- Email: [email protected]
Origins of human HHV8 in gay men
Newsdesk SIV infection less than expected in wild chimpanzees Wild-living chimpanzees can harbour simian immunodeficiency virus strains, such as SIVcpz, a new study has shown, although the prevelance is far less than expected. The viruses, which are closely related to HIV-1, had previously been isolated from chimpanzees (Pan troglodytes) in captivity. In the study, Mario Santiago (University of Alabama, Birmingham, AL, USA) and colleagues analysed faecal and urine samples from 58 wildliving chimps from Cote d’Ivoire, Uganda, and Tanzania for SIV antibodies and virion RNA. Only one healthy 23-year-old sexually active male from Gombe National Park in Tanzania was positive for SIVcpz infection; SIVcpz antibodies were found in two different urine samples and vRNA was isolated from three different faecal samples from this individual (Science 2002; 295: 465). Edward Holmes (Department of Zoology, Oxford University, Oxford, UK) finds it interesting that the prevalence of SIVcpz in wild-caught chimpanzees appears to be so low. “This is a real surprise because it is clear that chimpanzees are the donor
species for HIV-1 and therefore we might expect them to be rather commonly infected”, he says. It may be that the virus is transmitted only
Reservoir for human disease?
between certain groups within chimpanzee populations or, perhaps more likely, that the virus is at higher prevalence in chimpanzee populations not yet sampled, he explains. Kevin De Cock (Centers for Disease Control and Prevention, Atlanta, GA, USA) agrees that the number of animals sampled is low, but counters that if this prevalence is representative, it is conceivable that levels of infection in chimpanzee populations may have fallen. “It is important to remember that infectious diseases can emerge,
but also recede in animal populations, just as in human ones”, he says. According to senior author Beatrice Hahn, one of the public health implications of the study is that “the area of known infection must now be extended from Gabon and Cameroon in west-central Africa to the easternmost limit of the chimpanzee range in Tanzania”, she says. Although the prevalence of SIVcpz infection may be low, this large range increases the chances for the virus to have passed to people. “Our analysis indicates that east African chimpanzees harbor a virus too divergent to have been a source of human HIV-1 infection. However, SIVcpz has passed to humans in westcentral Africa, and the risk of additional introductions cannot be dismissed”, she stresses. Mike Huffman (Kyoto University, Japan), engaged in a follow-up study with Hahn, concludes that, ironically, “the continuing survival of wild apes that act as potential reservoirs for human infection could prove crucial in stemming the human epidemic.” Kath Senior
Origins of human HHV8 in gay men Although an epidemic of Kaposi’s sarcoma (KS) marked the beginning of the AIDS epidemic among gay men in San Francisco, CA, USA, infection with human herpesvirus 8 (HHV8) was already entrenched in this population, according to a new study (JAMA 2002; 287: 221–25). With the knowledge that HHV8 is an ancient virus, Dennis Osmond and Jeffrey Martin looked for evidence of HHV8 infection among gay men in San Francisco before the 1980s. “In the earliest samples from the first few months of 1978, 25% of the men were infected with HHV8 and less than 2% had evidence of HIV infection”, Osmond told TLID. Also, HHV8 seroprevalence at two time points—one in the mid-1980s and one in the mid-1990s—did not mirror the decline seen in HIV seroprevalence among gay men. “To our surprise, HHV8 prevalence was
constant”, Osmond added. This finding suggested to the researchers that those sexual practices that were constant throughout the past two decades were more likely to be an important source of HHV8 transmission. “By a process of elimination we have implicated oral sex as a practice that has contributed to the constant prevalence of HHV8 among gay men”, says Martin. Unlike HIV, HHV8 is frequently found in saliva and very rarely in semen. Also, HIV-infected men were about twice as likely to be shedding HHV8 as HIV-uninfected men. “Saliva comes into play in a lot of sexual behaviours, so it’s not clear cut what the routes of viral transmission are and it’s certainly possible that there are multiple routes”, Osmond said. Last year, Anna Wald (University of Washington, WA, USA) and
THE LANCET Infectious Diseases Vol 2 March 2002
http://infection.thelancet.com
colleagues reported that a history of deep kissing with an HIV-positive partner was an independent risk factor for infection with HHV8. “They have offered some novel insights into the epidemiology of the virus”, says Wald, “but, I don’t think their findings necessarily point to the mode of transmission”. Martin’s theory is that HHV8 isn’t easily transmitted by kissing otherwise it would be more prevalent in the heterosexual population. “You need to be circulating in a community where there are individuals with really high viral loads”, he said. Wald notes that “in other populations, such as in Africa and southern Europe, HHV8 is present in the heterosexual population. Clearly, the epidemiology of HHV8 is still somewhat a mystery, and there are contradictory lines of evidence”. Mary Quirk
131
For personal use. Only reproduce with permission from The Lancet Publishing Group.
