Delta32 Mutation Research Articles

Evidence for Gag p24-specific CD4 T cells with reduced susceptibility to R5 HIV-1 infection in a UK cohort of HIV-exposed-seronegative subjects.

To characterize HIV-1 Gag p24-specific CD4 cell responses in HIV-exposed-seronegative (ES) individuals. Twelve ES individuals, of diverse ethnicity and wild type for the CCR5 Delta-32 mutation, were identified. Controls were HIV-negative blood donors. Gag p24-specific and total Vbeta+ CD4 cells that expressed MIP-1beta, IFN-gamma and IL-2 were enumerated by intracytoplasmic cytokine staining. beta-Chemokine expression was correlated with susceptibility to R5 HIV-1 infection, as measured by polymerase chain reaction for integrated HIV-1 and by p24 enzyme-linked immunosorbent assay. Similar numbers of mitogen-stimulated and Vbeta+ MIP-1beta+, IFN-gamma+ and IL-2+ T cells were found in ES and HIV-negative control subjects. However, all ES subjects tested had an HIV Gag p24-specific MIP-1beta+, IFN-gamma+ and IL-2+ CD4 T-cell response that was rare in controls. p24-Specific cells of all ES but no control subjects could be expanded by in-vitro Ag/IL-2 stimulation, and when re-stimulated with an overlapping peptide series showed evidence of a broad CD4 cell memory response directed against multiple regions of Gag p24. Mitogen-stimulated ES CD4 cells were as susceptible to HIV infection as those from control subjects, but p24-specific IFN-gamma+ CD4 cells of six out of seven ES subjects tested were less susceptible to R5 HIV-1 infection than the counterpart fraction depleted of p24-specific IFN-gamma+ cells. The addition of blocking anti-beta-chemokine antibodies did not promote R5 HIV-1 infection of p24-specific IFN-gamma+ cells. Specific CD4 cell immunity, characterized by a broadly directed memory Gag-p24 CD4 cell response and reduced susceptibility of specific CD4 cells to R5 HIV-1 infection, is a likely correlate of non-transmission.

Polymorphisms in the CCR5 coding and noncoding regions among HIV type 1-exposed, persistently seronegative female sex-workers from Thailand.

Resistance to HIV-1 infection despite repeated exposures has been associated with one or more HIV-specific responses, enhanced nonspecific immune modifications, and/or host genetic polymorphisms in certain individuals (highly exposed, persistently seronegative, HEPS). In the present investigation, we focused on the CCR5 gene polymorphisms and the association of such mutations to resistance to HIV-1 infection among 12 HEPS women in Chiang Rai, northern Thailand, and compared our findings with data from 10 HIV-1-infected and 9 HIV-1-uninfected unexposed women from the same geographic area. Although we have previously shown that none of the Thai women carried the Delta32 mutation, further analysis of the CCR5 coding gene region revealed that none of the women had other mutations that affect coreceptor activity (C101X or FS299) or chemokine responses (C20S, A29S, L55Q, C178R). Analysis of the CCR5 promoter region revealed that the CCR5 haplogroup C (HHC; 60%) was the predominant haplogroup among these women. Comparative analysis of the frequencies of different haplogroups among the three groups did not reveal any statistically significant differences (p > 0.05). However, we did find that two individuals from the HEPS group were homozygous for HHF*2 (the CCR2b- 64I bearing haplogroup) compared to none from the HIV-1-infected and -uninfected groups. There was no detectable difference in specific CCR5 haplogroups and their ability to mediate env fusion or to mediate HIV-1 infection in vitro. These data suggest that homozygosity of the HHF*2 haplogroup may be one of the factors that mediate resistance to HIV-1 infection in this cohort of HEPS women.

Adverse effect of the CCR5 promoter −2459A allele on HIV‐1 disease progression

HIV positive individuals heterozygous for a 32 basepair deletion in the CCR5 encoding gene (CCR5 Delta32) have a reduced number of CCR5 receptors on the cell surface and a slower progression towards AIDS and death. Other human polymorphisms, such as the CCR2 64I and the CCR5 promoter -2459 A/G transition that has been discovered recently, have also been shown to influence HIV progression. Since genetic linkages make these polymorphisms interdependent variables, the aim of the present study was to isolate and evaluate the effect on HIV disease progression for each of these mutations independently. Genotypes were determined in 119 individuals enrolled in the Copenhagen AIDS Cohort. When including the concurrent effects of the CCR5 Delta32 and CCR2 64I mutations, homozygous carriers of the CCR5 promoter -2459A allele had a significantly faster progression towards death than heterozygous A/G individuals (P = 0.03), whereas this adverse effect was not significant when comparing A/A and G/G individuals. However, independent analysis revealed a significant adverse effect of the CCR5 promoter -2459A allele. Homozygous carriers of the -2459A allele that lack the protective effects of the CCR5 Delta32 and CCR2 64I mutations were found to have a median survival of 6.0 years, whereas carriers of the -2459G allele had a median survival of 9.4 years (P < 0.01).

Evidence for a post-entry barrier to R5 HIV-1 infection of CD4 memory T cells.

