The advent of robust im/m agents as part of induction/maintenance therapy for KTx has greatly limited the incidence of Ac rejection.
CMR/TCMR
Abbreviations (read twice
please, put also UR comments):
o
AB: antibodies
o
ABMR/AMR: antibody-mediated
(humoral) rejection
o
Ac Rj: acute
rejection
o
Ag: antigen
o
ALm: Alemtuzumab
o
Am: antimicrobial
o
AMR: antibody-mediated
(previously humoral) rejection
o
AMR: antibody-mediated
rejection
o
ATG: Antithymocyte
globulin
o
Aza: Azathioprine
o
BMD: bone mineral
density
o
C: complement
o
CLL: chronic
lymphocytic leukemia
o
CMV: cytomegalovirus
o
CyA: Cyclosporine
o
Dgx: diagnosis
o
Gctcds: glucocorticoids
o
IF/TA: interstitial
fibrosis/tubular atrophy
o
Ig: Immunoglobulin
o
IgG: immunoglobulin
G
o
im/m: immunosuppression/immunosuppressive
o
KTR: kidney
transplant recipients
o
KTx: kidney
transplantation
o
MMF: Mycophenolate
mofetil
o
MR: Mortality
rate
o
Mthyprd: methylprednisolone
o
NK: natural
killer cells
o
PCP: Pneumocystis pneumonia
o
Pph: plasmapheresis
o
PPI: proton
pump inhibitors
o
Pred: Prednisone
o
Prox: prophylactic
o
Prox: prophylaxis
o
PTLD: posttransplant
lymphoproliferative disorder.
o
rATG-T: rabbit antithymocyte globulin (Thymoglobulin)
o
RCT: randomized
controlled trial
o
Rj Dgx: rejection
diagnosis
o
Rj: rejection
o
SCr: serum
creatinine concentration
o
SE: side
effects
o
Sms: symptoms
o
Sns: signs
o
SRL: Sirolimus
o
Tac: tacrolimus
o
TCMR/CMR: T cell-mediated (cellular)
rejection
o
ttt: treatment
o
ttt: treatment
o
Tx: transplant/transplantation
o
UO: urine
output
The
advent of robust im/m agents as part
of induction/maintenance therapy for KTx
has greatly limited the incidence of Ac Rj
that could be defined as an acute decline in allograft function combined with certain
pathologic alterations in graft tissues. Utilizing the current im/m regimens, Ac
Rj rates have dropped to 8 % at many Tx
centers. Ac Rj can be generally
classified into CMR & AMR. Kidney
allograft biopsy is mandated to settle the Dgx and recognize the intensity of Rj to identify the most appropriate inlet to management.
CMR & AMR
may be coexisting simultaneously in the kidney allograft (i.e., mixed Ac Rj). The finding of tissue evidence of Ac Rj on biopsy with no associated rise in SCr is called subclinical Rj.
OUTCOMES/PROGNOSIS
Acute CMR is seen
most commonly within the 1st y after Tx and rarely
reported after 5 y post-Tx.
Generally, repeated attacks of Ac Rj would be complicated by decline in allograft longevity, despite
not all Rj episodes
have similar impact on allograft function. The effect of successful control of
acute CMR on graft
outcome has not been well assessed. Higher histological intensity of acute CMR (i.e., Banff grade > IA) has been
complicated with lowered response to ttt. Greater histological scores (e.g.,
i:
interstitial inflammation, t: tubulitis, v: intimal
arteritis) with delayed onset of Rj (>3 mo post-Tx)
have been complicated with worsened allograft outcome. Genetic studies
have shown that several molecular bases driving acute CMR are also underlying the evolution of chronic
histologic lesions of IF/TA that has
been accompanied by graft failure. Dedicated algorithm has been designed
(see alg.) & validated to anticipate the long-term risk of graft
failure in KTR. It’s
incorporating the functional, histological, and immunologic profile to identify
a prognostic
score (the iBox) for TR that can
be applied at any time after Tx, even at the timing of Rj Dgx. Further
studies are needed to recognize iBox utility regarding the clinical impact and
management.
