Nasal-associated lymphoid tissue is a site of long-term virus-specific antibody production following respiratory virus infection of mice

Abstract

Nasal immunoglobulin A provides an initial defense against inhaled respiratory pathogens. However, it is not known whether the nasal-associated lymphoid tissues (NALT) are able to mount an effective long-lasting pathogen-specific immune response, nor is it known whether functional differences exist between the organized NALT (O-NALT) and the diffuse NALT lining the nasal passages (D-NALT). Here we show that although both the O-NALT and the D-NALT are capable of producing virus-specific antibody in response to influenza virus infection, the frequency of specific antibody-forming cells in the D-NALT is much greater than the frequency observed in the O-NALT. Furthermore, we show that the D-NALT but not the O-NALT is the site of long-term virus-specific humoral immunity which lasts for the life of the animal. These results indicate that the D-NALT is not only the major effector site of the NALT but also the site of local long-term specific antibody production.

FIG. 1

Virus-specific antibody responses in the D-NALT are maintained for at least 18 months after primary intranasal infection with influenza virus. Mice were sacrificed at certain time points postinfection, and virus-specific AFCs in the cervical lymph nodes (A), O-NALT (B), and D-NALT (C) were enumerated by the ELISPOT assay. Cells were pooled from four or five mice per time point. Each panel is representative of one experimental time course. Each time course was carried out three times independently with similar results. D, day; M, months.

FIG. 2

Virus-specific AFC frequencies in the lung (A) and bone marrow (B) after primary intranasal infection with influenza virus. Mice were sacrificed at certain time points postinfection, and virus-specific AFCs in the lung and bone marrow were enumerated by the ELISPOT assay. Cells were pooled from four or five mice per time point. Each panel is representative of one experimental time course. Each time course was carried out three times independently with similar results. D, day; M, months.

FIG. 3

Influenza virus is cleared later in the D-NALT than in the O-NALT or the lung. Influenza virus titers were determined by inoculation into the allantoic fluid cavities of 10-day-old embryonated hen eggs. HA activity was assayed 72 h later. Assays were performed in triplicate with three mice per time point, and results are the means and standard deviations from three independent experiments. EID₅₀, 50% egg infective dose; D, day.