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Selection and fading of resistance mutations in women
and infants receiving nevirapine to prevent HIV-1
vertical transmission (HIVNET 012)
Susan H. Eshleman, Martin Mracna, Laura A. Guay, Martina Deseyvea,
Shawn Cunningham, Mark Mirochnickb, Philippa Musokec,
Thomas Flemingd, Mary Glenn Fowlere, Lynne M. Mofensonf,
Francis Mmirogand J. Brooks Jackson
Objective: To examine the emergence and fading of NVP resistance (NVPR) mutations
in HIV-1-infected Ugandan women and infants who received single dose NVP to
prevent HIV-1 vertical transmission.
Design: We examined NVPRin women and infants who received NVP in the
HIVNET 012 clinical trial, including 41 out of 48 women with infected infants, 70
randomly-selected women with uninfected infants, and 33 out of 49 infected infants.
Methods: Plasma HIV-1 was analyzed using the Applied Biosystems ViroSeq HIV-1
Genotyping System.
Results: NVPRmutations were detected in 21 out of 111 (19%) women tested 6± 8
weeks after delivery. The rate of NVPRwas similar among women whose infants were
or were not HIV-1 infected. K103N was the most common mutation detected. NVPR
mutations faded from detection within 12±24 months in all 11 evaluable women.
High baseline viral load and low baseline CD4 cell count were associated with
development of NVPR. NVPRmutations were detected in 11 out of 24 (46%) evaluable
infants who were infected by 6±8 weeks of age. The most common NVPRmutation
detected in infants was Y181C. Those mutations faded from detection by 12 months of
age in all seven evaluable infants. Of nine evaluable infants with late HIV-1 infection,
only one had evidence of NVPR.
Conclusions: NVPRwas detected more frequently in infants than women following
NVP prophylaxis, and different patterns of NVPRmutations were detected in women
versus infants. NVPRwas detected infrequently in infants with late HIV-1 infection.
NVP-resistant HIV-1 faded from detection in women and infants over time.
&2001 Lippincott Williams & Wilkins
AIDS 2001, 15:1951±1957
Keywords: Clinical trial, drug resistance, genotype, HIV-1, infant, nevirapine,
pregnancy, prophylaxis, Uganda, vertical transmission
From the Department of Pathology, The Johns Hopkins Medical Institutions, Baltimore, Maryland, the aFred Hutchinson Cancer
Research Center, Seattle, Washington, the bDepartment of Pediatrics, Boston University, Boston, Massachusetts, USA, the
cDepartment of Paediatrics, Makerere University, Kampala, Uganda, the dDepartment of Biostatistics, University of Washington,
Seattle, Washington, the eDivision of AIDS, NIAID/NIH, Rockville, the fPediatric, Adolescent, and Maternal AIDS Branch,
NICHD/NIH, Rockville, Maryland, USA, and the gDepartment of Obstetrics and Gynaecology, Makerere University, Kampala,
Uganda.
Requests for reprints to: S. Eshleman, Department of Pathology, The Johns Hopkins Medical Institutions, Ross Building 646,
720 Rutland Avenue, Baltimore, Maryland 21205, USA.
Received: 9 March 2001; revised: 8 June 2001; accepted: 13 June 2001.
Note: The content of this publication does not necessarily re¯ect the views or policies of the Department of Health and
Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the US
Government.
ISSN 0269-9370 &2001 Lippincott Williams & Wilkins 1951
Introduction
Nevirapine (NVP) is a potent non-nucleoside inhibitor
of HIV-1 reverse transcriptase (RT). In the HIV-
NET 012 clinical trial, administration of a single
200 mg dose of NVP to pregnant Ugandan women at
the onset of labor and a single 2 mg/kg dose to their
infants within 72 h of birth was shown to signi®cantly
reduce the rate of HIV-1 mother-to-child transmission
(MTCT) [1,2]. That regimen was more effective than a
short course of zidovudine prophylaxis starting in labor,
and was simpler and much less expensive. The ef®cacy,
simplicity and low cost of the HIVNET 012 NVP
regimen make it attractive for use in developing
countries. The World Health Organization recently
recommended implementation of this regimen as one
of several options for prevention of MTCT in re-
source-limited settings [3].
