Download Active or Prior GB Virus C Infection Does Not Protect against Vertical

BRIEF REPORT
Active or Prior GB Virus C Infection
Does Not Protect against Vertical
Transmission of HIV in Coinfected
Women from Tanzania
Amy C. Weintrob,1 John D. Hamilton,1,2 Christine Hahn,1
Donna Klinzman,3 Gustav Moyo,4 Dietmar Zdunek,5 Georg Hess,6
Daniel K. Benjamin, Jr.,1 and Jack T. Stapleton3
Duke University Medical Center and 2Research Service, Veterans Affairs
Medical Center, Durham, North Carolina; 3University of Iowa and Iowa Veterans
Affairs Medical Center, Iowa City, Iowa; 4Tanzania Ministry of Health, Dares-Salaam, Tanzania; and 5Roche Laboratories, Penzberg, and 6Roche
Diagnostics, Mannheim, Germany
1
To determine whether GB virus C (GBV-C) infection is associated with protection against vertical transmission of human immunodeficiency virus (HIV), we tested 186 HIVpositive pregnant women for GBV-C. Neither active nor prior
GBV-C infection was associated with a lower rate of HIV
acquisition among infants. Thus, GBV-C does not appear to
protect against perinatal HIV acquisition.
GB virus C (GBV-C) is a flavivirus that is closely related to
hepatitis C virus; however, it does not replicate in hepatocytes
and has not been associated with any specific disease (reviewed
in [1]). GBV-C viremia can persist for decades without apparent
illness, or the virus may be cleared with the formation of antibodies to envelope glycoprotein E2 [2, 3]. Recent studies
found that coinfection with GBV-C in HIV-infected patients
was associated with an increase in the duration of survival,
independent of HIV treatment received, baseline CD4+ T lymphocyte count, age, sex, race, and mode of transmission (reviewed in [4]). GBV-C viremia was also shown to slow the
Received 2 September 2003; accepted 16 November 2003; electronically published 1 March
2004.
Financial support: Veterans Administration (merit review to J.T.S.), National Institutes of
Health (grants AI 50478, AI 058740, and AI 27661 to J.T.S.), and National Institute of Child
Health and Human Development (grant R03HD42940-01 to D.K.B.).
Conflict of interest: G.H. and D.Z. are employees of Roche Diagnostics and Roche
Laboratories, respectively, and produce the E2 antibody ELISA method used in this study.
Presented in part: 43rd Interscience Conference on Antimicrobial Agents and Chemotherapy,
Chicago, Illinois, 14–17 September 2003 (abstract H1722).
Reprints or correspondence: Dr. Amy Weintrob, Duke University Medical Center, Box 3824,
Durham, NC 27710 ([email protected]).
Clinical Infectious Diseases 2004; 38:e46–8
2004 by the Infectious Diseases Society of America. All rights reserved.
1058-4838/2004/3806-00E2$15.00
e46 • CID 2004:38 (15 March) • BRIEF REPORT
progression to AIDS in patients with coinfection. GBV-C replicates in CD4+ T lymphocytes in vitro [5], and coinfection of
PBMCs with GBV-C and HIV has resulted in decreased HIV
replication [6]. Although the mechanism of interaction between
GBV-C and HIV is not completely understood, there is some
evidence that GBV-C replication alters chemokine expression,
which may contribute to the inhibition of HIV replication [7].
The prevalence of GBV-C viremia among blood donors is
1%–2% in the United States and up to 4% in some developed
countries [1]. Among HIV-infected individuals, the prevalence
of GBV-C viremia may be as high as 40% [8]. Parenteral transmission of GBV-C is well recognized, and recent studies suggest
that sexual transmission occurs frequently as well [9]. Several
studies have found a high rate of vertical transmission of GBVC (60%–80%) from viremic mothers [10, 11], and small studies
have evaluated whether coinfection with HIV affects the vertical
transmission of GBV-C. In one of these studies [10], 34 mothers
with detectable GBV-C RNA levels were evaluated. Eight of
these women were HIV positive. There was not a statistically
significant difference in the rate of vertical transmission of
GBV-C between babies who were born to mothers with HIV
coinfection (50%) and those who were born to mothers without
HIV infection (65%). Another study evaluated vertical transmission of GBV-C in HIV/GBV-C–coinfected women and
found a rate of vertical transmission of GBV-C of 45%, which
is similar to the rate seen in women without HIV infection
[11]. The effect of maternal GBV-C viremia on the vertical
transmission of HIV, however, remains unknown. Thus, we
evaluated the effects of GBV-C infection on the vertical transmission of HIV using archived plasma samples obtained from
HIV-positive women in Dar-es-Salaam, Tanzania, from 1992
through 1993.
