Maintenance of an Intact Human Immunodeficiency Virus Type 1 vpr Gene following Mother-to-Infant Transmission

The vpr sequences from six human immunodeficiency virus type 1 (HIV-1)-infected mother-infant pairs following perinatal transmission were analyzed. We found that 153 of the 166 clones analyzed from uncultured peripheral blood mononuclear cell DNA samples showed a 92.17% frequency of intact vpr open reading frames. There was a low degree of heterogeneity of vpr genes within mothers, within infants, and between epidemiologically linked mother-infant pairs. The distances between vpr sequences were greater in epidemiologically unlinked individuals than in epidemiologically linked mother-infant pairs. Moreover, the infants’ sequences displayed patterns similar to those seen in their mothers. The functional domains essential for Vpr activity, including virion incorporation, nuclear import, and cell cycle arrest and differentiation were highly conserved in most of the sequences. Phylogenetic analyses of 166 mother-infant pairs and 195 other available vpr sequences from HIV databases formed distinct clusters for each mother-infant pair and for other vpr sequences and grouped the six mother-infant pairs’ sequences with subtype B sequences. A high degree of conservation of intact and functional vpr supports the notion that vpr plays an important role in HIV-1 infection and replication in mother-infant isolates that are involved in perinatal transmission.     

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.     

Evaluation of genetic diversity of human immunodeficiency virus type 1<Emphasis Type="Italic">nef</Emphasis> gene associated with vertical transmission

The NEF gene is conserved among members of human and simian immunodeficiency viruses and may play an important role in viral pathogenesis. To determine the evolutionary dynamics and conservation of functionality of the human immunodeficiency virus type 1 (HIV-1) NEF gene during maternal-fetal transmission, we analyzed NEF sequences from seven mother-infant pairs following perinatal transmission, including a mother with infected twin infants. The NEF open reading frame was maintained in mother-infant isolates with a frequency of 86.2% following vertical transmission. While there was a low degree of viral heterogeneity and estimates of genetic diversity and high population growth rates of NEF sequences from mother-infant isolates, the infants' NEF sequences were slightly higher with respect to these parameters compared with the mothers' sequences. Both the mothers' and infants' NEF sequences were under positive selection pressure, as determined by a new method of Nielsen and Yang [Genetics 148:929-936;1998]. Based on genetic distance and phylogenetic parameters, the epidemiologically linked NEF sequences from mother-infant pairs were closer to each other compared with epidemiologically unlinked sequences from individuals. The functional domains essential for Nef activity, including membrane binding, CD4 and MHC-I downmodulation, T cell activation and interaction with factors of the cellular protein trafficking machinery, were conserved in most of the sequences from mother-infant pairs. The maintenance of intact NEF open reading frames with conserved functional domains and a low degree of genetic variability following vertical transmission supports the notion that NEF plays an important role in HIV-1 infection and replication in mothers and their perinatally infected infants.     

Characterization of HIV-1 envelope gp41 genetic diversity and functional domains following perinatal transmission

Background

HIV-1 envelope gp41 is a transmembrane protein that promotes fusion of the virus with the plasma membrane of the host cells required for virus entry. In addition, gp41 is an important target for the immune response and development of antiviral and vaccine strategies, especially when targeting the highly variable envelope gp120 has not met with resounding success. Mutations in gp41 may affect HIV-1 entry, replication, pathogenesis, and transmission. We, therefore, characterized the molecular properties of gp41, including genetic diversity, functional motifs, and evolutionary dynamics from five mother-infant pairs following perinatal transmission.

Results

The gp41 open reading frame (ORF) was maintained with a frequency of 84.17% in five mother-infant pairs' sequences following perinatal transmission. There was a low degree of viral heterogeneity and estimates of genetic diversity in gp41 sequences. Both mother and infant gp41 sequences were under positive selection pressure, as determined by ratios of non-synonymous to synonymous substitutions. Phylogenetic analysis of 157 mother-infant gp41 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 sequences. The functional domains of gp41, including fusion peptide, heptad repeats, glycosylation sites and lentiviral lytic peptides were mostly conserved in gp41 sequences analyzed in this study. The CTL recognition epitopes and motifs recognized by fusion inhibitors were also conserved in the five mother-infant pairs.

