Hepatitis C virus is present in large enough quantities in the rectal fluid of men with HIV and hepatitis C co-infection to permit HCV transmission without the presence of blood, researchers from the Icahn School of Medicine, Mount Sinai Hospital, New York, reported on Sunday at the 2015 AASLD Liver Meeting in San Francisco.
Until now it was assumed that hepatitis C transmission during anal intercourse occurred as a result of bleeding, or through transmission in semen. Hepatitis C is easily transmitted in blood; just 10 to 20 hepatitis C virions are enough to establish hepatitis C infection through contaminated medical equipment or used injecting equipment, it has been estimated. Transmission has been theorised to take place as a result of contact between blood and the mucosa of the penis, or contact with damaged tissue on the hand during fisting. Transmission has also been theorised to occur as a result of the transfer of blood containing HCV from one person to another, on the penis, on a gloved fist or on sex toys, during group sex.
Another presentation at the AASLD Liver Meeting by the same research group, led by Daniel Fierer, reported that HCV was present in 27% of three paired samples of blood and semen collected from 33 men with HIV and HCV co-infection, with virus levels sufficient to transmit HCV.
The possibility that hepatitis C virus might be present in the fluid on the surface of the rectal mucosa had not been previously explored. Seeking to understand how HCV is being transmitted widely among men who have sex with men (MSM), especially those with HIV infection, researchers from Icahn School of Medicine recruited 45 MSM with HIV and hepatitis C co-infection, 12 of whom were acutely infected.
Study participants had a median age of 43 years, 60% were white and 87% had genotype 1a HCV infection. Participants had high CD4 cell counts (median 582 cells/mm3) but HIV viral load suppression was not reported. Participants had moderately high HCV viral load (5.89 log10 IU/ml), and those with acute HCV infection had somewhat higher median viral load (6.42 log10 IU/ml) than those with chronic HCV infection (5.62 log10 IU/ml).
Men underwent rectal fluid collection by insertion of a swab which sampled the fluid on the rectal mucosa approximately 7cm beyond the anus. Fluid was analysed for HCV RNA using the COBAS HCV test, which has a lower limit of detection of 7 IU/ml. Swabs were analysed for blood. Participants also underwent HCV RNA testing of blood, as well as tests for rectal sexually transmitted infections and syphilis.
Hepatitis C virus was detected in 20 of the 45 specimens (47%) (two samples could not be processed). The median HCV RNA was 2.92 log10 IU/ml and the level of HCV RNA in rectal fluid was strongly correlated with the level in blood. Rectal HCV was much more likely to be detected in participants who had a high HCV viral load in blood. Rectal HCV detection was associated with having an HCV viral load in blood above 5 log10 IU/ml (P = 0.011).
There was no difference in detection of rectal HCV between men with acute or chronic infection, and no correlation with the presence of rectal sexually transmitted infections or syphilis.
The researchers concluded that the quantities of HCV detectable in rectal fluid would be sufficient for HCV transmission to take place during anal intercourse, even without the presence of blood. HCV might also be transmitted without the presence of blood during group sex, for example on the penis of the active partner, on sex toys, through fisting or through use of douching equipment, even where condoms or gloves are used.
The results of both studies led the authors to recommend the use of condoms for anal intercourse to men with HIV infection.
HCV also present in faeces
An unrelated German study also presented at the AASLD Liver Meeting this week shows that HCV is present in faeces, leading the authors to suggest that contact with faeces may be a route of transmission, at least in men. The study analysed stool samples from 98 men and women with HCV mono-infection for the presence of HCV RNA. Sixty-eight samples were positive for HCV RNA (69%) but blood was present in only five of these samples. HCV was detected significantly more often in the stool samples of men (83% vs. 52%; p < 0.001) and in people with low platelet counts.
Foster A et al. Rectal shedding of HCV in HIV/HCV coinfected men. AASLD Liver Meeting, San Francisco, abstract 89, 2015.
Heidrich B et al. HCV RNA and HCV core antigen are frequently detectable in stool of men chronically infected with HCV: Is feces a potential source of infection? AASLD Liver Meeting, San Francisco, abstract 1002, 2015.
Turner S et al. HCV in semen of HIV-infected men during acute and chronic infection. AASLD Liver Meeting, San Francisco, abstract 1852, 2015.