An epidemiological study of influenza viruses among Chinese farm families with household ducks and pigs.

To examine the possibility of interspecies transmission and genetic reassortment of influenza viruses on farms in Southern China, we surveyed 20 farm families living outside the city of Nanchang who raised pigs and ducks in their homes. Weekly interviews of family members and virus isolation studies of throat swabs and faecal samples, collected from September 1992 to September 1993, established the seasonal pattern of respiratory tract infections in these families and identified 11 influenza viruses (6 in humans and 5 in ducks). Most of the human isolates were type A of H3N2 subtype. Serologic studies of farm pigs indicated infection by the same human viruses circulating in family members, but there was no evidence that either swine or avian viruses had been transmitted to pigs. Eight of 156 human serum samples inhibited the neuraminidase activity of two of the duck isolates, raising the possibility of interspecies transmission of these avian viruses. Genotype analysis of duck and human isolates provided no evidence for reassortment. Our finding support the concept that intermingling of humans, pigs and ducks on Chinese farms is favourable to the generation of new, potentially hazardous strains of influenza virus.

Separation of resistance to antitumor diarylsulfonylurea agents from collateral sensitivity to mitochondrial toxins.

Compared with parental GC3/c1 human colon adenocarcinoma cells, which are diarylsulfonylurea (DSU)-sensitive cells, the DSU-resistant clone LYC5 demonstrates 4.2-, 12.8-, and 5.3- fold increase in sensitivity to the mitochondrial toxins rotenone, antimycin, and oligomycin, respectively. Studies with hybrids formed by fusion of parental GC3/c1 cells with LYC5 cells have indicated that resistance to antitumor DSUs and collateral sensitivity to mitochondrial toxins are recessive and therefore potentially linked. To examine this, we transfected a cDNA library from GC3/c1 cells, constructed in pcDNA3, into LYC5 cells. G418-resistant colonies were selected and further selected in a single step for resistance to rotenone (100 nm). Individual colonies (designated T5LR) were expanded and tested for sensitivity to mitochondrial toxins, antitumor DSU agents (LY195779 and LY186391) that demonstrate a 45-50-fold differential potency against GC3/c1, LYC5 cells, and the antimitotic agent vincristine. Results demonstrate that resistance to mitochondrial toxins rotenone, antimycin, and oligomycin can be transferred without conferring a DSU-sensitive phenotype. Furthermore, in T5LR clones, resistance to mitochondrial toxins was not associated with increased resistance to vincristine or increased P-glycoprotein expression, supporting the contention that resistance to these agents is independent of P-glycoprotein. Southern blot analysis of T5LR clones demonstrated unique integration sites for the neomycin phosphotransferase gene into genomic DNA in clones 4 and 9, indicating independent derivation. Analysis of clones 4, 6, and 9 with use of polymerase chain reaction demonstrated a cDNA insert of approximately 1.0 kilobase.

Evidence for interspecies transmission and reassortment of influenza A viruses in pigs in southern China.

The Asian/57, Hong Kong/68, and Russian/77 pandemics of this century appeared or reappeared in China. Interspecies transmission and genetic reassortment of influenza viruses have been implicated in the origin of these human pandemic influenza viruses. Pigs have been suspected to be the "mixing vessel" where reassortment occurs. To investigate this possibility, 104 porcine influenza viruses collected at random from Southern China from 1976 to 1982, including 32 H3N2 isolates and 72 H1N1 isolates, were studied using dot blot hybridization, partial sequencing, and phylogenetic analysis. There were 29 of 32 H3N2 isolates characteristic of viruses originally derived from humans; the other 3 isolates were reassortants containing genes from porcine and human influenza viruses. Phylogenetic analyses of the polymerase B1 (PB1) genes showed that interspecies transmission from humans to pigs has happened multiple times in pigs in Southern China. All 72 H1N1 isolates were of porcine origin characteristic of classical porcine H1N1 influenza virus. Analysis of 624 genes of porcine influenza viruses from Southern China failed to detect any evidence for avian influenza virus genes. This contrasts to what is currently found in Europe, where the majority of porcine influenza virus isolates are of avian origin.

Analysis of the influenza virus gene pool of avian species from southern China.

Although Southern China has been considered the epicenter of human influenza pandemics, little is known about the genetic composition of influenza viruses in lower mammals or birds in that region. To provide information on the molecular epidemiology of these viruses, we used dot blot hybridization and phylogenetic methods to study the internal genes (PB1, PB2, PA, NP, M, and NS) of 106 avian influenza A viruses isolated from a total of 11,798 domestic ducks, chickens, and geese raised in Southern China including Hong Kong. All 636 genes examined were characteristic of avian influenza viruses; no human or swine influenza genes were detected. Thus, influenza virus reassortants do not appear to be maintained in the domesticated birds of Southeast Asia, eliminating opportunities for further gene reassortment. Phylogenetic analysis showed that the internal genes of these viruses belong to the Eurasian avian lineage, supporting geographical separation of the major avian lineages. The PB1 genes were most similar to A/Singapore/57 (H2N2) and Hong Kong (H3N2) viral genes, supporting an avian origin for the recent human H2N2 and H3N2 pandemic strains. The majority of internal genes from avian influenza viruses in Southern China belong to the Eurasian lineage and are similar to viruses that have recently been transmitted to humans, swine, and horses. This study provides evidence that the transmission of avian influenza viruses and their genes to other species is unidirectional and that the transmission of mammalian influenza virus strains to domestic poultry is probably not a factor in the generation of new pandemic strains.

