Astrid K. N. Iversen

Heterozygosity for a deletion in the CKR-5 gene leads to prolonged AIDS-free survival and slower CD4 T-cell decline in a cohort of HIV-seropositive individuals.

Objective:Recently, it has been shown that a homozygous 32 base-pair deletion in the gene encoding CKR-5, a major coreceptor for HIV-1, leads to resistance to infection with HIV-1. We have investigated whether HIV-seropositive individuals who were heterozygous for the CKR-5 deletion had a different course of the disease. Design:Thirty-five high-risk HIV-seronegative and 99 HIV-seropositive Danish homosexual men followed from 1985 to 1996 and 37 blood donors were analysed for their CKR-5 genotype by polymerase chain reaction. Results:Two (6%) of the 35 HIV-seronegative subjects at high-risk of infection were homozygous and seven (20%) were heterozygous for the CKR-5 deletion. This was not significantly different from the distribution in normal donors. Twenty-two (22%) of the 99 HIV-seropositive subjects were heterozygous and none was homozygous. Two subgroups of patients who had an opposite course of the HIV disease were identified. Of nine long-term non-progressors, six (66%) were heterozygous for the deletion. This frequency is significantly higher than in nine rapid progressors of whom none was heterozygous. The frequency of heterozygotes in long-term nonprogressors was also significantly higher than in the cohort as a whole. A Kaplan-Meier plot of the HIV-seropositive subjects, of whom 57 developed AIDS, showed a significantly better prognosis within the first 7 years of follow-up for those who were heterozygous for the deletion. Heterozygous individuals also had a significantly slower decrease in CD4 T-cell count per year. Conclusion:Individuals who are heterozygous for the 32-base-pair deletion in the CKR-5 gene have a slower decrease in their CD4 T-cell count and a longer AIDS-free survival than individuals with the wild-type gene for up to 11 years of follow-up.

AIDS restriction HLA allotypes target distinct intervals of HIV-1 pathogenesis.

An effective acquired immune response to infectious agents mediated by HLA-restricted T-cell recognition can target different stages of disease pathogenesis. We show here that three distinct HLA alleles known to alter the overall rate of AIDS progression act during distinct intervals after HIV-1 infection. The discrete timing of HLA allele influence suggests alternative functional mechanisms in immune defense against this dynamic and chronic immunosuppressive disease.

Distinct determinants of human immunodeficiency virus type 1 RNA and DNA loads in vaginal and cervical secretions.

The relationship between human immunodeficiency virus type 1 (HIV-1) viral RNA and proviral DNA load in vagina and cervix and that found in the plasma and peripheral blood mononuclear cells (PBMC) was investigated in 28 HIV-1-infected women. Of the patients, 64% had > or = 1 HIV-1 RNA-positive genital sample, while 71% had > or = 1 DNA-positive sample. The higher the cervical HIV load, the more widespread was the virus in the genital tract. A strong correlation was found between viral RNA load in plasma and the genital tract, whereas the association between proviral DNA load in PBMC and the genital tract was less evident. Cervical HIV-1 DNA correlated with a viral RNA load > or = 50,000 copies/mL. Cervical HIV-1 RNA levels ranged from 10% to 100% of the plasma levels. Thus, a continuous transmission risk from untraumatized genital epithelium exists in the majority of HIV-1-infected women at all stages of infection.

Conflicting Selective Forces Affect T Cell Receptor Contacts in an Immunodominant Human Immunodeficiency Virus Epitope.

Cytotoxic T lymphocytes (CTLs) are critical for the control of human immunodeficiency virus, but containment of virus replication can be undermined by mutations in CTL epitopes that lead to virus escape. We analyzed the evolution in vivo of an immunodominant, HLA-A2–restricted CTL epitope and found two principal, diametrically opposed evolutionary pathways that exclusively affect T cell–receptor contact residues. One pathway was characterized by acquisition of CTL escape mutations and the other by selection for wild-type amino acids. The pattern of CTL responses to epitope variants shaped which variant(s) prevailed in the virus population. The pathways notably influenced the amount of plasma virus, as patients with efficient CTL selection had lower plasma viral loads than did patients without efficient selection. Thus, viral escape from CTL responses does not necessarily correlate with disease progression.

