HIV infections continue to be a global health threat, and there is still no vaccine or cure available. Dr. Ruprecht’s research is focused on lentiviruses such as HIV, where she develops strategies for treatment and prevention. Her special interest is to develop vaccines against HIV/AIDS, particularly against the world’s most prevalent subtype of HIV (HIV-C) in Sub-Saharan Africa and India. Her research strategy is to:
- Develop vaccines to block HIV at portals of entry: mucosal sites
- Construct multi-component vaccines that enlist as many host defense mechanisms as possible
Dr. Ruprecht was the first to demonstrate the in vivo safety and efficacy of AZT drug treatment in animal models, including prevention of maternal virus transmission. AZT later became the first FDA-approved AIDS drug and the first drug to prevent HIV transmission from an infected woman to her newborn. Dr. Ruprecht has been collaborating with scientists in the US, Europe, Asia and Africa, and is now Director of Texas Biomed’s AIDS research program. She has been studying lentiviruses since the discovery of HIV and has worked with non- human primate (NHP) models for more than 25 years.
In The Lab
Understanding mucosal virus transmission and vaccine development. One current research focus is on understanding mucosal virus transmission and its prevention, since 90 percent of all new HIV infections occur through mucosal exposure. To study anti-HIV-C envelope responses in NHP models, we have generated a panel of chimeric simian-human immunodeficiency virus (SHIV) strains that encode envelopes of recently transmitted HIV-Cs. The resulting SHIV-Cs are pathogenic, and one such infectious molecular clone was used to measure how easily different mucosal barriers can be penetrated in rhesus macaques. The relative mucosal permeability in the primate model paralleled the relative risks of HIV acquisitions in humans exposed to virus by different routes, thus confirming the SHIV-C model as a biologically relevant tool.
A protective anti-HIV vaccine needs to be not only bimodal — able to induce both cellular and humoral immunity — but also protect the mucosal barrier. We are actively pursuing such a “defense-in-depth” strategy. Using recombinant viral proteins as immunogens, we induced high levels of specific T cells and cross-neutralizing antibodies (Abs) in some vaccinated rhesus macaques. When challenged mucosally with SHIV-C carrying a heterologous env gene, some rhesus macaques were completely protected. Neutralizing Ab titers and cellular immune responses were significant correlates of protection.
To protect the mucosal barrier, we focused on IgA Abs in mucosal fluids, where these molecules exist in dimeric form. We provided the first direct proof that dimeric IgAs targeting the HIV envelope and delivered mucosally can protect rhesus macaques against mucosal virus challenge. A vaccine that could stimulate strong mucosal IgA responses against HIV would have a significant impact on transmission rates.
We have also developed a novel strategy to identify the protein regions in a vaccine that are exclusively recognized by Abs from rhesus macaques protected by vaccination — but not by Abs from rhesus macaques where the vaccine had failed. Using our new tool (termed differential biopanning), we have identified an Ab target outside the virus envelope that was significantly linked to vaccine protection. This new approach is attractive to refine vaccine design, even beyond HIV/AIDS vaccine development or infectious disease.
Our lab also developed the technology to isolate epitope/mimotope-specific monoclonal Ab (mAbs) from single rhesus monkey memory B cells collected by flow cytometry. This new approach utilizes fusion proteins linked to green fluorescent protein. These new technologies could lead to the isolation of novel recombinant mAbs for clinical use.
Mother-to-child transmission (MTCT). Primate models have played an essential role in our work; this includes studying the interaction of lentiviruses with the developing immune system in the fetus and newborn. Our long-term goal is to prevent HIV MTCT by effective antiviral drugs as well as by enlisting immune defenses, and we utilized infant rhesus monkey models with SIV or SHIV in our studies. We provided proof-of-principle for the:
- Pathogenicity of live attenuated, nef–deleted SIV when used as a vaccine in neonatal RMs; this finding was confirmed later also in adult RMs
- Protection of neonatal RMs against oral SHIV transmission with a combination of neutralizing human monoclonal Abs — even when given as post-exposure prophylaxis (PEP)
- Time dependence of successful PEP
Our current goal is to determine whether candidate AIDS vaccines, partnered with antiviral drugs, will not only completely suppress HIV replication in babies infected with HIV at birth, but will also induce such strong antiviral cellular immune defenses that the virus will not reemerge after all treatment is stopped. We will test our concepts in infant and neonatal rhesus macaques. These primate models will allow us to assess whether the virus can be cleared from tissue reservoirs and whether long-lasting protective immunity has been generated by the combined treatment.
Main Technologies And Methods Used
- Cloning, production and purification of monoclonal Abs
- Sequencing to study viral evolution
- Passive and active immunization in primate models
- Flow cytometry
- Virus transcytosis
- Assays for cell-mediated and humoral immune responses