Infected Mother-infant Pairs Research Articles

HIV Antiretroviral Resistance and Transmission in Mother–Infant Pairs Enrolled in a Large Perinatal Study

BackgroundDetection of antiretroviral (ARV) resistance in HIV-infected individuals is not uncommon and may be particularly problematic in HIV-infected pregnant women as it can lead to infant infection with resistant strains. To better evaluate the effect of drug resistance mutations (DRMs) on HIV mother-to-child transmission (MTCT), we determined the prevalence of DRMs in a subset of mother–infant pairs enrolled in a multi-center trial of infant prophylaxis among women not receiving ARVs during the current pregnancy.MethodsA case–control design of 1:4 (1 transmitter to 4 nontransmitters) was utilized to evaluate ARV resistance as a predictor of HIV MTCT in specimens obtained from mother–infant pairs. Secondary objectives included identification of potential risk factors associated with the presence of DRMs. Viroseq HIV-1 Genotyping System was performed on mother–infant specimens to assess for mutations that might result in a substantial reduction in drug susceptibility and clinical outcome, as determined by the Stanford HIV Drug Resistance Database.ResultsOne hundred and forty infants were infected. Of these, 123 HIV infected mother–infant pairs and 483 of 560 women who did not transmit HIV had amplifiable HIV nucleic acid enabling ARV resistance testing. A wide variety of DRMs were detected (Figure 1). Sixty (10%) of 606 women had clinically relevant DRMs; 12 (2%) had DRMs against more than 1 ARV class. Among 123 HIV− infected infants, 13 (11%) had clinically relevant DRMs with 3 (2%) harboring DRMs against more than 1 ARV class. Of 13 infants with DRMs, 10 (77%) were infected in utero. In univariate and multivariate analyses, DRMs in mothers were not associated with increased risk of HIV MTCT (AOR 0.79, 95% CI 0.38–1.5). Log HIV viral load was the only predictor of MTCT (OR 1.4, 95% CI 1.2−1.6). The presence of DRMs in mothers who transmitted was strongly associated with the presence of DRMs in infants (P < 0.001).ConclusionIn infected pregnant women without ARV exposure during their current gestation, the presence of pre-existing DRMs with a wide diversity was noted. DRMs do not increase the risk of HIV MTCT. However, if women with DRMs are not virologically suppressed they are likely to transmit resistant mutations even without selective ARV pressure, thus complicating treatment options.Disclosures All authors: No reported disclosures.

Evolution and mutations of hepatitis B virus quasispecies in genotype B and C during vertical transmission.

Evolution patterns of HBV QS between genotype B and C during vertical transmission are not well understood. In this study, we enrolled 10 HBV infected mother-infant pairs (four pairs with genotype B, four pairs with genotype C, and two with co-infection) without anti-viral therapy. Serum HBV DNA of mothers and infants were sequenced, HBV QS complexity and diversity were analyzed, polymorphisms and mutation sites were recorded, and phylogenetic trees were performed. Our result showed that the QS complexities in P (amino acid), C/PreC (amino acid), and PreS1 (nucleotide) gene were significantly higher in mothers than in infants in pairs with genotype C (P < 0.05), however, full-length and other genes showed non-significant differences (P > 0.05). Unlike genotype C, QS complexity of P gene (nucleotide) was significantly higher in infants than in mothers (P < 0.05) in pairs with genotype B, similarly, QS complexities of full-length and other genes (except Pre S2) were also higher in infants than in mothers but without significant differences (P > 0.05). QS diversities of full-length and most genes in genotype B were comparable between mothers and their infants (P > 0.05), in pairs with genotype C, dS of P, X, RT genes, genetic distance of Pre S1 gene (amino acid) and dN of Pre S1 gene were significant higher in mothers than in infants (P < 0.05). Several HBV mutations correlated with immune escape, e antigen loss and drug resistance were observed in infants. The results indicated that differences of HBV QS evolution patterns between genotype B and C during vertical transmission might contribute to distinct prognosis.

