Human-immunodeficiency-virus infections in infants negative for anti-HIV by enzyme-linked immunoassay

A dual-mode RNA-splitting aptamer biosensor for sensitive HIV Tat peptide detection via colorimetry and fluorescence

Early diagnosis of human immunodeficiency virus (HIV) is critical for effective treatment; however, traditional antibody methods encounter challenges during the infection window, and nucleic acid tests require specialized equipment. In this study, a dual-mode ribonucleic acid (RNA)-splitting aptamer biosensor was developed to target the HIV trans-activator of transcription (Tat) protein, a key HIV biomarker for viral replication throughout the infection cycle. The biosensor integrates colorimetric and fluorescent detection techniques by utilizing gold nanoparticles (AuNPs) and two types of aptamers, one labeled with carboxyfluorescein (FAM). In the presence of Tat, RNA-splitting aptamers adsorb onto AuNPs, protecting them from recombination, while the fluorescence of FAM is quenched via fluorescence resonance energy transfer (FRET). Aptamers form a ternary complex with Tat, preventing adsorption and leading to thioflavin T-induced aggregation of AuNPs, accompanied by a visible color change and fluorescence signal restoration. The biosensor demonstrated excellent sensing performance, with a linear range of 0.5-60 nM and a detection limit of 0.28 nM, successfully detecting Tat in human serum. Therefore, this low-cost dual-mode detection platform offers a promising tool for early HIV diagnosis and potential applications in clinical and point-of-care fields.

High-throughput single molecule screening of DNA and proteins

We report a novel imaging technology for real time comprehensive analysis of molecular alterations in cells and tissues appropriate for automation and adaptation to high-throughput applications. With these techniques it should eventually be possible to perform simultaneous analysis of the entire contents of individual biological cells with a sensitivity and selectivity sufficient to determine the presence or absence of a single copy of a targeted analyte (e.g., DNA region, RNA region, protein), and to do so at a relatively low cost. The technology is suitable for DNA and RNA through sizing or through fluorescent hybridization probes, and for proteins and small molecules through fluorescence immunoassays. This combination of the lowest possible detection limit and the broadest applicability to biomolecules represents the final frontier in bioanalysis. The general scheme is based on novel concepts for single molecule detection (SMD) and characterization recently demonstrated in our laboratory. Since minimal manipulation is involved, it should be possible to screen large numbers of cells in a short time to facilitate practical applications. This opens up the possibility of finding single copies of DNA or proteins within single biological cells for disease markers without performing polymerase chain reaction or other biological amplification.

Single-molecule immunoassay and DNA diagnosis

Many assays relevant to disease diagnosis are based on electrophoresis, where the migration velocity is used for distinguishing molecules of different size or charge. However, standard gel electrophoresis is not only slow but also insensitive. We describe a single-molecule imaging procedure to measure the electrophoretic mobilities of up to 100000 distinct molecules every second. The results correlate well with capillary electrophoresis (CE) experiments and afford confident discrimination between normal (16.5 kbp) and abnormal (6.1 kbp) mitochondrial DNA fragments, or beta-phycoerythrin-labeled digoxigenin (BP-D) and its immunocomplex (anti-D-BP-D). This demonstrates that virtually all electrophoresis diagnostic protocols from slab gels to CE should be adaptable to single-molecule detection. This opens up the prossibility of screening single copies of DNA or proteins within single biological cells for disease markers without performing polymerase chain reaction (PCR) or other biological amplification.

Semiquantitative human immunodeficiency virus antibody tests in diagnosis of vertical infection

OBJECTIVE

This study evaluated the roles of semiquantitative anti-HIV antibody tests for early diagnosis of vertical HIV-1 infection in infants.

METHODS

The study included 0- to 18-month-old children of HIV-1-infected mothers. They were regularly followed up, and blood was obtained for semiquantitative anti-HIV tests using a particle agglutination (PA) test and a microparticle enzyme immunoassay (MEIA).

