Signals

From Signals, Virtcr 1995
Interpreting Changes in Viral Load

The growing use of plasma HIV1 RNA levels in making treatment decisions has highlighted
the need to understand what constitutes a significant change in viral
load. Signals spoke with Dr. Mark
Holodniy (Director, AIDS Research
Center, VA Medical Center, Palo
Alto, CA) to better understand the
factors that produce changes in viral
load and the significance of those
changes.
"Viral load is now becoming
routine in the treatment paradigm," stated Holodniy. "But, when
interpreting results, it is important
to take into account all the factors
that impact viral burden."
"In order to understand what
qualifies as a significant change in
viral load, it is important to recognize the normal variability of the
viral load itself and the assay used
to measure it," continued Holodniy. "Precision data for the bDNA
assay indicates that when monitoring viral load in clinically stable
patients, there is approximately a
2-fold (0.3 log) variation in virus
levels. This takes into account both
the natural variation of viral load
in the patient and the variation of
the assay." 7,2
Consequently, many researchers, including Holodniy, consider
a 3-fold (0.5 log) or greater change
in viral load to be significant.'
Dr. Holodniy continues, "Cer
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Weeks of Testing
Figure 10. Graph represents simulated administration of flu vaccine on a clinically stable patient.
Vaccination may produce a transient rise in viral load that returns to pre-vaccination level within
4-6 weeks.

tamo things, such as disease progression and drug resistance perturb stable viral levels. Studies
have shown that current antiviral
therapies reduce viral burden by as
much as 0.5-2 logs." 1,2
When assessing a patient's disease activity and response to antiviral therapy, Holodniy recommends
measuring viral, load, "One of the
greatest utilities of the bDNA assay
is that it provides a tool for individualizing therapy to reduce viral
load."
"In using viral load to guide
treatment decisions, it is crucial
to consider not only the things that
produce long-term changes in virus
levels, but also understand those
factors that cause temporary changes
in viral load," said Holodniy.
"Some vaccines, such as those
used for influenza, stimulate viral

replication and result in significant
transient increases in viral burden."
Other researchers report that
administration of the influenza
vaccine instigates a 4-fold (0.6 log)
increase in viral load that peaks 2
weeks post vaccination, with the
majority of patients returning to
baseline within 4-6 weeks following vaccination. 4-8
Figure 10 simulates a typical
change caused by the administration of the flu vaccine in a clinically
stable patient with HIV disease. 4-s
According to Holodniy, "Similar trends might appear in virus
levels following the administration
of measles and hepatitis vaccines
as well. And data suggests that
activation of herpes simplex infection and some opportunistic
infections produce similar changes
Continued on page 6

VIIRAL LOAD' 'IIN REV 4IEW, FROM ~I J~tiPA
7 years of research have established clinical utility
Many of us were cautious when we first heard that virus levels could be
used as a marker for HIV disease. We've been disappointed by new assays
before, i.e. p24 and beta-2 microglobulin. One thing is now clear-viral load is
not p24.
In the last two years, there's been a lot of debate about the clinical utility
of monitoring viral load. We've learned much from the groundbreaking
research by Ho, Mellors, Saag, Shaw, Holodniy, Coombs, and many others.
An important point that has been missed in most debates is this-Viral load
is not a new concept.
Since 1989, laboratory research has consistently proved that patients
with lower levels of virus do better than patients with high levels of virus.'2
The thing that is new is this-We now have assays that can consistently and
reproducibly quantify viral load.
These assays have accelerated our ability to understand the AIDS virus
and made it possible to quickly evaluate new antiviral therapies.
Monitor viral load to individualize therapy
From the perspective of the physician managing therapy, viral load is an
excellent marker for HIV disease because viral load:
Correlates with disease progression and clinical outcome
Changes rapidly with the initiation of effective therapy
Measures the underlying process that drives disease pathogenesis-viral
replication
The majority of doctors-not just those on the cutting edge of AIDS treatment and research-will be monitoring the viral burdens of their HIV
patients. In January of this year, the "Consensus Conference on Laboratory
Markers in HIV Infection" in Rome3 recommended
Monitor the viral load of all patients
Initiate therapy when virus levels exceed 10 KEq/mL*, regardless of
CD4+ cell counts
Monitor virus levels every 3-4 months to identify signs of drug resistance
Use alternative therapies when viral burdens return to near baseline levels
What still needs to be done
Two things need to happen before all patients have access to viral load tests.
Private insurers, Medicaid, and Medicare need to acknowledge that viral
load is a standard of care in AIDS treatment and then approve reimbursement for these tests.
*The FDA has acknowledged the importance of viral load. The agency
needs to continue to expedite approval of these viral load assays just as
they have expedited the approval of the new protease inhibitors.
In the meantime, there is much that can be done. Physicians can start
monitoring the viral load of their patients today just as many of you are
already doing (Figure 12). The bDNA viral load assay is available through
Corning Clinical Laboratories and SmithKline Beecham Laboratories
(through special arrangements with the Chiron Reference Testing Lab).
Growth in bDNA Testing

CASE STUD

1 () 1":i a I. N f ' 1995

bDNA and Drug Resistance

41-year-old telecommunications executive had assumed
he was HIV positive since
1985 but had avoided medical
care and serological testing. After
being successfully treated for PCP,
he underwent a thorough baseline
evaluation in April, 1991.
Treatment history
The physical examination disclosed thrush (after having been
on antibiotics) and axillary adenopathy. The CD4+ cell count was
146. He also had symptoms of
increasing fatigue and unwanted
weight loss.
In July, 1991, combination
therapy with AZT (200 mg 3x
daily) and ddC (0.75 mg 3x daily)
was started. Within one month, he
stated that he felt better than he
had for over a year. By October,
1991, his CD4+ cell count had
increased to 306.
Over the next three years, the
patient was gainfully employed
with a rigorous work schedule.