TREATMENT: ttt approach in TR
with histological evidence of acute CMR
is primarily guided by the histopathological intensity of Rj:
1)
TR with
borderline CMR, there’s
no consensus regarding optimal management. Some Tx centers do
not provide specific ttt for Rj but only augment
the maintenance im/m by
targeting greater Tac levels (i.e.,
5-7 ng/mL) in ptns with
Tac trough values
are in its lower levels (i.e., 3-5 ng/mL) and/or by optimizing MMF doses.
Other Tx
centers prefer
to ttt borderline Rj like
acute CMR.
Subclinical Rj is usually
identified on surveillance/protocol biopsy with lack of clinical Sms/Sns.
2)
TR with Banff grade I Rj are
mostly provided with pulse high-dose IV steroids, followed by tapered oral Gctcds. Moreover,
maintenance im/m
would be augmented. TR with Banff IB Rj with few/no
chronic histological changes presenting < one y post-Tx, we give rATG-T added to the
pulse steroids.
3)
TR with Banff II/III Rj, we provide
pulse high-dose IV steroids, followed
by an oral tapered steroid. Moreover, we provide rATG-T +
augmented maintenance im/m. If rATG-T not
tolerated, we give ALm.
4)
TR with
evidence of combined acute CMR & AMR; i.e., mixed Ac Rj, on allograft biopsy should be ttt for both CMR & AMR.
Banff I Rj: Suggested
approach for ptns with Banff I Rj:
a)
Biopsy-proven Banff IA/IB CMR
(no evidence of AMR), ptns admission
is typically advocated. We give pulse IV Mthyprd at 3-5 mg/kg/d for 3-5 doses, maximum 500 mg/d. After pulse steroids, oral steroids are tapered rapidly to the maintenance oral
Pred kept before to the attack. If there’re
no concern about non-adherence, we provide augmented maintenance Pred dose, e.g., if the Rj seen
while TR was on 5
mg/d, we may raise Pred to 10 mg/d. Moreover, other members of maintenance im/m adjusted as required. Some Tx centers prefer to ttt Banff
IA CMR with an
equivalent dose of high-dose oral steroids
as an OPD, provided that ptns
can return for frequent lab monitoring.
b)
In Banff IB
CMR +
few/no chronic histological lesions presenting < one y post-Tx, we provide rATG-T with pulse steroids at 1.5-3 mg/kg/dose/ 1-3 ds for total dosing of 3-6 mg/kg in the 1st y. In these ptns, Mthyprd is provided as 3-5 mg/kg
(maximum 500 mg) before each dose of rATG-T. Shorter/higher-dosing
of ttt (i.e., single dose of rATG-T 3 mg/kg) is preferred
to limit cost & length of hospitalization. The rationale for rATG-T addition
is based on evidence that severe (t3) tubulitis that distinguishing Banff
IB from IA CMR, is complicated by worse allograft
outcome as compared to milder (t1 or t2) tubulitis and warranting more robust ttt.
Pulse
Mthyprd is the 1st-line
therapy for acute CMR in most Tx centers. Added to the intensified maintenance im/m, such pulse steroids
are commonly the only added ttt if Rj is Banff IA
or IB. The percentage reversing rate
for the 1st episode of acute CMR
is 60-70 % with
this protocol. Successful response: UO increased & SCr starts
declining within 5
days after the start of therapy.
TR are mostly responding to steroids;
few high-quality reports comparing the efficacy of various steroid regimens for ttt
of CMR. One trial: 95 episodes of kidney allograft Rj seen in 45 KTR, ttt
with IV pulse
Mthyprd (1 g boluses) or high-dose oral Pred induced
the same rate of reversal of Rj (about 60 %). Fluid
retention was commonly seen among ptns ttt
with high-dose oral Pred. This study
was proceeded before CMR & AMR dealt as separate entities.
