http://cid.oxfordjournals.org/content/51/2/242.full.pdf

HIV/AIDS
MAJOR ARTICLE
Association of Toll-Like Receptor 4
Asp299Gly and Thr399Ile Polymorphisms
with Increased Infection Risk in Patients
with Advanced HIV-1 Infection
Antonios I. Papadopoulos,1 Bart Ferwerda,2 Anastasia Antoniadou,1 Vissaria Sakka,1 Lambrini Galani,1
Dimitra Kavatha,1 Periklis Panagopoulos,1 Garyphalia Poulakou,1 Kyriaki Kanellakopoulou,1
Jos W. M. van der Meer,2 Evangelos J. Giamarellos-Bourboulis,1 and Mihai G. Netea2
1
4th Department of Internal Medicine, University of Athens Medical School, Athens, Greece; and 2Department of Internal Medicine
and Center for Infectious Diseases, University St Radboud, Nijmegen Medical Center, Nijmegen, the Netherlands
Background. The Toll-like receptor 4 (TLR4) is an essential component of the innate immune response to
various microorganisms. We investigated the association between TLR4 polymorphism and the risk of acquiring
severe infections, in patients with human immunodeficiency virus (HIV)–1 infection.
Methods. The presence of TLR4 Asp299Gly and Thr399Ile single nucleotide polymorphisms (SNPs) was determined in a cohort of 199 HIV-1 infected patients and evaluated in relation to the occurrence of various infections.
Results. One hundred seventy-two patients were homozygous for the wild-type genotype; 22 patients (11%)
were heterozygous for both SNPs; 4 were heterozygous for 1 polymorphism; 1 patient was heterozygous for the
Asp299Gly SNP and homozygous for the Thr399Ile SNP. Of individuals with a nadir CD4 cell count of !100 cells/
mm3, those who carried both SNPs, compared with those who carried the wild-type genotype, demonstrated a
13-fold increase in the odds ratio (OR) of any serious infection (OR, 6.33 vs OR, 1.83, P p .043).
Conclusions. This study suggests an association between the presence of TLR4 Asp299Gly and Thr399Ile
polymorphisms and the occurrence of serious infections in HIV-1 infected patients with a history of nadir CD4
cell count of !100 cells/mm3.
Human immunodeficiency virus type 1 (HIV-1) infection is characterized by a gradual dysfunction, mainly
in cell-mediated immunity but also in humoral immunity, attributable to CD4 lymphocyte depletion,
leading to high levels of HIV RNA and development
of opportunistic disease [1]. Chronic persistent immune activation has been implicated in the pathogenesis of HIV infection and the progression to AIDS [2].
An intact innate immune system may play a significant
role in controlling chronic inflammation and may influence the occurrence of opportunistic diseases [3, 4].
Received 10 December 2009; accepted 4 April 2010; electronically published 3
June 2010.
Reprints or correspondence: Dr Antonios I. Papadopoulos, 4th Dept of Internal Medicine, Attikon University Hospital, 1 Rimini St, Athens 12462, Greece
([email protected]).
Clinical Infectious Diseases 2010; 51(2):242–247
2010 by the Infectious Diseases Society of America. All rights reserved.
1058-4838/2010/5102-0018$15.00
DOI: 10.1086/653607
242 • CID 2010:51 (15 July) • HIV/AIDS
Toll-like receptors (TLRs) are transmembrane receptors that activate cells of the innate immune systems
upon recognition of pathogen-associated molecular
patterns [4–6]. When activated, TLRs interact with various adaptor proteins that orchestrate a series of cascade
reactions leading to induction of suppression of genes
involved in the inflammatory process [5–8]. At the
present time, 10 TLRs (TLR1-TLR13) have been identified in humans [9, 10]. One of the best-studied TLRs
is TLR4, which recognizes lipopolysaccharide of gramnegative bacteria, mannans of fungal pathogens, ligands
of Mycobacterium tuberculosis and Plasmodium species,
as well as endogenous ligands, such as fibronectin, oxidized low density lipoproteins, and heat shock proteins
[11, 12].
