Perinatal infection by human immunodeficiency virus type 1 (HIV-1): relationship between proviral copy number in vivo, viral properties in vitro, and clinical outcome

Clinico-Immunological Profile of Children Infected with HIV Through Vertical Transmission, in Southern India

BACKGROUND

Karnataka, being "High Prevalent State" of southern India, the HIV infection among antenatal women has crossed 1%. There are very few reports available with CD4 count and stage wise clinical spectrum among children. The clinical spectrum among HIV infected infants and children vary in different areas of the world. Hence it is important to know the spectrum of opportunistic infections and their respective CD4 count among HIV infected children of our locality.

MATERIALS AND METHODS

The opportunistic infections among 31 paediatric seropositive patients were evaluated. These all patients were classified as per CDC guide lines into stage I, stage II, and stage III based on CD4 counts of > 1000cells/μl, 500-999 cells/μl,<500cells/μl respectively. The opportunistic infections were diagnosed by standard laboratory investigations. Clinical spectrum presented by each stage children was documented.

RESULTS

Children in stage I were 5(16.1%),stage II 14(45.1%) and stage III 12(38.7%). Oral candidiasis (29%) was the commonest, followed by recurrent respiratory tract infection (25.8%), tubercular lymphadenitis (16.1%) and chronic diarrhoea (12.9%).

CONCLUSION

The present study showed the children with higher CD4 count had few infections and children with lower CD4 count presented with multiple opportunistic infections. This study also showed vertical transmission as the sole mode of transmission.

HIV-1 Transmission, Replication Fitness and Disease Progression

Upon transmission, human immunodeficiency virus type 1 (HIV-1) establishes infection of the lymphatic reservoir, leading to profound depletion of the memory CD4+ T cell population despite the induction of the adaptive immune response. The rapid evolution and association of viral variants having distinct characteristics during different stages of infection, the level of viral burden, and rate of disease progression suggest a role for viral variants in this process. Here, we review the literature on HIV-1 variants and disease and discuss the importance of viral fitness for transmission and disease.

Genotypic and phenotypic characterization of viral isolates from HIV-1 subtype C-infected children with slow and rapid disease progression

The genotypes and biological phenotypes of HIV-1 isolates obtained from 40 perinatally infected children in South Africa were analyzed. This included 15 infants who had HIV-related symptoms, most of whom died within 2 years of birth (rapid progressors), and 25 children who survived between 4 and 9 years with varying signs of disease (slow progressors). Heteroduplex mobility assays and sequence analysis confirmed that within the env and gag regions, all isolates were HIV-1 subtype C. Viral isolates from 14 of the 15 rapid progressors used the CCR5 coreceptor, whereas 1 (02ZARP1) used both the CXCR4 and CCR5 coreceptors. Among the 25 slow progressors, 22 isolates used CCR5 only, 2 used CXCR4 only, and 1 used both CCR5 and CXCR4. Two of the slow-progressing children who harbored CXCR4-using viruses had AIDS. All four CXCR4-using viruses had genotypic changes in the V3 region previously shown to be associated with CXCR4 usage. This cross-sectional study shows that HIV-1 subtype C viruses from both rapid- and slow-progressing perinatally infected children used predominantly CCR5. Similar to adults, CXCR4 usage was uncommon among HIV-1 subtype C isolates from pediatric infections.

HIV-1 fitness and macrophages

HIV-1 comprises a collection of closely related, but not identical, viruses or quasispecies. Fitness represents a selective advantage for propagation among populations of organisms competing in a particular environment and is an important characteristic of viruses because of a link between fitness and pathogenesis. Environmental differences based on the type of cell that is targeted for infection or the cell type that produces virus, impact fitness. CD4-expressing cells of lymphocyte or macrophage lineage are the principal host cells for HIV-1, although the milieu in lymphocytes is distinct from the macrophage environment from the perspective of cell half-life and activation, signal transduction and expression of coreceptors, and bioavailability of antiretroviral drugs. Multiple viral determinants, including entry via envelope glycoproteins, replication by reverse transcriptase, and virion maturation by protease activity, contribute to fitness in different cells and provide targets for current antiretroviral therapies. This review focuses on fitness of HIV-1 in macrophages and examines the impact of protease inhibitors on fitness of quasispecies and an unexplained discordance between fitness and pathogenesis.

