantitation of the HCV core antibody titer were closely associated with the presence of HCV RNA using core protein with the recombinant vaccinia expression system or recombinant E. coli system (JCC-2). Especially, in the group of high responders to interferon treatment, the antibody titer against core protein was apparently decreased after the end of interferon therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Target cells of cytotoxic T lymphocytes directed to the individual structural proteins of rabies virus

Target cells of cytotoxic T lymphocytes (CTL) directed to the individual structural proteins (except for the large polymerase (L) protein) of rabies virus were established by expressing only the respective protein in murine neuroblastoma (NA) and murine macrophage (J774-1) cell lines. Mice infected with the ERA strain of rabies virus developed CTL responses to all of these rabies virus proteins. The cytotoxic activity was abrogated by pretreatment of the effector cells with anti-CD8 monoclonal antibody (MAb) and complement but not with anti-CD4 MAb. Cell lysis by CTL was blocked in the presence of anti-major histocompatibility complex (MHC) class 1 antibodies in J774-1 cell lines. Rabies virus-infected cells express these proteins at the surface, which can be recognized and lysed by the respective CTL. Mice immunized with beta-propiolactone-inactivated virus induced a CTL response against glycoprotein but not against internal viral components. This assay system might be useful for further analysis of the possible contribution of these proteins in the cell-mediated immune protection against rabies.

Analysis of upstream region of hepatitis B virus core gene using in vitro transcription system

Transcription of the core (C) gene of hepatitis B virus DNA (HBV-DNA) was studied by an in vitro transcription system using nuclear extracts of human liver cell (HepG2) and non-liver cell (HeLa) origins. RNA polymerase II-dependent run-off transcription of 3.5-kb (C) mRNA was observed in both nuclear extracts; but the efficiency was much higher in the HepG2 nuclear extract. Analysis of run-off transcripts using upstream deletion mutants of HBV-DNA demonstrated that there are two transcription start sites located at approximately nucleotide numbers (nt) 1,797 +/- 5 and 1,815 +/- 5. This analysis also suggested that the minimum core promoter sequence and a cis-acting and liver-specific element for C mRNA transcription are located in the downstream region from -80 and -110 (HincII site) of transcription start sites, respectively. DNA-binding protein assays using synthetic double-stranded oligonucleotide probes corresponding to three regions in the upstream region (nt from 1,401 to 1,760) of transcription start sites revealed that there are some liver cell-specific and non-specific DNA-binding proteins in both nuclear extracts. The amount of those proteins was generally higher in the HepG2 nuclear extract. However, no obvious correlation was observed in the present study between the presence of DNA-binding proteins and transcription activity of nuclear extracts in our system. The possible causes of this discrepancy are discussed.

Protective efficacy in mice of post-exposure vaccination with vaccinia virus recombinant expressing either rabies virus glycoprotein or nucleoprotein

Mice vaccinated intraperitoneally (i.p.) with 10(7) p.f.u. of a vaccinia virus recombinant expressing either the glycoprotein (rVac-G) or nucleoprotein (rVac-N) of rabies virus 3 weeks before challenge were protected against peripheral lethal infection. Similarly, by post-exposure vaccination in which mice were first infected with rabies virus and subsequently vaccinated i.p. with the recombinant, rVac-G conferred protection when given immediately following infection and up to 24 h after infection. Prior treatment of those mice with anti-CD8 monoclonal antibodies (MAb) did not significantly affect the outcome of the infection. In contrast, rVac-N failed to confer protection even with higher doses (10(8) p.f.u.) of the virus or even when administered by the intradermal route. Anti-nucleoprotein antibody production by these mice was not suppressed by prior rabies virus infection and the levels and the time of antibody production were similar to those of anti-glycoprotein antibody production in mice vaccinated with rVac-G after rabies virus infection. The cytotoxic T lymphocyte response was also not down-regulated by rabies virus in the mice that were given rVac-N. Possible mechanism(s) for the ineffectiveness of rVac-N by post-exposure vaccination in contrast to pre-exposure vaccination was discussed.

Correlation of serum antibody titers against hepatitis C virus core protein with clinical features by western blot (immunoblot) analysis using a recombinant vaccinia virus expression system

In order to study the relationships among the clinical features of hepatitis C patients, the presence of hepatitis C virus (HCV) RNA in their blood, and their serum antibody titers against the core protein of virus and to study the antibody levels in asymptomatic HCV carriers, a recombinant vaccinia virus containing a core protein gene was constructed. The recombinant virus expressed a protein with a molecular mass of 22 kDa in RK-13 cells as determined by Western blot (immunoblot) analysis. By using the cell lysate of virus-infected cells and serially diluted serum samples, core antibody titers in the groups of patients in the chronic hepatitis phase and in the convalescent phase as well as in asymptomatic carriers were determined by enhanced chemiluminescence Western blot analysis. Almost all patients in the chronic phase were shown to have high antibody titers of more than 1:500,000 and with no exception had of HCV RNA in their sera. On the other hand, patients who had recovered naturally and were in the convalescent phase were shown to have significantly lower antibody titers, and the antibody was not detected in the lowest serum dilution of 1:500 in 43% of these patients (three of seven total patients). Antibody levels of patients who showed a good response to interferon treatment decreased to intermediate levels between those of patients in the chronic phase and those of patients in convalescent phase. The antibody titers in asymptomatic carriers varied considerably from 1:500,000 to 1:500, and 41% (11 of 27 total individuals) of these carriers showed a high titer equivalent to that of those in the chronic phase. Core antibody was detected consistently in the individuals in whom HCV RNA was detected. This system for core antibody might be useful for identifying the stage of an apparent HCV infection.

