Caracterização da replicação de dois isolados brasileiros do vírus Mayaro em modelos in vitro e in vivo e análise genotípica da linhagem D

Abstract

Mayaro virus (MAYV) is an emerging arbovirus from the Togaviridae family, Alphavirus genus, associated with a disease that presents debilitating musculoskeletal manifestations such as myalgia and chronic arthralgia. Although it is primarily transmitted by sylvatic mosquitoes in forested areas of the Americas, recent outbreaks in Brazilian cities suggest possible urban circulation, raising concerns in densely populated areas. MAYV comprises three genotypes with distinct geographic distribution. Genotype D is the most widely distributed and has been associated with the majority of outbreaks, while genotype L shows more restricted circulation in Brazil. Genotype N has been identified exclusively in Peru. Genotypic differences in MAYV may influence viral replication, tissue tropism, host immune response, and disease severity, but these aspects remain underexplored in comparative pathogenesis studies. In the present study, we compared three MAYV strains from two genotypes: the prototype ATCC strain (genotype D, isolated in 1954), the ACRE strain (genotype D, isolated in 2004 in Acre, Brazil), and the SINOP strain (genotype L, isolated in 2011 in Mato Grosso, Brazil). We conducted analyses using both cellular (in vitro) and animal (in vivo) models to assess differences in viral replication, immune response induction, and pathogenicity triggered by strains from different genotypes, aiming to describe the disease they cause. In the in vitro assays, all strains replicated efficiently in Aedes albopictus (C636) mosquito cells, with ATCC and SINOP showing the highest replication up to 72 hours post-infection (hpi). In Aedes aegypti (Aag2) cells, however, replication was inefficient for all recently isolated strains. In mammalian cells, the ACRE strain showed lower replication and absence of cytopathic effect, while ATCC and SINOP induced greater cell destruction in murine muscle cells. Moreover, infection with the ACRE strain led to higher expression of interferon-stimulated genes, reflecting stronger activation of the antiviral response, which may contribute to better infection control in this cell model. In mouse infection models, the SINOP strain resulted in the highest viral loads in all analyzed tissues, particularly muscles and joints, culminating in greater lethality and inflammation in muscle and joint tissues, indicating higher virulence. Conversely, the disease induced by the ACRE strain initially showed signs of infection control but rapidly progressed to a severe condition, quickly leading to animal death. Genomic analyses revealed that, although ACRE and ATCC strains belong to the same genotype (D), they exhibit distinct mutations in key proteins involved in viral entry and virulence (such as E1, E2, and nsP3), indicating spatiotemporal genomic evolution within the same genotype. These findings underscore the importance of considering MAYV genotypic diversity in pathogenesis and surveillance studies, since different genotypes may differ in transmission dynamics, vector adaptation, and clinical severity. Additionally, they highlight the limitations of using the prototype ATCC strain as a universal model for MAYV infection, emphasizing the need for studies with recent isolates representative of current circulation in Brazil.