When NVP is administered as monotherapy for treat-
ment of HIV-1 disease, rapid selection of HIV-1
variants with nevirapine resistance (NVPR) mutations
occurs [4]. We recently reported that NVP-resistant
HIV-1 can also be selected in women who receive
single dose NVP prophylaxis to prevent HIV-1 MTCT
[5]. In that report, we analyzed HIV-1 from 15 women
who were enrolled in the Ugandan Phase I/II trial,
HIVNET 006 [6]. Women in HIVNET 006 received
the same NVP prophylaxis regimen as women in
HIVNET 012. In that cohort, the K103N NVPR
mutation was detected in HIV-1 from three out of 15
(20%) women 6±8 weeks after delivery. Our analysis
of women in HIVNET 006 further suggested that a
more prolonged exposure to NVP favors selection of
NVP-resistant HIV-1 [5]. In this report, we extend our
previous studies by examining the emergence and
fading from detection of NVP-resistant HIV-1 in a
large cohort of Ugandan women and infants who
received NVP prophylaxis in the HIVNET 012 trial.
Materials and methods
HIV-1 Genotyping
HIV-1 genotyping was performed using the Applied
Biosystems ViroSeq HIV-1 Genotyping System (Ap-
plied Biosystems, Foster City, California, USA). For
some women, the amount of plasma available for
analysis was limited and genotyping was performed
with less than the recommended 0.5 ml plasma. Due to
limitations in sample volumes, all infant samples were
analyzed using 0.1 ml plasma. In this system, HIV-1
RNA is extracted from plasma samples and reverse
transcribed with murine Moloney leukemia virus re-
verse transcriptase. A 1.8 kb DNA fragment is then
ampli®ed in a single 40-cycle PCR with AmpliTaq
gold polymerase and uracil N-deglycosylase decontami-
nation control. PCR products are puri®ed using spin
columns, analyzed by agarose gel electrophoresis, and
sequenced with pre-mixed BigDye sequencing reagents
in seven separate reactions. Sequencing products were
analyzed using an ABI 377 automated sequencer. The
resulting sequences were assembled and mutations
associated with NVPR(A98G, L100I, K103N, V106A,
V108I, Y181C, Y188C, G190A) were identi®ed using
the HIV-1 Genotyping Software package v2.2 (Applied
Biosystems). Bidirectional sequences were obtained in
the region of interest (RT amino acids 98±190) for all
samples analyzed in this report. For quality control,
NVPRmutations present as amino acid mixtures were
identi®ed only if the corresponding nucleotide mixture
was present in the sequences of both DNA strands.
Study visits and results
The HIVNET 012 study protocol was reviewed and
approved by institutional review boards in Uganda and
the USA, and informed consent was obtained from all
women prior to enrollment. Women had not received
prior antiretroviral therapy and did not receive anti-
retroviral therapy after the single dose of NVP, con-
sistent with the standard of care in Uganda. Women
were evaluated at study entry, delivery, and 7 days and
6±8 weeks after delivery. Women gave separate in-
formed consent for collection of follow-up blood
samples at later time points. Infants were evaluated at
birth, 7 days, 6, 10, and 14 weeks, and 6, 9, 12, and 18
months of age. Blood was obtained at birth, 6 and 14
weeks, and 12 and 18 months of age.
Detailed methods and results of HIVNET 012 have
been presented elsewhere [1]. In the ®nal analysis, 311
women receiving NVP had 320 live births (eight
multiple births) [2]. HIV-1 infection was diagnosed in
infants prior to 18 months of age using HIV-1 RNA
PCR, con®rmed by an additional HIV-1 RNA PCR
or HIV-1 culture. At 18 months of age, HIV-1
infection was diagnosed by enzyme immunoassay
(EIA), and if reactive, by con®rmatory Western blot
[1]. Forty-nine out of 320 infants were HIV-1 infected
despite NVP prophylaxis, 37 (including one set of
twins) by age 6±8 weeks and 12 after age 6 ±8 weeks
(Table 1). Infected infants with negative virologic assays
through age 6±8 weeks and who had their ®rst positive
virologic test after age 6±8 weeks were de®ned as
having late infection.
