Background: HIV-1 is usually detected in seminal plasma (SP) less frequently than the corresponding blood plasma (BP) and usually at lower levels. However, in most cohorts there are a significant minority of men in which SP levels are equal to, or higher than BP levels. We have identified these individuals as “seminal super shedders” (SSS) of HIV-1 and postulate that they may represent a group of individuals at increased risk of transmitting HIV-1.

Methods: Seventy-three (73) HIV⁺ men not on therapy were enrolled. They produced matched blood and semen samples at the same time as undergoing tests for sexually transmitted infections. Viral load was determined by NASBA. Variables considered were; age, CDC status, CD4 count, BPVL > 100,000 c/ml, and the presence or absence of urethritis. SSS were defined as individuals with a SPVL/BPVL ratio > 1.

Results: Overall BPVL was significantly correlated with SPVL, Spearman’s σ 0.53 p < 0.0001. No men had BPVL values < 400 c/ml. In contrast 22/72 (30%) had SPVL < 400 c/ml despite detectable BPVL (e.g., non-shedders). Men who shed virus into semen had significantly higher BPVL than non shedders; 5.01 log₁₀ c/ml (range 3.4–6.3) vs 4.2 log₁₀ c/ml (3.0–5.5) p < 0.0001, Mann-Whitney U. Nine (9) men met the SSS criteria. These men had significantly higher SPVL compared with the main seminal shedding (SS) group; 5.6 log₁₀ c/ml (4.1–6.5) vs 3.9 log₁₀ c/ml (2.6–6.2) p < 0.001. In contrast, BPVL was not significantly different between SSS and SS (4.8 log₁₀ c/ml vs 5.02 log₁₀ c/ml, p = 0.9). SSS were generally older; 48 yrs vs 35 yrs p < 0.02 and the presence of urethritis was significantly over represented in the SSS group compared with the other groups, 3/9 (33%) vs 3/63 (4.8%) of other groups (Fishers Exact test p = 0.02). Importantly SSS was not simply explained by high BPVL as patients (pts) with BPVL > 100,000 c/ml were equally represented in both the SSS group 4/9 (44%) vs SS 25/63 (39%), p > 0.9. CD4 counts and CDC status were not significantly different between the SSS and SS.

Conclusions: In HIV+1 men with detectable BPVL not on therapy, ~30% had undetectable SPVL, ~58% had SPVL detectable at concentrations below their BPVL. Thus ~12% of this cohort was classified as SSS. Although urethritis accounted for 3/9 cases of SSS, studies are required to elucidate possible reasons for the excess shedding in those pts without urethritis. This important group of pts may pose a higher risk of transmitting HIV to their sexual partners.