Increased replication of non-syncytium-inducing HIV type 1 isolates in monocyte-derived macrophages is linked to advanced disease in infected children

Non-syncytium-inducing (NSI) strains of HIV-1 prevail among most infected children, including pediatric patients who develop advanced disease, severe immune suppression, and die. A study was designed to address the hypothesis that genotypic and/or phenotypic markers can distinguish NSI viruses isolated during early infection from NSI viruses found in advanced disease. Primary HIV-1 isolates, which were obtained from 43 children, adolescents, and adults who displayed a cross-section of clinical disease and immune suppression but were untreated by protease inhibitor antiretroviral therapy, were characterized for replication phenotype in different cell types. Most individuals (81%) harbored NSI viruses and almost half had progressed to advanced disease or severe immune deficiency. About 51% of NSI isolates produced low levels of p24 antigen (median, 142 pg/ml) in monocyte-derived macrophages (MDMs), 31% produced medium levels (median, 1584 pg/ml), and 17% produced high levels (median, 81,548 pg/ml) (p < 0.001). Seven of eight syncytium-inducing isolates also replicated in MDMs and displayed a dual-tropic phenotype that was associated with advanced disease. Replication of NSI viruses in MDMs varied as much as 100- to 1000-fold and was independent of replication in peripheral blood mononuclear cells. Replication in MDMs provided a clear biological feature to distinguish among viruses that were otherwise identical by NSI phenotype, V3 genotype, and CCR5 coreceptor usage. Low-level MDM replication was characteristic of viruses isolated from asymptomatic individuals, including long-term survivors. Enhanced MDM replication was related to morbidity and mortality among patients. Replication levels in MDMs provide a novel prognostic indicator of pathogenic potential by NSI viruses.

Timing of perinatal human immunodeficiency virus type 1 infection and rate of neurodevelopment. The Women and Infant Transmission Study Group

BACKGROUND

Identifying HIV-1-infected children who are at greatest risk for disease-related morbidities is critical for optimal therapeutic as well as preventive care. Several factors have been implicated in HIV-1 disease onset and severity, including maternal and infant host characteristics, viral phenotype and timing of HIV-1 infection. Early HIV-1 culture positivity, i.e. intrauterine infection, has been associated with poor immunologic, virologic and clinical outcomes in children of HIV-infected women. However, a direct effect of timing of infection on neurodevelopmental outcome in infancy has not yet been identified.

METHODS

Serial neurodevelopmental assessments were performed with 114 infants vertically infected with HIV-1 in a multicenter natural history, longitudinal study. Median mental and motor scores were compared at three time points. Longitudinal regression analyses were used to evaluate the neurodevelopmental functioning of children with early positive cultures and those with late positive cultures.

RESULTS

Early infected infants scored significantly lower than late infected infants by 24 months of age and beyond on both mental (P = 0.05) and motor (P = 0.03) measures. Early HIV-1 infection was associated with a decline in estimated motor scores of 1 standard score point per month compared with 0.28 point in the late infected group (P < 0.02). Estimated mental scores of the early infected group declined 0.72 point/ month, whereas the average decline of the late infected group was 0.30 point/month (P < 0.13).

CONCLUSION

Early HIV-1 infection increases a child's risk for poor neurodevelopmental functioning within the first 30 months of life.

Genetically and epidemiologically related "non-syncytium-inducing" isolates of HIV-1 display heterogeneous growth patterns in macrophages

The objective of this study was to identify phenotypic parameters that could distinguish among seemingly homogeneous non-syncytium-inducing (NSI) viruses and that might provide a surrogate marker for clinical progression in pediatric human immunodeficiency virus type 1 (HIV-1) infection. We undertook a pilot analysis of 15 independent HIV-1 isolates collected prospectively from two mothers and their four children who displayed a spectrum of disease stages ranging from CDC categories A1 to C3. Viruses were evaluated for their ability to replicate in primary cells (including monocyte-derived macrophages [MDM]) and cell lines, for their co-receptor preference and for genetic features of the V3 hypervariable domain of env. Virtually all isolates displayed NSI phenotypes that were restricted in their capacity to replicate in cell lines and displayed V3 loops with uniformly low net positive charges. NSI viruses from two symptomatic children and one mother were macrophage-tropic, whereas NSI isolates from two asymptomatic children were unable to replicate in MDM and were designated primary lymphotropic viruses. Only one isolate was syncytium-inducing (SI), replicated in a variety of cell lines and in MDM, used multiple co-receptors, and was dual tropic, rather than a mixture of T-cell tropic and M-tropic viruses, as assessed by genetic analysis. Phenotypic heterogeneity among NSI viruses is revealed in the ability of isolates to replicate in MDM. This characteristic is related to disease stage and provides a potentially new in vitro criterion to distinguish among NSI isolates that is unlinked to other surrogate markers.

