High rates of anal human papilloma virus infection have been found in an Italian cohort of HIV-positive men. A study, published in the October 1st edition of AIDS, also reports that the most common strains of human papilloma virus were those which carry a low risk of anal cancer. Human papilloma virus viral load was highly variable and did not appear to be linked to the strain of the virus or the strength of each individual patient’s immune system.
Human papilloma virus (HPV) is a very common sexually transmittable virus, which often causes no symptoms. Infection with certain strains of HPV is associated with a higher risk of cervical cancer in women, and anal cancer in both men and women. Anal HPV is common in gay men (especially HIV-positive men); HIV-positive men are at particular risk of developing anal cancer.
Markers that might indicate the risk of progression have not been well studied. In this study, an Italian research team studied the prevalence, genotypes (strains), and genotype-specific DNA viral loads of anal HPV in a sample of HIV-positive men at a colorectal clinic in Rome. A group of 25 HIV-negative men was also studied as a control.
The study was confined to men with no anal cellular abnormalities: men were excluded if they had abnormal anal cytology, a history of anal cancer, or were already being treated for anal human papilloma virus infection. Thirty-six HIV-positive patients were enrolled in total; those with anal HPV (n=29) had a median age of 43 years, a median CD4 count of 397 cells/mm3, and 86% had an HIV viral load below 50 copies/ml. These and other clinical characteristics were not significantly different from the seven HIV-positive patients who did not have HPV, however HPV-positive men were much more likely to be gay and to have a larger number of sexual partners.
Prevalence and genotypes
HPV DNA was detected in 81% of the HIV-positive men and 68% of the HIV-negative men (p > 0.05). Almost all homosexual men were HPV-infected (94% of HIV-positive and 89% of HIV-negative).
HPV was successfully genotyped in all but four of the HIV-positive and two of the HIV-negative men. Low-risk HPV types were more common than high-risk types. “High-risk and probable high-risk” HPV types (defined as eighteen types including 16, 18, 31, 33 and 35) were seen in 48% of the HIV-positive and 33% of the HIV-negative men. A total of fourteen HPV types, including nine high-risk types, were isolated in HIV-positive men; seven types, including five high-risk, were seen in the HIV-negative controls. Three (12%) of the HIV-positive, but none of the HIV-negative men, had more than one type of HPV.
Human papilloma virus viral load
HPV DNA viral load was measured by PCR for twelve different HPV genotypes, including seven high-risk types. Within each genotype the HPV viral load was extremely variable between individuals, ranging from under 1 log10 to over 6 log10 copies/ng. However, it did not differ significantly overall between HIV-positive and HIV-negative men. In many samples, low-risk HPV (6, 61, 70, and 74) viral loads were comparable with those of high-risk HPVs.
Conclusions
In this, possibly the first study of type-specific anal HPV viral load, very wide variations in viral load were seen; these variations “appear to be independent of patient immune status and of HPV genotype.”
Although the overall rates of HPV prevalence found here were comparable to other studies, other studies have often found higher rates of high-risk genotypes and multiple-genotype infection. The researchers speculated that the PCR amplification may have favoured the more abundant types and underestimated the less populous co-infecting strains.
While no direct links between viral load and clinical condition were drawn, high cervical HPV viral load has been linked to HPV persistence and increased risk of progression to cervical cancer; the researchers here note that “a high [anal HPV] viral load could be regarded as a marker of persistency”, and that “human papilloma virus genotype risk and viral load should be further evaluated for their potential predictive role in persistence and progression.” They also suggest that “apparently benign perianal warts could, in HIV-positive patients… progress to high-grade [anal disease] or cancer; hence, these patients should be monitored frequently.”
Reference:
Pierangeli A et al. Type-specific human papillomavirus-DNA load in anal infection in HIV-positive men. AIDS 22:1929–1935, 2008.