Maternal Neutralizing Antibodies to a CRF01_AE Primary Isolate are Associated with Low Intrapartum T

1
Maternal Neutralizing Antibodies to a CRF01_AE
Primary Isolate are Associated with Low
Intrapartum Transmission of HIV-1 in Thailand
T Samleerat1,2, G Jourdain3,4,5, M Braibant1, N
Ngo-Giang-Huong3,4,5, P Leechanachai2, S
Sirithadthamrong3, V Surasaerneewongse3, B
Warachit3, S Hotrawarikarn3, M Lallemant3,4,5,
and F Barin1 1.INSERM ERI19, Université
François Rabelais, Tours, France
2.Faculty of Associated Medical Sciences, Chiang
Mai University, Thailand 3.Harvard
School of Public Health, Boston, MA
4.Institut de Recherche pour le Développement
(IRD), URI 174, Chiang Mai, Thailand
5.Programs for HIV Prevention and Treatment
(PHPT), Chiang Mai, Thailand
MOAA0205
2
Background

• Mother-to-child transmission (MTCT) of
  HIV can occur during pregnancy (in
  utero), during labor and delivery (intrapartum),
  or after birth through breastfeeding.
• Rate of MTCT without any intervention 15-30.

3
Background

• Maternal neutralizing Abs (NAbs) are considered
  to be important in protecting the infant from
  infection by numerous pathogens.
• Maternal Abs can pass the placental barrier to
  the fetus in utero, reaching the highest
  levels at delivery.

4
Background

• Conflicting results regarding the role of
  maternal NAbs have been obtained in the field of
  MTCT of HIV.
• In particular, most previous studies did not take
  into clearly account the timing of transmission
  (in utero and intrapartum).

5
Background

• Recent molecular have studies suggested that
  intrapartum transmitted viruses are escape
  variants resistant to maternal autologous NAbs
  (Dickover et al., JVI 2001 752194-203 Wu et
  al., JVI 2006 80835-44 Dickover et al., JVI
  2006 806525-33).

6
Background

• We previously determined the NAbs titers against
  primary isolates of various clades in serum
  samples from Thai pregnant women for whom the
  time of transmission was known (Barin et al., JID
  2006 1931504-11).
• We found an association between higher titers of
  NAbs against a CRF01_AE primary isolate (MBA) and
  a lower rate of intrapartum transmission.

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Objective

• To investigate further the relationship between
  NAbs and MTCT of HIV in Thai pregnant women.

8
Study population

• HIV-1 infected pregnant women enrolled in a
  clinical trial assessing various zidovudine
  treatment durations for the prevention of MTCT in
  Thailand (PHPT-1 Lallemant et al., NEJM 2000,
  343 982-91).
• Infants were not breastfed.
• HIV-1 infection status of infants was determined
  by HIV-1 proviral DNA PCR (Roche monitor 1.5).

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Study population

• 45 transmitting mothers (cases) were matched to
  45 non-transmitting mothers (controls) on
• baseline viral load
• duration of zidovudine prophylaxis
• Of 45 transmitting mothers
• 14 transmitted in utero
• 29 transmitted intrapartum
• 2 not determined.

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Study population
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HIV-1 Subtyping

• Maternal viruses were subtyped using both V3
  serotyping assay and sequencing of gp41 region.
• Of 90 samples, 80 (89) were identified as
  CRF01_AE, 4 (4) were identified as subtype B,
  and 6 (7) were defined as indeterminate.

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MethodsExperiment 1

• NAbs titers were determined using P4P cells
  (CD4CXCR4CCR5 HeLa cells harboring the lacZ
  gene) assay (Barin et al., JID 2004, 189322-7).
• Heterologous primary isolates
• FRO B,X4
• BIG B,R5
• CHA B,R5X4
• C1712 CRF01_AE, X4
• LEA CRF01_AE, R5
• MBA CRF01_AE, R5X4

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MethodsExperiment 1

• Neutralization titer was defined as the dilution
  of serum that resulted in a 90 decrease of
  infected cells 2 days after infection with 100
  TCID50.
• Blood samples were collected before initiation of
  ZDV prophylaxis.