Conserved Footprints of APOBEC3G on Hypermutated Human Immunodeficiency Virus Type 1 and Human Endogenous Retrovirus HERV-K(HML2) Sequences

ABSTRACT The human polynucleotide cytidine deaminases APOBEC3G (hA3G) and APOBEC3F (hA3F) are antiviral restriction factors capable of inducing extensive plus-strand guanine-to-adenine (G-to-A) hypermutation in a variety of retroviruses and retroelements, including human immunodeficiency virus type 1 (HIV-1). They differ in target specificity, favoring plus-strand 5′GG and 5′GA dinucleotide motifs, respectively. To characterize their mutational preferences in detail, we analyzed single-copy, near-full-length HIV-1 proviruses which had been hypermutated in vitro by hA3G or hA3F. hA3-induced G-to-A mutation rates were significantly influenced by the wider sequence context of the target G. Moreover, hA3G, and to a lesser extent hA3F, displayed clear tetranucleotide preference hierarchies, irrespective of the genomic region examined and overall hypermutation rate. We similarly analyzed patient-derived hypermutated HIV-1 genomes using a new method for estimating reference sequences. The majority of these, regardless of subtype, carried signatures of hypermutation that strongly correlated with those induced in vitro by hA3G. Analysis of genome-wide hA3-induced mutational profiles confirmed that hypermutation levels were reduced downstream of the polypurine tracts. Additionally, while hA3G mutations were found throughout the genome, hA3F often intensely mutated shorter regions, the locations of which varied between proviruses. We extended our analysis to human endogenous retroviruses (HERVs) from the HERV-K(HML2) family, finding two elements that carried clear footprints of hA3G activity. This constitutes the most direct evidence to date for hA3G activity in the context of natural HERV infections, demonstrating the involvement of this restriction factor in defense against retroviral attacks over millions of years of human evolution.

Acute cytomegalovirus infection in Kenyan HIV-infected infants.

Objective:Cytomegalovirus (CMV) coinfection may influence HIV-1 disease progression during infancy. Our aim was to describe the incidence of CMV infection and the kinetics of viral replication in Kenyan HIV-infected and HIV-exposed uninfected infants. Methods:HIV-1 and CMV plasma viral loads were serially measured in 20 HIV-exposed uninfected and 44 HIV-infected infants born to HIV-infected mothers. HIV-infected children were studied for the first 2 years of life, and HIV-exposed uninfected infants were studied for 1 year. Results:CMV DNA was detected frequently during the first months of life; by 3 months of age, CMV DNA was detected in 90% of HIV-exposed uninfected infants and 93% of infants who had acquired HIV-1 in utero. CMV viral loads were highest in the 1–3 months following the first detection of virus and declined rapidly thereafter. CMV peak viral loads were significantly higher in the HIV-infected infants compared with the HIV-exposed uninfected infants (mean 3.2 versus 2.7 log10 CMV DNA copies/ml, respectively, P = 0.03). The detection of CMV DNA persisted to 7–9 months post-CMV infection in both the HIV-exposed uninfected (8/17, 47%) and HIV-infected (13/18, 72%, P = 0.2) children. Among HIV-infected children, CMV DNA was detected in three of the seven (43%) surviving infants tested between 19 and 21 months post-CMV infection. Finally, a strong correlation was found between peak CMV and HIV-1 viral loads (ρ = 0.40, P = 0.008). Conclusion:Acute CMV coinfection is common in HIV-infected Kenyan infants. HIV-1 infection was associated with impaired containment of CMV replication.

HIV-infected individuals with the CCR delta32/CCR5 genotype have lower HIV RNA levels and higher CD4 cell counts in the early years of the infection than do patients with the wild type. Copenhagen AIDS Cohort Study Group.

