Thesis (MScMedSc (Pathology. Medical Virology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: In 2007, AIDS caused an estimated 2.1 millions deaths worldwide; about 70% in sub-Saharan
Africa. HIV preferentially targets activated CD4 T cells, expressing the major HIV receptor
CD4, as well as the major chemokine coreceptors CCR5 and CXCR4. These coreceptors play
a prominent role during HIV cell entrance phase, HIV transmission and also disease
progression. They have been found to be differentially expressed by CD4 T cell subsets.
Tuberculosis coinfection may enhance immune activation in vivo thus accelerating HIV
disease progression and has become a major challenge in the control of TB in Africa.
Introduction of HAART has reduced disease progression to AIDS, as well as risk of further
morbidity and mortality. HAART results in a rapid decline of viral load and an initial increase
of peripheral CD4 count, however little is known on the effect of HAART in regulation of
coreceptor expression, immune activation status and CD4 T cell subset distribution in HIV
infection and HIV/TB coinfection.
This study is a cross-sectional analysis of coreceptor expression, immune activation status and
CD4 T cell subpopulation distribution in South African HIV and HIV/TB coinfected patients
before and after ARV. A total of 137 South African individuals were investigated, comprising
15 healthy normal donors (healthy subgroup), 10 patients with active pulmonary tuberculosis
(PTB subgroup), 33 HIV-1 positive patients without active PTB (HIV subgroup), 23 positive
patients with active PTB (HIV/PTB subgroup), 36 HIV-1 positive patients on ARV (HIV on
ARV subgroup) and 20 HIV-1 positive patients with active PTB on ARV (HIV/PTB on ARV
subgroup).
CD4 absolute count and plasma viral load were determined for all donors. Freshly isolated
PBMC were classified by flow cytometry into the following CD4+ T lymphocyte subsets:
naïve (CD45+, CD27+), effector memory (CD45-, CD27-), central memory (CD45-, CD27+),
and effector (CD45+, CD27-). Coreceptor expression and activation status was assessed by
CCR5, CXCR4 and CD38 expression on CD4 T cell subsets.
HIV, TB and HIV/TB coinfection was associated with a decrease in percentage CCR5+ T
cells as compared to healthy controls, with the HIV/TB group showing the most extensive
decrease. In treatment naive patients, CD4 T cells showed elevated surface expression of
CCR5 and CD38 as determined by mean fluorescence intensity in HIV/TB co-infection
compared to HIV infection alone. The percentage of antigen-experienced cells was higher in
the HIV/TB co-infected group compared to the HIV group. The percentage of naïve T cells
was decreased in both the HIV infected and the HIV/TB co-infected groups compared to
healthy controls. HIV patients with more than 6 months of ARV showed decreased CCR5 and
CD38 surface level expression in the HIV and the HIV/ TB co-infected subgroups. An
increased percentage of naïve T cells was observed in the HIV infected subgroup, but not in
the HIV/TB subgroup, similarly, a decreased percentage of antigen-experienced cells was
observed in the HIV subgroup, but not in the HIV/TB co-infected subgroup. A positive
correlation was found between CCR5 and CD38 expression, and CXCR4 and CD38
expression (Spearman coefficient of correlation respectively: r=0.59, p<0.001 and r=0.55,
p<0.001). Furthermore we found plasma viral load positively associated with CD38
expression (r=0.31, p<0.001) and percentage activated CCR5+ expressing CD4 T cells
positively related to viral load (r=0.31, p<0.001). Percentage naïve CD4 T cells was positively
associated with CD4 count (r=0.60, p<0.001) and negatively correlated to viral load (r=-0.42,
p<0.001).
These results indicate that TB coinfection exacerbates certain aspects of dysregulation of CD4
T cell homeostasis and activation caused by HIV infection. In addition, ARV-associated
decrease in coreceptor expression, immune activation status and a normalisation of CD4 T
cell subset distribution was observed in HIV infected individuals, but not in HIV/TB coinfection.
Despite viral suppression after ARV treatment, the decline in the immune activation
marker CD38 and coreceptor CCR5 expression, increase in percentage naïve CD4 T cells and
decrease of antigen-experienced cells did not reach the levels displayed in the healthy control
group. This may indicate that ongoing (albeit reduced) T cell immune activation may occur in
the presence of ARV. Further longitudinal studies are needed to closely monitor immune
activation during ARV treatment.
This study highlighted an association of TB disease with immune activation in HIV infection,
the importance of T-cell activation in HIV pathogenesis and its impact on ARV treatment.
Further studies are needed to identify causative factors that may lead to a persistent immune
activation status during ARV treatment, and how TB coinfection confounds normal responses
to ARV. / AFRIKAANSE OPSOMMING: In 2007 was ongeveer 2.1 miljoen sterftes wêreldwyd veroorsaak deur VIGS; ongeveer 70%
in Sub-Sahara Afrika. CD4 T selle is die hoof teiken van MIV, aangesien dit die primêre CD4
reseptor, sowel as een of beide van die vernaamste chemokien koreseptore CCR5 en CXCR4
vrystel. Hierdie koreseptore speel ‘n prominente rol wanneer die MIV die sel binnedring,
asook tydens MIV oordrag en verloop van die siekte. Dit word ook deur verskillende fraksies
van CD4 T selle vrygestel. Gelyktydige TB infeksie mag immuunaktivering in vivo verhoog
en dus die siekeproses versnel. MIV het ‘n groot uitdaging geword in die beheer van TB in
Afrika. Bekendstelling van HAART het die ontwikkeling van VIGS vertraag, asook die risiko
van verdere morbiditeit en mortaliteit. HAART veroorsaak ‘n vinnige afname in virale lading
‘n toename in CD4 telling, hoewel die spesifieke invloed van HAART op die regulering van
koreseptor vrystelling, immuunaktivering en verspreiding van CD4 fraksies in MIV en
MIV/TB infeksies nog onduidelik is.
