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Indian Pediatr 2014;51: 801-803 |
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Genetic Factors Associated with Slow Progression of HIV among
Perinatally-Infected Indian Children
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*Riya Pal Chaudhuri,
#Ujjwal Neogi,
$Shwetha D Rao and Anita Shet
From the Departments *Clinical Virology, #Hematology
Research Unit, Microbiology and Department of Pediatrics,
St. John’s Medical College Hospital, Bangalore, India.
Correspondence to: Dr Anita Shet, Department of
Pediatrics, St. John’s Medical College Hospital,
Bangalore 560 034, India.
Email: anitashet@stjohns.in
Received: February 20, 2014;
Initial review: April 21, 2014;
Accepted: August 04, 2014.
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Objectives: To study the
association between common AIDS restriction genes and slow disease
progression among perinatally-infected children in India.
Methods: ART-naïve
children were identified and selected host factors including CCR5-D32,
SDF1-3’A, CCR5-59029G, HLA-B*27, B*57 were studied using allele-specific
PCR-RFLP and SSPGo HLA typing kits.
Results: Among 165
children, 10 (6%) long-term non-progressors and 8 (5%) slow progressors
were identified. For comparison, 12 children with normal progression of
HIV were included. The frequencies of CCR5-D32
deletion, SDF1-3’A and CCR5-59029G did not differ significantly.
HLA-B*27 and B*57 were observed only in long-term non-progressors or
slow progressors, who also harbored either SDF1-3’A and/or CCR5-59029G.
Conclusions: There is an
association between host genetic factors and slow disease progression in
this population.
Keywords: Genetics, Human Immunodeficiency
virus, Outcome, Progression.
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The disease course of HIV is varied in
perinatally-infected children; those who succumb to terminal illnesses
soon after infection are termed as rapid-progressors. Others termed as
long-term non-progressors (LTNP) often survive up to 25 years or longer
without antiretroviral therapy (ART) [1]. This variability is related to
differences in viral biological properties, host genetics and host
immune responses [2]. Several immunoregulatory genes – AIDS restriction
genes (ARGs) - play a pivotal role in entry of the virus into the host
cell [2]. Mutations in these receptors or their ligands, have been
associated with natural resistance to HIV-1 and delayed progression of
HIV-1 disease [3]. Two HLA-class I alleles, HLA-B*27 and HLA-B*57 have
been associated with slower HIV-1 disease progression in adults [4].
Most studies assessing the role of host genetic factors in LTNPs have
been carried out on Caucasian or African populations; studies in India
are limited [5-7].
Our study aimed at correlating five commonly reported
ARGs, CCR5-D32,
SDF1-3’A, CCR5-59029G, HLA- B*57 and B*27, with disease progression
among perinatally-infected Indian children.
Methods
The study participants were selected from a cohort of
165 children living with perinatally-acquired HIV-1 infection obtaining
care at the Pediatric Infectious Disease Clinic, St. John’s Hospital,
Bangalore. Written informed consent was obtained from the caregivers,
and verbal assent was obtained from children
³8 years of age. The
study was approved by the Institutional Ethical Review Board at St.
John’s Medical College Hospital, Bangalore. Perinatal acquisition of HIV
was confirmed by history and documentation of maternal HIV-positive
status, and absence of other risk factors of HIV infection acquisition
in the child. The following definition was used to screen for LTNPs:
ART-naïve, asymptomatic, HIV-1 infection for >10 years, and CD4 T-cell
count >500 cells/mm3. Slow
progressors (SP) were defined as children who were ART-naïve,
asymptomatic, with known HIV-1 infection for >10 years, and CD4
count<500 cells/mm3 [1].
Normal progressors (NP) constituted those children who had HIV-1
infection for less than 10 years with CD4 cell count <500 cells/mm3.
The time of onset of HIV infection was considered as the date of birth
of the child, and the length of infection was the same as child’s age.
Clinical features and CD4 counts were documented for this study, and
viral load was performed using Abbott m2000RT Real Time PCR assay.
Genomic DNA was extracted from whole blood using QIAmp DNA Blood Mini
Kit (Qiagen, US). SDF1-3’A and CCR5-59029G genotypes were identified by
PCR-based restriction followed by fragment length polymorphisms
(PCR-RFLP) using MspI and BsaBI. CCR5-D32
was amplified by PCR using the primers described previously [8].
HLA-B*57 and B*27 allele polymorphisms were determined by SSPGo-HLA
Typing Kits (Biofortuna, Bromborough, UK) as per manufacturer’s
instructions.
Results
Among the 165 children who were initially screened,
we identified 6% LTNPs and 5% SPs. We also included 12 NPs, and the
final study sample consisted of 30 children (14 males). Mean (SD) CD4
absolute count was 482 (397) cells/mm3,
and mean (SD) CD4 percentage was 19% (4%). Mean (SD) viral load was 5.3
(0.7) log copies/mL. The majority of the children were asymptomatic, and
5% had minor illnesses that constituted features consistent with WHO
Clinical Stage 2 illnesses. Among the NPs, two each had previous WHO
clinical stage 3 or 4 conditions, and all were on anti-retroviral
treatment (ART).