Emerging recombinant human immunodeficiency viruses: uneven representation of the envelope V3 region

OBJECTIVE

To determine whether the envelope V3 region from HIV-1 subtypes A, C or D had the same probability of being present in intersubtype recombinant genomes.

MATERIALS AND METHODS

The envelope C2-C5 and the gag p24-p7 regions from one hundred infants infected perinatally in Tanzania were compared using phylogenetic and recombination analysis. Exact binomial and Fisher's exact tests were used to assess if various genomic regions were more likely to be overrepresented in intersubtype recombinants.

RESULTS

Of one hundred HIV-1 positive infants analyzed, twenty-two (22%) showed exclusively subtype A sequence in gag and env. Subtype C accounted for twenty-two infants (22%) whereas nineteen infants (19%) were infected by HIV-1 subtype D. Intersubtype recombinant genomes accounted for thirty-seven infections (37%). The V3 region from subtype A was found in all fifteen A-D recombinants (P = 0.00003) and the V3 region from subtype C was found in all twelve C-D recombinants (P = 0.0002). Conversely, subtype D gag sequences were preferentially represented in the gag of A-D recombinants (P = 0.0003) as well as C-D recombinants (P = 0.002). In A-D recombinants, the V3 region of subtype A was generally surrounded by subtype A C3-C5 sequences. In contrast, the V3 region from subtype C was surrounded by subtype D C3-C5 sequences in C-D recombinants. Significant differences were not found in the number of subtype A or subtype C sequences in A-C recombinants.

CONCLUSION

We have shown that several recombinant HIV-1 viruses have been generated and efficiently transmitted to infants in Tanzania. The recombination patterns showed that the V3 region of subtypes A or C was always selected in A-D and C-D recombinants. This selection suggests that the fitness of subtype D-V3 in perinatal transmission may be reduced with respect to V3 from subtype A and/or subtype C. The elevated number of recombinants transmitted perinatally suggests that co-infection or super-infection by two HIV-1 subtypes is not uncommon in this population.

Viral phenotype in mother-to-child HIV-1 transmission and disease progression of vertically acquired HIV-1 infection

Human immunodeficiency virus-1 (HIV-1) primary isolates differ in replicative capacity on peripheral blood mononuclear cells, tropism for primary monocyte-derived macrophages (MDM) and T-cell lines and syncytium-inducing (SI) capability on MT-2 cells in vitro. To assess the role of viral phenotype in mother-to-child HIV-1 transmission and the progression of vertically acquired HIV-1 infection, we studied 57 HIV-1-infected women at the time of delivery and 24 HIV-1-infected infants. Eight mothers transmitted the infection to their children. Primary isolates, obtained from 7 and 33 transmitting and non-transmitting mothers, respectively, differed in replicative capacity and SI activity, and no significant differences between the two groups were found regarding these viral properties. However, all primary isolates from transmitting mothers, but about half of those from non-transmitting mothers, were able to infect and replicate in MDM, regardless of their replicative capacity and/or SI activity; moreover, the monocyto-macrophage tropism of the maternal isolate correlated with an increased risk of transmission. Viral isolates from HIV-1-infected children were typed before 2 months of age; all but four showed a tropism for MDM, further supporting the notion that monocyto-macrophage tropic variants are selectively transmitted from mother to child and/or selectively replicated upon transmission. Clinical follow-up disclosed that 7/11 infants with a rapid/high replicating virus but none of the 17 with a slow replicating virus developed severe symptoms of disease and/or severe immunodepression by 1 year of age. By means of competitive RNA-polymerase chain reaction (PCR), a relationship was found between viral phenotype and dynamics of HIV-1 replication early in life in children who experienced different patterns of disease progression.