Influence of HIV-1 Genetic Variability on Vertical Transmission and Pathogenesis

HIV-1 exists as a genetically heterogeneous population within infected individuals and in infected population. Genetic variability or viral heterogeneity plays an important role in transmission, pathogenesis, immune response, disease progression and therapy as well as is the most effective way for the virus to evade the host immune response and persists in infected individuals. We have used HIV-1 infected motherinfant pairs as a transmitter-recipient model to elucidate the role of the molecular and biological properties of HIV-1 associated with transmission and pathogenesis. HIV-1 sequences derived from infected mothers were more heterogeneous than their younger infected infants’ HIV-1 sequences. However, the infants’ HIV-1 sequences diversified as they grew older. HIV-1 infants’ sequences were different from each other but similar or closer to their mother’s sequences. We found that the minor genotypes of HIV-1 found in mothers were transmitted to their infants, which was initially maintained as a homogeneous population in infants and diversified as the infants grew older. In addition, the phenotype of these minor geno types was macrophage-tropic, nonsyncytium inducing (NSI) referred as R5 HIV-1. We also analyzed several other regions of HIV-1 genome, including env, gag p17 and NC, pol RT, tat, rev, vif, vpr, vpu and nef infected mother-infant pairs and found that there was a high functional conservation of these genes. These findings suggested that HIV-1 heterogenity plays an important role in vertical transmission and pathogenesis. The properties of transmitted viruses and those that are associated with disease progression should be targeted for the development of new strategies for prevention and treatment of HIV-1 infection. Research should focus utilizing these findings in the development of better strategies for prevention and treatment of HIV-1.

Genotypic and functional properties of early infant HIV-1 envelopes.

BackgroundUnderstanding the properties of HIV-1 variants that are transmitted from women to their infants is crucial to improving strategies to prevent transmission. In this study, 162 full-length envelope (env) clones were generated from plasma RNA obtained from 5 HIV-1 Clade B infected mother-infant pairs. Following extensive genotypic and phylogenetic analyses, 35 representative clones were selected for functional studies.ResultsInfant quasispecies were highly homogeneous and generally represented minor maternal variants, consistent with transmission across a selective bottleneck. Infant clones did not differ from the maternal in env length, or glycosylation. All infant variants utilized the CCR5 co-receptor, but were not macrophage tropic. Relatively high levels (IC50 ≥ 100 μg/ml) of autologous maternal plasma IgG were required to neutralize maternal and infant viruses; however, all infant viruses were neutralized by pooled sera from HIV-1 infected individuals, implying that they were not inherently neutralization-resistant. All infant viruses were sensitive to the HIV-1 entry inhibitors Enfuvirtide and soluble CD4; none were resistant to Maraviroc. Sensitivity to human monoclonal antibodies 4E10, 2F5, b12 and 2G12 varied.ConclusionsThis study provides extensive characterization of the genotypic and functional properties of HIV-1 env shortly after transmission. We present the first detailed comparisons of the macrophage tropism of infant and maternal env variants and their sensitivity to Maraviroc, the only CCR5 antagonist approved for therapeutic use. These findings may have implications for improving approaches to prevent mother-to-child HIV-1 transmission.

Sensitive Oligonucleotide Ligation Assay for Low-Level Detection of Nevirapine Resistance Mutations in Human Immunodeficiency Virus Type 1 Quasispecies

This study has adapted the oligonucleotide ligation assay (OLA) to probe for low-level nevirapine (NVP) resistance mutations K103N and Y181C in the human immunodeficiency virus type 1 (HIV-1) population of infected mother-infant pairs from Uganda. When NVP is used to prevent perinatal transmission, NVP-resistant HIV-1 clones may be rapidly selected due to a low barrier for mutation and a relatively high level of fitness (compared to that of other drug-resistant HIV-1 clones). Monitoring for even a low frequency of NVP resistance mutations may help predict the success of subsequent treatment or warrant the use of another regimen to prevent transmission in a subsequent pregnancy. The standard OLA was optimized by using nonstandard bases in oligonucleotides to allow promiscuous base pairing and accommodate significant HIV-1 heterogeneity. Radiolabeled as opposed to fluorescently tagged oligonucleotides increased the sensitivity, whereas alteration of the template, oligonucleotides, salt, and thermostable DNA ligase concentrations increased the specificity for the detection of minority codons. This modified OLA is now capable of detecting mutants with the K103N or the Y181C mutation present in an HIV-1 population at a frequency of approximately 0.4% and is at least 10- to 30-fold more sensitive than the original protocol. A cohort of 19 Ugandan mothers who received NVP treatment perinatally were sampled 6 weeks postdelivery. Ten of 19 HIV-1 DNA samples extracted from peripheral blood mononuclear cells had a detectable K103N (0.5 to 44%) or Y181C (0.8 to 92.5%) mutation, but only one plasma HIV-1 RNA sample had a viral population with the Y181C mutation. These findings suggest that OLA is a robust, sensitive, and specific method for the detection of low-frequency drug resistance mutations in an intrapatient HIV-1 population.