Analysis of the evolution and variation of the human influenza A virus nucleoprotein gene from 1933 to 1990.

This study examined the evolution and variation of the human influenza virus nucleoprotein gene from the earliest isolates to the present. Phylogenetic reconstruction of the most parsimonious evolutionary path connecting 49 nucleoprotein sequences yielded a single lineage. The average calculated rate of mutation was 3.6 nucleotide substitutions per year (2.3 x 10(-3) substitutions per site per year). Thirty-two percent of these mutations resulted in amino acid substitutions, and the remainder were silent mutations. Analysis of virus isolates from China and elsewhere showed no significant differences in their rate of evolution, genetic diversity, or mean survival time. The nearly constant rate of change was maintained through the two antigenic shifts, and there were no obvious changes in the number or types of mutations associated with the changes in the surface proteins. A detailed comparison of the changes that have occurred on the main evolutionary path with those that have occurred on the side branches of the phylogenetic tree was made. This showed that while 35% of the mutations on the side branches resulted in amino acid changes, only 21% of those on the main path affected the protein sequence. These results suggest that although the rate of change of the human influenza virus nucleoprotein is much higher than that previously described for avian influenza viruses, there are measurable constraints on the evolution of the surviving virus lineage. Comparison of the nucleoproteins of virus isolates adapted to chicken embryos with the nucleoproteins of those grown only in MDCK cells revealed no consistent differences between the virus pairs. Thus, although the nucleoprotein is known to be critical for host specificity, its adaptation to growth in eggs apparently involves no immediate selective pressures, such as are found with hemagglutinin.

Molecular cloning of a new variant of human papillomavirus type 6 isolated from a Chinese woman and expression of its L1 gene in E. coli--molecular cloning & expression of HPV6 gene.

A human papillomavirus genome DNA of 7.9 kb from a Chinese woman with genital condyloma acuminata was cloned in BamHI site of pAT153. According to the results obtained from Southern blotting, restriction mapping as well as partial DNA sequencing, the isolated genome (HPV6BV) had obvious variance and was referred to as a new variant of HPV6 found in China the first time. HPV6BV L1 gene was successfully expressed in E. coli as a fusion protein with pUR288. The beta-galactosidase/L1 fusion protein reacted with both beta-galactosidase antiserum and HPV antibody using Western blot technique. The E. coli-produced fusion protein, possessing HPV antigenicity, may provide a reagent for clinical diagnosis and epidemiological survey.

Diagnosis of human papillomavirus infection in uterine cervix by immunoperoxidase technique.

The present study detected human papillomavirus (HPV) genus-specific antigen in paraffin section of chronic cervicitis tissue by peroxidase-antiperoxidase (PAP) technique. The results showed that HPV antigen was detected in 34 of 101 specimens (33.66%). All the normal control sections were negative. The antigen positive nuclei were found in the koilocytes of the upper layers of the epithelium. Antigen positive cells may display a uniform or a scattered pattern. The pathologic feature of HPV infection discribed by Meisels et al. was found in all positive sections. It is suggested from the results that almost one third of chronic cervicitis is induced by HPV infection.

[Human papillomavirus infection and carcinogenesis of cancer of uterine cervix. II. Immunoperoxidase localization of papilloma-virus antigen in tissues of the uterine cervix].

244 cervical tissue specimens with different diagnoses were stained by peroxidase-anti-peroxidase technique (PAP) for assay of the human papillomavirus (HPV) genus-specific antigen, the first of its kind performed in China. HPV antigen was detected in 41.93% of simple condyloma group, in 35.29% of dysplasia with condyloma and in 27.27% of carcinoma with condyloma. There was no positive in the control, dysplasia or carcinoma groups. The antigen positive nuclei were found in the koilocytes or parakeratosis cells in the upper layers of the epithelium. The severer the condyloma, the higher the positive rate of antigen. In the severe condyloma group, the positive rate was as high as 64.71%. The koilocytes were observed in every HPV antigen positive section. In view of the coexistence and continuous transformation of condyloma, dysplasia and carcinoma in pathomorphology, these results provide an important evidence to the further studies on the relation between HPV infection and carcinogenesis of cancer of uterine cervix.

[Human papillomavirus infection and carcinogenesis of cancer of the uterine cervix. I. Pathomorphology of 357 cervical tissues].

Human papillomavirus (HPV) infection in the cervix was studied by pathomorphology for the first time in China according to Meisels and Fortin's criteria. Cervical condyloma was found in 257 out of 357 (71.99%) cervical tissues. 141 were simple condyloma, 50 dysplasia with condyloma and 66 carcinoma with condyloma. A zone of continuous transformation was observed between the condyloma and dysplasia or carcinoma. 141 simple condylomas were initially diagnosed as chronic cervicitis in 94 (66.67%) and as dysplasia in 29 (20.57%). The pathomorphologic features of condyloma have not been fully recognized before. In carcinogenesis of the cervical carcinoma, the fact that condyloma associated becomes severer in extent but less in incidence, conforms well to Meisels' view that condyloma is the precursor of carcinoma in situ. It is suggested that HPV infection is closely related to cervical carcinoma.