RESULTS

One hundred forty-six children of HIV-1-infected mothers, including 104 infected and 42 uninfected infants, were studied. Using anti-HIV titer of < or = 1:100 by PA and optical values of < or = -3 by MEIA for diagnosis of not being infected, approximately 69 and 53% of the uninfected cases at age 7 to 8 months, 76 and 67% at age 9 months and 100% at age 12 months could be diagnosed. By comparison with the diagnosis by qualitative tests the figures were 16%, 8 and 11%, 70 and 74% at the same ages. All asymptomatic HIV-infected cases had persistently high PA titers and MEIA values of at least 1:5000 and 6, respectively, but 7 cases with AIDS-related manifestation at the time of tests had low anti-HIV titers. One severely ill, HIV-infected infant had a transient negative anti-HIV test at the age of 7 months. Two asymptomatic infected children, who had been breast-fed, had transient decrease in anti-HIV titers after the age of 6 months, and transient seroreversion occurred in one. CONCLUSION. Semiquantitative anti-HIV tests between the age of 6 to 12 months were very useful in diagnosis of HIV-1 infection in infants born of HIV-1-infected mothers. Interpretation must be accompanied by information about AIDS-related manifestation and history of breast-feeding.

A multicentre quality assessment study to monitor the performance of HIV-1 PCR

Eleven German laboratories and one Swiss laboratory initiated a quality assessment study to evaluate the specificity and sensitivity of their polymerase chain reaction (PCR) for detection of HIV-1 DNA. Following its own PCR protocols, each laboratory tested a panel of ten coded samples consisting of cell pellets containing 0, 0.1, 1, 10, 10(2), 10(3) and 10(4) ACH-2 cells per 1.5 x 10(5) uninfected peripheral blood mononuclear cells. Of the twelve participating laboratories, three reported correct results for the dilution series as well as for uninfected specimens. One or more classification errors were recorded for 12% of the samples for which the diagnosis was expected to be positive or negative. Samples containing 10 copies of the target template were correctly reported by eleven of the twelve participants. The average sensitivity was 97%. The results of the study revealed no significant differences between the Amplicor kit and in-house procedures. Most of the classification errors occurred in specimens from HIV-negative samples. Out of 36 negative samples, 5 were reported false positive, showing that contamination remains a problem for some laboratories, regardless of the PCR test performed. Careful laboratory techniques and internal as well as external quality control procedures will help avoiding carryover contamination.

Immune stimulation may contribute to enhanced progression of SIV induced disease in rhesus macaques

A number of rhesus macaques experimentally infected with SIV isolates such as SIVmac251, fail to seroconvert, develop high plasma viremia and die rapidly (within 6-7 months p.i.). We hypothesized that such rapid progression is a result of a state of hyperimmune activation and concomitant immune suppression of these animals at the time of virus challenge. In efforts to test the hypothesis that immune activation leads to rapid progression of lentivirus-induced disease, adult rhesus macaques were infected with SIV mac251 and received an alternate monthly schedule of repeated immunization with allogeneic cells, keyhole limpet hemocyanin and tetanus toxoid (group I). For purposes of controls, a group of monkeys was infected with the same pool and dose of virus but were not immunized (group II) and a group was immunized with the same schedule of multiple antigens as group I but were not infected with SIV (group III). All the animals in group I (n = 3) either failed to seroconvert or developed very low levels of SIV antibodies, had high plasma p27 defined antigenemia, and died within 8 months (2/3 died within 4 months). Of the animals in group II (n = 8), two patterns emerged as we had noted before. One subgroup (3 animals), displayed the same profile as group I (failure to fully seroconvert, high p27 levels and death by 8 months), whereas the other subgroup (5 animals) seroconverted, had low plasma p27 levels, and survived past 11 months (2/5 still alive past 22 months). All 3 animals in group III remained healthy. The data provided herein suggest that either experimental or natural (due to factors not clear at present) immune stimulation may lead to accelerated lentivirus induced disease progression most likely due to immune suppression and has implications for the understanding of the mechanisms for the rate of disease progression in human HIV-1 infection.

Evaluation and medical treatment of the HIV-exposed infant. American Academy of Pediatrics. Committee on Pediatric AIDS

As a result of the expanding human immunodeficiency virus (HIV) infection epidemic and recently published recommendations for routine HIV testing with consent for all pregnant women in the United States, pediatricians are becoming increasingly involved in providing care to infants born to HIV-infected women. This article provides guidelines about counseling the parent or care giver of the infant, use of antiretroviral therapy to reduce the risk of infection in the infant, medical treatment of the HIV-exposed infant, laboratory testing to determine the infection status of the infant, laboratory monitoring of hematologic and immunologic parameters, prophylaxis for Pneumocystis carinii pneumonia, and recommendations for immunizations and tuberculosis screening.

