Accurate detection of Zika virus IgG using a novel immune complex binding ELISA.

OBJECTIVES: Accurate serological assays are urgently needed to support public health responses to Zika virus (ZIKV) infection with its potential to cause foetal damage during pregnancy. Current flavivirus serology for ZIKV infections lacks specificity due to cross-reacting antibodies from closely related other flaviviruses. In this study, we evaluated novel serological tests for accurate ZIKV IgG detection. METHODS: Our ELISAs are based on immune complex binding. The high specificity is achieved by the simultaneous incubation of labelled ZIKV antigen and unlabelled flavivirus homolog protein competitors. Two assays were validated with a panel of 406 human samples from PCR-confirmed ZIKV patients collected in Brazil (n = 154), healthy blood donors and other infections from Brazil, Europe, Canada and Colombia (n = 252). RESULTS: The highest specificity (100% [252/252, 95% confidence interval (CI) 98.5-100.0]) was shown by the ZIKV ED3 ICB ELISA using the ED3 antigen of the ZIKV envelope. A similar test using the NS1 antigen (ZIKV NS1 ICB ELISA) was slightly less specific (92.1% [232/252, 95% CI 88.0-95.1]). The commercial Euroimmun ZIKV ELISA had a specificity of only 82.1% (207/252, 95% CI 76.8-86.7). Sensitivity was high (93-100%) from day 12 after onset of symptoms in all three tests. Seroprevalence of ZIKV IgG was analysed in 87 samples from Laos (Asia) confirming that the ED3 ELISA showed specific reactions in other populations. CONCLUSIONS: The novel ED3 ICB ELISA will be useful for ZIKV-specific IgG detection for seroepidemiological studies and serological diagnosis for case management in travellers and in countries where other flavivirus infections are co-circulating.

Factors associated with viral load suppression in HIV-infected pregnant women in Rio de Janeiro, Brazil.

Viral load (VL) near delivery is a determinant of mother-to-child transmission (MTCT) of HIV. To evaluate factors associated with an undetectable VL near delivery in HIV-infected pregnant women receiving highly active antiretroviral therapy (HAART) and non-HAART regimens, HIV-infected pregnant women with a detectable VL at entry and having used antiretrovirals for ≥4 weeks before delivery were selected. Multivariate analysis was employed using binary logistic unconditional models; the dependent variable was having a VL <400 copies/mL near delivery. VL suppression was achieved in 403/707 women (57%): 65.4% in the HAART group, but only 26% in the non-HAART group P = 0.001. Duration of HAART was correlated with VL suppression, with maximum benefit seen after ≥12 weeks of therapy (odds ratio [OR]: 2.51; 95% confidence interval [CI]: 1.72-3.65). CD4+ cell count near delivery (OR: 1.53; 95% CI: 1.06-2.20) and baseline VL (OR: 0.74; 95% CI: 0.58-0.94) were also independently associated with VL suppression. Overall MTCT rate was 1.6%. HAART for ≥12 weeks, baseline VL and CD4 cell count near delivery were independently associated with viral suppression near delivery.

Neutralization titres and vertical HIV-1 transmission.

Replication of the human immunodeficiency virus type 1 (HIV-1) isolate MN in CEM cells was less neutralized by the plasma from the mothers of infected children (MIC) in comparison with the plasma from the mothers of uninfected children (MUC). Significantly higher neutralization titres were observed for the sera from MUCs compared with MICs, and only the sera from MUC showed 100% neutralization of the HIV-1 MN strain. We suggest that a simple neutralization assay as described here could be useful in prognostic analyses.

Vertical HIV-1 transmission: importance of neutralizing antibody titer and specificity.

Neutralization analyses were carried out with plasma from 132 volunteer human immunodeficiency virus (HIV)-1 infected women (76% pregnant, 24% with infants suspected for HIV-1 infection) collected between 1994 and 1998, against autologous and heterologous primary- and the reference HIV-1 MN isolates. A significantly lower percentage of HIV-1 transmissions was observed after 1996, parallel to a more intense antiretroviral treatment of infected pregnant women. HIV-1 isolation was significantly more frequent from peripheral blood mononuclear cells of mothers of infected children than mothers of uninfected children (P = 0.0065). Neutralization of autologous HIV-1 isolates was comparable for HIV-1 transmitters and nontransmitters' plasma, whereas neutralization of the reference isolate HIV-1 MN was more frequent at high titers for pregnant women who did not transmit HIV to their offspring compared to pregnant women who did. Although neutralization of heterologous primary HIV-1 isolates from HIV transmitters and non transmitters by transmitter plasma occurred with similar frequency, neutralization of isolates from transmitters was much more frequent when heterologous plasma from nontransmitters were used. Macrophage-tropic heterologous HIV-1 isolates were neutralized more frequently at higher titers by plasma from nontransmitters than from transmitters. The results obtained indicate that antiretroviral treatment, lack of success of HIV-1 isolation and high titers of antibodies able to neutralize macrophage-tropic viruses appear to be of importance for protection against HIV-1 vertical transmission for the group of patients studied.

Accumulation of 3H-phosphoinositides mediated by muscarinic receptors in the developing chick retina: inhibition of carbachol-induced response by glutamate receptors.

In the present work we show the development of carbachol-induced accumulation of 3H-inositol phosphates (3H-InsPs) in the chick embryonic retina and its regulation by glutamate receptors. Although basal levels of 3H-InsPs increased during development, the retinal response to carbachol was high in the early developing stages and decreased after synaptogenesis in the retina. Eserine also stimulated the turnover of phosphoinositides in the embryonic but not in the mature retina. The effect of eserine could be blocked by atropine, suggesting that acetylcholine could be released from developing retina cells and further stimulate the turnover of InsPs in the embryonic tissue. Our data also show that muscarinic stimulation of turnover of 3H-InsPs could be blocked by stimulation of glutamatergic ionotropic receptors. Moreover, the effect of glutamate agonists did not seem to be mediated by the release of other neurotransmitters such as GABA, glycine, adenosine, or dopamine from the tissue because these neurotransmitters did not interfere with the retinal response to carbachol. These results suggest that muscarinic activation of phosphoinositide turnover occurs mainly in the embryonic retina and that activation of glutamate receptors can inhibit directly the muscarinic stimulation of hydrolysis of 3H-InsPs in this tissue.

Transient cyclic AMP accumulation mediated by dopamine D1 receptors in the chick embryo optic lobe.

[3H]SCH 23390 bound with high affinity (Kd = 0.6 nM) and in a saturable manner (Bmax = 130 fmol/mg protein) to membrane preparations of the chick optic lobe. Pharmacological experiments, using several dopaminergic ligands, revealed that [3H]SCH 23390 bound stereospecifically to dopaminergic receptors of the D1 type in this tissue. Other experiments revealed that dopamine was able to induce cyclic AMP accumulation in the optic lobe (ED50 = 3 microM), an effect that was blocked by fluphenazine, a potent D1 antagonist (IC50 = 1.8 microM). The developmental profile of tissue dopamine-dependent cyclic AMP accumulation, however, was quite different from the differentiation pattern of [3H]SCH 23390 specific binding sites. While [3H]SCH 23390 binding sites increased 4-fold after the 12th embryonic day (E12), dopamine-dependent cyclic AMP accumulation was maximal in earlier stages, decreasing progressively after E10. In tissues from embryos at E16 or older, no difference was observed between basal and dopamine-stimulated levels of cyclic AMP. These data suggest that D1 receptors are coupled to adenylate cyclase in a limited period of the development of the optic lobe and that D1 receptors not coupled to the enzyme can be a common feature in the CNS.