Takayuki Morishita

Hepatitis A, B and C seroprevalence in Pakistan

A cross sectional study was conducted to determine the seroprevalence of Hepatitis A, B, and C virus in healthy Pakistani children. HAV IgG antibody was assayed in 258 subjects and it was found that 94% children by 5 years of age had HAV IgG-antibody. The overall seroprevalence of HAV IgG antibody was 55.8% and IgM 5.3%. HBVsAb levels assayed in 236 healthy children showed a seroprevalence of 2.97%. Similarly, HCV antibody seroprevalence was found to be a low 0.44% in healthy children. HAV is a major cause of Hepatitis, as compared to HBV and HCV which are of low endemicity.

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. J. Med. Virol. 54:243–248, 1998.

Properties of hepatitis B virus genome recovered from Vietnamese patients with fulminant hepatitis in comparison with those of acute hepatitis.

Among the many mutations found in the hepatitis B virus (HBV) genome, some have been associated with fulminant hepatitis, as exemplified by precore‐defective mutations. The aim of this study was to determine whether such mutations also are found in Vietnamese cases of fulminant hepatitis B. The full‐genome nucleotide sequence of HBV in three patients with fulminant hepatitis (F‐2, F‐3, and F‐6) and one with acute hepatitis (A‐3), who were admitted to Cho Ray Hospital, Ho Chi Minh City, Vietnam was ascertained. Additionally, two patients with fulminant hepatitis (F‐1 and F‐7) and three with acute hepatitis (A‐1, A‐2, and A‐5) were examined only for the precore/core region of HBV. Remarkably, the nonsense mutation at precore codon 28 (Trp82Stop) was found in four of the five patients with fulminant hepatitis, while all the acute hepatitis patients harbored wild type (one had a mixture of wild and mutant types). The missense mutations within the core region, Ile97Leu and Pro130Ile/Thr/Ser, were also remarkable in fulminant hepatitis. Only F‐2 was free from these precore/core mutations, but F‐2 was unique in that it possessed a chimeric genotype: it could be classified into genotype C as a whole, but its X region was of genotype B, like the other four fulminant hepatitis isolates (F‐1, F‐3, F‐6, and F‐7). The codon 41 of the X protein was Pro in all three fulminant hepatitis cases examined for this region, while it was Ser in the wild‐type isolates of genotype B. Of note as negative data, the mutations C1653T and T1753M of the enhancer II (Enh II) and A1762T and G1764A of the precore/core promoter regions, once reported to be relevant to severe or fulminant hepatitis, were not found in the present cases. The results with the Vietnamese cases of fulminant hepatitis corroborated results of previous studies with respect to the mutations Trp28Stop of precore and Ile97Leu and Pro130Ile/Thr/Ser of core, but not for the mutations within Enh II and precore/core promoter region. Whether the Ser41Pro mutation in the X region of genotype B HBV is Vietnam‐specific or disease‐specific deserves further investigation. J. Med. Virol. 61:23–28, 2000.

Studies on the molecular basis for loss of the ability of recent influenza A (H1N1) virus strains to agglutinate chicken erythrocytes.

Recent strains of influenza A but not B viruses have lost the ability to agglutinate chicken red blood cells (CRBC). The H1N1 viruses isolated in Japan during the 1991/92 season could be divided into two groups. Group 1 viruses (A/Aichi/4/92 and A/Aichi/7/92) agglutinated goose red blood cells (GRBC) and CRBC, while group 2 viruses (A/Aichi/24/92 and A/Aichi/26/92) did not agglutinate CRBC. There were no amino acid differences between them in the haemagglutinin (HA) polypeptide. Reassortment experiments between a group 1 virus (A/Aichi/4/92) or a group 2 virus (A/Aichi/24/92) and the A/WSN/33 influenza A (H1N1) virus strain suggested that the HA gene products of the viruses of both groups had lost the capacity to agglutinate CRBC. The HA proteins expressed on Cos cells by transfecting the cDNAs of the virus HA gene of A/Aichi/4/92 and A/Aichi/24/92 agglutinated GRBC but not CRBC. These experiments indicated that the HA proteins of H1N1 viruses of both groups isolated in 1992 had lost the ability to agglutinate CRBC even though the group 1 virions showed haemagglutinating capacity with CRBC. By using the cDNAs of the HA gene of seven natural isolates obtained from 1977 to 1992, it was found that the expressed HA proteins of influenza A (H1N1) viruses isolated since 1988 had lost the ability to agglutinate CRBC. Experiments with chimeric and point-mutated HA cDNAs of A/Aichi/24/92 showed that an amino acid change at residue 225, which occurred after 1986, and a cluster of amino acid changes at residues 193, 196 and 197, which occurred before 1986, were responsible for loss of the ability to agglutinate CRBC. Egg-adapted virus derived from A/Aichi/24/92 had one amino acid change at residue 225 compared to the parental virus.

