If you want to know what is in the Johnson & Johnson, it is the adenovirus Type 26. The following website details Type 26 and I've copied and pasted it.

[link to www.sciencedirect.com (secure)]

2. Background

The adenovirus type 26 (Ad26) wild type virus was first isolated in 1956 from an anal specimen of a 9-month-old male child [2]. As described in that study, 4 different isolates were obtained from anal and throat swabs from different children, some of whom experienced mild self-limiting enteric infections. Although, none of the illnesses could etiologically be associated with the isolated adenoviruses, it suggests that wild type Ad26 can, presumably, cause asymptomatic or minor illness [2]. Human Ad26 has been considered to be a low-prevalent adenovirus due to the low frequency of Ad26 neutralizing antibodies in various populations compared with human adenovirus type 5.

And this....

2.2. Manufacturing, formulation and stability
Ad26 vector-based vaccines are manufactured using the E1-complementing PER.C6® cell line, a continuous, human cell line capable of supporting the manufacturing of replication incompetent adenoviral vectors [22]. One of the key strengths of this cell platform is that the cells can grow in suspension in serum-free media to very high cell densities. Cell counts of 100 million cells/mL, with a high percentage of viable cells, can be reached within 10 days of cell culture. Janssen has taken advantage of the ability to grow the PER.C6® cell line at high cell densities in a so called “intensified process”. Cell-specific yields are in the same range as is generally achieved with other Adenoviral vectors and E1-complementing cell lines, therefore, due to the higher cell densities yields per volume unit are higher. The complete manufacturing process has now been scaled up to 1,000 L allowing manufacturing at a commercial scale.

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Where does the PER.C6 cell line come from?

[link to www.gmp-creativebiolabs.com (secure)]

The PER.C6 cell line is derived from human embryonic retinal cells, originally from the retinal tissue of an 18 week old fetus aborted in 1985 and further developed and prepared as cell line by transfection with defined E1 region of the adenovirus type 5 followed by selection for transfectants with an immortal phenotype. At the beginning, this cell line was mainly applied for the production of human adenovirus vectors for use in vaccine development and gene therapy, and further optimization makes PER.C6 become a superexcellent host cell line for large-scale industrial production of therapeutic proteins, especially the human IgG.

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From a gov't website:

[link to faqs.in.gov (secure)]