species for HIV-1 and therefore we might expect them to be rather commonly infected”, he says. It may be that the virus is transmitted only
Reservoir for human disease?
between certain groups within chimpanzee populations or, perhaps more likely, that the virus is at higher prevalence in chimpanzee populations not yet sampled, he explains. Kevin De Cock (Centers for Disease Control and Prevention, Atlanta, GA, USA) agrees that the number of animals sampled is low, but counters that if this prevalence is representative, it is conceivable that levels of infection in chimpanzee populations may have fallen. “It is important to remember that infectious diseases can emerge,
but also recede in animal populations, just as in human ones”, he says. According to senior author Beatrice Hahn, one of the public health implications of the study is that “the area of known infection must now be extended from Gabon and Cameroon in west-central Africa to the easternmost limit of the chimpanzee range in Tanzania”, she says. Although the prevalence of SIVcpz infection may be low, this large range increases the chances for the virus to have passed to people. “Our analysis indicates that east African chimpanzees harbor a virus too divergent to have been a source of human HIV-1 infection. However, SIVcpz has passed to humans in westcentral Africa, and the risk of additional introductions cannot be dismissed”, she stresses. Mike Huffman (Kyoto University, Japan), engaged in a follow-up study with Hahn, concludes that, ironically, “the continuing survival of wild apes that act as potential reservoirs for human infection could prove crucial in stemming the human epidemic.” Kath Senior
Origins of human HHV8 in gay men Although an epidemic of Kaposi’s sarcoma (KS) marked the beginning of the AIDS epidemic among gay men in San Francisco, CA, USA, infection with human herpesvirus 8 (HHV8) was already entrenched in this population, according to a new study (JAMA 2002; 287: 221–25). With the knowledge that HHV8 is an ancient virus, Dennis Osmond and Jeffrey Martin looked for evidence of HHV8 infection among gay men in San Francisco before the 1980s. “In the earliest samples from the first few months of 1978, 25% of the men were infected with HHV8 and less than 2% had evidence of HIV infection”, Osmond told TLID. Also, HHV8 seroprevalence at two time points—one in the mid-1980s and one in the mid-1990s—did not mirror the decline seen in HIV seroprevalence among gay men. “To our surprise, HHV8 prevalence was
constant”, Osmond added. This finding suggested to the researchers that those sexual practices that were constant throughout the past two decades were more likely to be an important source of HHV8 transmission. “By a process of elimination we have implicated oral sex as a practice that has contributed to the constant prevalence of HHV8 among gay men”, says Martin. Unlike HIV, HHV8 is frequently found in saliva and very rarely in semen. Also, HIV-infected men were about twice as likely to be shedding HHV8 as HIV-uninfected men. “Saliva comes into play in a lot of sexual behaviours, so it’s not clear cut what the routes of viral transmission are and it’s certainly possible that there are multiple routes”, Osmond said. Last year, Anna Wald (University of Washington, WA, USA) and
THE LANCET Infectious Diseases Vol 2 March 2002
http://infection.thelancet.com
colleagues reported that a history of deep kissing with an HIV-positive partner was an independent risk factor for infection with HHV8. “They have offered some novel insights into the epidemiology of the virus”, says Wald, “but, I don’t think their findings necessarily point to the mode of transmission”. Martin’s theory is that HHV8 isn’t easily transmitted by kissing otherwise it would be more prevalent in the heterosexual population. “You need to be circulating in a community where there are individuals with really high viral loads”, he said. Wald notes that “in other populations, such as in Africa and southern Europe, HHV8 is present in the heterosexual population. Clearly, the epidemiology of HHV8 is still somewhat a mystery, and there are contradictory lines of evidence”. Mary Quirk
131
For personal use. Only reproduce with permission from The Lancet Publishing Group.