Immunological and virological markers of disease progression in HIV-infected children

Polymerase chain reaction (PCR), virus culture and antigen detection assays are useful for early detection of vertically transmitted human immunodeficiency virus type 1 (HIV-1) infection in infants under 12 months of age. Sixty-four children born to HIV-1-seropositive mothers were evaluated. Thirteen children (20.3%) were repeatedly positive by PCR analysis. There was 100% concordance between the results obtained from PCR and culture assays. Measurement of p24 antigen in serum was, in contrast, a less sensitive marker of HIV infection: only 5/13 infants had positive p24 antigen results. We have investigated the relationship among the HIV-1 biological phenotype, replicative capacity of viral isolates, HIV RNA copy number in plasma, p24 antigenaemia, CD4 T lymphocyte counts and the clinical status in 13 HIV-infected infants. Six out of 13 HIV-1 isolates from these patients were classified as rapid/high and seven as slow/low. We have found a significantly positive correlation between the replication rate of HIV isolates and their capacity to induce syncytia in vitro. The HIV-1 isolates with rapid/high and syncytium-inducing phenotype, and isolates with slow/low and non-syncytium-inducing phenotype were obtained from infants who had HIV-1 RNA copy number ml(-1) plasma values of 27654-83520 and 1342-34321, respectively. Levels of HIV-1 RNA were measured in sequential plasma samples from three HIV-infected infants and their biological properties determined in vitro. Our findings indicate that infants who carried viruses with more cytophatic biological phenotype and who had higher viral RNA copy numbers in blood were more likely to have lower CD4+ T cell counts and more likely to develop full-blown AIDS.

Relationship of virologic, immunologic, and clinical parameters in infants with vertically acquired human immunodeficiency virus type 1 infection

We have investigated the relationship among the HIV-1 biologic phenotype, replicative capacity of virus isolates, HIV-RNA copy number in plasma, p24 antigenemia, CD4+ T lymphocyte counts in peripheral blood, and the clinical status in a cohort of 13 HIV-infected children younger than 12 mo of age, born of HIV-1 seropositive mothers. Six out of 13 HIV-1 isolates from these patients were classified as rapid/high and seven as slow/low. We have found a significantly positive correlation between the replication rate of HIV isolates and their capacity to induce syncytia in vitro. Most of the serial HIV-1 isolates obtained from infants with AIDS had the rapid/high phenotype and induced syncytia, whereas only two out of 23 HIV-1 isolates obtained from infants without AIDS showed these properties. In sequential analysis of HIV-1 isolates from infants with AIDS, the presence of viral isolates with rapid/high and SI phenotype was associated with higher levels of HIV-1 RNA in plasma, CD4+ T cell depletion, and clinical progression. By contrast, infants whose viruses exhibited nonsyncytium-inducing phenotype throughout the follow-up showed lower levels of HIV RNA, stable CD4+ T cell counts, and mild symptomatic HIV infection. Our findings indicate that infants who carried viruses with more cytopathic biologic phenotype and who had higher viral RNA coy numbers in blood were more likely to have lower CD4+ T cell counts and more likely to have AIDS.

Very late presentation of vertically transmitted HIV-1 infection

We describe a 13-year-old boy with a very late presentation of vertically transmitted HIV-1 infection. The mother, an intravenous drug user before pregnancy, was diagnosed with AIDS in 1987 when the boy was 6 years old. HIV infection in her son was never suspected or investigated. No other risk factors for this infection can be attributed to the boy. On diagnosis of the infection the boy had moderately severe respiratory symptoms, as classified in category B2 of the 1994 paediatric HIV infection definition, and virological replicative kinetics and the phenotype have been determined. Standard AZT therapy has improved the clinical symptoms, with negativization of plasma p24 Ag and HIV RNA. Clinicians should be aware of this form of presentation of HIV-1 infection to avoid further delay of proper therapy.

Dynamics of viral replication in infants with vertically acquired human immunodeficiency virus type 1 infection

About one-third of vertically HIV-1 infected infants develop AIDS within the first months of life; the remainder show slower disease progression. We investigated the relationship between the pattern of HIV-1 replication early in life and disease outcome in eleven infected infants sequentially studied from birth. Viral load in cells and plasma was measured by highly sensitive competitive PCR-based methods. Although all infants showed an increase in the indices of viral replication within their first weeks of life, three distinct patterns emerged: (a) a rapid increase in plasma viral RNA and cell-associated proviral DNA during the first 4-6 wk, reaching high steady state levels (> 1,000 HIV-1 copies/10(5) PBMC and > 1,000,000 RNA copies/ml plasma) within 2-3 mo of age; (b) a similar initial rapid increase in viral load, followed by a 2.5-50-fold decline in viral levels; (c) a significantly lower (> 10-fold) viral increase during the first 4-6 wk of age. All infants displaying the first pattern developed early AIDS, while infants with slower clinical progression exhibited the second or third pattern. These findings demonstrate that the pattern of viral replication and clearance in the first 2-3 mo of life is strictly correlated with, and predictive of disease evolution in vertically infected infants.

