Anneka Ehrnst

Mother to child transmission of HIV infection in the era of highly active antiretroviral therapy

BACKGROUND Very low rates of mother-to-child transmission (MTCT) of human immunodeficiency virus (HIV) are achievable with use of highly active antiretroviral therapy (HAART). We examine risk factors for MTCT in the HAART era and describe infants who were vertically infected, despite exposure to prophylactic MTCT interventions. METHODS Of the 4525 mother-child pairs in this prospective cohort study, 1983 were enrolled during the period of January 1997 through May 2004. Factors examined included use of antiretroviral therapy during pregnancy, maternal CD4 cell count and HIV RNA level, mode of delivery, and gestational age in logistic regression analysis. RESULTS Receipt of antenatal antiretroviral therapy increased from 5% at the start of the HAART era to 92% in 2001-2003. The overall MTCT rate in this period was 2.87% (95% confidence interval [CI], 2.11%-3.81%), but it was 0.99% (95% CI, 0.32%-2.30%) during 2001-2003. In logistic regression analysis that included 885 mother-child pairs, MTCT risk was associated with high maternal viral load (adjusted odds ratio [AOR], 12.1; P=.003) and elective Caesarean section (AOR, 0.33; P=.04). Detection of maternal HIV RNA was significantly associated with antenatal use of antiretroviral therapy, CD4 cell count, and mode of delivery. Among 560 women with undetectable HIV RNA levels, elective Caesarean section was associated with a 90% reduction in MTCT risk (odds ratio, 0.10; 95% CI, 0.03-0.33), compared with vaginal delivery or emergency Caesarean section. CONCLUSIONS Our results suggest that offering an elective Caesarean section delivery to all HIV-infected women, even in areas where HAART is available, is appropriate clinical management, especially for persons with detectable viral loads. Our results also suggest that previously identified risk factors remain important.

Maternal viral load and vertical transmission of HIV-1: an important factor but not the only one

OBJECTIVES To investigate the association between maternal RNA load, risk of vertical transmission of HIV-1, and other variables. METHODS Plasma or serum samples from mothers of 373 children, enrolled in the prospective European Collaborative Study, were collected around time of delivery, and HIV-RNA quantified using two types of commercial assay. Women and children were followed according to a standard protocol. Adjusted odds ratios (AOR) were calculated to estimate the effect of RNA load and other maternal factors on vertical transmission. RESULTS Maternal RNA levels, mode of delivery and gestational age were independently associated with transmission. Vertical transmission increased with increasing RNA levels, but there was no threshold below which transmission did not occur. The risk was more than double for women with RNA above the sample specific median [AOR 2.36 (1.23-4.52)]. Elective caesarean section was associated with a substantial and significant decrease in transmission [AOR 0.19 (0.06-0.55)], and delivery before 37 weeks gestation with an increased risk [AOR 2.67 (1.33-5.38)]. Elective caesarean section was effective in both subgroups defined by median RNA level [AORs 0.37 (0.08-1.71) and 0.15 (0.03-0.64) below and above median respectively]. The predicted rate of transmission in a woman with a low RNA load delivering by elective caesarean section or vaginally after 37 weeks is around 2%, and 11%, respectively. INTERPRETATION Mother-to-child transmission of HIV-1 is multi-factorial; high RNA load is an important determinant but clearly not the only one. Interventions that target risk factors other than maternal RNA load remain important.

Coreceptor change appears after immune deficiency is established in children infected with different HIV-1 subtypes

Change of HIV-1 coreceptor use has been connected to progression of disease in children infected with HIV-1, presumably subtype B. It has not been possible to discern whether the appearance of new viral phenotypes precedes disease development or comes as a consequence of it. We studied the evolution of coreceptor use in HIV-1 isolates from 24 vertically infected children. Their clinical, virological, and immunological status was recorded and the env V3 subtype was determined by DNA sequencing. Coreceptor use was tested on human cell lines, expressing CD4 together with CCR5, CXCR4, and other chemokine receptors. The children carried five different env subtypes (nine A, five B, four C, three D, and one G) and one circulating recombinant form, CRF01_AE (n = 2). Of the 143 isolates, 86 originated from peripheral blood mononuclear cells (PBMCs) and 57 originated from plasma, received at 90 time points. In 52 of 54 paired plasma and PBMC isolates the coreceptor use was concordant. All 74 isolates obtained at 41 time points during the first year of life used CCR5. A change from use of CCR5 to use of CXCR4 occurred in four children infected with subtype A, D, or CRF01_AE after they had reached 1.5 to 5.8 years of age. There was a significant association with decreased CD4+ cell levels and severity of disease but, interestingly, the coreceptor change appeared months or even years after the beginning of the immunological deterioration. Thus CXCR4-using virus may emerge as a possible consequence of immune deficiency. The results provide new insights into AIDS development in children.