He remained clinically stable,
and his CD4+ cell count was measured every 3-4 months showing
little overall change.
In July, 1994, he was pleased
with his excellent clinical course
but concerned about reports
regarding AZT resistance. Because
he had been on the same drugs
for 37 months, he was considering changing his antiviral therapy
to another regimen. Without clinical or laboratory indication for
change, we decided to continue
the present course of therapy.
In October, 1994, the first
measurement of viral burden by
bDNA was obtained with a result
of 166 KEq/mL.* Considering his
clinical condition, this seemed surprisingly high. A second result of
204 KEq/mL one month later confirmed a high level of virus.
In January of 1995, he stopped
AZT and ddC and began monotherapy with D4T (40 mg 2x
daily). His bDNA level was 212
KEq/mL, and his CD4+ cell count
- 700
600
HIV-1 RNA - 5nn

was 281. One month later, his viral
load dropped 4-fold to 52 KEq/mL,
and his CD4+ cell count was 269.
Over the next four months, his
CD4+ cell count remained stable,
and his viral load dropped below
10 KEq/mL. He remains on D4T
and PCP prophylaxis, and he continues to be asymptomatic.
Dr. Joseph's comments
This case is a good example of
how an increase in viral load may
indicate developing resistance to an
antiviral regimen. In this patient,
the lack of symptoms and stable
CD4+ cell count were encouraging;
however, they did not give the full
picture. The high viral load signaled developing resistance to AZT
and ddC while the CD4+ cell count
remained stable. A more rational
approach to changing therapy was
made with the added information
provided by bDNA testing.
Once a change in therapy was
initiated, viral load was monitored
within 4-6 weeks to see the immediate impact of the drug on viral
replication. If CD4+ cells alone
were monitored, we may have had
to wait months to see the drug's
impact. This patient's response to
D4T followed the course that pre+ vious studies have shown - a
0
4-fold drop in viral load that was
associated with a rise in CD4+ cell
count. I will continue to measure
bDNA levels and CD4+ cell counts
every three months throughout the
course of this therapy.

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Figure 12. Increasing bDNA testing demonstrates acceptance of viral load to evaluate new drugs
and monitor therapy.
To get reimbursement, physicians can work with their patients to convince the medical directors of HMOs and insurance companies that viral
load testing is a medical necessity.
You can start by sending them this newsletter. If you'd like extra copies,
call 1-800-653-1353, and just tell us how many you need.
You can also call the Chiron Reimbursement Service at 1-800-775 -7533. This service has been established to help physicians and their
patients get coverage for bDNA testing.
We will keep you informed on developments in viral load testing.
References:
1 Ho et al. Quantitation of human immunodeficiency virus type 1 in the blood of infected persons. N EnglJ Med
1989; 321:1621-5
2 Coombs et al. Plasma viremia in human immunodeficiency virus infection. N EnglJ Med 1989; 321:1626-32
3 Saag et al. High-level viremia in adults and children infected with human immunodeficiency virus: relation to
disease stage and CD4+ lymphocyte levels. J Infect Dis 1991;164:72-80
4 Semple et al. Direct measurement of viraemia in patients infected with HIV-1 and its relationship to disease progression and zidovudine therapy J Med Virol 1991:35:38-45
5 Pachl et al. Quantitative detection of HIV RNA in plasma using a signal amplification probe assay. XXXII Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC). Anaheim, October, 1992
8 Mellors & Gupta. Presented at the 9th International Conference on AIDS in Berlin, 1993
7 Vahey et al. Presented at the 10th International Conference on AIDS in Yokohama, August, 1994
8 Cao et al. Virologic and immunologic characterization of long-term survivors of human immunodeficiency virus
type 1 infection. N EnglJ Med 1995; 332:201-208.
8 Ho et al. Rapid turnover of plasma virions and CD4 lymphocytes in HIV-1 infection. Nature 1995; 373:123-126
18 Wei et al. Viral dynamics in human immunodeficiency virus type 1 infection. Nature 1995; 373:117-122
1 Jackson et al. Presented at the National Conference on Human Retroviruses, February, 1995
12 Mellors et al. Quantitation of HIV-1 RNA in plasma predicts outcome after seroconversion. Ann Intern Med
1995;122:573-579
13 Aluti, Boucher, Dianzani, Fenyo, Ho, Lane, Lange, Montaner, Pantaleo, Pertin, Romagnani, Saag, Schooley,
Vella. Consensus Conference on Laboratory Markers in HIV Infection in Rome, January 16, 1996
14 Third Conference on Retroviruses & Opportunistic Infections, January, 1996
15 Volberding. HIV quantification: clinical applications. Lancet 1996; 347:71-73

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Months

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Figure 11. bONA levels and CD4+ cell counts were monitored as shown above. The elevated viral load
suggested that the patient had developed resistance to antiviral therapy. Following the initiation of new
therapy, the viral load decreased significantly and remained stable.

*HIV-1 RNA kilo equivalents/milliliter of plasma as measured by branched DNA (bDNA) direct quantification. A kilo equivalent 1,000 molecules of HIV-1 RNA.

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