Prognostic value of immunological data, in vitro antibody production, and virus culture in vertical infection with HIV-1

The prognostic value of immunological indices, in vitro antibody production, and virus culture pattern at 3 months of age was estimated in 35 infants infected by HIV-1 from a cohort of 298 babies born to HIV-1 seropositive mothers and followed up from birth. At 1 year old, 15 of these infants were classified as stage P-1 (according to the Centers for Disease Control classification) seven were P-2A, and seven had AIDS. Significantly higher CD8 percentages, lower percentages and absolute value of CD4, and lower CD4/CD8 ratios at 3 months were observed in infants with severe symptoms at 1 year of age when compared with those who were asymptomatic at this age. Seventy seven per cent of infants with a 'rapid' virus culture when 3 months old had developed AIDS or had died by 1 year of age and only 8% of those with 'slow' virus culture had AIDS when 1 year old. Moreover, 100% of those who were asymptomatic at 1 year had a slow virus culture at 3 months. Significant statistical association was found between the virus replication pattern at 3 months and the clinical stage at 1 year of age.

Broadly neutralizing, MN-like PND-directed antibodies in Rwandan children with long-term HIV1 infection

Sera from 11 perinatally HIV1-infected Rwandan children with prolonged survival were tested in vitro for the presence of neutralizing antibodies against different HIV1 strains. These 11 sera from long survivor (LS) children were compared with 16 sera from Rwandan children with AIDS. Sera from HIV1-infected children exhibited the greatest neutralizing activity against HIV1MN cell-free infection. They also inhibited HIV1RII and HIV1LAI cell-free infection with lower titres. Higher neutralization titres were observed in sera from LS compared to the AIDS group, with a significant difference for HIV1MN and HIV1LAI strains. Sera from LS children also inhibited syncytium formation induced by HIV1MN-infected cells with higher titres than AIDS children. Sera from the HIV1-infected children showed reactivity to the HIV1MN V3 peptide, as well as to both the US/European and the African consensus V3 peptides. Higher reactivity was observed in sera from LS than from AIDS children, and the difference was significant toward the African consensus peptide. The LS children also had significantly higher V3MN IgG avidity than the AIDS children. These data support the notion that the humoral response to the V3 domain, associated with a broadly neutralizing activity, may be an important factor in the prolonged survival of these children. The specificity against HIV1MN also suggests that an antigenically MN-related strain may be prevalent in Rwanda, and that an MN-related principal neutralizing domain sequence could be an important determinant for candidate vaccines in this part of Africa.

Relationship between the V3 loop and the phenotypes of human immunodeficiency virus type 1 (HIV-1) isolates from children perinatally infected with HIV-1

The third variable region (V3) of the envelope protein of human immunodeficiency virus type 1 (HIV-1) contains group- and type-specific epitopes for neutralizing antibodies and contains determinants involved in viral tropism and syncytium-inducing (SI) activity. We studied the in vivo relationship between V3 sequences and viral phenotypes in 24 perinatally HIV-1-infected children. To avoid in vitro selection of intrapatient minor variants, genetic studies were performed directly on uncultured peripheral blood mononuclear cells (PBMC), and the tropisms of HIV-1 isolates were evaluated by culturing patients' PBMC directly with monocyte-derived macrophages, lymphocytes, and MT-2 cells. According to their phenotypes, we could define five types of primary isolates: (i) non-syncytium-inducing (NSI) macrophagetropic, (ii) NSI macrophage-lymphotropic, (iii) NSI lymphotropic, (iv) SI lympho-T-cell line-tropic, and (v) SI pleiotropic. The SI viral phenotype was correlated with a more advanced status of disease. Genetic analysis of intrapatient molecular variants revealed that no relationship between the degree of intrapatient V3 variability and the pattern of viral tropism existed; moreover, within a single patient, the values for V3 variability between CD4+ lymphocytes and CD14+ monocytes were similar, thus suggesting that in vivo variability of the monocytotropic variants is more extensive than previously appreciated. A comparison between the intrapatient major variants and the phenotype of primary isolates disclosed that a negatively charged amino acid at residue site 25 was associated with an NSI macrophage- and macrophage-lymphotropic viral phenotype. Finally, by comparing the V3 sequences derived from our study population with those of several prototypes, we observed that the majority of isolates circulating in Italy are related to the North American subtype B macrophagetropic isolates.