Banff G
II/III Rj, suggested
approach for Banff II/III Rj:
●TR with biopsy-proven Banff
IIA, IIB,
or III CMR, in-ptns admission is preferred. We can provide pulse IV Mthyprd 3-5 mg/kg/d./ 3-5 doses (maximum 500 mg/d.),
followed by rapidly-tapered oral Pred dosing.
Typical steroid taper would be starting with
Pred 40 mg/d and to decrease the daily dosing by 10 mg every 5 ds
until 10 mg d., after which the daily dosing
is decreased to 5 mg daily after another 5 ds. Moreover, we give daily rATG-T at 1.5-3 mg/kg/dose
for total dosing of 5-10
mg/kg. Total No. of doses is limited by Banff severity,
e.g., with Banff IIA CMR, we may give rATG-T 2.5 mg/kg/d./2 d, and in Banff III, we give 2
mg/kg/d/4-5 ds according to the response in SCr levels. Other members of maintenance im/m adjusted as required. Ptns not tolerating rATG-T, we give ALm:
30 mg single IV dose. Such ptns may include TR with
allergic history to rATG-T (e.g., with induction or during previous ttt of Rj)
or ptns with WBCs < 2000/microL or platelet count < 75,000/microL. We may also give ALm, rather than rATG-T, to ptns having
previous history of severe rabbit exposure (i.e., having raised or ingested rabbits) and, so,
may be at risk of serum sickness
after rATG-T.
●ALL
ptns ttt with rATG-T (or ALm)
& high-dose steroids, we resume Am &
antiviral Prox/3 mo with a regimen similar to that provided in immediate
post-Tx timing including Prox against
PCP, CMV
infection/disease, & herpes simplex infection (in ptns at low-CMV
risk). Moreover, we also provide antifungal Prox.
ATG:
a polyclonal Ig that’s prepared via injecting human thymocytes into rabbits (rATG-T) or horses (Atgam).
ATG can
induce T lymphocyte depletion in the
peripheral blood mainly via C-dependent
cell lysis; it also shows some B
cell-AB, inhibiting B cell proliferation leading to B cell apoptosis. ATG
has been used both for Prox against
and for initial ttt of Ac Rj. Reversal rate for Ac Rj is between 75 &
100 % in several series, with SCr reversal
to baseline several days-week.
Comparing rATG-T to Atgam was conducted
in a multicenter, double-blind, RCT of 163 KTR with Ac Rj. Compared with Atgam, rATG-T induced higher rate of Rj reversal (88 vs 76 %) with
lowered rate of recurrent Rj within 90 d. after AB therapy
(17 vs 36 %). Ptns & graft
survival and the rates of SE and infectious episodes were similar.
Given the greater efficacy of rATG-T in ttt of Ac Rj, Atgam is no longer provided routinely in most Tx centers,
although it’s sometimes used in ptns having known allergy to rabbits or rATG-T if ALm is not
available.
Optimal
dose & duration of rATG-T for ttt
of Ac Rj is not certain. Pivotal
trial: that approved rATG-T as ttt
for Rj (US),
the medium total dose was 10 mg/kg given along
6 doses. It’s now established
that more intense & durable lymphocytic depletion that’s believed to be one
of the major mechanisms of rATG-T action can be achieved via larger but fewer
doses along short time. ALm is a
humanized anti-CD52 monoclonal AB that’s
approved for CLL. CD52 Ag is present on T
& B lymphocytes, NK cells,
and, to a less extent, on monocytes & macrophages. ALm can lyse lymphocytes via C activation & AB-dependent
cytotoxicity. A few reported studies, ALm
has been conducted for the ttt of Ac Rj.
ALm advantages: may include
peripheral, rather
than central, venous route with short ttt course. Large study: ALm reversed Ac Rj in 63 % of KTR on Tac monotherapy
with either steroid-resistant
Rj or at
least Banff
IB Rj. Other measures included reversing Tac weaning, steroids, and/or adding
SRL.
