Cerebrospinal fluid anti-cerebellar soluble lectin antibodies in human immunodeficiency virus type 1 infection

Persistent central nervous system immune activation following more than 10 years of effective HIV antiretroviral treatment

OBJECTIVE

Low-grade immune activation is common in people living with HIV (PLHIV), despite long-term viral suppression by antiretroviral therapy (ART). The clinical significance of this activation remains unclear. The aim of this study was to examine residual intrathecal immune activation in relation to signs of neuronal injury and neurocognitive impairment in PLHIV who had been virally suppressed on ART for more than 10 years.

DESIGN/METHODS

Twenty neuroasymptomatic PLHIV on suppressive ART for a median of 13.2 years were retrospectively identified from the longitudinal prospective Gothenburg HIV cerebrospinal fluid (CSF) study. HIV-RNA, neopterin, and neurofilament light protein (NFL) levels were measured in paired plasma and CSF samples. Pretreatment samples were available for 14 patients. Cognitive function was assessed by CogState at follow-up.

RESULTS

CSF neopterin decreased from a median (IQR) of 17.8 (10.6-29.7) to 6.1 (4.6-8.0) nmol/l during treatment (P < 0.001). In 11 out of 20 participants (55%), CSF neopterin levels were above the upper normal reference limit (5.8 nmol/l) at follow-up. Age-adjusted CSF NFL decreased to within-normal levels from a median of (IQR) 1179 (557-2707) to 415 (292-610) ng/l (P < 0.001). No significant correlations were found between CSF neopterin and CSF NFL or neurocognitive performance.

CONCLUSION

Although CSF neopterin decreased significantly, more than 50% of the patients had CSF concentrations above the upper normal reference value despite more than 10 years of suppressive ART. We found no correlation between CSF neopterin, CSF NFL or neurocognitive performance at follow-up, indicating that low-grade immune activation during suppressive ART may be clinically benign.

Extensive viral mimicry of 22 AIDS-related autoantigens by HIV-1 proteins and pathway analysis of 561 viral/human homologues suggest an initial treatable autoimmune component of AIDS

HIV-1 viral proteins, particularly the env protein, are homologous to 22 AIDS autoantigens, suggesting their creation by antiviral antibodies subsequently targeting human homologues. They include antibodies to T-cell receptors, CD4 and CD95, complement components, IgG, TNF and other immune-related proteins. Autoantibodies may compromise the immune system via knockdown of these key proteins, and autoimmune attack on the immune system itself, as supported by immune activation in early stages of infection and during the transition to AIDS. Over 500 human proteins contain pentapeptides or longer consensi, identical to viral peptides. Such homology explains the extensive viral/human interactome, likely related to the ability of viral homologues to compete with human counterparts as binding partners. Pathway analysis of these homologous proteins revealed their involvement in immune-related networks (e.g. natural killer cell toxicity/toll, T-cell/B-cell receptor signalling/antigen processing) and viral and bacterial entry and defence pathways (phagosome/lysosome pathways, DNA sensing/NOD/RIG-1 pathways) relevant to AIDS pathogenesis. At its inception, AIDS may have an autoimmune component selectively targeting the immune system. Immunosuppressive therapy or antibody removal, which has already achieved some success, might be therapeutically beneficial, particularly if targeted at removal of the culpable antibodies, via affinity dialysis.

Effects of antiretroviral treatment on blood-brain barrier integrity and intrathecal immunoglobulin production in neuroasymptomatic HIV-1-infected patients

OBJECTIVES

To study the effect of antiretroviral combination therapy on blood-brain barrier (BBB) integrity and intrathecal immunoglobulin G (IgG) production.

METHODS

Lumbar punctures were performed on 38 neurologically asymptomatic, treatment-naive HIV-1-infected patients prior to and during treatment at intervals of approximately 4 months, 1 year and 2 years. Albumin ratio and IgG index were analysed as markers of BBB integrity and intrathecal IgG synthesis.

RESULTS

HIV-1 RNA decreased to < 50 HIV-1 RNA copies/mL in the cerebrospinal fluid (CSF) of all patients and in the plasma of all but one patient. Only 5% of patients had elevated albumin ratio values at baseline, while 56% had an elevated IgG index. There was no significant reduction of the albumin ratio or the IgG index. After 2 years of treatment all patients had normal albumin ratio values, while 41% still had increased IgG index levels.

CONCLUSIONS

Up to 2 years after the initiation of treatment, the favourable impact of antiretroviral combination treatment on CSF viral load was not accompanied by a similar reduction of intrathecal IgG production. BBB function, measured as the albumin ratio, was not significantly changed in this cohort of neurologically asymptomatic HIV-1-infected patients.

High levels in serum, but no signs of intrathecal synthesis of anti-sulfatide antibodies in HIV-1 infected individuals with or without central nervous system complications

Myelin degeneration is commonly found in the central nervous system (CNS) of individuals infected with human immunodeficiency virus type 1 (HIV-1), especially in patients with HIV-1-associated dementia. We analysed cerebrospinal fluid (CSF) and serum samples from 25 HIV-1 infected individuals for the presence of antibodies directed against sulfatide, the major acidic glycosphingolipid in myelin. Nine of the patients had CNS complications, including 3 with HIV-1-associated dementia, and 16 had no neurological symptoms. Elevated titres of anti-sulfatide antibodies were found in serum from 24/25 HIV-1-infected individuals but in none of them in the CSF. Although the vast majority of HIV-1-infected individuals harbour autoantibodies directed against sulfatide in serum, the lack of detectable intrathecal production indicates that anti-sulfatide antibodies are not a major component in the pathogenesis of CNS myelin damage in HIV-1 infection.