Detection of virus in vertically exposed HIV-antibody-negative children

BACKGROUND

HIV-infected mothers can transmit their infection to their children in utero or at delivery (vertical transmission). There have been cases of children who were reported as acquiring infection vertically and later clearing the infection. We report the frequency of this phenomenon in a European cohort study.

METHODS

In four centres of the European Collaborative Study of children born to HIV-infected mothers, 299 children became HIV-antibody-negative and 264 of these had been followed up with virus culture and PCR for viral DNA at least once.

FINDINGS

Nine of the 264 children were positive by virus culture or PCR, and subsequently seroreverted. Two of the nine tested virus-positive after they became antibody-negative. Six cases were virus-positive early in life and became negative thereafter, which is consistent with clearance of infection. The pattern was less clear in the other three. The nine cases had had their last virus test at age 16-101 months. All nine children had been bottlefed only. Eight had been delivered vaginally. The children had no HIV-related symptoms and received no anti-HIV treatments. Based on only those children who had two or more positive virological tests, we estimate that 2.7% (6/219) cleared or "tolerated" the virus.

INTERPRETATION

The detection of virus or viral DNA in "uninfected" children born to HIV-infected mothers was rare and was not associated with clinical disease or immunological abnormalities. The timing of samples will affect the documentation of clearance since, in uninfected children of HIV-positive mothers who cleared the virus, viraemia was intermittent. Current paediatric opinion is to inform parents of children who serorevert that the child is not HIV-infected.

Virus isolation, polymerase chain reaction and in vitro antibody production for the diagnosis of pediatric human immunodeficiency virus infection

Viral culture (VC), polymerase chain reaction (PCR) and in vitro antibody production (IVAP) by peripheral blood mononuclear cells were compared for the early diagnosis of HIV-1 infection in 46 infants born to HIV-1 seropositive mothers. The ten children considered infected on the basis of clinical signs and persistence of anti-HIV-1 antibodies had at least one positive viral culture and seven were always positive in both PCR and IVAP tests. PCR and IVAP tests were occasionally negative in three infected children. Among 30 healthy children who became seronegative and were always negative for viral culture, 22 (73.3%) were also repeatedly negative in PCR and IVAP. We report 6 cases of children classified as P2A at the term of this study but who had lost anti-HIV-1 antibodies. They presented at least one positive viral culture and occasional positive PCR and/or IVAP results. The results indicate that the combination of viral culture, PCR and IVAP tests improves the early diagnosis of pediatric HIV infection.

Laboratory methods for early detection of human immunodeficiency virus type 1 in newborns and infants

Cumulative data on serological testing of newborns and infants have shown that (i) maternal and newborn anti-HIV-1 IgG titers are high at delivery, which may explain the persistence of antibody in the infants of seropositive mothers; (ii) in some situations, serial HIV-1 antibody testing may identify infected infants; and (iii) detection of anti-HIV-1 IgA or IgM is specific for infection but the sensitivity of this assay may be compromised in certain situations, such as when infected infants are hypogammaglobulinemic or when the rise and fall of HIV-1-specific IgM synthesis following acute infection has been completed before delivery of the infant. Cumulative data on PCR, viral culture, and tests for antigen in newborns and infants have shown that (i) among all age groups, viral culture is probably the most specific test available for detection of HIV-1, as PCR and the p24 antigen test may (though rarely) give false-positive results; (ii) the sensitivity of these tests increases in the order of antigen, culture, and PCR, with relatively insensitive results in the first 3 months of life for all of these tests; (iii) the sensitivity of all of these tests improves and approximates 90 to 100% when infants over 6 months of age are tested; and (iv) data regarding the sensitivity, specificity, and usefulness of these virological assays in infants under 3 months of age are very scant and inconclusive.

Detection of IgA and IgM antibodies to HIV-1 in neonates by radioimmune western blotting

OBJECTIVE

To detect infection with HIV-1 by IgA and IgM response at birth in children born to HIV-1 seropositive mothers.

DESIGN

Western blotting and radioimmune western blotting on stored sera from infected and uninfected babies born to HIV-1 seropositive mothers. Sera were pretreated to remove IgG.

SETTING

Parma and Bologna, Italy.

SUBJECTS

12 infected and five uninfected babies born to HIV-1 seropositive mothers and three babies born to seronegative mothers.

MAIN OUTCOME MEASURES

Effectiveness of western blotting and radioimmune western blotting in detecting antibodies to HIV-1 gene products.

