Mum-to-baby transmission rate now below one per cent
Less than one in a hundred babies born to HIV-positive mothers in the UK is now being infected, according to the National Study of HIV in Pregnancy & Childhood. Between 2003 and 2006 only 38 babies born to 3695 women were infected with HIV (1%), down from 1.6% in 2000-02. Ninety-five per cent of women had at least two weeks of HIV treatment, the remaining five per cent being largely due to late diagnosis, and 41% of women achieved an undetectable viral load. Three babies were infected even when the mother had an undetectable viral load, but it was thought they acquired HIV in the womb before their mums were diagnosed.

Herpes and STIs aid gay HIV transmission
A study of gay men in San Francisco has found that the only factors making HIV infection more likely were herpes in the positive partner or a bacterial STI like syphilis or gonorrhoea in the negative partner. Researcher David Butler traced the HIV positive sexual partners of recently-diagnosed gay men and then by genetically comparing viruses determined who had been a source of HIV infection and who hadn’t. He then looked at factors more likely to make transmission happen between a poz/neg couple. A third of transmissions featured a positive man with herpes and a negative man without; in contrast only one non-transmitting couple out of 30 featured this pattern. Butler calculated that HIV transmission was 16 times more likely if herpes transmission happened at the same time. Of note was the fact that a quarter of all transmitters had semen HIV viral loads under 110 – though they might have been higher at the time of transmission. Studies like this one suggest that giving HIV positive people medication to suppress herpes might make them less likely to pass on HIV.

Half of all HIV transmitted by people infected for less than a year
At least year’s Retrovirus Conference, study from Quebec suggested that half of all HIV infections are passed on by people who have been infected for less than six months. Several studies at this year’s conference investigated the same question in different populations. Researcher Gareth Hughes looked at recent HIV infection in gay men in Scotland. By looking at the way viruses are genetically related, he was able to group them in ‘families’ indicative of rapid transmission within a group of people. He estimated that a quarter of HIV infections in gay men in London came from people infected for less than six months, and half from people infected for less than a year. Swiss researchers established similar figures for gay men, heterosexuals and injecting drug users, though the proportion coming from people infected for six months varied from one in five to over half depending on locale. And the Quebec researchers revised their estimate for infections acquired from people with less than six months’ infection down to one-third. If a high proportion of HIV is transmitted by people who’ve recently caught it, it has implications for prevention strategies, as many of these will not be aware of their infection.

Fuzeon could prevent transmission to babies
In cases where more conventional drugs have failed, the injectable HIV drug T-20 (Fuzeon®) could find a new use as a way of preventing mother-to-baby infection, the Retrovirus conference heard. Fourteen HIV-positive pregnant women at an HIV clinic in Germany were given Fuzeon. Despite only taking it for an average of 17 days their average viral load went down from 75,000 to 200. One woman started with a viral load of over a million and ended up with one of 1700. As a result, no babies were born with HIV. Dr Alison Rodger of the Royal Free Hospital, reviewing the study, said that Fuzeon could be “a useful option, particularly for late presenters, multi-drug-resistant virus and premature delivery.”

Big herpes trial fails
On the other hand, a big international trial which gave HIV negative people with herpes an anti-herpes drug to see if suppressing herpes would make them less vulnerable to HIV has concluded that it made little difference. The study involved giving half of a group of
3172 people with herpes (57% of them gay men in the US and Peru, the rest women in Africa) the drug acyclovir and half of them an inactive placebo. There were 75 HIV infections in people taking acyclovir (4.7%) and 84 on placebo (5.2%) – not a significant difference. There was a reduction in herpes symptoms, but not by
the amount seen in other herpes trials. Volunteers had excellent adherence, with 94% of doses taken, and there was a trend towards lower HIV incidence in people with better adherence. Lead investigator Connie Celum said that the result from this, the largest-ever trial of herpes suppression, was “surprising, disappointing and important,” but said she felt to concept of suppressing herpes in order to slow HIV transmission was still valid. Another large international trial giving acyclovir to HIV positive people is still ongoing.

Immune therapy produces long-term CD4 increases, few side effects
Researchers have been interested for years in the idea of stimulating increases in CD4 count by giving patients booster doses of naturally occurring cytokines, body chemicals that stop CD4 cells self-destructing. Previous trials of the cytokine interleukin-2 (IL-2) have however foundered on its tendency to produce unpleasant fluey side effects. A French study gave six patients on stable antiretroviral therapy with undetectable viral loads eight injections over two weeks of a cytokine called interleukin-7 (IL-7). Patients reported minimal side effects and experienced a sustained CD4 count increase of about 50 cells that lasted for about three months. Tripling the dose produced a doubling of CD4 count, from an average of around 200 to 400, which lasted for at least six months, though it tailed off over time. However IL-7 also stimulates HIV and three out of eight patients given the larger dose experienced small detectable viral loads (up to 840 copies) that persisted in one case for 11 months. Results are being closely studied to see if further trials of IL-7 can establish an ideal safe dose.