The interaction of lipopolysaccharide with TLR4,
through the soluble protein MD2, initiates a downstream intracellular signaling transduction through
adaptor molecules that induces production of inflammatory cytokines such as tumor necrosis factor–a, in-
terleukin 1b, interleukin 6, and interleukin 8 [9, 13]. TLR4
plays a role not only in the immune reaction against infectious
microorganisms but also perhaps in the inflammatory processes
of other inflammatory diseases, such as atherosclerosis or diabetes mellitus [14].
Studies in mice and humans have demonstrated an increased
susceptibility to infection when mutations in genes encoding
TLRs or downstream signaling proteins exist [14, 15]. Several
single nucleotide polymorphisms (SNPs) in various TLR genes,
such as TLR2, TLR4, TLR5, TLR6, TLR9, and TLR10, have
been associated with disease susceptibility [14]. TLR4 SNPs
have been studied more extensively. Among them, 2 nonsynonymous SNPs are more prevalent, an A/G transition at SNP
rs4986790 that causes the substitution of aspartic acid by glycine at amino acid position 299 (Asp299Gly) and a C/T transition at SNP rs4986791 that causes the substitution of threonine by isoleucine at amino acid position 399 (Thr399Ile).
Some studies have suggested an association of those SNPs with
susceptibility to various conditions and diseases, including infections with gram-negative bacteria, septic shock, endotoxemia, disseminated candidiasis, invasive aspergillosis, respiratory syncytial virus infection, meningeal disease, bacterial
vaginosis, premature birth, brucellosis, coronary heart disease,
asthma, hematogenous osteomyelitis, and Plasmodium falciparum infections [11–14, 16–19]. Other studies have shown
that carriage of both SNPs is associated with decreased incidence of atopy and hay fever as well as protection against
legionnaires disease and atherosclerosis [14, 20, 21].
Only a few recent studies have investigated the role of TLR
SNPs in the susceptibility to infections of patients infected with
HIV. The TLR9 1635 A/C polymorphism has been associated
with low CD4 cell count, increased viral load, and more rapid
clinical progression [22]. Another study confirmed these findings and extended to the 1174G/A SNP in TLR9 that was also
associated with the rapid progressor phenotype [23]. A higher
susceptibility to active tuberculosis has been shown in HIVinfected patients in Tanzania who carry the TLR4 Asp299Gly
SNP [24].
We hypothesized that polymorphisms in TLR4 genes may
be associated with an increased susceptibility to severe infections in HIV-infected patients. To test this hypothesis, we analyzed the frequencies of the 2 common TLR4 SNPs, Asp299Gly
and Thr399Ile SNP of the TLR4 gene, in a Greek cohort of
patients with HIV infection.
METHODS
Patients. The study population consisted of 199 white, HIV1 infected adults ⭓18 years old, who were recruited from a
cohort of patients attending the AIDS Unit of the 4th Department of Internal Medicine of the University of Athens
(Greece), at University General Hospital Attikon, a tertiary care
center. Blood specimens were obtained during patients’ regular
visits after enrollment. Patients lost to follow-up or with missing data concerning demographics, clinical evolution, antiretroviral therapy administration, or laboratory parameters were
excluded.
Data were extracted from our electronic database, which is
comprised of patients for whom clinical data were available
since 1986. The following data were recorded: age, sex, stage
of HIV infection, nadir CD4 cell count, maximum HIV-RNA
levels, status with regard to highly active antiretroviral therapy
(naive or experienced), and history of documented infectious
diseases. The stage of the disease was recorded in accordance
with the expanded European AIDS case definition [25]. Important infections that occurred at the time of or after the
diagnosis of HIV-1 infection were also recorded. Included were
serious opportunistic infections that fulfilled the case definition
of the Centers for Disease Control and Prevention, such as
Pneumocystis jirovecii pneumonia, tuberculosis due to M. tuberculosis or Mycobacterium avium complex, cerebral toxoplasmosis, cytomegalovirus retinitis, progressive multifocal leukoencephalopathy due to JC virus, salmonella bacteremia, and
bacterial pneumonia due to Streptococcus pneumoniae or Pseudomonas aeruginosa [26]. Other important infectious diseases,
such as syphilis or community-acquired pneumonia, were also
recorded. Community-acquired pneumonia was diagnosed in
accordance with previously defined criteria [27].
