A commercially available rapid test (HIVCHEK) was compared with an enzyme-linked immunosorbent assay (ELISA) for identifying human immunodeficiency virus type 1 in the serum of newborn infants. Of 1309 cord blood samples tested, the HIVCHEK test detected all the true-positive samples detected by ELISA. Of the 35 samples with positive ELISA results, six had negative results on Western blot; only 1 of the 30 samples with positive HIVCHEK results had negative results on Western blot. Thus the HIVCHEK test can be used to facilitate the rapid identification of HIV-1 in the serum of newborn infants.

ABSTRACT: The increase in the number of human immunodeficiency virus-1 (HIV-1)-infected children is a direct consequence of the heterosexual spread of the disease to women and the growing number of HIV-positive i.v. drug users. It is not known how the majority of infants born to HIV-1-infected women escape HIV-1 infection, and, for those infected, the timing of HIV-1 transmission has yet to be determined. In addition, the role of maternal antibodies in the prevention of HIV-1 transmission to the fetus is unclear. We have previously demonstrated a correlation between vertical transmission and the absence of high-affinity/avidity antibodies to a peptide, KRI-HIGPGRAFYT, which corresponds to a region of the primary neutralizing domain of the gp120 V3 loop of HIVMN (MN-PND). The present study examines the correlation between the presence of these high affinity antibodies in women completing a pregnancy or undergoing an elective abortion and the detection of HIV-1 infection in their aborted fetuses. In several instances, transmission occurred despite high-affinity antibodies to the MN-PND. We have, therefore, evaluated the reactivity of sera to different MN-PND variants. In one infant born to a mother with high-affinity/avidity antibodies to KRIHIGPGRAFYT (classic MN-PND), the infected baby developed antibodies to an MN-PND variant peptide against which his mother did not mount a humoral immune response during pregnancy. This finding indicates that fetal infection with MN-PND escape mutants arising during pregnancy may occur during a period when the mother is serologically negative.

The principal neutralizing domain (PND) for antibody response is located within the V3 variable region of gp120 and can also stimulate T-cell responses. In some adults infected with human immunodeficiency virus (HIV) an HIV-1-specific T-cell response can be detected by demonstrating in vitro proliferation to HIV-1 proteins and peptides. In other HIV-1 infected adults an HIV-1-specific T-cell response can involve interleukin 2 (IL-2) secretion in the absence of T-cell proliferation. To elucidate the T-cell responses to PND in children, we examined the proliferative and the IL-2 secretory responses of peripheral blood lymphocytes from 19 HIV-1-infected children toward a peptide which contained a highly conserved sequence of the principal neutralizing domain of HIVMN (PND-MN). Stimulation with PND-MN induced proliferation of lymphocytes from 2 of the children and IL-2 secretion by lymphocytes from 5 of the children. In a 3-month-old infant, the in vitro cellular response to the PND-MN indicated HIV-1 infection prior to the detection p24 antigen in her serum. Although antibodies directed against PND-MN were detected in all but one of the children examined, the presence of high-affinity/avidity antibodies to the PND-MN correlated with the presence of a cellular response to PND-MN. Thus, in HIV-1-infected children an HIV-1 specific T-cell response in the absence of a proliferative response can be assessed by determination of the IL-2 secretory response and correlates with the generation of high-affinity/avidity antibodies.

The humoral response to HIV-1 infection has been demonstrated by a variety of immunoassays utilizing viral proteins. While several assays detect HIV-1 infection with high sensitivity and great specificity, little progress has been made to develop immunoassays correlative with disease progression and viral transmission. Antibodies toward the V3 domain of HIV-1 envelope can prevent virus infection and block virus-mediated cell fusion in vitro. Such properties may be critical to the course of the disease. Furthermore, understanding the role of neutralizing antibodies against HIV-1 during infection in humans and generating biologically relevant neutralizing antibodies are paramount to developing an efficacious AIDS vaccine. In this study we explored peptide binding and neutralization assays and their relation to predicting disease progression and viral transmission. Biologically relevant polyclonal and monoclonal neutralizing antibodies that were derived from natural HIV-1 infection of humans, experimental infections of chimpanzees, and viral envelope protein peptide immunizations were characterized. Comparison of V3-specific monoclonal antibodies by antigen-limited ELISA and a quantitative HIV-1 neutralization assay demonstrated a less than optimal predictive relationship between binding and neutralization potency. On the other hand, polyclonal sera from goats immunized with V3-specific peptides derived from three different HIV-1 strains, as well as sera from other HIV-1-infected individuals demonstrated correlation between binding affinity and neutralization.

