Kidney transplantation (KT) is the best treatment modality available to date for patients with advanced kidney disease and the success of KT is dependent on maintaining a selective intricate balance between the risk of rejection and infections in KT recipients. BK virus is an important clinical infection affecting the post-transplant outcomes in KT recipients. BK nephropathy can affect 8-15% of patients after KT causing acute kidney injury, increased risk of rejection and fibrosis leading to additional hospital stays, increasing overall health care cost burden, and in some cases graft loss. The exact pathogenesis and treatment options for BK nephropathy are not clearly understood. It is debatable whether BK nephropathy is a full fledge donor-derived infection or reactivation of the recipient's latent infection. Irrespective of etiology, the common consensus is that treatment of BK virus infection depends on the selective restoration of host immune responses and balancing the risk of rejection vs worsening of infection.

As with other viral infections, adaptive immunity plays an essential role in the control of BK virus infection. Previous studies have shown that humoral immunity doesn't prevent viral reactivation and cellular responses including CD4+ and CD8+ T cells play a crucial role in containing viral replication. Researchers have investigated the role of reconstitution of BK-specific T cell immunity KT recipients with overall low immunological risk populations showing that pre and post-transplant BK virus-specific cellular responses can be used as an important tool to identify KT recipients at increased risk of developing BK virus infection in the first year post-transplant. We plan to understand the role of adaptive immunity (cellular and humoral interplay) in a cohort with at least 50% of high immunological KT recipients with predominantly retransplant candidates, highly sensitized recipients with calculated panel reactive antibodies > 40 %, positive crossmatch or history of prior desensitization therapies.

The aim includes the sequential demonstration of immunogenesis processes that are specific to the BK virus in individuals who experience BK viremia and undergo various treatment approaches such as immunosuppression reduction and immune enhancement through intravenous immunoglobulins (IVIG).

Inclusion Criteria:

• Adult (>18 years old) male and female, deceased donor KT recipients
• Will include single organ transplants.
• Each participant must also have recently been diagnosed with BK viremia.
• In addition to the aforementioned inclusion criteria, each participant in the sub-study must also have recently been diagnosed with BK viremia or have difficult-to-treat BKV > 3 logs (BKV log does not decrease by more than 1 log copy/ml drop on second per protocol lab).

Exclusion Criteria:

• Prisoners will not be included in the study
• Multi-organ transplants and pregnant women

The study will include adults 18 and older who have undergone single organ deceased donor Kidney Transplant.