In VivoTropism of Attenuated and Pathogenic Measles Virus Expressing Green Fluorescent Protein in Macaques

Abstract

The global increase in measles vaccination has resulted in a significant reduction of measles mortality. The standard route of administration for the live-attenuated measles virus (MV) vaccine is subcutaneous injection, although alternative needle-free routes, including aerosol delivery, are under investigation. In vitro, attenuated MV has a much wider tropism than clinical isolates, as it can use both CD46 and CD150 as cellular receptors. To compare the in vivo tropism of attenuated and pathogenic MV, we infected cynomolgus macaques with pathogenic or attenuated recombinant MV expressing enhanced green fluorescent protein (GFP) (strains IC323 and Edmonston, respectively) via the intratracheal or aerosol route. Surprisingly, viral loads and cellular tropism in the lungs were similar for the two viruses regardless of the route of administration, and CD11c-positive cells were identified as the major target population. However, only the pathogenic MV caused significant viremia, which resulted in massive virus replication in B and T lymphocytes in lymphoid tissues and viral dissemination to the skin and the submucosa of respiratory epithelia. Attenuated MV was rarely detected in lymphoid tissues, and when it was, only in isolated infected cells. Following aerosol inhalation, attenuated MV was detected at early time points in the upper respiratory tract, suggesting local virus replication. This contrasts with pathogenic MV, which invaded the upper respiratory tract only after the onset of viremia. This study shows that despite in vitro differences, attenuated and pathogenic MV show highly similar in vivo tropism in the lungs. However, systemic spread of attenuated MV is restricted.Measles virus (MV) is one of the most contagious human viruses and is transmitted via aerosols or by direct contact with contaminated respiratory secretions. Clinical symptoms appear approximately 2 weeks after infection and include fever, rash, cough, coryza, and conjunctivitis (20). Measles is associated with immunosuppression, resulting in increased susceptibility to opportunistic infections. While significant progress has been made in global control programs, 164,000 deaths were attributed to measles in 2008 (46).MV was first isolated in cell culture in 1954 (16). This Edmonston wild-type MV strain was passaged multiple times in primary human kidney and amnion cells and adapted to eggs and chicken embryo fibroblasts to produce the live-attenuated Edmonston-B vaccine virus (15), which was later replaced by the more attenuated MV strains (Edmonston-Zagreb, Moraten, and Schwarz) (34). These vaccines have been shown to be safe and effective, and high coverage in two-dose regimens has successfully interrupted endemic MV transmission in large geographic areas (6).For many years, laboratory-adapted MV-Edmonston strains were used as the prototype virus and were shown to display a wide cellular tropism in vitro. The virus efficiently infected epithelial cells, which were considered the target cells for primary MV infection in vivo (22). In 1993,...

Wild-Type Measles Virus with the Hemagglutinin Protein of the Edmonston Vaccine Strain Retains Wild-Type Tropism in Macaques

“…This result is not surprising because it was reported that only the lymph nodes and spleen of monkeys were infected with MV vaccine strains (39). Furthermore, it was recently reported that CD11c-positive myeloid cells, such as alveolar macrophages and dendritic cells in lungs of monkeys, were infected with an EGFP-expressing recombinant Edmonston strain of MV via an aerosol route (5). This result is consistent with our findings in that the CD46-using Edmonston vaccine strain does not cause widespread infection in the lungs of monkeys, although there is a possibility that the infection by the Edmonston strain in lungs may be restricted due to mutations in the N and P/C/V genes, which are most important in combating the innate immune system.…”

Successful respiratory immunization with dry powder live-attenuated measles virus vaccine in rhesus macaques

“…Replication of vaccine strains of MeV in the upper and lower respiratory tract and in lung CD11c + immune cells has been observed after respiratory delivery to macaques (29). Furthermore, protective levels of antibody can be induced with nebulized intratracheal LAMV, which suggests that viral replication in the lower respiratory tract is sufficient to induce protective immunity (30).…”

Human Langerhans cells capture measles virus through Langerin and present viral antigens to CD4+ T cells but are incapable of cross‐presentation

“…The wild-type MV strain WTF [51], the laboratory-adapted MV strain Edmonston B, the recombinant pathogenic MV strain IC323-eGFP [52] and the recombinant attenuated strain Edmonston-eGFP [53] were propagated on Vero-CD150 cells and purified by discontinuous sucrose gradient ultracentrifugation. Purified MV strains were UV-inactivated (30 min, 15 W, 312 nm, 1.5 J/cm 2 ).…”