Mother-to-child HIV-1 transmission: quantitative assessment of viral burden as a diagnostic tool and prognostic parameter in HIV-1-infected children

Polymerase chain reaction was performed in 251 infants born to HIV-1-seropositive mothers to diagnose HIV-1 infection. Assay specificity was invariably > 95%, regardless of age at testing, while sensitivity ranged from 15% in neonates (within 48 h of birth) to > 95% in infants over 1 month of age. Evaluation of viral burden in 43 infected infants by means of quantitative DNA-PCR disclosed that the number of HIV-1 proviruses ranged from 5 to 947 per 100,000 peripheral blood mononuclear cells. Clinical follow-up demonstrated that a high viral burden was associated significantly with disease onset.

HTLV-I and HTLV-II infections among HIV-1 seropositive patients in Sao Paulo, Brazil

To estimate the presence of, and the risk factors for HTLV-I and HTLV-II infections among HIV-1 infected subjects in Sao Paulo, Brazil, a serosurvey was performed in 471 HIV-1 infected patients, including 216 intravenous drug addicts (IVDA), 229 homosexual/bisexual men, and 26 with other risk factors. Serum samples were screened for HTLV seroreactivity by ELISA; reactive samples were analyzed by Western Blot (WB), using whole HTLV-I lysate as antigen. To confirm and discriminate HTLV-I and HTLV-II infections, sera presenting any bands on WB were further analyzed by a WB containing recombinant HTLV-I and HTLV-II proteins (WB 2.3), and by enzyme immunoassays using synthetic peptides specific for envelope proteins (Synth-EIA). In 22 cases, cell samples were available for polymerase chain reaction (PCR) studies. On WB, 114 sera were reactive and, of these, 37 and 25 were concordantly positive on both WB 2.3 and Synth-EIA procedures for HTLV-I and HTLV-II specific antibodies, respectively; 37 specimens were negative on both assays, and 15 gave discordant or indeterminate results. PCR findings confirmed concordant results obtained in the discriminatory serological assays. The prevalence rates of HTLV-I and HTLV-II infections were 15.3% and 11.1% in IVDA, and 0.9% and 0.4% in homosexual/bisexual men, respectively. No case of HTLV-I/HTLV-II co-infection was found.

Persistence of multiple maternal genotypes of human immunodeficiency virus type I in infants infected by vertical transmission

The extent of nucleotide variation within the HIV-1 env hypervariable domains serves as a marker of virus genotypes within infected individuals and as a means to track transmission of the virus between individuals. We analyzed env V1 and V2 sequences in longitudinal samples from two HIV-1-infected mothers, each with three children infected by maternal transmission of the virus. Sequences in samples that were obtained from two infants at 2 d and 4 wk after birth displayed more variation in V1 and V2 than maternal samples obtained at the same times. Multiple HIV-1 genotypes were identified in each mother. In each family, multiple maternal HIV-1 genotypes were transmitted to the infants. Specific amino acid residues in the hypervariable domains were conserved within sequences from each family producing a family-specific amino acid signature pattern in V1 and V2. Viruses that were highly related to maternal viruses in signature pattern persisted for as long as 4 yr in the older children. Results support a model of transmission involving multiple HIV-1 genotypes with development of genetic variation from differential outgrowth and accumulation of genetic changes within each individual.

