Yichen Lu

Human neutralizing monoclonal antibodies of the IgG1 subtype protect against mucosal simian-human immunodeficiency virus infection.

Although maternal human immunodeficiency virus type 1 (HIV-1) transmission occurs during gestation, intrapartum and postpartum (by breast-feeding), 50–70% of all infected children seem to acquire HIV-1 shortly before or during delivery. Epidemiological evidence indicates that mucosal exposure is an important aspect of intrapartum HIV transmission. A simian immunodeficiency virus (SIV) macaque model has been developed that mimics the mucosal exposure that can occur during intrapartum HIV-1 transmission. To develop immunoprophylaxis against intrapartum HIV-1 transmission, we used SHIV–vpu+ (refs. 5,6), a chimeric simian–human virus that encodes the env gene of HIV-IIIB. Several combinations of human monoclonal antibodies against HIV-1 have been identified that neutralize SHIV–vpu+ completely in vitro through synergistic interaction. Here, we treated four pregnant macaques with a triple combination of the human IgG1 monoclonal antibodies F105, 2G12 and 2F5. All four macaques were protected against intravenous SHIV–vpu+ challenge after delivery. The infants received monoclonal antibodies after birth and were challenged orally with SHIV–vpu+ shortly thereafter. We found no evidence of infection in any infant during 6 months of follow-up. This demonstrates that IgG1 monoclonal antibodies protect against mucosal lentivirus challenge in neonates. We conclude that epitopes recognized by the three monoclonal antibodies are important determinants for achieving substantial protection, thus providing a rational basis for AIDS vaccine development.

rhesus Macaques That Become Systemically Infected With Pathogenic Shiv 89.6-pd After Intravenous, Rectal, or Vaginal Inoculation and Fail to Make an Antiviral Antibody Response Rapidly Develop Aids

A new simian-human immunodeficiency virus (SHIV) stock (SHIV 89.6-PD), derived from plasma of a rhesus macaque used for in vivo serial passage of virulence-attenuated SHIV 89.6, produces systemic infection after intravenous, intravaginal, or intrarectal inoculation of rhesus macaques. Infection with this virus results in high levels of viral antigen in plasma, a precipitous decline in CD4+ T-cell counts, and a disease syndrome that is characteristic of AIDS. Rapid progression to disease was associated with failure to seroconvert to viral antigens, whereas longer survival was associated with production of antiviral antibodies. In intravenously inoculated animals, peak antigenemia occurred at 7 days postinjection (PI) and severe CD4+ depletion occurred at 14 days PI. In mucosally infected animals, peak antigenemia occurred at 14 days PI and severe CD4+ depletion was not evident until 21 days PI. The 1-week delay in both viral antigenemia and CD4+ T-cell decline in mucosally infected animals is consistent with the hypothesis that, following vaginal inoculation, virus dissemination proceeds in a stepwise manner from the mucosal surface to the draining lymph nodes and subsequently to the bloodstream. This animal model can be used to test the ability of HIV-1 envelope-based vaccines to prevent infection or disease after challenge by the three major routes of HIV transmission.

The common mucosal immune system for the reproductive tract: basic principles applied toward an AIDS vaccine

Abstract The concept of the Collaborative Mucosal Immunization Research Group for AIDS (CMIG) was originally conceived by the AIDS Vaccine Branch, National Institute of Allergy and Infectious Diseases (NIAID) in order to provide support for a cooperative research environment for the development of mucosal immunity to AIDS. We have purposely organized five groups of investigators at five different locations to determine how effective mucosal immunity to AIDS can be optimally approached. CMIG recognizes that both rectal (homosexual) as well as vaginal (heterosexual) infections with HIV are two of the major ways that AIDS currently disseminates through the human population. Thus, we have chosen the SIV model of infection of rhesus macaques, but more importantly the CMIG have joined two of our five components in order to use the significant expertise developed for mucosal transmission of SIV and immunity. Thus, we have brought the extensive expertise with vaginal and rectal immunization and immunity to spread [Drs. Chris Miller and Marta Marthas, California Regional Primate Research Center (CRPRC), Davis and Drs. Thomas Lehner and Martin Cranage, United Medical and Dental School Guys Hospital, London and the Centre for Applied Microbiology and Research (Guys/CAMR)]. Two additional components were added in order to perform mucosal immune response studies required to develop and to optimize a mucosal vaccine. First, extensive CD4+ T helper (Th) cell (e.g., Th1 and Th2) and CD8+ T cell subset studies are a major effort of the coordinating group at the University of Alabama at Birmingham (Drs. Hiroshi Kiyono and Jerry R. McGhee). This component is closely interacting with both the CRPRC and Guys/CAMR components in terms of SIV-specific CD4+ and CD8+ T cell subset responses. For example, SIV-specific CTL responses are jointly examined using different techniques by CRPRC, Guys/CAMR and UAB investigators. Further, it is also important to examine a balance between SIV-specific and Th1 and Th2 cell responses following mucosal immunization since the Th cell-derived cytokines are essential for the induction of appropriate antigen-specific mucosal immune responses. This issue is currently being extensively examined by the CMIG effort and a summary of our findings is discussed in this review. A major question in mucosal immunity involves the functions of secretory IgA (S-IgA) antibodies and this area is of particular importance in rectal and reproductive tract immunity. A novel and exciting in vitro epithelial cell assay system is used to study how effectively S-IgA neutralizes SIV infection (Drs. John Huang, John Nedrud and Michael Lamm, Case Western Reserve, Cleveland). A clear advantage of this CMIG effort is the unique expertise in design of mucosal delivery systems for an AIDS vaccine. We are using state-of-the-art recombinant bacteria, i.e.. rSalmonella and rVibrios for mucosal immunization [Drs. Yichen Lu and Bryan Roberts, Virus Research Institute (VRI), Boston]. In addition, we are also testing other mucosal delivery systems including DNA vaccine, microspheres, cholera toxin (CT) and CT-B, recombinant poliovirus, and immune complexes. These studies represent the first efforts to induce not only Th cell mediated S-IgA responses, but also CTL responses to SIV in primates immunized with different mucosal vector delivery systems. In order to focus our effort for the induction of SIV-specific immune responses following mucosal immunization, investigators from the CMIG are attempting to understand the induction and regulation of antigen-specific immune responses in rhesus macaques mucosally immunized with different preparations of SIV vaccines.