RESULTS

With conventional western blotting we found IgA class antibodies to HIV-1 proteins in serum from three out of 12 infected children; in two of these three the serum was collected at age 3 months (positive controls). Radioimmune western blotting detected both IgA and IgM antibodies in serum from all infected children tested, whereas all serum from uninfected children born to seropositive and seronegative mothers showed no such antibodies.

CONCLUSION

Although the technique should be tested on more patients, radioimmune western blotting seems to be a valuable tool for serological diagnosis of congenital HIV-1 infection at birth in neonates born to seropositive mothers.

Epidemiology of vertically transmitted HIV-1 infection in Switzerland: results of a nationwide prospective study. Swiss Neonatal HIV Study Group

A nationwide study involving 286 children of human immunodeficiency virus (HIV)-infected mothers living in Switzerland has been performed with the participation of all paediatricians interested in HIV infection in the country. Of these children 201 could be followed up prospectively from birth up to a median age of 22 months. Prevalence of HIV infection in Swiss parturients was estimated at 0.1% and apparently remained stable from 1986 to 1989. Vertical transmission rate was estimated at 14%-20%. Variables of maternal or perinatal history were not associated with transmission rate. Transmission to pairs of siblings of the same mothers was discordant in 33% (6 of 18), with always the elder sibling being infected. Postneonatal mortality in infants of HIV-infected mothers followed up from birth was increased 15-fold over the general population with a very high incidence (2 in 100) of sudden infant death apparently unrelated to HIV infection.

Detection of human immunodeficiency virus type 1 provirus in mononuclear cells by in situ polymerase chain reaction

BACKGROUND

Studies of human immunodeficiency virus type 1 (HIV-1) infection have attempted to quantitate the viral load correlate it with the degree of immune deficiency. In one study, only about 1 in 10,000 peripheral-blood mononuclear cells (PBMC) expressed HIV-1, but in other studies, at least 1 in 100 CD4-positive cells was infected and harbored the HIV-1 provirus.

METHODS

We developed a new, highly sensitive in situ polymerase-chain-reaction (PCR) method that amplifies selected genetic regions within intact single cells. We used this technique to determine the proportion of PBMC carrying HIV-1 provirus in infected patients in different stages of disease.

RESULTS

None of the PBMC from 11 HIV-1--seronegative patients were found to be positive for HIV-1 provirus by the in situ PCR method. In 56 patients infected with HIV-1, the percentage of PBMC with HIV-1 ranged from 0.1 percent to 13.5 percent. The mean percentage of infected mononuclear cells was greater in 13 patients with persistent generalized adenopathy (mean, 6.6 percent) and 19 with the acquired immunodeficiency syndrome (Stages IV-A to IV-C) (4.6 percent) than in 19 patients with asymptomatic HIV-1 infection (0.9 percent) (P less than 0.001). However, in five patients with Kaposi's sarcoma (Stage IV-D), an average of only 1.6 percent of mononuclear cells were infected.

CONCLUSIONS

In HIV-1 infection, the proportion of PBMC that are infected appears to be at least 10 times higher than previously described. It is likely that most infected cells contain HIV-1 provirus in a latent or defective form that was not detected in some earlier studies.

Oral manifestations of HIV infection in children

Human immunodeficiency virus (HIV) infection was first recognized in children in 1983 and has now assumed the proportions of a major public health challenge. This article briefly reviews, on the basis of the literature, the epidemiology, diagnosis, clinical and immunologic characteristics, and prognosis of HIV infection in children. The clinical oral manifestations in children are described on the basis of the literature and the personal observations of HIV-infected pediatric patients.

Immunological follow-up in children born to HIV-1 infected mothers

From November 1985 to January 1990 we examined 156 children born to 154 HIV-1 seropositive mothers every 3 months. Eighty-seven infants were over 18 months by January 1990. Six of them met the CDC criteria of HIV-1 infection or died from AIDS; a transmission rate of 7%. Six of the children aged less than 18 months also met the CDC criteria of HIV-1 infection. These 12 infected children were compared with the 81 presumably unifected children. The perinatal findings were similar in both groups. Most of the HIV-1 infected babies showed early abnormalities in humoral and cellular immunity, hypergammaglobulinemia, low percentage of CD4 circulating lymphocytes and increased spontaneous in vitro immunoglobulin production. These changes were persistent in the HIV-1 infected children, but sporadic in those uninfected. Immunological abnormalities were frequently found before clinical symptoms appeared. We conclude that repeated immunological abnormalities in babies born to HIV-1 seropositive mothers are suggestive of HIV-1 infection.