Written informed consent was obtained from all patients.
The study was approved by the ethics committee of Attikon
University Hospital. All clinical research was conducted in accordance with the principles of the Helsinki Declaration.
Laboratory procedures. Routine CD4 cell count was determined using conventional flow cytometry with fresh blood
samples from all patients. Plasma HIV-1 RNA was also routinely measured by the quantitative branch DNA method (Roche
Diagnostic Systems), in accordance with the manufacturer’s
instruction.
TLR4 genotyping DNA was extracted from whole blood in
accordance with the manufacturer’s instructions from the isolation kit Puregene (Gentra Systems). Polymerase chain reaction (PCR) assays were performed using 50 ng of genomic DNA
at a final volume of 27 ml with 50 mM of MgCl2 (Invitrogen),
20 mM of deoxynucleotide triphosphates (Invitrogen), and 1
mM of Taq polymerase (Invitrogen). For the Asp299Gly polymorphism, the sense primer 5’-ATA CTT AGA CTA CTA CCT
CCA TG and the antisense primer AGC CTT TTG AGA GAT
TTG AGT-3’ were used. PCR consisted of 1 initial denaturation
phase of 95C for 5 min followed by 40 cycles; each cycle
consisted of 1 annealing step of 95C for 1 min, 1 polymerization step of 52C for 1 min, and 1 elongation step of 72C
for 1 min. Then, another cycle of 72C for 7 min was performed
before termination. Ten ml of the PCR product were digested
HIV/AIDS • CID 2010:51 (15 July) • 243
Table 1. Characteristics of a Cohort of 199 Patients Infected with Human Immunodeficiency Virus–1 and Studied in Relation to Single
Nucleotide Polymorphisms of Toll-Like Receptor 4
Wild type
(n p 172)
Characteristic
Male-to-female ratio
Age,a mean years SD
Stage C
HAART-naive–to–HAART-experienced ratio
a
Nadir CD4 cell count, mean cells/mm3 SD
a
Maximum viral load, median copies/mL
Asp299Gly HT +
Thr399Ile HT
(n p 22)
Asp299Gly HT
(n p 2)
Thr399Ile HT
(n p 2)
Asp299Gly HT +
Thr399Ile
homozygous
(n p 1)
142:30
18:4
2:0
1:1
0:1
41.4 11.3
32
30:142
38.9 9.6
4
3:19
30.0 1.4
0
0:2
50.0 1.4
0
1:1
30
0
0:1
237.4 141.3
252.2 130.8
196.0 19.7
364.5 78.5
222
66,391
74,400
50,856
184,697
46,900
Note. HAART, highly active antiretroviral therapy; HT, heterozygous; SD, standard deviation.
a
Difference between groups not significant by analysis of variance.
after incubation for 60 min at 37C with 0.5 units of the restriction enzyme NCO1 (BioLabs). The digestion product was
evaluated after 2% agarose gel electrophoresis and ethidium
bromide staining.
For the Thr399Ile polymorphism, the sense primer 5’-GCT
GTT CTC AAA GTG ATT TTG GGA and the antisense primer
CAC TCA TTT GTT TCA AAT TGG AAT G-3’ were used.
PCR consisted of 1 initial denaturation phase of 95C for 4
min followed by 35 cycles; each cycle consisted of 1 annealing
step of 95C for 30 sec, 1 polymerization step of 56C for 30
sec, and 1 elongation step of 72C for 30 sec. Then, another
cycle of 72C for 7 min was performed before termination. Ten
ml of the PCR product was digested after incubation for 60 min
at 37C with 0.5 units of the restriction enzyme Hinf1 (BioLabs). The digestion product was evaluated after 2% agarose
gel electrophoresis and ethidium bromide staining.
Statistical analysis. Quantitative characteristics were expressed by their mean value standard deviation (SD) for
normally distributed values and by their median value for nonnormally distributed values. A nadir CD4 cell count !100 cells/
mm3 was defined as a common risk for the advent of any
infection and was evaluated by the Mantel-Haenzel statistic.