Conclusion

The maintenance of an intact envelope gp41 ORF with conserved functional domains and a low degree of genetic variability as well as positive selection pressure for adaptive evolution following perinatal transmission is consistent with an indispensable role of envelope gp41 in HIV-1 replication and pathogenesis.     

Genome Sequence of a Novel HIV-1 Circulating Recombinant Form 54_01B from Malaysia

We report here the first novel HIV-1 circulating recombinant form (CRF) 54_01B (CRF54_01B) isolated from three epidemiologically unlinked subjects of different risk groups in Malaysia. These recently sampled recombinants showed a complex genome organization composed of parental subtype B′ and CRF01_AE, with identical recombination breakpoints observed in the gag, pol, and vif genes. Such a discovery highlights the ongoing active generation and spread of intersubtype recombinants involving the subtype B′ and CRF01_AE lineages and indicates the potential of the new CRF in bridging HIV-1 transmission among different risk groups in Southeast Asia.     

How rhesus monkey infants budget their time between mothers and peers

Social play between two rhesus monkey (Macaca mulatta) infants takes place mainly when they are both not in body contact with their mothers. This suggests that social play and mother-infant body contact are potential competitors in the infants' time budgets. We investigated whether the presence of a playmate changed the duration of mother-infant body contact during the first 6 months of life. A decrease in contact would favour play opportunity. Mother-infant pairs were observed alternately alone and together with another pair. Resting, which always occurs during on-mother, was not reduced in the presence of a peer. Body contact during activity phases was reduced in most playing pairs, but only to a large extent in pairs which showed relatively high levels of contact in the situation without a peer. Play opportunity was further increased by synchronization of the rest-activity cycles of the two infants; this occurred without a reduction in mother-infant interactions. No influences by mothers on play opportunity were demonstrated, except that strong maternal interference with resting reduced activity synchronization.     

Viral linkage in HIV-1 seroconverters and their partners in an HIV-1 prevention clinical trial

Background

Characterization of viruses in HIV-1 transmission pairs will help identify biological determinants of infectiousness and evaluate candidate interventions to reduce transmission. Although HIV-1 sequencing is frequently used to substantiate linkage between newly HIV-1 infected individuals and their sexual partners in epidemiologic and forensic studies, viral sequencing is seldom applied in HIV-1 prevention trials. The Partners in Prevention HSV/HIV Transmission Study (ClinicalTrials.gov #{"type":"clinical-trial","attrs":{"text":"NCT00194519","term_id":"NCT00194519"}}NCT00194519) was a prospective randomized placebo-controlled trial that enrolled serodiscordant heterosexual couples to determine the efficacy of genital herpes suppression in reducing HIV-1 transmission; as part of the study analysis, HIV-1 sequences were examined for genetic linkage between seroconverters and their enrolled partners.

Methodology/Principal Findings

We obtained partial consensus HIV-1 env and gag sequences from blood plasma for 151 transmission pairs and performed deep sequencing of env in some cases. We analyzed sequences with phylogenetic techniques and developed a Bayesian algorithm to evaluate the probability of linkage. For linkage, we required monophyletic clustering between enrolled partners'' sequences and a Bayesian posterior probability of ≥50%. Adjudicators classified each seroconversion, finding 108 (71.5%) linked, 40 (26.5%) unlinked, and 3 (2.0%) indeterminate transmissions, with linkage determined by consensus env sequencing in 91 (84%). Male seroconverters had a higher frequency of unlinked transmissions than female seroconverters. The likelihood of transmission from the enrolled partner was related to time on study, with increasing numbers of unlinked transmissions occurring after longer observation periods. Finally, baseline viral load was found to be significantly higher among linked transmitters.

