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Association of the Insertion of CTTTT in 5’UTR of CD28 Gene with Low Level of CD28 Expression in T Cells: Influence on Susceptibility to HIV-1 Infection
Alex Soriano*1, H Oliva1, F García1, J Del Romero2, C Rodríguez2, A Barrasa2, J Lorenzo3, M Plana1, J Gatell1, and T Gallart1
1Hosp Clin, Univ of Barcelona, Spain; 2Ctr Med Sandoval, Madrid, Spain; and 3Hosp La Fé, Valencia, Spain
Background: CD28 is a
critical co-stimulatory molecule for the optimal activation of T cells and
regulates the expression of the main HIV co-receptors. We previously described
polymorphisms in 5’ untranslated region (5’UTR) of
CD28, which were associated with increased susceptibility to HIV-1 infection. Here,
our objective was to investigate whether 5’UTR polymorphisms could influence
the CD28 expression on CD4 and CD8 T cells.
Methods: We found that 5’
UTR of CD28 was amplified using appropriate primers, sequencing, and cloning in
49 individuals (28 exposed uninfected [EU] and 21 HIV+). Subsets of
CD3, CD4, and CD8 T cells, as well as expression of CD28 on CD4 and CD8 T cells
were done on peripheral blood mononuclear cells (PBMC) by flow citometry. The percentage of CD4+, CD8+,
CD4+CD28+, and CD8+CD28+ cells and
the mean fluorescent intensity (MFI) of CD4+CD28+, and
CD8+CD28+ cells were compared regarding the 5’UTR
genotype using a Wilcoxon rank sum test. A p value of <0.05 was considered
statistically significant.
Results: We found 39
individuals, 24 of 28 EU (85.7%) and 15 of 21 HIV+ (71.4%), with
homozygous genotype characterized by 4 tandem repeats of 5 nucleotides (CTTTT)
in 5’ extreme of 5’UTR. A total of 10 individuals, 4 of 28 EU (14.2%) and 6 of 21
HIV+ (28.5%), with heterozygous genotype characterized by 1 allele
with 4 tandem repeats and others with 5 tandem repeats (insertion of CTTTT).
The median (IQR) percentage of CD4, CD8, CD4+CD28+, and
CD8+CD28+ cells in homozygous (n = 39) and heterozygous (n
= 10) individuals were not statistically significantly different. The median
(IQR) MFI of CD4+CD28+ in homozygous (n = 34) and heterozygous (n = 8) was 245.5 (214 to 295) and 200.5
(173 to 246), respectively (p = 0,09). The median (IQR) MFI of CD8+CD28+
in homozygous (n = 34) and
heterozygous (n = 8) was 147.5 (134
to 180) and 118.5 (110.5 to 144), respectively (p = 0.04).
Conclusions: Our results
suggest that the insertion of CTTTT in 5’UTR of CD28 gene is associated with a
low level of CD28 expression in T cells. This could contribute to the increased
susceptibility to HIV-1 infection.
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