Neutralization of human immunodeficiency virus type 1 (HIV-1) mediated by parotid IgA of HIV-1-infected patients

Infection with human immunodeficiency virus type 1 (HIV-1) has been shown to elicit a serum antibody response with neutralizing activity against T cell line-adapted HIV strains and primary HIV-1 isolates. Mucosal surfaces are the primary route of HIV-1 infection. Evidence is presented here for the presence of HIV-neutralizing antibodies in secretions. Infection of mucosal cells with HIV stimulates systemic and mucosal immune responses and results in the generation of neutralizing antibodies. Serum IgG and IgA neutralize HIV-1MN infection of susceptible T cell lines; serum IgG inhibits more effectively. Mucosal IgA purified from parotid saliva of HIV-1-seropositive individuals could neutralize both a T cell line-adapted strain and a primary isolate. The neutralizing activity of IgA was not directed against the anti-third-variable-loop or the anti-ELDKWA epitope. Thus, the specificity of mucosal IgA for HIV-1 neutralization epitopes remains to be determined and may provide insight into development of a mucosal vaccine.

Maternal humoral factors associated with perinatal human immunodeficiency virus type-1 transmission in a cohort from Kigali, Rwanda, 1988-1994

OBJECTIVES

to study different parameters of humoral immunity responses in the serum of 39 human immunodeficiency virus type-1 infected pregnant women from Kigali, (Rwanda) in correlation with perinatal transmission.

METHODS

this study was done between 1988 and 1994. Thirty nine HIV-1 infected women, 18 transmitting (T) and 21 non-transmitting (NT) mothers, have been chosen based on the quantity of sera available for analysis. Maternal data were collected at the time of delivery or during the preceding month. Quantification of viral load was performed by the signal amplification bDNA assay. Specific reactivity of antibody was tested against recombinant p24 protein and five different synthetic peptides from gp120 and gp41 based on HIV LAI-strain sequences. Neutralization assays were performed against laboratory (RII strain of the HIV-1 C subtype) and primary strains (two NSI and one SI of the HIV-1 A subtype). Antibody Dependent Cellular Cytotoxicity assay was performed with CEM.NK(R) cells against a laboratory HIV-1 strain.

RESULTS

absence of correlation regarding maternal viral load, or viral subtype and vertical transmission was observed. By contrast, the CD4/CD8 ratio was significantly higher in non-transmitting mothers compared to transmitting mothers. Moreover, high anti-p24 antibody avidity was correlated with a lower risk of perinatal transmission. Furthermore, transmission risk appeared significantly higher with reactivity of serum samples to linear epitopes of gp41 (amino acids 566-582, 578-594), whereas risk appeared lower with reactivity to the immunodominant domain of gp41 (amino acids 597-609). No significant difference was observed in titres of antibody neutralizing primary isolates (two NSI (non syncitium inducer) and one SI (syncitium inducer) of the HIV-1 A subtype) and laboratory strain (RII strain, of the HIV-1 C subtype) between transmitting and non-transmitting mother's sera. In addition, titres of Antibody Dependent Cellular Cytotoxicity were similar in transmitting versus non-transmitting mothers. However, high Antibody Dependent Cellular Cytotoxicity titres were correlated with a good clinical status of children.

CONCLUSIONS

three parameters such as high CD4/CD8 ratio, high anti-p24 antibody avidity and high reactivity against the immunodominant epitope of gp41 have been shown to be correlated with no perinatal transmission. High Antibody Dependent Cellular Cytotoxicity titres appeared to be linked to a good clinical status of children after birth. One parameter, reactivity against two linear epitopes of gp41, appeared to be correlated with vertical transmission.

Identification of three major phosphorylation sites within HIV-1 capsid. Role of phosphorylation during the early steps of infection

We previously reported the presence of two cellular serine/threonine protein kinases incorporated in human immunodeficiency virus type 1 (HIV-1) particles. One protein kinase is MAPK ERK2 (mitogen-activated protein kinase), whereas the other one, a 53-kDa protein, still needs to be identified. Furthermore, we demonstrated that the capsid protein CAp24 is phosphorylated by one of those two virion-associated protein kinases (Cartier, C., Deckert, M., Grangeasse, C., Trauger, R., Jensen, F., Bernard, A., Cozzone, A., Desgranges, C., and Boyer, V. (1997) J. Virol. 71, 4832-4837). In this study, we showed that CAp24 is not a direct substrate of MAPK ERK2. Moreover, using site-directed mutagenesis of each of the 9 serine residues of CAp24, we demonstrated the phosphorylation of 3 serine residues (Ser-109, Ser-149, and Ser-178) in the CAp24. Substitution of each serine residue did not affect viral budding, nor viral structure. By contrast, substitution of Ser-109, Ser-149, or Ser-178 affects viral infectivity by preventing the reverse transcription process to be completely achieved. Our results suggest that CAp24 serine phosphorylation is essential for viral uncoating process.