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Results
Comparison of detectable NAbs against the 6
primary isolates between transmitting and
non-transmitting mothers
15
Comparison of NAbs titers against the 6 primary
isolates between transmitting and
non-transmitting mothers
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Comparison of NAbs titers to MBA strain in
non-transmitting, in utero and intrapartum
transmitting mothers
P0.04
P1.00
40
30
Neutralizing antibody titers to MBA
20
10
0
NT
In utero
Intrapartum
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SummaryExperiment 1

• There was an association between high titers of
  maternal NAbs against MBA and a lower rate of
  MTCT of HIV (Plt0.01) in this population, in
  particular for intrapartum transmission (P0.04).

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SummaryExperiment 1

• Some passively-transferred NAbs should be able to
  neutralize variants present in the mothers.
• Only strains with specific properties such as MBA
  might be indicators for protection.

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MethodsExperiment 2

• The env gene from the CRF01_AE viruses was
  directly sequenced.
• The N-linked glycosylation sites were identified
  by submitting to N-Glycosite (HIV Sequence
  Database https//hiv.lanl.gov/content/hiv-db/GLYC
  OSITE/glycosite.html).
• (Nucleotide sequences have been submitted to
  the GenBank with accession numbers DQ518410,
  DQ518411, DQ518412.)

20
01 AE.FI.93.FIN9379
01 AE.TH.01.OUR702I
01 AE.FR.96.PHI426
01 AE.US.x.98US MSC1100
01 AE.TH.97.97TH6 107
01 AE.US.x.98US MSC1120
01 AE.TH.00.OUR810I
01 AE.TH.99.OUR422I
90
01 AE.TH.00.OUR746I
01 AE.US.x.98US MSC3012
C1712 (DQ518410)
01 AE.JP.93.93JP NH1
01 AE.TH.96.NI1157
01 AE.TH.98.98TH NP1251
Phylogenetic tree of HIV-1 strains based on env
gene
01 AE.CN.97.97CNGX2F
55
MBA (DQ518412)
01 AE.TH.99.OUR199I
01 AE.US.x.00US MSC1164
01 AE.TH.99.99TH NI1052
01 AE.TH.96.96TH M02138
54
01 AE.HK.x.HK001
01 AE.TH.00.OUR661I
CRF01_AE
52
01 AE.TH.00.OUR724I
01 AE.TH.97.97TH NP1695
01 AE.TH.97.97TH NP1525
01 AE.TH.01.OUR414I
01 AE.TH.96.96TH NP1046
01 AE.TH.01.OUR786I
100
01 AE.TH.01.OUR674I
01 AE.TH.00.OUR721I
01 AE.TH.96.NI1154
01 AE.TH.01.OUR830I
01 AE.TH.02.OUR737I
100
01 AE.TH.02.OUR769I
01 AE.TH.99.OUR044I
01 AE.TH.96.NI1155
01 AE.TH.01.OUR609I
01 AE.TH.01.OUR647I
01 AE.TH.99.OUR164I
77
01 AE.TH.99.OUR066I
100
01 AE.TH.99.OUR008I
57
01 AE.TH.01.OUR642I
01 AE.CF.90.90CF11697
100
68
01 AE.US.x.98US MSC2008
01 AE.CM.93.CA10
LEA (DQ518411)
B
55
52
B.FR.83.HXB2-LAI-IIIB-BRU
D
D.UG.94.U88824
A
A1.SE.94.AF069670
Group O
O.CM.91.L20571
0.05
21
Results
Alignment of the amino acid sequences of V3
region of gp120 (N-lined glycosylation site
NXST)

• The substitution of N301 by other amino acid is
  associated with an increased sensitivity of HIV
  to neutralization by mAbs to the CD4 binding site
  (Koch et al., Virology 2003 313 387-400
  McCaffrey et al., JVI 2004 78 3279-95).

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Results
Alignment of the amino acid sequences of gp41
based on 2F5 and 4E10 epitopes
2F5 mAb epitope ELLELDKWASLWN
(659-671)
4E10 mAb epitope NWFDIT
(671-676)
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SummaryExperiment 2

• A potential N-linked glycosylation site, N301 was
  found in V3 region only for MBA strains.
• These sequence properties might explain how MBA
  stain are resistant to neutralize in term of
  neutralization and protection.

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Conclusion

• This study confirms that maternal NAbs to a
  CRF01_AE primary isolate (MBA) are associated
  with low intrapartum transmission of HIV-1 in
  Thailand
• Some primary isolates might be relevant
  indicators for identification of protective
  antibodies.

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