NVPRanalysis study subjects
We analyzed plasma HIV-1 from samples collected 6±
8 weeks after delivery from a subset of women enrolled
in HIVNET 012. Forty-eight women had 49 infants
(including one pair of twins) who became infected
despite NVP prophylaxis. Plasma samples were avail-
able from 33 out of 36 (92%) women whose infants
were infected by age 6±8 weeks; genotyping was
successful for 32 of those samples. Of the remaining
AIDS 2001, Vol 15 No 151952
263 women who had infants who were not HIV-1-
infected, a random sample of 72 women was selected
for evaluation. Those women had infants who were
uninfected and alive at 6±8 weeks of age. Women
were excluded if their viral load was ,2000 copies/ml
at baseline or 6±8 weeks after delivery to provide
suf®cient HIV-1 RNA for genotyping. HIV-1 geno-
typing was successful for 70 of those 72 women.
Additionally, samples collected 6±8 weeks after deliv-
ery were available from nine out of 12 (75%) of the
mothers of the late-infected infants. Plasma samples
were available and HIV-1 was genotyped from 24 out
of 37 (65%) HIV-1 infected infants with infection
diagnosed by age 6±8 weeks and nine out of 12 (75%)
diagnosed after age 6±8 weeks (Table 1).
Statistics
Logistic regression was used to evaluate correlates of
maternal NVPR, including transmission status, baseline
viral load, and CD4 cell counts. All statistical analyses
were done with SAS (version 8.1).
Results
Quality control of sequence data
We analyzed 185 plasma samples from 144 individuals
who received NVP in HIVNET 012, including 111
out of 311 (36%) women and 33 out of 49 (67%)
infected infants. Samples collected at more than one
time-point were genotyped for 23 out of 144 indivi-
duals. For each sample, a sequence corresponding to
protease amino acids 1±99 and RT amino acids 1 ±324
was obtained. Phylogenetic reconstructions of the
entire data set revealed the following: in cases where
more than one sequence was analyzed from a given
individual, all sequences from that individual clustered
together; sequences from each infant clustered most
closely with the sequence from the corresponding
mother. Comparison of the genetic distances of all 185
sequences revealed only three cases where two se-
quences were identical: the sequence from one infant
at 6±8 weeks of age was identical to the sequence from
the same infant at 14±16 weeks of age; the sequence
from one infant at birth was identical to the sequence
from the same infant at 14±16 weeks of age; the
sequence from one infant at 6±8 weeks of age was
identical to the sequence from the corresponding
mother at 6±8 weeks post-partum. This analysis pro-
vided evidence that the data set was valid, without
evidence of sample cross-contamination or sample mis-
identi®cation.
NVPRmutations in women 6±8 weeks after
delivery
We ®rst analyzed samples from 102 women, including
70 whose infants were uninfected at 6±8 weeks, and
32 whose infants were diagnosed with HIV by 6±8
weeks. Analysis of women with late-infected infants is
described later in this report. NVPRmutations were
detected in 18 out of 102 (18%) of women (Tables 1
and 2). The rates of resistance among women whose
infants were and were not infected by 6±8 weeks were
not signi®cantly different. Baseline (pre-NVP) samples
were available from all seven women whose infants
were HIV-1 infected and who had NVPRmutations
detected 6±8 weeks after delivery. All seven samples
lacked detectable NVPRmutations. Those ®ndings
were consistent with our previous report that demon-
strated an absence of NVPRmutations in 27 antiretro-
viral drug-naive Ugandan adults [7]. Follow-up samples
collected 12±24 months after delivery were available
from 11 out of 18 women who had NVPRdetected
6±8 weeks after delivery. All 11 follow-up samples
lacked detectable NVPRmutations (Table 1).
Logistic regression analysis revealed an association be-
Table 1. NVPRanalysis of study samples.