Conservation of functional domains and limited heterogeneity of HIV-1 reverse transcriptase gene following vertical transmission.

BackgroundThe reverse transcriptase (RT) enzyme of human immunodeficiency virus type 1 (HIV-1) plays a crucial role in the life cycle of the virus by converting the single stranded RNA genome into double stranded DNA that integrates into the host chromosome. In addition, RT is also responsible for the generation of mutations throughout the viral genome, including in its own sequences and is thus responsible for the generation of quasi-species in HIV-1-infected individuals. We therefore characterized the molecular properties of RT, including the conservation of functional motifs, degree of genetic diversity, and evolutionary dynamics from five mother-infant pairs following vertical transmission.ResultsThe RT open reading frame was maintained with a frequency of 87.2% in five mother-infant pairs' sequences following vertical transmission. There was a low degree of viral heterogeneity and estimates of genetic diversity in mother-infant pairs' sequences. Both mothers and infants RT sequences were under positive selection pressure, as determined by the ratios of non-synonymous to synonymous substitutions. Phylogenetic analysis of 132 mother-infant RT sequences revealed distinct clusters for each mother-infant pair, suggesting that the epidemiologically linked mother-infant pairs were evolutionarily closer to each other as compared with epidemiologically unlinked mother-infant pairs. The functional domains of RT which are responsible for reverse transcription, DNA polymerization and RNase H activity were mostly conserved in the RT sequences analyzed in this study. Specifically, the active sites and domains required for primer binding, template binding, primer and template positioning and nucleotide recruitment were conserved in all mother-infant pairs' sequences.ConclusionThe maintenance of an intact RT open reading frame, conservation of functional domains for RT activity, preservation of several amino acid motifs in epidemiologically linked mother-infant pairs, and a low degree of genetic variability following vertical transmission is consistent with an indispensable role of RT in HIV-1 replication in infected mother-infant pairs.

THE VERTICAL TRANSMISSION OF HUMAN IMMUNODEFICIENCY VIRUS TYPE 1: Molecular and Biological Properties of the Virus

The vertical (mother-to-infant) transmission of human immunodeficiency virus type 1 (HIV-1) occurs at an estimated rate of more than 30% and is the major cause of AIDS in children. Numerous maternal parameters, including advanced clinical stages, low CD4+ lymphocyte counts, high viral load, immune response, and disease progression have been implicated in an increased risk of vertical transmission. While the use of antiretroviral therapy (ART) during pregnancy has been shown to reduce the risk of vertical transmission, selective transmission of ART-resistant mutants has also been documented. Elucidation of the molecular mechanisms of vertical transmission might provide relevant information for the development of effective strategies for prevention and treatment. By using HIV-1 infected mother-infant pairs as a transmitter-recipient model, the minor genotypes of HIV-1 with macrophage-tropic and non-syncytium-inducing phenotypes (R5 viruses) in infected mothers were found to be transmitted to their infants and were initially maintained in the infants with the same properties. In addition, the transmission of major and multiple genotypes has been suggested. Furthermore, HIV-1 sequences found in non-transmitting mothers (mothers who failed to transmit HIV-1 to their infants in the absence of ART) were less heterogeneous than those from transmitting mothers, suggesting that viral heterogeneity may play an important role in vertical transmission. In the analysis of other regions of the HIV-1 genome, we have shown a high conservation of intact and functional gag p17, vif, vpr, vpu, tat, and nef open reading frames following mother-to-infant transmission. Moreover, the accessory genes, vif and vpr, were less functionally conserved in the isolates of non-transmitting mothers than transmitting mothers and their infants. We, therefore, should target the properties of transmitted viruses to develop new and more effective strategies for the prevention and treatment of HIV-1 infection.