Conclusions/Significance

In this first use of HIV-1 sequencing to establish endpoints in a large clinical trial, more than one-fourth of transmissions were unlinked to the enrolled partner, illustrating the relevance of these methods in the design of future HIV-1 prevention trials in serodiscordant couples. A hierarchy of sequencing techniques, analysis methods, and expert adjudication contributed to the linkage determination process.     

The human immunodeficiency virus type 1 envelope confers higher rates of replicative fitness to perinatally transmitted viruses than to nontransmitted viruses

Selection of a minor viral genotype during perinatal transmission of human Immunodeficiency virus type 1 (HIV-1) has been observed, but there is a lack of information on the correlation of the restrictive transmission with biological properties of the virus, such as replicative fitness. Recombinant viruses expressing the enhanced green fluorescent protein or the Discosoma sp. red fluorescent (DsRed2) protein carrying the V1 to V5 regions of env from seven mother-infant pairs (MIPs) infected by subtype C HIV-1 were constructed, and competition assays were carried out to compare the fitness between the transmitted and nontransmitted viruses. Flow cytometry was used to quantify the frequency of infected cells, and the replicative fitness was determined based on a calculation that takes into account replication of competing viruses in a single infection versus dual infections. Transmitted viruses from five MIPs with the mothers chronically infected showed a restrictive env genotype, and all the recombinant viruses carrying the infants' Env had higher replicative fitness than those carrying the Env from the mothers. This growth fitness is lineage specific and can be observed only within the same MIP. In contrast, in two MIPs where the mothers had undergone recent acute infection, the viral Env sequences were similar between the mothers and infants and showed no further restriction in quasispecies during perinatal transmission. The recombinant viruses carrying the Env from the infants' viruses also showed replication fitness similar to those carrying the mothers' Env proteins. Our results suggest that newly transmitted viruses from chronically infected mothers have been selected to have higher replicative fitness to favor transmission, and this advantage is conferred by the V1 to V5 region of Env of the transmitted viruses. This finding has important implications for vaccine design or development of strategies to prevent HIV-1 transmission.     

Mother-infant relationships among free-ranging rhesus monkeys on Cayo Santiago: A comparison with captive pairs

The general course of mother-infant relationships among free-ranging rhesus monkeys (Macaca mulatta) on Cayo Santiago is remarkably similar both qualitatively and quantitatively to that observed in the socially living captive colony at the MRC Unit at Madingley, England. Nevertheless, small but consistent differences appear to be due to differences between mothers in the two environments rather than differences between infants. Captive mothers may be described as more protective and less encouraging of early independence in their infants than free-ranging mothers. Moreover, captive pairs have become more like free-ranging pairs over the years, perhaps as captive mothers have been allowed to raise their infants in the presence of kin. A unitary concept of environmental complexity is not useful in accounting for the results.     

Restricted Genetic Diversity of HIV-1 Subtype C Envelope Glycoprotein from Perinatally Infected Zambian Infants

Background

Mother-to-child transmission of HIV-1 remains a significant problem in the resource-constrained settings where anti-retroviral therapy is still not widely available. Understanding the earliest events during HIV-1 transmission and characterizing the newly transmitted or founder virus is central to intervention efforts. In this study, we analyzed the viral env quasispecies of six mother-infant transmission pairs (MIPs) and characterized the genetic features of envelope glycoprotein that could influence HIV-1 subtype C perinatal transmission.

Methodology and Findings

The V1-V5 region of env was amplified from 6 MIPs baseline samples and 334 DNA sequences in total were analyzed. A comparison of the viral population derived from the mother and infant revealed a severe genetic bottleneck occurring during perinatal transmission, which was characterized by low sequence diversity in the infant. Phylogenetic analysis indicates that most likely in all our infant subjects a single founder virus was responsible for establishing infection. Furthermore, the newly transmitted viruses from the infant had significantly fewer potential N-linked glycosylation sites in Env V1-V5 region and showed a propensity to encode shorter variable loops compared to the nontransmitted viruses. In addition, a similar intensity of selection was seen between mothers and infants with a higher rate of synonymous (dS) compared to nonsynonymous (dN) substitutions evident (dN/dS<1).