Subjects in the
HIVNET 012
NVP arm (n)
Subjects
genotyped at 6± 8
weeks (n)
Subjects with
NVPRat 6± 8
weeks (n)
Subjects genotyped
after 6± 8 weeks (n)
Subjects with NVPR
after 6± 8 weeks (n)
All women 311 111/311 21/111 11/21 0/11 (12± 24 months)
Infant uninfecteda263 70/263 11/70 6/11 (24 months) 0/6 (24 months)
Infant positive by 6± 8 weeksb36 32/36 7/32 5/7 (12± 18 months) 0/5 (12± 18 months)
Infant positive after 6± 8 weeksb12 9/12 3/9 0/3 ±
All infantsc320
Uninfected 271 ± ± ± ±
Infectedb49
Positive by 6±8 weeks 37 24/37 11/24 9/11 (14±16 weeks)
3/11 (12 months)
5/9 (14± 16 weeks)
0/3 (12 months)
Positive after 6±8 weeks 12 ± ± 9/12 1/9d
aTesting was performed on a random set of 72 women (see Methods). Genotyping was successful for 70 out of 72 women. bGenotyping was
performed on all available samples. Genotyping was unsuccessful for one of these women. cIncluding seven sets of twins and one set of triplets.
dSee Table 4 for the age at diagnosis and testing for each infant. Positivediagnosed with HIV-1 infection.
NVP resistance in HIVNET 012 Eshleman et al. 1953
tween baseline viral load and development of NVPR
mutations and between baseline CD4 cell count and
resistance. In a univariate model, women with high
viral loads were more likely to develop resistance (per
increase of one log10 HIV-1 RNA: odds ratio, 3.97;
95% con®dence interval, 1.54±10.20; P0.0042).
Similarly, women with low CD4 cell counts were
more likely to develop resistance (per decrease of 100
cells: odds ratio, 1.63; 95% con®dence interval, 1.20±
2.21; P0.0016).
NVPR mutations in HIV-1 infected infants
diagnosed by age 6±8 weeks
Plasma samples collected at 6±8 weeks of age were
available for 24 out of 37 infants who were diagnosed
with HIV-1 infection by 6±8 weeks of age. NVPR
mutations were detected in 11 out of 24 (46%) of those
infants (Table 2). Birth samples (plasma from peripheral
or cord blood) were available from 10 of those 11
infants. Analysis of NVPRmutations was successful for
nine of those samples, all of which lacked detectable
NVPRmutations. Follow-up samples collected at 14±
16 weeks of age were available from nine out of 11
infants who had NVPRmutations at 6± 8 weeks of age.
Of those, four out of nine lacked detectable NVPR
mutations. In contrast, ®ve out of nine samples had the
same NVPRmutations detected in the 6± 8 week
sample from the same infant. The NVPRmutations
present in the 14±16 week samples from those ®ve
infants were: Y181C (three), K103N (one), and
Y181C G190A (one). Follow-up samples collected
at 12 months were available for three out of those ®ve
infants, all of which lacked detectable NVPRmuta-
tions.
Ten out of the 11 infants who had NVPRmutations
detected at 6±8 weeks of age were HIV-1 RNA
positive at birth, compared to nine out of 13 infants
who did not have NVPRmutations. The death rate
within the ®rst year of life was similar among those
with and without NVPRmutations (3/11 versus 5/13,
respectively). However, the numbers were too small
for meaningful statistical analysis.
Comparison of NVPRmutations in HIV-1 infected
infants diagnosed by age 6-8 weeks and their
mothers
Different patterns of NVPRmutations were detected in
women and infants. In women, the most common
mutation was K103N, whereas in infants it was Y181C
(Table 2). K103N was detected in 16 out of 18 (89%)
women versus only two out of 11 (18%) infants. In
contrast, Y181C was detected in six out of 18 (33%)
women versus 10 out of 11 (91%) infants. NVPR
mutations were also compared in mother±infant pairs,
in which both mother and infant had samples analyzed
from 6±8 weeks after delivery. Twenty-two mother ±
infant pairs were available for analysis. In 12 pairs,
samples from both the mother and infant lacked
detectable NVPRmutations. The NVPRmutations
detected in the other 10 mother±infant pairs are shown
in Table 3. Six infants who had NVPRmutations at 6±
8 weeks of age had mothers who lacked detectable
NVPRmutations at that time; all of those infants had
HIV-1 infection at the time of birth. In each case
where both mother and infant had NVPR, the pattern
Table 2. NVPRmutations detected in women and infants with HIV-1 infection diagnosed by age 6±8 weeks.