Hierdie studie het gepoog om koreseptor vrystelling, immuunaktiveringstatus en die
verspreiding van CD4 subpopulasies in pasiënte met MIV en MIV/TB voor en na ARV
behandeling te ondersoek. ‘n Totaal van 137 Suid-Afrikaanse individue is ondersoek en die
studiegroep het bestaan uit 15 normale persone (gesonde subgroep), 10 pasiënte met aktiewe
pulmonale TB (PTB subgroup), 33 MIV positiewe pasiënte sonder PTB (MIV subgroep), 23
MIV positiewe pasiënte met aktiewe PTB (MIV/PTB subgroep), 36 MIV positiewe pasiënte
op ARV (MIV op ARV subgroep) en 20 MIV positiewe pasiënte met aktiewe PTB op ARV
(MIV/PTB op ARV subgroep).
Absolute CD4 telling en virale ladings was bepaal vir alle deelnemers. Vars geïsoleerde
perifere bloed mononukleêre selle is geklassifiseer deur middel van vloeisitometrie as die
volgende CD4 T limfosiet subgroepe: naïewe selle (CD45+, CD27+), effektor geheueselle
(CD45-, CD27-), sentrale geheueselle (CD45-, CD27+), en effektor selle (CD45+, CD27-).
Koreseptor vrystelling en aktivering was beoordeel volgens CCR5, CXCR4 en CD38
vrystelling op CD4 T sel subgroepe.
HIV, TB en MIV/TB ko-infeksie is geassosieer met ‘n afname in die persentasie CCR5+ T
selle, vergeleke met gesonde kontroles, waar die MIV/TB subgroep die grootste afname
getoon het. In onbehandelde pasiënte het die CD4 T selle verhoogde vrystelling van CCR5 en
CD38 op die oppervlakte getoon en dit is bevestig deur die gemiddelde fluoresserende
vii
intensiteit in die MIV/TB subgroep vergeleke met die subgroep met slegs MIV. Die MIV/TB
subgroep het verder ook ‘n verhoogde persentasie totale geheue T selle getoon vergeleke met
die MIV subgroep. Die persentasie naïewe T selle was egter verlaag in beide die MIV en
MIV/TB subgroepe vergeleke met normale kontroles. MIV pasiënte wat langer as 6 maande
op ARV behandeling was in beide die MIV en MIV/TB subgroepe, het ‘n verlaagde
vrystelling van CCR5 en CD38 op die oppervlakte van die CD4 selle getoon. ‘n Verhoogde
persentasie naïewe T selle het in die MIV subgroep voorgekom, maar nie in die MIV/TB
subgroup nie. ‘n Soortgelyke tendens is gevind waar die persentasie totale geheueselle
verlaag was in die MIV subgroep, maar nie in die MIV/TB subgroep nie. ‘n Positiewe
korrelasie is gevind tussen CCR5 en CD38 vrystelling, asook CXCR4 en CD38 vrystelling
(Spearman korrelasie koëffisiënt: r=0.59, p<0.001 en r=0.55, p<0.001 onderskeidelik). Verder
het die plasma virale lading ‘n positiewe assosiasie getoon met CD38 vrystelling (r=0.31,
p<0.001) en die persentasie geaktiveerde CCR5+ vrystellende CD4 T selle met virale lading
(r=0.31, p<0.001). Die persentasie naïewe CD4 T selle het ‘n positiewe assosiasie getoon met
CD4 telling (r=0.60, p<0.001) en ‘n negatiewe korrelasie met virale lading (r=-0.42,
p<0.001).
Volgens hierdie resultate vererger TB ko-infeksie sekere aspekte van die disregulasie van
CD4 T selhomeostase en aktivering as gevolg van MIV infeksie. Verder kon ‘n ARVgeassosieerde
afname in koreseptor vrystelling, immuunaktivering en normalisering van CD4
T sel fraksies bespeur word in die MIV subgroep, maar nie in die MIV/TB subgroep nie. Ten
spyte van virale onderdrukking veroorsaak deur ARV behandeling, het die afname in die
immuunmerker CD38 en koreseptor CCR5, toename in die persentasie naïewe CD4 selle en
afname in totale geheue CD4 T selle nie die vlakke van die normale kontrolegroep bereik nie.
Dit is moontlik dat volgehoue verlaagde T sel immuunaktivering nog steeds mag plaasvind in
die teenwoordigheid van ARV. Verdere longitudinale studies is nodig om immuunaktivering
tydens ARV behandeling te monitor.
Hierdie studie het die belangrikheid van T sel aktivering in MIV patogenese en dit impak
daarvan op ARV behandeling beklemtoon. Verdere studies is nodig om moontlike oorsake of
bydraende faktore te identifiseer wat tot volgehoue immuunaktivering tydens ARV
behandeling kan lei, asook tot mate waartoe TB ko-infeksie kan inmeng met die normale
werking van ARV behandeling.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/2219 |
| Date | 12 1900 |
| Creators | Ngandu, Jean Pierre Kabue |
| Contributors | De Beer, C., Glashoff, R. H., University of Stellenbosch. Faculty of Health Sciences. Dept. of Pathology. Medical Virology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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