Phylogenetic and phenotypic analysis of HIV type 1 env gp120 in cases of subtype C mother-to-child transmission.

Human immunodeficiency virus type 1 (HIV-1) subtype C constitutes a majority of the newly transmitted cases of HIV-1 in many developing countries. There is growing evidence suggesting that subtype C viruses may display characteristics that make them distinct from subtype B and other subtypes, and such differences may affect its transmission and pathogenesis in infected individuals. In this study, HIV-1 sequences from the C2-V4 region of the envelope gene were analyzed from four infected mother-infant pairs (MIPs) after perinatal transmission in Zambia. We found that all viral isolates from four Zambian MIPs were of the subtype C HIV-1 subgroup. All tested isolates were macrophage tropic and did not infect any tested T cell lines or form syncytia in vitro. In addition, the isolates appear to use exclusively the CCR5 coreceptor. Phylogenetic analyses clearly indicated two contrasting phylogenetic transmission patterns for the four MIPs analyzed in the present study. Three cases displayed a pattern of selective transmission of a single or a few variants, and one case was found to transmit multiple maternal HIV-1 variants to her infant. The differences in the mode and timing of transmission may account for the observed transmission pattern among four MIPs.

Molecular mechanisms of human immunodeficiency virus type I mother-infant transmission

Maternal-fetal transmission accounts for approximately 80% of all HIV-1 infections in children. Mother-to-infant transmission of HIV-1 predominately occurs perinatally at an estimated rate of more than 30%. However, the rate of transmission also depends on the symptoms of the disease and the frequency of delivery at estimated rates of 24% in symptom-free mothers and 65% in mothers with the disease or who have had a previous child with AIDS. In contrast, the rate of HIV-2 mother-infant transmission is much lower compared to HIV-1 and dually infected mothers could transmit both viruses, but the transmission of HIV-1 has generally been observed. There are no clearly defined factors, viral or host, associated with maternal transmission of HIV-1. However, maternal parameters, including advanced clinical stages of the mother, low CD4+ lymphocyte counts, maternal immune response to HIV-1, recent infection, high level of circulating HIV-1, and maternal disease progression have been implicated in an increased risk of mother-to-infant transmission of HIV-1. Molecular and biological properties of HIV-1 involved in mother-to-infant transmission are critical determinants of perinatal transmission. Studies from my laboratory compared the HIV-1 DNA sequences in the V3 region of the envelope gene from seven mother-infant pairs, following perinatal transmission. The minor HIV-1 genotype predominates initially as a homogeneous population in the infant and then becomes diverse as the infant grows older. Nucleotide sequencing directly derived from HIV-1 DNA isolated from infected mother-infant pairs' peripheral blood mononuclear cells (PBMC), alignment of deduced amino acid sequences, and phylogenetic analysis have provided a powerful tool to analyze and identify HIV-1 genotypes transmitted from mother to infant.

Characterization of mother-infant HIV type 1 gag p17 sequences associated with perinatal transmission.

The gag p17 matrix sequences of human immunodeficiency virus type 1 (HIV-1) from seven infected mother-infant pairs were analyzed after perinatal transmission. The p17 matrix open reading frame was maintained in 143 of the 166 clones analyzed (86.2% frequency of intact p17 open reading frames). The functional domains essential for p17 matrix function in HIV-1 replication, including targeting of Gag to the plasma membrane, virus assembly and release, envelope glycoprotein incorporation into virus particle, virus entry, and localization of the virus preintegration complex to the nucleus of nondividing cells, were highly conserved in most of the sequences. In addition, examination of the three-dimensional structure of the p17 matrix protein in mother-infant isolates showed a high degree of conservation of amino acids required for correct folding and biological activity. Several amino acid motifs common to most of the mother-infant pairs sequences, including pair-specific signature sequences, were observed. There was a low degree of heterogeneity of gag p17 sequences within mothers, within infants, and between mother-infant pairs, but the distances were greater between epidemiologically unlinked individuals. Phylogenetic analyses of 166 mother-infant pairs and 181 other p17 sequences available from HIV-1 databases revealed distinct clusters for each mother-infant pair and for other p17 sequences. In conclusion, these findings indicate that an intact and functional gag p17 matrix is maintained during maternal-fetal transmission and that several motifs in p17 may be associated with perinatal transmission.

