Toxoplasmic encephalitis: role of HLA markers associated with rapid progression to AIDS

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The Brazilian Journal of


1 Original article

2 Toxoplasmic encephalitis: role of HLA markers

3 associated with rapid progression to AIDS

4 qi Maria de Lourdes Rodriguesa, Neifi Hassam Deghaideb, José Fernando Figueiredob,

5 Marcelo Bezerra de Menezesa, Ana Lucia Demarcoa, Eduardo Donadib,

6 Ana Paula Fernandesc'*

7 a Department of Ophthalmology, Otorhinolaringology and Head and Neck Surgery, School of Medicine ofRibeiräo Preto, University of Säo

8 Paulo, 3900 Av Bandeirantes, CEP14 049-900, Ribeiräo Preto, SP, Brazil

9 b Department of Medical Clinical, School of Medicine ofRibeiräo Preto, University of Säo Paulo, 3900 Av Bandeirantes, CEP14 049-900,

10 Ribeiräo Preto, SP, Brazil

11 c Department of General and Specialized Nursing, Nursing School ofRibeiräo Preto, University of Säo Paulo, 3900 Av Bandeirantes,

12 CEP14 040-902, Ribeiräo Preto, SP, Brazil

article info


i6Q2 Article history:

Received 3 June 2015 Accepted 25 October 2015 Available online xxx


22Q3 HLA

23 HIV


25 Encephalitis

Toxoplasmic T. gondii

Background/aims: The frequency of HLA antigens/alleles associated with rapid progression from HIV infection to AIDS was evaluated in Brazilian AIDS patients with or without toxoplasmic encephalitis (TE).

Methods: 114 AIDS patients (41 with TE, 43 with anti-Toxoplasma gondii antibodies without TE, and 30 without anti-T. gondii and TE) were studied.

Results:HLA antigens/alleles associated with rapid progression to AIDS, particularly HLA-B35 antigens and HLA-DQB*01 allele group were significantly less represented in TE AIDS patients.

Conclusion:The presence of these HLA antigens/alleles that predisposed to AIDS progression was associated with resistance to TE among HIV-1 patients.

© 2016 Published by Elsevier Editora Ltda.


Human leukocyte antigens (HLA) genes have been reported to be associated with increased susceptibility to the development of specific disease or with progression to AIDS outcomes.1-3 The progression from human immunodeficiency

virus (HIV) infection to AIDS has been strongly associated with HLA-A1-Cw7-B8-DR3-DQ2 and HLA-A11-Cw4-B35-DR1-DQ1 haplotypes, conferring a high risk of rapid progression to AIDS.4-7 It has been assumed that associations between progression to AIDS and particular HLA alleles reflect differential antigen presentation by classes I or II molecules exhibiting particular motifs in the peptide binding groove.8

* Corresponding author at: Department of General and Specialized Nursing, School of Nursing of Ribeiräo Preto, University of Säo Paulo, 3900 Av. Bandeirantes, Monte Alegre, 14 049-902, Ribeiräo Preto, SP, Brazil.

E-mail address (A.P. Fernandes). 1413-8670/© 2016 Published by Elsevier Editora Ltda.

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For example, the most harmful effects of HLA-B*35 are seen with the molecules encoded by the HLA-B*35:02 and B*35:03 alleles, which have proline at anchor position 2 of their loaded peptide and a non-tyrosine residue at position 9.9 For instance, the HLA-B*35:01 molecule containing tyrosine at position 9 does not have any substantial effect on disease prognosis. While both HLA-B*35 subtypes can equally induce a cytotoxic T lymphocyte (CTL) response, viral load was cleared less effectively by non-tyrosine-containing HLA-B*35:02 and B*35:03 molecules compared with HLA-B*35:01.10 It may, therefore, be possible that altered epitope recognition by HLA-B*35:02 and B*35:03 will induce CTL that may not specifically function against HIV-1-infected cells.11

Toxoplasma gondii infection is widespread in humans, with estimated infection rates ranging from 50% to 80% of the general population in South America.12 In some areas of Southern Brazil, the prevalence of antibodies against T. gondii may be as high as 98%.13,14 Toxoplasmosis in the immunocompromised host is most probably due to reactivation of a previous latent infection and can be life-threatening.15 Encephalitis is the most important manifestation of toxoplasmosis in immuno-suppressed patients as it causes severe damage and death.16 It is estimated that in countries with a high prevalence of T. gondii, toxoplasmic encephalitis is the most common cerebral lesion in HIV patients.17

Few studies reported an association between HLA markers and toxoplasmic encephalitis in AIDS patients.18-21 We have previously reported that susceptibility to toxoplasmic retinochoroiditis was associated with HLA alleles related with rapid progression to AIDS,22 and the availability of genetic markers for other AIDS severe complications may discriminate patients with poor prognosis. To further explore whether HLA markers associated with rapid progression to AIDS could also be associated with the development of toxoplasmic encephalitis, we evaluated these markers in Brazilian AIDS patients with or without toxoplasmic encephalitis.