Echovirus Type 23 Observed as a Nosocomial Infection in Infants

Echovirus type 23 was isolated from 5 children, aged 1-13 months, during a 7-month period, covering a study period of several decades. The children were hospitalized for long periods because of chronic conditions. In 4 cases the virus was isolated from faecal samples, collected because of diarrhoea and/or vomiting. In one case echovirus type 23 was collected from nasopharyngeal secretions from a child with respiratory symptoms. The features of echovirus type 23 infection were similar to those of echovirus type 22, but it is striking that infections with echovirus type 23 were less common during the same decades covered by the study.

Peptide Microarray-Based Identification of Mycobacterium tuberculosis Epitope Binding to HLA-DRB1*0101, DRB1*1501, and DRB1*0401

ABSTRACT A more effective vaccine against Mycobacterium tuberculosis is needed, and a number of M. tuberculosis vaccine candidates are currently in preclinical or clinical phase I and II studies. One of the strategies to select M. tuberculosis (protein) targets to elicit a CD8+ or CD4+ T-cell response is to gauge the binding of candidate peptides to major histocompatibility complex (MHC) class I or class II molecules, a prerequisite for successful peptide presentation and to expand antigen-specific T cells. We scanned 61 proteins from the M. tuberculosis proteome for potential MHC class II-presented epitopes that could serve as targets for CD4+ T-cell responses. We constructed a peptide microarray consisting of 7,466 unique peptides derived from 61 M. tuberculosis proteins. The peptides were 15-mers overlapping by 12 amino acids. Soluble recombinant DRB1*0101 (DR1), DRB1*1501 (DR2), and DRB1*0401 (DR4) monomers were used to gauge binding to individual peptide species. Out of 7,466 peptides, 1,282, 674, and 1,854 peptides formed stable complexes with HLA-DR1, -DR2, and -DR4, respectively. Five hundred forty-four peptides bound to all three MHC class II molecules, 609 bound to only two, and 756 bound to only a single MHC class II molecule. This allowed us to rank M. tuberculosis proteins by epitope density. M. tuberculosis proteins contained “hot spots,” i.e., regions with enriched MHC class II binding epitopes. Two hundred twenty-two peptides that formed MHC class II-peptide complexes had previously been described as exclusively recognized by IgG in sera from patients with active pulmonary tuberculosis, but not in sera from healthy individuals, suggesting that these peptides serve as B-cell and CD4+ T-cell epitopes. This work helps to identify not only M. tuberculosis peptides with immunogenic potential, but also the most immunogenic proteins. This information is useful for vaccine design and the development of future tools to explore immune responses to M. tuberculosis.

Polar appearance and nonligand induced spreading of measles virus hemagglutinin at the surface of chronically infected cells

Fixation with glutaraldehyde (GA) and paraformaldehyde (PFA) preserved measles virus hemagglutinin at the surface of chronically infected cells. Cells fixed with PFA but not with GA exhibited hemadsorption with green monkey cells. PFA fixation, in contrast to GA fixation, also preserved the immunogenicity of measles virus hemolysin. These fixatives and the removal of the measles virus hemagglutinin from the cell surface by trypsin enabled studies of the appearance of the hemagglutinin at the surface membrane. Results obtained by immunofluorescence technique and by hemadsorption indicated that measles virus hemagglutinin appeared polarly at the cell membrane and then spread around the surface. This was substantiated by measurements of the immunofluorescence intensity at the single cell level per membrane unit and per cell, and by measuring the binding of iodinated immunoglobulins per 10(6) cells. The appearance was inhibited by sodium azide and cytochalasin B. The spreading was not inhibited by sodium azide, but was influenced by cytochalasin B. The spreading did not proceed at 4 degrees C. On the basis of these findings, a hypothetical model for appearance and spreading of measles virus hemagglutinin was proposed.