Resistance of mice vaccinated with rabies virus internal structural proteins to lethal infection

Mice were vaccinated with recombinant vaccinia virus (rVac) expressing the glycoprotein (G), nucleoprotein (N), phosphoprotein (NS) or matrix protein (M) of rabies virus and their resistance to peripheral lethal infection with street rabies virus was examined. Mice vaccinated with rVac-G or rVac-N developed strong antibody responses to the corresponding proteins and essentially all mice survived challenge infection. Mice vaccinated with rVac-NS or rVac-M developed only a slight antibody response, however, a significant protection (59%) was observed in the rVac-NS-vaccinated mice, whereas rVac-M-vaccinated mice were not protected. No anti-G antibodies were detected in the sera of mice which has been vaccinated with rVac-N or rVac-NS and survived challenge infection. Passive transfer of anti-N monoclonal antibodies (MAbs) recognizing an epitope located on amino acids 1-224 of the protein prior to challenge resulted in significant protection, although the protection was not complete even with a high amount of antibodies. In contrast, none of the mice given MAbs recognizing an epitope of amino acids 247-415 or F(ab')2 fragments from a protective MAb IgG were protected. Administration of anti-CD 8 MAb to rVac-N-vaccinated mice showed no significant effect on protection. Our observations suggest that a considerable part of the protection achieved by the vaccination with rVac-N can be ascribed to the intact anti-N antibodies recognizing an epitope located on amino acids 1-224 of the protein.

Comparative sequence analysis of the M gene among rabies virus strains and its expression by recombinant vaccinia virus

Nucleotide sequences and the deduced amino acid sequences of the gene encoding the matrix (M) protein of the Nishigahara and the CVS strains of rabies virus have been determined. The M gene is 609 nucleotides long and is capable of coding for a peptide composed of 202 amino acids. Sequence comparison of these M genes with those of other stains [Pasteur (PV), ERA, Avol] revealed that there is 89.7-91.5% homology at the nucleotide level, and 90.1-92.1% homology at amino acid level, between almost all combinations of these strains. However, in the combinations of the PV and ERA strains, and the virulent CVS and the avirulent CVS-derived Avol strains, much higher homology was observed both at the nucleotide and amino acid levels. The predicted secondary structure and hydropathy profiles also exhibited similar features. Recombinant vaccinia virus containing the M gene was constructed. Sodium dodecyl sulfate (NaDodSO4)-polyacrylamide gel electrophoresis of the precipitates obtained by immune reaction of the recombinant virus-infected cell lysate with a monoclonal antibody against the M protein revealed that electrophoretic mobility of the expressed protein is indistinguishable from that of the authentic M protein from rabies virions.

Suppression of cell-mediated immunity by street rabies virus infection

An attempt to define a severe suppression of cell-mediated immunity by street rabies virus infection was undertaken by using the mice lethally and peripherally infected with a street rabies virus (1088 strain). The cell-mediated cytotoxic (CMC) activity of the spleen cells from those mice once slightly increased until day 4 after infection but declined rapidly thereafter until their death on days 10 to 12 after infection. In parallel with a decrease of CMC response of the spleen cells from 1088-infected mice, proliferative response to Con A, IL-2 activity in the culture supernatants of Con A-induced proliferation, responsiveness to exogenously added IL-2 and to Con A to express IL-2R, of those cells became suppressed, and the marked decrease of the total number of spleen cells was observed. Selective depletion of CD4+ and CD8+ cells in the spleens, abnormalities of IL-1 and E-type prostaglandins (PGE2) production or production of inhibitory component able to block IL-2 activity by spleen cells were not observed and these factors did not appear to be associated with the suppression of proliferative response to Con A. However, an apparent association of CD8+ cells in the suppression of differentiation of pre-cytotoxic lymphocytes (CTL) into CTL was demonstrated in the co-culture experiments of the spleen cells from 1088-infected mice with spleen cells of mice infected with an attenuated rabies virus (ERA strain) which can induce higher levels of CMC response. There was no evidence of the productive replication of rabies virus in thymus and spleen of 1088-infected mice. The relationship of these observations to current theories on virus-induced immunosuppression was discussed.

Mapping of the antigenic determinants recognized by monoclonal antibodies against the M2 protein of rabies virus

Twenty-one hybridomas producing monoclonal antibodies (moAbs) against the M2 protein of the Nishigahara (RECH) strain of rabies virus were prepared using the SDS-polyacrylamide gel-purified M2 protein as the immunogen. All moAbs reacted with the protein after Western blotting of rabies virus. By combinations of competitive binding assays, examination of the reactivity of moAbs to the cells infected with parent RCEH and two other strains, CVS and HEP-Flury, and immunoprecipitation with in vitro translation products derived from full-length and truncated cDNAs of the M2 gene, these moAbs could be classified into seven epitope groups. Of these, 20 moAbs belonging to six epitope groups were suggested to recognize an antigenic determinant in the amino-terminal region, from the 1st to the 72nd amino acid of the protein (8 moAbs from two groups directed to amino acids 1 to 72; 2 moAbs from a group directed to amino acids 9 to 72; 5 moAbs from a group directed to amino acids 17-72; 5 moAbs from two groups directed to amino acids 32 to 72). The antigenic determinant recognized by the remaining 1 moAb was shown to be located in the amino acid region from 50 to 171. These moAbs should be useful for further studies on the biological functions of the M2 protein of rabies virus.