Frequent and early in utero HIV-1 infection

We have investigated in utero human immunodeficiency virus type 1 (HIV-1) transmission by analyzing human fetal tissues for the presence of viral DNA by means of the polymerase chain reaction (PCR). Thirty three fetal samples: thymus, spleen, and peripheral mononuclear blood cells (PMBC) were obtained at abortion (16 to 24 weeks) from HIV-1-infected asymptomatic women. The results of HIV-1-DNA detection were considered only in 9 cases where contamination of fetal samples by infected mother cells could be definitely eliminated by using primers specific for a polymorphic cellular locus. PCR allowed the identification of HIV-1 DNA sequences in 6/8, 8/9, and 5/9 of specimens from thymus, spleen, and PMBC, respectively. Positive results were shown in fetuses as early as 16 weeks. Viral cultures as well as assays for serum p24 HIV-1 antigen were negative in 9.9 and 33/33 tested, respectively. Therefore, our results indicate early and frequent in utero HIV-1 infection. Different patterns of viral activation after birth might then lead to either rapid or delayed onset of acquired immunodeficiency syndrome.

Pediatric HIV disease. The newest chronic illness of childhood

HIV disease has emerged as a major chronic illness of childhood. Children with HIV infection and children with other chronic health impairments have much in common, including the need for comprehensive, multidisciplinary, coordinated care that includes special attention to the psychosocial effects on the child and family. However, because the mother and often the father and siblings share this lethal viral infection, the impact of HIV disease upon the family surpasses that of virtually all other chronic conditions. This is compounded by the association of the disease with drug use, its preponderance among the most disenfranchised populations in the United States, and the persistent public fear and discrimination surrounding AIDS. We have made substantial progress already in the medical management of this infection, and while we await the development of more effective therapies, we already have the tools and knowledge in hand to help these families.

Laboratory diagnosis of HIV infection

Laboratory diagnosis of human immunodeficiency virus (HIV) infection is complicated by absence of data on sensitivity, specificity and predictive value of the various tests as they apply to children. The presence of maternal anti-HIV passively transmitted across the placenta also confounds diagnosis. The authors review currently available data on the detection of HIV, HIV genome, and HIV gene products, as well as the diagnostic value of detecting serologic and cellular responses to HIV in infants and children.

HIV-1 infection in a cohort of haemophilic patients

The course of HIV infection in 53 haemophilic patients aged 5-20 years was evaluated by clinical examination and laboratory tests. During the evaluation time (median 30 months) two patients died of AIDS and 32 patients (60%) deteriorated when assessed by the Brodt-Helm classification. Nineteen patients (37%) had decreased absolute helper cell counts (less than 500 CD4 positive cells/microliters), and 45 patients (87%) had reduced helper cell to lymphocyte ratios (less than 0.35). HIV-1 was isolated from peripheral lymphocytes in 29 of 46 patients. As the disease progressed the number of positive viral cultures increased. Considerable progression of the HIV infection was seen in haemophilic children and adolescents during the median evaluation period of 30 months. The transition from symptomless HIV infection to immunodeficiency was easily recognised. A lowered ratio of helper cells to lymphocytes seems to be a useful marker of the beginning of the deterioration of the immune system.

Cost-effectiveness of HIV screening of pregnant women in hospitals of the Paris area. The Paris-Tours study group of antenatal transmission of HIV, Group '9 maternites'

In the context of an epidemiologic multicentric study about perinatal transmission of HIV, screening was systematically proposed to all pregnant women attending nine maternities clinics of the Paris region (n = 7600, between August 1987 and July 1988) at their first prenatal visit. Among them, 2145 had already been tested and 45 were known to be HIV positive. So, 5660 tests were performed during the first 6 months (period 1), and 17 pregnant women were discovered to be positive. The total cost of screening has been estimated between FF. 720,000 and 775,000, resulting in a mean cost per pregnant woman found to be HIV positive of about FF. 42,000 to 45,000. A similar calculation over the following 5 months (period 2) gave a mean cost of between FF. 165,000 and 178,000. Since the women, before being screened, had to answer a short questionnaire about risk factors; cost and effectiveness of a selective screening strategy could be simulated. The preference of systematic screening to selective screening enabled the discovery of two HIV positive cases in each period, the marginal cost, i.e., cost per extra pregnant woman found to be HIV positive was thus FF. 303,320 to 327,540 for period 1, and FF. 572,240 to 619,000 for period 2. Although these figures seem high, an estimation of the cost-effectiveness does not allow us to conclude whether it is in society's interest to devote the funds necessary to move away from selective screening towards systematic screening.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of anti-HIV IgA in tears of children born to seropositive mothers is highly specific