Methods. This was a retrospective cohort study using archived serum samples obtained for a study on the vertical transmission of HIV during the period of 1992–1993. The institutional review boards at Duke University (Durham, NC) and
the University of Iowa (Iowa City, IA) approved the study.
Women attending an antenatal clinic in Dar-es-Salaam, Tanzania, were addressed by a Swahili-speaking nurse and invited
to participate in screening for the HIV vertical transmission
study. Consenting women were interviewed privately to reconfirm their consent to having an HIV test performed, and they
subsequently were tested for HIV by ELISA. Blood samples
were stored at ⫺20C. Women who tested positive for HIV
infection twice by ELISA were enrolled if they consented to
continue with the study. Blood samples were obtained from
their infants at birth and 6 weeks, 3 months, 6 months, 9
months, 12 months, 15 months, and 18 months after birth for
determination of HIV RNA levels by RT-PCR. None of the
study subjects received antiretroviral therapy.
All serum samples were identified by a unique code, and
laboratory personnel were blinded to clinical data. RNA was
extracted from 200 mL of serum using a previously described
guanidinium-isothiocyanate extraction method [6]. Onefourth of this RNA preparation was used in nested RT-PCR
reactions to amplify GBV-C RNA using primers from the E2
coding region of the genome. Specifically, primers were as follows: outer sense, 5-GDC GYG AYT CGA ARA TMG AYG-3
(nt 1484–1505); outer antisense, 5-AAG ATC AAC GGG ACC
AGC CGT GCC TCA-3 (nt 2229–2251); inner sense, 5-GAT
ATC GAA RAT MGA YGT GTG GAG-3 (nt 1490–1512); inner
antisense, 5-TTA GGT ACC GCC TCA GCC AGC TTC AT3 (nt 2219–2235) (sequence numbering based on the fulllength Iowa GBV-C isolate; GenBank accession no. AF121950
[5]). Reaction conditions and the protocol for PCR product
identification were described elsewhere [6]. Negative and positive controls were included with each sample undergoing PCR
testing. The presence of antibodies to GBV-C envelope glycoprotein E2 was determined by ELISA [12], using the mPlate
anti-HGenv test (Roche Diagnostics).
Statistical analyses were completed using Stata software, version 6.0/7.0 (Stata). Binomial 95% CIs were calculated using
exact methods, when appropriate. P values are 2-tailed and
were estimated using the Wilcoxon rank sum test.
Results. Two thousand three hundred twenty-nine women
were screened, and 320 (13.8%) were found to have antibodies
to HIV. Of these women, 215 HIV-positive women enrolled in
the study and had 131 live births. Of the 215 HIV-infected
women enrolled in the vertical transmission study in Tanzania,
186 had serum samples available for GBV-C testing. All but 1
of the infants in this study were delivered vaginally. Ninetyeight (53%) of the 186 women had evidence of past or active
GBV-C infection. Forty-four women (24%; 95% CI, 18%–30%)
had detectable GBV-C RNA, and 54 (29%; 95% CI, 24%–37%)
had anti-E2 antibodies. Two patients had both GBV-RNA and
anti-E2 antibodies.
The rate of vertical transmission of HIV according to GBVC status is shown in figure 1. HIV-positive women with GBVC viremia transmitted HIV to 25 (28%; 95% CI, 12%–49%)
of their infants, compared with 26 (23%; 95% CI, 9%–44%)
of the infants from women with anti-E2 antibody and 77 (26%;
95% CI, 17%–37%) of the infants from women without active
or past GBV-C infection. There was no statistically significant
difference in the rates of vertical transmission of HIV.
