Preclinical Assessment of Antibody Responses to Adeno-Associated Virus (AAV) Vector-Based Capsids of AAV2, AAV5, AAV8, or AAV9 in Laboratory Cynomolgus Macaques ( <i>Macaca fascicularis</i> ) of Asian or Mauritian Origin

Adeno-associated virus (AAV)-based vectors are the most commonly used vectors for gene therapy. Wild-type AAV infections occur widely in humans and nonhuman primates (NHPs), and an accurate assessment of preexisting AAV antibodies is crucial for the efficient use of AAV-based gene therapies in preclinical and clinical studies. Cynomolgus macaques (<i>Macaca fascicularis</i>) are well-established preclinical large animal models for evaluating the efficacy and safety of AAV-mediated gene therapies intended for human use. We provide a retrospective evaluation comparing preexisting AAV-neutralizing or total antibody titers against serotypes AAV2, AAV5, AAV8, or AAV9 in cynomolgus macaque cohorts of Asian or Mauritian origin. We used an <i>in vitro</i> neutralizing antibody (NAB) assay to detect NAB titers or an <i>in vitro</i> Meso Scale Discovery-based assay for the quantification of total binding antibodies (TABs) in blood samples. Results were obtained to measure the serostatus of animals. In our analysis, the <i>in vitro</i> NAB assay revealed the lowest seroprevalence for AAV5 (13 ± 15% to 21 ± 6%) independent of origin. In the same assay, Asian animals were highly seropositive against AAV8, followed by AAV2 and AAV9 serotypes (88 ± 13%, 71 ± 10%, 69 ± 9%, respectively). Whereby, the prevalence of seropositivity was lower in animals of Mauritian origin with the highest seroprevalence for AAV9 (58 ± 7%), followed by AAV8 (53 ± 17%) and AAV2 (51 ± 20%) assessed by <i>in vitro</i> TAB assay. Notably, co-prevalences of antibody responses against AAV2, AAV8, and AAV9 serotypes resulted in 39.8% seropositivity (<i>in vitro</i> NAB assay) in NHPs of Asian and in about 32.6% (<i>in vitro</i> TAB assay) of Mauritian origin.