In order to improve the diagnosis of HIV infection in children born to seropositive mothers, 86 children were previously tested by Western blotting for anti-HIV IgA in tears and IgG in serum, at a median age of 9.2 months. To determine the exact value of the assay, 68/86 children of the same cohort were retested 9 months later. Nine children (13.4%) were seropositive and all had anti-HIV IgA in tears. Eight of them had possessed lachrymal antibodies 9 months earlier. The ninth child was seronegative when 9 months old and then seroconverted. Four children (6%), known to be seronegative, had an indeterminate Western blot pattern and no HIV IgA in tears. Fifty four (80.6%) were seronegative at 18 months; none of them had ever had anti-HIV IgA in tears. This highlights the fact that only the children without lachrymal HIV IgA at the age of 9 months became seronegative at the age of 18 months. Our results clearly show that the detection of anti-HIV IgA in tears is a highly specific and reliable diagnostic test in children aged less than 15 months, born to seropositive mothers.

HIV-1 infection in HIV-1 enzyme-linked immunoassay seronegative patients in Kinshasa, Zaire

Serum samples of 62 African patients who had clinical manifestations of HIV-1 infection but were seronegative for HIV-1 by ELISA (Organon) were subsequently further tested by another HIV-1 ELISA test (Wellcozyme), HIV-1 IgG Western blot, HIV-1 antigen detection and HIV-2 ELISA. Patients' lymphocytes were cultured for HIV-1 and 2. Because of limited quantities of serum available all tests were not performed on all samples. Seven (26%) of 27 sera of patients meeting the WHO clinical case definition of AIDS were Western-blot-positive. In contrast, of 35 patients' sera with possible HIV related disease, only one (3%) was Western blot positive (P = 0.02) and none of 75 sera from HIV-1 ELISA (Organon) seronegative blood donors (P less than 0.01) were Western blot positive. Of 30 HIV-1 ELISA (Organon) seronegative patients tested with the HIV-1 ELISA Wellcozyme assay only one was seropositive (this patient's serum was also Western blot positive). Of 17 HIV-1 ELISA (Organon) seronegative patients tested, HIV-1 antigen was found in 1 case (6%) (this patient's serum was Western blot negative). None of the 34 patients tested by HIV-2 serology was HIV-2 seropositive. HIV-1 was isolated by culture in 3 (21%) of 14 HIV-1 ELISA seronegative patients (sera of the 3 patients were Western blot negative). In total, 12 (19%) of 62 HIV-1 ELISA (Organon) seronegative patients were found to be positive for HIV, either by Western blot HIV antigen testing or viral culture.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative study of virus isolation, polymerase chain reaction, and antigen detection in children of mothers infected with human immunodeficiency virus

We report on an investigation designed to compare the polymerase chain reaction (PCR) with culture and p24 measurement for the diagnosis of human immunodeficiency virus (HIV) infection in infants and children. Forty-five children born of mothers with antibodies to HIV type 1 were studied; P24 antigen was measured in plasma, and HIV-1 proviral DNA was sought in peripheral blood mononuclear cells after amplification by PCR. In 26 cases, blood specimens were cultured for HIV; in all but two instances cultures were established at the same time that the PCR test was performed. Primer pairs in three regions of the proviral genome were used for the PCR test. There was good agreement between the results obtained from PCR tests and from cultures; of 24 children in whom both tests were done at the same time, 10 had positive results on both the culture and the PCR test, 1 had positive results on the PCR test but negative culture results, and 13 had negative results on both tests (concordance 96%). Measurement of p24 antigen in plasma was, in contrast, an insensitive marker of infection: 6 of 12 infants with positive cultures had positive p24 test results, and 8 of 18 infants had positive PCR test results. Sixteen children with subsequent seronegativity for HIV-1 had negative PCR results. This study provides further evidence that the PCR test is a valid alternative to viral culture for the diagnosis of pediatric HIV infection.