The immunoreactivity of HTLV-III-infected individuals and virus-inoculated chimpanzees with gp120 synthetic peptides of the HTLV-III gp120 envelope principle neutralizing domain (amino acid 301-324 sequences), derived from the HTLV-III isolates 3B, RF, MN, WMJ2, and SC were determined. Sequential bleeds from an infected lab worker and chimpanzees, both infected with the HTLV-IIIB, were immunoreactive only with the 3B peptide. In contrast, 33 HTLV-III-infected individuals were immunoreactive with the HTLV-III(MN) peptide. Of these 33 individuals, 23 were also immunoreactive with the HTLV-III(SC) peptide, and 18 with the HTLV-III(WMJ2) peptide. The data suggest that HTLV-III strains related to MN are most prevalent among HTLV-III-infected individuals. The binding specificities of goat sera generated against either of these synthetic peptides or the C-terminal fragment of gp120 (PB-1, amino acid 287-467, derived from the HTLV-III isolates 3B, RF, MN, WMJ2, and SC) were also determined. Four different ELISA formats (peptide sera/peptide antigens, peptide sera/PB-1 antigens, PB-1 sera/PB-1 antigens, and PB-1 sera/peptide antigens) were utilized to determine the cross-reactivity patterns of goat sera with the antigens. Goat sera generated against MN and SC sequences (PB-1 proteins, as well as synthetic peptides) were highly cross reactive. Thus, patient sera cross reactivity to multiple strains of the principal neutralizing domain may reflect the antigenic relatedness of the virus isolates rather than multiple infection events or strains generated during disease progression.

Many, but not all, infants born to mothers infected with the human immunodeficiency virus (HIV) are infected in utero. We have now shown that mothers who have high-affinity/avidity antibodies directed toward the principal neutralizing domain (PND) of gp120 are less likely to transmit HIV to their children. An ELISA that preferentially measures the level of the biologically functioning, high-affinity/avidity antibodies against PND is described. In a retrospective study of 15 maternal/neonatal serum samples, the assay correctly identified the 4 uninfected and the 11 HIV-infected infants. Other clinical and laboratory parameters such as p24 antigen, phytohemagglutinin mitogenic index, and absolute surface antigen T4+ cell counts did not accurately predict HIV fetal transmission. In addition to introducing a promising diagnostic tool, this study provides the in vivo evidence that protective antibodies may prevent infection by HIV.

Using the western blot technique, we evaluated the reactivity of sera from individuals infected with human retroviruses with the p97 pol precursor. p97 reacted with antibodies in all HIV-1 and HIV-2 positive human sera. The specificity was excellent; no cross-reactivity with wild type baculovirus-infected cell lysates could be demonstrasted

This chapter describes the inhibition of tobacco mosaic virus (TMV) replication in leaf disks, protoplasts, and intact plants by 2, 5-A3 core and selected analogs. Apart from their numerous effects on cellular processes in mammalian systems, the (2'-5')-oligoadenylate cores have been demonstrated to be very potent inhibitors of TMV replication in tobacco leaf disks. The potency of 2,5-A3 core and its analogs as inhibitors of TMV replication in infected protoplasts, TMV-infected leaf disks, and intact plants has been demonstrated. The effectiveness of the 2, 5-A3 core and analogs is markedly decreased when applied to leaves following TMV infection. Although the mechanism by which the mammalian (2'-5')-oligoadenylate cores inhibit TMV replication is not as yet known, the concentrations of 2,5-A3 core and analogs required to inhibit TMV replication in plants are 1/1000th of that required for the inhibition of mammalian viruses or mammalian cell growth.