Conclusions

Our results indicate that a strong genetic bottleneck occurs during perinatal transmission of HIV-1 subtype C. This is evident through population diversity and phylogenetic patterns where a single viral variant appears to be responsible for infection in the infants. As a result the newly transmitted viruses are less diverse and harbored significantly less glycosylated envelope. This suggests that viruses with the restricted glycosylation in envelope glycoprotein appeared to be preferentially transmitted during HIV-1 subtype C perinatal transmission. In addition, our findings also indicated that purifying selection appears to predominate in shaping the early intrahost evolution of HIV-1 subtype C envelope sequences.     

MOTHER-INFANT SPATIAL RELATIONS IN CAPTIVE BOTTLENOSE DOLPHINS,TURSIOPS TRUNCATUS

The prolonged nursing period and strong, extended mother-infant bond observed among bottlenose dolphins may reflect social and physical ontogeny critical for infant survival. This study was conducted to quantify ontogentic changes in mother-infant contact time and the amount of time infants spent in specific spatial states with their mothers from birth to age 12 mo. These behaviors were studied through a systematic, longitudinal study of six mother-infant pairs of captive bottlenose dolphins from three different social groups. There was a significant decrease in the time infants spent with their mothers (logistic regression, P < 0.001), following the general mammalian pattern of increasing independence with age. When with their mothers, the probability that infants would be found in “echelon” position, flanking the mother, decreased as the calf aged (logistic regression, P <0.001), possibly due to anatomical and hydrodynamic factors. The probability that infants would be found in “infant” position, underneath the mother, increased with calf age (logistic regression, P < 0.001). Results obtained in this study are consistent with similar studies of wild bottlenose dolphin mother-infant pairs, indicating a suite of ontogenetically comparable behaviors between wild and captive bottlenose dolphins.     

Maternal aggressive contact vocalizations in captive bottlenose dolphins (Tursiops truncatus): Wide-band,low-frequency signals during mother/aunt-infant interactions

The mother-infant bond in bottlenose dolphins is critical to infant survival and has been reported to last from 3-10 years in both captive and wild populations. Little information on mother-infant communication during early development has been collected. This paper reports on a newly discovered dolphin vocalization, termed thunk, which is predominantly used by mothers toward infants. Four mother-infant pairs and one aunt-infant pair were the subjects for this study. Methods included a focal animal sampling technique using 2.5 min interval and event/continuous sampling regimes on audio- or videotape. Results indicated that thunks are produced by mothers or aunting females during infant departures (distances greater than 5 feet) and are frequently followed by disciplinary activity by the mother or aunt. In addition, thunks appeared to cease at approximately 9-10 months after birth, concurrent with a decrease in infant dependence. Thunks also were analyzed acoustically for frequency and duration parameters. Thunks have a harmonic structure with an energy peak in the 273–350 Hz range and ranged from 129–5,556 Hz in frequency and from 21–171 ms in duration. They appear to function as aggressive contact vocalizations produced by mothers and other adult females toward infants in order to maintain infant proximity. © 1995 Wiley-Liss, Inc.     

Evolution of human immunodeficiency virus type 1 in perinatally infected infants with rapid and slow progression to disease.

We addressed the relationship between the origin and evolution of human immunodeficiency virus type 1 (HIV-1) variants and disease outcome in perinatally infected infants by studying the V3 regions of viral variants in samples obtained from five transmitting mothers at delivery and obtained sequentially over the first year of life from their infected infants, two of whom (rapid progressors) rapidly progressed to having AIDS. Phylogenetic analyses disclosed that the V3 sequences from each mother-infant pair clustered together and were clearly distinct from those of the other pairs. Within each pair, the child's sequences formed a monophyletic group, indicating that a single variant initiated the infection in both rapid and slow progressors. Plasma HIV-1 RNA levels increased in all five infants during their first months of life and then declined within the first semester of life only in the three slow progressors. V3 variability increased over time in all infants, but no differences in the pattern of V3 evolution in terms of potential viral phenotype were observed. The numbers of synonymous and nonsynonymous substitutions varied during the first semester of life regardless of viral load, CD4+-cell count, and disease progression. Conversely, during the second semester of life the rate of nonsynonymous substitutions was higher than that of synonymous substitutions in the slow progressors but not in the rapid progressors, thus suggesting a stronger host selective pressure in the former. In view of the proposal that V3 genetic evolution is driven mainly by host immune constraints, these findings suggest that while the immune response to V3 might contribute to regulating viral levels after the first semester of life, it is unlikely to play a determinant role in the initial viral decline soon after birth.     