Intrathecal synthesis of anti-sulfatide IgG is associated with peripheral nerve disease in acquired immunodeficiency syndrome

Peripheral nervous system involvement in the acquired immunodeficiency syndrome (AIDS) can take the form of an acute or chronic inflammatory demyelinating polyneuropathy, polyradiculopathy, mononeuropathy multiplex, or autonomic neuropathy. There is no widely held consensus on the etiology of PNS or other neurological complications associated with HIV infection. We report here that PNS disease in HIV-infected individuals is associated with intrathecal synthesis of an antibody directed against sulfatide, a major component of myelin. The anti-sulfatide antibody is also present nonspecifically in serum. The antibody requires the presence of the 3-O-sulfogalactosyl residue for binding and recognizes preferentially the hydroxy fatty acid-containing form of sulfatide. Anti-sulfatide antibodies are therefore one of the humoral factors responsible for demyelinating diseases in AIDS patients.

Intrathecal synthesis of anti-myelin basic protein IgG in HIV-1+ patients

Human immunodeficiency virus type 1 (HIV-1)-infected individuals frequently develop a broad spectrum of neurological syndromes, classified as HIV-1-associated cognitive/motor complex. Diffuse demyelination of hemispheric white matter is a commonly observed in HIV-1 infected brain, but the events leading to myelin destruction are still obscure. Since oligodendrocyte infection by HIV-1 is not proven as yet, myelin damage in HIV-1 infection may result from indirect mechanisms such as the excessive release of myelinotoxic substances or the triggering of autoimmune responses directed to myelin constituents. To verify the latter hypothesis, we searched for elevated anti-myelin basic protein (MBP) IgG levels in the cerebrospinal fluid (CSF) and serum of 25 patients with HIV-1 infection, 12 with multiple sclerosis (MS), and 9 with non-inflammatory neurological diseases (NIND). CSF, but not serum, anti-MBP IgG levels were more frequently elevated in HIV-1+ (16/25, 64%) than in MS (3/12, 25%) or NIND (0/9) patients. By using the anti-MBP IgG index, the anti-MBP IgG antibody specificity index (ASI), and the search for anti-MBP oligoclonal IgG, we ascertained that anti-MBP IgG were produced within the CNS in 13 of 25 (52%) HIV-1+, in 6 of 12 (50%) MS, and in none of NIND patients. The incidence of increased CSF anti-MBP IgG levels was higher among HIV-1+ patients at stage II-III (4/4, 100%) or at stage IV B (7/9, 78%) than among those at stage IV C-IV D (5/12, 42%). Although our data indicate that intrathecal anti-MBP IgG may occur early during HIV-1 infection and that they are more common in patients with HIV-1-associated cognitive/motor complex, the possible demyelinating role of these antibodies remains to be demonstrated.

Tryptophan concentrations increase in cerebrospinal fluid and blood after zidovudine treatment in patients with HIV type 1 infection

Cerebrospinal fluid (CSF) and blood concentrations of indoleamines and catecholamines were analyzed in 14 HIV-1-seropositive individuals before antiviral treatment with zidovudine, after 3-14 months of treatment, and, in 8 of the patients, also after 14-30 months. The median pretreatment concentrations of tryptophan in CSF and blood were low (224 ng/ml and 6.0 micrograms/ml, respectively), but an increase in these values by an average of 40% in CSF and 23% in blood was seen after 3-14 months of zidovudine treatment (p < 0.01) and remained undiminished after 14-30 months of treatment. No significant change was observed in the 5-hydroxytryptamine (5-HT, serotonin) level in blood or in the CSF concentrations of the 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA) and the dopamine metabolite homovanillic acid (HVA). The CSF concentrations of the noradrenalin metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) had decreased by 12% on average (p < 0.01) by the time of the second follow-up, that is, after 14-30 months of zidovudine treatment. A decrease in neopterin during antiretroviral treatment correlated with an increase in tryptophan (p < 0.01). The data suggest that an association between decreased immune stimulation and reduced tryptophan degradation in patients treated with zidovudine.

Presence of anti-CSL antibodies in the cerebrospinal fluid of patients: a sensitive and specific test in the diagnosis of multiple sclerosis

The carbohydrate-binding protein (lectin) CSL is an antigen involved in the stabilization of the myelin structure by interacting with the carbohydrate moiety of myelin glycoproteins. Since anti-CSL Fab fragments were able to produce destruction of CNS myelin in vitro, CSL was considered as a potential immunological target in multiple sclerosis. The presence of anti-CSL antibodies has been examined in the cerebrospinal fluid of 1388 different patients with various neurological diseases. It is concluded that the presence of anti-CSL antibodies in the cerebrospinal fluid of patients less than 50 years old constitutes a very sensitive and specific test for multiple sclerosis.