The clinical features and allelic distribution of
ARGs among the three groups is presented in Table I. None
of the children had CCR5-D32
deletion; all had wild-type CCR5. Among the SPs and LTNPs together
(collectively called "long term survivors" (LTS)), the SDF1-3’A allele
was found either in the heterozygous or homozygous form in 44% (8/18).
Among NPs, it was found in 25% (3/12) (P=0.279), Similarly, the
CCR5-59029G allele was found in 89% (16/18) among LTS and 92% (11/12)
among NPs (P=0.804). The HLA-B*57-positive SP was also
heterozygous for SDF1-3’A and CCR5-59029G while the HLA-B*57-positive
LTNP was homozygous for SDF1-3’A and heterozygous for CCR5-59029G. The
HLA-B*27-positive LTNP was also heterozygous for CCR5-59029G.
TABLE I Clinical, Demographic and Allelic frequency of AIDS Restriction Genes Among Perinatally-infected
Children Living with HIV-1, Classified Based on Their Rate of Disease Progression
Parameter |
Normal progressors
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Slow progressors
|
Long-term non- |
|
(n=12) |
(n=8) |
progressors (n=10) |
Age; mean (SD) |
6.3 (2.6) |
12.8 (1.7) |
11.8 (2.0) |
Boys; No. (%)
|
6 (50%) |
4 (50%) |
4 (40%) |
Viral load, log copies/mL; Mean (SD)
|
5.35 (0.73) |
5.37 (0.66) |
5.11 (0.78) |
CD4 count, cells/mm3; Mean (SD) |
282 (105) |
243 (118) |
913 (415) |
SDF1-3’A prevalence, n (%)
|
Heterozygous (3’G/3’A) |
1 (8%) |
3 (38%) |
2 (20%) |
Homozygous (3’A/3’A) |
2 (17%) |
1 (13%) |
2 (20%) |
Wild Type (3’G/3’G) |
9 (75%) |
4 (50%) |
6 (60%) |
CCR5-59029G prevalence, n (%)
|
Heterozygous (G/A) |
4 (33%) |
4 (50%) |
4 (40%) |
Homozygous (G/G) |
7 (58%) |
3 (38%) |
5 (50%) |
Wild type (A/A) |
1 (8%) |
1 (13%) |
1 (10%) |
HLA-B*27 prevalence, n (%) |
0 |
0 |
1 (10%) |
HLA-B*57 prevalence, n (%) |
0 |
1 (13%) |
1 (10%) |
Discussion
The progression to AIDS was observed to vary widely
in our HIV-1-infected pediatric cohort. It is noteworthy that a tenth of
all the children being followed in the clinic belonged to the LTNP or
slow progressor category.
The prevalence of LTNPs has been reported to be 3% in
children of Spanish and Italian origin [9], and 9% in children of
Italian origin [10]. These studies demonstrated the occurrence of known
ARGs (CCR5-D32
and SDF1-3’A) among LTNPs at low frequencies. Previous studies in India
have analyzed the prevalence of ARGs among exposed seronegative HIV-1
populations and healthy controls [6,11]. A study from a French cohort of
adults previously reported that the CCR5-D32 and SDF1-3’A along with
HLA-genotypes in combination, portray the synergistic effects of ARGs in
disease progression [12]. HLA class I alleles have been closely
associated with immune control in HIV among humans [13]. The observation
that HIV-infected HLA-B*27-positive individuals can mount strong
cytotoxic T lymphocyte (CTL) responses against the immunodominant
epitope showed that specific HLA class I alleles can influence the
outcome of HIV infection [14]. There is also a gag epitope
(corresponding to the gag amino acids 240-249) which is the main target
of the acute CD8+T-cell response in HIV-infected subjects who have the
HLA-B*57 allele [15].
Our study findings are limited by a cross-sectional
design and small sample size. The host genetic studies were also
restricted to a small number of factors; other host genetic factors are
yet to be studied in this population.
Our study highlights the proportion of Indian
children with slow disease progression among the cohort of children
living with HIV. These preliminary results of host genetic studies
suggest an association between known ARGs, as well as a possible
combined effect of host factors such as chemokine-receptors and their
ligands, and HLA-class molecules on the outcome of disease progression.
A larger sample size and a more extensive list of factors, including
host chemokine co-receptor polymorphisms and viral alterations
associated with HIV-1 disease non-progression may reveal better insight
into the protective correlates among the Indian HIV-1 population.
Contributors: RP: Performed the
experiments, analyzed the data and contributed towards manuscript
writing; UN: Designed the experiments and helped with the manuscript;
SDR: Performed the experiments and analyzed the data; and AS:
conceptualized the study and planed the analyses, and supervized writing
of the manuscript.
Funding: Department of Biotechnology-Wellcome
Trust-India Alliance Senior Fellowship Program (IA/S/13/2/501017)
Competing interests: None stated.
What This Study Adds?
•
There is a possible association of HLA alleles with other host
factors such as AIDS restriction genes in predicting HIV disease
outcome in perinatally HIV-infected children in India.
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