Infectious episodes were observed in 35 % of ptns, 2 ptns died, one due to infection and the other developed PTLD. ALm has been also
efficacious for CMR in pediatrics.
Borderline/subclinical
Rj: There’s no available consensus in ttt
borderline Rj
and, specifically, whether anti-Rj
ttt should be provided. Some Tx centers do not provide specific ttt for Rj
but rather augment maintenance im/m via
targeting greater Tac levels (i.e., 5-7 ng/mL) in TR with Tac trough
levels with lowered range (i.e., 3-5 ng/mL) and/or via optimizing MMF
doses. Other Tx centers prefer to ttt
borderline Rj as acute CMR, considering observational data showing
pathologic Dgx of borderline Rj is complicated by adverse clinical &
histological outcomes, e.g., progressive
fibrosis & greater risk of
subsequent Rj, graft failure,
and ptn MR. However, other reports
question the benefit of Rj ttt in this
type of Rj.
Subclinical
Rj can be defined as: = [the finding of histological
evidence of Ac Rj on
biopsy without rise in SCr]. It can be found
on a surveillance/protocol biopsy with no associated clinical Sms/Sns. Application
of protocol biopsy is generally confined to ptns conducted
in experimental im/m regimens considering
the lowered incidence of subclinical Rj
in ptns on Tac,
MMF, & steroids. It’s not clear if the advent of therapy with subclinical
Rj may improve clinical outcome. A
few reports have managed this question:
1)
Report: 72 ptns ttt with CyA, Aza, & steroids were assigned
to biopsy at 1, 2, 3, 6, & 12 mo post-Tx (biopsy g.) or to biopsy at 6 & 12 mo (control g.).
Subclinical Rj found at
mo: 1, 2, & 3 in biopsy g. was ttt with high-dose steroids. Compared
with no ttt, steroids therapy
was associated with less attacks of Ac Rj & lowered SCr at 2 ys (1.5 vs 2 mg/dL, 133
vs 183
micromol/L).
2)
Multicenter
report: 240 KTR ttt with Tac, MMF, & steroids assigned to protocol biopsies or control arm, with
subclinical Rj ttt with steroids. At 6 mo,
there was no difference in allograft function between g.s. Authors reported
that protocol
biopsy was NOT
beneficial with robust im/m (i.e., Tac/MMF/ steroids).
Further workup
with prolonged follow-up is needed to conclude whether protocol biopsy,
combined with robust im/m given for ttt of subclinical Rj,
improving long-term outcomes.
Monitoring ttt response: All
ptns being ttt
for acute CMR, it’s
preferable to advocate in-ptns admission during management. SCr monitoring
on daily
basis while the ptn is hospitalized to evaluate response to ttt. After discharge,
SCr can be
monitored on a weekly
basis until corrected
to the baseline (before Rj) or a plateau on new baseline has been established.
Assessment
of peripheral
blood donor-derived cell-free DNA (dd-cfDNA) can
be applied to support Ac Rj Dgx to monitor ttt response. Ptns with raised plasma dd-cfDNA (i.e., >1 %) at the timing of Dgx, we may repeat dd-cfDNA at 1-2 mo after start of ttt.
Ptns responding to ttt, dd-cfDNA fraction should decline back to normal (<1 %) within 2 mo. The current dd-cf DNA tests
in clinical practice have not been validated to define low-grade (Banff
1A or less) or borderline Rj, nor have they been accepted to assess the
response of low-grade CMR to ttt.
