A multivalent polyomavirus vaccine elicits durable neutralizing antibody responses in macaques

Abstract

In 2019, there were about 100,000 kidney transplants globally, with more than a quarter of them performed in the United States. Unfortunately, some engrafted organs are lost to polyomavirus-associated nephropathy (PyVAN) caused by BK and JC viruses (BKPyV and JCPyV). Both viruses cause brain disease and possibly bladder cancer in immunosuppressed individuals. Transplant patients are routinely monitored for BKPyV viremia, which is an accepted hallmark of nascent nephropathy. If viremia is detected, a reduction in immunosuppressive therapy is standard care, but the intervention comes with increased risk of immune rejection of the engrafted organ. Recent reports have suggested that transplant recipients with high levels of polyomavirus-neutralizing antibodies are protected against PyVAN. Virus-like particle (VLP) vaccines, similar to approved human papillomavirus vaccines, have an excellent safety record and are known to induce high levels of neutralizing antibodies and long-lasting protection from infection. In this study, we demonstrate that VLPs representing BKPyV genotypes I, II, and IV, as well as JCPyV genotype 2 produced in insect cells elicit robust antibody titers. In rhesus macaques, all monkeys developed neutralizing antibody titers above a previously proposed protective threshold of 10,000. A second inoculation, administered 19 weeks after priming, boosted titers to a plateau of ≥ 25,000 that was maintained for almost two years. No vaccine-related adverse events were observed in any macaques. A multivalent BK/JC VLP immunogen did not show inferiority compared to the single-genotype VLP immunogens. Considering these encouraging results, we believe a clinical trial administering the multivalent VLP vaccine in patients waiting to receive a kidney transplant is warranted to evaluate its ability to reduce or eliminate PyVAN.

Keywords: BKV; HPyV1; HPyV2; JCV; PyVAN; Transplant.

Figure 1.. Production and purification of polyomavirus VLPs:

A) Coomassie-stained SDS-PAGE analysis of VLPs used to immunize mice and monkeys. Lanes 1–4 correspond to culture supernatant-derived VLPs (s) and lanes 5–8 correspond to cellular pellet-derived VLPs (p). Lanes 1,5 BKPyV-I (I), lanes 2,6 BKPyV-II (II), lanes 3,7 BKPyV-IV (IV), and lanes 4,8 JCPyV (JC). B-E) Electron micrographs of purified indicated VLPs. A bar corresponding to 50nm in length was added for size comparisons.

Figure 2.. Serological response of mice immunized with polyomavirus VLPs:

Pseudovirus neutralization serology was performed on pooled sera from groups of five BALB/c mice after the first (prime) and second (boost) doses of VLPs administered intramuscularly with alum adjuvant. EC₅₀ titers of 6 and above are highlighted in purple, 5 to 5.9 in red, 4 to 4.9 in orange, 3 to 3.9 in yellow, 2 to 2.9 in green, and negative (undetectable to 1.9) in blue.

Figure 3.. Serological response of rhesus macaques immunized with polyomavirus VLPs:

16- to 20-year-old macaques were immunized with 10 μg of VLPs and 100 μg of alum were used as an adjuvant. Serum samples were obtained prior to immunization and weekly for the first 6 weeks after administration of the initial dose of VLPs. A second dose of VLPs was given at week 19 post prime. Additional serum was obtained at weeks 25, 43 and 92. The neutralizing titer of the sera was evaluated over time and the EC₅₀ is depicted in the graphs. Macaques immunized with BKPyV-I are depicted by the blue circles, those immunized with BKPyV-IV are shown with red squares, and macaques receiving a quadrivalent vaccine (BKPyV-I, II, IV and JCPyV) are shown with green triangles.