Odds ratios (ORs) and 95% confidence intervals (CIs) for the
advent of an infection were estimated. Comparisons of ORs
were calculated by the Breslow-Day and Tarone tests.
RESULTS
The study included 199 HIV-1 infected patients, who were
assessed for the presence of TLR4 Asp299Gly and Thr399Ile
polymorphisms. The characteristics of the patients at study
entry are presented in Table 1. The study population comprised
163 males (82%) and 36 females (18%), with a mean age
(SD) of 4111 years. Thirty-six patients (18%) were in
stage C.
The distribution of TLR4 polymorphisms is also shown in
Table 1; 172 (86%) patients were bearing the wild-type (WT)
244 • CID 2010:51 (15 July) • HIV/AIDS
genotype; 22 patients (11%) were heterozygous for both
Asp299Gly and Thr399Ile SNP; 2 patients were heterozygous
for the Asp299Gly SNP alone; 2 patients were heterozygous for
the Thr399Ile SNP alone; and 1 patient was heterozygous for
the Asp299Gly SNP and homozygous for the Thr399Ile SNP.
Further statistical analysis was focused on patients bearing the
WT genotype and on patients heterozygous for both SNPs.
Overall, 92 infections occurred during the disease history of
55 patients. These infections occurred in 6 (27%) of the 22
patients heterozygous for both SNPs and in 49 (28%) of the
172 patients bearing the WT genotype (Table 2) (not significant). No difference was found between carriers of the WT
genotype and patients heterozygous for both SNPs with regard
to intake of prophylaxis medications, namely trimethoprimsulfamethoxazole (P p .378), macrolides (P p .459), and azoles (P p .615), or with regard to history of antipneumococcal
vaccination (P p .552).
Among patients bearing the WT genotype, the OR for the
advent of an infection for patients with a history of nadir CD4
cell count of !100 cells/mm3, compared with patients with a
history of nadir CD4 cell count ⭓100 cells/mm3, was 1.83 (95%
CI, 1.14–2.93). This OR was changed to 6.33 (95% CI, 2.24–
17.89) when analysis comprised patients carrying both SNPs
of TLR4. A statistically significant difference was found between
the ORs of the 2 populations (P p .043 by the Breslow-Day
test; P p .043 by the Tarone test) (Table 3). No other cut-off
of CD4 cell counts was determined to be associated with an
impact of carriage of TLR4 SNPs.
Among the 27 cases of community-acquired pneumonia, S.
pneumoniae was defined with certainty as a cause in 3 patients,
although we cannot completely exclude it as an etiological agent
in more of the cases. All 3 patients were bearing only WT alleles
for the studied SNPs. No legionnaires disease was recorded.
The time of seroconversion was known for only 18 patients
of the entire cohort; 15 were heterozygous for both SNPs and
3 bore both WT alleles. Of the 15 patients heterozygous for
Table 2. History of Infections and Measures of Prophylaxis in 199 Human Immunodeficiency Virus–Infected Patients in
Relation to Single Nucleotide Polymorphisms of the Toll-Like Receptor 4 Gene
No. (%) of patients
Variable
Wild type
(n p 172)
Asp299Gly HT +
Thr399Ile HT
(n p 22)
History of infections
Pneumocystis jirovecii pneumonia
11 (6.4)
2 (9.1)
0 (0)
0 (0)
0 (0)
Community-acquired pneumonia
Salmonellosis
25 (14.5)
1 (0.6)
2 (9.1)
1 (4.5)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
Tuberculosis
Mycobacterium avium complex
9 (5.2)
1 (0.6)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
Toxoplasmosis
Cytomegalovirus
1 (0.6)
2 (1.2)
1 (4.5)
2 (9.1)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
PML
Candidiasisa
Syphilis
Any
Prophylaxis measure
TMP-SMX
Macrolides
Azoles
Pneumococcal vaccination
Asp299Gly HT
(n p 2)
Thr399Ile HT
(n p 2)
Asp299Gly HT +
Thr399Ile homozygous
(n p 1)
2 (1.2)
1 (4.5)
0 (0)
0 (0)
0 (0)
18 (10.5)
11 (6.4)
49 (28)
1 (4.5)
1 (4.5)
6 (27)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
35 (20.3)
2 (9.1)
0 (0)
0 (0)
0 (0)
15 (8.7)
4 (2.3)
76 (44.2)
1 (4.5)
0 (0)
10 (45.4)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
1 (50)
0 (0)
0 (0)
0 (0)
Note. HT, heterozygous; PML, progressive multifocal leukoencephalopathy; TMP-SMX, trimethoprim-sulfamethoxazole.
