25. Transmission and progression of HIV/AIDS:

Two recent articles in the Lancet provide some insights into the transmission and progression of retroviral disease. The first relates to a follow-up study in Zambia that originally included >1300 cohabiting HIV-sero-discordant couples (i.e. one HIV+, the other HIV-). Those who became sero-concordant were studied, and it was found that common alleles at HLA class I B loci predisposed to transmission of disease. The analysis was based on 125 couples who had intra-partner transmission, and 104 who remained sero-discordant. Transmission was independent of age, which partner started out as positive, presence of other STDs, frequency of sexual encounters or viral load. Overall, sharing of HLA-B alleles was associated with accelerated intra-couple transmission by a factor of 2,23 (95% CI 1.52 - 3.26; p<0.0001). Where couples shared both B alleles the mean time to sero-concordance was 185 days, with sharing of one it was 395 days, and if neither was shared the time to transmission was 638 days (i.e. it was still possible to transmit but at a much lower rate). Similar results have been found with vertical transmission i.e. class I HLA-sharing increases perinatal transmission rates.
The second study used PCR to identify HIV positive patients with CMV disease, and showed that the presence of the latter virus was associated with a two-fold increase in risk of progression to a new AIDS-defining disorder and fourfold increase in risk of death. These findings were independent of the fact that patients had access to HAART and had shown a response to the regimen. Herpes viruses in general and CMV in particular have long been regarded as candidates for activation of latent HIV disease and contribution to immunosuppression.

Read more:
Lancet 2004;363:2101-2; and 2137-9
Lancet 2004;363:2103-4; and 2116-21
J Infect Dis 1998;177:551-6
J Infect Dis 2000;181:1581-9
J Acquir Immune Defic Syndr 2001;27:277-80