Construction of pIHBoV1 mutants. pIHBoV1NS1(2) and pIHBoV1NP1 (2) were constructed by mutating HBoV1 nt 542 from T to A, and nt 2588 from G to A, resulting in stop codons that lead to early termination of the NS1 and NP1 ORFs, respectively. Similarly, pIHBoV1VP1(2) and pIHBoV1VP2 (2) were generated by mutating HBoV1 nt 3205 from T to A, and nt 3540 from T to G, disrupting VP1 and VP2 ORFs, respectively.