Heterosubtypic Immunity to Influenza A Virus Infection Requires a Properly Diversified Antibody Repertoire

Abstract

Heterosubtypic immunity (HSI) is defined as cross-protection to infection with an influenza A virus serotype other than the one used for primary infection. Although HSI has been thought to be mediated by serotype cross-reactive cytotoxic T lymphocytes (CTL) that recognize conserved epitopes of structural proteins, recent studies suggest that antibodies (Abs) may make a significant contribution. In this study, we provide further evidence for the role of Abs in HSI using transgenic mice lacking terminal deoxyribonucleotidyltransferase (TdT), which adds N nucleotides to V-D and D-J junctions of the complementary determining region 3 (CDR3) (TdT ؊/؊ ) and mice with altered Ab repertoires due to replacement of the complete locus of heavy chain diversity segments (D H ) with an altered D H segment (namely, ⌬D-iD). Both types of mice failed to generate complete HSI, although they were able to mount protective immunity to a homologous challenge. Lower levels of virus-specific antibodies along with more severely impaired HSI were observed in TdT ؊/؊ mice compared to those in ⌬D-iD mice, while CTL activity remained unchanged in both types of mice. These findings indicate that a properly diversified antibody repertoire is required for HSI and that N addition by TdT is a more effective mechanism in the induction of a properly diversified antibody repertoire and, therefore, complete HSI. The results suggest that the diversity of the antibody repertoire as determined by the composition of the D region of HCDR3 and by N addition are among the mechanisms selected for in evolution to create a favorable environment to resolve infections with mutated viruses.

Regulation of Antinucleoprotein IgG by Systemic Vaccination and Its Effect on Influenza Virus Clearance

“…The search for universal influenza vaccines has focused on exploiting the mechanisms of Het-I, which has been studied extensively in mice (13,25,26,33,(38)(39)(40)52). There is evidence for Het-I in humans as well, defined as reductions in hospitalization and in mortality (30,31,34,35,44) and by a lower infection rate (11).…”

“…Thus, unlike inactivated virus vaccines, NP immunization provides cross-protection similar to that induced by prior influenza virus infection (heterosubtypic immunity [Het-I]) (12,14,17,27,53,54,57). Importantly, Het-I is poor in B cell-deficient mice (39) and in mice with limited antibody diversity (33), suggesting that antibody responses to conserved Ags, such as NP, make a major contribution to Het-I. In fact, accelerated viral clearance induced by NP protein immunization requires antibody production (3).…”

“…In fact, accelerated viral clearance induced by NP protein immunization requires antibody production (3). Despite the importance of antibody for Het-I and for NPimmune protection in mice (3,33), the presence of NP-reactive IgG in potentially susceptible individuals has raised concern about the utility of these antibodies in humans (10,47,58). However, such observations do not exclude the possibility that NP-immune antibody or NP-immune memory T cells (each of which is induced by prior infection and could be enhanced with proper boosting) can or do provide antiviral immunity.…”

Vaccination with whole inactivated virus vaccine affects the induction of heterosubtypic immunity against influenza virus A/H5N1 and immunodominance of virus-specific CD8+ T-cell responses in mice

“…Vaccination and heterosubtypic immunity to influenza induced by infection, such as virus-specific CD4 + T cells, antibodies to the extracellular domain of the matrix protein (Benton et al, 2001;Jegerlehner et al, 2004;Liang et al, 1994;Neirynck et al, 1999;Nguyen et al, 1999Nguyen et al, , 2000Nguyen et al, , 2001Nguyen et al, , 2007Rangel-Moreno et al, 2008;Slepushkin et al, 1995;Straight et al, 2008) and the induction of tertiary lymphoid structures (Moyron-Quiroz et al, 2004). Although it has been suggested recently that antibodies to the NP also contribute to heterosubtypic immunity (Carragher et al, 2008), it is unlikely that they played a role in the present study, as all vaccinated mice developed NP-specific antibodies, which did not correlate with protection against H5N1 infection (data not shown).…”

“…+ and CD8 + T cells, local virus-specific antibodies and B cells (Benton et al, 2001;Grebe et al, 2008;Neirynck et al, 1999;Nguyen et al, 1999Nguyen et al, , 2007Slepushkin et al, 1995;Tumpey et al, 2001). …”