a
Oropharyngeal or esophageal.
both SNPs, 10 (66.7%) had started highly active antiretroviral
therapy at the time of seroconversion (P p .350 ) and 2 (13.3%)
developed an infection (P p .686). Of the 3 patients who bore
both WT alleles, 3 (100%) had started highly active antiretroviral therapy at the time of seroconversion (P p .350) and
none developed an infection (P p .686).
Nine malignant neoplasms occurred (6 cases of B-cell nonHodgkin lymphoma and 3 cases of anal carcinoma), all among
patients bearing both WT alleles (5%). The difference between
patients bearing only the WT genotype and those heterozygous
for both SNPs was not significant (P p .330).
DISCUSSION
To our knowledge, this study represents the first effort to demonstrate how a haplotype containing 2 commonly segregated
polymorphisms of the human TLR4 gene, the Asp299Gly and
the Thr399Ile SNPs, influences the occurrence of serious infections in patients with advanced HIV-1 infection. Results revealed that the carriage of both SNPs was associated with an
increased risk for the advent of infections.
Studies to evaluate the role of TLR4 polymorphisms in the
course of HIV-1 infection have been limited [24]. In line with
Table 3. Toll-Like Receptor 4 (TLR4) Asp299Gly and Thr399Ile Polymorphisms in
194 Human Immunodeficiency Virus–1 Infected Patients Stratified according to CD4
Cell Count and the History of Any Infection
Presence of TLR4 single nucleotide
polymorphisms, by nadir CD4 cell count
No. of
patients
History of infection,
no. (%) of patients
Yes
No
Wild type
!100 cells/mm3
⭓100 cells/mm3
Asp299Gly HT + Thr399Ile HT
!100 cells/mm3
⭓100 cells/mm3
36
16 (44%)
20 (56%)
136
33 (24%)
103 (76%)
3
3 (100%)
0 (0%)
19
3 (16%)
16 (84%)
HIV/AIDS • CID 2010:51 (15 July) • 245
this, we have observed that in HIV-infected patients with normal or moderately decreased CD4 cell counts, no major differences in terms of infections have been observed in relation
to the presence of TLR4 polymorphisms. However, in individuals with CD4 cell counts !100 cells/mm3, those patients bearing TLR4 polymorphisms had a significant increase in the risk
of occurrence of a severe infection. This effect is likely attributable to the attenuation of an effective adaptive cellular response due to low CD4 cell counts and to an increase in the
relative importance of innate host defense. Furthermore, the
in vitro activation and signaling through TLR2, TLR4, and
TLR9 might facilitate HIV replication. Increased expression of
TLR2, TLR3, and TLR4 on the cell membrane of monocytes
has been demonstrated in advanced stages of HIV-1 infection
and especially in patients with a CD4 cell count !200 cells/
mm3 [22, 28]. Moreover, microbial translocation from the gut
flora to circulation has recently been considered to be a major
cause of systemic activation, and this effect is probably mediated
through TLRs-dependent signaling [29, 30]. Subsequently, on
the one hand, TLR4 polymorphisms may modulate the systemic
inflammatory response to translocated lipopolysaccharide, with
many (although by no means all) studies suggesting a lower
inflammatory response in individuals bearing the polymorphisms described in the present study [13]. On the other hand,
HIV RNA may also influence the response to microbial translocation through TLR4 signaling and may promote the cycle
of immune activation [31]. It may be tempting to speculate
whether the presence of TLR4 SNPs would prove to be protective against this circle of infection-inflammation, but this
remains to be demonstrated. This generalized activation may
ultimately lead to exhaustion of the immune system and to the
subsequent development of opportunistic and other infections.