No Findings of Enteroviruses in Swedish Patients with Chronic Fatigue Syndrome

Enteroviruses have been proposed to cause an immune complex disease in the chronic fatigue syndrome. Altogether 34 patients with the chronic fatigue syndrome, according to criteria of the Centers for Disease Control, USA, were studied evenly over the seasons for the possible presence of a chronic enterovirus infection. In 11 patients, 1-5 faecal samples were collected at about 6 month intervals for virus isolation before and after acid treatment, followed by ultracetrifugation at pH 3 to dissolve possible enterovirus-antibody complexes. Another 14 fecal samples were subjected to routine virus isolation alone. Seven pairs of serum-cerebrospinal fluid samples were analysed for cross-reactive IgG antibody activity to enteroviruses. In 29 patients a muscle biopsy was collected for enterovirus polymerase chain reaction (PCR). We were unable to identify enteroviruses in any of these samples by any of these techniques. Our study does not confirm evidence for persistent enterovirus infection in the chronic fatigue syndrome.

Characterization of blood mononuclear cells reacting with K 562 cells after yellow fever vaccination

Abstract At various times after yellow fever (17 D) vaccination mononuclear blood cells were tested for cytotoxic potential in conjugate with K 562. They were characterized with monoclonal reagents Leu2a, Leu4, and OKM1, using indirect immunofluorescent technique. The cytotoxicity against K 562 increased after vaccination with a peak on Days 8–12 when the [ 3 H]thymidine uptake was also maximal. The majority of cells in conjugates with K 562 were then T cells. Later the conjugates contained more OKM1-positive cells. OKM1 reagent was found to react with K 562 and thereby cause a coagglutination between this target cell and the OKM1-positive monocytic cells. The surface moiety reacting with OKM1 reagent might be of lipid nature.

Pattern of HIV Viraemia and CD4 Levels in Relation to Pregnancy in HIV-1 Infected Women

The objective was to study HIV-1 viraemia and CD4 levels during and 6 months after pregnancy. HIV cultures on peripheral blood mononuclear cells (PBMC) and plasma from 225 samples were performed in 90 HIV-1 infected women with 59 continued and 35 terminated pregnancies. P-24 antigen and HIV-DNA were also studied. 34 women originated from European, 44 from African and 10 from other countries while 2 were of unknown origin. HIV was detected in 30% of the plasma cultures from the first trimester and in approximately 50% thereafter. Repeated plasma isolations did not give an indication of HIV activation, nor did the cross-sectional time-to-culture positivity in plasma and in PBMC, PBMC isolation frequencies, HIV-DNA and CD4 levels. The plasma viraemia frequencies were generally higher and the CD4 levels lower in the African women than in the European ones. Six months after delivery there was a significant decrease in the CD4 cell counts compared to delivery, but not when compared to the values during the first or second trimesters. The results showed that HIV activity during pregnancy was relatively stable, followed by indications of resumed activity during the first 6 months after delivery.

Charged amino acid patterns of coreceptor use in the major subtypes of human immunodeficiency virus type 1

Human immunodeficiency virus type 1 has several genetic subtypes and two coreceptor use phenotypes: R5 that uses CCR5, while X4 uses CXCR4. A high amino acid charge of the envelope glycoprotein 120 V3 region, common at positions 11 and 25, is important for CXCR4 use. We characterized charged V3 amino acids, retrieving all biologically phenotyped sequences from the HIV Sequence Database. Selecting individually unique ones randomly yielded 48 subtype A, 231 B, 180 C, 37 D and 32 CRF01_AE sequences; 482 were R5 and 46 were X4. Charged amino acids were conserved in both R5 and X4 with general and subtype-specific patterns. X4 viruses gained a higher charge from positive amino acids at positions other than in R5, and through the loss of negative amino acids. Other positions than 11/25 had a greater impact on charge (P<0.001). This describes how R5 evolves into X4 in a subtype-specific context, useful for computer-based predictions and vaccine design.