Hepatitis B virus infection in the South Pacific : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science at Massey University
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Date
1999
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Massey University
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Abstract
An exploratory study into the genetics of the hepatitis B virus and its human host in the South Pacific was undertaken to determine direction for future research. This virus is a serious health concern, especially for the indigenous people of this region. The DNA sequence of 14 complete and 2 partial virus genomes were obtained. The viral sequence mutations were investigated and compared with a collected database and current literature. Phylogenetic analysis of the viral sequences was carried out using version 4.64 of PAUP* and SplitsTree. Using the new sensitive method of sequence based typing, HLA-DPA1 allele's were typed in 51 unrelated Trobriand Islanders. The viral genomes displayed a great deal of variation with many interesting mutations. The results highlight the affect of quasi-species distribution within a host. Phylogenetic analysis identified two hepatitis B genotypes within the South Pacific, HBV-C and HBV-D. However, the genotype common in northern Europe (HBV-A) was not found. The phylogenetic analysis presented a pattern of evolution that resembled that of its human host. The Trobriand Islanders were found to be an extremely homogeneous population, with 86% homogenous for the HLA- DPA1*02022 allele. The study proved to be very informative, providing the directions of research we aimed for. The Hepatitis B samples demonstrated an interesting pattern of evolution that parallels that of its host supporting a co-evolutionary relationship between host and pathogen, thus hepatitis B appears to be indigenous in the South Pacific. We are presently establishing research to further investigate this pattern by analysing viral samples from Fiji. We have also established research that will investigate the rate of evolution of this virus. The sequenced based typing method proved to be very informative with the ability to detect new alleles. The allele frequency obtained from the Trobriand Islanders agreed with concurrent research and supports the fast-train model of migration into the Pacific. Further work in Fiji will continue with this theme of research as genetic analysis of Fiji has proved to be more complex.
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Hepatitis B, Papua New Guinea, Trobiand Islands