Conservation of an intact vif gene of human immunodeficiency virus type 1 during maternal-fetal transmission.

The human immunodeficiency virus type 1 (HIV-1) vif gene is conserved among most lentiviruses, suggesting that vif is important for natural infection. To determine whether an intact vif gene is positively selected during mother-to-infant transmission, we analyzed vif sequences from five infected mother-infant pairs following perinatal transmission. The coding potential of the vif open reading frame directly derived from uncultured peripheral blood mononuclear cell DNA was maintained in most of the 78,912 bp sequenced. We found that 123 of the 137 clones analyzed showed an 89.8% frequency of intact vif open reading frames. There was a low degree of heterogeneity of vif genes within mothers, within infants, and between epidemiologically linked mother-infant pairs. The distances between vif sequences were greater in epidemiologically unlinked individuals than in epidemiologically linked mother-infant pairs. Furthermore, the epidemiologically linked mother-infant pair vif sequences displayed similar patterns that were not seen in vif sequences from epidemiologically unlinked individuals. The functional domains, including the two cysteines at positions 114 and 133, a serine phosphorylation site at position 144, and the C-terminal basic amino acids essential for vif protein function, were highly conserved in most of the sequences. Phylogenetic analyses of 137 mother-infant pair vif sequences and 187 other available vif sequences from HIV-1 databases revealed distinct clusters for vif sequences from each mother-infant pair and for other vif sequences. Taken together, these findings suggest that vif plays an important role in HIV-1 infection and replication in mothers and their perinatally infected infants.

Genetic analysis of human immunodeficiency virus type 1 envelope V3 region isolates from mothers and infants after perinatal transmission.

The human immunodeficiency virus type 1 (HIV-1) sequences from variable region 3 (V3) of the envelope gene were analyzed from seven infected mother-infant pairs following perinatal transmission. The V3 region sequences directly derived from the DNA of the uncultured peripheral blood mononuclear cells from infected mothers displayed a heterogeneous population. In contrast, the infants' sequences were less diverse than those of their mothers. In addition, the sequences from the younger infants' peripheral blood mononuclear cell DNA were more homogeneous than the older infants' sequences. All infants' sequences were different but displayed patterns similar to those seen in their mothers. In the mother-infant pair sequences analyzed, a minor genotype or subtype found in the mothers predominated in their infants. The conserved N-linked glycosylation site proximal to the first cysteine of the V3 loop was absent only in one infant's sequence set and in some variants of two other infants' sequences. Furthermore, the HIV-1 sequences of the epidemiologically linked mother-infant pairs were closer than the sequences of epidemiologically unlinked individuals, suggesting that the sequence comparison of mother-infant pairs done in order to identify genetic variants transmitted from mother to infant could be performed even in older infants. There was no evidence for transmission of a major genotype or multiple genotypes from mother to infant. In conclusion, a minor genotype of maternal virus is transmitted to the infants, and this finding could be useful in developing strategies to prevent maternal transmission of HIV-1 by means of perinatal interventions.

A nursery outbreak of group A streptococcal infection

We report an outbreak of 23 neonatal group A streptococcal infections including two cases of septicaemia in a nursery for the newborn. At the same time, 19 mothers had puerperal endometritis. The outbreak lasted for about 2 months and could not be eradicated by ordinary hygienic measures. In a colonisation study, 19 of 90 umbilical stumps studied on the day of discharge from hospital harboured group A streptococci, all of the same epidemic strain T28 provisional M-type 2841/opacity factor positive (T28/MPT2841/OF+). Chlorhexidine gluconate was therefore applied daily to the umbilical stumps. The outbreak came to an end with the introduction of this procedure. The time interval between delivery and recognition of infection was shorter in infants than in mothers. There were also only two infected mother-infant pairs. Taken together, this suggests that infected umbilical stumps on symptomless infants were a likely source of the maternal infections. Throughout 1 year from the introduction of the chlorhexidine treatment, we have not seen a case of group A streptococcal infection in neonates. Surveillance cultures from umbilical cords after the outbreak have also been negative. We conclude that bacteriological surveillance of umbilical stumps is valuable in recognising an outbreak and should be seriously considered when a group A streptococcal infection has been recorded in a nursery.