A novel factor produced by placental cells with activity against HIV-1.

The factors controlling the dynamics of HIV-1 transmission from mother to infant are not clearly known. Previous studies have suggested the existence of maternal and placental protective mechanisms that inhibit viral replication in utero. Preliminary studies from our laboratory revealed that supernatant from placental stromal cells protected HIV-1-infected PBMC from virus-induced apoptosis and suppressed virus production. We have attempted to characterize the antiviral activity of this placental factor (PF) and delineate the stages of HIV-1 replication affected. This activity was not due to the presence of any known cytokine reported to have anti-HIV effect. Direct exposure to PF had no suppressive effect on the infectivity of cell-free HIV-1, and envelope-mediated membrane fusion appeared to be unaffected. Western blot analysis of HIV-1 from infected PBMC treated with PF revealed that expression of all viral proteins was reduced proportionately, both intracellularly and in released virions. However, exposure of HIV-1-infected cells to PF resulted in production of virions with 10-100-fold-reduced infectivity. PF-treated virions contained two- to threefold reduced ratios of cyclophilin A:Gag protein as compared with untreated virus. Reduced cyclophilin A content resulting in decreased binding of cyclophilin A to Gag could account, in part, for the observed reduction in infectivity. Our results suggest that placental cells produce an antiviral factor that protects the fetus during gestation and may have therapeutic potential.

Extensive evaluation of a seronegative participant in an HIV-1 vaccine trial as a result of false-positive PCR.

BACKGROUND: In the USA, more than 2000 volunteers have received one or more experimental HIV-1 vaccines in phase I and II clinical trials, and there have been breakthrough HIV-1 infections among participants receiving vaccine and placebo. Serological diagnosis of new HIV-1 infections in vaccine-trial participants will become increasingly complicated as more viral components are used in vaccines. Recognition of this problem has led to a reliance on viral-genome measurement to distinguish vaccine-induced immunity from HIV-1 infection. Currently, quantitative RNA measurement is expensive, prone to contamination, and reliable only in laboratories certified by manufacturers or that have quality-control programmes. METHODS: A high-risk vaccinee presented after an acute febrile episode and was tested for HIV-1 infection by reverse transcriptase (RT) PCR of viral RNA. Further extensive tests were required to clarify the HIV-1 infection and immune status of the vaccinee, including repeat RT-PCR, nested DNA PCR, western blot, lymphoproliferation assay, cytotoxic T-cell lysis, CD8-depleted co-culture, and HIV-1 challenge culture. FINDINGS: Initial testing of plasma by RNA RT-PCR was reported as positive. This result was not confirmed by viral cultures, nested DNA PCR, western blot, or EIA. Additional RNA RT-PCR assays gave positive results from earlier occasions in the vaccine trial. Eventually, testing of all previously reactive samples by RNA RT-PCR was repeated in a quality-controlled laboratory, and confirmed the negative HIV-1 status of the individual. INTERPRETATION: This case report exemplifies the difficulties with use of viral-genome measurement as a screening test to diagnose HIV-1 infection, particularly in individuals who have ever participated in HIV-1 vaccine trials. Monitoring of large numbers of phase III vaccinees by RNA RT-PCR will not be feasible. The design of efficacy trials for new vaccines should be in parallel with development of antibody-based diagnostic tests that are capable of differentiating between immunisation and true HIV-1 infection.