Replication and tropism of human immunodeficiency virus type 1 as predictors of disease outcome in infants with vertically acquired infection

In a series of 97 infants born to mothers who were seropositive for human immunodeficiency virus type 1 (HIV-1), 18 were identified as infected within the first 60 days of life on the basis of viral culture and polymerase chain reaction findings. We studied viral burden in vivo by quantitative polymerase chain reaction and the in vitro replication pattern of the HIV-1 infecting strain by culturing patient cells with normal phytohemagglutinin-stimulated peripheral blood mononuclear cells. According to the lag phase before p24 antigen detection and the level of p24 production on peripheral blood mononuclear cells, HIV-1 isolates from these patients were classified as rapid/high (R/H), slow/high (S/H), and slow/low (S/L). The pattern of HIV-1 replication in vitro was significantly associated with the viral burden in vivo; the range of HIV-1 copies per 10(5) peripheral blood mononuclear cells was 10 to 38, 44 to 314, and 360 to 947 in children with isolates of the S/L, S/H, and R/H types, respectively. Viral tropism was assessed by culturing patient cells under end-point dilution conditions with either CD4+ T-lymphocytes or monocyte-derived macrophages. We found that children with S/L isolates harbored mainly monocytotropic variants; all infants with S/H or R/H isolates had T-lymphotropic variants and, in 7 of 11 cases, monocytotropic or amphitropic variants. All children with R/H isolates had HIV-related symptoms by the age of 4 months, and five had acquired immunodeficiency syndrome by the age of 1 year. At 1 year of age, four and no infants with S/H or S/L isolates, respectively, had HIV-1-related symptoms (p < 0.001), and none had acquired immunodeficiency syndrome (p = 0.006).

Pattern of antibody response against the V3 loop in children with vertically acquired immunodeficiency virus type 1 (HIV-1) infection

The principal neutralizing domain (PND) of HIV-1, located within the third variable region (V3) of the gp120 envelope protein, is related to the humoral and cellular immune response. We studied the V3 PND-specific antibody response in 30 children with vertically acquired HIV-1 infection by determining the antibodies that bound synthetic peptides derived from the PND of the HIV-1MN, HIV-1SF-2, HIV-1SC, HIV-1IIIB, HIV-1RF, HIV-1ELI, and HIV-1Z6 virus strains. At a standard antigen concentration, we found that most sera (90%) reacted against PNDMN peptide, but 73.3% also cross-reacted against multiple PNDs. A search for high-affinity/avidity antibodies was conducted in an antigen-limited assay; at lower peptide concentrations, cross-reactivity was restricted to PNDMN and PNDSC in 12 of 22 broadly reactive sera. Sequence analysis of the V3 region of HIV-1 isolates indicated that patients with high-affinity/avidity antibodies to PNDMN and PNDSC had a PND with an internal 12-amino acid sequence (serotype-specific domain, SSD) that was highly homologous (> 90%) with the MN and SC SSD. Broadly reactive sera with low-affinity/avidity antibodies showed a lower degree of homology with the SSD sequence of all tested viral strains. The role of anti-PND antibodies in vertical transmission was further studied in 49 children born to HIV-1-seropositive mothers. No statistical correlation emerged between V3 antibodies and HIV-1 transmission, but we found that maternal V3 antibodies were lost soon after birth. This finding may be relevant to a new serological approach to the early diagnosis of vertically transmitted HIV-1 infection.

Molecular profile of human immunodeficiency virus type 1 infection in symptomless patients and in patients with AIDS

Recent molecular evidence indicates that active human immunodeficiency virus type 1 (HIV-1) infection is detectable in both symptomless and symptomatic infected patients. For this main reason, it has been pointed out that precise quantitative analysis of viral activity in vivo is necessary, firstly, for the pathogenetic investigation of the steps relevant to infection progression and, secondly, for better clinical management of HIV-1-infected patients. In this study, the presence of HIV-1 genomic RNA in plasma samples, specific HIV-1 transcripts in peripheral blood mononuclear cells, and proviral DNA sequences were assayed for 33 HIV-1-infected patients (including symptomless and symptomatic subjects) by using a competitive polymerase chain reaction method that allows quantitation of the RNA/DNA target sequences. The quantitative results obtained confirm that transcription of HIV-1 structural genes and complete viral replication occur in all the HIV-1-infected patients independently of the clinical stage. However, although sharp individual differences were detected, a high degree of correlation of the molecular parameters studied with both disease progression and a decrease in the number of CD4+ T lymphocytes was documented. Interestingly, despite the increasing viremia level associated with infection progression, the mean transcriptional activity of individual infected cells was found to be only moderately greater in AIDS patients than in asymptomatic infected subjects. In addition, it was noted that quantitation of HIV-1 genomic RNA in plasma samples and quantitation of specific HIV-1 transcripts in peripheral blood mononuclear cells appear to be more reliable and sensitive markers of viral activity than quantitative analysis of proviral HIV-1 sequences in peripheral lymphocytes.