Dyadic interactions of infant lowland gorillas in an outdoor exhibit compared to an indoor holding area

The behavior of two lowland gorilla mother-infant pairs living in a social group at Zoo Atlanta was compared in an indoor holding area vs. an outdoor exhibit. Focal animal data were collected for each pair during 30-min observation sessions over 24 days, alternating between indoors and outdoors. A variety of individual and social behaviors differed in the two conditions, particularly infant behaviors and infant-controlled behaviors. Mothers and infants spent more time closer together inside than outside, and infants left mothers more and mothers approached infants more outside than inside. Additional differences included more object examination and solitary play by the infants, and more feeding by the mothers, outside. Mothers autogroomed more and infants engaged in more self-manipulation inside. Additionally, there were significantly more aggressive display behaviors directed toward the mother-infant pairs inside than outside, and the adults engaged in coprophagy inside but not outside. A variety of other behaviors measured did not change between the two environments. There was a clear effect on behavior of the different housing conditions in which the gorillas were kept. © 1994 Wiley-Liss, Inc.     

Independent variation and positive selection in env V1 and V2 domains within maternal-infant strains of human immunodeficiency virus type 1 in vivo.

Multiple targets for immune recognition and cellular tropism are localized to the V1 and V2 hypervariable regions in the amino portion of human immunodeficiency virus type 1 (HIV-1) gp120env. We have assessed genetic diversity in env V1 and V2 hypervariable domains in vivo within epidemiologically related strains of HIV-1. Our strategy was to analyze longitudinal samples from two seropositive mothers and multiple children infected by perinatal transmission. Although the V1 and V2 domains are closely linked in the HIV-1 genome, nucleotide sequences in V1 and in V2 evolved independently in maternal-infant viruses in vivo. A high proportion of the nucleotide substitutions would introduce amino acid diversity in V1 and in V2. A significant excess of nonsynonymous over synonymous substitutions was identified in HIV-1 env V1 and V2 peptides in the mothers and in two older children but was not generally apparent in HIV-1 sequences in infants. An excess of nonsynonymous over synonymous substitutions indicated that there is positive selection for independent genetic variation in the V1 and V2 domains in vivo. It is likely that there are host responses to complex determinants in the V1 or V2 hypervariable domain of HIV-1 gp120.     

Mother-infant interactions in captive slow lorises (Nycticebus coucang)

Information is presented about mother-infant interactions and infant development in a rarely studied prosimian primate, the slow loris (Nycticebus coucang). Four dyads were observed, by means of closed circuit TV, in a semi-natural environment for 1 hour per day three times a week. Infants were inactive for the first 6–8 weeks. Although mothers carried infants, they also left them alone for substantial periods of time after the 1st week. Over the 20-week study period, there was a significant decline in ventral contact but not in sitting within 12 inches or engaging in active social interactions. By the end of the study, infants were not yet fully independent. Three of the 4 were primarily responsible for maintaining physical closeness to the mother; they made most of the approaches and mothers made most of the departures. However, only 2 of the 4 infants had assumed responsibility for the initiation and maintenance of social interactions with the mother. By comparison with other nocturnal prosimians of similar size, the rate of development is relatively slow. Unlike many anthropoids, mothers were not strongly protective or rejecting. They did not bring infants back to a fixed location or try to prevent infants from leaving them; and the decline in ventral contact was not accompanied by fights between the pair. The 3 group-living mothers were more protective than the single individually housed mother, and it would seem advisable to isolate mother-infant pairs in laboratory breeding colonies.