Material and methods


The study was conducted on 114 adult HIV-infected patients (81 males) aged 21-59 years (median = 33) presenting AIDS, diagnosed 1-108 months (median = 22) before inclusion in this study. Forty-one patients experienced toxoplasmic encephalitis, diagnosed clinically and by brain computerized tomography and by the presence of antibody against T. gondii (Group 1). Two additional AIDS patient groups without toxoplasmic encephalitis were studied; i.e., a group of 43 patients with positive anti-T gondii antibodies but without toxoplasmic encephalitis (Group 2), and 30 patients with neither anti-T. gondii antibodies nor toxoplasmic encephalitis (Group 3). Patients were selected from the Acquired Immunodeficiency Outpatient Clinic at the University Hospital of the Faculty of Medicine of Ribeirao Preto, University of Sao Paulo, Brazil. A total of 161 healthy bone marrow donors from the University Hospital of Faculty of Medicine of Ribeirao Preto with no known infectious, chronic, or autoimmune disorders were also studied.

Ethical aspects

The local Ethics Committee of the University Hospital of Faculty of Medicine of Ribeirao Preto and the National Brazilian Ethics Committee approved the study protocol, and informed consent was obtained from all individuals (HCFMRP-USP # 8992/2001 and CONEP # 203/2002).

Anti-T. gondii antibodies

The search for anti-T. gondii antibodies in serum was performed by indirect immunofluorescence by the method of Camargo23 using an anti-human IgG fluorescent conjugate (Bio-Merieux). Serum samples with >1/16 titers were considered to be positive.

HLA typing

HLA class I antigens expressed on the surface of peripheral blood lymphomononuclear cells were typed using a microlym-phocytotoxity assay.24 DNA was obtained from peripheral blood mononuclear cells using a salting out procedure. HLA class II allele typing was performed using commercial kits (One Lambda, Canoga Park, CA), as previously described.25

HLA specificities associated with the rate of progression to AIDS

Since HLA-A1, A11, B8, B35, DR3, DR1, DQ2, DQ1 antigens have been described in the literature in association with rapid progression to AIDS4,26 in many ethnic groups, these markers were considered for analysis in the present study.

Statistical analysis

HLA antigen and HLA allele group frequencies were calculated by direct counting. The strength of the association between toxoplasmic encephalitis and HLA specificities was evaluated calculating the relative risk (RR) and Odds Ratio (OR). The Fisher's exact test was used for comparisons, and it was considered to be significant at p < 0.05.


HLA profile according to the presence of toxoplasmic encephalitis

The frequency of HLA-B35 antigen was significantly decreased among AIDS patients presenting toxoplasmic encephalitis (Group 1) in comparison to AIDS patients with neither anti-T. gondii antibodies nor toxoplasmic encephalitis (Group 3) (p = 0.0007), presenting a RR = 0.20 and an 0D = 0.12 (Table 1). Similar results were observed when the group of toxoplas-mic encephalitis AIDS patients (Group 1) were compared with healthy controls (p = 0.0003) and a RR = 0.20 and an 0D = 0.12 (Table 1). When the HLA-B35 antigen frequency was compared between AIDS patients without toxoplasmic encephalitis (Group 2 and Group 3) its frequency was significantly decreased among AIDS patients presenting with anti-T.

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Table 1 – Frequency of human leukocyte antigens (HLA) associated with rapid progression to AIDS in Brazilian AIDS patients presenting with: (i) toxoplasmic encephalitis (Group 1); (ii) antibody against T. gondii but without toxoplasmic encephalitis (Group 2); and (iii) negative serology for T. gondii and without toxoplasmic encephalitis (Group 3). The frequencies of HLA among healthy controls are also shown.

HLA Group 1 (n = 41) Group 2 (n = 43) Group 3 (n = 30) Healthy controls (n = 161) Group Comparisons (p-values)

1x 2 1 x 3 2 x 3

HLA-A11 HLA-B35 HLA-DR1 HLA-DQ1 4 (10%) 4 (10%) 5 (12%) 17 (42%) 2 (5%) 6 (14%) 10 (23%) 36 (84%) 2 (7%) 14 (47%) 3 (10%) 16 (53%) 19 (12%) 76 (47%) (p = 0.0003 x G1) 24 (15%) 140 (87%) (p = 0.0001 x G1) NS NS NS 0.0001 NS 0.0007 NS NS NS 0.0031 NS 0.008

NS, non-si gnificant comparisons: ; x G1, comparisons to Group 1.

139 gondii antibodies (Group 2) (p = 0.0031), with a RR = 0.29 and an

140 OD = 0.18 (Table 1). However, the comparison of the frequency

141 of HLA-B35 between patients with positive anti-T. gondii anti-

142 bodies, with and without toxoplasmic encephalitis (Group 1

143 and Group 2), showed no significant difference (Table 1).