Host-Specific Hemagglutination of Influenza A (H1N1) Virus

H1N1 strains of influenza A virus isolated during the influenza season of 1991–92 were divided into two groups according to the property of host‐specific hemagglutination. Group 1 viruses agglutinated human and chicken red blood cells. Group 2 viruses agglutinated human but not chicken red blood cells. The viruses of both groups, however, showed the same antigenic structure determined with ferret antisera. The virus clones which were plaque‐purified twice from a group 2 virus retained the characteristic of host‐specific hemagglutination after five successive passages in MDCK cells, indicating that this phenomenon is genetically determined. However, the amino acid, sequences of the hemagglutinin (HA) polypeptides deduced from the nucleotide sequences of the HA gene of the two groups did not show any differences between them. This suggests a difference in amino acids in some other polypeptide(s), which affects the host‐specific hemagglutination.

Prevalence of infection and genotypes of GBV-C/HGV among homosexual men

Since the discovery of GB virus‐C (GBV‐C) and hepatitis G virus (HGV), many studies have been performed. These viruses are now known to be parenterally, as well as sexually transmitted. A phylogenetic analysis also revealed that GBV‐C has five major genotypes: type 1 predominates in West Africa, type 2 in Europe and the United States, type 3 in parts of Asia, type 4 in Southeast Asia, and type 5 in South Africa. Despite the number of reports so far, there have been few large‐scale surveys of homosexual men to determine the prevalence of the GBV‐C/HGV infections. We examined the levels of GBV‐C/HGV viremia in 297 homosexual men who attended the Nagoya Lesbian and Gay Revolution held in Nagoya, Japan. Reverse transcription‐polymerase chain reaction (RT‐PCR)/nested PCR of the GBV‐C/HGV 5′‐non‐coding region (NCR), and base sequence analyses showed that the infection rate was 12.5%, and genotypes in this population were classified into type 2 (32%) and type 3 (68%). None were classified as types 1, 4, or 5 in this study. Our results indicate that the GBV‐C/HGV type 2 seen mainly in Europe and the US is spreading widely in Japan, especially in the Nagoya district.

Quantitative SNP-detection method for estimating HIV-1 replicative fitness: application to protease inhibitor-resistant viruses.

We have improved the methods for the standard competitive growth assay of human immunodeficiency virus type 1 (HIV‐1). The cloning step for the mixed viral population and subsequent genotype analysis for arbitrary numbers of clones were excluded from procedures. Instead, a single nucleotide polymorphism (SNP)‐detection step was devised for the determination of viral populations. The quantitative SNP‐detection method can rapidly estimate the proportion of wild‐type and mutant populations with high reproducibility. Consequently, this method allows manipulation of many samples within a short period. Using this new competitive growth assay, replicative fitness of drug‐resistant HIV‐1 containing an M46I amino acid mutation in the protease was assessed in the presence or absence of indinavir. Without indinavir, replicative fitness of wild‐type HIV‐1 surpassed that of M46I‐mutated HIV‐1, and the fraction of mutated virus was reduced to about 10% at passage #9. In contrast, the fraction of M46I‐mutated virus increased to >90% at passage #5 in the presence of 26.4 nM indinavir. Almost identical results were obtained for L90M‐mutated HIV‐1 with or without saquinavir. HIV‐1 can survive under indinavir pressure by acquiring M46I mutation, as with acquisition of the L90M mutation under saquinavir pressure. However, these mutations damage viral replicative fitness under natural conditions without any drugs. Subtle differences between wild‐type and mutant viruses are thus easily detected using the improved method.

Isolation of an Influenza C Virus Introduced into Japan by a Traveler from Malaysia

ABSTRACT An influenza C virus was isolated from a Japanese traveler who had visited Malaysia in April 1999. Phylogenetic analysis indicated that the genome composition of this virus was distinct from that of any other strain isolated in Japan. The possibility that a genetically unique influenza C virus was introduced into Japan by a traveler is shown.