A35R and H3L are Serological and B Cell Markers for Monkeypox Infection

Abstract

Monkeypox virus (MPXV) resides in two forms, mature and enveloped virions, and depending on it, distinct proteins are displayed on the viral surface. We expressed in mammalian cells two MPXV antigens from the mature form and two MPXV antigens from the enveloped form and tested their reactivity to sera of 11 MPXV convalescent donors diagnosed in Israel during May-June 2022 and collected 33-62 days post infection. While only 4 out of 11 donors neutralized the related Vaccinia Lister strain, all MPXV recoverees demonstrated a strong serological response to a 124-amino acid truncation of the A35R antigen, and to a 276-amino acid truncation of the H3L antigen. Moreover, A35R- and H3L-specific B cells ranging from 0.03-0.5% and 0.01-0.35% of IgG+CD19+ cells, respectively, were detected in all 11 MPXV donors (A35R), and in 8 out of 11 donors (H3L). Therefore, A35R and H3L represent MPXV immune targets, and can be used in a simple heat-inactivated serological enzyme-linked immunosorbent assay for the identification of recent MPXV infection.

Mpox vaccine and infection-driven human immune signatures

“…We found a positive correlation between JYNNEOS-elicited antibodies against the A35R and A33R proteins, suggesting that the common sequences these orthologs share induce comparable antibody responses to the vaccine. Finally, we confirmed the A35R protein as a serum marker of human mpox virus infection 40 , given the total absence of AS35R-IgG in the serum after vaccination.…”

“…We found a positive correlation between JYNNEOS-elicited antibodies against the A35R and A33R proteins, suggesting that the common sequences these orthologs share induce comparable antibody responses to the vaccine. Finally, we confirmed the A35R protein as a serum marker of human mpox virus infection 40 , given the total absence of AS35R-IgG in the serum after vaccination. Our data establish that the B cell immunogenicity of JYNNEOS vaccination is low up to 2 months post-vaccination.Thus, what mediates JYNNEOS' protective effects in humans if not B cells and antibodies?…”

“…We quantified serum IgG responses after immunization or infection. Initially, we expressed the mpox proteins A29L, A35R, A30L and E8L (strain Zaire-96-I-16), all known antibody targets 38 that can induce B cell immunogenicity [39][40][41][42][43][44] . IgG responses to A29L and A35R proteins were increased only after infection (Figure 3A-D) and were undetectable or present at very low levels in the serum of vaccinees shortly after or up to 60 days after the first or second doses (Figure S8).…”

“…A recent ELISA-based study reported vaccine-specific IgG peaks in the serum of JYNNEOS-vaccinated participants after 42 days 66 . In addition, a recent study reported lower A35R- and H3L-specific titers in antigen-specific IgG tests compared to tests against the whole sera of convalescent participants, suggesting that IgMs might be among the immunoglobulins responding up to 50 days post-viral exposure (in that case, via infection) 40 . The reference strains of VACV and mpox virus share > 90% identity.…”

“…OPXV-elicited antibodies have significantly better cross-neutralizing potential compared to those targeting other viruses, such as HIV and influenza virus 26 , due to the a) high sequence homology between the surface proteins of VACV, mpox virus, smallpox virus, and cowpox virus (89-100% similarity) and b) the broad neutralization effects of OPXV antibodies, which can target multiple viral surface proteins concomitantly [62][63][64] 66 . In addition, a recent study reported lower A35R-and H3L-specific titers in antigen-specific IgG tests compared to tests against the whole sera of convalescent participants, suggesting that IgMs might be among the immunoglobulins responding up to 50 days post-viral exposure (in that case, via infection) 40 . The reference strains of VACV and mpox virus share > 90% identity.…”