HIV病毒文档ppt

HIV-1 Genotypes
M (main); O (outlier); and N (non-wenku.baidu.com, non-O) The M group of HIV-1, which includes more than
95% of the global virus isolates, consists of at least nine discrete clades or subgroups (A, B, C, D, F, G, H, J, and K) and 15 circulating recombinant forms (CRF) HIV-1 group O isolates have been recovered from individuals living in Cameroon, Gabon, and Equatorial Guinea; their genomes share approximately 65% identity with group M viruses Early in the epidemic, group O strains may have been responsible for more than 20% of HIV-1 infections in Cameroon but currently are associated with approximately only 1%
This approach has been validated by successfully timing the earliest historic isolate, which was sequenced from a stored plasma sample obtained in 1959 from a person who died in Manchester, England
CRF01, a clade A/clade E recombinant originally isolated in Thailand
HIV-1 Genotypes
Type B found in western countries, may be transmitted more effectively by homosexual intercourse and via blood (as in intra-venous drug use) whereas types C and E may be transmitted more via a heterosexual route
Types C and E replicate better in Langerhans' cells found in the mucosa of the cervix, vagina and penis while type B replicates better in the rectal mucosa. It also appears that type E is more readily transmitted between sexual partners than type B
HIV-1 Genotypes
Clade A viruses, the most common HIV-1 subtype in Africa early in the epidemic, currently account for more than a quarter of the infections globally, and are present predominantly in eastern and central African countries
China also has a severe problem with up to 1.5 million HIV-infected people in 2004 (prevalence rate: 0.1%). It is predicted that if nothing is done to prevent the increasing infection rate, China will have 10
million cases by 2010.
Origin of HIV
The global HIV epidemic is the result of a crossspecies infection of humans by a chimpanzee lentivirus, simian immunodeficiency virus (SIVcpz), which occurred in west central Africa
Clade B viruses, the most intensively studied HIV1 subtype, remain the most prevalent isolates in Europe and North America
Clade C viruses have become the dominant subtype and now account for nearly half of HIV-1 infections worldwide
SIVcpz is an asymptomatic infection in chimpanzees
Date of introduction of the M group into the human population is estimated to be around 1931, based on analysis of large numbers of sequenced HIV isolates, assuming a constant rate of evolution