Detection of HIV RNA by in situ hybridization in peripheral blood mononuclear cells of seronegative children born to HIV-infected mothers

Of 44 children born to human immunodeficiency virus (type 1) (HIV)-infected mothers, 11 have become seronegative. After the loss of maternal antibodies all children were analysed for several immunological functions and virological parameters in order to determine their HIV status. All children to date are clinically healthy and have normal immune functions. HIV-1 was detected by p24 antigen in one child, by in situ hybridization in nine children while viral cultures were all negative. These data suggest that the rate of vertical transmission of HIV-1 may be underestimated if seronegative children are considered to be not infected. They also suggest that molecular biological techniques are more sensitive than HIV antigen assay or viral cultures.

Pharmacokinetics of azidothymidine during late pregnancy in Long-Evans rats

Azidothymidine (Zidovudine) is used to treat symptomatic human immunodeficiency virus infection. It has the ability to reverse seropositivity as well as decrease serum viral titers, and perhaps decrease potential for transmission of the virus. An animal model (pregnant Long-Evans rats) was used to investigate the potential for placental transmission of azidothymidine. The drug crosses the placenta to reach concentrations in the placenta and fetus that are comparable to 75% and 58%, respectively, of those in the maternal serum by 2 hours after administration. By 4 to 6 hours after administration azidothymidine concentrations in the placenta and fetal liver significantly exceed maternal concentrations.

Sensitivity and specificity of pooled versus individual sera in a human immunodeficiency virus antibody prevalence study

We evaluated the efficacy of testing pooled versus individual sera for the detection of human immunodeficiency virus antibody. A total of 5,000 individual specimens and 500 pools of 10 specimens each were assayed by an enzyme-linked immunosorbent assay. There was complete agreement in human immunodeficiency virus enzyme-linked immunosorbent assay reactivity for pooled versus individual specimens. An estimated savings of 60 to 80% (labor and supplies) can be realized dependent upon pooling and assay format.

Vertical transmission of HIV: a prospective study

Forty nine infants of HIV seropositive women were followed up for a median of 24 months, together with 24 controls. The infection status of 11 index children under 18 months of age was indeterminate; 34 were presumed uninfected while four showed clinical and laboratory evidence of HIV disease. Based on current definitions of HIV infection and excluding children under 18 months old as well as those who had not been studied from birth, two out of 28 children were infected. The estimated rate of maternofetal transmission was therefore 7.1%. In children with proved infection, sequential laboratory data showed that hypergammaglobulinaemia was noted as early as 6 months and often predated clinical signs. This observation, in the presence of non-specific clinical findings, was helpful in alerting the paediatrician to a diagnosis of HIV infection.

Anti-HIV antibody testing: procedures and precautions

Prudent use of screening tests for infection with human immunodeficiency virus (HIV) and interpretation of test results require an understanding of the body's immune response to HIV infection, the serologic assays currently available, and the problems associated with false-positive and false-negative test results. The methodologies of the enzyme immunoassay (enzyme-linked immunosorbent assay [ELISA]) and the Western blot assay are presented, and efficacies of these tests are evaluated. Tests for the detection of anti-HIV antibodies that are, at this time, primarily restricted to research use but that show promise for adaptation to screening (such as the ELISA with recombinant antigen) also are discussed, as is the alternative of testing for HIV antigens or HIV-specific DNA. From a personal perspective, any test for HIV infection is accompanied by certain benefits and risks. These can be discussed with the patient in the framework of pretest and posttest counseling.

Polymerase chain reaction compared with concurrent viral cultures for rapid identification of human immunodeficiency virus infection among high-risk infants and children

To determine the usefulness of DNA amplification by polymerase chain reaction for the early identification of human immunodeficiency virus type 1 (HIV-1) infection in infants and children, we compared the polymerase chain reaction and concurrent viral cultures of peripheral blood mononuclear cells from 25 high-risk subjects aged 5 weeks to 8 years. In two separate primer pairs, HIV-1 proviral DNA gag sequences were successfully identified in cell lysates from seven patients, including two infants with previously indeterminate HIV-1 status on the basis of serologic and culture results. In the remaining 18 patients the polymerase chain reaction was negative for HIV-1. Simultaneously grown HIV-1 cultures concurred with polymerase chain reaction results for all patients. In an 18-month-old infant who had had a single HIV-1 positive culture at 1 month of age with four subsequent negative cultures, both polymerase chain reaction and HIV-1 culture were negative. Our data demonstrate the clinical applicability of polymerase chain reaction on crude cell lysates for the rapid, early, definitive detection of HIV-1 infection in high-risk infants and children.