HIV-1 strains R5 and X4 can infect CD4 memory T cells in vivo. Anti-CD3/28 stimulation induces beta-chemokines and CCR5 down-regulation and renders these cells resistant to R5 HIV-1 infection. Here we describe an additional cellular mechanism that blocks productive R5 HIV-1 infection of CD4 memory T cells. Blood-derived CD4 memory T cells and CD4 T-cell clones were infected with primary R5 and X4 HIV-1 strains. Virus replication was correlated with CCR5 expression and beta-chemokine production. Virus entry and infectivity were measured by PCR for early and late products of HIV reverse transcription respectively. R5 strains were up to 1000-fold less infectious than X4 viruses for CD4 memory T cells. This resistance was independent of CCR5 levels and of the Delta-32 mutation and the CCR2-V64I/CCR5-59653T linked mutations. Blocking endogenous beta-chemokines relieved minimally this restriction. At the single cell level, CD4 memory cells were either permissive or non-permissive for R5 HIV-1 infection. R5 HIV titre was up to 10-fold lower than X4 virus titre even in a permissive clone. However, R5 viruses replicated as efficiently as X4 viruses in the permissive clone when neutralizing anti-beta chemokine antibodies were added. Non-permissive cells blocked a post-entry step of the virus life-cycle and expressed early but not late HIV transcripts. Neutralizing anti-beta chemokine antibodies promoted R5 virus replication marginally in the non-permissive clone. Some blood memory CD4 T cells retard R5 HIV-1 replication via endogenous beta-chemokines whereas others block productive R5 HIV-1 infection by an additional mechanism that interferes with a post-entry step of the virus life cycle. These natural barriers might contribute to lower pathogenicity of R5 HIV-1 strains for CD4 memory T cells than X4 viruses that emerge late in disease.

Frequency of CCR5 delta-32 mutation in human immunodeficiency virus (HIV)-seropositive and HIV-exposed seronegative individuals and in general population of Medellin, Colombia.

Repeated exposure to human immunodeficiency virus (HIV) does not always result in seroconversion. Modifications in coreceptors for HIV entrance to target cells are one of the factors that block the infection. We studied the frequency of Delta-32 mutation in ccr5 gene in Medellin, Colombia. Two hundred and eighteen individuals distributed in three different groups were analyzed for Delta-32 mutation in ccr5 gene by polymerase chain reaction (PCR): 29 HIV seropositive (SP), 39 exposed seronegative (ESN) and 150 individuals as a general population sample (GPS). The frequency of the Delta-32 mutant allele was 3.8% for ESN, 2.7% for GPS and 1.7% for SP. Only one homozygous mutant genotype (Delta-32/Delta-32) was found among the ESN (2.6%). The heterozygous genotype (ccr5/Delta-32) was found in eight GPS (5.3%), in one SP (3.4%) and in one ESN (2.6%). The differences in the allelic and genotypic frequencies among the three groups were not statistically significant. A comparison between the expected and the observed genotypic frequencies showed that these frequencies were significantly different for the ESN group, which indirectly suggests a protective effect of the mutant genotype (Delta-32/Delta-32). Since this mutant genotype explained the resistance of infection in only one of our ESN persons, different mechanisms of protection must be playing a more important role in this population.

Association of CCR5 ▵32 with reduced risk of asthma

We report that individuals carrying the CCR5 delta32 mutation, a naturally occurring variant of the C-C chemokine receptor 5 (CCR5), are at reduced risk of developing asthma. These data suggest a possible explanation for the high prevalence of this mutation in the general population.

Effect of chemokine receptor mutations on heterosexual human immunodeficiency virus transmission.

To assess the effect of mutations at the CCR-2 and CCR-5 loci on heterosexual human immunodeficiency virus (HIV) transmission, 144 persons heterosexually exposed to HIV (infected and uninfected [EU]) and 57 HIV-positive index partners were genotyped. A significantly higher frequency of 64I heterozygotes at CCR-2 was observed in HIV-positive than in EU women (P=.02, relative risk=1.6). The allele frequency of 64I in women was 8% in HIV-positive contacts and 1% in EUs (P<.02). At CCR-5, no difference in the frequency of Delta32 was seen between groups, and the CCR-5 genotypes did not differ in accumulated "at-risk" exposure in EUs. Combining the analysis of the Delta32 and 64I mutations in index partners suggested an additive effect on transmission (P=.10). Thus heterozygosity for 64I at CCR-2 acts as a risk factor for HIV infection of women after heterosexual contact but heterozygosity for Delta32 at CCR-5 has no detectable effect.

CCR5 genotype and resistance to vertical transmission of HIV-1.

A human gene has been identified that affects susceptibility to HIV-1 infection. The gene codes for CCR5, the coreceptor for macrophage-tropic strains of HIV-1. Individuals who are homozygous for a deleted, mutant form of the gene, delta32, display a high degree of natural resistance to sexual and parenteral transmission of HIV-1. To investigate whether delta32 plays a role in vertical transmission, we determined the CCR5 genotype of 552 children born to infected mothers in the United States and correlated the genotypes with HIV-1 infection status. Of these children, 13% were white, 30% Latino, and 56% African American, reflecting the ethnic makeup of infected women in the United States. The delta32 gene frequency varied among these groups, ranging from 0.08 in whites to 0.02 in both Latinos and African Americans. Approximately 27% of the children in each ethnic group were infected. Four children were identified as delta32 homozygotes, two uninfected whites (3.77%) and two uninfected Latinos (1.68%). None of the infected children displayed the delta32 homozygous genotype. Among Latinos and whites, the number of uninfected children who carried the homozygous delta32 mutation was significantly greater than that predicted by the Hardy-Weinberg equilibrium (p < .001 for Latinos, p = .044 for whites). This association was noted in Latino and white children whose mothers were either treated or untreated with zidovudine. These data document the occurrence of the homozygous delta32 genotype among children of HIV-1-infected mothers and suggest that this mutant genotype may confer protection from mother-to-child transmission of HIV-1. They also suggest that sexual, parenteral, and vertical transmission all involve processes that use CCR5 as a coreceptor for primary HIV-1 infection. Therefore, blocking the CCR5 receptor may provide an additional strategy to prevent HIV-1 vertical transmission.