As
mentioned before, some Tx centers ttt ptns with less severe Ac Rj (i.e., Banff IA) with higher-dose oral steroids on an out-ptns
basis. In such ptns, SCr should be assessed
EOD, if possible, until returned to its
baseline or became plateaus at a new baseline,
then routine follow up can be resumed. TR with
CMR ttt with steroids
& rATG-T and not having intense chronic histological changes (e.g., IF/TA, vascular
intimal sclerosis, arteriolar hyaline
thickening) or frank necrosis, a favorable result to ttt is anticipated, typically within 3-5 d. of ttt start. Decline in SCr
to within 10 %
of baseline is considered to be a successful reversal of Rj. Ptns with
evidence of chronic injury & fibrosis are less likely to have reversal of allograft
dysfunction.
Next
steps to ttt according to the response to
initial therapy:
o
SCr decline:
keep augmented im/m + low-dose oral Pred indefinitely.
o
No decline in SCr
after 5 d of
Rj ttt
are considered initial ttt failure.
So, ongoing Rj and/or alternate Dgx of allograft dysfunction should be suspected. Next
steps depend on the initial ttt for Rj:
o
Ptns ttt with steroids only, we can
provide rATG-T. Ptns cannot tolerate
rATG-T, we can
provide a single dose of ALm.
o
Ptns ttt with rATG-T (or ALm if ptn not
tolerating rATG-T), we may repeat
a graft biopsy to exclude an alternate Dgx or a more intense histological lesion (e.g., higher Banff or AMR). If higher Banff is identified,
we ttt with appropriate therapy for the higher Banff, as above. If biopsy shows evidence of AMR, we start
ttt for AMR. If biopsy
shows absence of reversible changes or extensive fibrosis (= dead
renal tissue), hold ttt of Ac Rj.
When to hold therapy: It is difficult decision but crucial &
determined by overall clinical situation of the TR.
Therapy withdrawal is recommended
with:
1)
Current infectious episodes with
undue risks with further im/m augmentation.
2)
Lack of
response after intense course of pulse steroids and/or rATG-T, and absent
evidence of AMR on repeat
biopsy (dictating alternate ttt plan) or any other alternative etiology for persistent graft dysfunction.
3)
Dead renal
tissue on biopsy. It’s beneficial to get trichrome stain to assess fibrotic
status. The magnitude of chronic alterations on initial biopsy can help guiding
the power/duration of im/m. With low
evidence for reversible
changes, risk of infection/malignancy due to high-dose im/m may
outweigh any benefit.
Current toxicities: The major sequalae of pulse steroids is the higher susceptibility to infection, particularly oral candidiasis. Other sequalae may include hyperglycemia, HT, peptic ulceration, and psychiatric upsets e.g., euphoria & depression. Prox histamine-2 (H2) blockers or PPI & antifungals are usually advised. Bone disease is commonly seen in KTR, with the most crucial risk factor being the loss of BMD due to the cumulative effect of steroids. The highest steroids-induced bone loss is in the 1st 3-12 mo after Tx. As most CMR observed within the 1st y. post-Tx, further steroids may intensify its cumulative dose.
Fever & chills may be developed
during initial rATG-T administration.
Anaphylactoid
reactions, e.g., respiratory
distress & hypotension, are currently
rare. Concurrently given pulse steroids before rATG-T may prevent or significantly limit infusion-induced
reactions. Considering the risk of phlebitis, rATG-T should be provided via central venous route; however,
rATG-T can be given
via peripheral line if mixed with heparin and antihistaminic premedication.
Pruritic
skin rash can be seen in
20 % of rATG-T-ttt ptns.
Contaminated rATG-T with platelets & RBCs
can induce AB production & SE of thrombocytopenia. Thymoglobulin
preparation also have anti-leukocyte IgG
that can induce transient leukopenia.
Both CMV &
herpes infection can be seen after rATG-T ttt but rarely life threatening with current Prox antivirals. PTLD can also be reported. ATG-induced
serum sickness responding to Pph has
been also reported including one case with rapidly
progressive paralysis linked to serum
sickness. Rapid cure can be seen with therapeutic Pph. Previous exposure to rabbits may augment
the risk of developing serum sickness
with the 1st dose of rATG-T.
COMMENTS