Vertical HIV transmission may be influenced by complex synergies with other STI – such as Cytomegalovirus

The apparently greater susceptibility of sub-Saharan African women to HIV infection has led researchers to consider the various potential synergies between HIV and other genital infections (White & Glynn (STIs); Lurie & Matthews (STIs)) or conditions of the vaginal microbiome (The susceptibility of heterosexual sub-Saharan women (STI/blog)).  A recent study, Adachi & Nielson-Saines, brings this wider perspective to bear on mother-to-child transmission, casting some fresh light on the complex interrelation between the ‘vertical’ transmission of HIV and active and Cytomegalovirus (CMV) viruria.

The study is a late spin-off from HPTN-040 (reported in a 2012 paper by Nielson-Saines & Mofenson IN&M).  This compared the efficacy of different post-partum ART regimes for HIV infected children.  The original participants were c. 1,700, largely S. American women who presented in late pregnancy with HIV.  Matched urine specimens were available for 264 mother-child pairs.  Researchers returned to these specimens after the closure of the main trial in order to investigate through PCR testing the impact of CMV viral shedding on vertical transmission of Cytomegalovirus (CMV) and its concomitants.

The results were as follows.  Out of the 264 maternal urine samples 24 (9.2%) showed evidence of CMV shedding. Matching these maternal samples with infant samples revealed vertical CMV transmission in 10/264 cases.  Five of these were from among the 24 with maternal shedding (20.8%); five were from among the 240 without shedding (2.1%).  When the ratio of transmissions with shedding to transmissions without shedding was adjusted for mode of delivery, maternal gonorrhoea and maternal HIV viral load, it came out at 29.7%.   Women with CMV viral shedding also showed significantly higher odds of HIV transmission to their infants (aOR = 5.6%).

These findings are striking; but what is their relevance?  Maternal CMV shedding may indeed be a very good marker of vertical CMV and HIV transmission.  Presumably, however, health workers would give appropriate anti-retroviral therapy to 100% of infants at risk of HIV infection in any case – and anti-retroviral therapy has been shown to deal successfully with the CMV, without the need to give additional, and potentially toxic, drugs specifically for the CMV (Anfumborn & Tejiokern). So N&M’s research have little implications for management of these infections.

However, their importance may lie in showing how the problem of HIV – including vertically transmitted HIV – cannot be isolated from the wider problem of STI and sexual health in general. Maternal HIV may, for example, increase the likelihood of CMV transmission, and CMV infection of the infant may, in turn, lead to a more rapid progression of HIV.  Complex synergies with vertical HIV transmission may operate in the case of other STI as well – such as HSV-2 (Sivarajah & Tan (STIs)).  So the messages to take away may include not just ‘the necessity of controlling maternal HIV infection during pregnancy through cART’, but also the importance of STI control – above all through the promotion of practices of safe sex.