The relations among serum HIV RNA levels, CD4 cell counts, presence of the mutant CCR5-allele in heterozygous form, and clinical outcome was analyzed in 96 patients from the Copenhagen AIDS Cohort. In the early years of the infection, patients with the CCR5 delta32/CCR5 genotype had significantly lower HIV RNA levels (p = 0.005) and higher CD4 cell counts (p < 0.005) than did patients homozygous for the normal allele. The long-term clinical benefit of being heterozygous is small and cannot solely explain the large interpatient variation in progression rates. The beneficial effect of being heterozygous seems to be mediated by events in the early stages of the HIV infection.

Chemokine receptor CCR2b 64I polymorphism and its relation to CD4 T-cell counts and disease progression in a Danish cohort of HIV-infected individuals. Copenhagen AIDS cohort.

We have investigated the role of the recently described mutation in CCR2b named 64I in relation to HIV resistance, CD4 T-cell counts, and disease progression in Danish individuals by polymerase chain reaction (PCR)-based methods as well as sequenced full-length CXCR4 and CCR5 genes from HIV-infected long-term nonprogressors for possible mutations. In total, 215 Danish individuals were analyzed for 64I allele frequency; disease progression was followed in 105 HIV-1-positive homosexual Danish men from their first known positive HIV-1 test result and up to 11 years. In 87 individuals, the CD4 T-cell count was monitored closely. We found no significant difference in 64I allele frequency between HIV-1-seropositive persons (0.08), high-risk HIV-1-seronegative persons (0.11), and blood donors (0.06). No significant difference was observed in annual CD4 T-cell decline, CD4 T-cell counts at the time of AIDS, in AIDS-free survival as well as survival with AIDS, between 64I allele carriers and wild-type individuals. Among 9 long-term nonprogressors, 2 carried the 64I allele, while none of 9 fast progressors carried the 64I allele. However, this was not significantly different (p=.47). Long-term nonprogression could not be explained by CXCR4 polymorphism or other polymorphisms in the CCR5 gene than the CCR5delta32 allele. Furthermore, we were not able to detect any significant independent effect of the 64I allele on development to AIDS, overall survival, and annual CD4 T-cell decline in this cohort.

APOBEC3G-Induced Hypermutation of Human Immunodeficiency Virus Type-1 Is Typically a Discrete “All or Nothing” Phenomenon

The rapid evolution of Human Immunodeficiency Virus (HIV-1) allows studies of ongoing host–pathogen interactions. One key selective host factor is APOBEC3G (hA3G) that can cause extensive and inactivating Guanosine-to-Adenosine (G-to-A) mutation on HIV plus-strand DNA (termed hypermutation). HIV can inhibit this innate anti-viral defense through binding of the viral protein Vif to hA3G, but binding efficiency varies and hypermutation frequencies fluctuate in patients. A pivotal question is whether hA3G-induced G-to-A mutation is always lethal to the virus or if it may occur at sub-lethal frequencies that could increase viral diversification. We show in vitro that limiting-levels of hA3G-activity (i.e. when only a single hA3G-unit is likely to act on HIV) produce hypermutation frequencies similar to those in patients and demonstrate in silico that potentially non-lethal G-to-A mutation rates are ∼10-fold lower than the lowest observed hypermutation levels in vitro and in vivo. Our results suggest that even a single incorporated hA3G-unit is likely to cause extensive and inactivating levels of HIV hypermutation and that hypermutation therefore is typically a discrete “all or nothing” phenomenon. Thus, therapeutic measures that inhibit the interaction between Vif and hA3G will likely not increase virus diversification but expand the fraction of hypermutated proviruses within the infected host.

Therapeutic immunization of highly active antiretroviral therapy-treated HIV-1-infected patients: safety and immunogenicity of an HIV-1 gag/poly-epitope DNA vaccine.

In view of the global emergency posed by lack of access to highly active antiretroviral therapy (HAART) and the limitations of current drug regimens, alternative therapeutic strategies are urgently needed. Cellular immune responses elicited by HIV-1 exert some control over virus replication, therefore the enhancement of HIV-1-specific responses by therapeutic vaccination might lead to viral containment without HAART. We evaluated the safety and immunogenicity, in HIV-1-infected individuals under HAART suppression, of a DNA vaccine, pTHr.HIVA.