Antigen detection for human immunodeficiency virus

The recent development of enzyme immunoassay procedures for the direct determination of human immunodeficiency virus (HIV) antigens has been of significant benefit in both clinical and research applications. The historical development of HIV antigen assays as well as their current and future applications for use in the clinical microbiology laboratory are reviewed. A detailed description of selected commercially available assays is presented, and a comparison is made of various parameters, including sensitivity, specificity, and cost. The use of the HIV antigen assay as an alternative to the reverse transcriptase assay in virus culture applications is also discussed. In addition, the diagnostic and prognostic utility of the HIV antigen assay is considered for various patient groups, including neonatal, high-risk asymptomatic, seronegative, and seropositive patient populations. The use of the HIV antigen assay as an adjunct to anti-HIV antibody testing, as well as its utility in assessing the therapeutic efficacy of antiviral drug therapy, is discussed. The biology of HIV antigen expression and modulation of anti-HIV antibody titers during infection are also discussed in terms of two possible models.

Evaluation of three enzyme immunoassays for HIV-1 antigen detection

Three enzyme immunoassay (EIA) methods for the detection of human immunodeficiency virus (HIV-1) were evaluated. Serum or plasma samples from 22 individuals seropositive for HIV-1 antibodies were tested with the Abbott, Coulter, and DuPont kits for presence of HIV-1 p24 antigen. Another 12 samples were tested with two kits only. Discordant results were obtained with 9 of 34 (26%) HIV-1-antibody-positive patient samples tested. Most of these discrepancies were found in samples containing less than 30 pg/ml of HIV-1 p24 core antigen. A sampling of sera from normal blood donors and patients with infectious or autoimmune diseases revealed a low level of false positive reactions, especially with sera containing antinuclear antibodies or rheumatoid factor. Noteworthy is the frequency of false positive reactions seen with the DuPont EIA for HIV-1 p24 antigen. 18/111 sera (16.2%) containing auto-antibodies tested positively with the DuPont HIV-1 p24 antigen EIA. The nonspecific nature of the test reactivity for 9/10 of these samples was confirmed using an HIV-1 p24 antigen inhibition assay. These findings are discussed in light of the need for HIV-1 antigen detection in the clinical laboratory and of other methods for HIV-1 detection: the polymerase chain reaction and measurements of reverse transcriptase activity.

Human immunodeficiency virus type 1 antigenemia in children

Human immunodeficiency virus type 1 (HIV-1) core antigen was assayed in the plasma of children at risk for infection with HIV to determine its usefulness in the diagnosis of infection and to correlate it with the clinical stage of disease. Antigen was detected in the plasma of all children less than 15 months of age with acquired immunodeficiency syndrome (AIDS). Two thirds of children with AIDS-related illnesses and half of children with asymptomatic infection had antigen. Although 53% of plasma specimens originating from HIV-infected children younger than 6 months of age contained antigen, only 25% of plasma specimens from children younger than 6 months who had no symptoms and none of the 10 specimens from HIV-infected newborn infants contained antigen. Half of the specimens containing core antigen also contained anticore antibody. Quantitative mean antigen levels were more likely to be elevated in children with AIDS (516 pg/ml) than in children with AIDS-related illnesses (295 pg/ml) or in those who had no symptoms (70 pg/ml). Antigen levels tended to increase over time in children with advancing clinical illness, but they tended to decrease over time after a diagnosis of AIDS was made. Antigen was detected in the plasma of 4 of 14 children without symptoms who subsequently reverted to an HIV seronegative state. We conclude that the detection of core antigen occurs with high frequency in children, even young infants, with symptomatic HIV infection. Plasma core antigen was less frequent in children without symptoms and was not detected in 10 infected children when they were tested at birth.

Seronegativity and HIV infection

An African girl born to an HIV seropositive mother was seropositive during the neonatal period, became seronegative, and was again found to be seropositive at 18 and 20 months of age. We suggest that seronegative children born to seropositive mothers should be followed up for months or even years before HIV infection can be ruled out.

Acquired immunodeficiency syndrome: a new population of children at risk

Cases of AIDS in children have been described since 1982. Diagnosis is more complex in children than in adults owing to the more varied clinical presentations and the difficulty in interpretation of laboratory tests. Our current understanding of HIV infection in children is reviewed, as well as the controversies regarding medical, psychosocial, and public health issues.