Perinatal transmission of HIV type 1: associations with maternal anti-HIV serological reactivity. Mothers and Infants Cohort Study and the HIV-1 Perinatal Serology Working Group

Maternal humoral factors associated with perinatal human immunodeficiency virus type-1 transmission in a cohort from Kigali, Rwanda, 1988-1994

OBJECTIVES

to study different parameters of humoral immunity responses in the serum of 39 human immunodeficiency virus type-1 infected pregnant women from Kigali, (Rwanda) in correlation with perinatal transmission.

METHODS

this study was done between 1988 and 1994. Thirty nine HIV-1 infected women, 18 transmitting (T) and 21 non-transmitting (NT) mothers, have been chosen based on the quantity of sera available for analysis. Maternal data were collected at the time of delivery or during the preceding month. Quantification of viral load was performed by the signal amplification bDNA assay. Specific reactivity of antibody was tested against recombinant p24 protein and five different synthetic peptides from gp120 and gp41 based on HIV LAI-strain sequences. Neutralization assays were performed against laboratory (RII strain of the HIV-1 C subtype) and primary strains (two NSI and one SI of the HIV-1 A subtype). Antibody Dependent Cellular Cytotoxicity assay was performed with CEM.NK(R) cells against a laboratory HIV-1 strain.

RESULTS

absence of correlation regarding maternal viral load, or viral subtype and vertical transmission was observed. By contrast, the CD4/CD8 ratio was significantly higher in non-transmitting mothers compared to transmitting mothers. Moreover, high anti-p24 antibody avidity was correlated with a lower risk of perinatal transmission. Furthermore, transmission risk appeared significantly higher with reactivity of serum samples to linear epitopes of gp41 (amino acids 566-582, 578-594), whereas risk appeared lower with reactivity to the immunodominant domain of gp41 (amino acids 597-609). No significant difference was observed in titres of antibody neutralizing primary isolates (two NSI (non syncitium inducer) and one SI (syncitium inducer) of the HIV-1 A subtype) and laboratory strain (RII strain, of the HIV-1 C subtype) between transmitting and non-transmitting mother's sera. In addition, titres of Antibody Dependent Cellular Cytotoxicity were similar in transmitting versus non-transmitting mothers. However, high Antibody Dependent Cellular Cytotoxicity titres were correlated with a good clinical status of children.

CONCLUSIONS

three parameters such as high CD4/CD8 ratio, high anti-p24 antibody avidity and high reactivity against the immunodominant epitope of gp41 have been shown to be correlated with no perinatal transmission. High Antibody Dependent Cellular Cytotoxicity titres appeared to be linked to a good clinical status of children after birth. One parameter, reactivity against two linear epitopes of gp41, appeared to be correlated with vertical transmission.

Neutralizing antibodies and complement-mediated, antibody-dependent enhancement (C'-ADE) of human immunodeficiency virus infection in its vertical transmission

PROBLEM

Mother-to-child transmission is a major route for the spread of human immunodeficiency virus (HIV) worldwide. Our understanding of its mechanisms and parameters is still limited. Among the factors possibly involved in virus passage determination are the level and quality of antiviral humoral response.

METHOD OF STUDY

Anti-HIV-1/Lai neutralizing activity in sera from 35 mother-infant pairs (in which 13 transmission cases occurred) was investigated, as was the complement-mediated antibody-dependent enhancement capacity of the same sera.

RESULTS

Neutralization titers of 640 or more were found only in four mothers of uninfected children, but this result was not significant. No significant link was obtained with the occurrence of complement-mediated, antibody-dependent enhancement.

CONCLUSIONS

As suggested by a synthesis of the literature, vertical transmission of HIV is probably the result of multiple active and/or stochastic parameters in the mother, the fetal structures, and the viral population. The precise definition of cellular mechanisms involved in in utero infection would help to better define which immune activity in the mother should be more carefully considered.

Neutralizing antibody and perinatal transmission of human immunodeficiency virus type 1. New York City Perinatal HIV Transmission Collaborative Study Group

The major immunologic determinants for perinatal transmission of human immunodeficiency virus type 1 (HIV-1) remain largely unknown. The presence of maternal neutralizing antibodies has been proposed as an explanation for why the majority of infants born to untreated HIV-1-infected women do not become infected. Using maternal and infant specimens collected as part of a longitudinal cohort study of perinatal transmission in New York City between 1991 and 1995, we successfully obtained primary viral isolates from 10 of 20 perinatally nontransmitting (NTR) women, 14 of 20 perinatally transmitting (TR) women, and 13 of 13 of their HIV-1-infected infants. Neutralizing antibody titers were then determined using a titer reduction assay. TR and NTR women did not differ in their ability to neutralize autologous virus or laboratory strains LAI and MN. Infant viruses were not less sensitive to neutralization by maternal sera than autologous viruses. Similarly, TR and NTR isolates were neutralized equally well using a reference serum with broad neutralizing ability. Finally, a heteroduplex tracking assay (HTA) was used to analyze the degree of viral homology within 13 TR maternal-infant pairs. In eight pairs, maternal and infant isolates were highly homologous. In five pairs, lesser degrees of homology were observed, consistent with perinatal transmission of a minor species. However, these isolates were no more or less resistant to maternal sera than were homologous isolates. Thus we found no association between the presence of neutralizing antibody in maternal sera as measured by a titer reduction neutralization (inactivation) assay and perinatal transmission of HIV-1.

Interaction between timing of perinatal human immunodeficiency virus infection and the design of preventive and therapeutic interventions

In 1994, the hypothesis that transmission of human immunodeficiency virus (HIV) from mother to child could be interrupted became a reality when it was shown that a regimen of zidovudine given to HIV-infected pregnant women and their newborn infants could reduce the risk of perinatal transmission by two-thirds. An understanding of the pathogenesis of transmission is crucial for interpreting these results, for design of future interventions and for understanding the natural history of perinatal HIV infection. This paper will review current information regarding the timing of and risk factors for perinatal HIV transmission, and the relationship between the timing of transmission and design of efforts to interrupt transmission and to slow disease progression in infected infants.

Characterization of human immunodeficiency virus type 1 p17 matrix protein motifs associated with mother-to-child transmission

In order to determine if viral selection occurs during mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1), we used a direct solid-phase sequencing method to sequence the p17 matrix protein-encoding regions of viral isolates from 12 HIV-1-infected mother-and-child pairs, 4 infected infants, 4 transmitting mothers, and 22 nontransmitting mothers and compared the sequences. The blood samples were collected during the delivery period for the mothers and during the first month of life for most of the children. The p17 nucleic sequences were distributed among several clades corresponding to the HIV-1 A, B, and G subtypes. At the amino acid level, no significant differences within the known p17 functional regions were observed among the subtypes. Statistical analyses could be performed with the B subtype. Within the major p17 antibody binding site, a constant KIEEEQN motif (amino acids 103 to 109) was found in all mother-and-child isolates from the B subtype. On the other hand, 9 of 17 nontransmitting mother isolates were variable in this 103 to 109 region. Thus, this motif was significantly associated with the transmitting status (chi square, P = 0.0034). A valine residue at position 104 was significantly associated with the nontransmitting phenotype (chi square, P = 0.014), suggesting that it has a protective role during vertical transmission. The C-terminal end of p17 was globally conserved among nontransmitting mother isolates (chi square, P = 0.0037). These results might improve the understanding of the pathogenesis of HIV-1 vertical transmission and might allow the screening of seropositive mothers by a rapid molecular or peptide test.