A small number of “seminal super-shedders” who have disproportionately high HIV viral loads in their semen may be particularly likely to transmit HIV during unprotected sex, according to research presented to the 2003 conference of the British HIV Association last week in Manchester.
Seminal and plasma viral loads were obtained from 72 HIV-posiitve men who were not taking HIV therapy in a research project involving investigators from London and Birmingham. Earlier research from these investigators established that in men taking HAART, a detectable seminal viral load was associated with untreated gonorrhoea (see link below).
Information on age, stage of HIV disease, CD4 cell count, blood plasma viral load, and the presence of a sexually transmitted infection (STI) such as gonorrhoea, NSU or chlamydia was collected to see if there were any risk factors for higher viral loads in semen. The overwhelming majority of men (n=65) were gay, average age was 35 years, and median CD4 cell count was 214 cells/mm3. An AIDS diagnosis had been recorded for 31 of the men.
Although none of the men in the study had a blood plasma viral load below the limit of detection (400 copies/ml), 22 men (30% of the sample) did have undetectable seminal viral loads. These men were classified as “non-shedders. ” Low levels of HIV, on average 4,000 copies/ml, were detected in the semen of 58% of men, who were classified as “seminal shedders. ” Their blood plasma viral load was significantly higher than non-shedders at 100,000 copies/ml versus 10,000 copies/ml.
12% (n=9) of men had extremely high seminal levels of HIV, on average 398,000 copies/ml, and these nine men were classified as “seminal super- shedders” and were considered particularly likely to pass on HIV during unprotected sex.
Blood plasma viral loads, CD4 cell counts and stage of HIV disease did not differ significantly between super-shedders and seminal shedders. However, the investigators did find that super-shedders were generally older, with an average age of 48 years compared to 35 for the sample as a whole, and were more likely to have an STI (33% of super-shedders compared to 3% of total sample).
The investigators conclude that men shedding viral load in their semen were likely to have higher blood plasma viral loads than non-shedders. In addition, a small number of men are super-shedders, and although they have comparable blood levels of HIV to normal shedders, super-shedders tend to be older and have an STI which may assist local reproduction of HIV in the genital tract.
Further information on this website.
Sexual health resources - menu
Gonorrhoea is the STI most likely to cause semen viral load rebound in HAART patients - news story
Taylor S et al. Seminal super-shedding of HIV: implications for sexual transmission. 9th Conference of the British HIV Association Annual, oral presentation 02, 2003.