SIVHIVspecific immune responses and virus evolution in breast milk

1
SIV/HIV-specific immune responses and virus
evolution in breast milk
Sallie Permar, MD, PhD Beth Israel Deaconess
Medical Center Childrens Hospital, Boston New
England Regional Primate Center
2
HIV transmission via breastfeeding

• 350,000 infant HIV infections yearly
• 1/3-1/2 are breast milk transmissions
• Formula feeding associated with higher mortality
• 10 HIV-infected mothers transmit the virus
  during breastfeeding
• High breast milk virus load
• Low maternal CD4 count
• Effect of immunologic milieu in breast milk on
  breast milk virus load and virus transmission is
  unknown

3
Rhesus monkey/SIV model to study HIV/SIV immunity
in breast milk

• MHC types and immunodominant immune responses
  well characterized
• Genetically well defined viral stock
• Ease of frequent sampling
• SIV-specific CD8 T lymphocytes and antibody
  response detectable in breast milk
• Calculate absolute numbers of lymphocytes in a
  mucosal compartment

4
Hormone-induction of lactation in rhesus monkeys

• Artificially induced lactation to avoid reliance
  on breeder monkeys
• Mammary gland maturation with estradiol and
  medroxyprogesterone injections
• Oral dopamine antagonist to raise serum prolactin
• Oxytocin at time of collection
• Lymphocyte phenotype and antibody subclass
  concentration similar between hormone-induced
  lactation and natural lactation breast milk

5
SIV infection of lactating rhesus monkeys

• Robust SIV-specific CD8 T lymphocyte response
  identified in breast milk
• Associated with low breast milk virus load

6
SIV-specific CD8 T lymphocyte response is 2-3
times higher in breast milk than blood during
acute infection
7
Breast milk viral load is 1-2 logs lower than
plasma viral load during acute SIV-infection
plasma
breast milk
9
206
8
257
402
7
403
log copies/ml
6
5
4
10
20
30
40
50
60
70
10
20
30
40
50
60
70
days
8
SIV infection of lactating rhesus monkeys

• Robust SIV/HIV-specific CD8 T lymphocyte
  response identified in breast milk
• Associated with low breast milk virus load
• Evidence of local production of breast milk virus

9
SIV envelope sequencing in breast milk and plasma
during chronic infection
10
SIV infection of lactating rhesus monkeys

• Robust SIV/HIV-specific CD8 T lymphocyte
  response identified in breast milk
• Associated with low breast milk virus load
• Evidence of local production of breast milk virus
• High proportion of nearly identical viruses in
  milk
• CTL escape of breast milk virus

11
Rate of Gag p11C CTL escape similar in milk and
blood virus
blood
milk
206
257
100
100
80
80
60
60
Percent wild type
40
40
20
20
10
20
30
40
10
20
30
40
402
403
100
100
80
80
60
60
Percent wild type
40
40
20
20
10
20
30
40
10
20
30
40
weeks after infection
12
SIV infection of lactating rhesus monkeys

• Robust SIV/HIV-specific CD8 T lymphocyte
  response identified in breast milk
• - Associated with low breast milk virus
  load
• Evidence of local production of breast milk
  SIV/HIV
• Groups of nearly identical viruses in milk
• CTL escape of breast milk virus
• Therefore, local breast milk immune responses
  may contribute to control virus replication in
  breast milk

13
SIV vaccination of lactating rhesus monkeys

• Important Questions
• Can maternal vaccination enhance virus-specific
  immune responses in breast milk?
• Can vaccine-elicited immune responses enhance
  control of local breast milk virus replication?

14
Maternal vaccination to reduce breast milk
transmission of HIV

• Low rate of HIV transmission via breast milk
  despite maternal antiretroviral treatment
• Maternal vaccine may complement antiretroviral
  prophylaxis during breastfeeding
• Enhancement of virus-specific cellular immune
  responses in breast milk may contribute to
  control of milk virus replication

15
SIV vaccination of lactating rhesus monkeys

• Many prototype SIV vaccines can reduce peak and
  set point virus load after challenge
• Systemic vaccination induces mucosal cellular
  immune responses
• Vaccine-elicited cellular immune responses in
  breast milk have not been studied

16
Vaccination of lactating rhesus monkeys

• Well-studied SIV DNA prime-pox vector boost
  vaccination strategy
• IM vaccination of 5 uninfected, hormone-induced
  lactating rhesus monkeys
• 5 µg of rDNA plasmid SIV gag-pol and SIV env x 3
  (0, 4, and 8 weeks)
• Planned boost with NYVAC containing SIV gag-pol
  and SIV env (30 weeks)
• Monitor phenotype of lymphocytes in breast milk
  after vaccination by flow cytometry
• Measurement of SIV-specific CD8 T lymphocytes
  with Gag p11C and ENV p54-specific tetramers

17
Vaccine-elicited Gag-specific CD8 T lymphocyte
responses detectable in breast milk after DNA
prime
Breast Milk
Blood
458
402
1.6
294
234
1.2
percent
74
.8
.4
Gag p11C-specific CD8 T lymphocytes
6
5
log absolute count/ml
4
3
2
DNA vaccination
2
4
6
8
10
12
2
4
6
8
10
12
weeks
18
Conclusions

• Local SIV-specific CD8 T lymphocyte responses in
  milk may control local virus replication
• Robust CD8 T lymphocyte response in milk
• Evidence of local production of breast milk virus
• CTL escape of breast milk virus
• Vaccine-elicited SIV-specific cellular immune
  responses appear in breast milk after systemic
  DNA vaccination

19
Future plans

• Monitoring lymphocyte phenotype and SIV-specific
  CD8 T lymphocytes in breast milk after live pox
  vector systemic boost (NYVAC)
• Vaccination of chronically SIV-infected,
  lactating rhesus monkeys
• Monitoring of vaccine-elicited immune responses
  and SIV virus load in breast milk after
  systemic/mucosal vaccination
• Define HIV-specific cellular and humoral immune
  responses in transmitting and nontransmitting
  mothers (IMPAACT PROMISE study)

20
Acknowledgements

• Beth Israel Deaconess Medical Center
• Andrew Wilks
• Helen Kang
• Linh Mach
• Tatenda Mahlokozera
• Liz Ehlinger
• Norman Letvin
• New England Regional Primate Center
• Angela Carville
• Keith Mansfield

• Vaccine Research Center, NIH
• Gary Nabel
• Judy Stein
• EuroVac
• Gepi Pantaleo
• Song Ding
• IMPAACT
• Betsy McFarland
• Coleen Cunningham