If the latter hypothesis is true, it may in part explain the present
findings.
Scant evidence exists about a role of TLR4 SNPs in the course
of HIV-1 infection. It has been suggested that TLR4 Asp299Gly
polymorphism may facilitate more intense viral replication with
concomitant CD4 cell loss and increased susceptibility to infection from M. tuberculosis [24]. However, a more direct effect
of TLR4 polymorphisms on the release of proinflammatory mediators, induced by ligands from the invading pathogen, may
be an alternative explanation for the effects found, because
defective cytokine release by cells of individuals with TLR4
polymorphisms has been reported by some, although not all,
of the studies [13].
Three main limitations of this study may be recognized: (1)
the retrospective nature of data collection, (2) the limited number of patients with CD4 cell count !100 mm3 bearing both
TLR4 SNPs, and (3) the fact that all major infections were
collectively analyzed. The relatively low number of each type
of infection precluded us from analyzing separately the role of
246 • CID 2010:51 (15 July) • HIV/AIDS
TLR4 polymorphisms on each specific infection. However, our
cohort consisted of a homogenous white population with similar demographic characteristics, with a long and consistent
follow-up. The patients were also consecutively tested at random, with no selection bias. The presented findings suggest a
role of TLR4 SNPs for the advent of serious infections during
the progression of HIV-1 infection. A point that one should
always bear in mind is that factors other than SNPs, namely
CD4 cell count and viral load, impinge considerably on the
physical course of HIV-1 infected individuals. Additional casecontrol studies in the future, with HIV-negative patients bearing
serious infections, may provide a concise conclusion about the
role of TLR4 SNPs for the advent of serious infections among
HIV-infected individuals with low CD4 cell counts.
In conclusion, this study suggests an association between
TLR4 haplotypes segregated together and an increased risk of
serious infections in patients with HIV-1 infection. The present
results may influence future strategies concerning disease surveillance and antibiotic prophylaxis of opportunistic infections.
Acknowledgments
Financial support. Netherlands Organization for Scientific Research
(Vidi grant to M.G.N.).
Potential conflicts of interest. All authors: no conflicts.
References
1. Cohen DE, Walker BD. Human immunodeficiency virus pathogenesis
and prospects for immune control in patients with established infection. Clin Infect Dis 2001; 32:1756–1768.
2. Sodora DL, Silvestri G. Immune activation and AIDS pathogenesis.
AIDS 2008; 22:439–446.
3. Noursadeghi M, Katz DR, Miller RF. HIV-1 infection of mononuclear
phagocytic cells: the case for bacterial innate immune deficiency in
AIDS. Lancet Infect Dis 2006; 6:794–804.
4. Barton GM, Medzhitov R. Toll-like receptor signaling pathways. Science
2003; 300:1524–1525.
5. Sanders CM, Cruse JM, Lewis RE. Toll-like receptors, cytokines and
HIV-1. Exp Mol Pathol 2008; 84:31–36.
6. Takeda K, Akira S. Toll-like receptors in innate immunity. Int Immunol
2005; 17:1–14.
7. Akira S, Uematsu S, Takeuchi O. Pathogen recognition and innate immunity. Cell 2006; 124:783–801.
8. Beutler B. Inferences, questions and possibilities in Toll-like receptor
signalling. Nature 2004; 430:257–263.
9. Kawai T, Akira S. TLR signaling. Cell Death Differ 2006; 13:816–825.
10. Poltorak A, He X, Smirnova I, et al. Defective LPS signaling in C3H/
HeJ and C57BL/10ScCr mice: mutations in TLR4 gene. Science 1998;
282:2085–2088.
11. Netea MG, Van Der Graaf CA, Vonk AG, et al. The role of Toll-like
receptor (TLR) 2 and TLR4 in the host defense against disseminated
candidiasis. J Infect Dis 2002; 185:1483–1489.
