infection during pregnancy or delivery may greatly increase the subsequent risk
of foetal or infant HIV infection, Thai researchers report.
formula-fed infants of HIV-infected mothers receiving zidovudine prophylaxis, HIV
infections were more frequent in infants with congenital or acquired cytomegalovirus (CMV)
infection, Woottichai Khamduang and colleagues reported in a retrospective
case-control study from a Thai clinical trial cohort published in the advance
online edition of the Journal of Acquired
Immune Deficiency Syndromes.
independent risk factors maternal viral load is acknowledged as being the most
important predictor of mother-to-child HIV transmission. While the presence of infant
CMV infection has been looked at within the context of HIV infection of mothers
and infants, the authors note it has never been subject to multivariate
non- HIV-infected populations between 0.1% and 2% of infants become infected
with CMV during pregnancy, and 5% - 10% become infected during birth. CMV is a common virus from the family of herpes viruses that may eventually infect the majority of otherwise healthy adults, and in most cases causes no more than a mild viral infection.
However in a minority of infants infected with CMV during pregancy, infection can lead to more serious health problems such as hearing loss and learning difficulties.
In people with HIV infection who suffer serious immune system damage, including infants, CMV can cause serious AIDS-defining disease in the gastrointestinal tract or in the eye (retinitis).
HIV-infected infants rates of infection ranging from 0-26% during pregnancy
have been recorded; the two largest studies have shown a 10% transmission rate.
Among formula-fed infants a number of studies have shown high overall rates of
CMV in HIV-infected infants, the authors of the Thai study note.
a retrospective case-control study using data and frozen specimens from a
non-breastfeeding cohort the authors looked at predictors, including infant CMV
infection, of HIV transmission during pregnancy and birth to see whether CMV
was independently associated with HIV transmission.
study population came from a clinical trial that took place in Thailand
from 1997 to 2001 to look at the effects of long- and short-term zidovudine
monotherapy in the prevention of mother-to-child HIV transmission.
parent study included 1409 live births of which 97 were HIV-infected.
infants were matched with HIV-uninfected infants according to maternal viral
load; so ensuring the elimination of the strongest known risk factor for MTCT.
A total of 194 control mothers and 196 control HIV-uninfected infants were
included (one HIV uninfected infant had an infected twin and one matched mother
had two uninfected infants).
were not tested for CMV since studies have shown CMV prevalence among pregnant
women in Thailand
to be close to 100%. Infants were formula-fed from birth. Infant blood samples
were tested at birth, six weeks and at four, six, 12 and 18 months of age.
were screened by testing 18-month plasma or serum for CMV antibodies. All
earlier samples were tested to time the start of CMV infection.
baseline CD4 cell counts, length of zidovudine prophylaxis, mode of delivery,
sex of infant, prematurity and birth weight were all tested for HIV
length of zidovudine prophylaxis was lower among mothers with infant HIV transmission
compared to no transmission, 5.4 weeks and 6.8 weeks, (p=0.04) respectively.
to 90% (84) of the 97 HIV-infected infants had samples to time the infection.
40% were infected during pregnancy and 58% during delivery.
zidovudine prophylaxis nor CD4 cell count were significantly associated with
HIV transmission, whereas prematurity and low birth weight were (p=0.02 and
p=0.003, respectively). The authors note this may be explained by the matching
of case-controls according to the strongest and most consistent risk factor -
maternal viral load.
mother/infant characteristics were similar in both sets of mother-infant pairs.
HIV-infected infants congenital and overall CMV infections were more common
than in HIV-uninfected infants, 14% (as in other studies) compared to 3%; and
84% compared to 63%, respectively. Acquired CMV infection was common to all
infants in the study. CMV infection during delivery and the period immediately
following birth accounted mostly for the higher percentage found in
HIV-infected infants. The authors believe this can be attributed to cervical
(OR: 4.9, p=0.009) and overall CMV (OR: 3.0, p<0.001) infection were
strongly associated with overall HIV infection
timing of both HIV and CMV infections are of importance. Congenital CMV was
linked to both HIV infection during pregnancy (OR:8.1, p=0.01) and HIV
infection acquired during birth (p=0.03). However, CMV infection acquired after
birth was not associated with HIV infection during pregnancy (OR: 0.9, p=1.00)
but was significantly associated with HIV infection acquired during delivery
(OR: 2.5, p=0.04).
order of the timing and linking of infections, the authors note, suggests that
foetal or infant CMV infection predisposes to HIV infection and not the other
way around. There is no evidence to support this and it may be because of some
unknown confounding factor, they add.
authors note that it is probable that the two infections are linked in some
way, adding it is likely that one viral infection facilitates the other.
authors note that 85% of HIV-infected infants were co-infected with CMV by 18
months of age and suggest their impaired immune functioning may make them more
susceptible to horizontally acquired infections.
authors conclude that in an analysis of multiple risk factors for
mother-to-child transmission in a formula-fed population of HIV-infected
mothers “congenital and acquired CMV infections are strong independent
predictors of mother-to-child transmission.”