144 On the other hand, the frequency of HLA-DQBV01 allele

145 group was significantly decreased among AIDS patient pre-

146 senting toxoplasmic encephalitis (Group 1) in comparison

147 to AIDS patient presenting anti-T. gondii antibodies but

148 without toxoplasmic encephalitis (Group 2) p = 0.0001), and

149 with a RR = 0.49 and an 0D = 0.13 (Table 1). Similar results

150 were observed when the AIDS group with toxoplasmic

151 encephalitis (Group 1) were compared with healthy con-

152 trols (p = 0.0001), with a RR = 0.47 and an 0D = 0.10 (Table 1).

153 When the HLA-DQB1*01 allele group frequency was compared

154 between AIDS patients without toxoplasmic encephalitis

155 (Group 2 and Group 3) its frequency was significantly

156 decreased among those without anti-T. gondii antibodies

157 (Group 3) (p = 0.008), conferring a RR=1.57 and an 0D = 4.50

158 (Table 1).

159 The frequencies of other HLA markers associated with

160 rapid progression to AIDS were closely similar among AIDS

161 patients and healthy controls.


162 Several reports examining the role of HLA antigens/alleles in

163 AIDS susceptibility have been published5 and the haplotypes

164 encompassing HLA-B35 antigens were consistently associated

165 with rapid progression to AIDS in several populations.27 HLA-

166 B*35 alleles have been classified into two groups based on the

167 residue at pocket 9 (P9) of the peptide binding groove. The PY

168 group binds mainly to a tyrosine (Y) at P9, whereas the Px

169 group has a preference for smaller hydrophobic residues such

170 as leucine, methionine, or valine, and does not bind to tyrosine

171 at P9.9 HLA-B*35:02 and B*35:03 alleles, which code part of the

172 Px group, have been associated with an especially poor HIV

173 disease outcome.10 The possible mechanisms for this asso-

174 ciation remain unknown, but it has been suggested that the

175 greater ability of the HLA-B*35:01 (PY) molecule to present HIV

176 peptides (Gag) compared to HLA-B*35:02/35:03 molecules is a

177 key difference affecting HIV disease outcome.28 Furthermore,

HLA-B35:16 another member of the PY group, was the worst 178

HIV-peptide binding molecule among all B35 subtypes and was 179

associated with the highest viral load. Therefore, the detri- 180

mental effect of HLA-B35 is unlikely to be related exclusively 181

to PY/Px groups. Other factors, such as the fine specificity of 182

the HIV peptides presented by different B35 molecules, may 183

play a role, affecting the nature of the CTL response.29 184

Few studies have focused on the evaluation of HLA anti- 185

gens/alleles in toxoplasmic infection among AIDS patients. 186

Concerning cerebral toxoplasmosis, the study conducted in 187

Caucasian North American patients with AIDS have reported 188

an association of the HLA-DQ3 antigen with susceptibil- 189

ity, and HLA-DQ1 antigen with resistance to toxoplasmic 190

encephalitis.19,20 In the present study, we found a similar 191

association; i.e., HLA-DQ1 conferring resistance to toxoplas- 192

mic encephalitis in Brazilian AIDS patients. Additionally, Mack 193

et al. studying transgenic mice for DQ human genes, demon- 194

strated that the human DQB1 gene, and to a lesser extent DQ3 195

gene, confers protection against T. gondii, corroborating the 196

idea that certain DQB1 genes are associated with protection 197

against this pathogenic protozoan. 198

This is the first study evaluating the frequency of HLA 199

markers in Brazilian AIDS patients, a mixed population, 200

presenting with cerebral toxoplasmic disease. The findings 201

suggest that the frequency of HLA markers associated with 202

rapid progression to AIDS, in particular the HLA-DQB1*01 allele 203

group and HLA-B35 antigen, were less represented among tox- 204

oplasmic encephalitis AIDS patients. The frequency of T. gondii 205

infection in Brazilian AIDS patients can be as high as 98%.13 206

Therefore, the presence of these HLA markers may confer 207

resistance to the development of toxoplasmic encephalitis, 208

which are different from those markers associated with rapid 209

progression to AIDS. 210

In conclusion, AIDS patients presenting HLA-DQBl*01 allele 211

group appear to be resistant to the development of toxoplas- 212

mic encephalitis, since the frequency of this allele was lower 213

in AIDS patients presenting encephalitis in relation to AIDS 214

patients presenting only the infection (anti-T. gondii antibod- 215

ies). The present study suggests that HLA-DQB1 typing, better 216

than the HLA-B, may help on decisions regarding toxoplasmo- 217

sis prophylaxis. Further studies will be required to determine 218

if genetic control of susceptibility to toxoplasmic encephalitis 219

is similar in AIDS patients of other ethnicities. 220


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Conflicts of interest

221 The authors declare no conflicts of interest.


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