Women
Women whose infants were Infants
infected by age 6±8 weeks Women with uninfected All women
Mutations detected (n 32) infants (n 70) (n 102) (n 24)
K103N 5 6 11 1
K103N Y181C 1 2 3 1
K103N Y181CV106A 1 1
K103N Y181CG190A 1 1
Y181C 116
Y181C Y188C 2
Y181C G190A 1
V108I 11
Total 7 11 18 11
Table 3 Comparison of NVPRmutations in infants with HIV-1 infec-
tion diagnosed by age 6± 8 weeks of age and their mothers.
Mother Infant
WT Y181C
WT Y181C
WT Y181C
WT Y181C
WT Y181C G190A
WT Y181C Y188C
K103N Y181C Y188C
K103N Y181C
K103N Y181C K103N
K103N V106A Y181C K103N
WT, No NVPRmutations detected.
AIDS 2001, Vol 15 No 151954
of NVPRmutations detected in the mother and infant
was different.
NVPRin late-infected infants and their mothers
In HIVNET 012, 98% of women breastfed their
infants. Because of the potential for HIV-1 transmission
by breastfeeding, infants who tested negative for HIV-1
infection at 6±8 weeks of age were followed for 18
months for evidence of late HIV-1 infection. Nine
infants were diagnosed with HIV-1 at later time points.
In addition, three infants who were not tested at 6±8
weeks of age, but who tested negative at birth, were
diagnosed with HIV-1 at later times (Table 4). The
median age of HIV-1 diagnosis in those 12 infants was
301 days (10 months; range, 77±550 days).
Samples collected 6±8 weeks after delivery were avail-
able from nine out of 12 of the mothers of the late-
infected infants. NVPRmutations were detected in
three of those women (Table 4). Samples collected
from those women at later time points were not
available for analysis.
Samples collected after the diagnosis of HIV-1 infection
were available from the corresponding nine late-
infected infants. The age at diagnosis and at the time of
subsequent resistance testing for each infant are shown
in Table 4. Samples from eight out of nine infants
lacked detectable NVP-resistance mutations. This in-
cluded two out of three infants whose mothers had
NVPRmutations detected 6± 8 weeks after delivery.
Only one out of nine infants had NVPRmutations
detected following diagnosis of HIV-1 infection. That
infant's mother had a mixture of codons AAA (K,
lysine) and AAC (N, asparagine) at position 103, as
well as the mutation Y181C detected 6±8 weeks post-
partum. The infant tested negative for HIV-1 infection
at 6±8 weeks, but tested positive for HIV-1 infection
at day 367 (approximately 12 months of age). Samples
from the infant at 15 months and 18 months of age
both had the K103N mutation. Interestingly, both
follow-up samples from the infant had an unusual
mixture of codons at position 103: AAC and AGC (S,
serine). The Y181C mutation was not detected in
either of the infant's follow-up samples.
Discussion
We detected NVP-resistant HIV-1 6±8 weeks after
delivery in 19% of 111 women tested who received
single dose NVP in HIVNET 012. Several factors may
have contributed to the selection of NVP-resistant
HIV-1 in this setting. These include the high potency
and long half-life of NVP in pregnant women during
labor (median t1=261.3 h) [6,8], the ability of a single
mutation (K103N or Y181C) to cause high level
NVPR, and the probability that minor HIV-1 variants
with those mutations are likely to be present at low
background levels in most infected women prior to
NVP administration [4,9]. We found that the K103N
mutation was selected more frequently than Y181C in
women following single dose NVP. This is consistent
with early detection of K103N in patients receiving
chronic NVP therapy [10]. Early emergence of variants
with K103N may re¯ect a ®tness advantage of those
variants compared to variants with Y181C. With in-
creased NVP exposure, Y181C variants with higher
levels of phenotypic NVPRwould be expected to
emerge.
Frequent emergence of NVPRamong women in
HIVNET 012 may in part re¯ect their advanced stage
of HIV-1 disease. At study entry, women analyzed in
this report had relatively high viral loads (median,
40 067 copies/ml) and relatively low CD4 cell counts
(median, 412 3106cells/ìl). Both of those factors
were associated with development of NVPRin this
cohort. Therefore, the rate of NVPRfollowing single
Table 4 Analysis of NVPRmutations in late-infected infants and their mothers.