Discussion. GBV-C viremia has been shown to be associated with an increase in the duration of survival among HIVinfected individuals, independent of HIV treatment, baseline
CD4+ T lymphocyte count, age, sex, race, and mode of transmission (reviewed in [4]). Although the interactions between
GBV-C and HIV are incompletely understood, there is evidence
that GBV-C replication inhibits HIV replication [6, 7]. We studied the prevalence of GBV-C infection and the effects of coinfection with GBV-C on the vertical transmission of HIV in
Tanzanian women who did not have access to antiretroviral
therapy.
The prevalence of GBV-C viremia in HIV-infected, pregnant Tanzanian women was 24%, and an additional 30% had
detectable antibodies to envelope protein E2, indicating past
GBV-C infection and clearance. Similar to previous studies
[8], the prevalence of GBV-C viremia in HIV-infected women
Figure 1. Rate of vertical transmission of HIV, according to the hepatitis GB virus C (GBV-C) status of the mother. P p .60 , for women with GBVC viremia versus those without GBV-C infection. P 1 .99 , for women with GBV-C antibodies versus those without GBV-C infection. +, Positive; ⫺,
negative.
BRIEF REPORT • CID 2004:38 (15 March) • e47
was significantly greater than the prevalence of GBV-C reported in the general population. However, the prevalence of
GBV-C viremia in this study was lower than that seen in some
HIV-infected cohorts. For example, a study of 362 HIVinfected individuals from the midwestern United States found
a prevalence of GBV-C viremia of 40%, regardless of risk
factors for HIV infection [6], and a retrospective evaluation
of samples obtained from 271 HIV-infected individuals in the
Multicenter AIDS Cohort Study (MACS) found a prevalence
of GBV-C viremia of 39% [12].
We assume that the vast majority of HIV infections in Tanzania were transmitted sexually. GBV-C has been shown to be
transmitted sexually as well as parenterally [10, 11]; therefore,
this probably does not account for the difference in prevalence.
All of the samples in this study were obtained in the same
manner and frozen until use, so there should not have been
technical difficulty in detecting GBV-C RNA in the samples.
The lower overall rate of viremia and E2 antibody positivity
may reflect an increased rate of clearance of GBV-C RNA without development of E2 antibody in HIV-positive individuals.
In the MACS cohort, for example, 12 of 61 participants who
were GBV-C RNA positive within 18 months of HIV seroconversion cleared their GBV-C viremia during 4–5 years of followup. Seventy-five percent of these patients did not develop E2
antibody, and these patients were 5.87 times more likely to die
than were those who were persistently viremic [12]. Another
factor that may contribute to the difference in the prevalence
of GBV-C viremia seen in this cohort is that, presumably, the
Tanzanian women had non–clade B HIV and either GBV-C
genotype 1 or 5. It is unknown how either HIV or GBV-C
diversity might affect the detection of GBV-C infection or the
interaction between GBV-C and HIV. Thus, this study may not
be applicable to all HIV-positive pregnant women.
Previous studies found a high rate (45%–80%) of vertical
transmission of GBV-C, but none of these studies evaluated
the effects of coinfection with GBV-C on the vertical transmission of HIV. In this cohort, neither maternal GBV-C viremia
nor E2 antibody was associated with a high level of protection
against vertical HIV transmission. However, because of the relatively small number of subjects with an adequate volume of
serum available for evaluation of GBV-C RNA or anti-E2 antibodies, this study did not have sufficient power to detect small
differences in HIV transmission rates. With 51 coinfected
women and 77 women with HIV infection alone, as well as a
baseline rate of vertical transmission rate of 26%, then (with
an a of 5% and using Fisher’s exact methods, given the small
e48 • CID 2004:38 (15 March) • BRIEF REPORT
sample size) the study had 80% power to detect an absolute
difference of 20%. Nevertheless, these data do not support a
protective effect of GBV-C infection on vertical transmission
of HIV in Tanzanian women. The possible effect of vertical
transmission of both HIV and GBV-C on long-term infant
survival is currently under study.
Acknowledgments
We would like to thank the women in Tanzania who consented to the study and Stephanie O’Conner for assistance with
the GBV-C testing logistics.
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