12. Ferwerda B, McCall MB, Alonso S, et al. TLR4 polymorphisms, infectious diseases, and evolutionary pressure during migration of modern humans. Proc Natl Acad Sci U S A 2007; 104:16645–16650.
13. Ferwerda B, McCall MB, Verheijen K, et al. Functional consequences
of Toll-like receptor 4 polymorphisms. Mol Med 2008; 14:346–352.
14. Schröder NW, Schumann RR. Single nucleotide polymorphisms of
Toll-like receptors and susceptibility to infectious disease. Lancet Infect Dis 2005; 5:156–164.
15. Pamer EG. TLR polymorphisms and the risk of invasive fungal infections. N Engl J Med 2008; 359:1836–1838.
16. Arbour NC, Lorenz E, Schutte BC, et al. TLR4 mutations are associated with endotoxin hyporesponsiveness in humans. Nat Genet 2000;
25:187–191.
17. Bochud PY, Chien JW, Marr KA, et al. Toll-like receptor 4 polymorphisms and aspergillosis in stem-cell transplantation. N Engl J Med
2008; 359:1766–1777.
18. Carvalho A, Pasqualotto AC, Pitzurra L, et al. Polymorphisms in Tolllike receptor genes and susceptibility to pulmonary aspergillosis. J Infect
Dis 2008; 197:618–621.
19. Van der Graaf CA, Netea MG, Morré SA, et al. Toll-like receptor 4
Asp299Gly/Thr399Ile polymorphisms are a risk factor for Candida
bloodstream infection. Eur Cytokine Netw 2006; 17:29–34.
20. Senthilselvan A, Rennie D, Chénard L, et al. Association of polymorphisms of Toll-like receptor 4 with a reduced prevalence of hay fever
and atopy. Ann Allergy Asthma Immunol 2008; 100:463–468.
21. Hawn TR, Verbon A, Janer M, Zhao LP, Beutler B, Aderem A. Tolllike receptor 4 polymorphisms are associated with resistance to legionnaires disease. Proc Natl Acad Sci USA 2005; 102:2487–2489.
22. Soriano-Sarabia N, Vallejo A, Ramı́rez-Lorca R, et al. Influence of the
Toll-like receptor 9 1635A/G polymorphism on the CD4 count, HIV
viral load, and clinical progression. J Acquir Immune Defic Syndr 2008;
49:128–135.
23. Bochud PY, Hersberger M, Taffé P, et al. Polymorphisms in Toll-like
24.
25.
26.
27.
28.
29.
30.
31.
receptor 9 influence the clinical course of HIV-1 infection. AIDS 2007;
21:441–446.
Ferwerda B, Kibiki GS, Netea MG, et al. The Toll-like receptor 4
Asp299Gly variant and tuberculosis susceptibility in HIV-infected patients in Tanzania. AIDS 2007; 21:1375–1377.
Ancelle-Park R. Expanded European AIDS case definition. Lancet 1993;
341:441.
1993 Revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescents and adults. MMWR
Recomm Rep 1992; 41(RR-17):1–19.
Christ-Crain M, Stolz D, Bingisser R, et al. Procalcitonin guidance of antibiotic therapy in community-acquired pneumonia: a randomized trial.
Am J Resp Crit Care Med 2006; 174:84–93.
Lester RT, Yao XD, Ball TB, et al. Toll-like receptor expression and responsiveness are increased in viraemic HIV-1 infection. AIDS 2008; 22:
685–694.
Báfica A, Scanga CA, Schito M, et al. Influence of coinfecting pathogens
on HIV expression: evidence for a role of Toll-like receptors. J Immunol
2004; 172:7229–7234.
Brenchley JM, Price DA, Schacker TW, et al. Microbial translocation is
a cause of systemic immune activation in chronic HIV infection. Nat
Med 2006; 12:1365–1371.
Lester RT, Yao XD, Ball TB, et al. HIV-1 RNA dysregulates the natural
TLR response to subclinical endotoxemia in Kenyan female sex-workers. PLoS One 2009; 4:e5644.
HIV/AIDS • CID 2010:51 (15 July) • 247