Mutations detected in
women 6± 8 weeks after
delivery
Age of infants at
diagnosis of HIV-1
infection
Age of infants
at time of
sample collection
Mutations
detected in
infants
WT 7± 8 monthsa9 months WT
WT 3± 4 monthsa8 months WT
WT 2± 3 monthsa6 months WT
WT 12± 13 months 18 months WT
WT 12 months 15 months WT
WT 3± 4 months 6 months WT
K103N G190A 3± 4 months 12 months WT
K103N 12± 13 months 13 months WT
K103N Y181C 12± 13 months 15 months K103N
18 months K103N
aThese three infants tested negative for HIV-1 infection at birth; one of these infants also tested
negative for HIV-1 infection at day 7. Because of missed clinic visits, none of these infants was
tested again until the age at diagnosis (shown). Infection of these three infants prior to 6±8
weeks of age cannot be excluded. WT, No NVPRmutations detected.
NVP resistance in HIVNET 012 Eshleman et al. 1955
dose NVP prophylaxis may be lower in cohorts with
less advanced HIV-1 disease. In the USA, NVP
prophylaxis is one of the recommended options for
prevention of HIV-1 MTCT in women in labor who
have not received antiretroviral therapy during preg-
nancy [11]. Initiation of fully suppressive, highly active
antiretroviral therapy in such women during the
immediate postnatal period would probably reduce the
risk that NVP-resistant HIV-1 would emerge.
In the HIVNET 012 cohort, NVP-resistant HIV-1
faded from detection in women over time. HIV-1
variants with NVPRmutations may continue to circu-
late in these women as minor variants, and be
maintained as provirus in infected cells. However,
replacement of the major HIV-1 population with
NVP-sensitive HIV-1 makes it less likely that NVP-
resistant HIV-1 would be transmitted from women to
other adults. Furthermore, our inability to detect
NVP-resistant HIV-1 12±24 months after delivery
suggests that the single dose NVP prophylaxis regimen
would remain effective for interruption of intrapartum
transmission in subsequent pregnancies. This is because
most of the HIV-1 population would be sensitive to
NVP at the time of labor, when NVP is administered,
and would be effectively inhibited during labor and
delivery, when HIV-1 transmission is most likely to
occur. This requires con®rmation. In contrast, persis-
tence of minor variants or proviruses with NVPR
mutations could potentially limit the use of NVP or
other non-nucleoside RT inhibitors for subsequent
treatment of HIV-1 infection. In developing countries,
where the NVP prophylactic regimen is most likely to
be implemented, current treatment options for HIV-1
infection are extremely limited. If treatment options in
those countries were widely expanded in the future,
women with NVP-resistant HIV-1 could be offered
alternative treatment regimens with other antiretroviral
drugs.
We found no association between post-partum selec-
tion of NVP-resistant HIV-1 in women and the risk of
MTCT with the ®rst use of NVP prophylaxis. We also
found little evidence for transmission of NVP-resistant
HIV-1 variants from women to infants who were
infected by 6±8 weeks of age. The risk of transmission
of NVP-resistant HIV-1 variants through breastfeeding
requires further evaluation. The kinetics of the emer-
gence and fading of NVP-resistant HIV-1 in women
receiving single dose NVP has not been de®ned, and
the duration NVP-resistant HIV-1 persists in the
mother will affect the risk of late postnatal transmission
of resistant virus. Of the nine late-infected infants in
this study, only three had mothers with NVPRdetected
at 6±8 weeks postpartum. Of those, two infants were
infected with NVP-sensitive HIV-1 and one was
infected with NVP-resistant HIV-1. Additionally, 11
women with NVP-resistant HIV-1 had uninfected
infants and did not transmit HIV-1 despite breastfeed-
ing. However, because evaluation of NVPRin infants
in HIVNET 012 was possible only using follow-up
samples collected months after the diagnosis of HIV-1
infection for most infants, it is possible that additional
NVP-resistant strains were transmitted to infants by
breastfeeding, but that those variants faded from detec-
tion before follow-up samples were collected.
Our data suggest that NVP-resistant HIV-1 is selected
independently in infants after NVP administration. The
relatively high rate of NVPRobserved among infants in
HIVNET 012 could re¯ect the high viral loads typi-
cally present in HIV-1 infected infants. Increased
exposure to NVP in infants compared to their mothers
may also favor emergence of NVP-resistant HIV-1.
Infants in HIVNET 012 were essentially dosed twice:
once by the placental transfer of maternally admin-
istered NVP, and once within 48±72 h of birth. The
half-life of NVP in infants is long (median t1=2
46.5 h) [6,8]. When pregnant women and infants
received the same regimen used in HIVNET 012, the
NVP concentration in infants was .100 ng/ml (.10
times the 50% inhibitory concentration of the drug) for
7 days [6,8]. The greater NVP exposure of infants
versus women in HIVNET 012 may also explain the
more frequent detection of the Y181C mutation
(rather than K103N) in infants. The fading of NVP-
resistant HIV-1 that we observed in infants paralleled
that observed in women post-partum, and was consis-
tent with reduced ®tness of HIV-1 with NVPRmuta-
tions in the absence of the drug.
The ®ndings of this report emphasize the importance
of evaluating the development of drug resistance
among women receiving short-course antiretroviral
prophylaxis regimens, particularly for prophylaxis regi-
mens using antiretroviral drugs in which a single
mutation can confer resistance, such as NVP or
lamivudine. Such evaluations should include: (i) further
characterization of the kinetics of the emergence and
fading of NVPRin women receiving single dose NVP
prophylaxis; (ii) assessment of whether there is a risk
for transmission of NVP-resistant virus to infants post-
natally through breastfeeding or to sexual partners and
the magnitude of that risk; and (iii) assessment of the
association of NVPRwith disease progression. Such
monitoring should be planned within future perinatal
trials, as well as within the context of implementation
efforts. Epidemiologic studies could also be considered
to evaluate the effectiveness of the single dose NVP
regimen in future pregnancies.
The potential for selection of NVP-resistant HIV-1 in
women and infants receiving single dose NVP prophy-
laxis must be balanced against the documented ef®cacy,
simplicity, and cost-effectiveness of the HIVNET 012
regimen. This regimen can signi®cantly reduce HIV-1
AIDS 2001, Vol 15 No 151956
MTCT in settings where other prophylactic regimens
are impractical and treatment options are extremely
limited. If implemented rapidly, this regimen can
prevent HIV-1 infection in millions of HIV-1 exposed
infants over the next decade.
Acknowledgements
Reagents for HIV genotyping were provided by
Applied Biosystems (Foster City, CA). The authors
acknowledge the assistance of M. Allen (Protocol
Specialist, Family Health International). The authors
thank E. Piwowar-Manning, C. Ducar, and the labora-
tory staff in Uganda for assistance with sample proces-
sing. The authors also thank E. Shulse and the Applied
Biosystems Genotyping Team for helpful discussions
and for providing reagents used in this study. The
authors thank D. Richman (UCSD) and C. Petropou-
los (ViroLogic) for helpful discussions.
Sponsorship: Supported by: (i) the Elizabeth Glaser Pedi-
atric AIDS Foundation; (ii) the HIV Network for Preven-
tion Trials (HIVNET) and sponsored by the US National
Institute of Allergy and Infectious Diseases (NIAID),
National Institutes of Health (NIH), Department of Health
and Human Services (DHHS), through contract N01-AI-
35173 with Family Health International, contract N01-
AI-45200 with Fred Hutchinson Cancer Research Center,
and subcontracts with JHU/Makerere Univ. (NOI-AI-
35173-417); (iii) the HIV Prevention Trials Network
(HPTN) sponsored by the NIAID, National Institutes of
Child Health and Human Development (NICH/HD),
National Institute on Drug Abuse, National Institute of
Mental Health, and Of®ce of AIDS Research, of the NIH,
DHHS (U01-AI-46745 and U01-AI-48054); (iv) the Pedi-
atric and Adult AIDS Clinical Trials Groups (NIH, Divi-
sion of AIDS, NIAID); and (v) R29 34348 (NIH, Division
of CH/HD).
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